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Linux/kernel/sched/fair.c

  1 /*
  2  * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
  3  *
  4  *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  5  *
  6  *  Interactivity improvements by Mike Galbraith
  7  *  (C) 2007 Mike Galbraith <efault@gmx.de>
  8  *
  9  *  Various enhancements by Dmitry Adamushko.
 10  *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 11  *
 12  *  Group scheduling enhancements by Srivatsa Vaddagiri
 13  *  Copyright IBM Corporation, 2007
 14  *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 15  *
 16  *  Scaled math optimizations by Thomas Gleixner
 17  *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
 18  *
 19  *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 20  *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
 21  */
 22 
 23 #include <linux/latencytop.h>
 24 #include <linux/sched.h>
 25 #include <linux/cpumask.h>
 26 #include <linux/cpuidle.h>
 27 #include <linux/slab.h>
 28 #include <linux/profile.h>
 29 #include <linux/interrupt.h>
 30 #include <linux/mempolicy.h>
 31 #include <linux/migrate.h>
 32 #include <linux/task_work.h>
 33 
 34 #include <trace/events/sched.h>
 35 
 36 #include "sched.h"
 37 
 38 /*
 39  * Targeted preemption latency for CPU-bound tasks:
 40  * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
 41  *
 42  * NOTE: this latency value is not the same as the concept of
 43  * 'timeslice length' - timeslices in CFS are of variable length
 44  * and have no persistent notion like in traditional, time-slice
 45  * based scheduling concepts.
 46  *
 47  * (to see the precise effective timeslice length of your workload,
 48  *  run vmstat and monitor the context-switches (cs) field)
 49  */
 50 unsigned int sysctl_sched_latency = 6000000ULL;
 51 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
 52 
 53 /*
 54  * The initial- and re-scaling of tunables is configurable
 55  * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 56  *
 57  * Options are:
 58  * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 59  * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 60  * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 61  */
 62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
 63         = SCHED_TUNABLESCALING_LOG;
 64 
 65 /*
 66  * Minimal preemption granularity for CPU-bound tasks:
 67  * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
 68  */
 69 unsigned int sysctl_sched_min_granularity = 750000ULL;
 70 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
 71 
 72 /*
 73  * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 74  */
 75 static unsigned int sched_nr_latency = 8;
 76 
 77 /*
 78  * After fork, child runs first. If set to 0 (default) then
 79  * parent will (try to) run first.
 80  */
 81 unsigned int sysctl_sched_child_runs_first __read_mostly;
 82 
 83 /*
 84  * SCHED_OTHER wake-up granularity.
 85  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
 86  *
 87  * This option delays the preemption effects of decoupled workloads
 88  * and reduces their over-scheduling. Synchronous workloads will still
 89  * have immediate wakeup/sleep latencies.
 90  */
 91 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
 92 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
 93 
 94 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
 95 
 96 /*
 97  * The exponential sliding  window over which load is averaged for shares
 98  * distribution.
 99  * (default: 10msec)
100  */
101 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
102 
103 #ifdef CONFIG_CFS_BANDWIDTH
104 /*
105  * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106  * each time a cfs_rq requests quota.
107  *
108  * Note: in the case that the slice exceeds the runtime remaining (either due
109  * to consumption or the quota being specified to be smaller than the slice)
110  * we will always only issue the remaining available time.
111  *
112  * default: 5 msec, units: microseconds
113   */
114 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
115 #endif
116 
117 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
118 {
119         lw->weight += inc;
120         lw->inv_weight = 0;
121 }
122 
123 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
124 {
125         lw->weight -= dec;
126         lw->inv_weight = 0;
127 }
128 
129 static inline void update_load_set(struct load_weight *lw, unsigned long w)
130 {
131         lw->weight = w;
132         lw->inv_weight = 0;
133 }
134 
135 /*
136  * Increase the granularity value when there are more CPUs,
137  * because with more CPUs the 'effective latency' as visible
138  * to users decreases. But the relationship is not linear,
139  * so pick a second-best guess by going with the log2 of the
140  * number of CPUs.
141  *
142  * This idea comes from the SD scheduler of Con Kolivas:
143  */
144 static unsigned int get_update_sysctl_factor(void)
145 {
146         unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
147         unsigned int factor;
148 
149         switch (sysctl_sched_tunable_scaling) {
150         case SCHED_TUNABLESCALING_NONE:
151                 factor = 1;
152                 break;
153         case SCHED_TUNABLESCALING_LINEAR:
154                 factor = cpus;
155                 break;
156         case SCHED_TUNABLESCALING_LOG:
157         default:
158                 factor = 1 + ilog2(cpus);
159                 break;
160         }
161 
162         return factor;
163 }
164 
165 static void update_sysctl(void)
166 {
167         unsigned int factor = get_update_sysctl_factor();
168 
169 #define SET_SYSCTL(name) \
170         (sysctl_##name = (factor) * normalized_sysctl_##name)
171         SET_SYSCTL(sched_min_granularity);
172         SET_SYSCTL(sched_latency);
173         SET_SYSCTL(sched_wakeup_granularity);
174 #undef SET_SYSCTL
175 }
176 
177 void sched_init_granularity(void)
178 {
179         update_sysctl();
180 }
181 
182 #define WMULT_CONST     (~0U)
183 #define WMULT_SHIFT     32
184 
185 static void __update_inv_weight(struct load_weight *lw)
186 {
187         unsigned long w;
188 
189         if (likely(lw->inv_weight))
190                 return;
191 
192         w = scale_load_down(lw->weight);
193 
194         if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
195                 lw->inv_weight = 1;
196         else if (unlikely(!w))
197                 lw->inv_weight = WMULT_CONST;
198         else
199                 lw->inv_weight = WMULT_CONST / w;
200 }
201 
202 /*
203  * delta_exec * weight / lw.weight
204  *   OR
205  * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
206  *
207  * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
208  * we're guaranteed shift stays positive because inv_weight is guaranteed to
209  * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
210  *
211  * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212  * weight/lw.weight <= 1, and therefore our shift will also be positive.
213  */
214 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
215 {
216         u64 fact = scale_load_down(weight);
217         int shift = WMULT_SHIFT;
218 
219         __update_inv_weight(lw);
220 
221         if (unlikely(fact >> 32)) {
222                 while (fact >> 32) {
223                         fact >>= 1;
224                         shift--;
225                 }
226         }
227 
228         /* hint to use a 32x32->64 mul */
229         fact = (u64)(u32)fact * lw->inv_weight;
230 
231         while (fact >> 32) {
232                 fact >>= 1;
233                 shift--;
234         }
235 
236         return mul_u64_u32_shr(delta_exec, fact, shift);
237 }
238 
239 
240 const struct sched_class fair_sched_class;
241 
242 /**************************************************************
243  * CFS operations on generic schedulable entities:
244  */
245 
246 #ifdef CONFIG_FAIR_GROUP_SCHED
247 
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
250 {
251         return cfs_rq->rq;
252 }
253 
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se)      (!se->my_q)
256 
257 static inline struct task_struct *task_of(struct sched_entity *se)
258 {
259 #ifdef CONFIG_SCHED_DEBUG
260         WARN_ON_ONCE(!entity_is_task(se));
261 #endif
262         return container_of(se, struct task_struct, se);
263 }
264 
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267                 for (; se; se = se->parent)
268 
269 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
270 {
271         return p->se.cfs_rq;
272 }
273 
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
276 {
277         return se->cfs_rq;
278 }
279 
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
282 {
283         return grp->my_q;
284 }
285 
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
287 {
288         if (!cfs_rq->on_list) {
289                 /*
290                  * Ensure we either appear before our parent (if already
291                  * enqueued) or force our parent to appear after us when it is
292                  * enqueued.  The fact that we always enqueue bottom-up
293                  * reduces this to two cases.
294                  */
295                 if (cfs_rq->tg->parent &&
296                     cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
297                         list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
298                                 &rq_of(cfs_rq)->leaf_cfs_rq_list);
299                 } else {
300                         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
301                                 &rq_of(cfs_rq)->leaf_cfs_rq_list);
302                 }
303 
304                 cfs_rq->on_list = 1;
305         }
306 }
307 
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
309 {
310         if (cfs_rq->on_list) {
311                 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
312                 cfs_rq->on_list = 0;
313         }
314 }
315 
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318         list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
319 
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq *
322 is_same_group(struct sched_entity *se, struct sched_entity *pse)
323 {
324         if (se->cfs_rq == pse->cfs_rq)
325                 return se->cfs_rq;
326 
327         return NULL;
328 }
329 
330 static inline struct sched_entity *parent_entity(struct sched_entity *se)
331 {
332         return se->parent;
333 }
334 
335 static void
336 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
337 {
338         int se_depth, pse_depth;
339 
340         /*
341          * preemption test can be made between sibling entities who are in the
342          * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343          * both tasks until we find their ancestors who are siblings of common
344          * parent.
345          */
346 
347         /* First walk up until both entities are at same depth */
348         se_depth = (*se)->depth;
349         pse_depth = (*pse)->depth;
350 
351         while (se_depth > pse_depth) {
352                 se_depth--;
353                 *se = parent_entity(*se);
354         }
355 
356         while (pse_depth > se_depth) {
357                 pse_depth--;
358                 *pse = parent_entity(*pse);
359         }
360 
361         while (!is_same_group(*se, *pse)) {
362                 *se = parent_entity(*se);
363                 *pse = parent_entity(*pse);
364         }
365 }
366 
367 #else   /* !CONFIG_FAIR_GROUP_SCHED */
368 
369 static inline struct task_struct *task_of(struct sched_entity *se)
370 {
371         return container_of(se, struct task_struct, se);
372 }
373 
374 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
375 {
376         return container_of(cfs_rq, struct rq, cfs);
377 }
378 
379 #define entity_is_task(se)      1
380 
381 #define for_each_sched_entity(se) \
382                 for (; se; se = NULL)
383 
384 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
385 {
386         return &task_rq(p)->cfs;
387 }
388 
389 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
390 {
391         struct task_struct *p = task_of(se);
392         struct rq *rq = task_rq(p);
393 
394         return &rq->cfs;
395 }
396 
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
399 {
400         return NULL;
401 }
402 
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
404 {
405 }
406 
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
408 {
409 }
410 
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412                 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
413 
414 static inline struct sched_entity *parent_entity(struct sched_entity *se)
415 {
416         return NULL;
417 }
418 
419 static inline void
420 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
421 {
422 }
423 
424 #endif  /* CONFIG_FAIR_GROUP_SCHED */
425 
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
428 
429 /**************************************************************
430  * Scheduling class tree data structure manipulation methods:
431  */
432 
433 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
434 {
435         s64 delta = (s64)(vruntime - max_vruntime);
436         if (delta > 0)
437                 max_vruntime = vruntime;
438 
439         return max_vruntime;
440 }
441 
442 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
443 {
444         s64 delta = (s64)(vruntime - min_vruntime);
445         if (delta < 0)
446                 min_vruntime = vruntime;
447 
448         return min_vruntime;
449 }
450 
451 static inline int entity_before(struct sched_entity *a,
452                                 struct sched_entity *b)
453 {
454         return (s64)(a->vruntime - b->vruntime) < 0;
455 }
456 
457 static void update_min_vruntime(struct cfs_rq *cfs_rq)
458 {
459         u64 vruntime = cfs_rq->min_vruntime;
460 
461         if (cfs_rq->curr)
462                 vruntime = cfs_rq->curr->vruntime;
463 
464         if (cfs_rq->rb_leftmost) {
465                 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
466                                                    struct sched_entity,
467                                                    run_node);
468 
469                 if (!cfs_rq->curr)
470                         vruntime = se->vruntime;
471                 else
472                         vruntime = min_vruntime(vruntime, se->vruntime);
473         }
474 
475         /* ensure we never gain time by being placed backwards. */
476         cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
477 #ifndef CONFIG_64BIT
478         smp_wmb();
479         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
480 #endif
481 }
482 
483 /*
484  * Enqueue an entity into the rb-tree:
485  */
486 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
487 {
488         struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
489         struct rb_node *parent = NULL;
490         struct sched_entity *entry;
491         int leftmost = 1;
492 
493         /*
494          * Find the right place in the rbtree:
495          */
496         while (*link) {
497                 parent = *link;
498                 entry = rb_entry(parent, struct sched_entity, run_node);
499                 /*
500                  * We dont care about collisions. Nodes with
501                  * the same key stay together.
502                  */
503                 if (entity_before(se, entry)) {
504                         link = &parent->rb_left;
505                 } else {
506                         link = &parent->rb_right;
507                         leftmost = 0;
508                 }
509         }
510 
511         /*
512          * Maintain a cache of leftmost tree entries (it is frequently
513          * used):
514          */
515         if (leftmost)
516                 cfs_rq->rb_leftmost = &se->run_node;
517 
518         rb_link_node(&se->run_node, parent, link);
519         rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
520 }
521 
522 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
523 {
524         if (cfs_rq->rb_leftmost == &se->run_node) {
525                 struct rb_node *next_node;
526 
527                 next_node = rb_next(&se->run_node);
528                 cfs_rq->rb_leftmost = next_node;
529         }
530 
531         rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
532 }
533 
534 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
535 {
536         struct rb_node *left = cfs_rq->rb_leftmost;
537 
538         if (!left)
539                 return NULL;
540 
541         return rb_entry(left, struct sched_entity, run_node);
542 }
543 
544 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
545 {
546         struct rb_node *next = rb_next(&se->run_node);
547 
548         if (!next)
549                 return NULL;
550 
551         return rb_entry(next, struct sched_entity, run_node);
552 }
553 
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
556 {
557         struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
558 
559         if (!last)
560                 return NULL;
561 
562         return rb_entry(last, struct sched_entity, run_node);
563 }
564 
565 /**************************************************************
566  * Scheduling class statistics methods:
567  */
568 
569 int sched_proc_update_handler(struct ctl_table *table, int write,
570                 void __user *buffer, size_t *lenp,
571                 loff_t *ppos)
572 {
573         int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
574         unsigned int factor = get_update_sysctl_factor();
575 
576         if (ret || !write)
577                 return ret;
578 
579         sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
580                                         sysctl_sched_min_granularity);
581 
582 #define WRT_SYSCTL(name) \
583         (normalized_sysctl_##name = sysctl_##name / (factor))
584         WRT_SYSCTL(sched_min_granularity);
585         WRT_SYSCTL(sched_latency);
586         WRT_SYSCTL(sched_wakeup_granularity);
587 #undef WRT_SYSCTL
588 
589         return 0;
590 }
591 #endif
592 
593 /*
594  * delta /= w
595  */
596 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
597 {
598         if (unlikely(se->load.weight != NICE_0_LOAD))
599                 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
600 
601         return delta;
602 }
603 
604 /*
605  * The idea is to set a period in which each task runs once.
606  *
607  * When there are too many tasks (sched_nr_latency) we have to stretch
608  * this period because otherwise the slices get too small.
609  *
610  * p = (nr <= nl) ? l : l*nr/nl
611  */
612 static u64 __sched_period(unsigned long nr_running)
613 {
614         if (unlikely(nr_running > sched_nr_latency))
615                 return nr_running * sysctl_sched_min_granularity;
616         else
617                 return sysctl_sched_latency;
618 }
619 
620 /*
621  * We calculate the wall-time slice from the period by taking a part
622  * proportional to the weight.
623  *
624  * s = p*P[w/rw]
625  */
626 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
627 {
628         u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
629 
630         for_each_sched_entity(se) {
631                 struct load_weight *load;
632                 struct load_weight lw;
633 
634                 cfs_rq = cfs_rq_of(se);
635                 load = &cfs_rq->load;
636 
637                 if (unlikely(!se->on_rq)) {
638                         lw = cfs_rq->load;
639 
640                         update_load_add(&lw, se->load.weight);
641                         load = &lw;
642                 }
643                 slice = __calc_delta(slice, se->load.weight, load);
644         }
645         return slice;
646 }
647 
648 /*
649  * We calculate the vruntime slice of a to-be-inserted task.
650  *
651  * vs = s/w
652  */
653 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
654 {
655         return calc_delta_fair(sched_slice(cfs_rq, se), se);
656 }
657 
658 #ifdef CONFIG_SMP
659 static int select_idle_sibling(struct task_struct *p, int cpu);
660 static unsigned long task_h_load(struct task_struct *p);
661 
662 /*
663  * We choose a half-life close to 1 scheduling period.
664  * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
665  * dependent on this value.
666  */
667 #define LOAD_AVG_PERIOD 32
668 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
670 
671 /* Give new sched_entity start runnable values to heavy its load in infant time */
672 void init_entity_runnable_average(struct sched_entity *se)
673 {
674         struct sched_avg *sa = &se->avg;
675 
676         sa->last_update_time = 0;
677         /*
678          * sched_avg's period_contrib should be strictly less then 1024, so
679          * we give it 1023 to make sure it is almost a period (1024us), and
680          * will definitely be update (after enqueue).
681          */
682         sa->period_contrib = 1023;
683         sa->load_avg = scale_load_down(se->load.weight);
684         sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
685         sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
686         sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
687         /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
688 }
689 
690 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
691 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
692 #else
693 void init_entity_runnable_average(struct sched_entity *se)
694 {
695 }
696 #endif
697 
698 /*
699  * Update the current task's runtime statistics.
700  */
701 static void update_curr(struct cfs_rq *cfs_rq)
702 {
703         struct sched_entity *curr = cfs_rq->curr;
704         u64 now = rq_clock_task(rq_of(cfs_rq));
705         u64 delta_exec;
706 
707         if (unlikely(!curr))
708                 return;
709 
710         delta_exec = now - curr->exec_start;
711         if (unlikely((s64)delta_exec <= 0))
712                 return;
713 
714         curr->exec_start = now;
715 
716         schedstat_set(curr->statistics.exec_max,
717                       max(delta_exec, curr->statistics.exec_max));
718 
719         curr->sum_exec_runtime += delta_exec;
720         schedstat_add(cfs_rq, exec_clock, delta_exec);
721 
722         curr->vruntime += calc_delta_fair(delta_exec, curr);
723         update_min_vruntime(cfs_rq);
724 
725         if (entity_is_task(curr)) {
726                 struct task_struct *curtask = task_of(curr);
727 
728                 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
729                 cpuacct_charge(curtask, delta_exec);
730                 account_group_exec_runtime(curtask, delta_exec);
731         }
732 
733         account_cfs_rq_runtime(cfs_rq, delta_exec);
734 }
735 
736 static void update_curr_fair(struct rq *rq)
737 {
738         update_curr(cfs_rq_of(&rq->curr->se));
739 }
740 
741 #ifdef CONFIG_SCHEDSTATS
742 static inline void
743 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
744 {
745         u64 wait_start = rq_clock(rq_of(cfs_rq));
746 
747         if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
748             likely(wait_start > se->statistics.wait_start))
749                 wait_start -= se->statistics.wait_start;
750 
751         se->statistics.wait_start = wait_start;
752 }
753 
754 static void
755 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
756 {
757         struct task_struct *p;
758         u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
759 
760         if (entity_is_task(se)) {
761                 p = task_of(se);
762                 if (task_on_rq_migrating(p)) {
763                         /*
764                          * Preserve migrating task's wait time so wait_start
765                          * time stamp can be adjusted to accumulate wait time
766                          * prior to migration.
767                          */
768                         se->statistics.wait_start = delta;
769                         return;
770                 }
771                 trace_sched_stat_wait(p, delta);
772         }
773 
774         se->statistics.wait_max = max(se->statistics.wait_max, delta);
775         se->statistics.wait_count++;
776         se->statistics.wait_sum += delta;
777         se->statistics.wait_start = 0;
778 }
779 #else
780 static inline void
781 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
782 {
783 }
784 
785 static inline void
786 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
787 {
788 }
789 #endif
790 
791 /*
792  * Task is being enqueued - update stats:
793  */
794 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
795 {
796         /*
797          * Are we enqueueing a waiting task? (for current tasks
798          * a dequeue/enqueue event is a NOP)
799          */
800         if (se != cfs_rq->curr)
801                 update_stats_wait_start(cfs_rq, se);
802 }
803 
804 static inline void
805 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
806 {
807         /*
808          * Mark the end of the wait period if dequeueing a
809          * waiting task:
810          */
811         if (se != cfs_rq->curr)
812                 update_stats_wait_end(cfs_rq, se);
813 }
814 
815 /*
816  * We are picking a new current task - update its stats:
817  */
818 static inline void
819 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
820 {
821         /*
822          * We are starting a new run period:
823          */
824         se->exec_start = rq_clock_task(rq_of(cfs_rq));
825 }
826 
827 /**************************************************
828  * Scheduling class queueing methods:
829  */
830 
831 #ifdef CONFIG_NUMA_BALANCING
832 /*
833  * Approximate time to scan a full NUMA task in ms. The task scan period is
834  * calculated based on the tasks virtual memory size and
835  * numa_balancing_scan_size.
836  */
837 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
838 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
839 
840 /* Portion of address space to scan in MB */
841 unsigned int sysctl_numa_balancing_scan_size = 256;
842 
843 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
844 unsigned int sysctl_numa_balancing_scan_delay = 1000;
845 
846 static unsigned int task_nr_scan_windows(struct task_struct *p)
847 {
848         unsigned long rss = 0;
849         unsigned long nr_scan_pages;
850 
851         /*
852          * Calculations based on RSS as non-present and empty pages are skipped
853          * by the PTE scanner and NUMA hinting faults should be trapped based
854          * on resident pages
855          */
856         nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
857         rss = get_mm_rss(p->mm);
858         if (!rss)
859                 rss = nr_scan_pages;
860 
861         rss = round_up(rss, nr_scan_pages);
862         return rss / nr_scan_pages;
863 }
864 
865 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
866 #define MAX_SCAN_WINDOW 2560
867 
868 static unsigned int task_scan_min(struct task_struct *p)
869 {
870         unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
871         unsigned int scan, floor;
872         unsigned int windows = 1;
873 
874         if (scan_size < MAX_SCAN_WINDOW)
875                 windows = MAX_SCAN_WINDOW / scan_size;
876         floor = 1000 / windows;
877 
878         scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
879         return max_t(unsigned int, floor, scan);
880 }
881 
882 static unsigned int task_scan_max(struct task_struct *p)
883 {
884         unsigned int smin = task_scan_min(p);
885         unsigned int smax;
886 
887         /* Watch for min being lower than max due to floor calculations */
888         smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
889         return max(smin, smax);
890 }
891 
892 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
893 {
894         rq->nr_numa_running += (p->numa_preferred_nid != -1);
895         rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
896 }
897 
898 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
899 {
900         rq->nr_numa_running -= (p->numa_preferred_nid != -1);
901         rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
902 }
903 
904 struct numa_group {
905         atomic_t refcount;
906 
907         spinlock_t lock; /* nr_tasks, tasks */
908         int nr_tasks;
909         pid_t gid;
910 
911         struct rcu_head rcu;
912         nodemask_t active_nodes;
913         unsigned long total_faults;
914         /*
915          * Faults_cpu is used to decide whether memory should move
916          * towards the CPU. As a consequence, these stats are weighted
917          * more by CPU use than by memory faults.
918          */
919         unsigned long *faults_cpu;
920         unsigned long faults[0];
921 };
922 
923 /* Shared or private faults. */
924 #define NR_NUMA_HINT_FAULT_TYPES 2
925 
926 /* Memory and CPU locality */
927 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
928 
929 /* Averaged statistics, and temporary buffers. */
930 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
931 
932 pid_t task_numa_group_id(struct task_struct *p)
933 {
934         return p->numa_group ? p->numa_group->gid : 0;
935 }
936 
937 /*
938  * The averaged statistics, shared & private, memory & cpu,
939  * occupy the first half of the array. The second half of the
940  * array is for current counters, which are averaged into the
941  * first set by task_numa_placement.
942  */
943 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
944 {
945         return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
946 }
947 
948 static inline unsigned long task_faults(struct task_struct *p, int nid)
949 {
950         if (!p->numa_faults)
951                 return 0;
952 
953         return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
954                 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
955 }
956 
957 static inline unsigned long group_faults(struct task_struct *p, int nid)
958 {
959         if (!p->numa_group)
960                 return 0;
961 
962         return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
963                 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
964 }
965 
966 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
967 {
968         return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
969                 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
970 }
971 
972 /* Handle placement on systems where not all nodes are directly connected. */
973 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
974                                         int maxdist, bool task)
975 {
976         unsigned long score = 0;
977         int node;
978 
979         /*
980          * All nodes are directly connected, and the same distance
981          * from each other. No need for fancy placement algorithms.
982          */
983         if (sched_numa_topology_type == NUMA_DIRECT)
984                 return 0;
985 
986         /*
987          * This code is called for each node, introducing N^2 complexity,
988          * which should be ok given the number of nodes rarely exceeds 8.
989          */
990         for_each_online_node(node) {
991                 unsigned long faults;
992                 int dist = node_distance(nid, node);
993 
994                 /*
995                  * The furthest away nodes in the system are not interesting
996                  * for placement; nid was already counted.
997                  */
998                 if (dist == sched_max_numa_distance || node == nid)
999                         continue;
1000 
1001                 /*
1002                  * On systems with a backplane NUMA topology, compare groups
1003                  * of nodes, and move tasks towards the group with the most
1004                  * memory accesses. When comparing two nodes at distance
1005                  * "hoplimit", only nodes closer by than "hoplimit" are part
1006                  * of each group. Skip other nodes.
1007                  */
1008                 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1009                                         dist > maxdist)
1010                         continue;
1011 
1012                 /* Add up the faults from nearby nodes. */
1013                 if (task)
1014                         faults = task_faults(p, node);
1015                 else
1016                         faults = group_faults(p, node);
1017 
1018                 /*
1019                  * On systems with a glueless mesh NUMA topology, there are
1020                  * no fixed "groups of nodes". Instead, nodes that are not
1021                  * directly connected bounce traffic through intermediate
1022                  * nodes; a numa_group can occupy any set of nodes.
1023                  * The further away a node is, the less the faults count.
1024                  * This seems to result in good task placement.
1025                  */
1026                 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1027                         faults *= (sched_max_numa_distance - dist);
1028                         faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1029                 }
1030 
1031                 score += faults;
1032         }
1033 
1034         return score;
1035 }
1036 
1037 /*
1038  * These return the fraction of accesses done by a particular task, or
1039  * task group, on a particular numa node.  The group weight is given a
1040  * larger multiplier, in order to group tasks together that are almost
1041  * evenly spread out between numa nodes.
1042  */
1043 static inline unsigned long task_weight(struct task_struct *p, int nid,
1044                                         int dist)
1045 {
1046         unsigned long faults, total_faults;
1047 
1048         if (!p->numa_faults)
1049                 return 0;
1050 
1051         total_faults = p->total_numa_faults;
1052 
1053         if (!total_faults)
1054                 return 0;
1055 
1056         faults = task_faults(p, nid);
1057         faults += score_nearby_nodes(p, nid, dist, true);
1058 
1059         return 1000 * faults / total_faults;
1060 }
1061 
1062 static inline unsigned long group_weight(struct task_struct *p, int nid,
1063                                          int dist)
1064 {
1065         unsigned long faults, total_faults;
1066 
1067         if (!p->numa_group)
1068                 return 0;
1069 
1070         total_faults = p->numa_group->total_faults;
1071 
1072         if (!total_faults)
1073                 return 0;
1074 
1075         faults = group_faults(p, nid);
1076         faults += score_nearby_nodes(p, nid, dist, false);
1077 
1078         return 1000 * faults / total_faults;
1079 }
1080 
1081 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1082                                 int src_nid, int dst_cpu)
1083 {
1084         struct numa_group *ng = p->numa_group;
1085         int dst_nid = cpu_to_node(dst_cpu);
1086         int last_cpupid, this_cpupid;
1087 
1088         this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1089 
1090         /*
1091          * Multi-stage node selection is used in conjunction with a periodic
1092          * migration fault to build a temporal task<->page relation. By using
1093          * a two-stage filter we remove short/unlikely relations.
1094          *
1095          * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1096          * a task's usage of a particular page (n_p) per total usage of this
1097          * page (n_t) (in a given time-span) to a probability.
1098          *
1099          * Our periodic faults will sample this probability and getting the
1100          * same result twice in a row, given these samples are fully
1101          * independent, is then given by P(n)^2, provided our sample period
1102          * is sufficiently short compared to the usage pattern.
1103          *
1104          * This quadric squishes small probabilities, making it less likely we
1105          * act on an unlikely task<->page relation.
1106          */
1107         last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1108         if (!cpupid_pid_unset(last_cpupid) &&
1109                                 cpupid_to_nid(last_cpupid) != dst_nid)
1110                 return false;
1111 
1112         /* Always allow migrate on private faults */
1113         if (cpupid_match_pid(p, last_cpupid))
1114                 return true;
1115 
1116         /* A shared fault, but p->numa_group has not been set up yet. */
1117         if (!ng)
1118                 return true;
1119 
1120         /*
1121          * Do not migrate if the destination is not a node that
1122          * is actively used by this numa group.
1123          */
1124         if (!node_isset(dst_nid, ng->active_nodes))
1125                 return false;
1126 
1127         /*
1128          * Source is a node that is not actively used by this
1129          * numa group, while the destination is. Migrate.
1130          */
1131         if (!node_isset(src_nid, ng->active_nodes))
1132                 return true;
1133 
1134         /*
1135          * Both source and destination are nodes in active
1136          * use by this numa group. Maximize memory bandwidth
1137          * by migrating from more heavily used groups, to less
1138          * heavily used ones, spreading the load around.
1139          * Use a 1/4 hysteresis to avoid spurious page movement.
1140          */
1141         return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1142 }
1143 
1144 static unsigned long weighted_cpuload(const int cpu);
1145 static unsigned long source_load(int cpu, int type);
1146 static unsigned long target_load(int cpu, int type);
1147 static unsigned long capacity_of(int cpu);
1148 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1149 
1150 /* Cached statistics for all CPUs within a node */
1151 struct numa_stats {
1152         unsigned long nr_running;
1153         unsigned long load;
1154 
1155         /* Total compute capacity of CPUs on a node */
1156         unsigned long compute_capacity;
1157 
1158         /* Approximate capacity in terms of runnable tasks on a node */
1159         unsigned long task_capacity;
1160         int has_free_capacity;
1161 };
1162 
1163 /*
1164  * XXX borrowed from update_sg_lb_stats
1165  */
1166 static void update_numa_stats(struct numa_stats *ns, int nid)
1167 {
1168         int smt, cpu, cpus = 0;
1169         unsigned long capacity;
1170 
1171         memset(ns, 0, sizeof(*ns));
1172         for_each_cpu(cpu, cpumask_of_node(nid)) {
1173                 struct rq *rq = cpu_rq(cpu);
1174 
1175                 ns->nr_running += rq->nr_running;
1176                 ns->load += weighted_cpuload(cpu);
1177                 ns->compute_capacity += capacity_of(cpu);
1178 
1179                 cpus++;
1180         }
1181 
1182         /*
1183          * If we raced with hotplug and there are no CPUs left in our mask
1184          * the @ns structure is NULL'ed and task_numa_compare() will
1185          * not find this node attractive.
1186          *
1187          * We'll either bail at !has_free_capacity, or we'll detect a huge
1188          * imbalance and bail there.
1189          */
1190         if (!cpus)
1191                 return;
1192 
1193         /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1194         smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1195         capacity = cpus / smt; /* cores */
1196 
1197         ns->task_capacity = min_t(unsigned, capacity,
1198                 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1199         ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1200 }
1201 
1202 struct task_numa_env {
1203         struct task_struct *p;
1204 
1205         int src_cpu, src_nid;
1206         int dst_cpu, dst_nid;
1207 
1208         struct numa_stats src_stats, dst_stats;
1209 
1210         int imbalance_pct;
1211         int dist;
1212 
1213         struct task_struct *best_task;
1214         long best_imp;
1215         int best_cpu;
1216 };
1217 
1218 static void task_numa_assign(struct task_numa_env *env,
1219                              struct task_struct *p, long imp)
1220 {
1221         if (env->best_task)
1222                 put_task_struct(env->best_task);
1223 
1224         env->best_task = p;
1225         env->best_imp = imp;
1226         env->best_cpu = env->dst_cpu;
1227 }
1228 
1229 static bool load_too_imbalanced(long src_load, long dst_load,
1230                                 struct task_numa_env *env)
1231 {
1232         long imb, old_imb;
1233         long orig_src_load, orig_dst_load;
1234         long src_capacity, dst_capacity;
1235 
1236         /*
1237          * The load is corrected for the CPU capacity available on each node.
1238          *
1239          * src_load        dst_load
1240          * ------------ vs ---------
1241          * src_capacity    dst_capacity
1242          */
1243         src_capacity = env->src_stats.compute_capacity;
1244         dst_capacity = env->dst_stats.compute_capacity;
1245 
1246         /* We care about the slope of the imbalance, not the direction. */
1247         if (dst_load < src_load)
1248                 swap(dst_load, src_load);
1249 
1250         /* Is the difference below the threshold? */
1251         imb = dst_load * src_capacity * 100 -
1252               src_load * dst_capacity * env->imbalance_pct;
1253         if (imb <= 0)
1254                 return false;
1255 
1256         /*
1257          * The imbalance is above the allowed threshold.
1258          * Compare it with the old imbalance.
1259          */
1260         orig_src_load = env->src_stats.load;
1261         orig_dst_load = env->dst_stats.load;
1262 
1263         if (orig_dst_load < orig_src_load)
1264                 swap(orig_dst_load, orig_src_load);
1265 
1266         old_imb = orig_dst_load * src_capacity * 100 -
1267                   orig_src_load * dst_capacity * env->imbalance_pct;
1268 
1269         /* Would this change make things worse? */
1270         return (imb > old_imb);
1271 }
1272 
1273 /*
1274  * This checks if the overall compute and NUMA accesses of the system would
1275  * be improved if the source tasks was migrated to the target dst_cpu taking
1276  * into account that it might be best if task running on the dst_cpu should
1277  * be exchanged with the source task
1278  */
1279 static void task_numa_compare(struct task_numa_env *env,
1280                               long taskimp, long groupimp)
1281 {
1282         struct rq *src_rq = cpu_rq(env->src_cpu);
1283         struct rq *dst_rq = cpu_rq(env->dst_cpu);
1284         struct task_struct *cur;
1285         long src_load, dst_load;
1286         long load;
1287         long imp = env->p->numa_group ? groupimp : taskimp;
1288         long moveimp = imp;
1289         int dist = env->dist;
1290         bool assigned = false;
1291 
1292         rcu_read_lock();
1293 
1294         raw_spin_lock_irq(&dst_rq->lock);
1295         cur = dst_rq->curr;
1296         /*
1297          * No need to move the exiting task or idle task.
1298          */
1299         if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1300                 cur = NULL;
1301         else {
1302                 /*
1303                  * The task_struct must be protected here to protect the
1304                  * p->numa_faults access in the task_weight since the
1305                  * numa_faults could already be freed in the following path:
1306                  * finish_task_switch()
1307                  *     --> put_task_struct()
1308                  *         --> __put_task_struct()
1309                  *             --> task_numa_free()
1310                  */
1311                 get_task_struct(cur);
1312         }
1313 
1314         raw_spin_unlock_irq(&dst_rq->lock);
1315 
1316         /*
1317          * Because we have preemption enabled we can get migrated around and
1318          * end try selecting ourselves (current == env->p) as a swap candidate.
1319          */
1320         if (cur == env->p)
1321                 goto unlock;
1322 
1323         /*
1324          * "imp" is the fault differential for the source task between the
1325          * source and destination node. Calculate the total differential for
1326          * the source task and potential destination task. The more negative
1327          * the value is, the more rmeote accesses that would be expected to
1328          * be incurred if the tasks were swapped.
1329          */
1330         if (cur) {
1331                 /* Skip this swap candidate if cannot move to the source cpu */
1332                 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1333                         goto unlock;
1334 
1335                 /*
1336                  * If dst and source tasks are in the same NUMA group, or not
1337                  * in any group then look only at task weights.
1338                  */
1339                 if (cur->numa_group == env->p->numa_group) {
1340                         imp = taskimp + task_weight(cur, env->src_nid, dist) -
1341                               task_weight(cur, env->dst_nid, dist);
1342                         /*
1343                          * Add some hysteresis to prevent swapping the
1344                          * tasks within a group over tiny differences.
1345                          */
1346                         if (cur->numa_group)
1347                                 imp -= imp/16;
1348                 } else {
1349                         /*
1350                          * Compare the group weights. If a task is all by
1351                          * itself (not part of a group), use the task weight
1352                          * instead.
1353                          */
1354                         if (cur->numa_group)
1355                                 imp += group_weight(cur, env->src_nid, dist) -
1356                                        group_weight(cur, env->dst_nid, dist);
1357                         else
1358                                 imp += task_weight(cur, env->src_nid, dist) -
1359                                        task_weight(cur, env->dst_nid, dist);
1360                 }
1361         }
1362 
1363         if (imp <= env->best_imp && moveimp <= env->best_imp)
1364                 goto unlock;
1365 
1366         if (!cur) {
1367                 /* Is there capacity at our destination? */
1368                 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1369                     !env->dst_stats.has_free_capacity)
1370                         goto unlock;
1371 
1372                 goto balance;
1373         }
1374 
1375         /* Balance doesn't matter much if we're running a task per cpu */
1376         if (imp > env->best_imp && src_rq->nr_running == 1 &&
1377                         dst_rq->nr_running == 1)
1378                 goto assign;
1379 
1380         /*
1381          * In the overloaded case, try and keep the load balanced.
1382          */
1383 balance:
1384         load = task_h_load(env->p);
1385         dst_load = env->dst_stats.load + load;
1386         src_load = env->src_stats.load - load;
1387 
1388         if (moveimp > imp && moveimp > env->best_imp) {
1389                 /*
1390                  * If the improvement from just moving env->p direction is
1391                  * better than swapping tasks around, check if a move is
1392                  * possible. Store a slightly smaller score than moveimp,
1393                  * so an actually idle CPU will win.
1394                  */
1395                 if (!load_too_imbalanced(src_load, dst_load, env)) {
1396                         imp = moveimp - 1;
1397                         put_task_struct(cur);
1398                         cur = NULL;
1399                         goto assign;
1400                 }
1401         }
1402 
1403         if (imp <= env->best_imp)
1404                 goto unlock;
1405 
1406         if (cur) {
1407                 load = task_h_load(cur);
1408                 dst_load -= load;
1409                 src_load += load;
1410         }
1411 
1412         if (load_too_imbalanced(src_load, dst_load, env))
1413                 goto unlock;
1414 
1415         /*
1416          * One idle CPU per node is evaluated for a task numa move.
1417          * Call select_idle_sibling to maybe find a better one.
1418          */
1419         if (!cur)
1420                 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1421 
1422 assign:
1423         assigned = true;
1424         task_numa_assign(env, cur, imp);
1425 unlock:
1426         rcu_read_unlock();
1427         /*
1428          * The dst_rq->curr isn't assigned. The protection for task_struct is
1429          * finished.
1430          */
1431         if (cur && !assigned)
1432                 put_task_struct(cur);
1433 }
1434 
1435 static void task_numa_find_cpu(struct task_numa_env *env,
1436                                 long taskimp, long groupimp)
1437 {
1438         int cpu;
1439 
1440         for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1441                 /* Skip this CPU if the source task cannot migrate */
1442                 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1443                         continue;
1444 
1445                 env->dst_cpu = cpu;
1446                 task_numa_compare(env, taskimp, groupimp);
1447         }
1448 }
1449 
1450 /* Only move tasks to a NUMA node less busy than the current node. */
1451 static bool numa_has_capacity(struct task_numa_env *env)
1452 {
1453         struct numa_stats *src = &env->src_stats;
1454         struct numa_stats *dst = &env->dst_stats;
1455 
1456         if (src->has_free_capacity && !dst->has_free_capacity)
1457                 return false;
1458 
1459         /*
1460          * Only consider a task move if the source has a higher load
1461          * than the destination, corrected for CPU capacity on each node.
1462          *
1463          *      src->load                dst->load
1464          * --------------------- vs ---------------------
1465          * src->compute_capacity    dst->compute_capacity
1466          */
1467         if (src->load * dst->compute_capacity * env->imbalance_pct >
1468 
1469             dst->load * src->compute_capacity * 100)
1470                 return true;
1471 
1472         return false;
1473 }
1474 
1475 static int task_numa_migrate(struct task_struct *p)
1476 {
1477         struct task_numa_env env = {
1478                 .p = p,
1479 
1480                 .src_cpu = task_cpu(p),
1481                 .src_nid = task_node(p),
1482 
1483                 .imbalance_pct = 112,
1484 
1485                 .best_task = NULL,
1486                 .best_imp = 0,
1487                 .best_cpu = -1
1488         };
1489         struct sched_domain *sd;
1490         unsigned long taskweight, groupweight;
1491         int nid, ret, dist;
1492         long taskimp, groupimp;
1493 
1494         /*
1495          * Pick the lowest SD_NUMA domain, as that would have the smallest
1496          * imbalance and would be the first to start moving tasks about.
1497          *
1498          * And we want to avoid any moving of tasks about, as that would create
1499          * random movement of tasks -- counter the numa conditions we're trying
1500          * to satisfy here.
1501          */
1502         rcu_read_lock();
1503         sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1504         if (sd)
1505                 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1506         rcu_read_unlock();
1507 
1508         /*
1509          * Cpusets can break the scheduler domain tree into smaller
1510          * balance domains, some of which do not cross NUMA boundaries.
1511          * Tasks that are "trapped" in such domains cannot be migrated
1512          * elsewhere, so there is no point in (re)trying.
1513          */
1514         if (unlikely(!sd)) {
1515                 p->numa_preferred_nid = task_node(p);
1516                 return -EINVAL;
1517         }
1518 
1519         env.dst_nid = p->numa_preferred_nid;
1520         dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1521         taskweight = task_weight(p, env.src_nid, dist);
1522         groupweight = group_weight(p, env.src_nid, dist);
1523         update_numa_stats(&env.src_stats, env.src_nid);
1524         taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1525         groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1526         update_numa_stats(&env.dst_stats, env.dst_nid);
1527 
1528         /* Try to find a spot on the preferred nid. */
1529         if (numa_has_capacity(&env))
1530                 task_numa_find_cpu(&env, taskimp, groupimp);
1531 
1532         /*
1533          * Look at other nodes in these cases:
1534          * - there is no space available on the preferred_nid
1535          * - the task is part of a numa_group that is interleaved across
1536          *   multiple NUMA nodes; in order to better consolidate the group,
1537          *   we need to check other locations.
1538          */
1539         if (env.best_cpu == -1 || (p->numa_group &&
1540                         nodes_weight(p->numa_group->active_nodes) > 1)) {
1541                 for_each_online_node(nid) {
1542                         if (nid == env.src_nid || nid == p->numa_preferred_nid)
1543                                 continue;
1544 
1545                         dist = node_distance(env.src_nid, env.dst_nid);
1546                         if (sched_numa_topology_type == NUMA_BACKPLANE &&
1547                                                 dist != env.dist) {
1548                                 taskweight = task_weight(p, env.src_nid, dist);
1549                                 groupweight = group_weight(p, env.src_nid, dist);
1550                         }
1551 
1552                         /* Only consider nodes where both task and groups benefit */
1553                         taskimp = task_weight(p, nid, dist) - taskweight;
1554                         groupimp = group_weight(p, nid, dist) - groupweight;
1555                         if (taskimp < 0 && groupimp < 0)
1556                                 continue;
1557 
1558                         env.dist = dist;
1559                         env.dst_nid = nid;
1560                         update_numa_stats(&env.dst_stats, env.dst_nid);
1561                         if (numa_has_capacity(&env))
1562                                 task_numa_find_cpu(&env, taskimp, groupimp);
1563                 }
1564         }
1565 
1566         /*
1567          * If the task is part of a workload that spans multiple NUMA nodes,
1568          * and is migrating into one of the workload's active nodes, remember
1569          * this node as the task's preferred numa node, so the workload can
1570          * settle down.
1571          * A task that migrated to a second choice node will be better off
1572          * trying for a better one later. Do not set the preferred node here.
1573          */
1574         if (p->numa_group) {
1575                 if (env.best_cpu == -1)
1576                         nid = env.src_nid;
1577                 else
1578                         nid = env.dst_nid;
1579 
1580                 if (node_isset(nid, p->numa_group->active_nodes))
1581                         sched_setnuma(p, env.dst_nid);
1582         }
1583 
1584         /* No better CPU than the current one was found. */
1585         if (env.best_cpu == -1)
1586                 return -EAGAIN;
1587 
1588         /*
1589          * Reset the scan period if the task is being rescheduled on an
1590          * alternative node to recheck if the tasks is now properly placed.
1591          */
1592         p->numa_scan_period = task_scan_min(p);
1593 
1594         if (env.best_task == NULL) {
1595                 ret = migrate_task_to(p, env.best_cpu);
1596                 if (ret != 0)
1597                         trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1598                 return ret;
1599         }
1600 
1601         ret = migrate_swap(p, env.best_task);
1602         if (ret != 0)
1603                 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1604         put_task_struct(env.best_task);
1605         return ret;
1606 }
1607 
1608 /* Attempt to migrate a task to a CPU on the preferred node. */
1609 static void numa_migrate_preferred(struct task_struct *p)
1610 {
1611         unsigned long interval = HZ;
1612 
1613         /* This task has no NUMA fault statistics yet */
1614         if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1615                 return;
1616 
1617         /* Periodically retry migrating the task to the preferred node */
1618         interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1619         p->numa_migrate_retry = jiffies + interval;
1620 
1621         /* Success if task is already running on preferred CPU */
1622         if (task_node(p) == p->numa_preferred_nid)
1623                 return;
1624 
1625         /* Otherwise, try migrate to a CPU on the preferred node */
1626         task_numa_migrate(p);
1627 }
1628 
1629 /*
1630  * Find the nodes on which the workload is actively running. We do this by
1631  * tracking the nodes from which NUMA hinting faults are triggered. This can
1632  * be different from the set of nodes where the workload's memory is currently
1633  * located.
1634  *
1635  * The bitmask is used to make smarter decisions on when to do NUMA page
1636  * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1637  * are added when they cause over 6/16 of the maximum number of faults, but
1638  * only removed when they drop below 3/16.
1639  */
1640 static void update_numa_active_node_mask(struct numa_group *numa_group)
1641 {
1642         unsigned long faults, max_faults = 0;
1643         int nid;
1644 
1645         for_each_online_node(nid) {
1646                 faults = group_faults_cpu(numa_group, nid);
1647                 if (faults > max_faults)
1648                         max_faults = faults;
1649         }
1650 
1651         for_each_online_node(nid) {
1652                 faults = group_faults_cpu(numa_group, nid);
1653                 if (!node_isset(nid, numa_group->active_nodes)) {
1654                         if (faults > max_faults * 6 / 16)
1655                                 node_set(nid, numa_group->active_nodes);
1656                 } else if (faults < max_faults * 3 / 16)
1657                         node_clear(nid, numa_group->active_nodes);
1658         }
1659 }
1660 
1661 /*
1662  * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1663  * increments. The more local the fault statistics are, the higher the scan
1664  * period will be for the next scan window. If local/(local+remote) ratio is
1665  * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1666  * the scan period will decrease. Aim for 70% local accesses.
1667  */
1668 #define NUMA_PERIOD_SLOTS 10
1669 #define NUMA_PERIOD_THRESHOLD 7
1670 
1671 /*
1672  * Increase the scan period (slow down scanning) if the majority of
1673  * our memory is already on our local node, or if the majority of
1674  * the page accesses are shared with other processes.
1675  * Otherwise, decrease the scan period.
1676  */
1677 static void update_task_scan_period(struct task_struct *p,
1678                         unsigned long shared, unsigned long private)
1679 {
1680         unsigned int period_slot;
1681         int ratio;
1682         int diff;
1683 
1684         unsigned long remote = p->numa_faults_locality[0];
1685         unsigned long local = p->numa_faults_locality[1];
1686 
1687         /*
1688          * If there were no record hinting faults then either the task is
1689          * completely idle or all activity is areas that are not of interest
1690          * to automatic numa balancing. Related to that, if there were failed
1691          * migration then it implies we are migrating too quickly or the local
1692          * node is overloaded. In either case, scan slower
1693          */
1694         if (local + shared == 0 || p->numa_faults_locality[2]) {
1695                 p->numa_scan_period = min(p->numa_scan_period_max,
1696                         p->numa_scan_period << 1);
1697 
1698                 p->mm->numa_next_scan = jiffies +
1699                         msecs_to_jiffies(p->numa_scan_period);
1700 
1701                 return;
1702         }
1703 
1704         /*
1705          * Prepare to scale scan period relative to the current period.
1706          *       == NUMA_PERIOD_THRESHOLD scan period stays the same
1707          *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1708          *       >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1709          */
1710         period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1711         ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1712         if (ratio >= NUMA_PERIOD_THRESHOLD) {
1713                 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1714                 if (!slot)
1715                         slot = 1;
1716                 diff = slot * period_slot;
1717         } else {
1718                 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1719 
1720                 /*
1721                  * Scale scan rate increases based on sharing. There is an
1722                  * inverse relationship between the degree of sharing and
1723                  * the adjustment made to the scanning period. Broadly
1724                  * speaking the intent is that there is little point
1725                  * scanning faster if shared accesses dominate as it may
1726                  * simply bounce migrations uselessly
1727                  */
1728                 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1729                 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1730         }
1731 
1732         p->numa_scan_period = clamp(p->numa_scan_period + diff,
1733                         task_scan_min(p), task_scan_max(p));
1734         memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1735 }
1736 
1737 /*
1738  * Get the fraction of time the task has been running since the last
1739  * NUMA placement cycle. The scheduler keeps similar statistics, but
1740  * decays those on a 32ms period, which is orders of magnitude off
1741  * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1742  * stats only if the task is so new there are no NUMA statistics yet.
1743  */
1744 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1745 {
1746         u64 runtime, delta, now;
1747         /* Use the start of this time slice to avoid calculations. */
1748         now = p->se.exec_start;
1749         runtime = p->se.sum_exec_runtime;
1750 
1751         if (p->last_task_numa_placement) {
1752                 delta = runtime - p->last_sum_exec_runtime;
1753                 *period = now - p->last_task_numa_placement;
1754         } else {
1755                 delta = p->se.avg.load_sum / p->se.load.weight;
1756                 *period = LOAD_AVG_MAX;
1757         }
1758 
1759         p->last_sum_exec_runtime = runtime;
1760         p->last_task_numa_placement = now;
1761 
1762         return delta;
1763 }
1764 
1765 /*
1766  * Determine the preferred nid for a task in a numa_group. This needs to
1767  * be done in a way that produces consistent results with group_weight,
1768  * otherwise workloads might not converge.
1769  */
1770 static int preferred_group_nid(struct task_struct *p, int nid)
1771 {
1772         nodemask_t nodes;
1773         int dist;
1774 
1775         /* Direct connections between all NUMA nodes. */
1776         if (sched_numa_topology_type == NUMA_DIRECT)
1777                 return nid;
1778 
1779         /*
1780          * On a system with glueless mesh NUMA topology, group_weight
1781          * scores nodes according to the number of NUMA hinting faults on
1782          * both the node itself, and on nearby nodes.
1783          */
1784         if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1785                 unsigned long score, max_score = 0;
1786                 int node, max_node = nid;
1787 
1788                 dist = sched_max_numa_distance;
1789 
1790                 for_each_online_node(node) {
1791                         score = group_weight(p, node, dist);
1792                         if (score > max_score) {
1793                                 max_score = score;
1794                                 max_node = node;
1795                         }
1796                 }
1797                 return max_node;
1798         }
1799 
1800         /*
1801          * Finding the preferred nid in a system with NUMA backplane
1802          * interconnect topology is more involved. The goal is to locate
1803          * tasks from numa_groups near each other in the system, and
1804          * untangle workloads from different sides of the system. This requires
1805          * searching down the hierarchy of node groups, recursively searching
1806          * inside the highest scoring group of nodes. The nodemask tricks
1807          * keep the complexity of the search down.
1808          */
1809         nodes = node_online_map;
1810         for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1811                 unsigned long max_faults = 0;
1812                 nodemask_t max_group = NODE_MASK_NONE;
1813                 int a, b;
1814 
1815                 /* Are there nodes at this distance from each other? */
1816                 if (!find_numa_distance(dist))
1817                         continue;
1818 
1819                 for_each_node_mask(a, nodes) {
1820                         unsigned long faults = 0;
1821                         nodemask_t this_group;
1822                         nodes_clear(this_group);
1823 
1824                         /* Sum group's NUMA faults; includes a==b case. */
1825                         for_each_node_mask(b, nodes) {
1826                                 if (node_distance(a, b) < dist) {
1827                                         faults += group_faults(p, b);
1828                                         node_set(b, this_group);
1829                                         node_clear(b, nodes);
1830                                 }
1831                         }
1832 
1833                         /* Remember the top group. */
1834                         if (faults > max_faults) {
1835                                 max_faults = faults;
1836                                 max_group = this_group;
1837                                 /*
1838                                  * subtle: at the smallest distance there is
1839                                  * just one node left in each "group", the
1840                                  * winner is the preferred nid.
1841                                  */
1842                                 nid = a;
1843                         }
1844                 }
1845                 /* Next round, evaluate the nodes within max_group. */
1846                 if (!max_faults)
1847                         break;
1848                 nodes = max_group;
1849         }
1850         return nid;
1851 }
1852 
1853 static void task_numa_placement(struct task_struct *p)
1854 {
1855         int seq, nid, max_nid = -1, max_group_nid = -1;
1856         unsigned long max_faults = 0, max_group_faults = 0;
1857         unsigned long fault_types[2] = { 0, 0 };
1858         unsigned long total_faults;
1859         u64 runtime, period;
1860         spinlock_t *group_lock = NULL;
1861 
1862         /*
1863          * The p->mm->numa_scan_seq field gets updated without
1864          * exclusive access. Use READ_ONCE() here to ensure
1865          * that the field is read in a single access:
1866          */
1867         seq = READ_ONCE(p->mm->numa_scan_seq);
1868         if (p->numa_scan_seq == seq)
1869                 return;
1870         p->numa_scan_seq = seq;
1871         p->numa_scan_period_max = task_scan_max(p);
1872 
1873         total_faults = p->numa_faults_locality[0] +
1874                        p->numa_faults_locality[1];
1875         runtime = numa_get_avg_runtime(p, &period);
1876 
1877         /* If the task is part of a group prevent parallel updates to group stats */
1878         if (p->numa_group) {
1879                 group_lock = &p->numa_group->lock;
1880                 spin_lock_irq(group_lock);
1881         }
1882 
1883         /* Find the node with the highest number of faults */
1884         for_each_online_node(nid) {
1885                 /* Keep track of the offsets in numa_faults array */
1886                 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1887                 unsigned long faults = 0, group_faults = 0;
1888                 int priv;
1889 
1890                 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1891                         long diff, f_diff, f_weight;
1892 
1893                         mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1894                         membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1895                         cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1896                         cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1897 
1898                         /* Decay existing window, copy faults since last scan */
1899                         diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1900                         fault_types[priv] += p->numa_faults[membuf_idx];
1901                         p->numa_faults[membuf_idx] = 0;
1902 
1903                         /*
1904                          * Normalize the faults_from, so all tasks in a group
1905                          * count according to CPU use, instead of by the raw
1906                          * number of faults. Tasks with little runtime have
1907                          * little over-all impact on throughput, and thus their
1908                          * faults are less important.
1909                          */
1910                         f_weight = div64_u64(runtime << 16, period + 1);
1911                         f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1912                                    (total_faults + 1);
1913                         f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1914                         p->numa_faults[cpubuf_idx] = 0;
1915 
1916                         p->numa_faults[mem_idx] += diff;
1917                         p->numa_faults[cpu_idx] += f_diff;
1918                         faults += p->numa_faults[mem_idx];
1919                         p->total_numa_faults += diff;
1920                         if (p->numa_group) {
1921                                 /*
1922                                  * safe because we can only change our own group
1923                                  *
1924                                  * mem_idx represents the offset for a given
1925                                  * nid and priv in a specific region because it
1926                                  * is at the beginning of the numa_faults array.
1927                                  */
1928                                 p->numa_group->faults[mem_idx] += diff;
1929                                 p->numa_group->faults_cpu[mem_idx] += f_diff;
1930                                 p->numa_group->total_faults += diff;
1931                                 group_faults += p->numa_group->faults[mem_idx];
1932                         }
1933                 }
1934 
1935                 if (faults > max_faults) {
1936                         max_faults = faults;
1937                         max_nid = nid;
1938                 }
1939 
1940                 if (group_faults > max_group_faults) {
1941                         max_group_faults = group_faults;
1942                         max_group_nid = nid;
1943                 }
1944         }
1945 
1946         update_task_scan_period(p, fault_types[0], fault_types[1]);
1947 
1948         if (p->numa_group) {
1949                 update_numa_active_node_mask(p->numa_group);
1950                 spin_unlock_irq(group_lock);
1951                 max_nid = preferred_group_nid(p, max_group_nid);
1952         }
1953 
1954         if (max_faults) {
1955                 /* Set the new preferred node */
1956                 if (max_nid != p->numa_preferred_nid)
1957                         sched_setnuma(p, max_nid);
1958 
1959                 if (task_node(p) != p->numa_preferred_nid)
1960                         numa_migrate_preferred(p);
1961         }
1962 }
1963 
1964 static inline int get_numa_group(struct numa_group *grp)
1965 {
1966         return atomic_inc_not_zero(&grp->refcount);
1967 }
1968 
1969 static inline void put_numa_group(struct numa_group *grp)
1970 {
1971         if (atomic_dec_and_test(&grp->refcount))
1972                 kfree_rcu(grp, rcu);
1973 }
1974 
1975 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1976                         int *priv)
1977 {
1978         struct numa_group *grp, *my_grp;
1979         struct task_struct *tsk;
1980         bool join = false;
1981         int cpu = cpupid_to_cpu(cpupid);
1982         int i;
1983 
1984         if (unlikely(!p->numa_group)) {
1985                 unsigned int size = sizeof(struct numa_group) +
1986                                     4*nr_node_ids*sizeof(unsigned long);
1987 
1988                 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1989                 if (!grp)
1990                         return;
1991 
1992                 atomic_set(&grp->refcount, 1);
1993                 spin_lock_init(&grp->lock);
1994                 grp->gid = p->pid;
1995                 /* Second half of the array tracks nids where faults happen */
1996                 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1997                                                 nr_node_ids;
1998 
1999                 node_set(task_node(current), grp->active_nodes);
2000 
2001                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2002                         grp->faults[i] = p->numa_faults[i];
2003 
2004                 grp->total_faults = p->total_numa_faults;
2005 
2006                 grp->nr_tasks++;
2007                 rcu_assign_pointer(p->numa_group, grp);
2008         }
2009 
2010         rcu_read_lock();
2011         tsk = READ_ONCE(cpu_rq(cpu)->curr);
2012 
2013         if (!cpupid_match_pid(tsk, cpupid))
2014                 goto no_join;
2015 
2016         grp = rcu_dereference(tsk->numa_group);
2017         if (!grp)
2018                 goto no_join;
2019 
2020         my_grp = p->numa_group;
2021         if (grp == my_grp)
2022                 goto no_join;
2023 
2024         /*
2025          * Only join the other group if its bigger; if we're the bigger group,
2026          * the other task will join us.
2027          */
2028         if (my_grp->nr_tasks > grp->nr_tasks)
2029                 goto no_join;
2030 
2031         /*
2032          * Tie-break on the grp address.
2033          */
2034         if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2035                 goto no_join;
2036 
2037         /* Always join threads in the same process. */
2038         if (tsk->mm == current->mm)
2039                 join = true;
2040 
2041         /* Simple filter to avoid false positives due to PID collisions */
2042         if (flags & TNF_SHARED)
2043                 join = true;
2044 
2045         /* Update priv based on whether false sharing was detected */
2046         *priv = !join;
2047 
2048         if (join && !get_numa_group(grp))
2049                 goto no_join;
2050 
2051         rcu_read_unlock();
2052 
2053         if (!join)
2054                 return;
2055 
2056         BUG_ON(irqs_disabled());
2057         double_lock_irq(&my_grp->lock, &grp->lock);
2058 
2059         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2060                 my_grp->faults[i] -= p->numa_faults[i];
2061                 grp->faults[i] += p->numa_faults[i];
2062         }
2063         my_grp->total_faults -= p->total_numa_faults;
2064         grp->total_faults += p->total_numa_faults;
2065 
2066         my_grp->nr_tasks--;
2067         grp->nr_tasks++;
2068 
2069         spin_unlock(&my_grp->lock);
2070         spin_unlock_irq(&grp->lock);
2071 
2072         rcu_assign_pointer(p->numa_group, grp);
2073 
2074         put_numa_group(my_grp);
2075         return;
2076 
2077 no_join:
2078         rcu_read_unlock();
2079         return;
2080 }
2081 
2082 void task_numa_free(struct task_struct *p)
2083 {
2084         struct numa_group *grp = p->numa_group;
2085         void *numa_faults = p->numa_faults;
2086         unsigned long flags;
2087         int i;
2088 
2089         if (grp) {
2090                 spin_lock_irqsave(&grp->lock, flags);
2091                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2092                         grp->faults[i] -= p->numa_faults[i];
2093                 grp->total_faults -= p->total_numa_faults;
2094 
2095                 grp->nr_tasks--;
2096                 spin_unlock_irqrestore(&grp->lock, flags);
2097                 RCU_INIT_POINTER(p->numa_group, NULL);
2098                 put_numa_group(grp);
2099         }
2100 
2101         p->numa_faults = NULL;
2102         kfree(numa_faults);
2103 }
2104 
2105 /*
2106  * Got a PROT_NONE fault for a page on @node.
2107  */
2108 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2109 {
2110         struct task_struct *p = current;
2111         bool migrated = flags & TNF_MIGRATED;
2112         int cpu_node = task_node(current);
2113         int local = !!(flags & TNF_FAULT_LOCAL);
2114         int priv;
2115 
2116         if (!static_branch_likely(&sched_numa_balancing))
2117                 return;
2118 
2119         /* for example, ksmd faulting in a user's mm */
2120         if (!p->mm)
2121                 return;
2122 
2123         /* Allocate buffer to track faults on a per-node basis */
2124         if (unlikely(!p->numa_faults)) {
2125                 int size = sizeof(*p->numa_faults) *
2126                            NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2127 
2128                 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2129                 if (!p->numa_faults)
2130                         return;
2131 
2132                 p->total_numa_faults = 0;
2133                 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2134         }
2135 
2136         /*
2137          * First accesses are treated as private, otherwise consider accesses
2138          * to be private if the accessing pid has not changed
2139          */
2140         if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2141                 priv = 1;
2142         } else {
2143                 priv = cpupid_match_pid(p, last_cpupid);
2144                 if (!priv && !(flags & TNF_NO_GROUP))
2145                         task_numa_group(p, last_cpupid, flags, &priv);
2146         }
2147 
2148         /*
2149          * If a workload spans multiple NUMA nodes, a shared fault that
2150          * occurs wholly within the set of nodes that the workload is
2151          * actively using should be counted as local. This allows the
2152          * scan rate to slow down when a workload has settled down.
2153          */
2154         if (!priv && !local && p->numa_group &&
2155                         node_isset(cpu_node, p->numa_group->active_nodes) &&
2156                         node_isset(mem_node, p->numa_group->active_nodes))
2157                 local = 1;
2158 
2159         task_numa_placement(p);
2160 
2161         /*
2162          * Retry task to preferred node migration periodically, in case it
2163          * case it previously failed, or the scheduler moved us.
2164          */
2165         if (time_after(jiffies, p->numa_migrate_retry))
2166                 numa_migrate_preferred(p);
2167 
2168         if (migrated)
2169                 p->numa_pages_migrated += pages;
2170         if (flags & TNF_MIGRATE_FAIL)
2171                 p->numa_faults_locality[2] += pages;
2172 
2173         p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2174         p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2175         p->numa_faults_locality[local] += pages;
2176 }
2177 
2178 static void reset_ptenuma_scan(struct task_struct *p)
2179 {
2180         /*
2181          * We only did a read acquisition of the mmap sem, so
2182          * p->mm->numa_scan_seq is written to without exclusive access
2183          * and the update is not guaranteed to be atomic. That's not
2184          * much of an issue though, since this is just used for
2185          * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2186          * expensive, to avoid any form of compiler optimizations:
2187          */
2188         WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2189         p->mm->numa_scan_offset = 0;
2190 }
2191 
2192 /*
2193  * The expensive part of numa migration is done from task_work context.
2194  * Triggered from task_tick_numa().
2195  */
2196 void task_numa_work(struct callback_head *work)
2197 {
2198         unsigned long migrate, next_scan, now = jiffies;
2199         struct task_struct *p = current;
2200         struct mm_struct *mm = p->mm;
2201         u64 runtime = p->se.sum_exec_runtime;
2202         struct vm_area_struct *vma;
2203         unsigned long start, end;
2204         unsigned long nr_pte_updates = 0;
2205         long pages, virtpages;
2206 
2207         WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2208 
2209         work->next = work; /* protect against double add */
2210         /*
2211          * Who cares about NUMA placement when they're dying.
2212          *
2213          * NOTE: make sure not to dereference p->mm before this check,
2214          * exit_task_work() happens _after_ exit_mm() so we could be called
2215          * without p->mm even though we still had it when we enqueued this
2216          * work.
2217          */
2218         if (p->flags & PF_EXITING)
2219                 return;
2220 
2221         if (!mm->numa_next_scan) {
2222                 mm->numa_next_scan = now +
2223                         msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2224         }
2225 
2226         /*
2227          * Enforce maximal scan/migration frequency..
2228          */
2229         migrate = mm->numa_next_scan;
2230         if (time_before(now, migrate))
2231                 return;
2232 
2233         if (p->numa_scan_period == 0) {
2234                 p->numa_scan_period_max = task_scan_max(p);
2235                 p->numa_scan_period = task_scan_min(p);
2236         }
2237 
2238         next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2239         if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2240                 return;
2241 
2242         /*
2243          * Delay this task enough that another task of this mm will likely win
2244          * the next time around.
2245          */
2246         p->node_stamp += 2 * TICK_NSEC;
2247 
2248         start = mm->numa_scan_offset;
2249         pages = sysctl_numa_balancing_scan_size;
2250         pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2251         virtpages = pages * 8;     /* Scan up to this much virtual space */
2252         if (!pages)
2253                 return;
2254 
2255 
2256         down_read(&mm->mmap_sem);
2257         vma = find_vma(mm, start);
2258         if (!vma) {
2259                 reset_ptenuma_scan(p);
2260                 start = 0;
2261                 vma = mm->mmap;
2262         }
2263         for (; vma; vma = vma->vm_next) {
2264                 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2265                         is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2266                         continue;
2267                 }
2268 
2269                 /*
2270                  * Shared library pages mapped by multiple processes are not
2271                  * migrated as it is expected they are cache replicated. Avoid
2272                  * hinting faults in read-only file-backed mappings or the vdso
2273                  * as migrating the pages will be of marginal benefit.
2274                  */
2275                 if (!vma->vm_mm ||
2276                     (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2277                         continue;
2278 
2279                 /*
2280                  * Skip inaccessible VMAs to avoid any confusion between
2281                  * PROT_NONE and NUMA hinting ptes
2282                  */
2283                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2284                         continue;
2285 
2286                 do {
2287                         start = max(start, vma->vm_start);
2288                         end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2289                         end = min(end, vma->vm_end);
2290                         nr_pte_updates = change_prot_numa(vma, start, end);
2291 
2292                         /*
2293                          * Try to scan sysctl_numa_balancing_size worth of
2294                          * hpages that have at least one present PTE that
2295                          * is not already pte-numa. If the VMA contains
2296                          * areas that are unused or already full of prot_numa
2297                          * PTEs, scan up to virtpages, to skip through those
2298                          * areas faster.
2299                          */
2300                         if (nr_pte_updates)
2301                                 pages -= (end - start) >> PAGE_SHIFT;
2302                         virtpages -= (end - start) >> PAGE_SHIFT;
2303 
2304                         start = end;
2305                         if (pages <= 0 || virtpages <= 0)
2306                                 goto out;
2307 
2308                         cond_resched();
2309                 } while (end != vma->vm_end);
2310         }
2311 
2312 out:
2313         /*
2314          * It is possible to reach the end of the VMA list but the last few
2315          * VMAs are not guaranteed to the vma_migratable. If they are not, we
2316          * would find the !migratable VMA on the next scan but not reset the
2317          * scanner to the start so check it now.
2318          */
2319         if (vma)
2320                 mm->numa_scan_offset = start;
2321         else
2322                 reset_ptenuma_scan(p);
2323         up_read(&mm->mmap_sem);
2324 
2325         /*
2326          * Make sure tasks use at least 32x as much time to run other code
2327          * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2328          * Usually update_task_scan_period slows down scanning enough; on an
2329          * overloaded system we need to limit overhead on a per task basis.
2330          */
2331         if (unlikely(p->se.sum_exec_runtime != runtime)) {
2332                 u64 diff = p->se.sum_exec_runtime - runtime;
2333                 p->node_stamp += 32 * diff;
2334         }
2335 }
2336 
2337 /*
2338  * Drive the periodic memory faults..
2339  */
2340 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2341 {
2342         struct callback_head *work = &curr->numa_work;
2343         u64 period, now;
2344 
2345         /*
2346          * We don't care about NUMA placement if we don't have memory.
2347          */
2348         if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2349                 return;
2350 
2351         /*
2352          * Using runtime rather than walltime has the dual advantage that
2353          * we (mostly) drive the selection from busy threads and that the
2354          * task needs to have done some actual work before we bother with
2355          * NUMA placement.
2356          */
2357         now = curr->se.sum_exec_runtime;
2358         period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2359 
2360         if (now > curr->node_stamp + period) {
2361                 if (!curr->node_stamp)
2362                         curr->numa_scan_period = task_scan_min(curr);
2363                 curr->node_stamp += period;
2364 
2365                 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2366                         init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2367                         task_work_add(curr, work, true);
2368                 }
2369         }
2370 }
2371 #else
2372 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2373 {
2374 }
2375 
2376 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2377 {
2378 }
2379 
2380 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2381 {
2382 }
2383 #endif /* CONFIG_NUMA_BALANCING */
2384 
2385 static void
2386 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2387 {
2388         update_load_add(&cfs_rq->load, se->load.weight);
2389         if (!parent_entity(se))
2390                 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2391 #ifdef CONFIG_SMP
2392         if (entity_is_task(se)) {
2393                 struct rq *rq = rq_of(cfs_rq);
2394 
2395                 account_numa_enqueue(rq, task_of(se));
2396                 list_add(&se->group_node, &rq->cfs_tasks);
2397         }
2398 #endif
2399         cfs_rq->nr_running++;
2400 }
2401 
2402 static void
2403 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2404 {
2405         update_load_sub(&cfs_rq->load, se->load.weight);
2406         if (!parent_entity(se))
2407                 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2408         if (entity_is_task(se)) {
2409                 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2410                 list_del_init(&se->group_node);
2411         }
2412         cfs_rq->nr_running--;
2413 }
2414 
2415 #ifdef CONFIG_FAIR_GROUP_SCHED
2416 # ifdef CONFIG_SMP
2417 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2418 {
2419         long tg_weight;
2420 
2421         /*
2422          * Use this CPU's real-time load instead of the last load contribution
2423          * as the updating of the contribution is delayed, and we will use the
2424          * the real-time load to calc the share. See update_tg_load_avg().
2425          */
2426         tg_weight = atomic_long_read(&tg->load_avg);
2427         tg_weight -= cfs_rq->tg_load_avg_contrib;
2428         tg_weight += cfs_rq->load.weight;
2429 
2430         return tg_weight;
2431 }
2432 
2433 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2434 {
2435         long tg_weight, load, shares;
2436 
2437         tg_weight = calc_tg_weight(tg, cfs_rq);
2438         load = cfs_rq->load.weight;
2439 
2440         shares = (tg->shares * load);
2441         if (tg_weight)
2442                 shares /= tg_weight;
2443 
2444         if (shares < MIN_SHARES)
2445                 shares = MIN_SHARES;
2446         if (shares > tg->shares)
2447                 shares = tg->shares;
2448 
2449         return shares;
2450 }
2451 # else /* CONFIG_SMP */
2452 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2453 {
2454         return tg->shares;
2455 }
2456 # endif /* CONFIG_SMP */
2457 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2458                             unsigned long weight)
2459 {
2460         if (se->on_rq) {
2461                 /* commit outstanding execution time */
2462                 if (cfs_rq->curr == se)
2463                         update_curr(cfs_rq);
2464                 account_entity_dequeue(cfs_rq, se);
2465         }
2466 
2467         update_load_set(&se->load, weight);
2468 
2469         if (se->on_rq)
2470                 account_entity_enqueue(cfs_rq, se);
2471 }
2472 
2473 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2474 
2475 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2476 {
2477         struct task_group *tg;
2478         struct sched_entity *se;
2479         long shares;
2480 
2481         tg = cfs_rq->tg;
2482         se = tg->se[cpu_of(rq_of(cfs_rq))];
2483         if (!se || throttled_hierarchy(cfs_rq))
2484                 return;
2485 #ifndef CONFIG_SMP
2486         if (likely(se->load.weight == tg->shares))
2487                 return;
2488 #endif
2489         shares = calc_cfs_shares(cfs_rq, tg);
2490 
2491         reweight_entity(cfs_rq_of(se), se, shares);
2492 }
2493 #else /* CONFIG_FAIR_GROUP_SCHED */
2494 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2495 {
2496 }
2497 #endif /* CONFIG_FAIR_GROUP_SCHED */
2498 
2499 #ifdef CONFIG_SMP
2500 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2501 static const u32 runnable_avg_yN_inv[] = {
2502         0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2503         0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2504         0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2505         0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2506         0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2507         0x85aac367, 0x82cd8698,
2508 };
2509 
2510 /*
2511  * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
2512  * over-estimates when re-combining.
2513  */
2514 static const u32 runnable_avg_yN_sum[] = {
2515             0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2516          9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2517         17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2518 };
2519 
2520 /*
2521  * Approximate:
2522  *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
2523  */
2524 static __always_inline u64 decay_load(u64 val, u64 n)
2525 {
2526         unsigned int local_n;
2527 
2528         if (!n)
2529                 return val;
2530         else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2531                 return 0;
2532 
2533         /* after bounds checking we can collapse to 32-bit */
2534         local_n = n;
2535 
2536         /*
2537          * As y^PERIOD = 1/2, we can combine
2538          *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2539          * With a look-up table which covers y^n (n<PERIOD)
2540          *
2541          * To achieve constant time decay_load.
2542          */
2543         if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2544                 val >>= local_n / LOAD_AVG_PERIOD;
2545                 local_n %= LOAD_AVG_PERIOD;
2546         }
2547 
2548         val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2549         return val;
2550 }
2551 
2552 /*
2553  * For updates fully spanning n periods, the contribution to runnable
2554  * average will be: \Sum 1024*y^n
2555  *
2556  * We can compute this reasonably efficiently by combining:
2557  *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
2558  */
2559 static u32 __compute_runnable_contrib(u64 n)
2560 {
2561         u32 contrib = 0;
2562 
2563         if (likely(n <= LOAD_AVG_PERIOD))
2564                 return runnable_avg_yN_sum[n];
2565         else if (unlikely(n >= LOAD_AVG_MAX_N))
2566                 return LOAD_AVG_MAX;
2567 
2568         /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2569         do {
2570                 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2571                 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2572 
2573                 n -= LOAD_AVG_PERIOD;
2574         } while (n > LOAD_AVG_PERIOD);
2575 
2576         contrib = decay_load(contrib, n);
2577         return contrib + runnable_avg_yN_sum[n];
2578 }
2579 
2580 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2581 #error "load tracking assumes 2^10 as unit"
2582 #endif
2583 
2584 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2585 
2586 /*
2587  * We can represent the historical contribution to runnable average as the
2588  * coefficients of a geometric series.  To do this we sub-divide our runnable
2589  * history into segments of approximately 1ms (1024us); label the segment that
2590  * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2591  *
2592  * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2593  *      p0            p1           p2
2594  *     (now)       (~1ms ago)  (~2ms ago)
2595  *
2596  * Let u_i denote the fraction of p_i that the entity was runnable.
2597  *
2598  * We then designate the fractions u_i as our co-efficients, yielding the
2599  * following representation of historical load:
2600  *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2601  *
2602  * We choose y based on the with of a reasonably scheduling period, fixing:
2603  *   y^32 = 0.5
2604  *
2605  * This means that the contribution to load ~32ms ago (u_32) will be weighted
2606  * approximately half as much as the contribution to load within the last ms
2607  * (u_0).
2608  *
2609  * When a period "rolls over" and we have new u_0`, multiplying the previous
2610  * sum again by y is sufficient to update:
2611  *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2612  *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2613  */
2614 static __always_inline int
2615 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2616                   unsigned long weight, int running, struct cfs_rq *cfs_rq)
2617 {
2618         u64 delta, scaled_delta, periods;
2619         u32 contrib;
2620         unsigned int delta_w, scaled_delta_w, decayed = 0;
2621         unsigned long scale_freq, scale_cpu;
2622 
2623         delta = now - sa->last_update_time;
2624         /*
2625          * This should only happen when time goes backwards, which it
2626          * unfortunately does during sched clock init when we swap over to TSC.
2627          */
2628         if ((s64)delta < 0) {
2629                 sa->last_update_time = now;
2630                 return 0;
2631         }
2632 
2633         /*
2634          * Use 1024ns as the unit of measurement since it's a reasonable
2635          * approximation of 1us and fast to compute.
2636          */
2637         delta >>= 10;
2638         if (!delta)
2639                 return 0;
2640         sa->last_update_time = now;
2641 
2642         scale_freq = arch_scale_freq_capacity(NULL, cpu);
2643         scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2644 
2645         /* delta_w is the amount already accumulated against our next period */
2646         delta_w = sa->period_contrib;
2647         if (delta + delta_w >= 1024) {
2648                 decayed = 1;
2649 
2650                 /* how much left for next period will start over, we don't know yet */
2651                 sa->period_contrib = 0;
2652 
2653                 /*
2654                  * Now that we know we're crossing a period boundary, figure
2655                  * out how much from delta we need to complete the current
2656                  * period and accrue it.
2657                  */
2658                 delta_w = 1024 - delta_w;
2659                 scaled_delta_w = cap_scale(delta_w, scale_freq);
2660                 if (weight) {
2661                         sa->load_sum += weight * scaled_delta_w;
2662                         if (cfs_rq) {
2663                                 cfs_rq->runnable_load_sum +=
2664                                                 weight * scaled_delta_w;
2665                         }
2666                 }
2667                 if (running)
2668                         sa->util_sum += scaled_delta_w * scale_cpu;
2669 
2670                 delta -= delta_w;
2671 
2672                 /* Figure out how many additional periods this update spans */
2673                 periods = delta / 1024;
2674                 delta %= 1024;
2675 
2676                 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2677                 if (cfs_rq) {
2678                         cfs_rq->runnable_load_sum =
2679                                 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2680                 }
2681                 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2682 
2683                 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2684                 contrib = __compute_runnable_contrib(periods);
2685                 contrib = cap_scale(contrib, scale_freq);
2686                 if (weight) {
2687                         sa->load_sum += weight * contrib;
2688                         if (cfs_rq)
2689                                 cfs_rq->runnable_load_sum += weight * contrib;
2690                 }
2691                 if (running)
2692                         sa->util_sum += contrib * scale_cpu;
2693         }
2694 
2695         /* Remainder of delta accrued against u_0` */
2696         scaled_delta = cap_scale(delta, scale_freq);
2697         if (weight) {
2698                 sa->load_sum += weight * scaled_delta;
2699                 if (cfs_rq)
2700                         cfs_rq->runnable_load_sum += weight * scaled_delta;
2701         }
2702         if (running)
2703                 sa->util_sum += scaled_delta * scale_cpu;
2704 
2705         sa->period_contrib += delta;
2706 
2707         if (decayed) {
2708                 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2709                 if (cfs_rq) {
2710                         cfs_rq->runnable_load_avg =
2711                                 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2712                 }
2713                 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2714         }
2715 
2716         return decayed;
2717 }
2718 
2719 #ifdef CONFIG_FAIR_GROUP_SCHED
2720 /*
2721  * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2722  * and effective_load (which is not done because it is too costly).
2723  */
2724 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2725 {
2726         long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2727 
2728         /*
2729          * No need to update load_avg for root_task_group as it is not used.
2730          */
2731         if (cfs_rq->tg == &root_task_group)
2732                 return;
2733 
2734         if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2735                 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2736                 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2737         }
2738 }
2739 
2740 /*
2741  * Called within set_task_rq() right before setting a task's cpu. The
2742  * caller only guarantees p->pi_lock is held; no other assumptions,
2743  * including the state of rq->lock, should be made.
2744  */
2745 void set_task_rq_fair(struct sched_entity *se,
2746                       struct cfs_rq *prev, struct cfs_rq *next)
2747 {
2748         if (!sched_feat(ATTACH_AGE_LOAD))
2749                 return;
2750 
2751         /*
2752          * We are supposed to update the task to "current" time, then its up to
2753          * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2754          * getting what current time is, so simply throw away the out-of-date
2755          * time. This will result in the wakee task is less decayed, but giving
2756          * the wakee more load sounds not bad.
2757          */
2758         if (se->avg.last_update_time && prev) {
2759                 u64 p_last_update_time;
2760                 u64 n_last_update_time;
2761 
2762 #ifndef CONFIG_64BIT
2763                 u64 p_last_update_time_copy;
2764                 u64 n_last_update_time_copy;
2765 
2766                 do {
2767                         p_last_update_time_copy = prev->load_last_update_time_copy;
2768                         n_last_update_time_copy = next->load_last_update_time_copy;
2769 
2770                         smp_rmb();
2771 
2772                         p_last_update_time = prev->avg.last_update_time;
2773                         n_last_update_time = next->avg.last_update_time;
2774 
2775                 } while (p_last_update_time != p_last_update_time_copy ||
2776                          n_last_update_time != n_last_update_time_copy);
2777 #else
2778                 p_last_update_time = prev->avg.last_update_time;
2779                 n_last_update_time = next->avg.last_update_time;
2780 #endif
2781                 __update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
2782                                   &se->avg, 0, 0, NULL);
2783                 se->avg.last_update_time = n_last_update_time;
2784         }
2785 }
2786 #else /* CONFIG_FAIR_GROUP_SCHED */
2787 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2788 #endif /* CONFIG_FAIR_GROUP_SCHED */
2789 
2790 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2791 
2792 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2793 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2794 {
2795         struct sched_avg *sa = &cfs_rq->avg;
2796         int decayed, removed = 0;
2797 
2798         if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2799                 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2800                 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2801                 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2802                 removed = 1;
2803         }
2804 
2805         if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2806                 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2807                 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2808                 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2809         }
2810 
2811         decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2812                 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2813 
2814 #ifndef CONFIG_64BIT
2815         smp_wmb();
2816         cfs_rq->load_last_update_time_copy = sa->last_update_time;
2817 #endif
2818 
2819         return decayed || removed;
2820 }
2821 
2822 /* Update task and its cfs_rq load average */
2823 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2824 {
2825         struct cfs_rq *cfs_rq = cfs_rq_of(se);
2826         u64 now = cfs_rq_clock_task(cfs_rq);
2827         int cpu = cpu_of(rq_of(cfs_rq));
2828 
2829         /*
2830          * Track task load average for carrying it to new CPU after migrated, and
2831          * track group sched_entity load average for task_h_load calc in migration
2832          */
2833         __update_load_avg(now, cpu, &se->avg,
2834                           se->on_rq * scale_load_down(se->load.weight),
2835                           cfs_rq->curr == se, NULL);
2836 
2837         if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2838                 update_tg_load_avg(cfs_rq, 0);
2839 }
2840 
2841 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2842 {
2843         if (!sched_feat(ATTACH_AGE_LOAD))
2844                 goto skip_aging;
2845 
2846         /*
2847          * If we got migrated (either between CPUs or between cgroups) we'll
2848          * have aged the average right before clearing @last_update_time.
2849          */
2850         if (se->avg.last_update_time) {
2851                 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2852                                   &se->avg, 0, 0, NULL);
2853 
2854                 /*
2855                  * XXX: we could have just aged the entire load away if we've been
2856                  * absent from the fair class for too long.
2857                  */
2858         }
2859 
2860 skip_aging:
2861         se->avg.last_update_time = cfs_rq->avg.last_update_time;
2862         cfs_rq->avg.load_avg += se->avg.load_avg;
2863         cfs_rq->avg.load_sum += se->avg.load_sum;
2864         cfs_rq->avg.util_avg += se->avg.util_avg;
2865         cfs_rq->avg.util_sum += se->avg.util_sum;
2866 }
2867 
2868 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2869 {
2870         __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2871                           &se->avg, se->on_rq * scale_load_down(se->load.weight),
2872                           cfs_rq->curr == se, NULL);
2873 
2874         cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2875         cfs_rq->avg.load_sum = max_t(s64,  cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2876         cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2877         cfs_rq->avg.util_sum = max_t(s32,  cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2878 }
2879 
2880 /* Add the load generated by se into cfs_rq's load average */
2881 static inline void
2882 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2883 {
2884         struct sched_avg *sa = &se->avg;
2885         u64 now = cfs_rq_clock_task(cfs_rq);
2886         int migrated, decayed;
2887 
2888         migrated = !sa->last_update_time;
2889         if (!migrated) {
2890                 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2891                         se->on_rq * scale_load_down(se->load.weight),
2892                         cfs_rq->curr == se, NULL);
2893         }
2894 
2895         decayed = update_cfs_rq_load_avg(now, cfs_rq);
2896 
2897         cfs_rq->runnable_load_avg += sa->load_avg;
2898         cfs_rq->runnable_load_sum += sa->load_sum;
2899 
2900         if (migrated)
2901                 attach_entity_load_avg(cfs_rq, se);
2902 
2903         if (decayed || migrated)
2904                 update_tg_load_avg(cfs_rq, 0);
2905 }
2906 
2907 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2908 static inline void
2909 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2910 {
2911         update_load_avg(se, 1);
2912 
2913         cfs_rq->runnable_load_avg =
2914                 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2915         cfs_rq->runnable_load_sum =
2916                 max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2917 }
2918 
2919 #ifndef CONFIG_64BIT
2920 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2921 {
2922         u64 last_update_time_copy;
2923         u64 last_update_time;
2924 
2925         do {
2926                 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2927                 smp_rmb();
2928                 last_update_time = cfs_rq->avg.last_update_time;
2929         } while (last_update_time != last_update_time_copy);
2930 
2931         return last_update_time;
2932 }
2933 #else
2934 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2935 {
2936         return cfs_rq->avg.last_update_time;
2937 }
2938 #endif
2939 
2940 /*
2941  * Task first catches up with cfs_rq, and then subtract
2942  * itself from the cfs_rq (task must be off the queue now).
2943  */
2944 void remove_entity_load_avg(struct sched_entity *se)
2945 {
2946         struct cfs_rq *cfs_rq = cfs_rq_of(se);
2947         u64 last_update_time;
2948 
2949         /*
2950          * Newly created task or never used group entity should not be removed
2951          * from its (source) cfs_rq
2952          */
2953         if (se->avg.last_update_time == 0)
2954                 return;
2955 
2956         last_update_time = cfs_rq_last_update_time(cfs_rq);
2957 
2958         __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2959         atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2960         atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2961 }
2962 
2963 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2964 {
2965         return cfs_rq->runnable_load_avg;
2966 }
2967 
2968 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2969 {
2970         return cfs_rq->avg.load_avg;
2971 }
2972 
2973 static int idle_balance(struct rq *this_rq);
2974 
2975 #else /* CONFIG_SMP */
2976 
2977 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2978 static inline void
2979 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2980 static inline void
2981 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2982 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2983 
2984 static inline void
2985 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2986 static inline void
2987 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2988 
2989 static inline int idle_balance(struct rq *rq)
2990 {
2991         return 0;
2992 }
2993 
2994 #endif /* CONFIG_SMP */
2995 
2996 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2997 {
2998 #ifdef CONFIG_SCHEDSTATS
2999         struct task_struct *tsk = NULL;
3000 
3001         if (entity_is_task(se))
3002                 tsk = task_of(se);
3003 
3004         if (se->statistics.sleep_start) {
3005                 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3006 
3007                 if ((s64)delta < 0)
3008                         delta = 0;
3009 
3010                 if (unlikely(delta > se->statistics.sleep_max))
3011                         se->statistics.sleep_max = delta;
3012 
3013                 se->statistics.sleep_start = 0;
3014                 se->statistics.sum_sleep_runtime += delta;
3015 
3016                 if (tsk) {
3017                         account_scheduler_latency(tsk, delta >> 10, 1);
3018                         trace_sched_stat_sleep(tsk, delta);
3019                 }
3020         }
3021         if (se->statistics.block_start) {
3022                 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3023 
3024                 if ((s64)delta < 0)
3025                         delta = 0;
3026 
3027                 if (unlikely(delta > se->statistics.block_max))
3028                         se->statistics.block_max = delta;
3029 
3030                 se->statistics.block_start = 0;
3031                 se->statistics.sum_sleep_runtime += delta;
3032 
3033                 if (tsk) {
3034                         if (tsk->in_iowait) {
3035                                 se->statistics.iowait_sum += delta;
3036                                 se->statistics.iowait_count++;
3037                                 trace_sched_stat_iowait(tsk, delta);
3038                         }
3039 
3040                         trace_sched_stat_blocked(tsk, delta);
3041 
3042                         /*
3043                          * Blocking time is in units of nanosecs, so shift by
3044                          * 20 to get a milliseconds-range estimation of the
3045                          * amount of time that the task spent sleeping:
3046                          */
3047                         if (unlikely(prof_on == SLEEP_PROFILING)) {
3048                                 profile_hits(SLEEP_PROFILING,
3049                                                 (void *)get_wchan(tsk),
3050                                                 delta >> 20);
3051                         }
3052                         account_scheduler_latency(tsk, delta >> 10, 0);
3053                 }
3054         }
3055 #endif
3056 }
3057 
3058 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
3059 {
3060 #ifdef CONFIG_SCHED_DEBUG
3061         s64 d = se->vruntime - cfs_rq->min_vruntime;
3062 
3063         if (d < 0)
3064                 d = -d;
3065 
3066         if (d > 3*sysctl_sched_latency)
3067                 schedstat_inc(cfs_rq, nr_spread_over);
3068 #endif
3069 }
3070 
3071 static void
3072 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3073 {
3074         u64 vruntime = cfs_rq->min_vruntime;
3075 
3076         /*
3077          * The 'current' period is already promised to the current tasks,
3078          * however the extra weight of the new task will slow them down a
3079          * little, place the new task so that it fits in the slot that
3080          * stays open at the end.
3081          */
3082         if (initial && sched_feat(START_DEBIT))
3083                 vruntime += sched_vslice(cfs_rq, se);
3084 
3085         /* sleeps up to a single latency don't count. */
3086         if (!initial) {
3087                 unsigned long thresh = sysctl_sched_latency;
3088 
3089                 /*
3090                  * Halve their sleep time's effect, to allow
3091                  * for a gentler effect of sleepers:
3092                  */
3093                 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3094                         thresh >>= 1;
3095 
3096                 vruntime -= thresh;
3097         }
3098 
3099         /* ensure we never gain time by being placed backwards. */
3100         se->vruntime = max_vruntime(se->vruntime, vruntime);
3101 }
3102 
3103 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3104 
3105 static void
3106 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3107 {
3108         /*
3109          * Update the normalized vruntime before updating min_vruntime
3110          * through calling update_curr().
3111          */
3112         if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3113                 se->vruntime += cfs_rq->min_vruntime;
3114 
3115         /*
3116          * Update run-time statistics of the 'current'.
3117          */
3118         update_curr(cfs_rq);
3119         enqueue_entity_load_avg(cfs_rq, se);
3120         account_entity_enqueue(cfs_rq, se);
3121         update_cfs_shares(cfs_rq);
3122 
3123         if (flags & ENQUEUE_WAKEUP) {
3124                 place_entity(cfs_rq, se, 0);
3125                 enqueue_sleeper(cfs_rq, se);
3126         }
3127 
3128         update_stats_enqueue(cfs_rq, se);
3129         check_spread(cfs_rq, se);
3130         if (se != cfs_rq->curr)
3131                 __enqueue_entity(cfs_rq, se);
3132         se->on_rq = 1;
3133 
3134         if (cfs_rq->nr_running == 1) {
3135                 list_add_leaf_cfs_rq(cfs_rq);
3136                 check_enqueue_throttle(cfs_rq);
3137         }
3138 }
3139 
3140 static void __clear_buddies_last(struct sched_entity *se)
3141 {
3142         for_each_sched_entity(se) {
3143                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3144                 if (cfs_rq->last != se)
3145                         break;
3146 
3147                 cfs_rq->last = NULL;
3148         }
3149 }
3150 
3151 static void __clear_buddies_next(struct sched_entity *se)
3152 {
3153         for_each_sched_entity(se) {
3154                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3155                 if (cfs_rq->next != se)
3156                         break;
3157 
3158                 cfs_rq->next = NULL;
3159         }
3160 }
3161 
3162 static void __clear_buddies_skip(struct sched_entity *se)
3163 {
3164         for_each_sched_entity(se) {
3165                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3166                 if (cfs_rq->skip != se)
3167                         break;
3168 
3169                 cfs_rq->skip = NULL;
3170         }
3171 }
3172 
3173 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3174 {
3175         if (cfs_rq->last == se)
3176                 __clear_buddies_last(se);
3177 
3178         if (cfs_rq->next == se)
3179                 __clear_buddies_next(se);
3180 
3181         if (cfs_rq->skip == se)
3182                 __clear_buddies_skip(se);
3183 }
3184 
3185 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3186 
3187 static void
3188 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3189 {
3190         /*
3191          * Update run-time statistics of the 'current'.
3192          */
3193         update_curr(cfs_rq);
3194         dequeue_entity_load_avg(cfs_rq, se);
3195 
3196         update_stats_dequeue(cfs_rq, se);
3197         if (flags & DEQUEUE_SLEEP) {
3198 #ifdef CONFIG_SCHEDSTATS
3199                 if (entity_is_task(se)) {
3200                         struct task_struct *tsk = task_of(se);
3201 
3202                         if (tsk->state & TASK_INTERRUPTIBLE)
3203                                 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3204                         if (tsk->state & TASK_UNINTERRUPTIBLE)
3205                                 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3206                 }
3207 #endif
3208         }
3209 
3210         clear_buddies(cfs_rq, se);
3211 
3212         if (se != cfs_rq->curr)
3213                 __dequeue_entity(cfs_rq, se);
3214         se->on_rq = 0;
3215         account_entity_dequeue(cfs_rq, se);
3216 
3217         /*
3218          * Normalize the entity after updating the min_vruntime because the
3219          * update can refer to the ->curr item and we need to reflect this
3220          * movement in our normalized position.
3221          */
3222         if (!(flags & DEQUEUE_SLEEP))
3223                 se->vruntime -= cfs_rq->min_vruntime;
3224 
3225         /* return excess runtime on last dequeue */
3226         return_cfs_rq_runtime(cfs_rq);
3227 
3228         update_min_vruntime(cfs_rq);
3229         update_cfs_shares(cfs_rq);
3230 }
3231 
3232 /*
3233  * Preempt the current task with a newly woken task if needed:
3234  */
3235 static void
3236 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3237 {
3238         unsigned long ideal_runtime, delta_exec;
3239         struct sched_entity *se;
3240         s64 delta;
3241 
3242         ideal_runtime = sched_slice(cfs_rq, curr);
3243         delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3244         if (delta_exec > ideal_runtime) {
3245                 resched_curr(rq_of(cfs_rq));
3246                 /*
3247                  * The current task ran long enough, ensure it doesn't get
3248                  * re-elected due to buddy favours.
3249                  */
3250                 clear_buddies(cfs_rq, curr);
3251                 return;
3252         }
3253 
3254         /*
3255          * Ensure that a task that missed wakeup preemption by a
3256          * narrow margin doesn't have to wait for a full slice.
3257          * This also mitigates buddy induced latencies under load.
3258          */
3259         if (delta_exec < sysctl_sched_min_granularity)
3260                 return;
3261 
3262         se = __pick_first_entity(cfs_rq);
3263         delta = curr->vruntime - se->vruntime;
3264 
3265         if (delta < 0)
3266                 return;
3267 
3268         if (delta > ideal_runtime)
3269                 resched_curr(rq_of(cfs_rq));
3270 }
3271 
3272 static void
3273 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3274 {
3275         /* 'current' is not kept within the tree. */
3276         if (se->on_rq) {
3277                 /*
3278                  * Any task has to be enqueued before it get to execute on
3279                  * a CPU. So account for the time it spent waiting on the
3280                  * runqueue.
3281                  */
3282                 update_stats_wait_end(cfs_rq, se);
3283                 __dequeue_entity(cfs_rq, se);
3284                 update_load_avg(se, 1);
3285         }
3286 
3287         update_stats_curr_start(cfs_rq, se);
3288         cfs_rq->curr = se;
3289 #ifdef CONFIG_SCHEDSTATS
3290         /*
3291          * Track our maximum slice length, if the CPU's load is at
3292          * least twice that of our own weight (i.e. dont track it
3293          * when there are only lesser-weight tasks around):
3294          */
3295         if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3296                 se->statistics.slice_max = max(se->statistics.slice_max,
3297                         se->sum_exec_runtime - se->prev_sum_exec_runtime);
3298         }
3299 #endif
3300         se->prev_sum_exec_runtime = se->sum_exec_runtime;
3301 }
3302 
3303 static int
3304 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3305 
3306 /*
3307  * Pick the next process, keeping these things in mind, in this order:
3308  * 1) keep things fair between processes/task groups
3309  * 2) pick the "next" process, since someone really wants that to run
3310  * 3) pick the "last" process, for cache locality
3311  * 4) do not run the "skip" process, if something else is available
3312  */
3313 static struct sched_entity *
3314 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3315 {
3316         struct sched_entity *left = __pick_first_entity(cfs_rq);
3317         struct sched_entity *se;
3318 
3319         /*
3320          * If curr is set we have to see if its left of the leftmost entity
3321          * still in the tree, provided there was anything in the tree at all.
3322          */
3323         if (!left || (curr && entity_before(curr, left)))
3324                 left = curr;
3325 
3326         se = left; /* ideally we run the leftmost entity */
3327 
3328         /*
3329          * Avoid running the skip buddy, if running something else can
3330          * be done without getting too unfair.
3331          */
3332         if (cfs_rq->skip == se) {
3333                 struct sched_entity *second;
3334 
3335                 if (se == curr) {
3336                         second = __pick_first_entity(cfs_rq);
3337                 } else {
3338                         second = __pick_next_entity(se);
3339                         if (!second || (curr && entity_before(curr, second)))
3340                                 second = curr;
3341                 }
3342 
3343                 if (second && wakeup_preempt_entity(second, left) < 1)
3344                         se = second;
3345         }
3346 
3347         /*
3348          * Prefer last buddy, try to return the CPU to a preempted task.
3349          */
3350         if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3351                 se = cfs_rq->last;
3352 
3353         /*
3354          * Someone really wants this to run. If it's not unfair, run it.
3355          */
3356         if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3357                 se = cfs_rq->next;
3358 
3359         clear_buddies(cfs_rq, se);
3360 
3361         return se;
3362 }
3363 
3364 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3365 
3366 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3367 {
3368         /*
3369          * If still on the runqueue then deactivate_task()
3370          * was not called and update_curr() has to be done:
3371          */
3372         if (prev->on_rq)
3373                 update_curr(cfs_rq);
3374 
3375         /* throttle cfs_rqs exceeding runtime */
3376         check_cfs_rq_runtime(cfs_rq);
3377 
3378         check_spread(cfs_rq, prev);
3379         if (prev->on_rq) {
3380                 update_stats_wait_start(cfs_rq, prev);
3381                 /* Put 'current' back into the tree. */
3382                 __enqueue_entity(cfs_rq, prev);
3383                 /* in !on_rq case, update occurred at dequeue */
3384                 update_load_avg(prev, 0);
3385         }
3386         cfs_rq->curr = NULL;
3387 }
3388 
3389 static void
3390 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3391 {
3392         /*
3393          * Update run-time statistics of the 'current'.
3394          */
3395         update_curr(cfs_rq);
3396 
3397         /*
3398          * Ensure that runnable average is periodically updated.
3399          */
3400         update_load_avg(curr, 1);
3401         update_cfs_shares(cfs_rq);
3402 
3403 #ifdef CONFIG_SCHED_HRTICK
3404         /*
3405          * queued ticks are scheduled to match the slice, so don't bother
3406          * validating it and just reschedule.
3407          */
3408         if (queued) {
3409                 resched_curr(rq_of(cfs_rq));
3410                 return;
3411         }
3412         /*
3413          * don't let the period tick interfere with the hrtick preemption
3414          */
3415         if (!sched_feat(DOUBLE_TICK) &&
3416                         hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3417                 return;
3418 #endif
3419 
3420         if (cfs_rq->nr_running > 1)
3421                 check_preempt_tick(cfs_rq, curr);
3422 }
3423 
3424 
3425 /**************************************************
3426  * CFS bandwidth control machinery
3427  */
3428 
3429 #ifdef CONFIG_CFS_BANDWIDTH
3430 
3431 #ifdef HAVE_JUMP_LABEL
3432 static struct static_key __cfs_bandwidth_used;
3433 
3434 static inline bool cfs_bandwidth_used(void)
3435 {
3436         return static_key_false(&__cfs_bandwidth_used);
3437 }
3438 
3439 void cfs_bandwidth_usage_inc(void)
3440 {
3441         static_key_slow_inc(&__cfs_bandwidth_used);
3442 }
3443 
3444 void cfs_bandwidth_usage_dec(void)
3445 {
3446         static_key_slow_dec(&__cfs_bandwidth_used);
3447 }
3448 #else /* HAVE_JUMP_LABEL */
3449 static bool cfs_bandwidth_used(void)
3450 {
3451         return true;
3452 }
3453 
3454 void cfs_bandwidth_usage_inc(void) {}
3455 void cfs_bandwidth_usage_dec(void) {}
3456 #endif /* HAVE_JUMP_LABEL */
3457 
3458 /*
3459  * default period for cfs group bandwidth.
3460  * default: 0.1s, units: nanoseconds
3461  */
3462 static inline u64 default_cfs_period(void)
3463 {
3464         return 100000000ULL;
3465 }
3466 
3467 static inline u64 sched_cfs_bandwidth_slice(void)
3468 {
3469         return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3470 }
3471 
3472 /*
3473  * Replenish runtime according to assigned quota and update expiration time.
3474  * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3475  * additional synchronization around rq->lock.
3476  *
3477  * requires cfs_b->lock
3478  */
3479 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3480 {
3481         u64 now;
3482 
3483         if (cfs_b->quota == RUNTIME_INF)
3484                 return;
3485 
3486         now = sched_clock_cpu(smp_processor_id());
3487         cfs_b->runtime = cfs_b->quota;
3488         cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3489 }
3490 
3491 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3492 {
3493         return &tg->cfs_bandwidth;
3494 }
3495 
3496 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3497 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3498 {
3499         if (unlikely(cfs_rq->throttle_count))
3500                 return cfs_rq->throttled_clock_task;
3501 
3502         return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3503 }
3504 
3505 /* returns 0 on failure to allocate runtime */
3506 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3507 {
3508         struct task_group *tg = cfs_rq->tg;
3509         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3510         u64 amount = 0, min_amount, expires;
3511 
3512         /* note: this is a positive sum as runtime_remaining <= 0 */
3513         min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3514 
3515         raw_spin_lock(&cfs_b->lock);
3516         if (cfs_b->quota == RUNTIME_INF)
3517                 amount = min_amount;
3518         else {
3519                 start_cfs_bandwidth(cfs_b);
3520 
3521                 if (cfs_b->runtime > 0) {
3522                         amount = min(cfs_b->runtime, min_amount);
3523                         cfs_b->runtime -= amount;
3524                         cfs_b->idle = 0;
3525                 }
3526         }
3527         expires = cfs_b->runtime_expires;
3528         raw_spin_unlock(&cfs_b->lock);
3529 
3530         cfs_rq->runtime_remaining += amount;
3531         /*
3532          * we may have advanced our local expiration to account for allowed
3533          * spread between our sched_clock and the one on which runtime was
3534          * issued.
3535          */
3536         if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3537                 cfs_rq->runtime_expires = expires;
3538 
3539         return cfs_rq->runtime_remaining > 0;
3540 }
3541 
3542 /*
3543  * Note: This depends on the synchronization provided by sched_clock and the
3544  * fact that rq->clock snapshots this value.
3545  */
3546 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3547 {
3548         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3549 
3550         /* if the deadline is ahead of our clock, nothing to do */
3551         if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3552                 return;
3553 
3554         if (cfs_rq->runtime_remaining < 0)
3555                 return;
3556 
3557         /*
3558          * If the local deadline has passed we have to consider the
3559          * possibility that our sched_clock is 'fast' and the global deadline
3560          * has not truly expired.
3561          *
3562          * Fortunately we can check determine whether this the case by checking
3563          * whether the global deadline has advanced. It is valid to compare
3564          * cfs_b->runtime_expires without any locks since we only care about
3565          * exact equality, so a partial write will still work.
3566          */
3567 
3568         if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3569                 /* extend local deadline, drift is bounded above by 2 ticks */
3570                 cfs_rq->runtime_expires += TICK_NSEC;
3571         } else {
3572                 /* global deadline is ahead, expiration has passed */
3573                 cfs_rq->runtime_remaining = 0;
3574         }
3575 }
3576 
3577 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3578 {
3579         /* dock delta_exec before expiring quota (as it could span periods) */
3580         cfs_rq->runtime_remaining -= delta_exec;
3581         expire_cfs_rq_runtime(cfs_rq);
3582 
3583         if (likely(cfs_rq->runtime_remaining > 0))
3584                 return;
3585 
3586         /*
3587          * if we're unable to extend our runtime we resched so that the active
3588          * hierarchy can be throttled
3589          */
3590         if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3591                 resched_curr(rq_of(cfs_rq));
3592 }
3593 
3594 static __always_inline
3595 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3596 {
3597         if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3598                 return;
3599 
3600         __account_cfs_rq_runtime(cfs_rq, delta_exec);
3601 }
3602 
3603 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3604 {
3605         return cfs_bandwidth_used() && cfs_rq->throttled;
3606 }
3607 
3608 /* check whether cfs_rq, or any parent, is throttled */
3609 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3610 {
3611         return cfs_bandwidth_used() && cfs_rq->throttle_count;
3612 }
3613 
3614 /*
3615  * Ensure that neither of the group entities corresponding to src_cpu or
3616  * dest_cpu are members of a throttled hierarchy when performing group
3617  * load-balance operations.
3618  */
3619 static inline int throttled_lb_pair(struct task_group *tg,
3620                                     int src_cpu, int dest_cpu)
3621 {
3622         struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3623 
3624         src_cfs_rq = tg->cfs_rq[src_cpu];
3625         dest_cfs_rq = tg->cfs_rq[dest_cpu];
3626 
3627         return throttled_hierarchy(src_cfs_rq) ||
3628                throttled_hierarchy(dest_cfs_rq);
3629 }
3630 
3631 /* updated child weight may affect parent so we have to do this bottom up */
3632 static int tg_unthrottle_up(struct task_group *tg, void *data)
3633 {
3634         struct rq *rq = data;
3635         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3636 
3637         cfs_rq->throttle_count--;
3638 #ifdef CONFIG_SMP
3639         if (!cfs_rq->throttle_count) {
3640                 /* adjust cfs_rq_clock_task() */
3641                 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3642                                              cfs_rq->throttled_clock_task;
3643         }
3644 #endif
3645 
3646         return 0;
3647 }
3648 
3649 static int tg_throttle_down(struct task_group *tg, void *data)
3650 {
3651         struct rq *rq = data;
3652         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3653 
3654         /* group is entering throttled state, stop time */
3655         if (!cfs_rq->throttle_count)
3656                 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3657         cfs_rq->throttle_count++;
3658 
3659         return 0;
3660 }
3661 
3662 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3663 {
3664         struct rq *rq = rq_of(cfs_rq);
3665         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3666         struct sched_entity *se;
3667         long task_delta, dequeue = 1;
3668         bool empty;
3669 
3670         se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3671 
3672         /* freeze hierarchy runnable averages while throttled */
3673         rcu_read_lock();
3674         walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3675         rcu_read_unlock();
3676 
3677         task_delta = cfs_rq->h_nr_running;
3678         for_each_sched_entity(se) {
3679                 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3680                 /* throttled entity or throttle-on-deactivate */
3681                 if (!se->on_rq)
3682                         break;
3683 
3684                 if (dequeue)
3685                         dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3686                 qcfs_rq->h_nr_running -= task_delta;
3687 
3688                 if (qcfs_rq->load.weight)
3689                         dequeue = 0;
3690         }
3691 
3692         if (!se)
3693                 sub_nr_running(rq, task_delta);
3694 
3695         cfs_rq->throttled = 1;
3696         cfs_rq->throttled_clock = rq_clock(rq);
3697         raw_spin_lock(&cfs_b->lock);
3698         empty = list_empty(&cfs_b->throttled_cfs_rq);
3699 
3700         /*
3701          * Add to the _head_ of the list, so that an already-started
3702          * distribute_cfs_runtime will not see us
3703          */
3704         list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3705 
3706         /*
3707          * If we're the first throttled task, make sure the bandwidth
3708          * timer is running.
3709          */
3710         if (empty)
3711                 start_cfs_bandwidth(cfs_b);
3712 
3713         raw_spin_unlock(&cfs_b->lock);
3714 }
3715 
3716 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3717 {
3718         struct rq *rq = rq_of(cfs_rq);
3719         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3720         struct sched_entity *se;
3721         int enqueue = 1;
3722         long task_delta;
3723 
3724         se = cfs_rq->tg->se[cpu_of(rq)];
3725 
3726         cfs_rq->throttled = 0;
3727 
3728         update_rq_clock(rq);
3729 
3730         raw_spin_lock(&cfs_b->lock);
3731         cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3732         list_del_rcu(&cfs_rq->throttled_list);
3733         raw_spin_unlock(&cfs_b->lock);
3734 
3735         /* update hierarchical throttle state */
3736         walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3737 
3738         if (!cfs_rq->load.weight)
3739                 return;
3740 
3741         task_delta = cfs_rq->h_nr_running;
3742         for_each_sched_entity(se) {
3743                 if (se->on_rq)
3744                         enqueue = 0;
3745 
3746                 cfs_rq = cfs_rq_of(se);
3747                 if (enqueue)
3748                         enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3749                 cfs_rq->h_nr_running += task_delta;
3750 
3751                 if (cfs_rq_throttled(cfs_rq))
3752                         break;
3753         }
3754 
3755         if (!se)
3756                 add_nr_running(rq, task_delta);
3757 
3758         /* determine whether we need to wake up potentially idle cpu */
3759         if (rq->curr == rq->idle && rq->cfs.nr_running)
3760                 resched_curr(rq);
3761 }
3762 
3763 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3764                 u64 remaining, u64 expires)
3765 {
3766         struct cfs_rq *cfs_rq;
3767         u64 runtime;
3768         u64 starting_runtime = remaining;
3769 
3770         rcu_read_lock();
3771         list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3772                                 throttled_list) {
3773                 struct rq *rq = rq_of(cfs_rq);
3774 
3775                 raw_spin_lock(&rq->lock);
3776                 if (!cfs_rq_throttled(cfs_rq))
3777                         goto next;
3778 
3779                 runtime = -cfs_rq->runtime_remaining + 1;
3780                 if (runtime > remaining)
3781                         runtime = remaining;
3782                 remaining -= runtime;
3783 
3784                 cfs_rq->runtime_remaining += runtime;
3785                 cfs_rq->runtime_expires = expires;
3786 
3787                 /* we check whether we're throttled above */
3788                 if (cfs_rq->runtime_remaining > 0)
3789                         unthrottle_cfs_rq(cfs_rq);
3790 
3791 next:
3792                 raw_spin_unlock(&rq->lock);
3793 
3794                 if (!remaining)
3795                         break;
3796         }
3797         rcu_read_unlock();
3798 
3799         return starting_runtime - remaining;
3800 }
3801 
3802 /*
3803  * Responsible for refilling a task_group's bandwidth and unthrottling its
3804  * cfs_rqs as appropriate. If there has been no activity within the last
3805  * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3806  * used to track this state.
3807  */
3808 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3809 {
3810         u64 runtime, runtime_expires;
3811         int throttled;
3812 
3813         /* no need to continue the timer with no bandwidth constraint */
3814         if (cfs_b->quota == RUNTIME_INF)
3815                 goto out_deactivate;
3816 
3817         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3818         cfs_b->nr_periods += overrun;
3819 
3820         /*
3821          * idle depends on !throttled (for the case of a large deficit), and if
3822          * we're going inactive then everything else can be deferred
3823          */
3824         if (cfs_b->idle && !throttled)
3825                 goto out_deactivate;
3826 
3827         __refill_cfs_bandwidth_runtime(cfs_b);
3828 
3829         if (!throttled) {
3830                 /* mark as potentially idle for the upcoming period */
3831                 cfs_b->idle = 1;
3832                 return 0;
3833         }
3834 
3835         /* account preceding periods in which throttling occurred */
3836         cfs_b->nr_throttled += overrun;
3837 
3838         runtime_expires = cfs_b->runtime_expires;
3839 
3840         /*
3841          * This check is repeated as we are holding onto the new bandwidth while
3842          * we unthrottle. This can potentially race with an unthrottled group
3843          * trying to acquire new bandwidth from the global pool. This can result
3844          * in us over-using our runtime if it is all used during this loop, but
3845          * only by limited amounts in that extreme case.
3846          */
3847         while (throttled && cfs_b->runtime > 0) {
3848                 runtime = cfs_b->runtime;
3849                 raw_spin_unlock(&cfs_b->lock);
3850                 /* we can't nest cfs_b->lock while distributing bandwidth */
3851                 runtime = distribute_cfs_runtime(cfs_b, runtime,
3852                                                  runtime_expires);
3853                 raw_spin_lock(&cfs_b->lock);
3854 
3855                 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3856 
3857                 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3858         }
3859 
3860         /*
3861          * While we are ensured activity in the period following an
3862          * unthrottle, this also covers the case in which the new bandwidth is
3863          * insufficient to cover the existing bandwidth deficit.  (Forcing the
3864          * timer to remain active while there are any throttled entities.)
3865          */
3866         cfs_b->idle = 0;
3867 
3868         return 0;
3869 
3870 out_deactivate:
3871         return 1;
3872 }
3873 
3874 /* a cfs_rq won't donate quota below this amount */
3875 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3876 /* minimum remaining period time to redistribute slack quota */
3877 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3878 /* how long we wait to gather additional slack before distributing */
3879 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3880 
3881 /*
3882  * Are we near the end of the current quota period?
3883  *
3884  * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3885  * hrtimer base being cleared by hrtimer_start. In the case of
3886  * migrate_hrtimers, base is never cleared, so we are fine.
3887  */
3888 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3889 {
3890         struct hrtimer *refresh_timer = &cfs_b->period_timer;
3891         u64 remaining;
3892 
3893         /* if the call-back is running a quota refresh is already occurring */
3894         if (hrtimer_callback_running(refresh_timer))
3895                 return 1;
3896 
3897         /* is a quota refresh about to occur? */
3898         remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3899         if (remaining < min_expire)
3900                 return 1;
3901 
3902         return 0;
3903 }
3904 
3905 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3906 {
3907         u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3908 
3909         /* if there's a quota refresh soon don't bother with slack */
3910         if (runtime_refresh_within(cfs_b, min_left))
3911                 return;
3912 
3913         hrtimer_start(&cfs_b->slack_timer,
3914                         ns_to_ktime(cfs_bandwidth_slack_period),
3915                         HRTIMER_MODE_REL);
3916 }
3917 
3918 /* we know any runtime found here is valid as update_curr() precedes return */
3919 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3920 {
3921         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3922         s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3923 
3924         if (slack_runtime <= 0)
3925                 return;
3926 
3927         raw_spin_lock(&cfs_b->lock);
3928         if (cfs_b->quota != RUNTIME_INF &&
3929             cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3930                 cfs_b->runtime += slack_runtime;
3931 
3932                 /* we are under rq->lock, defer unthrottling using a timer */
3933                 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3934                     !list_empty(&cfs_b->throttled_cfs_rq))
3935                         start_cfs_slack_bandwidth(cfs_b);
3936         }
3937         raw_spin_unlock(&cfs_b->lock);
3938 
3939         /* even if it's not valid for return we don't want to try again */
3940         cfs_rq->runtime_remaining -= slack_runtime;
3941 }
3942 
3943 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3944 {
3945         if (!cfs_bandwidth_used())
3946                 return;
3947 
3948         if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3949                 return;
3950 
3951         __return_cfs_rq_runtime(cfs_rq);
3952 }
3953 
3954 /*
3955  * This is done with a timer (instead of inline with bandwidth return) since
3956  * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3957  */
3958 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3959 {
3960         u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3961         u64 expires;
3962 
3963         /* confirm we're still not at a refresh boundary */
3964         raw_spin_lock(&cfs_b->lock);
3965         if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3966                 raw_spin_unlock(&cfs_b->lock);
3967                 return;
3968         }
3969 
3970         if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3971                 runtime = cfs_b->runtime;
3972 
3973         expires = cfs_b->runtime_expires;
3974         raw_spin_unlock(&cfs_b->lock);
3975 
3976         if (!runtime)
3977                 return;
3978 
3979         runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3980 
3981         raw_spin_lock(&cfs_b->lock);
3982         if (expires == cfs_b->runtime_expires)
3983                 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3984         raw_spin_unlock(&cfs_b->lock);
3985 }
3986 
3987 /*
3988  * When a group wakes up we want to make sure that its quota is not already
3989  * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3990  * runtime as update_curr() throttling can not not trigger until it's on-rq.
3991  */
3992 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3993 {
3994         if (!cfs_bandwidth_used())
3995                 return;
3996 
3997         /* an active group must be handled by the update_curr()->put() path */
3998         if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3999                 return;
4000 
4001         /* ensure the group is not already throttled */
4002         if (cfs_rq_throttled(cfs_rq))
4003                 return;
4004 
4005         /* update runtime allocation */
4006         account_cfs_rq_runtime(cfs_rq, 0);
4007         if (cfs_rq->runtime_remaining <= 0)
4008                 throttle_cfs_rq(cfs_rq);
4009 }
4010 
4011 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4012 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4013 {
4014         if (!cfs_bandwidth_used())
4015                 return false;
4016 
4017         if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4018                 return false;
4019 
4020         /*
4021          * it's possible for a throttled entity to be forced into a running
4022          * state (e.g. set_curr_task), in this case we're finished.
4023          */
4024         if (cfs_rq_throttled(cfs_rq))
4025                 return true;
4026 
4027         throttle_cfs_rq(cfs_rq);
4028         return true;
4029 }
4030 
4031 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
4032 {
4033         struct cfs_bandwidth *cfs_b =
4034                 container_of(timer, struct cfs_bandwidth, slack_timer);
4035 
4036         do_sched_cfs_slack_timer(cfs_b);
4037 
4038         return HRTIMER_NORESTART;
4039 }
4040 
4041 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
4042 {
4043         struct cfs_bandwidth *cfs_b =
4044                 container_of(timer, struct cfs_bandwidth, period_timer);
4045         int overrun;
4046         int idle = 0;
4047 
4048         raw_spin_lock(&cfs_b->lock);
4049         for (;;) {
4050                 overrun = hrtimer_forward_now(timer, cfs_b->period);
4051                 if (!overrun)
4052                         break;
4053 
4054                 idle = do_sched_cfs_period_timer(cfs_b, overrun);
4055         }
4056         if (idle)
4057                 cfs_b->period_active = 0;
4058         raw_spin_unlock(&cfs_b->lock);
4059 
4060         return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
4061 }
4062 
4063 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4064 {
4065         raw_spin_lock_init(&cfs_b->lock);
4066         cfs_b->runtime = 0;
4067         cfs_b->quota = RUNTIME_INF;
4068         cfs_b->period = ns_to_ktime(default_cfs_period());
4069 
4070         INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4071         hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4072         cfs_b->period_timer.function = sched_cfs_period_timer;
4073         hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4074         cfs_b->slack_timer.function = sched_cfs_slack_timer;
4075 }
4076 
4077 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4078 {
4079         cfs_rq->runtime_enabled = 0;
4080         INIT_LIST_HEAD(&cfs_rq->throttled_list);
4081 }
4082 
4083 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4084 {
4085         lockdep_assert_held(&cfs_b->lock);
4086 
4087         if (!cfs_b->period_active) {
4088                 cfs_b->period_active = 1;
4089                 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4090                 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4091         }
4092 }
4093 
4094 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4095 {
4096         /* init_cfs_bandwidth() was not called */
4097         if (!cfs_b->throttled_cfs_rq.next)
4098                 return;
4099 
4100         hrtimer_cancel(&cfs_b->period_timer);
4101         hrtimer_cancel(&cfs_b->slack_timer);
4102 }
4103 
4104 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4105 {
4106         struct cfs_rq *cfs_rq;
4107 
4108         for_each_leaf_cfs_rq(rq, cfs_rq) {
4109                 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4110 
4111                 raw_spin_lock(&cfs_b->lock);
4112                 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4113                 raw_spin_unlock(&cfs_b->lock);
4114         }
4115 }
4116 
4117 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4118 {
4119         struct cfs_rq *cfs_rq;
4120 
4121         for_each_leaf_cfs_rq(rq, cfs_rq) {
4122                 if (!cfs_rq->runtime_enabled)
4123                         continue;
4124 
4125                 /*
4126                  * clock_task is not advancing so we just need to make sure
4127                  * there's some valid quota amount
4128                  */
4129                 cfs_rq->runtime_remaining = 1;
4130                 /*
4131                  * Offline rq is schedulable till cpu is completely disabled
4132                  * in take_cpu_down(), so we prevent new cfs throttling here.
4133                  */
4134                 cfs_rq->runtime_enabled = 0;
4135 
4136                 if (cfs_rq_throttled(cfs_rq))
4137                         unthrottle_cfs_rq(cfs_rq);
4138         }
4139 }
4140 
4141 #else /* CONFIG_CFS_BANDWIDTH */
4142 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4143 {
4144         return rq_clock_task(rq_of(cfs_rq));
4145 }
4146 
4147 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4148 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4149 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4150 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4151 
4152 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4153 {
4154         return 0;
4155 }
4156 
4157 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4158 {
4159         return 0;
4160 }
4161 
4162 static inline int throttled_lb_pair(struct task_group *tg,
4163                                     int src_cpu, int dest_cpu)
4164 {
4165         return 0;
4166 }
4167 
4168 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4169 
4170 #ifdef CONFIG_FAIR_GROUP_SCHED
4171 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4172 #endif
4173 
4174 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4175 {
4176         return NULL;
4177 }
4178 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4179 static inline void update_runtime_enabled(struct rq *rq) {}
4180 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4181 
4182 #endif /* CONFIG_CFS_BANDWIDTH */
4183 
4184 /**************************************************
4185  * CFS operations on tasks:
4186  */
4187 
4188 #ifdef CONFIG_SCHED_HRTICK
4189 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4190 {
4191         struct sched_entity *se = &p->se;
4192         struct cfs_rq *cfs_rq = cfs_rq_of(se);
4193 
4194         WARN_ON(task_rq(p) != rq);
4195 
4196         if (cfs_rq->nr_running > 1) {
4197                 u64 slice = sched_slice(cfs_rq, se);
4198                 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4199                 s64 delta = slice - ran;
4200 
4201                 if (delta < 0) {
4202                         if (rq->curr == p)
4203                                 resched_curr(rq);
4204                         return;
4205                 }
4206                 hrtick_start(rq, delta);
4207         }
4208 }
4209 
4210 /*
4211  * called from enqueue/dequeue and updates the hrtick when the
4212  * current task is from our class and nr_running is low enough
4213  * to matter.
4214  */
4215 static void hrtick_update(struct rq *rq)
4216 {
4217         struct task_struct *curr = rq->curr;
4218 
4219         if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4220                 return;
4221 
4222         if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4223                 hrtick_start_fair(rq, curr);
4224 }
4225 #else /* !CONFIG_SCHED_HRTICK */
4226 static inline void
4227 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4228 {
4229 }
4230 
4231 static inline void hrtick_update(struct rq *rq)
4232 {
4233 }
4234 #endif
4235 
4236 /*
4237  * The enqueue_task method is called before nr_running is
4238  * increased. Here we update the fair scheduling stats and
4239  * then put the task into the rbtree:
4240  */
4241 static void
4242 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4243 {
4244         struct cfs_rq *cfs_rq;
4245         struct sched_entity *se = &p->se;
4246 
4247         for_each_sched_entity(se) {
4248                 if (se->on_rq)
4249                         break;
4250                 cfs_rq = cfs_rq_of(se);
4251                 enqueue_entity(cfs_rq, se, flags);
4252 
4253                 /*
4254                  * end evaluation on encountering a throttled cfs_rq
4255                  *
4256                  * note: in the case of encountering a throttled cfs_rq we will
4257                  * post the final h_nr_running increment below.
4258                 */
4259                 if (cfs_rq_throttled(cfs_rq))
4260                         break;
4261                 cfs_rq->h_nr_running++;
4262 
4263                 flags = ENQUEUE_WAKEUP;
4264         }
4265 
4266         for_each_sched_entity(se) {
4267                 cfs_rq = cfs_rq_of(se);
4268                 cfs_rq->h_nr_running++;
4269 
4270                 if (cfs_rq_throttled(cfs_rq))
4271                         break;
4272 
4273                 update_load_avg(se, 1);
4274                 update_cfs_shares(cfs_rq);
4275         }
4276 
4277         if (!se)
4278                 add_nr_running(rq, 1);
4279 
4280         hrtick_update(rq);
4281 }
4282 
4283 static void set_next_buddy(struct sched_entity *se);
4284 
4285 /*
4286  * The dequeue_task method is called before nr_running is
4287  * decreased. We remove the task from the rbtree and
4288  * update the fair scheduling stats:
4289  */
4290 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4291 {
4292         struct cfs_rq *cfs_rq;
4293         struct sched_entity *se = &p->se;
4294         int task_sleep = flags & DEQUEUE_SLEEP;
4295 
4296         for_each_sched_entity(se) {
4297                 cfs_rq = cfs_rq_of(se);
4298                 dequeue_entity(cfs_rq, se, flags);
4299 
4300                 /*
4301                  * end evaluation on encountering a throttled cfs_rq
4302                  *
4303                  * note: in the case of encountering a throttled cfs_rq we will
4304                  * post the final h_nr_running decrement below.
4305                 */
4306                 if (cfs_rq_throttled(cfs_rq))
4307                         break;
4308                 cfs_rq->h_nr_running--;
4309 
4310                 /* Don't dequeue parent if it has other entities besides us */
4311                 if (cfs_rq->load.weight) {
4312                         /*
4313                          * Bias pick_next to pick a task from this cfs_rq, as
4314                          * p is sleeping when it is within its sched_slice.
4315                          */
4316                         if (task_sleep && parent_entity(se))
4317                                 set_next_buddy(parent_entity(se));
4318 
4319                         /* avoid re-evaluating load for this entity */
4320                         se = parent_entity(se);
4321                         break;
4322                 }
4323                 flags |= DEQUEUE_SLEEP;
4324         }
4325 
4326         for_each_sched_entity(se) {
4327                 cfs_rq = cfs_rq_of(se);
4328                 cfs_rq->h_nr_running--;
4329 
4330                 if (cfs_rq_throttled(cfs_rq))
4331                         break;
4332 
4333                 update_load_avg(se, 1);
4334                 update_cfs_shares(cfs_rq);
4335         }
4336 
4337         if (!se)
4338                 sub_nr_running(rq, 1);
4339 
4340         hrtick_update(rq);
4341 }
4342 
4343 #ifdef CONFIG_SMP
4344 
4345 /*
4346  * per rq 'load' arrray crap; XXX kill this.
4347  */
4348 
4349 /*
4350  * The exact cpuload calculated at every tick would be:
4351  *
4352  *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4353  *
4354  * If a cpu misses updates for n ticks (as it was idle) and update gets
4355  * called on the n+1-th tick when cpu may be busy, then we have:
4356  *
4357  *   load_n   = (1 - 1/2^i)^n * load_0
4358  *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
4359  *
4360  * decay_load_missed() below does efficient calculation of
4361  *
4362  *   load' = (1 - 1/2^i)^n * load
4363  *
4364  * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4365  * This allows us to precompute the above in said factors, thereby allowing the
4366  * reduction of an arbitrary n in O(log_2 n) steps. (See also
4367  * fixed_power_int())
4368  *
4369  * The calculation is approximated on a 128 point scale.
4370  */
4371 #define DEGRADE_SHIFT           7
4372 
4373 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4374 static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4375         {   0,   0,  0,  0,  0,  0, 0, 0 },
4376         {  64,  32,  8,  0,  0,  0, 0, 0 },
4377         {  96,  72, 40, 12,  1,  0, 0, 0 },
4378         { 112,  98, 75, 43, 15,  1, 0, 0 },
4379         { 120, 112, 98, 76, 45, 16, 2, 0 }
4380 };
4381 
4382 /*
4383  * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4384  * would be when CPU is idle and so we just decay the old load without
4385  * adding any new load.
4386  */
4387 static unsigned long
4388 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4389 {
4390         int j = 0;
4391 
4392         if (!missed_updates)
4393                 return load;
4394 
4395         if (missed_updates >= degrade_zero_ticks[idx])
4396                 return 0;
4397 
4398         if (idx == 1)
4399                 return load >> missed_updates;
4400 
4401         while (missed_updates) {
4402                 if (missed_updates % 2)
4403                         load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4404 
4405                 missed_updates >>= 1;
4406                 j++;
4407         }
4408         return load;
4409 }
4410 
4411 /**
4412  * __update_cpu_load - update the rq->cpu_load[] statistics
4413  * @this_rq: The rq to update statistics for
4414  * @this_load: The current load
4415  * @pending_updates: The number of missed updates
4416  * @active: !0 for NOHZ_FULL
4417  *
4418  * Update rq->cpu_load[] statistics. This function is usually called every
4419  * scheduler tick (TICK_NSEC).
4420  *
4421  * This function computes a decaying average:
4422  *
4423  *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4424  *
4425  * Because of NOHZ it might not get called on every tick which gives need for
4426  * the @pending_updates argument.
4427  *
4428  *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4429  *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4430  *             = A * (A * load[i]_n-2 + B) + B
4431  *             = A * (A * (A * load[i]_n-3 + B) + B) + B
4432  *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4433  *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4434  *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4435  *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4436  *
4437  * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4438  * any change in load would have resulted in the tick being turned back on.
4439  *
4440  * For regular NOHZ, this reduces to:
4441  *
4442  *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
4443  *
4444  * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4445  * term. See the @active paramter.
4446  */
4447 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4448                               unsigned long pending_updates, int active)
4449 {
4450         unsigned long tickless_load = active ? this_rq->cpu_load[0] : 0;
4451         int i, scale;
4452 
4453         this_rq->nr_load_updates++;
4454 
4455         /* Update our load: */
4456         this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4457         for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4458                 unsigned long old_load, new_load;
4459 
4460                 /* scale is effectively 1 << i now, and >> i divides by scale */
4461 
4462                 old_load = this_rq->cpu_load[i] - tickless_load;
4463                 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4464                 old_load += tickless_load;
4465                 new_load = this_load;
4466                 /*
4467                  * Round up the averaging division if load is increasing. This
4468                  * prevents us from getting stuck on 9 if the load is 10, for
4469                  * example.
4470                  */
4471                 if (new_load > old_load)
4472                         new_load += scale - 1;
4473 
4474                 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4475         }
4476 
4477         sched_avg_update(this_rq);
4478 }
4479 
4480 /* Used instead of source_load when we know the type == 0 */
4481 static unsigned long weighted_cpuload(const int cpu)
4482 {
4483         return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4484 }
4485 
4486 #ifdef CONFIG_NO_HZ_COMMON
4487 /*
4488  * There is no sane way to deal with nohz on smp when using jiffies because the
4489  * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4490  * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4491  *
4492  * Therefore we cannot use the delta approach from the regular tick since that
4493  * would seriously skew the load calculation. However we'll make do for those
4494  * updates happening while idle (nohz_idle_balance) or coming out of idle
4495  * (tick_nohz_idle_exit).
4496  *
4497  * This means we might still be one tick off for nohz periods.
4498  */
4499 
4500 /*
4501  * Called from nohz_idle_balance() to update the load ratings before doing the
4502  * idle balance.
4503  */
4504 static void update_idle_cpu_load(struct rq *this_rq)
4505 {
4506         unsigned long curr_jiffies = READ_ONCE(jiffies);
4507         unsigned long load = weighted_cpuload(cpu_of(this_rq));
4508         unsigned long pending_updates;
4509 
4510         /*
4511          * bail if there's load or we're actually up-to-date.
4512          */
4513         if (load || curr_jiffies == this_rq->last_load_update_tick)
4514                 return;
4515 
4516         pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4517         this_rq->last_load_update_tick = curr_jiffies;
4518 
4519         __update_cpu_load(this_rq, load, pending_updates, 0);
4520 }
4521 
4522 /*
4523  * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4524  */
4525 void update_cpu_load_nohz(int active)
4526 {
4527         struct rq *this_rq = this_rq();
4528         unsigned long curr_jiffies = READ_ONCE(jiffies);
4529         unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
4530         unsigned long pending_updates;
4531 
4532         if (curr_jiffies == this_rq->last_load_update_tick)
4533                 return;
4534 
4535         raw_spin_lock(&this_rq->lock);
4536         pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4537         if (pending_updates) {
4538                 this_rq->last_load_update_tick = curr_jiffies;
4539                 /*
4540                  * In the regular NOHZ case, we were idle, this means load 0.
4541                  * In the NOHZ_FULL case, we were non-idle, we should consider
4542                  * its weighted load.
4543                  */
4544                 __update_cpu_load(this_rq, load, pending_updates, active);
4545         }
4546         raw_spin_unlock(&this_rq->lock);
4547 }
4548 #endif /* CONFIG_NO_HZ */
4549 
4550 /*
4551  * Called from scheduler_tick()
4552  */
4553 void update_cpu_load_active(struct rq *this_rq)
4554 {
4555         unsigned long load = weighted_cpuload(cpu_of(this_rq));
4556         /*
4557          * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4558          */
4559         this_rq->last_load_update_tick = jiffies;
4560         __update_cpu_load(this_rq, load, 1, 1);
4561 }
4562 
4563 /*
4564  * Return a low guess at the load of a migration-source cpu weighted
4565  * according to the scheduling class and "nice" value.
4566  *
4567  * We want to under-estimate the load of migration sources, to
4568  * balance conservatively.
4569  */
4570 static unsigned long source_load(int cpu, int type)
4571 {
4572         struct rq *rq = cpu_rq(cpu);
4573         unsigned long total = weighted_cpuload(cpu);
4574 
4575         if (type == 0 || !sched_feat(LB_BIAS))
4576                 return total;
4577 
4578         return min(rq->cpu_load[type-1], total);
4579 }
4580 
4581 /*
4582  * Return a high guess at the load of a migration-target cpu weighted
4583  * according to the scheduling class and "nice" value.
4584  */
4585 static unsigned long target_load(int cpu, int type)
4586 {
4587         struct rq *rq = cpu_rq(cpu);
4588         unsigned long total = weighted_cpuload(cpu);
4589 
4590         if (type == 0 || !sched_feat(LB_BIAS))
4591                 return total;
4592 
4593         return max(rq->cpu_load[type-1], total);
4594 }
4595 
4596 static unsigned long capacity_of(int cpu)
4597 {
4598         return cpu_rq(cpu)->cpu_capacity;
4599 }
4600 
4601 static unsigned long capacity_orig_of(int cpu)
4602 {
4603         return cpu_rq(cpu)->cpu_capacity_orig;
4604 }
4605 
4606 static unsigned long cpu_avg_load_per_task(int cpu)
4607 {
4608         struct rq *rq = cpu_rq(cpu);
4609         unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4610         unsigned long load_avg = weighted_cpuload(cpu);
4611 
4612         if (nr_running)
4613                 return load_avg / nr_running;
4614 
4615         return 0;
4616 }
4617 
4618 static void record_wakee(struct task_struct *p)
4619 {
4620         /*
4621          * Rough decay (wiping) for cost saving, don't worry
4622          * about the boundary, really active task won't care
4623          * about the loss.
4624          */
4625         if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4626                 current->wakee_flips >>= 1;
4627                 current->wakee_flip_decay_ts = jiffies;
4628         }
4629 
4630         if (current->last_wakee != p) {
4631                 current->last_wakee = p;
4632                 current->wakee_flips++;
4633         }
4634 }
4635 
4636 static void task_waking_fair(struct task_struct *p)
4637 {
4638         struct sched_entity *se = &p->se;
4639         struct cfs_rq *cfs_rq = cfs_rq_of(se);
4640         u64 min_vruntime;
4641 
4642 #ifndef CONFIG_64BIT
4643         u64 min_vruntime_copy;
4644 
4645         do {
4646                 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4647                 smp_rmb();
4648                 min_vruntime = cfs_rq->min_vruntime;
4649         } while (min_vruntime != min_vruntime_copy);
4650 #else
4651         min_vruntime = cfs_rq->min_vruntime;
4652 #endif
4653 
4654         se->vruntime -= min_vruntime;
4655         record_wakee(p);
4656 }
4657 
4658 #ifdef CONFIG_FAIR_GROUP_SCHED
4659 /*
4660  * effective_load() calculates the load change as seen from the root_task_group
4661  *
4662  * Adding load to a group doesn't make a group heavier, but can cause movement
4663  * of group shares between cpus. Assuming the shares were perfectly aligned one
4664  * can calculate the shift in shares.
4665  *
4666  * Calculate the effective load difference if @wl is added (subtracted) to @tg
4667  * on this @cpu and results in a total addition (subtraction) of @wg to the
4668  * total group weight.
4669  *
4670  * Given a runqueue weight distribution (rw_i) we can compute a shares
4671  * distribution (s_i) using:
4672  *
4673  *   s_i = rw_i / \Sum rw_j                                             (1)
4674  *
4675  * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4676  * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4677  * shares distribution (s_i):
4678  *
4679  *   rw_i = {   2,   4,   1,   0 }
4680  *   s_i  = { 2/7, 4/7, 1/7,   0 }
4681  *
4682  * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4683  * task used to run on and the CPU the waker is running on), we need to
4684  * compute the effect of waking a task on either CPU and, in case of a sync
4685  * wakeup, compute the effect of the current task going to sleep.
4686  *
4687  * So for a change of @wl to the local @cpu with an overall group weight change
4688  * of @wl we can compute the new shares distribution (s'_i) using:
4689  *
4690  *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)                            (2)
4691  *
4692  * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4693  * differences in waking a task to CPU 0. The additional task changes the
4694  * weight and shares distributions like:
4695  *
4696  *   rw'_i = {   3,   4,   1,   0 }
4697  *   s'_i  = { 3/8, 4/8, 1/8,   0 }
4698  *
4699  * We can then compute the difference in effective weight by using:
4700  *
4701  *   dw_i = S * (s'_i - s_i)                                            (3)
4702  *
4703  * Where 'S' is the group weight as seen by its parent.
4704  *
4705  * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4706  * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4707  * 4/7) times the weight of the group.
4708  */
4709 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4710 {
4711         struct sched_entity *se = tg->se[cpu];
4712 
4713         if (!tg->parent)        /* the trivial, non-cgroup case */
4714                 return wl;
4715 
4716         for_each_sched_entity(se) {
4717                 long w, W;
4718 
4719                 tg = se->my_q->tg;
4720 
4721                 /*
4722                  * W = @wg + \Sum rw_j
4723                  */
4724                 W = wg + calc_tg_weight(tg, se->my_q);
4725 
4726                 /*
4727                  * w = rw_i + @wl
4728                  */
4729                 w = cfs_rq_load_avg(se->my_q) + wl;
4730 
4731                 /*
4732                  * wl = S * s'_i; see (2)
4733                  */
4734                 if (W > 0 && w < W)
4735                         wl = (w * (long)tg->shares) / W;
4736                 else
4737                         wl = tg->shares;
4738 
4739                 /*
4740                  * Per the above, wl is the new se->load.weight value; since
4741                  * those are clipped to [MIN_SHARES, ...) do so now. See
4742                  * calc_cfs_shares().
4743                  */
4744                 if (wl < MIN_SHARES)
4745                         wl = MIN_SHARES;
4746 
4747                 /*
4748                  * wl = dw_i = S * (s'_i - s_i); see (3)
4749                  */
4750                 wl -= se->avg.load_avg;
4751 
4752                 /*
4753                  * Recursively apply this logic to all parent groups to compute
4754                  * the final effective load change on the root group. Since
4755                  * only the @tg group gets extra weight, all parent groups can
4756                  * only redistribute existing shares. @wl is the shift in shares
4757                  * resulting from this level per the above.
4758                  */
4759                 wg = 0;
4760         }
4761 
4762         return wl;
4763 }
4764 #else
4765 
4766 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4767 {
4768         return wl;
4769 }
4770 
4771 #endif
4772 
4773 /*
4774  * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4775  * A waker of many should wake a different task than the one last awakened
4776  * at a frequency roughly N times higher than one of its wakees.  In order
4777  * to determine whether we should let the load spread vs consolodating to
4778  * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4779  * partner, and a factor of lls_size higher frequency in the other.  With
4780  * both conditions met, we can be relatively sure that the relationship is
4781  * non-monogamous, with partner count exceeding socket size.  Waker/wakee
4782  * being client/server, worker/dispatcher, interrupt source or whatever is
4783  * irrelevant, spread criteria is apparent partner count exceeds socket size.
4784  */
4785 static int wake_wide(struct task_struct *p)
4786 {
4787         unsigned int master = current->wakee_flips;
4788         unsigned int slave = p->wakee_flips;
4789         int factor = this_cpu_read(sd_llc_size);
4790 
4791         if (master < slave)
4792                 swap(master, slave);
4793         if (slave < factor || master < slave * factor)
4794                 return 0;
4795         return 1;
4796 }
4797 
4798 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4799 {
4800         s64 this_load, load;
4801         s64 this_eff_load, prev_eff_load;
4802         int idx, this_cpu, prev_cpu;
4803         struct task_group *tg;
4804         unsigned long weight;
4805         int balanced;
4806 
4807         idx       = sd->wake_idx;
4808         this_cpu  = smp_processor_id();
4809         prev_cpu  = task_cpu(p);
4810         load      = source_load(prev_cpu, idx);
4811         this_load = target_load(this_cpu, idx);
4812 
4813         /*
4814          * If sync wakeup then subtract the (maximum possible)
4815          * effect of the currently running task from the load
4816          * of the current CPU:
4817          */
4818         if (sync) {
4819                 tg = task_group(current);
4820                 weight = current->se.avg.load_avg;
4821 
4822                 this_load += effective_load(tg, this_cpu, -weight, -weight);
4823                 load += effective_load(tg, prev_cpu, 0, -weight);
4824         }
4825 
4826         tg = task_group(p);
4827         weight = p->se.avg.load_avg;
4828 
4829         /*
4830          * In low-load situations, where prev_cpu is idle and this_cpu is idle
4831          * due to the sync cause above having dropped this_load to 0, we'll
4832          * always have an imbalance, but there's really nothing you can do
4833          * about that, so that's good too.
4834          *
4835          * Otherwise check if either cpus are near enough in load to allow this
4836          * task to be woken on this_cpu.
4837          */
4838         this_eff_load = 100;
4839         this_eff_load *= capacity_of(prev_cpu);
4840 
4841         prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4842         prev_eff_load *= capacity_of(this_cpu);
4843 
4844         if (this_load > 0) {
4845                 this_eff_load *= this_load +
4846                         effective_load(tg, this_cpu, weight, weight);
4847 
4848                 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4849         }
4850 
4851         balanced = this_eff_load <= prev_eff_load;
4852 
4853         schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4854 
4855         if (!balanced)
4856                 return 0;
4857 
4858         schedstat_inc(sd, ttwu_move_affine);
4859         schedstat_inc(p, se.statistics.nr_wakeups_affine);
4860 
4861         return 1;
4862 }
4863 
4864 /*
4865  * find_idlest_group finds and returns the least busy CPU group within the
4866  * domain.
4867  */
4868 static struct sched_group *
4869 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4870                   int this_cpu, int sd_flag)
4871 {
4872         struct sched_group *idlest = NULL, *group = sd->groups;
4873         unsigned long min_load = ULONG_MAX, this_load = 0;
4874         int load_idx = sd->forkexec_idx;
4875         int imbalance = 100 + (sd->imbalance_pct-100)/2;
4876 
4877         if (sd_flag & SD_BALANCE_WAKE)
4878                 load_idx = sd->wake_idx;
4879 
4880         do {
4881                 unsigned long load, avg_load;
4882                 int local_group;
4883                 int i;
4884 
4885                 /* Skip over this group if it has no CPUs allowed */
4886                 if (!cpumask_intersects(sched_group_cpus(group),
4887                                         tsk_cpus_allowed(p)))
4888                         continue;
4889 
4890                 local_group = cpumask_test_cpu(this_cpu,
4891                                                sched_group_cpus(group));
4892 
4893                 /* Tally up the load of all CPUs in the group */
4894                 avg_load = 0;
4895 
4896                 for_each_cpu(i, sched_group_cpus(group)) {
4897                         /* Bias balancing toward cpus of our domain */
4898                         if (local_group)
4899                                 load = source_load(i, load_idx);
4900                         else
4901                                 load = target_load(i, load_idx);
4902 
4903                         avg_load += load;
4904                 }
4905 
4906                 /* Adjust by relative CPU capacity of the group */
4907                 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4908 
4909                 if (local_group) {
4910                         this_load = avg_load;
4911                 } else if (avg_load < min_load) {
4912                         min_load = avg_load;
4913                         idlest = group;
4914                 }
4915         } while (group = group->next, group != sd->groups);
4916 
4917         if (!idlest || 100*this_load < imbalance*min_load)
4918                 return NULL;
4919         return idlest;
4920 }
4921 
4922 /*
4923  * find_idlest_cpu - find the idlest cpu among the cpus in group.
4924  */
4925 static int
4926 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4927 {
4928         unsigned long load, min_load = ULONG_MAX;
4929         unsigned int min_exit_latency = UINT_MAX;
4930         u64 latest_idle_timestamp = 0;
4931         int least_loaded_cpu = this_cpu;
4932         int shallowest_idle_cpu = -1;
4933         int i;
4934 
4935         /* Traverse only the allowed CPUs */
4936         for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4937                 if (idle_cpu(i)) {
4938                         struct rq *rq = cpu_rq(i);
4939                         struct cpuidle_state *idle = idle_get_state(rq);
4940                         if (idle && idle->exit_latency < min_exit_latency) {
4941                                 /*
4942                                  * We give priority to a CPU whose idle state
4943                                  * has the smallest exit latency irrespective
4944                                  * of any idle timestamp.
4945                                  */
4946                                 min_exit_latency = idle->exit_latency;
4947                                 latest_idle_timestamp = rq->idle_stamp;
4948                                 shallowest_idle_cpu = i;
4949                         } else if ((!idle || idle->exit_latency == min_exit_latency) &&
4950                                    rq->idle_stamp > latest_idle_timestamp) {
4951                                 /*
4952                                  * If equal or no active idle state, then
4953                                  * the most recently idled CPU might have
4954                                  * a warmer cache.
4955                                  */
4956                                 latest_idle_timestamp = rq->idle_stamp;
4957                                 shallowest_idle_cpu = i;
4958                         }
4959                 } else if (shallowest_idle_cpu == -1) {
4960                         load = weighted_cpuload(i);
4961                         if (load < min_load || (load == min_load && i == this_cpu)) {
4962                                 min_load = load;
4963                                 least_loaded_cpu = i;
4964                         }
4965                 }
4966         }
4967 
4968         return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4969 }
4970 
4971 /*
4972  * Try and locate an idle CPU in the sched_domain.
4973  */
4974 static int select_idle_sibling(struct task_struct *p, int target)
4975 {
4976         struct sched_domain *sd;
4977         struct sched_group *sg;
4978         int i = task_cpu(p);
4979 
4980         if (idle_cpu(target))
4981                 return target;
4982 
4983         /*
4984          * If the prevous cpu is cache affine and idle, don't be stupid.
4985          */
4986         if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4987                 return i;
4988 
4989         /*
4990          * Otherwise, iterate the domains and find an elegible idle cpu.
4991          */
4992         sd = rcu_dereference(per_cpu(sd_llc, target));
4993         for_each_lower_domain(sd) {
4994                 sg = sd->groups;
4995                 do {
4996                         if (!cpumask_intersects(sched_group_cpus(sg),
4997                                                 tsk_cpus_allowed(p)))
4998                                 goto next;
4999 
5000                         for_each_cpu(i, sched_group_cpus(sg)) {
5001                                 if (i == target || !idle_cpu(i))
5002                                         goto next;
5003                         }
5004 
5005                         target = cpumask_first_and(sched_group_cpus(sg),
5006                                         tsk_cpus_allowed(p));
5007                         goto done;
5008 next:
5009                         sg = sg->next;
5010                 } while (sg != sd->groups);
5011         }
5012 done:
5013         return target;
5014 }
5015 
5016 /*
5017  * cpu_util returns the amount of capacity of a CPU that is used by CFS
5018  * tasks. The unit of the return value must be the one of capacity so we can
5019  * compare the utilization with the capacity of the CPU that is available for
5020  * CFS task (ie cpu_capacity).
5021  *
5022  * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5023  * recent utilization of currently non-runnable tasks on a CPU. It represents
5024  * the amount of utilization of a CPU in the range [0..capacity_orig] where
5025  * capacity_orig is the cpu_capacity available at the highest frequency
5026  * (arch_scale_freq_capacity()).
5027  * The utilization of a CPU converges towards a sum equal to or less than the
5028  * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5029  * the running time on this CPU scaled by capacity_curr.
5030  *
5031  * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5032  * higher than capacity_orig because of unfortunate rounding in
5033  * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5034  * the average stabilizes with the new running time. We need to check that the
5035  * utilization stays within the range of [0..capacity_orig] and cap it if
5036  * necessary. Without utilization capping, a group could be seen as overloaded
5037  * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5038  * available capacity. We allow utilization to overshoot capacity_curr (but not
5039  * capacity_orig) as it useful for predicting the capacity required after task
5040  * migrations (scheduler-driven DVFS).
5041  */
5042 static int cpu_util(int cpu)
5043 {
5044         unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5045         unsigned long capacity = capacity_orig_of(cpu);
5046 
5047         return (util >= capacity) ? capacity : util;
5048 }
5049 
5050 /*
5051  * select_task_rq_fair: Select target runqueue for the waking task in domains
5052  * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5053  * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5054  *
5055  * Balances load by selecting the idlest cpu in the idlest group, or under
5056  * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5057  *
5058  * Returns the target cpu number.
5059  *
5060  * preempt must be disabled.
5061  */
5062 static int
5063 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5064 {
5065         struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5066         int cpu = smp_processor_id();
5067         int new_cpu = prev_cpu;
5068         int want_affine = 0;
5069         int sync = wake_flags & WF_SYNC;
5070 
5071         if (sd_flag & SD_BALANCE_WAKE)
5072                 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5073 
5074         rcu_read_lock();
5075         for_each_domain(cpu, tmp) {
5076                 if (!(tmp->flags & SD_LOAD_BALANCE))
5077                         break;
5078 
5079                 /*
5080                  * If both cpu and prev_cpu are part of this domain,
5081                  * cpu is a valid SD_WAKE_AFFINE target.
5082                  */
5083                 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5084                     cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5085                         affine_sd = tmp;
5086                         break;
5087                 }
5088 
5089                 if (tmp->flags & sd_flag)
5090                         sd = tmp;
5091                 else if (!want_affine)
5092                         break;
5093         }
5094 
5095         if (affine_sd) {
5096                 sd = NULL; /* Prefer wake_affine over balance flags */
5097                 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5098                         new_cpu = cpu;
5099         }
5100 
5101         if (!sd) {
5102                 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5103                         new_cpu = select_idle_sibling(p, new_cpu);
5104 
5105         } else while (sd) {
5106                 struct sched_group *group;
5107                 int weight;
5108 
5109                 if (!(sd->flags & sd_flag)) {
5110                         sd = sd->child;
5111                         continue;
5112                 }
5113 
5114                 group = find_idlest_group(sd, p, cpu, sd_flag);
5115                 if (!group) {
5116                         sd = sd->child;
5117                         continue;
5118                 }
5119 
5120                 new_cpu = find_idlest_cpu(group, p, cpu);
5121                 if (new_cpu == -1 || new_cpu == cpu) {
5122                         /* Now try balancing at a lower domain level of cpu */
5123                         sd = sd->child;
5124                         continue;
5125                 }
5126 
5127                 /* Now try balancing at a lower domain level of new_cpu */
5128                 cpu = new_cpu;
5129                 weight = sd->span_weight;
5130                 sd = NULL;
5131                 for_each_domain(cpu, tmp) {
5132                         if (weight <= tmp->span_weight)
5133                                 break;
5134                         if (tmp->flags & sd_flag)
5135                                 sd = tmp;
5136                 }
5137                 /* while loop will break here if sd == NULL */
5138         }
5139         rcu_read_unlock();
5140 
5141         return new_cpu;
5142 }
5143 
5144 /*
5145  * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5146  * cfs_rq_of(p) references at time of call are still valid and identify the
5147  * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5148  */
5149 static void migrate_task_rq_fair(struct task_struct *p)
5150 {
5151         /*
5152          * We are supposed to update the task to "current" time, then its up to date
5153          * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5154          * what current time is, so simply throw away the out-of-date time. This
5155          * will result in the wakee task is less decayed, but giving the wakee more
5156          * load sounds not bad.
5157          */
5158         remove_entity_load_avg(&p->se);
5159 
5160         /* Tell new CPU we are migrated */
5161         p->se.avg.last_update_time = 0;
5162 
5163         /* We have migrated, no longer consider this task hot */
5164         p->se.exec_start = 0;
5165 }
5166 
5167 static void task_dead_fair(struct task_struct *p)
5168 {
5169         remove_entity_load_avg(&p->se);
5170 }
5171 #endif /* CONFIG_SMP */
5172 
5173 static unsigned long
5174 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5175 {
5176         unsigned long gran = sysctl_sched_wakeup_granularity;
5177 
5178         /*
5179          * Since its curr running now, convert the gran from real-time
5180          * to virtual-time in his units.
5181          *
5182          * By using 'se' instead of 'curr' we penalize light tasks, so
5183          * they get preempted easier. That is, if 'se' < 'curr' then
5184          * the resulting gran will be larger, therefore penalizing the
5185          * lighter, if otoh 'se' > 'curr' then the resulting gran will
5186          * be smaller, again penalizing the lighter task.
5187          *
5188          * This is especially important for buddies when the leftmost
5189          * task is higher priority than the buddy.
5190          */
5191         return calc_delta_fair(gran, se);
5192 }
5193 
5194 /*
5195  * Should 'se' preempt 'curr'.
5196  *
5197  *             |s1
5198  *        |s2
5199  *   |s3
5200  *         g
5201  *      |<--->|c
5202  *
5203  *  w(c, s1) = -1
5204  *  w(c, s2) =  0
5205  *  w(c, s3) =  1
5206  *
5207  */
5208 static int
5209 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5210 {
5211         s64 gran, vdiff = curr->vruntime - se->vruntime;
5212 
5213         if (vdiff <= 0)
5214                 return -1;
5215 
5216         gran = wakeup_gran(curr, se);
5217         if (vdiff > gran)
5218                 return 1;
5219 
5220         return 0;
5221 }
5222 
5223 static void set_last_buddy(struct sched_entity *se)
5224 {
5225         if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5226                 return;
5227 
5228         for_each_sched_entity(se)
5229                 cfs_rq_of(se)->last = se;
5230 }
5231 
5232 static void set_next_buddy(struct sched_entity *se)
5233 {
5234         if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5235                 return;
5236 
5237         for_each_sched_entity(se)
5238                 cfs_rq_of(se)->next = se;
5239 }
5240 
5241 static void set_skip_buddy(struct sched_entity *se)
5242 {
5243         for_each_sched_entity(se)
5244                 cfs_rq_of(se)->skip = se;
5245 }
5246 
5247 /*
5248  * Preempt the current task with a newly woken task if needed:
5249  */
5250 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5251 {
5252         struct task_struct *curr = rq->curr;
5253         struct sched_entity *se = &curr->se, *pse = &p->se;
5254         struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5255         int scale = cfs_rq->nr_running >= sched_nr_latency;
5256         int next_buddy_marked = 0;
5257 
5258         if (unlikely(se == pse))
5259                 return;
5260 
5261         /*
5262          * This is possible from callers such as attach_tasks(), in which we
5263          * unconditionally check_prempt_curr() after an enqueue (which may have
5264          * lead to a throttle).  This both saves work and prevents false
5265          * next-buddy nomination below.
5266          */
5267         if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5268                 return;
5269 
5270         if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5271                 set_next_buddy(pse);
5272                 next_buddy_marked = 1;
5273         }
5274 
5275         /*
5276          * We can come here with TIF_NEED_RESCHED already set from new task
5277          * wake up path.
5278          *
5279          * Note: this also catches the edge-case of curr being in a throttled
5280          * group (e.g. via set_curr_task), since update_curr() (in the
5281          * enqueue of curr) will have resulted in resched being set.  This
5282          * prevents us from potentially nominating it as a false LAST_BUDDY
5283          * below.
5284          */
5285         if (test_tsk_need_resched(curr))
5286                 return;
5287 
5288         /* Idle tasks are by definition preempted by non-idle tasks. */
5289         if (unlikely(curr->policy == SCHED_IDLE) &&
5290             likely(p->policy != SCHED_IDLE))
5291                 goto preempt;
5292 
5293         /*
5294          * Batch and idle tasks do not preempt non-idle tasks (their preemption
5295          * is driven by the tick):
5296          */
5297         if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5298                 return;
5299 
5300         find_matching_se(&se, &pse);
5301         update_curr(cfs_rq_of(se));
5302         BUG_ON(!pse);
5303         if (wakeup_preempt_entity(se, pse) == 1) {
5304                 /*
5305                  * Bias pick_next to pick the sched entity that is
5306                  * triggering this preemption.
5307                  */
5308                 if (!next_buddy_marked)
5309                         set_next_buddy(pse);
5310                 goto preempt;
5311         }
5312 
5313         return;
5314 
5315 preempt:
5316         resched_curr(rq);
5317         /*
5318          * Only set the backward buddy when the current task is still
5319          * on the rq. This can happen when a wakeup gets interleaved
5320          * with schedule on the ->pre_schedule() or idle_balance()
5321          * point, either of which can * drop the rq lock.
5322          *
5323          * Also, during early boot the idle thread is in the fair class,
5324          * for obvious reasons its a bad idea to schedule back to it.
5325          */
5326         if (unlikely(!se->on_rq || curr == rq->idle))
5327                 return;
5328 
5329         if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5330                 set_last_buddy(se);
5331 }
5332 
5333 static struct task_struct *
5334 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5335 {
5336         struct cfs_rq *cfs_rq = &rq->cfs;
5337         struct sched_entity *se;
5338         struct task_struct *p;
5339         int new_tasks;
5340 
5341 again:
5342 #ifdef CONFIG_FAIR_GROUP_SCHED
5343         if (!cfs_rq->nr_running)
5344                 goto idle;
5345 
5346         if (prev->sched_class != &fair_sched_class)
5347                 goto simple;
5348 
5349         /*
5350          * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5351          * likely that a next task is from the same cgroup as the current.
5352          *
5353          * Therefore attempt to avoid putting and setting the entire cgroup
5354          * hierarchy, only change the part that actually changes.
5355          */
5356 
5357         do {
5358                 struct sched_entity *curr = cfs_rq->curr;
5359 
5360                 /*
5361                  * Since we got here without doing put_prev_entity() we also
5362                  * have to consider cfs_rq->curr. If it is still a runnable
5363                  * entity, update_curr() will update its vruntime, otherwise
5364                  * forget we've ever seen it.
5365                  */
5366                 if (curr) {
5367                         if (curr->on_rq)
5368                                 update_curr(cfs_rq);
5369                         else
5370                                 curr = NULL;
5371 
5372                         /*
5373                          * This call to check_cfs_rq_runtime() will do the
5374                          * throttle and dequeue its entity in the parent(s).
5375                          * Therefore the 'simple' nr_running test will indeed
5376                          * be correct.
5377                          */
5378                         if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5379                                 goto simple;
5380                 }
5381 
5382                 se = pick_next_entity(cfs_rq, curr);
5383                 cfs_rq = group_cfs_rq(se);
5384         } while (cfs_rq);
5385 
5386         p = task_of(se);
5387 
5388         /*
5389          * Since we haven't yet done put_prev_entity and if the selected task
5390          * is a different task than we started out with, try and touch the
5391          * least amount of cfs_rqs.
5392          */
5393         if (prev != p) {
5394                 struct sched_entity *pse = &prev->se;
5395 
5396                 while (!(cfs_rq = is_same_group(se, pse))) {
5397                         int se_depth = se->depth;
5398                         int pse_depth = pse->depth;
5399 
5400                         if (se_depth <= pse_depth) {
5401                                 put_prev_entity(cfs_rq_of(pse), pse);
5402                                 pse = parent_entity(pse);
5403                         }
5404                         if (se_depth >= pse_depth) {
5405                                 set_next_entity(cfs_rq_of(se), se);
5406                                 se = parent_entity(se);
5407                         }
5408                 }
5409 
5410                 put_prev_entity(cfs_rq, pse);
5411                 set_next_entity(cfs_rq, se);
5412         }
5413 
5414         if (hrtick_enabled(rq))
5415                 hrtick_start_fair(rq, p);
5416 
5417         return p;
5418 simple:
5419         cfs_rq = &rq->cfs;
5420 #endif
5421 
5422         if (!cfs_rq->nr_running)
5423                 goto idle;
5424 
5425         put_prev_task(rq, prev);
5426 
5427         do {
5428                 se = pick_next_entity(cfs_rq, NULL);
5429                 set_next_entity(cfs_rq, se);
5430                 cfs_rq = group_cfs_rq(se);
5431         } while (cfs_rq);
5432 
5433         p = task_of(se);
5434 
5435         if (hrtick_enabled(rq))
5436                 hrtick_start_fair(rq, p);
5437 
5438         return p;
5439 
5440 idle:
5441         /*
5442          * This is OK, because current is on_cpu, which avoids it being picked
5443          * for load-balance and preemption/IRQs are still disabled avoiding
5444          * further scheduler activity on it and we're being very careful to
5445          * re-start the picking loop.
5446          */
5447         lockdep_unpin_lock(&rq->lock);
5448         new_tasks = idle_balance(rq);
5449         lockdep_pin_lock(&rq->lock);
5450         /*
5451          * Because idle_balance() releases (and re-acquires) rq->lock, it is
5452          * possible for any higher priority task to appear. In that case we
5453          * must re-start the pick_next_entity() loop.
5454          */
5455         if (new_tasks < 0)
5456                 return RETRY_TASK;
5457 
5458         if (new_tasks > 0)
5459                 goto again;
5460 
5461         return NULL;
5462 }
5463 
5464 /*
5465  * Account for a descheduled task:
5466  */
5467 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5468 {
5469         struct sched_entity *se = &prev->se;
5470         struct cfs_rq *cfs_rq;
5471 
5472         for_each_sched_entity(se) {
5473                 cfs_rq = cfs_rq_of(se);
5474                 put_prev_entity(cfs_rq, se);
5475         }
5476 }
5477 
5478 /*
5479  * sched_yield() is very simple
5480  *
5481  * The magic of dealing with the ->skip buddy is in pick_next_entity.
5482  */
5483 static void yield_task_fair(struct rq *rq)
5484 {
5485         struct task_struct *curr = rq->curr;
5486         struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5487         struct sched_entity *se = &curr->se;
5488 
5489         /*
5490          * Are we the only task in the tree?
5491          */
5492         if (unlikely(rq->nr_running == 1))
5493                 return;
5494 
5495         clear_buddies(cfs_rq, se);
5496 
5497         if (curr->policy != SCHED_BATCH) {
5498                 update_rq_clock(rq);
5499                 /*
5500                  * Update run-time statistics of the 'current'.
5501                  */
5502                 update_curr(cfs_rq);
5503                 /*
5504                  * Tell update_rq_clock() that we've just updated,
5505                  * so we don't do microscopic update in schedule()
5506                  * and double the fastpath cost.
5507                  */
5508                 rq_clock_skip_update(rq, true);
5509         }
5510 
5511         set_skip_buddy(se);
5512 }
5513 
5514 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5515 {
5516         struct sched_entity *se = &p->se;
5517 
5518         /* throttled hierarchies are not runnable */
5519         if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5520                 return false;
5521 
5522         /* Tell the scheduler that we'd really like pse to run next. */
5523         set_next_buddy(se);
5524 
5525         yield_task_fair(rq);
5526 
5527         return true;
5528 }
5529 
5530 #ifdef CONFIG_SMP
5531 /**************************************************
5532  * Fair scheduling class load-balancing methods.
5533  *
5534  * BASICS
5535  *
5536  * The purpose of load-balancing is to achieve the same basic fairness the
5537  * per-cpu scheduler provides, namely provide a proportional amount of compute
5538  * time to each task. This is expressed in the following equation:
5539  *
5540  *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
5541  *
5542  * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5543  * W_i,0 is defined as:
5544  *
5545  *   W_i,0 = \Sum_j w_i,j                                             (2)
5546  *
5547  * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5548  * is derived from the nice value as per prio_to_weight[].
5549  *
5550  * The weight average is an exponential decay average of the instantaneous
5551  * weight:
5552  *
5553  *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
5554  *
5555  * C_i is the compute capacity of cpu i, typically it is the
5556  * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5557  * can also include other factors [XXX].
5558  *
5559  * To achieve this balance we define a measure of imbalance which follows
5560  * directly from (1):
5561  *
5562  *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
5563  *
5564  * We them move tasks around to minimize the imbalance. In the continuous
5565  * function space it is obvious this converges, in the discrete case we get
5566  * a few fun cases generally called infeasible weight scenarios.
5567  *
5568  * [XXX expand on:
5569  *     - infeasible weights;
5570  *     - local vs global optima in the discrete case. ]
5571  *
5572  *
5573  * SCHED DOMAINS
5574  *
5575  * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5576  * for all i,j solution, we create a tree of cpus that follows the hardware
5577  * topology where each level pairs two lower groups (or better). This results
5578  * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5579  * tree to only the first of the previous level and we decrease the frequency
5580  * of load-balance at each level inv. proportional to the number of cpus in
5581  * the groups.
5582  *
5583  * This yields:
5584  *
5585  *     log_2 n     1     n
5586  *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
5587  *     i = 0      2^i   2^i
5588  *                               `- size of each group
5589  *         |         |     `- number of cpus doing load-balance
5590  *         |         `- freq
5591  *         `- sum over all levels
5592  *
5593  * Coupled with a limit on how many tasks we can migrate every balance pass,
5594  * this makes (5) the runtime complexity of the balancer.
5595  *
5596  * An important property here is that each CPU is still (indirectly) connected
5597  * to every other cpu in at most O(log n) steps:
5598  *
5599  * The adjacency matrix of the resulting graph is given by:
5600  *
5601  *             log_2 n     
5602  *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
5603  *             k = 0
5604  *
5605  * And you'll find that:
5606  *
5607  *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
5608  *
5609  * Showing there's indeed a path between every cpu in at most O(log n) steps.
5610  * The task movement gives a factor of O(m), giving a convergence complexity
5611  * of:
5612  *
5613  *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
5614  *
5615  *
5616  * WORK CONSERVING
5617  *
5618  * In order to avoid CPUs going idle while there's still work to do, new idle
5619  * balancing is more aggressive and has the newly idle cpu iterate up the domain
5620  * tree itself instead of relying on other CPUs to bring it work.
5621  *
5622  * This adds some complexity to both (5) and (8) but it reduces the total idle
5623  * time.
5624  *
5625  * [XXX more?]
5626  *
5627  *
5628  * CGROUPS
5629  *
5630  * Cgroups make a horror show out of (2), instead of a simple sum we get:
5631  *
5632  *                                s_k,i
5633  *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
5634  *                                 S_k
5635  *
5636  * Where
5637  *
5638  *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
5639  *
5640  * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5641  *
5642  * The big problem is S_k, its a global sum needed to compute a local (W_i)
5643  * property.
5644  *
5645  * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5646  *      rewrite all of this once again.]
5647  */ 
5648 
5649 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5650 
5651 enum fbq_type { regular, remote, all };
5652 
5653 #define LBF_ALL_PINNED  0x01
5654 #define LBF_NEED_BREAK  0x02
5655 #define LBF_DST_PINNED  0x04
5656 #define LBF_SOME_PINNED 0x08
5657 
5658 struct lb_env {
5659         struct sched_domain     *sd;
5660 
5661         struct rq               *src_rq;
5662         int                     src_cpu;
5663 
5664         int                     dst_cpu;
5665         struct rq               *dst_rq;
5666 
5667         struct cpumask          *dst_grpmask;
5668         int                     new_dst_cpu;
5669         enum cpu_idle_type      idle;
5670         long                    imbalance;
5671         /* The set of CPUs under consideration for load-balancing */
5672         struct cpumask          *cpus;
5673 
5674         unsigned int            flags;
5675 
5676         unsigned int            loop;
5677         unsigned int            loop_break;
5678         unsigned int            loop_max;
5679 
5680         enum fbq_type           fbq_type;
5681         struct list_head        tasks;
5682 };
5683 
5684 /*
5685  * Is this task likely cache-hot:
5686  */
5687 static int task_hot(struct task_struct *p, struct lb_env *env)
5688 {
5689         s64 delta;
5690 
5691         lockdep_assert_held(&env->src_rq->lock);
5692 
5693         if (p->sched_class != &fair_sched_class)
5694                 return 0;
5695 
5696         if (unlikely(p->policy == SCHED_IDLE))
5697                 return 0;
5698 
5699         /*
5700          * Buddy candidates are cache hot:
5701          */
5702         if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5703                         (&p->se == cfs_rq_of(&p->se)->next ||
5704                          &p->se == cfs_rq_of(&p->se)->last))
5705                 return 1;
5706 
5707         if (sysctl_sched_migration_cost == -1)
5708                 return 1;
5709         if (sysctl_sched_migration_cost == 0)
5710                 return 0;
5711 
5712         delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5713 
5714         return delta < (s64)sysctl_sched_migration_cost;
5715 }
5716 
5717 #ifdef CONFIG_NUMA_BALANCING
5718 /*
5719  * Returns 1, if task migration degrades locality
5720  * Returns 0, if task migration improves locality i.e migration preferred.
5721  * Returns -1, if task migration is not affected by locality.
5722  */
5723 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5724 {
5725         struct numa_group *numa_group = rcu_dereference(p->numa_group);
5726         unsigned long src_faults, dst_faults;
5727         int src_nid, dst_nid;
5728 
5729         if (!static_branch_likely(&sched_numa_balancing))
5730                 return -1;
5731 
5732         if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5733                 return -1;
5734 
5735         src_nid = cpu_to_node(env->src_cpu);
5736         dst_nid = cpu_to_node(env->dst_cpu);
5737 
5738         if (src_nid == dst_nid)
5739                 return -1;
5740 
5741         /* Migrating away from the preferred node is always bad. */
5742         if (src_nid == p->numa_preferred_nid) {
5743                 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5744                         return 1;
5745                 else
5746                         return -1;
5747         }
5748 
5749         /* Encourage migration to the preferred node. */
5750         if (dst_nid == p->numa_preferred_nid)
5751                 return 0;
5752 
5753         if (numa_group) {
5754                 src_faults = group_faults(p, src_nid);
5755                 dst_faults = group_faults(p, dst_nid);
5756         } else {
5757                 src_faults = task_faults(p, src_nid);
5758                 dst_faults = task_faults(p, dst_nid);
5759         }
5760 
5761         return dst_faults < src_faults;
5762 }
5763 
5764 #else
5765 static inline int migrate_degrades_locality(struct task_struct *p,
5766                                              struct lb_env *env)
5767 {
5768         return -1;
5769 }
5770 #endif
5771 
5772 /*
5773  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5774  */
5775 static
5776 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5777 {
5778         int tsk_cache_hot;
5779 
5780         lockdep_assert_held(&env->src_rq->lock);
5781 
5782         /*
5783          * We do not migrate tasks that are:
5784          * 1) throttled_lb_pair, or
5785          * 2) cannot be migrated to this CPU due to cpus_allowed, or
5786          * 3) running (obviously), or
5787          * 4) are cache-hot on their current CPU.
5788          */
5789         if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5790                 return 0;
5791 
5792         if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5793                 int cpu;
5794 
5795                 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5796 
5797                 env->flags |= LBF_SOME_PINNED;
5798 
5799                 /*
5800                  * Remember if this task can be migrated to any other cpu in
5801                  * our sched_group. We may want to revisit it if we couldn't
5802                  * meet load balance goals by pulling other tasks on src_cpu.
5803                  *
5804                  * Also avoid computing new_dst_cpu if we have already computed
5805                  * one in current iteration.
5806                  */
5807                 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5808                         return 0;
5809 
5810                 /* Prevent to re-select dst_cpu via env's cpus */
5811                 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5812                         if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5813                                 env->flags |= LBF_DST_PINNED;
5814                                 env->new_dst_cpu = cpu;
5815                                 break;
5816                         }
5817                 }
5818 
5819                 return 0;
5820         }
5821 
5822         /* Record that we found atleast one task that could run on dst_cpu */
5823         env->flags &= ~LBF_ALL_PINNED;
5824 
5825         if (task_running(env->src_rq, p)) {
5826                 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5827                 return 0;
5828         }
5829 
5830         /*
5831          * Aggressive migration if:
5832          * 1) destination numa is preferred
5833          * 2) task is cache cold, or
5834          * 3) too many balance attempts have failed.
5835          */
5836         tsk_cache_hot = migrate_degrades_locality(p, env);
5837         if (tsk_cache_hot == -1)
5838                 tsk_cache_hot = task_hot(p, env);
5839 
5840         if (tsk_cache_hot <= 0 ||
5841             env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5842                 if (tsk_cache_hot == 1) {
5843                         schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5844                         schedstat_inc(p, se.statistics.nr_forced_migrations);
5845                 }
5846                 return 1;
5847         }
5848 
5849         schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5850         return 0;
5851 }
5852 
5853 /*
5854  * detach_task() -- detach the task for the migration specified in env
5855  */
5856 static void detach_task(struct task_struct *p, struct lb_env *env)
5857 {
5858         lockdep_assert_held(&env->src_rq->lock);
5859 
5860         p->on_rq = TASK_ON_RQ_MIGRATING;
5861         deactivate_task(env->src_rq, p, 0);
5862         set_task_cpu(p, env->dst_cpu);
5863 }
5864 
5865 /*
5866  * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5867  * part of active balancing operations within "domain".
5868  *
5869  * Returns a task if successful and NULL otherwise.
5870  */
5871 static struct task_struct *detach_one_task(struct lb_env *env)
5872 {
5873         struct task_struct *p, *n;
5874 
5875         lockdep_assert_held(&env->src_rq->lock);
5876 
5877         list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5878                 if (!can_migrate_task(p, env))
5879                         continue;
5880 
5881                 detach_task(p, env);
5882 
5883                 /*
5884                  * Right now, this is only the second place where
5885                  * lb_gained[env->idle] is updated (other is detach_tasks)
5886                  * so we can safely collect stats here rather than
5887                  * inside detach_tasks().
5888                  */
5889                 schedstat_inc(env->sd, lb_gained[env->idle]);
5890                 return p;
5891         }
5892         return NULL;
5893 }
5894 
5895 static const unsigned int sched_nr_migrate_break = 32;
5896 
5897 /*
5898  * detach_tasks() -- tries to detach up to imbalance weighted load from
5899  * busiest_rq, as part of a balancing operation within domain "sd".
5900  *
5901  * Returns number of detached tasks if successful and 0 otherwise.
5902  */
5903 static int detach_tasks(struct lb_env *env)
5904 {
5905         struct list_head *tasks = &env->src_rq->cfs_tasks;
5906         struct task_struct *p;
5907         unsigned long load;
5908         int detached = 0;
5909 
5910         lockdep_assert_held(&env->src_rq->lock);
5911 
5912         if (env->imbalance <= 0)
5913                 return 0;
5914 
5915         while (!list_empty(tasks)) {
5916                 /*
5917                  * We don't want to steal all, otherwise we may be treated likewise,
5918                  * which could at worst lead to a livelock crash.
5919                  */
5920                 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
5921                         break;
5922 
5923                 p = list_first_entry(tasks, struct task_struct, se.group_node);
5924 
5925                 env->loop++;
5926                 /* We've more or less seen every task there is, call it quits */
5927                 if (env->loop > env->loop_max)
5928                         break;
5929 
5930                 /* take a breather every nr_migrate tasks */
5931                 if (env->loop > env->loop_break) {
5932                         env->loop_break += sched_nr_migrate_break;
5933                         env->flags |= LBF_NEED_BREAK;
5934                         break;
5935                 }
5936 
5937                 if (!can_migrate_task(p, env))
5938                         goto next;
5939 
5940                 load = task_h_load(p);
5941 
5942                 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5943                         goto next;
5944 
5945                 if ((load / 2) > env->imbalance)
5946                         goto next;
5947 
5948                 detach_task(p, env);
5949                 list_add(&p->se.group_node, &env->tasks);
5950 
5951                 detached++;
5952                 env->imbalance -= load;
5953 
5954 #ifdef CONFIG_PREEMPT
5955                 /*
5956                  * NEWIDLE balancing is a source of latency, so preemptible
5957                  * kernels will stop after the first task is detached to minimize
5958                  * the critical section.
5959                  */
5960                 if (env->idle == CPU_NEWLY_IDLE)
5961                         break;
5962 #endif
5963 
5964                 /*
5965                  * We only want to steal up to the prescribed amount of
5966                  * weighted load.
5967                  */
5968                 if (env->imbalance <= 0)
5969                         break;
5970 
5971                 continue;
5972 next:
5973                 list_move_tail(&p->se.group_node, tasks);
5974         }
5975 
5976         /*
5977          * Right now, this is one of only two places we collect this stat
5978          * so we can safely collect detach_one_task() stats here rather
5979          * than inside detach_one_task().
5980          */
5981         schedstat_add(env->sd, lb_gained[env->idle], detached);
5982 
5983         return detached;
5984 }
5985 
5986 /*
5987  * attach_task() -- attach the task detached by detach_task() to its new rq.
5988  */
5989 static void attach_task(struct rq *rq, struct task_struct *p)
5990 {
5991         lockdep_assert_held(&rq->lock);
5992 
5993         BUG_ON(task_rq(p) != rq);
5994         activate_task(rq, p, 0);
5995         p->on_rq = TASK_ON_RQ_QUEUED;
5996         check_preempt_curr(rq, p, 0);
5997 }
5998 
5999 /*
6000  * attach_one_task() -- attaches the task returned from detach_one_task() to
6001  * its new rq.
6002  */
6003 static void attach_one_task(struct rq *rq, struct task_struct *p)
6004 {
6005         raw_spin_lock(&rq->lock);
6006         attach_task(rq, p);
6007         raw_spin_unlock(&rq->lock);
6008 }
6009 
6010 /*
6011  * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6012  * new rq.
6013  */
6014 static void attach_tasks(struct lb_env *env)
6015 {
6016         struct list_head *tasks = &env->tasks;
6017         struct task_struct *p;
6018 
6019         raw_spin_lock(&env->dst_rq->lock);
6020 
6021         while (!list_empty(tasks)) {
6022                 p = list_first_entry(tasks, struct task_struct, se.group_node);
6023                 list_del_init(&p->se.group_node);
6024 
6025                 attach_task(env->dst_rq, p);
6026         }
6027 
6028         raw_spin_unlock(&env->dst_rq->lock);
6029 }
6030 
6031 #ifdef CONFIG_FAIR_GROUP_SCHED
6032 static void update_blocked_averages(int cpu)
6033 {
6034         struct rq *rq = cpu_rq(cpu);
6035         struct cfs_rq *cfs_rq;
6036         unsigned long flags;
6037 
6038         raw_spin_lock_irqsave(&rq->lock, flags);
6039         update_rq_clock(rq);
6040 
6041         /*
6042          * Iterates the task_group tree in a bottom up fashion, see
6043          * list_add_leaf_cfs_rq() for details.
6044          */
6045         for_each_leaf_cfs_rq(rq, cfs_rq) {
6046                 /* throttled entities do not contribute to load */
6047                 if (throttled_hierarchy(cfs_rq))
6048                         continue;
6049 
6050                 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6051                         update_tg_load_avg(cfs_rq, 0);
6052         }
6053         raw_spin_unlock_irqrestore(&rq->lock, flags);
6054 }
6055 
6056 /*
6057  * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6058  * This needs to be done in a top-down fashion because the load of a child
6059  * group is a fraction of its parents load.
6060  */
6061 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6062 {
6063         struct rq *rq = rq_of(cfs_rq);
6064         struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6065         unsigned long now = jiffies;
6066         unsigned long load;
6067 
6068         if (cfs_rq->last_h_load_update == now)
6069                 return;
6070 
6071         cfs_rq->h_load_next = NULL;
6072         for_each_sched_entity(se) {
6073                 cfs_rq = cfs_rq_of(se);
6074                 cfs_rq->h_load_next = se;
6075                 if (cfs_rq->last_h_load_update == now)
6076                         break;
6077         }
6078 
6079         if (!se) {
6080                 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6081                 cfs_rq->last_h_load_update = now;
6082         }
6083 
6084         while ((se = cfs_rq->h_load_next) != NULL) {
6085                 load = cfs_rq->h_load;
6086                 load = div64_ul(load * se->avg.load_avg,
6087                         cfs_rq_load_avg(cfs_rq) + 1);
6088                 cfs_rq = group_cfs_rq(se);
6089                 cfs_rq->h_load = load;
6090                 cfs_rq->last_h_load_update = now;
6091         }
6092 }
6093 
6094 static unsigned long task_h_load(struct task_struct *p)
6095 {
6096         struct cfs_rq *cfs_rq = task_cfs_rq(p);
6097 
6098         update_cfs_rq_h_load(cfs_rq);
6099         return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6100                         cfs_rq_load_avg(cfs_rq) + 1);
6101 }
6102 #else
6103 static inline void update_blocked_averages(int cpu)
6104 {
6105         struct rq *rq = cpu_rq(cpu);
6106         struct cfs_rq *cfs_rq = &rq->cfs;
6107         unsigned long flags;
6108 
6109         raw_spin_lock_irqsave(&rq->lock, flags);
6110         update_rq_clock(rq);
6111         update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6112         raw_spin_unlock_irqrestore(&rq->lock, flags);
6113 }
6114 
6115 static unsigned long task_h_load(struct task_struct *p)
6116 {
6117         return p->se.avg.load_avg;
6118 }
6119 #endif
6120 
6121 /********** Helpers for find_busiest_group ************************/
6122 
6123 enum group_type {
6124         group_other = 0,
6125         group_imbalanced,
6126         group_overloaded,
6127 };
6128 
6129 /*
6130  * sg_lb_stats - stats of a sched_group required for load_balancing
6131  */
6132 struct sg_lb_stats {
6133         unsigned long avg_load; /*Avg load across the CPUs of the group */
6134         unsigned long group_load; /* Total load over the CPUs of the group */
6135         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6136         unsigned long load_per_task;
6137         unsigned long group_capacity;
6138         unsigned long group_util; /* Total utilization of the group */
6139         unsigned int sum_nr_running; /* Nr tasks running in the group */
6140         unsigned int idle_cpus;
6141         unsigned int group_weight;
6142         enum group_type group_type;
6143         int group_no_capacity;
6144 #ifdef CONFIG_NUMA_BALANCING
6145         unsigned int nr_numa_running;
6146         unsigned int nr_preferred_running;
6147 #endif
6148 };
6149 
6150 /*
6151  * sd_lb_stats - Structure to store the statistics of a sched_domain
6152  *               during load balancing.
6153  */
6154 struct sd_lb_stats {
6155         struct sched_group *busiest;    /* Busiest group in this sd */
6156         struct sched_group *local;      /* Local group in this sd */
6157         unsigned long total_load;       /* Total load of all groups in sd */
6158         unsigned long total_capacity;   /* Total capacity of all groups in sd */
6159         unsigned long avg_load; /* Average load across all groups in sd */
6160 
6161         struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6162         struct sg_lb_stats local_stat;  /* Statistics of the local group */
6163 };
6164 
6165 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6166 {
6167         /*
6168          * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6169          * local_stat because update_sg_lb_stats() does a full clear/assignment.
6170          * We must however clear busiest_stat::avg_load because
6171          * update_sd_pick_busiest() reads this before assignment.
6172          */
6173         *sds = (struct sd_lb_stats){
6174                 .busiest = NULL,
6175                 .local = NULL,
6176                 .total_load = 0UL,
6177                 .total_capacity = 0UL,
6178                 .busiest_stat = {
6179                         .avg_load = 0UL,
6180                         .sum_nr_running = 0,
6181                         .group_type = group_other,
6182                 },
6183         };
6184 }
6185 
6186 /**
6187  * get_sd_load_idx - Obtain the load index for a given sched domain.
6188  * @sd: The sched_domain whose load_idx is to be obtained.
6189  * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6190  *
6191  * Return: The load index.
6192  */
6193 static inline int get_sd_load_idx(struct sched_domain *sd,
6194                                         enum cpu_idle_type idle)
6195 {
6196         int load_idx;
6197 
6198         switch (idle) {
6199         case CPU_NOT_IDLE:
6200                 load_idx = sd->busy_idx;
6201                 break;
6202 
6203         case CPU_NEWLY_IDLE:
6204                 load_idx = sd->newidle_idx;
6205                 break;
6206         default:
6207                 load_idx = sd->idle_idx;
6208                 break;
6209         }
6210 
6211         return load_idx;
6212 }
6213 
6214 static unsigned long scale_rt_capacity(int cpu)
6215 {
6216         struct rq *rq = cpu_rq(cpu);
6217         u64 total, used, age_stamp, avg;
6218         s64 delta;
6219 
6220         /*
6221          * Since we're reading these variables without serialization make sure
6222          * we read them once before doing sanity checks on them.
6223          */
6224         age_stamp = READ_ONCE(rq->age_stamp);
6225         avg = READ_ONCE(rq->rt_avg);
6226         delta = __rq_clock_broken(rq) - age_stamp;
6227 
6228         if (unlikely(delta < 0))
6229                 delta = 0;
6230 
6231         total = sched_avg_period() + delta;
6232 
6233         used = div_u64(avg, total);
6234 
6235         if (likely(used < SCHED_CAPACITY_SCALE))
6236                 return SCHED_CAPACITY_SCALE - used;
6237 
6238         return 1;
6239 }
6240 
6241 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6242 {
6243         unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6244         struct sched_group *sdg = sd->groups;
6245 
6246         cpu_rq(cpu)->cpu_capacity_orig = capacity;
6247 
6248         capacity *= scale_rt_capacity(cpu);
6249         capacity >>= SCHED_CAPACITY_SHIFT;
6250 
6251         if (!capacity)
6252                 capacity = 1;
6253 
6254         cpu_rq(cpu)->cpu_capacity = capacity;
6255         sdg->sgc->capacity = capacity;
6256 }
6257 
6258 void update_group_capacity(struct sched_domain *sd, int cpu)
6259 {
6260         struct sched_domain *child = sd->child;
6261         struct sched_group *group, *sdg = sd->groups;
6262         unsigned long capacity;
6263         unsigned long interval;
6264 
6265         interval = msecs_to_jiffies(sd->balance_interval);
6266         interval = clamp(interval, 1UL, max_load_balance_interval);
6267         sdg->sgc->next_update = jiffies + interval;
6268 
6269         if (!child) {
6270                 update_cpu_capacity(sd, cpu);
6271                 return;
6272         }
6273 
6274         capacity = 0;
6275 
6276         if (child->flags & SD_OVERLAP) {
6277                 /*
6278                  * SD_OVERLAP domains cannot assume that child groups
6279                  * span the current group.
6280                  */
6281 
6282                 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6283                         struct sched_group_capacity *sgc;
6284                         struct rq *rq = cpu_rq(cpu);
6285 
6286                         /*
6287                          * build_sched_domains() -> init_sched_groups_capacity()
6288                          * gets here before we've attached the domains to the
6289                          * runqueues.
6290                          *
6291                          * Use capacity_of(), which is set irrespective of domains
6292                          * in update_cpu_capacity().
6293                          *
6294                          * This avoids capacity from being 0 and
6295                          * causing divide-by-zero issues on boot.
6296                          */
6297                         if (unlikely(!rq->sd)) {
6298                                 capacity += capacity_of(cpu);
6299                                 continue;
6300                         }
6301 
6302                         sgc = rq->sd->groups->sgc;
6303                         capacity += sgc->capacity;
6304                 }
6305         } else  {
6306                 /*
6307                  * !SD_OVERLAP domains can assume that child groups
6308                  * span the current group.
6309                  */ 
6310 
6311                 group = child->groups;
6312                 do {
6313                         capacity += group->sgc->capacity;
6314                         group = group->next;
6315                 } while (group != child->groups);
6316         }
6317 
6318         sdg->sgc->capacity = capacity;
6319 }
6320 
6321 /*
6322  * Check whether the capacity of the rq has been noticeably reduced by side
6323  * activity. The imbalance_pct is used for the threshold.
6324  * Return true is the capacity is reduced
6325  */
6326 static inline int
6327 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6328 {
6329         return ((rq->cpu_capacity * sd->imbalance_pct) <
6330                                 (rq->cpu_capacity_orig * 100));
6331 }
6332 
6333 /*
6334  * Group imbalance indicates (and tries to solve) the problem where balancing
6335  * groups is inadequate due to tsk_cpus_allowed() constraints.
6336  *
6337  * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6338  * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6339  * Something like:
6340  *
6341  *      { 0 1 2 3 } { 4 5 6 7 }
6342  *              *     * * *
6343  *
6344  * If we were to balance group-wise we'd place two tasks in the first group and
6345  * two tasks in the second group. Clearly this is undesired as it will overload
6346  * cpu 3 and leave one of the cpus in the second group unused.
6347  *
6348  * The current solution to this issue is detecting the skew in the first group
6349  * by noticing the lower domain failed to reach balance and had difficulty
6350  * moving tasks due to affinity constraints.
6351  *
6352  * When this is so detected; this group becomes a candidate for busiest; see
6353  * update_sd_pick_busiest(). And calculate_imbalance() and
6354  * find_busiest_group() avoid some of the usual balance conditions to allow it
6355  * to create an effective group imbalance.
6356  *
6357  * This is a somewhat tricky proposition since the next run might not find the
6358  * group imbalance and decide the groups need to be balanced again. A most
6359  * subtle and fragile situation.
6360  */
6361 
6362 static inline int sg_imbalanced(struct sched_group *group)
6363 {
6364         return group->sgc->imbalance;
6365 }
6366 
6367 /*
6368  * group_has_capacity returns true if the group has spare capacity that could
6369  * be used by some tasks.
6370  * We consider that a group has spare capacity if the  * number of task is
6371  * smaller than the number of CPUs or if the utilization is lower than the
6372  * available capacity for CFS tasks.
6373  * For the latter, we use a threshold to stabilize the state, to take into
6374  * account the variance of the tasks' load and to return true if the available
6375  * capacity in meaningful for the load balancer.
6376  * As an example, an available capacity of 1% can appear but it doesn't make
6377  * any benefit for the load balance.
6378  */
6379 static inline bool
6380 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6381 {
6382         if (sgs->sum_nr_running < sgs->group_weight)
6383                 return true;
6384 
6385         if ((sgs->group_capacity * 100) >
6386                         (sgs->group_util * env->sd->imbalance_pct))
6387                 return true;
6388 
6389         return false;
6390 }
6391 
6392 /*
6393  *  group_is_overloaded returns true if the group has more tasks than it can
6394  *  handle.
6395  *  group_is_overloaded is not equals to !group_has_capacity because a group
6396  *  with the exact right number of tasks, has no more spare capacity but is not
6397  *  overloaded so both group_has_capacity and group_is_overloaded return
6398  *  false.
6399  */
6400 static inline bool
6401 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6402 {
6403         if (sgs->sum_nr_running <= sgs->group_weight)
6404                 return false;
6405 
6406         if ((sgs->group_capacity * 100) <
6407                         (sgs->group_util * env->sd->imbalance_pct))
6408                 return true;
6409 
6410         return false;
6411 }
6412 
6413 static inline enum
6414 group_type group_classify(struct sched_group *group,
6415                           struct sg_lb_stats *sgs)
6416 {
6417         if (sgs->group_no_capacity)
6418                 return group_overloaded;
6419 
6420         if (sg_imbalanced(group))
6421                 return group_imbalanced;
6422 
6423         return group_other;
6424 }
6425 
6426 /**
6427  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6428  * @env: The load balancing environment.
6429  * @group: sched_group whose statistics are to be updated.
6430  * @load_idx: Load index of sched_domain of this_cpu for load calc.
6431  * @local_group: Does group contain this_cpu.
6432  * @sgs: variable to hold the statistics for this group.
6433  * @overload: Indicate more than one runnable task for any CPU.
6434  */
6435 static inline void update_sg_lb_stats(struct lb_env *env,
6436                         struct sched_group *group, int load_idx,
6437                         int local_group, struct sg_lb_stats *sgs,
6438                         bool *overload)
6439 {
6440         unsigned long load;
6441         int i, nr_running;
6442 
6443         memset(sgs, 0, sizeof(*sgs));
6444 
6445         for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6446                 struct rq *rq = cpu_rq(i);
6447 
6448                 /* Bias balancing toward cpus of our domain */
6449                 if (local_group)
6450                         load = target_load(i, load_idx);
6451                 else
6452                         load = source_load(i, load_idx);
6453 
6454                 sgs->group_load += load;
6455                 sgs->group_util += cpu_util(i);
6456                 sgs->sum_nr_running += rq->cfs.h_nr_running;
6457 
6458                 nr_running = rq->nr_running;
6459                 if (nr_running > 1)
6460                         *overload = true;
6461 
6462 #ifdef CONFIG_NUMA_BALANCING
6463                 sgs->nr_numa_running += rq->nr_numa_running;
6464                 sgs->nr_preferred_running += rq->nr_preferred_running;
6465 #endif
6466                 sgs->sum_weighted_load += weighted_cpuload(i);
6467                 /*
6468                  * No need to call idle_cpu() if nr_running is not 0
6469                  */
6470                 if (!nr_running && idle_cpu(i))
6471                         sgs->idle_cpus++;
6472         }
6473 
6474         /* Adjust by relative CPU capacity of the group */
6475         sgs->group_capacity = group->sgc->capacity;
6476         sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6477 
6478         if (sgs->sum_nr_running)
6479                 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6480 
6481         sgs->group_weight = group->group_weight;
6482 
6483         sgs->group_no_capacity = group_is_overloaded(env, sgs);
6484         sgs->group_type = group_classify(group, sgs);
6485 }
6486 
6487 /**
6488  * update_sd_pick_busiest - return 1 on busiest group
6489  * @env: The load balancing environment.
6490  * @sds: sched_domain statistics
6491  * @sg: sched_group candidate to be checked for being the busiest
6492  * @sgs: sched_group statistics
6493  *
6494  * Determine if @sg is a busier group than the previously selected
6495  * busiest group.
6496  *
6497  * Return: %true if @sg is a busier group than the previously selected
6498  * busiest group. %false otherwise.
6499  */
6500 static bool update_sd_pick_busiest(struct lb_env *env,
6501                                    struct sd_lb_stats *sds,
6502                                    struct sched_group *sg,
6503                                    struct sg_lb_stats *sgs)
6504 {
6505         struct sg_lb_stats *busiest = &sds->busiest_stat;
6506 
6507         if (sgs->group_type > busiest->group_type)
6508                 return true;
6509 
6510         if (sgs->group_type < busiest->group_type)
6511                 return false;
6512 
6513         if (sgs->avg_load <= busiest->avg_load)
6514                 return false;
6515 
6516         /* This is the busiest node in its class. */
6517         if (!(env->sd->flags & SD_ASYM_PACKING))
6518                 return true;
6519 
6520         /*
6521          * ASYM_PACKING needs to move all the work to the lowest
6522          * numbered CPUs in the group, therefore mark all groups
6523          * higher than ourself as busy.
6524          */
6525         if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6526                 if (!sds->busiest)
6527                         return true;
6528 
6529                 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6530                         return true;
6531         }
6532 
6533         return false;
6534 }
6535 
6536 #ifdef CONFIG_NUMA_BALANCING
6537 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6538 {
6539         if (sgs->sum_nr_running > sgs->nr_numa_running)
6540                 return regular;
6541         if (sgs->sum_nr_running > sgs->nr_preferred_running)
6542                 return remote;
6543         return all;
6544 }
6545 
6546 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6547 {
6548         if (rq->nr_running > rq->nr_numa_running)
6549                 return regular;
6550         if (rq->nr_running > rq->nr_preferred_running)
6551                 return remote;
6552         return all;
6553 }
6554 #else
6555 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6556 {
6557         return all;
6558 }
6559 
6560 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6561 {
6562         return regular;
6563 }
6564 #endif /* CONFIG_NUMA_BALANCING */
6565 
6566 /**
6567  * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6568  * @env: The load balancing environment.
6569  * @sds: variable to hold the statistics for this sched_domain.
6570  */
6571 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6572 {
6573         struct sched_domain *child = env->sd->child;
6574         struct sched_group *sg = env->sd->groups;
6575         struct sg_lb_stats tmp_sgs;
6576         int load_idx, prefer_sibling = 0;
6577         bool overload = false;
6578 
6579         if (child && child->flags & SD_PREFER_SIBLING)
6580                 prefer_sibling = 1;
6581 
6582         load_idx = get_sd_load_idx(env->sd, env->idle);
6583 
6584         do {
6585                 struct sg_lb_stats *sgs = &tmp_sgs;
6586                 int local_group;
6587 
6588                 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6589                 if (local_group) {
6590                         sds->local = sg;
6591                         sgs = &sds->local_stat;
6592 
6593                         if (env->idle != CPU_NEWLY_IDLE ||
6594                             time_after_eq(jiffies, sg->sgc->next_update))
6595                                 update_group_capacity(env->sd, env->dst_cpu);
6596                 }
6597 
6598                 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6599                                                 &overload);
6600 
6601                 if (local_group)
6602                         goto next_group;
6603 
6604                 /*
6605                  * In case the child domain prefers tasks go to siblings
6606                  * first, lower the sg capacity so that we'll try
6607                  * and move all the excess tasks away. We lower the capacity
6608                  * of a group only if the local group has the capacity to fit
6609                  * these excess tasks. The extra check prevents the case where
6610                  * you always pull from the heaviest group when it is already
6611                  * under-utilized (possible with a large weight task outweighs
6612                  * the tasks on the system).
6613                  */
6614                 if (prefer_sibling && sds->local &&
6615                     group_has_capacity(env, &sds->local_stat) &&
6616                     (sgs->sum_nr_running > 1)) {
6617                         sgs->group_no_capacity = 1;
6618                         sgs->group_type = group_classify(sg, sgs);
6619                 }
6620 
6621                 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6622                         sds->busiest = sg;
6623                         sds->busiest_stat = *sgs;
6624                 }
6625 
6626 next_group:
6627                 /* Now, start updating sd_lb_stats */
6628                 sds->total_load += sgs->group_load;
6629                 sds->total_capacity += sgs->group_capacity;
6630 
6631                 sg = sg->next;
6632         } while (sg != env->sd->groups);
6633 
6634         if (env->sd->flags & SD_NUMA)
6635                 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6636 
6637         if (!env->sd->parent) {
6638                 /* update overload indicator if we are at root domain */
6639                 if (env->dst_rq->rd->overload != overload)
6640                         env->dst_rq->rd->overload = overload;
6641         }
6642 
6643 }
6644 
6645 /**
6646  * check_asym_packing - Check to see if the group is packed into the
6647  *                      sched doman.
6648  *
6649  * This is primarily intended to used at the sibling level.  Some
6650  * cores like POWER7 prefer to use lower numbered SMT threads.  In the
6651  * case of POWER7, it can move to lower SMT modes only when higher
6652  * threads are idle.  When in lower SMT modes, the threads will
6653  * perform better since they share less core resources.  Hence when we
6654  * have idle threads, we want them to be the higher ones.
6655  *
6656  * This packing function is run on idle threads.  It checks to see if
6657  * the busiest CPU in this domain (core in the P7 case) has a higher
6658  * CPU number than the packing function is being run on.  Here we are
6659  * assuming lower CPU number will be equivalent to lower a SMT thread
6660  * number.
6661  *
6662  * Return: 1 when packing is required and a task should be moved to
6663  * this CPU.  The amount of the imbalance is returned in *imbalance.
6664  *
6665  * @env: The load balancing environment.
6666  * @sds: Statistics of the sched_domain which is to be packed
6667  */
6668 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6669 {
6670         int busiest_cpu;
6671 
6672         if (!(env->sd->flags & SD_ASYM_PACKING))
6673                 return 0;
6674 
6675         if (!sds->busiest)
6676                 return 0;
6677 
6678         busiest_cpu = group_first_cpu(sds->busiest);
6679         if (env->dst_cpu > busiest_cpu)
6680                 return 0;
6681 
6682         env->imbalance = DIV_ROUND_CLOSEST(
6683                 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6684                 SCHED_CAPACITY_SCALE);
6685 
6686         return 1;
6687 }
6688 
6689 /**
6690  * fix_small_imbalance - Calculate the minor imbalance that exists
6691  *                      amongst the groups of a sched_domain, during
6692  *                      load balancing.
6693  * @env: The load balancing environment.
6694  * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6695  */
6696 static inline
6697 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6698 {
6699         unsigned long tmp, capa_now = 0, capa_move = 0;
6700         unsigned int imbn = 2;
6701         unsigned long scaled_busy_load_per_task;
6702         struct sg_lb_stats *local, *busiest;
6703 
6704         local = &sds->local_stat;
6705         busiest = &sds->busiest_stat;
6706 
6707         if (!local->sum_nr_running)
6708                 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6709         else if (busiest->load_per_task > local->load_per_task)
6710                 imbn = 1;
6711 
6712         scaled_busy_load_per_task =
6713                 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6714                 busiest->group_capacity;
6715 
6716         if (busiest->avg_load + scaled_busy_load_per_task >=
6717             local->avg_load + (scaled_busy_load_per_task * imbn)) {
6718                 env->imbalance = busiest->load_per_task;
6719                 return;
6720         }
6721 
6722         /*
6723          * OK, we don't have enough imbalance to justify moving tasks,
6724          * however we may be able to increase total CPU capacity used by
6725          * moving them.
6726          */
6727 
6728         capa_now += busiest->group_capacity *
6729                         min(busiest->load_per_task, busiest->avg_load);
6730         capa_now += local->group_capacity *
6731                         min(local->load_per_task, local->avg_load);
6732         capa_now /= SCHED_CAPACITY_SCALE;
6733 
6734         /* Amount of load we'd subtract */
6735         if (busiest->avg_load > scaled_busy_load_per_task) {
6736                 capa_move += busiest->group_capacity *
6737                             min(busiest->load_per_task,
6738                                 busiest->avg_load - scaled_busy_load_per_task);
6739         }
6740 
6741         /* Amount of load we'd add */
6742         if (busiest->avg_load * busiest->group_capacity <
6743             busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6744                 tmp = (busiest->avg_load * busiest->group_capacity) /
6745                       local->group_capacity;
6746         } else {
6747                 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6748                       local->group_capacity;
6749         }
6750         capa_move += local->group_capacity *
6751                     min(local->load_per_task, local->avg_load + tmp);
6752         capa_move /= SCHED_CAPACITY_SCALE;
6753 
6754         /* Move if we gain throughput */
6755         if (capa_move > capa_now)
6756                 env->imbalance = busiest->load_per_task;
6757 }
6758 
6759 /**
6760  * calculate_imbalance - Calculate the amount of imbalance present within the
6761  *                       groups of a given sched_domain during load balance.
6762  * @env: load balance environment
6763  * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6764  */
6765 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6766 {
6767         unsigned long max_pull, load_above_capacity = ~0UL;
6768         struct sg_lb_stats *local, *busiest;
6769 
6770         local = &sds->local_stat;
6771         busiest = &sds->busiest_stat;
6772 
6773         if (busiest->group_type == group_imbalanced) {
6774                 /*
6775                  * In the group_imb case we cannot rely on group-wide averages
6776                  * to ensure cpu-load equilibrium, look at wider averages. XXX
6777                  */
6778                 busiest->load_per_task =
6779                         min(busiest->load_per_task, sds->avg_load);
6780         }
6781 
6782         /*
6783          * In the presence of smp nice balancing, certain scenarios can have
6784          * max load less than avg load(as we skip the groups at or below
6785          * its cpu_capacity, while calculating max_load..)
6786          */
6787         if (busiest->avg_load <= sds->avg_load ||
6788             local->avg_load >= sds->avg_load) {
6789                 env->imbalance = 0;
6790                 return fix_small_imbalance(env, sds);
6791         }
6792 
6793         /*
6794          * If there aren't any idle cpus, avoid creating some.
6795          */
6796         if (busiest->group_type == group_overloaded &&
6797             local->group_type   == group_overloaded) {
6798                 load_above_capacity = busiest->sum_nr_running *
6799                                         SCHED_LOAD_SCALE;
6800                 if (load_above_capacity > busiest->group_capacity)
6801                         load_above_capacity -= busiest->group_capacity;
6802                 else
6803                         load_above_capacity = ~0UL;
6804         }
6805 
6806         /*
6807          * We're trying to get all the cpus to the average_load, so we don't
6808          * want to push ourselves above the average load, nor do we wish to
6809          * reduce the max loaded cpu below the average load. At the same time,
6810          * we also don't want to reduce the group load below the group capacity
6811          * (so that we can implement power-savings policies etc). Thus we look
6812          * for the minimum possible imbalance.
6813          */
6814         max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6815 
6816         /* How much load to actually move to equalise the imbalance */
6817         env->imbalance = min(
6818                 max_pull * busiest->group_capacity,
6819                 (sds->avg_load - local->avg_load) * local->group_capacity
6820         ) / SCHED_CAPACITY_SCALE;
6821 
6822         /*
6823          * if *imbalance is less than the average load per runnable task
6824          * there is no guarantee that any tasks will be moved so we'll have
6825          * a think about bumping its value to force at least one task to be
6826          * moved
6827          */
6828         if (env->imbalance < busiest->load_per_task)
6829                 return fix_small_imbalance(env, sds);
6830 }
6831 
6832 /******* find_busiest_group() helpers end here *********************/
6833 
6834 /**
6835  * find_busiest_group - Returns the busiest group within the sched_domain
6836  * if there is an imbalance. If there isn't an imbalance, and
6837  * the user has opted for power-savings, it returns a group whose
6838  * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6839  * such a group exists.
6840  *
6841  * Also calculates the amount of weighted load which should be moved
6842  * to restore balance.
6843  *
6844  * @env: The load balancing environment.
6845  *
6846  * Return:      - The busiest group if imbalance exists.
6847  *              - If no imbalance and user has opted for power-savings balance,
6848  *                 return the least loaded group whose CPUs can be
6849  *                 put to idle by rebalancing its tasks onto our group.
6850  */
6851 static struct sched_group *find_busiest_group(struct lb_env *env)
6852 {
6853         struct sg_lb_stats *local, *busiest;
6854         struct sd_lb_stats sds;
6855 
6856         init_sd_lb_stats(&sds);
6857 
6858         /*
6859          * Compute the various statistics relavent for load balancing at
6860          * this level.
6861          */
6862         update_sd_lb_stats(env, &sds);
6863         local = &sds.local_stat;
6864         busiest = &sds.busiest_stat;
6865 
6866         /* ASYM feature bypasses nice load balance check */
6867         if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6868             check_asym_packing(env, &sds))
6869                 return sds.busiest;
6870 
6871         /* There is no busy sibling group to pull tasks from */
6872         if (!sds.busiest || busiest->sum_nr_running == 0)
6873                 goto out_balanced;
6874 
6875         sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6876                                                 / sds.total_capacity;
6877 
6878         /*
6879          * If the busiest group is imbalanced the below checks don't
6880          * work because they assume all things are equal, which typically
6881          * isn't true due to cpus_allowed constraints and the like.
6882          */
6883         if (busiest->group_type == group_imbalanced)
6884                 goto force_balance;
6885 
6886         /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6887         if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6888             busiest->group_no_capacity)
6889                 goto force_balance;
6890 
6891         /*
6892          * If the local group is busier than the selected busiest group
6893          * don't try and pull any tasks.
6894          */
6895         if (local->avg_load >= busiest->avg_load)
6896                 goto out_balanced;
6897 
6898         /*
6899          * Don't pull any tasks if this group is already above the domain
6900          * average load.
6901          */
6902         if (local->avg_load >= sds.avg_load)
6903                 goto out_balanced;
6904 
6905         if (env->idle == CPU_IDLE) {
6906                 /*
6907                  * This cpu is idle. If the busiest group is not overloaded
6908                  * and there is no imbalance between this and busiest group
6909                  * wrt idle cpus, it is balanced. The imbalance becomes
6910                  * significant if the diff is greater than 1 otherwise we
6911                  * might end up to just move the imbalance on another group
6912                  */
6913                 if ((busiest->group_type != group_overloaded) &&
6914                                 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6915                         goto out_balanced;
6916         } else {
6917                 /*
6918                  * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6919                  * imbalance_pct to be conservative.
6920                  */
6921                 if (100 * busiest->avg_load <=
6922                                 env->sd->imbalance_pct * local->avg_load)
6923                         goto out_balanced;
6924         }
6925 
6926 force_balance:
6927         /* Looks like there is an imbalance. Compute it */
6928         calculate_imbalance(env, &sds);
6929         return sds.busiest;
6930 
6931 out_balanced:
6932         env->imbalance = 0;
6933         return NULL;
6934 }
6935 
6936 /*
6937  * find_busiest_queue - find the busiest runqueue among the cpus in group.
6938  */
6939 static struct rq *find_busiest_queue(struct lb_env *env,
6940                                      struct sched_group *group)
6941 {
6942         struct rq *busiest = NULL, *rq;
6943         unsigned long busiest_load = 0, busiest_capacity = 1;
6944         int i;
6945 
6946         for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6947                 unsigned long capacity, wl;
6948                 enum fbq_type rt;
6949 
6950                 rq = cpu_rq(i);
6951                 rt = fbq_classify_rq(rq);
6952 
6953                 /*
6954                  * We classify groups/runqueues into three groups:
6955                  *  - regular: there are !numa tasks
6956                  *  - remote:  there are numa tasks that run on the 'wrong' node
6957                  *  - all:     there is no distinction
6958                  *
6959                  * In order to avoid migrating ideally placed numa tasks,
6960                  * ignore those when there's better options.
6961                  *
6962                  * If we ignore the actual busiest queue to migrate another
6963                  * task, the next balance pass can still reduce the busiest
6964                  * queue by moving tasks around inside the node.
6965                  *
6966                  * If we cannot move enough load due to this classification
6967                  * the next pass will adjust the group classification and
6968                  * allow migration of more tasks.
6969                  *
6970                  * Both cases only affect the total convergence complexity.
6971                  */
6972                 if (rt > env->fbq_type)
6973                         continue;
6974 
6975                 capacity = capacity_of(i);
6976 
6977                 wl = weighted_cpuload(i);
6978 
6979                 /*
6980                  * When comparing with imbalance, use weighted_cpuload()
6981                  * which is not scaled with the cpu capacity.
6982                  */
6983 
6984                 if (rq->nr_running == 1 && wl > env->imbalance &&
6985                     !check_cpu_capacity(rq, env->sd))
6986                         continue;
6987 
6988                 /*
6989                  * For the load comparisons with the other cpu's, consider
6990                  * the weighted_cpuload() scaled with the cpu capacity, so
6991                  * that the load can be moved away from the cpu that is
6992                  * potentially running at a lower capacity.
6993                  *
6994                  * Thus we're looking for max(wl_i / capacity_i), crosswise
6995                  * multiplication to rid ourselves of the division works out
6996                  * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
6997                  * our previous maximum.
6998                  */
6999                 if (wl * busiest_capacity > busiest_load * capacity) {
7000                         busiest_load = wl;
7001                         busiest_capacity = capacity;
7002                         busiest = rq;
7003                 }
7004         }
7005 
7006         return busiest;
7007 }
7008 
7009 /*
7010  * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7011  * so long as it is large enough.
7012  */
7013 #define MAX_PINNED_INTERVAL     512
7014 
7015 /* Working cpumask for load_balance and load_balance_newidle. */
7016 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7017 
7018 static int need_active_balance(struct lb_env *env)
7019 {
7020         struct sched_domain *sd = env->sd;
7021 
7022         if (env->idle == CPU_NEWLY_IDLE) {
7023 
7024                 /*
7025                  * ASYM_PACKING needs to force migrate tasks from busy but
7026                  * higher numbered CPUs in order to pack all tasks in the
7027                  * lowest numbered CPUs.
7028                  */
7029                 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7030                         return 1;
7031         }
7032 
7033         /*
7034          * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7035          * It's worth migrating the task if the src_cpu's capacity is reduced
7036          * because of other sched_class or IRQs if more capacity stays
7037          * available on dst_cpu.
7038          */
7039         if ((env->idle != CPU_NOT_IDLE) &&
7040             (env->src_rq->cfs.h_nr_running == 1)) {
7041                 if ((check_cpu_capacity(env->src_rq, sd)) &&
7042                     (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7043                         return 1;
7044         }
7045 
7046         return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7047 }
7048 
7049 static int active_load_balance_cpu_stop(void *data);
7050 
7051 static int should_we_balance(struct lb_env *env)
7052 {
7053         struct sched_group *sg = env->sd->groups;
7054         struct cpumask *sg_cpus, *sg_mask;
7055         int cpu, balance_cpu = -1;
7056 
7057         /*
7058          * In the newly idle case, we will allow all the cpu's
7059          * to do the newly idle load balance.
7060          */
7061         if (env->idle == CPU_NEWLY_IDLE)
7062                 return 1;
7063 
7064         sg_cpus = sched_group_cpus(sg);
7065         sg_mask = sched_group_mask(sg);
7066         /* Try to find first idle cpu */
7067         for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7068                 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7069                         continue;
7070 
7071                 balance_cpu = cpu;
7072                 break;
7073         }
7074 
7075         if (balance_cpu == -1)
7076                 balance_cpu = group_balance_cpu(sg);
7077 
7078         /*
7079          * First idle cpu or the first cpu(busiest) in this sched group
7080          * is eligible for doing load balancing at this and above domains.
7081          */
7082         return balance_cpu == env->dst_cpu;
7083 }
7084 
7085 /*
7086  * Check this_cpu to ensure it is balanced within domain. Attempt to move
7087  * tasks if there is an imbalance.
7088  */
7089 static int load_balance(int this_cpu, struct rq *this_rq,
7090                         struct sched_domain *sd, enum cpu_idle_type idle,
7091                         int *continue_balancing)
7092 {
7093         int ld_moved, cur_ld_moved, active_balance = 0;
7094         struct sched_domain *sd_parent = sd->parent;
7095         struct sched_group *group;
7096         struct rq *busiest;
7097         unsigned long flags;
7098         struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7099 
7100         struct lb_env env = {
7101                 .sd             = sd,
7102                 .dst_cpu        = this_cpu,
7103                 .dst_rq         = this_rq,
7104                 .dst_grpmask    = sched_group_cpus(sd->groups),
7105                 .idle           = idle,
7106                 .loop_break     = sched_nr_migrate_break,
7107                 .cpus           = cpus,
7108                 .fbq_type       = all,
7109                 .tasks          = LIST_HEAD_INIT(env.tasks),
7110         };
7111 
7112         /*
7113          * For NEWLY_IDLE load_balancing, we don't need to consider
7114          * other cpus in our group
7115          */
7116         if (idle == CPU_NEWLY_IDLE)
7117                 env.dst_grpmask = NULL;
7118 
7119         cpumask_copy(cpus, cpu_active_mask);
7120 
7121         schedstat_inc(sd, lb_count[idle]);
7122 
7123 redo:
7124         if (!should_we_balance(&env)) {
7125                 *continue_balancing = 0;
7126                 goto out_balanced;
7127         }
7128 
7129         group = find_busiest_group(&env);
7130         if (!group) {
7131                 schedstat_inc(sd, lb_nobusyg[idle]);
7132                 goto out_balanced;
7133         }
7134 
7135         busiest = find_busiest_queue(&env, group);
7136         if (!busiest) {
7137                 schedstat_inc(sd, lb_nobusyq[idle]);
7138                 goto out_balanced;
7139         }
7140 
7141         BUG_ON(busiest == env.dst_rq);
7142 
7143         schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7144 
7145         env.src_cpu = busiest->cpu;
7146         env.src_rq = busiest;
7147 
7148         ld_moved = 0;
7149         if (busiest->nr_running > 1) {
7150                 /*
7151                  * Attempt to move tasks. If find_busiest_group has found
7152                  * an imbalance but busiest->nr_running <= 1, the group is
7153                  * still unbalanced. ld_moved simply stays zero, so it is
7154                  * correctly treated as an imbalance.
7155                  */
7156                 env.flags |= LBF_ALL_PINNED;
7157                 env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7158 
7159 more_balance:
7160                 raw_spin_lock_irqsave(&busiest->lock, flags);
7161 
7162                 /*
7163                  * cur_ld_moved - load moved in current iteration
7164                  * ld_moved     - cumulative load moved across iterations
7165                  */
7166                 cur_ld_moved = detach_tasks(&env);
7167 
7168                 /*
7169                  * We've detached some tasks from busiest_rq. Every
7170                  * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7171                  * unlock busiest->lock, and we are able to be sure
7172                  * that nobody can manipulate the tasks in parallel.
7173                  * See task_rq_lock() family for the details.
7174                  */
7175 
7176                 raw_spin_unlock(&busiest->lock);
7177 
7178                 if (cur_ld_moved) {
7179                         attach_tasks(&env);
7180                         ld_moved += cur_ld_moved;
7181                 }
7182 
7183                 local_irq_restore(flags);
7184 
7185                 if (env.flags & LBF_NEED_BREAK) {
7186                         env.flags &= ~LBF_NEED_BREAK;
7187                         goto more_balance;
7188                 }
7189 
7190                 /*
7191                  * Revisit (affine) tasks on src_cpu that couldn't be moved to
7192                  * us and move them to an alternate dst_cpu in our sched_group
7193                  * where they can run. The upper limit on how many times we
7194                  * iterate on same src_cpu is dependent on number of cpus in our
7195                  * sched_group.
7196                  *
7197                  * This changes load balance semantics a bit on who can move
7198                  * load to a given_cpu. In addition to the given_cpu itself
7199                  * (or a ilb_cpu acting on its behalf where given_cpu is
7200                  * nohz-idle), we now have balance_cpu in a position to move
7201                  * load to given_cpu. In rare situations, this may cause
7202                  * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7203                  * _independently_ and at _same_ time to move some load to
7204                  * given_cpu) causing exceess load to be moved to given_cpu.
7205                  * This however should not happen so much in practice and
7206                  * moreover subsequent load balance cycles should correct the
7207                  * excess load moved.
7208                  */
7209                 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7210 
7211                         /* Prevent to re-select dst_cpu via env's cpus */
7212                         cpumask_clear_cpu(env.dst_cpu, env.cpus);
7213 
7214                         env.dst_rq       = cpu_rq(env.new_dst_cpu);
7215                         env.dst_cpu      = env.new_dst_cpu;
7216                         env.flags       &= ~LBF_DST_PINNED;
7217                         env.loop         = 0;
7218                         env.loop_break   = sched_nr_migrate_break;
7219 
7220                         /*
7221                          * Go back to "more_balance" rather than "redo" since we
7222                          * need to continue with same src_cpu.
7223                          */
7224                         goto more_balance;
7225                 }
7226 
7227                 /*
7228                  * We failed to reach balance because of affinity.
7229                  */
7230                 if (sd_parent) {
7231                         int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7232 
7233                         if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7234                                 *group_imbalance = 1;
7235                 }
7236 
7237                 /* All tasks on this runqueue were pinned by CPU affinity */
7238                 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7239                         cpumask_clear_cpu(cpu_of(busiest), cpus);
7240                         if (!cpumask_empty(cpus)) {
7241                                 env.loop = 0;
7242                                 env.loop_break = sched_nr_migrate_break;
7243                                 goto redo;
7244                         }
7245                         goto out_all_pinned;
7246                 }
7247         }
7248 
7249         if (!ld_moved) {
7250                 schedstat_inc(sd, lb_failed[idle]);
7251                 /*
7252                  * Increment the failure counter only on periodic balance.
7253                  * We do not want newidle balance, which can be very
7254                  * frequent, pollute the failure counter causing
7255                  * excessive cache_hot migrations and active balances.
7256                  */
7257                 if (idle != CPU_NEWLY_IDLE)
7258                         sd->nr_balance_failed++;
7259 
7260                 if (need_active_balance(&env)) {
7261                         raw_spin_lock_irqsave(&busiest->lock, flags);
7262 
7263                         /* don't kick the active_load_balance_cpu_stop,
7264                          * if the curr task on busiest cpu can't be
7265                          * moved to this_cpu
7266                          */
7267                         if (!cpumask_test_cpu(this_cpu,
7268                                         tsk_cpus_allowed(busiest->curr))) {
7269                                 raw_spin_unlock_irqrestore(&busiest->lock,
7270                                                             flags);
7271                                 env.flags |= LBF_ALL_PINNED;
7272                                 goto out_one_pinned;
7273                         }
7274 
7275                         /*
7276                          * ->active_balance synchronizes accesses to
7277                          * ->active_balance_work.  Once set, it's cleared
7278                          * only after active load balance is finished.
7279                          */
7280                         if (!busiest->active_balance) {
7281                                 busiest->active_balance = 1;
7282                                 busiest->push_cpu = this_cpu;
7283                                 active_balance = 1;
7284                         }
7285                         raw_spin_unlock_irqrestore(&busiest->lock, flags);
7286 
7287                         if (active_balance) {
7288                                 stop_one_cpu_nowait(cpu_of(busiest),
7289                                         active_load_balance_cpu_stop, busiest,
7290                                         &busiest->active_balance_work);
7291                         }
7292 
7293                         /*
7294                          * We've kicked active balancing, reset the failure
7295                          * counter.
7296                          */
7297                         sd->nr_balance_failed = sd->cache_nice_tries+1;
7298                 }
7299         } else
7300                 sd->nr_balance_failed = 0;
7301 
7302         if (likely(!active_balance)) {
7303                 /* We were unbalanced, so reset the balancing interval */
7304                 sd->balance_interval = sd->min_interval;
7305         } else {
7306                 /*
7307                  * If we've begun active balancing, start to back off. This
7308                  * case may not be covered by the all_pinned logic if there
7309                  * is only 1 task on the busy runqueue (because we don't call
7310                  * detach_tasks).
7311                  */
7312                 if (sd->balance_interval < sd->max_interval)
7313                         sd->balance_interval *= 2;
7314         }
7315 
7316         goto out;
7317 
7318 out_balanced:
7319         /*
7320          * We reach balance although we may have faced some affinity
7321          * constraints. Clear the imbalance flag if it was set.
7322          */
7323         if (sd_parent) {
7324                 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7325 
7326                 if (*group_imbalance)
7327                         *group_imbalance = 0;
7328         }
7329 
7330 out_all_pinned:
7331         /*
7332          * We reach balance because all tasks are pinned at this level so
7333          * we can't migrate them. Let the imbalance flag set so parent level
7334          * can try to migrate them.
7335          */
7336         schedstat_inc(sd, lb_balanced[idle]);
7337 
7338         sd->nr_balance_failed = 0;
7339 
7340 out_one_pinned:
7341         /* tune up the balancing interval */
7342         if (((env.flags & LBF_ALL_PINNED) &&
7343                         sd->balance_interval < MAX_PINNED_INTERVAL) ||
7344                         (sd->balance_interval < sd->max_interval))
7345                 sd->balance_interval *= 2;
7346 
7347         ld_moved = 0;
7348 out:
7349         return ld_moved;
7350 }
7351 
7352 static inline unsigned long
7353 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7354 {
7355         unsigned long interval = sd->balance_interval;
7356 
7357         if (cpu_busy)
7358                 interval *= sd->busy_factor;
7359 
7360         /* scale ms to jiffies */
7361         interval = msecs_to_jiffies(interval);
7362         interval = clamp(interval, 1UL, max_load_balance_interval);
7363 
7364         return interval;
7365 }
7366 
7367 static inline void
7368 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7369 {
7370         unsigned long interval, next;
7371 
7372         interval = get_sd_balance_interval(sd, cpu_busy);
7373         next = sd->last_balance + interval;
7374 
7375         if (time_after(*next_balance, next))
7376                 *next_balance = next;
7377 }
7378 
7379 /*
7380  * idle_balance is called by schedule() if this_cpu is about to become
7381  * idle. Attempts to pull tasks from other CPUs.
7382  */
7383 static int idle_balance(struct rq *this_rq)
7384 {
7385         unsigned long next_balance = jiffies + HZ;
7386         int this_cpu = this_rq->cpu;
7387         struct sched_domain *sd;
7388         int pulled_task = 0;
7389         u64 curr_cost = 0;
7390 
7391         /*
7392          * We must set idle_stamp _before_ calling idle_balance(), such that we
7393          * measure the duration of idle_balance() as idle time.
7394          */
7395         this_rq->idle_stamp = rq_clock(this_rq);
7396 
7397         if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7398             !this_rq->rd->overload) {
7399                 rcu_read_lock();
7400                 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7401                 if (sd)
7402                         update_next_balance(sd, 0, &next_balance);
7403                 rcu_read_unlock();
7404 
7405                 goto out;
7406         }
7407 
7408         raw_spin_unlock(&this_rq->lock);
7409 
7410         update_blocked_averages(this_cpu);
7411         rcu_read_lock();
7412         for_each_domain(this_cpu, sd) {
7413                 int continue_balancing = 1;
7414                 u64 t0, domain_cost;
7415 
7416                 if (!(sd->flags & SD_LOAD_BALANCE))
7417                         continue;
7418 
7419                 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7420                         update_next_balance(sd, 0, &next_balance);
7421                         break;
7422                 }
7423 
7424                 if (sd->flags & SD_BALANCE_NEWIDLE) {
7425                         t0 = sched_clock_cpu(this_cpu);
7426 
7427                         pulled_task = load_balance(this_cpu, this_rq,
7428                                                    sd, CPU_NEWLY_IDLE,
7429                                                    &continue_balancing);
7430 
7431                         domain_cost = sched_clock_cpu(this_cpu) - t0;
7432                         if (domain_cost > sd->max_newidle_lb_cost)
7433                                 sd->max_newidle_lb_cost = domain_cost;
7434 
7435                         curr_cost += domain_cost;
7436                 }
7437 
7438                 update_next_balance(sd, 0, &next_balance);
7439 
7440                 /*
7441                  * Stop searching for tasks to pull if there are
7442                  * now runnable tasks on this rq.
7443                  */
7444                 if (pulled_task || this_rq->nr_running > 0)
7445                         break;
7446         }
7447         rcu_read_unlock();
7448 
7449         raw_spin_lock(&this_rq->lock);
7450 
7451         if (curr_cost > this_rq->max_idle_balance_cost)
7452                 this_rq->max_idle_balance_cost = curr_cost;
7453 
7454         /*
7455          * While browsing the domains, we released the rq lock, a task could
7456          * have been enqueued in the meantime. Since we're not going idle,
7457          * pretend we pulled a task.
7458          */
7459         if (this_rq->cfs.h_nr_running && !pulled_task)
7460                 pulled_task = 1;
7461 
7462 out:
7463         /* Move the next balance forward */
7464         if (time_after(this_rq->next_balance, next_balance))
7465                 this_rq->next_balance = next_balance;
7466 
7467         /* Is there a task of a high priority class? */
7468         if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7469                 pulled_task = -1;
7470 
7471         if (pulled_task)
7472                 this_rq->idle_stamp = 0;
7473 
7474         return pulled_task;
7475 }
7476 
7477 /*
7478  * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7479  * running tasks off the busiest CPU onto idle CPUs. It requires at
7480  * least 1 task to be running on each physical CPU where possible, and
7481  * avoids physical / logical imbalances.
7482  */
7483 static int active_load_balance_cpu_stop(void *data)
7484 {
7485         struct rq *busiest_rq = data;
7486         int busiest_cpu = cpu_of(busiest_rq);
7487         int target_cpu = busiest_rq->push_cpu;
7488         struct rq *target_rq = cpu_rq(target_cpu);
7489         struct sched_domain *sd;
7490         struct task_struct *p = NULL;
7491 
7492         raw_spin_lock_irq(&busiest_rq->lock);
7493 
7494         /* make sure the requested cpu hasn't gone down in the meantime */
7495         if (unlikely(busiest_cpu != smp_processor_id() ||
7496                      !busiest_rq->active_balance))
7497                 goto out_unlock;
7498 
7499         /* Is there any task to move? */
7500         if (busiest_rq->nr_running <= 1)
7501                 goto out_unlock;
7502 
7503         /*
7504          * This condition is "impossible", if it occurs
7505          * we need to fix it. Originally reported by
7506          * Bjorn Helgaas on a 128-cpu setup.
7507          */
7508         BUG_ON(busiest_rq == target_rq);
7509 
7510         /* Search for an sd spanning us and the target CPU. */
7511         rcu_read_lock();
7512         for_each_domain(target_cpu, sd) {
7513                 if ((sd->flags & SD_LOAD_BALANCE) &&
7514                     cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7515                                 break;
7516         }
7517 
7518         if (likely(sd)) {
7519                 struct lb_env env = {
7520                         .sd             = sd,
7521                         .dst_cpu        = target_cpu,
7522                         .dst_rq         = target_rq,
7523                         .src_cpu        = busiest_rq->cpu,
7524                         .src_rq         = busiest_rq,
7525                         .idle           = CPU_IDLE,
7526                 };
7527 
7528                 schedstat_inc(sd, alb_count);
7529 
7530                 p = detach_one_task(&env);
7531                 if (p)
7532                         schedstat_inc(sd, alb_pushed);
7533                 else
7534                         schedstat_inc(sd, alb_failed);
7535         }
7536         rcu_read_unlock();
7537 out_unlock:
7538         busiest_rq->active_balance = 0;
7539         raw_spin_unlock(&busiest_rq->lock);
7540 
7541         if (p)
7542                 attach_one_task(target_rq, p);
7543 
7544         local_irq_enable();
7545 
7546         return 0;
7547 }
7548 
7549 static inline int on_null_domain(struct rq *rq)
7550 {
7551         return unlikely(!rcu_dereference_sched(rq->sd));
7552 }
7553 
7554 #ifdef CONFIG_NO_HZ_COMMON
7555 /*
7556  * idle load balancing details
7557  * - When one of the busy CPUs notice that there may be an idle rebalancing
7558  *   needed, they will kick the idle load balancer, which then does idle
7559  *   load balancing for all the idle CPUs.
7560  */
7561 static struct {
7562         cpumask_var_t idle_cpus_mask;
7563         atomic_t nr_cpus;
7564         unsigned long next_balance;     /* in jiffy units */
7565 } nohz ____cacheline_aligned;
7566 
7567 static inline int find_new_ilb(void)
7568 {
7569         int ilb = cpumask_first(nohz.idle_cpus_mask);
7570 
7571         if (ilb < nr_cpu_ids && idle_cpu(ilb))
7572                 return ilb;
7573 
7574         return nr_cpu_ids;
7575 }
7576 
7577 /*
7578  * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7579  * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7580  * CPU (if there is one).
7581  */
7582 static void nohz_balancer_kick(void)
7583 {
7584         int ilb_cpu;
7585 
7586         nohz.next_balance++;
7587 
7588         ilb_cpu = find_new_ilb();
7589 
7590         if (ilb_cpu >= nr_cpu_ids)
7591                 return;
7592 
7593         if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7594                 return;
7595         /*
7596          * Use smp_send_reschedule() instead of resched_cpu().
7597          * This way we generate a sched IPI on the target cpu which
7598          * is idle. And the softirq performing nohz idle load balance
7599          * will be run before returning from the IPI.
7600          */
7601         smp_send_reschedule(ilb_cpu);
7602         return;
7603 }
7604 
7605 static inline void nohz_balance_exit_idle(int cpu)
7606 {
7607         if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7608                 /*
7609                  * Completely isolated CPUs don't ever set, so we must test.
7610                  */
7611                 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7612                         cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7613                         atomic_dec(&nohz.nr_cpus);
7614                 }
7615                 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7616         }
7617 }
7618 
7619 static inline void set_cpu_sd_state_busy(void)
7620 {
7621         struct sched_domain *sd;
7622         int cpu = smp_processor_id();
7623 
7624         rcu_read_lock();
7625         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7626 
7627         if (!sd || !sd->nohz_idle)
7628                 goto unlock;
7629         sd->nohz_idle = 0;
7630 
7631         atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7632 unlock:
7633         rcu_read_unlock();
7634 }
7635 
7636 void set_cpu_sd_state_idle(void)
7637 {
7638         struct sched_domain *sd;
7639         int cpu = smp_processor_id();
7640 
7641         rcu_read_lock();
7642         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7643 
7644         if (!sd || sd->nohz_idle)
7645                 goto unlock;
7646         sd->nohz_idle = 1;
7647 
7648         atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7649 unlock:
7650         rcu_read_unlock();
7651 }
7652 
7653 /*
7654  * This routine will record that the cpu is going idle with tick stopped.
7655  * This info will be used in performing idle load balancing in the future.
7656  */
7657 void nohz_balance_enter_idle(int cpu)
7658 {
7659         /*
7660          * If this cpu is going down, then nothing needs to be done.
7661          */
7662         if (!cpu_active(cpu))
7663                 return;
7664 
7665         if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7666                 return;
7667 
7668         /*
7669          * If we're a completely isolated CPU, we don't play.
7670          */
7671         if (on_null_domain(cpu_rq(cpu)))
7672                 return;
7673 
7674         cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7675         atomic_inc(&nohz.nr_cpus);
7676         set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7677 }
7678 
7679 static int sched_ilb_notifier(struct notifier_block *nfb,
7680                                         unsigned long action, void *hcpu)
7681 {
7682         switch (action & ~CPU_TASKS_FROZEN) {
7683         case CPU_DYING:
7684                 nohz_balance_exit_idle(smp_processor_id());
7685                 return NOTIFY_OK;
7686         default:
7687                 return NOTIFY_DONE;
7688         }
7689 }
7690 #endif
7691 
7692 static DEFINE_SPINLOCK(balancing);
7693 
7694 /*
7695  * Scale the max load_balance interval with the number of CPUs in the system.
7696  * This trades load-balance latency on larger machines for less cross talk.
7697  */
7698 void update_max_interval(void)
7699 {
7700         max_load_balance_interval = HZ*num_online_cpus()/10;
7701 }
7702 
7703 /*
7704  * It checks each scheduling domain to see if it is due to be balanced,
7705  * and initiates a balancing operation if so.
7706  *
7707  * Balancing parameters are set up in init_sched_domains.
7708  */
7709 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7710 {
7711         int continue_balancing = 1;
7712         int cpu = rq->cpu;
7713         unsigned long interval;
7714         struct sched_domain *sd;
7715         /* Earliest time when we have to do rebalance again */
7716         unsigned long next_balance = jiffies + 60*HZ;
7717         int update_next_balance = 0;
7718         int need_serialize, need_decay = 0;
7719         u64 max_cost = 0;
7720 
7721         update_blocked_averages(cpu);
7722 
7723         rcu_read_lock();
7724         for_each_domain(cpu, sd) {
7725                 /*
7726                  * Decay the newidle max times here because this is a regular
7727                  * visit to all the domains. Decay ~1% per second.
7728                  */
7729                 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7730                         sd->max_newidle_lb_cost =
7731                                 (sd->max_newidle_lb_cost * 253) / 256;
7732                         sd->next_decay_max_lb_cost = jiffies + HZ;
7733                         need_decay = 1;
7734                 }
7735                 max_cost += sd->max_newidle_lb_cost;
7736 
7737                 if (!(sd->flags & SD_LOAD_BALANCE))
7738                         continue;
7739 
7740                 /*
7741                  * Stop the load balance at this level. There is another
7742                  * CPU in our sched group which is doing load balancing more
7743                  * actively.
7744                  */
7745                 if (!continue_balancing) {
7746                         if (need_decay)
7747                                 continue;
7748                         break;
7749                 }
7750 
7751                 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7752 
7753                 need_serialize = sd->flags & SD_SERIALIZE;
7754                 if (need_serialize) {
7755                         if (!spin_trylock(&balancing))
7756                                 goto out;
7757                 }
7758 
7759                 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7760                         if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7761                                 /*
7762                                  * The LBF_DST_PINNED logic could have changed
7763                                  * env->dst_cpu, so we can't know our idle
7764                                  * state even if we migrated tasks. Update it.
7765                                  */
7766                                 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7767                         }
7768                         sd->last_balance = jiffies;
7769                         interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7770                 }
7771                 if (need_serialize)
7772                         spin_unlock(&balancing);
7773 out:
7774                 if (time_after(next_balance, sd->last_balance + interval)) {
7775                         next_balance = sd->last_balance + interval;
7776                         update_next_balance = 1;
7777                 }
7778         }
7779         if (need_decay) {
7780                 /*
7781                  * Ensure the rq-wide value also decays but keep it at a
7782                  * reasonable floor to avoid funnies with rq->avg_idle.
7783                  */
7784                 rq->max_idle_balance_cost =
7785                         max((u64)sysctl_sched_migration_cost, max_cost);
7786         }
7787         rcu_read_unlock();
7788 
7789         /*
7790          * next_balance will be updated only when there is a need.
7791          * When the cpu is attached to null domain for ex, it will not be
7792          * updated.
7793          */
7794         if (likely(update_next_balance)) {
7795                 rq->next_balance = next_balance;
7796 
7797 #ifdef CONFIG_NO_HZ_COMMON
7798                 /*
7799                  * If this CPU has been elected to perform the nohz idle
7800                  * balance. Other idle CPUs have already rebalanced with
7801                  * nohz_idle_balance() and nohz.next_balance has been
7802                  * updated accordingly. This CPU is now running the idle load
7803                  * balance for itself and we need to update the
7804                  * nohz.next_balance accordingly.
7805                  */
7806                 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
7807                         nohz.next_balance = rq->next_balance;
7808 #endif
7809         }
7810 }
7811 
7812 #ifdef CONFIG_NO_HZ_COMMON
7813 /*
7814  * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7815  * rebalancing for all the cpus for whom scheduler ticks are stopped.
7816  */
7817 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7818 {
7819         int this_cpu = this_rq->cpu;
7820         struct rq *rq;
7821         int balance_cpu;
7822         /* Earliest time when we have to do rebalance again */
7823         unsigned long next_balance = jiffies + 60*HZ;
7824         int update_next_balance = 0;
7825 
7826         if (idle != CPU_IDLE ||
7827             !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7828                 goto end;
7829 
7830         for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7831                 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7832                         continue;
7833 
7834                 /*
7835                  * If this cpu gets work to do, stop the load balancing
7836                  * work being done for other cpus. Next load
7837                  * balancing owner will pick it up.
7838                  */
7839                 if (need_resched())
7840                         break;
7841 
7842                 rq = cpu_rq(balance_cpu);
7843 
7844                 /*
7845                  * If time for next balance is due,
7846                  * do the balance.
7847                  */
7848                 if (time_after_eq(jiffies, rq->next_balance)) {
7849                         raw_spin_lock_irq(&rq->lock);
7850                         update_rq_clock(rq);
7851                         update_idle_cpu_load(rq);
7852                         raw_spin_unlock_irq(&rq->lock);
7853                         rebalance_domains(rq, CPU_IDLE);
7854                 }
7855 
7856                 if (time_after(next_balance, rq->next_balance)) {
7857                         next_balance = rq->next_balance;
7858                         update_next_balance = 1;
7859                 }
7860         }
7861 
7862         /*
7863          * next_balance will be updated only when there is a need.
7864          * When the CPU is attached to null domain for ex, it will not be
7865          * updated.
7866          */
7867         if (likely(update_next_balance))
7868                 nohz.next_balance = next_balance;
7869 end:
7870         clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7871 }
7872 
7873 /*
7874  * Current heuristic for kicking the idle load balancer in the presence
7875  * of an idle cpu in the system.
7876  *   - This rq has more than one task.
7877  *   - This rq has at least one CFS task and the capacity of the CPU is
7878  *     significantly reduced because of RT tasks or IRQs.
7879  *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
7880  *     multiple busy cpu.
7881  *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7882  *     domain span are idle.
7883  */
7884 static inline bool nohz_kick_needed(struct rq *rq)
7885 {
7886         unsigned long now = jiffies;
7887         struct sched_domain *sd;
7888         struct sched_group_capacity *sgc;
7889         int nr_busy, cpu = rq->cpu;
7890         bool kick = false;
7891 
7892         if (unlikely(rq->idle_balance))
7893                 return false;
7894 
7895        /*
7896         * We may be recently in ticked or tickless idle mode. At the first
7897         * busy tick after returning from idle, we will update the busy stats.
7898         */
7899         set_cpu_sd_state_busy();
7900         nohz_balance_exit_idle(cpu);
7901 
7902         /*
7903          * None are in tickless mode and hence no need for NOHZ idle load
7904          * balancing.
7905          */
7906         if (likely(!atomic_read(&nohz.nr_cpus)))
7907                 return false;
7908 
7909         if (time_before(now, nohz.next_balance))
7910                 return false;
7911 
7912         if (rq->nr_running >= 2)
7913                 return true;
7914 
7915         rcu_read_lock();
7916         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7917         if (sd) {
7918                 sgc = sd->groups->sgc;
7919                 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7920 
7921                 if (nr_busy > 1) {
7922                         kick = true;
7923                         goto unlock;
7924                 }
7925 
7926         }
7927 
7928         sd = rcu_dereference(rq->sd);
7929         if (sd) {
7930                 if ((rq->cfs.h_nr_running >= 1) &&
7931                                 check_cpu_capacity(rq, sd)) {
7932                         kick = true;
7933                         goto unlock;
7934                 }
7935         }
7936 
7937         sd = rcu_dereference(per_cpu(sd_asym, cpu));
7938         if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7939                                   sched_domain_span(sd)) < cpu)) {
7940                 kick = true;
7941                 goto unlock;
7942         }
7943 
7944 unlock:
7945         rcu_read_unlock();
7946         return kick;
7947 }
7948 #else
7949 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7950 #endif
7951 
7952 /*
7953  * run_rebalance_domains is triggered when needed from the scheduler tick.
7954  * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7955  */
7956 static void run_rebalance_domains(struct softirq_action *h)
7957 {
7958         struct rq *this_rq = this_rq();
7959         enum cpu_idle_type idle = this_rq->idle_balance ?
7960                                                 CPU_IDLE : CPU_NOT_IDLE;
7961 
7962         /*
7963          * If this cpu has a pending nohz_balance_kick, then do the
7964          * balancing on behalf of the other idle cpus whose ticks are
7965          * stopped. Do nohz_idle_balance *before* rebalance_domains to
7966          * give the idle cpus a chance to load balance. Else we may
7967          * load balance only within the local sched_domain hierarchy
7968          * and abort nohz_idle_balance altogether if we pull some load.
7969          */
7970         nohz_idle_balance(this_rq, idle);
7971         rebalance_domains(this_rq, idle);
7972 }
7973 
7974 /*
7975  * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7976  */
7977 void trigger_load_balance(struct rq *rq)
7978 {
7979         /* Don't need to rebalance while attached to NULL domain */
7980         if (unlikely(on_null_domain(rq)))
7981                 return;
7982 
7983         if (time_after_eq(jiffies, rq->next_balance))
7984                 raise_softirq(SCHED_SOFTIRQ);
7985 #ifdef CONFIG_NO_HZ_COMMON
7986         if (nohz_kick_needed(rq))
7987                 nohz_balancer_kick();
7988 #endif
7989 }
7990 
7991 static void rq_online_fair(struct rq *rq)
7992 {
7993         update_sysctl();
7994 
7995         update_runtime_enabled(rq);
7996 }
7997 
7998 static void rq_offline_fair(struct rq *rq)
7999 {
8000         update_sysctl();
8001 
8002         /* Ensure any throttled groups are reachable by pick_next_task */
8003         unthrottle_offline_cfs_rqs(rq);
8004 }
8005 
8006 #endif /* CONFIG_SMP */
8007 
8008 /*
8009  * scheduler tick hitting a task of our scheduling class:
8010  */
8011 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8012 {
8013         struct cfs_rq *cfs_rq;
8014         struct sched_entity *se = &curr->se;
8015 
8016         for_each_sched_entity(se) {
8017                 cfs_rq = cfs_rq_of(se);
8018                 entity_tick(cfs_rq, se, queued);
8019         }
8020 
8021         if (static_branch_unlikely(&sched_numa_balancing))
8022                 task_tick_numa(rq, curr);
8023 }
8024 
8025 /*
8026  * called on fork with the child task as argument from the parent's context
8027  *  - child not yet on the tasklist
8028  *  - preemption disabled
8029  */
8030 static void task_fork_fair(struct task_struct *p)
8031 {
8032         struct cfs_rq *cfs_rq;
8033         struct sched_entity *se = &p->se, *curr;
8034         int this_cpu = smp_processor_id();
8035         struct rq *rq = this_rq();
8036         unsigned long flags;
8037 
8038         raw_spin_lock_irqsave(&rq->lock, flags);
8039 
8040         update_rq_clock(rq);
8041 
8042         cfs_rq = task_cfs_rq(current);
8043         curr = cfs_rq->curr;
8044 
8045         /*
8046          * Not only the cpu but also the task_group of the parent might have
8047          * been changed after parent->se.parent,cfs_rq were copied to
8048          * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8049          * of child point to valid ones.
8050          */
8051         rcu_read_lock();
8052         __set_task_cpu(p, this_cpu);
8053         rcu_read_unlock();
8054 
8055         update_curr(cfs_rq);
8056 
8057         if (curr)
8058                 se->vruntime = curr->vruntime;
8059         place_entity(cfs_rq, se, 1);
8060 
8061         if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8062                 /*
8063                  * Upon rescheduling, sched_class::put_prev_task() will place
8064                  * 'current' within the tree based on its new key value.
8065                  */
8066                 swap(curr->vruntime, se->vruntime);
8067                 resched_curr(rq);
8068         }
8069 
8070         se->vruntime -= cfs_rq->min_vruntime;
8071 
8072         raw_spin_unlock_irqrestore(&rq->lock, flags);
8073 }
8074 
8075 /*
8076  * Priority of the task has changed. Check to see if we preempt
8077  * the current task.
8078  */
8079 static void
8080 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8081 {
8082         if (!task_on_rq_queued(p))
8083                 return;
8084 
8085         /*
8086          * Reschedule if we are currently running on this runqueue and
8087          * our priority decreased, or if we are not currently running on
8088          * this runqueue and our priority is higher than the current's
8089          */
8090         if (rq->curr == p) {
8091                 if (p->prio > oldprio)
8092                         resched_curr(rq);
8093         } else
8094                 check_preempt_curr(rq, p, 0);
8095 }
8096 
8097 static inline bool vruntime_normalized(struct task_struct *p)
8098 {
8099         struct sched_entity *se = &p->se;
8100 
8101         /*
8102          * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8103          * the dequeue_entity(.flags=0) will already have normalized the
8104          * vruntime.
8105          */
8106         if (p->on_rq)
8107                 return true;
8108 
8109         /*
8110          * When !on_rq, vruntime of the task has usually NOT been normalized.
8111          * But there are some cases where it has already been normalized:
8112          *
8113          * - A forked child which is waiting for being woken up by
8114          *   wake_up_new_task().
8115          * - A task which has been woken up by try_to_wake_up() and
8116          *   waiting for actually being woken up by sched_ttwu_pending().
8117          */
8118         if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8119                 return true;
8120 
8121         return false;
8122 }
8123 
8124 static void detach_task_cfs_rq(struct task_struct *p)
8125 {
8126         struct sched_entity *se = &p->se;
8127         struct cfs_rq *cfs_rq = cfs_rq_of(se);
8128 
8129         if (!vruntime_normalized(p)) {
8130                 /*
8131                  * Fix up our vruntime so that the current sleep doesn't
8132                  * cause 'unlimited' sleep bonus.
8133                  */
8134                 place_entity(cfs_rq, se, 0);
8135                 se->vruntime -= cfs_rq->min_vruntime;
8136         }
8137 
8138         /* Catch up with the cfs_rq and remove our load when we leave */
8139         detach_entity_load_avg(cfs_rq, se);
8140 }
8141 
8142 static void attach_task_cfs_rq(struct task_struct *p)
8143 {
8144         struct sched_entity *se = &p->se;
8145         struct cfs_rq *cfs_rq = cfs_rq_of(se);
8146 
8147 #ifdef CONFIG_FAIR_GROUP_SCHED
8148         /*
8149          * Since the real-depth could have been changed (only FAIR
8150          * class maintain depth value), reset depth properly.
8151          */
8152         se->depth = se->parent ? se->parent->depth + 1 : 0;
8153 #endif
8154 
8155         /* Synchronize task with its cfs_rq */
8156         attach_entity_load_avg(cfs_rq, se);
8157 
8158         if (!vruntime_normalized(p))
8159                 se->vruntime += cfs_rq->min_vruntime;
8160 }
8161 
8162 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8163 {
8164         detach_task_cfs_rq(p);
8165 }
8166 
8167 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8168 {
8169         attach_task_cfs_rq(p);
8170 
8171         if (task_on_rq_queued(p)) {
8172                 /*
8173                  * We were most likely switched from sched_rt, so
8174                  * kick off the schedule if running, otherwise just see
8175                  * if we can still preempt the current task.
8176                  */
8177                 if (rq->curr == p)
8178                         resched_curr(rq);
8179                 else
8180                         check_preempt_curr(rq, p, 0);
8181         }
8182 }
8183 
8184 /* Account for a task changing its policy or group.
8185  *
8186  * This routine is mostly called to set cfs_rq->curr field when a task
8187  * migrates between groups/classes.
8188  */
8189 static void set_curr_task_fair(struct rq *rq)
8190 {
8191         struct sched_entity *se = &rq->curr->se;
8192 
8193         for_each_sched_entity(se) {
8194                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8195 
8196                 set_next_entity(cfs_rq, se);
8197                 /* ensure bandwidth has been allocated on our new cfs_rq */
8198                 account_cfs_rq_runtime(cfs_rq, 0);
8199         }
8200 }
8201 
8202 void init_cfs_rq(struct cfs_rq *cfs_rq)
8203 {
8204         cfs_rq->tasks_timeline = RB_ROOT;
8205         cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8206 #ifndef CONFIG_64BIT
8207         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8208 #endif
8209 #ifdef CONFIG_SMP
8210         atomic_long_set(&cfs_rq->removed_load_avg, 0);
8211         atomic_long_set(&cfs_rq->removed_util_avg, 0);
8212 #endif
8213 }
8214 
8215 #ifdef CONFIG_FAIR_GROUP_SCHED
8216 static void task_move_group_fair(struct task_struct *p)
8217 {
8218         detach_task_cfs_rq(p);
8219         set_task_rq(p, task_cpu(p));
8220 
8221 #ifdef CONFIG_SMP
8222         /* Tell se's cfs_rq has been changed -- migrated */
8223         p->se.avg.last_update_time = 0;
8224 #endif
8225         attach_task_cfs_rq(p);
8226 }
8227 
8228 void free_fair_sched_group(struct task_group *tg)
8229 {
8230         int i;
8231 
8232         destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8233 
8234         for_each_possible_cpu(i) {
8235                 if (tg->cfs_rq)
8236                         kfree(tg->cfs_rq[i]);
8237                 if (tg->se) {
8238                         if (tg->se[i])
8239                                 remove_entity_load_avg(tg->se[i]);
8240                         kfree(tg->se[i]);
8241                 }
8242         }
8243 
8244         kfree(tg->cfs_rq);
8245         kfree(tg->se);
8246 }
8247 
8248 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8249 {
8250         struct cfs_rq *cfs_rq;
8251         struct sched_entity *se;
8252         int i;
8253 
8254         tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8255         if (!tg->cfs_rq)
8256                 goto err;
8257         tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8258         if (!tg->se)
8259                 goto err;
8260 
8261         tg->shares = NICE_0_LOAD;
8262 
8263         init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8264 
8265         for_each_possible_cpu(i) {
8266                 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8267                                       GFP_KERNEL, cpu_to_node(i));
8268                 if (!cfs_rq)
8269                         goto err;
8270 
8271                 se = kzalloc_node(sizeof(struct sched_entity),
8272                                   GFP_KERNEL, cpu_to_node(i));
8273                 if (!se)
8274                         goto err_free_rq;
8275 
8276                 init_cfs_rq(cfs_rq);
8277                 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8278                 init_entity_runnable_average(se);
8279         }
8280 
8281         return 1;
8282 
8283 err_free_rq:
8284         kfree(cfs_rq);
8285 err:
8286         return 0;
8287 }
8288 
8289 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8290 {
8291         struct rq *rq = cpu_rq(cpu);
8292         unsigned long flags;
8293 
8294         /*
8295         * Only empty task groups can be destroyed; so we can speculatively
8296         * check on_list without danger of it being re-added.
8297         */
8298         if (!tg->cfs_rq[cpu]->on_list)
8299                 return;
8300 
8301         raw_spin_lock_irqsave(&rq->lock, flags);
8302         list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8303         raw_spin_unlock_irqrestore(&rq->lock, flags);
8304 }
8305 
8306 void init_tg_cfs_entry(struct