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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 <pzijlstr@redhat.com>
 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 int get_update_sysctl_factor(void)
145 {
146         unsigned int cpus = min_t(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 void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
287                                        int force_update);
288 
289 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
290 {
291         if (!cfs_rq->on_list) {
292                 /*
293                  * Ensure we either appear before our parent (if already
294                  * enqueued) or force our parent to appear after us when it is
295                  * enqueued.  The fact that we always enqueue bottom-up
296                  * reduces this to two cases.
297                  */
298                 if (cfs_rq->tg->parent &&
299                     cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
300                         list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
301                                 &rq_of(cfs_rq)->leaf_cfs_rq_list);
302                 } else {
303                         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
304                                 &rq_of(cfs_rq)->leaf_cfs_rq_list);
305                 }
306 
307                 cfs_rq->on_list = 1;
308                 /* We should have no load, but we need to update last_decay. */
309                 update_cfs_rq_blocked_load(cfs_rq, 0);
310         }
311 }
312 
313 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
314 {
315         if (cfs_rq->on_list) {
316                 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
317                 cfs_rq->on_list = 0;
318         }
319 }
320 
321 /* Iterate thr' all leaf cfs_rq's on a runqueue */
322 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
323         list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
324 
325 /* Do the two (enqueued) entities belong to the same group ? */
326 static inline struct cfs_rq *
327 is_same_group(struct sched_entity *se, struct sched_entity *pse)
328 {
329         if (se->cfs_rq == pse->cfs_rq)
330                 return se->cfs_rq;
331 
332         return NULL;
333 }
334 
335 static inline struct sched_entity *parent_entity(struct sched_entity *se)
336 {
337         return se->parent;
338 }
339 
340 static void
341 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
342 {
343         int se_depth, pse_depth;
344 
345         /*
346          * preemption test can be made between sibling entities who are in the
347          * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
348          * both tasks until we find their ancestors who are siblings of common
349          * parent.
350          */
351 
352         /* First walk up until both entities are at same depth */
353         se_depth = (*se)->depth;
354         pse_depth = (*pse)->depth;
355 
356         while (se_depth > pse_depth) {
357                 se_depth--;
358                 *se = parent_entity(*se);
359         }
360 
361         while (pse_depth > se_depth) {
362                 pse_depth--;
363                 *pse = parent_entity(*pse);
364         }
365 
366         while (!is_same_group(*se, *pse)) {
367                 *se = parent_entity(*se);
368                 *pse = parent_entity(*pse);
369         }
370 }
371 
372 #else   /* !CONFIG_FAIR_GROUP_SCHED */
373 
374 static inline struct task_struct *task_of(struct sched_entity *se)
375 {
376         return container_of(se, struct task_struct, se);
377 }
378 
379 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
380 {
381         return container_of(cfs_rq, struct rq, cfs);
382 }
383 
384 #define entity_is_task(se)      1
385 
386 #define for_each_sched_entity(se) \
387                 for (; se; se = NULL)
388 
389 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
390 {
391         return &task_rq(p)->cfs;
392 }
393 
394 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
395 {
396         struct task_struct *p = task_of(se);
397         struct rq *rq = task_rq(p);
398 
399         return &rq->cfs;
400 }
401 
402 /* runqueue "owned" by this group */
403 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
404 {
405         return NULL;
406 }
407 
408 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
409 {
410 }
411 
412 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
413 {
414 }
415 
416 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
417                 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
418 
419 static inline struct sched_entity *parent_entity(struct sched_entity *se)
420 {
421         return NULL;
422 }
423 
424 static inline void
425 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
426 {
427 }
428 
429 #endif  /* CONFIG_FAIR_GROUP_SCHED */
430 
431 static __always_inline
432 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
433 
434 /**************************************************************
435  * Scheduling class tree data structure manipulation methods:
436  */
437 
438 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
439 {
440         s64 delta = (s64)(vruntime - max_vruntime);
441         if (delta > 0)
442                 max_vruntime = vruntime;
443 
444         return max_vruntime;
445 }
446 
447 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
448 {
449         s64 delta = (s64)(vruntime - min_vruntime);
450         if (delta < 0)
451                 min_vruntime = vruntime;
452 
453         return min_vruntime;
454 }
455 
456 static inline int entity_before(struct sched_entity *a,
457                                 struct sched_entity *b)
458 {
459         return (s64)(a->vruntime - b->vruntime) < 0;
460 }
461 
462 static void update_min_vruntime(struct cfs_rq *cfs_rq)
463 {
464         u64 vruntime = cfs_rq->min_vruntime;
465 
466         if (cfs_rq->curr)
467                 vruntime = cfs_rq->curr->vruntime;
468 
469         if (cfs_rq->rb_leftmost) {
470                 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
471                                                    struct sched_entity,
472                                                    run_node);
473 
474                 if (!cfs_rq->curr)
475                         vruntime = se->vruntime;
476                 else
477                         vruntime = min_vruntime(vruntime, se->vruntime);
478         }
479 
480         /* ensure we never gain time by being placed backwards. */
481         cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
482 #ifndef CONFIG_64BIT
483         smp_wmb();
484         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
485 #endif
486 }
487 
488 /*
489  * Enqueue an entity into the rb-tree:
490  */
491 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
492 {
493         struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
494         struct rb_node *parent = NULL;
495         struct sched_entity *entry;
496         int leftmost = 1;
497 
498         /*
499          * Find the right place in the rbtree:
500          */
501         while (*link) {
502                 parent = *link;
503                 entry = rb_entry(parent, struct sched_entity, run_node);
504                 /*
505                  * We dont care about collisions. Nodes with
506                  * the same key stay together.
507                  */
508                 if (entity_before(se, entry)) {
509                         link = &parent->rb_left;
510                 } else {
511                         link = &parent->rb_right;
512                         leftmost = 0;
513                 }
514         }
515 
516         /*
517          * Maintain a cache of leftmost tree entries (it is frequently
518          * used):
519          */
520         if (leftmost)
521                 cfs_rq->rb_leftmost = &se->run_node;
522 
523         rb_link_node(&se->run_node, parent, link);
524         rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
525 }
526 
527 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
528 {
529         if (cfs_rq->rb_leftmost == &se->run_node) {
530                 struct rb_node *next_node;
531 
532                 next_node = rb_next(&se->run_node);
533                 cfs_rq->rb_leftmost = next_node;
534         }
535 
536         rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
537 }
538 
539 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
540 {
541         struct rb_node *left = cfs_rq->rb_leftmost;
542 
543         if (!left)
544                 return NULL;
545 
546         return rb_entry(left, struct sched_entity, run_node);
547 }
548 
549 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
550 {
551         struct rb_node *next = rb_next(&se->run_node);
552 
553         if (!next)
554                 return NULL;
555 
556         return rb_entry(next, struct sched_entity, run_node);
557 }
558 
559 #ifdef CONFIG_SCHED_DEBUG
560 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
561 {
562         struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
563 
564         if (!last)
565                 return NULL;
566 
567         return rb_entry(last, struct sched_entity, run_node);
568 }
569 
570 /**************************************************************
571  * Scheduling class statistics methods:
572  */
573 
574 int sched_proc_update_handler(struct ctl_table *table, int write,
575                 void __user *buffer, size_t *lenp,
576                 loff_t *ppos)
577 {
578         int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
579         int factor = get_update_sysctl_factor();
580 
581         if (ret || !write)
582                 return ret;
583 
584         sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
585                                         sysctl_sched_min_granularity);
586 
587 #define WRT_SYSCTL(name) \
588         (normalized_sysctl_##name = sysctl_##name / (factor))
589         WRT_SYSCTL(sched_min_granularity);
590         WRT_SYSCTL(sched_latency);
591         WRT_SYSCTL(sched_wakeup_granularity);
592 #undef WRT_SYSCTL
593 
594         return 0;
595 }
596 #endif
597 
598 /*
599  * delta /= w
600  */
601 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
602 {
603         if (unlikely(se->load.weight != NICE_0_LOAD))
604                 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
605 
606         return delta;
607 }
608 
609 /*
610  * The idea is to set a period in which each task runs once.
611  *
612  * When there are too many tasks (sched_nr_latency) we have to stretch
613  * this period because otherwise the slices get too small.
614  *
615  * p = (nr <= nl) ? l : l*nr/nl
616  */
617 static u64 __sched_period(unsigned long nr_running)
618 {
619         u64 period = sysctl_sched_latency;
620         unsigned long nr_latency = sched_nr_latency;
621 
622         if (unlikely(nr_running > nr_latency)) {
623                 period = sysctl_sched_min_granularity;
624                 period *= nr_running;
625         }
626 
627         return period;
628 }
629 
630 /*
631  * We calculate the wall-time slice from the period by taking a part
632  * proportional to the weight.
633  *
634  * s = p*P[w/rw]
635  */
636 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
637 {
638         u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
639 
640         for_each_sched_entity(se) {
641                 struct load_weight *load;
642                 struct load_weight lw;
643 
644                 cfs_rq = cfs_rq_of(se);
645                 load = &cfs_rq->load;
646 
647                 if (unlikely(!se->on_rq)) {
648                         lw = cfs_rq->load;
649 
650                         update_load_add(&lw, se->load.weight);
651                         load = &lw;
652                 }
653                 slice = __calc_delta(slice, se->load.weight, load);
654         }
655         return slice;
656 }
657 
658 /*
659  * We calculate the vruntime slice of a to-be-inserted task.
660  *
661  * vs = s/w
662  */
663 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
664 {
665         return calc_delta_fair(sched_slice(cfs_rq, se), se);
666 }
667 
668 #ifdef CONFIG_SMP
669 static int select_idle_sibling(struct task_struct *p, int cpu);
670 static unsigned long task_h_load(struct task_struct *p);
671 
672 static inline void __update_task_entity_contrib(struct sched_entity *se);
673 
674 /* Give new task start runnable values to heavy its load in infant time */
675 void init_task_runnable_average(struct task_struct *p)
676 {
677         u32 slice;
678 
679         p->se.avg.decay_count = 0;
680         slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
681         p->se.avg.runnable_avg_sum = slice;
682         p->se.avg.runnable_avg_period = slice;
683         __update_task_entity_contrib(&p->se);
684 }
685 #else
686 void init_task_runnable_average(struct task_struct *p)
687 {
688 }
689 #endif
690 
691 /*
692  * Update the current task's runtime statistics.
693  */
694 static void update_curr(struct cfs_rq *cfs_rq)
695 {
696         struct sched_entity *curr = cfs_rq->curr;
697         u64 now = rq_clock_task(rq_of(cfs_rq));
698         u64 delta_exec;
699 
700         if (unlikely(!curr))
701                 return;
702 
703         delta_exec = now - curr->exec_start;
704         if (unlikely((s64)delta_exec <= 0))
705                 return;
706 
707         curr->exec_start = now;
708 
709         schedstat_set(curr->statistics.exec_max,
710                       max(delta_exec, curr->statistics.exec_max));
711 
712         curr->sum_exec_runtime += delta_exec;
713         schedstat_add(cfs_rq, exec_clock, delta_exec);
714 
715         curr->vruntime += calc_delta_fair(delta_exec, curr);
716         update_min_vruntime(cfs_rq);
717 
718         if (entity_is_task(curr)) {
719                 struct task_struct *curtask = task_of(curr);
720 
721                 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
722                 cpuacct_charge(curtask, delta_exec);
723                 account_group_exec_runtime(curtask, delta_exec);
724         }
725 
726         account_cfs_rq_runtime(cfs_rq, delta_exec);
727 }
728 
729 static void update_curr_fair(struct rq *rq)
730 {
731         update_curr(cfs_rq_of(&rq->curr->se));
732 }
733 
734 static inline void
735 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
736 {
737         schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
738 }
739 
740 /*
741  * Task is being enqueued - update stats:
742  */
743 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
744 {
745         /*
746          * Are we enqueueing a waiting task? (for current tasks
747          * a dequeue/enqueue event is a NOP)
748          */
749         if (se != cfs_rq->curr)
750                 update_stats_wait_start(cfs_rq, se);
751 }
752 
753 static void
754 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
755 {
756         schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
757                         rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
758         schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
759         schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
760                         rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
761 #ifdef CONFIG_SCHEDSTATS
762         if (entity_is_task(se)) {
763                 trace_sched_stat_wait(task_of(se),
764                         rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
765         }
766 #endif
767         schedstat_set(se->statistics.wait_start, 0);
768 }
769 
770 static inline void
771 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
772 {
773         /*
774          * Mark the end of the wait period if dequeueing a
775          * waiting task:
776          */
777         if (se != cfs_rq->curr)
778                 update_stats_wait_end(cfs_rq, se);
779 }
780 
781 /*
782  * We are picking a new current task - update its stats:
783  */
784 static inline void
785 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
786 {
787         /*
788          * We are starting a new run period:
789          */
790         se->exec_start = rq_clock_task(rq_of(cfs_rq));
791 }
792 
793 /**************************************************
794  * Scheduling class queueing methods:
795  */
796 
797 #ifdef CONFIG_NUMA_BALANCING
798 /*
799  * Approximate time to scan a full NUMA task in ms. The task scan period is
800  * calculated based on the tasks virtual memory size and
801  * numa_balancing_scan_size.
802  */
803 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
804 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
805 
806 /* Portion of address space to scan in MB */
807 unsigned int sysctl_numa_balancing_scan_size = 256;
808 
809 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
810 unsigned int sysctl_numa_balancing_scan_delay = 1000;
811 
812 static unsigned int task_nr_scan_windows(struct task_struct *p)
813 {
814         unsigned long rss = 0;
815         unsigned long nr_scan_pages;
816 
817         /*
818          * Calculations based on RSS as non-present and empty pages are skipped
819          * by the PTE scanner and NUMA hinting faults should be trapped based
820          * on resident pages
821          */
822         nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
823         rss = get_mm_rss(p->mm);
824         if (!rss)
825                 rss = nr_scan_pages;
826 
827         rss = round_up(rss, nr_scan_pages);
828         return rss / nr_scan_pages;
829 }
830 
831 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
832 #define MAX_SCAN_WINDOW 2560
833 
834 static unsigned int task_scan_min(struct task_struct *p)
835 {
836         unsigned int scan_size = ACCESS_ONCE(sysctl_numa_balancing_scan_size);
837         unsigned int scan, floor;
838         unsigned int windows = 1;
839 
840         if (scan_size < MAX_SCAN_WINDOW)
841                 windows = MAX_SCAN_WINDOW / scan_size;
842         floor = 1000 / windows;
843 
844         scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
845         return max_t(unsigned int, floor, scan);
846 }
847 
848 static unsigned int task_scan_max(struct task_struct *p)
849 {
850         unsigned int smin = task_scan_min(p);
851         unsigned int smax;
852 
853         /* Watch for min being lower than max due to floor calculations */
854         smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
855         return max(smin, smax);
856 }
857 
858 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
859 {
860         rq->nr_numa_running += (p->numa_preferred_nid != -1);
861         rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
862 }
863 
864 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
865 {
866         rq->nr_numa_running -= (p->numa_preferred_nid != -1);
867         rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
868 }
869 
870 struct numa_group {
871         atomic_t refcount;
872 
873         spinlock_t lock; /* nr_tasks, tasks */
874         int nr_tasks;
875         pid_t gid;
876         struct list_head task_list;
877 
878         struct rcu_head rcu;
879         nodemask_t active_nodes;
880         unsigned long total_faults;
881         /*
882          * Faults_cpu is used to decide whether memory should move
883          * towards the CPU. As a consequence, these stats are weighted
884          * more by CPU use than by memory faults.
885          */
886         unsigned long *faults_cpu;
887         unsigned long faults[0];
888 };
889 
890 /* Shared or private faults. */
891 #define NR_NUMA_HINT_FAULT_TYPES 2
892 
893 /* Memory and CPU locality */
894 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
895 
896 /* Averaged statistics, and temporary buffers. */
897 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
898 
899 pid_t task_numa_group_id(struct task_struct *p)
900 {
901         return p->numa_group ? p->numa_group->gid : 0;
902 }
903 
904 static inline int task_faults_idx(int nid, int priv)
905 {
906         return NR_NUMA_HINT_FAULT_TYPES * nid + priv;
907 }
908 
909 static inline unsigned long task_faults(struct task_struct *p, int nid)
910 {
911         if (!p->numa_faults_memory)
912                 return 0;
913 
914         return p->numa_faults_memory[task_faults_idx(nid, 0)] +
915                 p->numa_faults_memory[task_faults_idx(nid, 1)];
916 }
917 
918 static inline unsigned long group_faults(struct task_struct *p, int nid)
919 {
920         if (!p->numa_group)
921                 return 0;
922 
923         return p->numa_group->faults[task_faults_idx(nid, 0)] +
924                 p->numa_group->faults[task_faults_idx(nid, 1)];
925 }
926 
927 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
928 {
929         return group->faults_cpu[task_faults_idx(nid, 0)] +
930                 group->faults_cpu[task_faults_idx(nid, 1)];
931 }
932 
933 /*
934  * These return the fraction of accesses done by a particular task, or
935  * task group, on a particular numa node.  The group weight is given a
936  * larger multiplier, in order to group tasks together that are almost
937  * evenly spread out between numa nodes.
938  */
939 static inline unsigned long task_weight(struct task_struct *p, int nid)
940 {
941         unsigned long total_faults;
942 
943         if (!p->numa_faults_memory)
944                 return 0;
945 
946         total_faults = p->total_numa_faults;
947 
948         if (!total_faults)
949                 return 0;
950 
951         return 1000 * task_faults(p, nid) / total_faults;
952 }
953 
954 static inline unsigned long group_weight(struct task_struct *p, int nid)
955 {
956         if (!p->numa_group || !p->numa_group->total_faults)
957                 return 0;
958 
959         return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
960 }
961 
962 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
963                                 int src_nid, int dst_cpu)
964 {
965         struct numa_group *ng = p->numa_group;
966         int dst_nid = cpu_to_node(dst_cpu);
967         int last_cpupid, this_cpupid;
968 
969         this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
970 
971         /*
972          * Multi-stage node selection is used in conjunction with a periodic
973          * migration fault to build a temporal task<->page relation. By using
974          * a two-stage filter we remove short/unlikely relations.
975          *
976          * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
977          * a task's usage of a particular page (n_p) per total usage of this
978          * page (n_t) (in a given time-span) to a probability.
979          *
980          * Our periodic faults will sample this probability and getting the
981          * same result twice in a row, given these samples are fully
982          * independent, is then given by P(n)^2, provided our sample period
983          * is sufficiently short compared to the usage pattern.
984          *
985          * This quadric squishes small probabilities, making it less likely we
986          * act on an unlikely task<->page relation.
987          */
988         last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
989         if (!cpupid_pid_unset(last_cpupid) &&
990                                 cpupid_to_nid(last_cpupid) != dst_nid)
991                 return false;
992 
993         /* Always allow migrate on private faults */
994         if (cpupid_match_pid(p, last_cpupid))
995                 return true;
996 
997         /* A shared fault, but p->numa_group has not been set up yet. */
998         if (!ng)
999                 return true;
1000 
1001         /*
1002          * Do not migrate if the destination is not a node that
1003          * is actively used by this numa group.
1004          */
1005         if (!node_isset(dst_nid, ng->active_nodes))
1006                 return false;
1007 
1008         /*
1009          * Source is a node that is not actively used by this
1010          * numa group, while the destination is. Migrate.
1011          */
1012         if (!node_isset(src_nid, ng->active_nodes))
1013                 return true;
1014 
1015         /*
1016          * Both source and destination are nodes in active
1017          * use by this numa group. Maximize memory bandwidth
1018          * by migrating from more heavily used groups, to less
1019          * heavily used ones, spreading the load around.
1020          * Use a 1/4 hysteresis to avoid spurious page movement.
1021          */
1022         return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1023 }
1024 
1025 static unsigned long weighted_cpuload(const int cpu);
1026 static unsigned long source_load(int cpu, int type);
1027 static unsigned long target_load(int cpu, int type);
1028 static unsigned long capacity_of(int cpu);
1029 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1030 
1031 /* Cached statistics for all CPUs within a node */
1032 struct numa_stats {
1033         unsigned long nr_running;
1034         unsigned long load;
1035 
1036         /* Total compute capacity of CPUs on a node */
1037         unsigned long compute_capacity;
1038 
1039         /* Approximate capacity in terms of runnable tasks on a node */
1040         unsigned long task_capacity;
1041         int has_free_capacity;
1042 };
1043 
1044 /*
1045  * XXX borrowed from update_sg_lb_stats
1046  */
1047 static void update_numa_stats(struct numa_stats *ns, int nid)
1048 {
1049         int smt, cpu, cpus = 0;
1050         unsigned long capacity;
1051 
1052         memset(ns, 0, sizeof(*ns));
1053         for_each_cpu(cpu, cpumask_of_node(nid)) {
1054                 struct rq *rq = cpu_rq(cpu);
1055 
1056                 ns->nr_running += rq->nr_running;
1057                 ns->load += weighted_cpuload(cpu);
1058                 ns->compute_capacity += capacity_of(cpu);
1059 
1060                 cpus++;
1061         }
1062 
1063         /*
1064          * If we raced with hotplug and there are no CPUs left in our mask
1065          * the @ns structure is NULL'ed and task_numa_compare() will
1066          * not find this node attractive.
1067          *
1068          * We'll either bail at !has_free_capacity, or we'll detect a huge
1069          * imbalance and bail there.
1070          */
1071         if (!cpus)
1072                 return;
1073 
1074         /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1075         smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1076         capacity = cpus / smt; /* cores */
1077 
1078         ns->task_capacity = min_t(unsigned, capacity,
1079                 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1080         ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1081 }
1082 
1083 struct task_numa_env {
1084         struct task_struct *p;
1085 
1086         int src_cpu, src_nid;
1087         int dst_cpu, dst_nid;
1088 
1089         struct numa_stats src_stats, dst_stats;
1090 
1091         int imbalance_pct;
1092 
1093         struct task_struct *best_task;
1094         long best_imp;
1095         int best_cpu;
1096 };
1097 
1098 static void task_numa_assign(struct task_numa_env *env,
1099                              struct task_struct *p, long imp)
1100 {
1101         if (env->best_task)
1102                 put_task_struct(env->best_task);
1103         if (p)
1104                 get_task_struct(p);
1105 
1106         env->best_task = p;
1107         env->best_imp = imp;
1108         env->best_cpu = env->dst_cpu;
1109 }
1110 
1111 static bool load_too_imbalanced(long src_load, long dst_load,
1112                                 struct task_numa_env *env)
1113 {
1114         long imb, old_imb;
1115         long orig_src_load, orig_dst_load;
1116         long src_capacity, dst_capacity;
1117 
1118         /*
1119          * The load is corrected for the CPU capacity available on each node.
1120          *
1121          * src_load        dst_load
1122          * ------------ vs ---------
1123          * src_capacity    dst_capacity
1124          */
1125         src_capacity = env->src_stats.compute_capacity;
1126         dst_capacity = env->dst_stats.compute_capacity;
1127 
1128         /* We care about the slope of the imbalance, not the direction. */
1129         if (dst_load < src_load)
1130                 swap(dst_load, src_load);
1131 
1132         /* Is the difference below the threshold? */
1133         imb = dst_load * src_capacity * 100 -
1134               src_load * dst_capacity * env->imbalance_pct;
1135         if (imb <= 0)
1136                 return false;
1137 
1138         /*
1139          * The imbalance is above the allowed threshold.
1140          * Compare it with the old imbalance.
1141          */
1142         orig_src_load = env->src_stats.load;
1143         orig_dst_load = env->dst_stats.load;
1144 
1145         if (orig_dst_load < orig_src_load)
1146                 swap(orig_dst_load, orig_src_load);
1147 
1148         old_imb = orig_dst_load * src_capacity * 100 -
1149                   orig_src_load * dst_capacity * env->imbalance_pct;
1150 
1151         /* Would this change make things worse? */
1152         return (imb > old_imb);
1153 }
1154 
1155 /*
1156  * This checks if the overall compute and NUMA accesses of the system would
1157  * be improved if the source tasks was migrated to the target dst_cpu taking
1158  * into account that it might be best if task running on the dst_cpu should
1159  * be exchanged with the source task
1160  */
1161 static void task_numa_compare(struct task_numa_env *env,
1162                               long taskimp, long groupimp)
1163 {
1164         struct rq *src_rq = cpu_rq(env->src_cpu);
1165         struct rq *dst_rq = cpu_rq(env->dst_cpu);
1166         struct task_struct *cur;
1167         long src_load, dst_load;
1168         long load;
1169         long imp = env->p->numa_group ? groupimp : taskimp;
1170         long moveimp = imp;
1171 
1172         rcu_read_lock();
1173 
1174         raw_spin_lock_irq(&dst_rq->lock);
1175         cur = dst_rq->curr;
1176         /*
1177          * No need to move the exiting task, and this ensures that ->curr
1178          * wasn't reaped and thus get_task_struct() in task_numa_assign()
1179          * is safe under RCU read lock.
1180          * Note that rcu_read_lock() itself can't protect from the final
1181          * put_task_struct() after the last schedule().
1182          */
1183         if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1184                 cur = NULL;
1185         raw_spin_unlock_irq(&dst_rq->lock);
1186 
1187         /*
1188          * Because we have preemption enabled we can get migrated around and
1189          * end try selecting ourselves (current == env->p) as a swap candidate.
1190          */
1191         if (cur == env->p)
1192                 goto unlock;
1193 
1194         /*
1195          * "imp" is the fault differential for the source task between the
1196          * source and destination node. Calculate the total differential for
1197          * the source task and potential destination task. The more negative
1198          * the value is, the more rmeote accesses that would be expected to
1199          * be incurred if the tasks were swapped.
1200          */
1201         if (cur) {
1202                 /* Skip this swap candidate if cannot move to the source cpu */
1203                 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1204                         goto unlock;
1205 
1206                 /*
1207                  * If dst and source tasks are in the same NUMA group, or not
1208                  * in any group then look only at task weights.
1209                  */
1210                 if (cur->numa_group == env->p->numa_group) {
1211                         imp = taskimp + task_weight(cur, env->src_nid) -
1212                               task_weight(cur, env->dst_nid);
1213                         /*
1214                          * Add some hysteresis to prevent swapping the
1215                          * tasks within a group over tiny differences.
1216                          */
1217                         if (cur->numa_group)
1218                                 imp -= imp/16;
1219                 } else {
1220                         /*
1221                          * Compare the group weights. If a task is all by
1222                          * itself (not part of a group), use the task weight
1223                          * instead.
1224                          */
1225                         if (cur->numa_group)
1226                                 imp += group_weight(cur, env->src_nid) -
1227                                        group_weight(cur, env->dst_nid);
1228                         else
1229                                 imp += task_weight(cur, env->src_nid) -
1230                                        task_weight(cur, env->dst_nid);
1231                 }
1232         }
1233 
1234         if (imp <= env->best_imp && moveimp <= env->best_imp)
1235                 goto unlock;
1236 
1237         if (!cur) {
1238                 /* Is there capacity at our destination? */
1239                 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1240                     !env->dst_stats.has_free_capacity)
1241                         goto unlock;
1242 
1243                 goto balance;
1244         }
1245 
1246         /* Balance doesn't matter much if we're running a task per cpu */
1247         if (imp > env->best_imp && src_rq->nr_running == 1 &&
1248                         dst_rq->nr_running == 1)
1249                 goto assign;
1250 
1251         /*
1252          * In the overloaded case, try and keep the load balanced.
1253          */
1254 balance:
1255         load = task_h_load(env->p);
1256         dst_load = env->dst_stats.load + load;
1257         src_load = env->src_stats.load - load;
1258 
1259         if (moveimp > imp && moveimp > env->best_imp) {
1260                 /*
1261                  * If the improvement from just moving env->p direction is
1262                  * better than swapping tasks around, check if a move is
1263                  * possible. Store a slightly smaller score than moveimp,
1264                  * so an actually idle CPU will win.
1265                  */
1266                 if (!load_too_imbalanced(src_load, dst_load, env)) {
1267                         imp = moveimp - 1;
1268                         cur = NULL;
1269                         goto assign;
1270                 }
1271         }
1272 
1273         if (imp <= env->best_imp)
1274                 goto unlock;
1275 
1276         if (cur) {
1277                 load = task_h_load(cur);
1278                 dst_load -= load;
1279                 src_load += load;
1280         }
1281 
1282         if (load_too_imbalanced(src_load, dst_load, env))
1283                 goto unlock;
1284 
1285         /*
1286          * One idle CPU per node is evaluated for a task numa move.
1287          * Call select_idle_sibling to maybe find a better one.
1288          */
1289         if (!cur)
1290                 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1291 
1292 assign:
1293         task_numa_assign(env, cur, imp);
1294 unlock:
1295         rcu_read_unlock();
1296 }
1297 
1298 static void task_numa_find_cpu(struct task_numa_env *env,
1299                                 long taskimp, long groupimp)
1300 {
1301         int cpu;
1302 
1303         for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1304                 /* Skip this CPU if the source task cannot migrate */
1305                 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1306                         continue;
1307 
1308                 env->dst_cpu = cpu;
1309                 task_numa_compare(env, taskimp, groupimp);
1310         }
1311 }
1312 
1313 static int task_numa_migrate(struct task_struct *p)
1314 {
1315         struct task_numa_env env = {
1316                 .p = p,
1317 
1318                 .src_cpu = task_cpu(p),
1319                 .src_nid = task_node(p),
1320 
1321                 .imbalance_pct = 112,
1322 
1323                 .best_task = NULL,
1324                 .best_imp = 0,
1325                 .best_cpu = -1
1326         };
1327         struct sched_domain *sd;
1328         unsigned long taskweight, groupweight;
1329         int nid, ret;
1330         long taskimp, groupimp;
1331 
1332         /*
1333          * Pick the lowest SD_NUMA domain, as that would have the smallest
1334          * imbalance and would be the first to start moving tasks about.
1335          *
1336          * And we want to avoid any moving of tasks about, as that would create
1337          * random movement of tasks -- counter the numa conditions we're trying
1338          * to satisfy here.
1339          */
1340         rcu_read_lock();
1341         sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1342         if (sd)
1343                 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1344         rcu_read_unlock();
1345 
1346         /*
1347          * Cpusets can break the scheduler domain tree into smaller
1348          * balance domains, some of which do not cross NUMA boundaries.
1349          * Tasks that are "trapped" in such domains cannot be migrated
1350          * elsewhere, so there is no point in (re)trying.
1351          */
1352         if (unlikely(!sd)) {
1353                 p->numa_preferred_nid = task_node(p);
1354                 return -EINVAL;
1355         }
1356 
1357         taskweight = task_weight(p, env.src_nid);
1358         groupweight = group_weight(p, env.src_nid);
1359         update_numa_stats(&env.src_stats, env.src_nid);
1360         env.dst_nid = p->numa_preferred_nid;
1361         taskimp = task_weight(p, env.dst_nid) - taskweight;
1362         groupimp = group_weight(p, env.dst_nid) - groupweight;
1363         update_numa_stats(&env.dst_stats, env.dst_nid);
1364 
1365         /* Try to find a spot on the preferred nid. */
1366         task_numa_find_cpu(&env, taskimp, groupimp);
1367 
1368         /* No space available on the preferred nid. Look elsewhere. */
1369         if (env.best_cpu == -1) {
1370                 for_each_online_node(nid) {
1371                         if (nid == env.src_nid || nid == p->numa_preferred_nid)
1372                                 continue;
1373 
1374                         /* Only consider nodes where both task and groups benefit */
1375                         taskimp = task_weight(p, nid) - taskweight;
1376                         groupimp = group_weight(p, nid) - groupweight;
1377                         if (taskimp < 0 && groupimp < 0)
1378                                 continue;
1379 
1380                         env.dst_nid = nid;
1381                         update_numa_stats(&env.dst_stats, env.dst_nid);
1382                         task_numa_find_cpu(&env, taskimp, groupimp);
1383                 }
1384         }
1385 
1386         /*
1387          * If the task is part of a workload that spans multiple NUMA nodes,
1388          * and is migrating into one of the workload's active nodes, remember
1389          * this node as the task's preferred numa node, so the workload can
1390          * settle down.
1391          * A task that migrated to a second choice node will be better off
1392          * trying for a better one later. Do not set the preferred node here.
1393          */
1394         if (p->numa_group) {
1395                 if (env.best_cpu == -1)
1396                         nid = env.src_nid;
1397                 else
1398                         nid = env.dst_nid;
1399 
1400                 if (node_isset(nid, p->numa_group->active_nodes))
1401                         sched_setnuma(p, env.dst_nid);
1402         }
1403 
1404         /* No better CPU than the current one was found. */
1405         if (env.best_cpu == -1)
1406                 return -EAGAIN;
1407 
1408         /*
1409          * Reset the scan period if the task is being rescheduled on an
1410          * alternative node to recheck if the tasks is now properly placed.
1411          */
1412         p->numa_scan_period = task_scan_min(p);
1413 
1414         if (env.best_task == NULL) {
1415                 ret = migrate_task_to(p, env.best_cpu);
1416                 if (ret != 0)
1417                         trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1418                 return ret;
1419         }
1420 
1421         ret = migrate_swap(p, env.best_task);
1422         if (ret != 0)
1423                 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1424         put_task_struct(env.best_task);
1425         return ret;
1426 }
1427 
1428 /* Attempt to migrate a task to a CPU on the preferred node. */
1429 static void numa_migrate_preferred(struct task_struct *p)
1430 {
1431         unsigned long interval = HZ;
1432 
1433         /* This task has no NUMA fault statistics yet */
1434         if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults_memory))
1435                 return;
1436 
1437         /* Periodically retry migrating the task to the preferred node */
1438         interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1439         p->numa_migrate_retry = jiffies + interval;
1440 
1441         /* Success if task is already running on preferred CPU */
1442         if (task_node(p) == p->numa_preferred_nid)
1443                 return;
1444 
1445         /* Otherwise, try migrate to a CPU on the preferred node */
1446         task_numa_migrate(p);
1447 }
1448 
1449 /*
1450  * Find the nodes on which the workload is actively running. We do this by
1451  * tracking the nodes from which NUMA hinting faults are triggered. This can
1452  * be different from the set of nodes where the workload's memory is currently
1453  * located.
1454  *
1455  * The bitmask is used to make smarter decisions on when to do NUMA page
1456  * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1457  * are added when they cause over 6/16 of the maximum number of faults, but
1458  * only removed when they drop below 3/16.
1459  */
1460 static void update_numa_active_node_mask(struct numa_group *numa_group)
1461 {
1462         unsigned long faults, max_faults = 0;
1463         int nid;
1464 
1465         for_each_online_node(nid) {
1466                 faults = group_faults_cpu(numa_group, nid);
1467                 if (faults > max_faults)
1468                         max_faults = faults;
1469         }
1470 
1471         for_each_online_node(nid) {
1472                 faults = group_faults_cpu(numa_group, nid);
1473                 if (!node_isset(nid, numa_group->active_nodes)) {
1474                         if (faults > max_faults * 6 / 16)
1475                                 node_set(nid, numa_group->active_nodes);
1476                 } else if (faults < max_faults * 3 / 16)
1477                         node_clear(nid, numa_group->active_nodes);
1478         }
1479 }
1480 
1481 /*
1482  * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1483  * increments. The more local the fault statistics are, the higher the scan
1484  * period will be for the next scan window. If local/(local+remote) ratio is
1485  * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1486  * the scan period will decrease. Aim for 70% local accesses.
1487  */
1488 #define NUMA_PERIOD_SLOTS 10
1489 #define NUMA_PERIOD_THRESHOLD 7
1490 
1491 /*
1492  * Increase the scan period (slow down scanning) if the majority of
1493  * our memory is already on our local node, or if the majority of
1494  * the page accesses are shared with other processes.
1495  * Otherwise, decrease the scan period.
1496  */
1497 static void update_task_scan_period(struct task_struct *p,
1498                         unsigned long shared, unsigned long private)
1499 {
1500         unsigned int period_slot;
1501         int ratio;
1502         int diff;
1503 
1504         unsigned long remote = p->numa_faults_locality[0];
1505         unsigned long local = p->numa_faults_locality[1];
1506 
1507         /*
1508          * If there were no record hinting faults then either the task is
1509          * completely idle or all activity is areas that are not of interest
1510          * to automatic numa balancing. Scan slower
1511          */
1512         if (local + shared == 0) {
1513                 p->numa_scan_period = min(p->numa_scan_period_max,
1514                         p->numa_scan_period << 1);
1515 
1516                 p->mm->numa_next_scan = jiffies +
1517                         msecs_to_jiffies(p->numa_scan_period);
1518 
1519                 return;
1520         }
1521 
1522         /*
1523          * Prepare to scale scan period relative to the current period.
1524          *       == NUMA_PERIOD_THRESHOLD scan period stays the same
1525          *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1526          *       >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1527          */
1528         period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1529         ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1530         if (ratio >= NUMA_PERIOD_THRESHOLD) {
1531                 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1532                 if (!slot)
1533                         slot = 1;
1534                 diff = slot * period_slot;
1535         } else {
1536                 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1537 
1538                 /*
1539                  * Scale scan rate increases based on sharing. There is an
1540                  * inverse relationship between the degree of sharing and
1541                  * the adjustment made to the scanning period. Broadly
1542                  * speaking the intent is that there is little point
1543                  * scanning faster if shared accesses dominate as it may
1544                  * simply bounce migrations uselessly
1545                  */
1546                 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1547                 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1548         }
1549 
1550         p->numa_scan_period = clamp(p->numa_scan_period + diff,
1551                         task_scan_min(p), task_scan_max(p));
1552         memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1553 }
1554 
1555 /*
1556  * Get the fraction of time the task has been running since the last
1557  * NUMA placement cycle. The scheduler keeps similar statistics, but
1558  * decays those on a 32ms period, which is orders of magnitude off
1559  * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1560  * stats only if the task is so new there are no NUMA statistics yet.
1561  */
1562 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1563 {
1564         u64 runtime, delta, now;
1565         /* Use the start of this time slice to avoid calculations. */
1566         now = p->se.exec_start;
1567         runtime = p->se.sum_exec_runtime;
1568 
1569         if (p->last_task_numa_placement) {
1570                 delta = runtime - p->last_sum_exec_runtime;
1571                 *period = now - p->last_task_numa_placement;
1572         } else {
1573                 delta = p->se.avg.runnable_avg_sum;
1574                 *period = p->se.avg.runnable_avg_period;
1575         }
1576 
1577         p->last_sum_exec_runtime = runtime;
1578         p->last_task_numa_placement = now;
1579 
1580         return delta;
1581 }
1582 
1583 static void task_numa_placement(struct task_struct *p)
1584 {
1585         int seq, nid, max_nid = -1, max_group_nid = -1;
1586         unsigned long max_faults = 0, max_group_faults = 0;
1587         unsigned long fault_types[2] = { 0, 0 };
1588         unsigned long total_faults;
1589         u64 runtime, period;
1590         spinlock_t *group_lock = NULL;
1591 
1592         seq = ACCESS_ONCE(p->mm->numa_scan_seq);
1593         if (p->numa_scan_seq == seq)
1594                 return;
1595         p->numa_scan_seq = seq;
1596         p->numa_scan_period_max = task_scan_max(p);
1597 
1598         total_faults = p->numa_faults_locality[0] +
1599                        p->numa_faults_locality[1];
1600         runtime = numa_get_avg_runtime(p, &period);
1601 
1602         /* If the task is part of a group prevent parallel updates to group stats */
1603         if (p->numa_group) {
1604                 group_lock = &p->numa_group->lock;
1605                 spin_lock_irq(group_lock);
1606         }
1607 
1608         /* Find the node with the highest number of faults */
1609         for_each_online_node(nid) {
1610                 unsigned long faults = 0, group_faults = 0;
1611                 int priv, i;
1612 
1613                 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1614                         long diff, f_diff, f_weight;
1615 
1616                         i = task_faults_idx(nid, priv);
1617 
1618                         /* Decay existing window, copy faults since last scan */
1619                         diff = p->numa_faults_buffer_memory[i] - p->numa_faults_memory[i] / 2;
1620                         fault_types[priv] += p->numa_faults_buffer_memory[i];
1621                         p->numa_faults_buffer_memory[i] = 0;
1622 
1623                         /*
1624                          * Normalize the faults_from, so all tasks in a group
1625                          * count according to CPU use, instead of by the raw
1626                          * number of faults. Tasks with little runtime have
1627                          * little over-all impact on throughput, and thus their
1628                          * faults are less important.
1629                          */
1630                         f_weight = div64_u64(runtime << 16, period + 1);
1631                         f_weight = (f_weight * p->numa_faults_buffer_cpu[i]) /
1632                                    (total_faults + 1);
1633                         f_diff = f_weight - p->numa_faults_cpu[i] / 2;
1634                         p->numa_faults_buffer_cpu[i] = 0;
1635 
1636                         p->numa_faults_memory[i] += diff;
1637                         p->numa_faults_cpu[i] += f_diff;
1638                         faults += p->numa_faults_memory[i];
1639                         p->total_numa_faults += diff;
1640                         if (p->numa_group) {
1641                                 /* safe because we can only change our own group */
1642                                 p->numa_group->faults[i] += diff;
1643                                 p->numa_group->faults_cpu[i] += f_diff;
1644                                 p->numa_group->total_faults += diff;
1645                                 group_faults += p->numa_group->faults[i];
1646                         }
1647                 }
1648 
1649                 if (faults > max_faults) {
1650                         max_faults = faults;
1651                         max_nid = nid;
1652                 }
1653 
1654                 if (group_faults > max_group_faults) {
1655                         max_group_faults = group_faults;
1656                         max_group_nid = nid;
1657                 }
1658         }
1659 
1660         update_task_scan_period(p, fault_types[0], fault_types[1]);
1661 
1662         if (p->numa_group) {
1663                 update_numa_active_node_mask(p->numa_group);
1664                 spin_unlock_irq(group_lock);
1665                 max_nid = max_group_nid;
1666         }
1667 
1668         if (max_faults) {
1669                 /* Set the new preferred node */
1670                 if (max_nid != p->numa_preferred_nid)
1671                         sched_setnuma(p, max_nid);
1672 
1673                 if (task_node(p) != p->numa_preferred_nid)
1674                         numa_migrate_preferred(p);
1675         }
1676 }
1677 
1678 static inline int get_numa_group(struct numa_group *grp)
1679 {
1680         return atomic_inc_not_zero(&grp->refcount);
1681 }
1682 
1683 static inline void put_numa_group(struct numa_group *grp)
1684 {
1685         if (atomic_dec_and_test(&grp->refcount))
1686                 kfree_rcu(grp, rcu);
1687 }
1688 
1689 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1690                         int *priv)
1691 {
1692         struct numa_group *grp, *my_grp;
1693         struct task_struct *tsk;
1694         bool join = false;
1695         int cpu = cpupid_to_cpu(cpupid);
1696         int i;
1697 
1698         if (unlikely(!p->numa_group)) {
1699                 unsigned int size = sizeof(struct numa_group) +
1700                                     4*nr_node_ids*sizeof(unsigned long);
1701 
1702                 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1703                 if (!grp)
1704                         return;
1705 
1706                 atomic_set(&grp->refcount, 1);
1707                 spin_lock_init(&grp->lock);
1708                 INIT_LIST_HEAD(&grp->task_list);
1709                 grp->gid = p->pid;
1710                 /* Second half of the array tracks nids where faults happen */
1711                 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1712                                                 nr_node_ids;
1713 
1714                 node_set(task_node(current), grp->active_nodes);
1715 
1716                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1717                         grp->faults[i] = p->numa_faults_memory[i];
1718 
1719                 grp->total_faults = p->total_numa_faults;
1720 
1721                 list_add(&p->numa_entry, &grp->task_list);
1722                 grp->nr_tasks++;
1723                 rcu_assign_pointer(p->numa_group, grp);
1724         }
1725 
1726         rcu_read_lock();
1727         tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);
1728 
1729         if (!cpupid_match_pid(tsk, cpupid))
1730                 goto no_join;
1731 
1732         grp = rcu_dereference(tsk->numa_group);
1733         if (!grp)
1734                 goto no_join;
1735 
1736         my_grp = p->numa_group;
1737         if (grp == my_grp)
1738                 goto no_join;
1739 
1740         /*
1741          * Only join the other group if its bigger; if we're the bigger group,
1742          * the other task will join us.
1743          */
1744         if (my_grp->nr_tasks > grp->nr_tasks)
1745                 goto no_join;
1746 
1747         /*
1748          * Tie-break on the grp address.
1749          */
1750         if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1751                 goto no_join;
1752 
1753         /* Always join threads in the same process. */
1754         if (tsk->mm == current->mm)
1755                 join = true;
1756 
1757         /* Simple filter to avoid false positives due to PID collisions */
1758         if (flags & TNF_SHARED)
1759                 join = true;
1760 
1761         /* Update priv based on whether false sharing was detected */
1762         *priv = !join;
1763 
1764         if (join && !get_numa_group(grp))
1765                 goto no_join;
1766 
1767         rcu_read_unlock();
1768 
1769         if (!join)
1770                 return;
1771 
1772         BUG_ON(irqs_disabled());
1773         double_lock_irq(&my_grp->lock, &grp->lock);
1774 
1775         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
1776                 my_grp->faults[i] -= p->numa_faults_memory[i];
1777                 grp->faults[i] += p->numa_faults_memory[i];
1778         }
1779         my_grp->total_faults -= p->total_numa_faults;
1780         grp->total_faults += p->total_numa_faults;
1781 
1782         list_move(&p->numa_entry, &grp->task_list);
1783         my_grp->nr_tasks--;
1784         grp->nr_tasks++;
1785 
1786         spin_unlock(&my_grp->lock);
1787         spin_unlock_irq(&grp->lock);
1788 
1789         rcu_assign_pointer(p->numa_group, grp);
1790 
1791         put_numa_group(my_grp);
1792         return;
1793 
1794 no_join:
1795         rcu_read_unlock();
1796         return;
1797 }
1798 
1799 void task_numa_free(struct task_struct *p)
1800 {
1801         struct numa_group *grp = p->numa_group;
1802         void *numa_faults = p->numa_faults_memory;
1803         unsigned long flags;
1804         int i;
1805 
1806         if (grp) {
1807                 spin_lock_irqsave(&grp->lock, flags);
1808                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1809                         grp->faults[i] -= p->numa_faults_memory[i];
1810                 grp->total_faults -= p->total_numa_faults;
1811 
1812                 list_del(&p->numa_entry);
1813                 grp->nr_tasks--;
1814                 spin_unlock_irqrestore(&grp->lock, flags);
1815                 RCU_INIT_POINTER(p->numa_group, NULL);
1816                 put_numa_group(grp);
1817         }
1818 
1819         p->numa_faults_memory = NULL;
1820         p->numa_faults_buffer_memory = NULL;
1821         p->numa_faults_cpu= NULL;
1822         p->numa_faults_buffer_cpu = NULL;
1823         kfree(numa_faults);
1824 }
1825 
1826 /*
1827  * Got a PROT_NONE fault for a page on @node.
1828  */
1829 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
1830 {
1831         struct task_struct *p = current;
1832         bool migrated = flags & TNF_MIGRATED;
1833         int cpu_node = task_node(current);
1834         int local = !!(flags & TNF_FAULT_LOCAL);
1835         int priv;
1836 
1837         if (!numabalancing_enabled)
1838                 return;
1839 
1840         /* for example, ksmd faulting in a user's mm */
1841         if (!p->mm)
1842                 return;
1843 
1844         /* Allocate buffer to track faults on a per-node basis */
1845         if (unlikely(!p->numa_faults_memory)) {
1846                 int size = sizeof(*p->numa_faults_memory) *
1847                            NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
1848 
1849                 p->numa_faults_memory = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
1850                 if (!p->numa_faults_memory)
1851                         return;
1852 
1853                 BUG_ON(p->numa_faults_buffer_memory);
1854                 /*
1855                  * The averaged statistics, shared & private, memory & cpu,
1856                  * occupy the first half of the array. The second half of the
1857                  * array is for current counters, which are averaged into the
1858                  * first set by task_numa_placement.
1859                  */
1860                 p->numa_faults_cpu = p->numa_faults_memory + (2 * nr_node_ids);
1861                 p->numa_faults_buffer_memory = p->numa_faults_memory + (4 * nr_node_ids);
1862                 p->numa_faults_buffer_cpu = p->numa_faults_memory + (6 * nr_node_ids);
1863                 p->total_numa_faults = 0;
1864                 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1865         }
1866 
1867         /*
1868          * First accesses are treated as private, otherwise consider accesses
1869          * to be private if the accessing pid has not changed
1870          */
1871         if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
1872                 priv = 1;
1873         } else {
1874                 priv = cpupid_match_pid(p, last_cpupid);
1875                 if (!priv && !(flags & TNF_NO_GROUP))
1876                         task_numa_group(p, last_cpupid, flags, &priv);
1877         }
1878 
1879         /*
1880          * If a workload spans multiple NUMA nodes, a shared fault that
1881          * occurs wholly within the set of nodes that the workload is
1882          * actively using should be counted as local. This allows the
1883          * scan rate to slow down when a workload has settled down.
1884          */
1885         if (!priv && !local && p->numa_group &&
1886                         node_isset(cpu_node, p->numa_group->active_nodes) &&
1887                         node_isset(mem_node, p->numa_group->active_nodes))
1888                 local = 1;
1889 
1890         task_numa_placement(p);
1891 
1892         /*
1893          * Retry task to preferred node migration periodically, in case it
1894          * case it previously failed, or the scheduler moved us.
1895          */
1896         if (time_after(jiffies, p->numa_migrate_retry))
1897                 numa_migrate_preferred(p);
1898 
1899         if (migrated)
1900                 p->numa_pages_migrated += pages;
1901 
1902         p->numa_faults_buffer_memory[task_faults_idx(mem_node, priv)] += pages;
1903         p->numa_faults_buffer_cpu[task_faults_idx(cpu_node, priv)] += pages;
1904         p->numa_faults_locality[local] += pages;
1905 }
1906 
1907 static void reset_ptenuma_scan(struct task_struct *p)
1908 {
1909         ACCESS_ONCE(p->mm->numa_scan_seq)++;
1910         p->mm->numa_scan_offset = 0;
1911 }
1912 
1913 /*
1914  * The expensive part of numa migration is done from task_work context.
1915  * Triggered from task_tick_numa().
1916  */
1917 void task_numa_work(struct callback_head *work)
1918 {
1919         unsigned long migrate, next_scan, now = jiffies;
1920         struct task_struct *p = current;
1921         struct mm_struct *mm = p->mm;
1922         struct vm_area_struct *vma;
1923         unsigned long start, end;
1924         unsigned long nr_pte_updates = 0;
1925         long pages;
1926 
1927         WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
1928 
1929         work->next = work; /* protect against double add */
1930         /*
1931          * Who cares about NUMA placement when they're dying.
1932          *
1933          * NOTE: make sure not to dereference p->mm before this check,
1934          * exit_task_work() happens _after_ exit_mm() so we could be called
1935          * without p->mm even though we still had it when we enqueued this
1936          * work.
1937          */
1938         if (p->flags & PF_EXITING)
1939                 return;
1940 
1941         if (!mm->numa_next_scan) {
1942                 mm->numa_next_scan = now +
1943                         msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
1944         }
1945 
1946         /*
1947          * Enforce maximal scan/migration frequency..
1948          */
1949         migrate = mm->numa_next_scan;
1950         if (time_before(now, migrate))
1951                 return;
1952 
1953         if (p->numa_scan_period == 0) {
1954                 p->numa_scan_period_max = task_scan_max(p);
1955                 p->numa_scan_period = task_scan_min(p);
1956         }
1957 
1958         next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1959         if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
1960                 return;
1961 
1962         /*
1963          * Delay this task enough that another task of this mm will likely win
1964          * the next time around.
1965          */
1966         p->node_stamp += 2 * TICK_NSEC;
1967 
1968         start = mm->numa_scan_offset;
1969         pages = sysctl_numa_balancing_scan_size;
1970         pages <<= 20 - PAGE_SHIFT; /* MB in pages */
1971         if (!pages)
1972                 return;
1973 
1974         down_read(&mm->mmap_sem);
1975         vma = find_vma(mm, start);
1976         if (!vma) {
1977                 reset_ptenuma_scan(p);
1978                 start = 0;
1979                 vma = mm->mmap;
1980         }
1981         for (; vma; vma = vma->vm_next) {
1982                 if (!vma_migratable(vma) || !vma_policy_mof(vma))
1983                         continue;
1984 
1985                 /*
1986                  * Shared library pages mapped by multiple processes are not
1987                  * migrated as it is expected they are cache replicated. Avoid
1988                  * hinting faults in read-only file-backed mappings or the vdso
1989                  * as migrating the pages will be of marginal benefit.
1990                  */
1991                 if (!vma->vm_mm ||
1992                     (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
1993                         continue;
1994 
1995                 /*
1996                  * Skip inaccessible VMAs to avoid any confusion between
1997                  * PROT_NONE and NUMA hinting ptes
1998                  */
1999                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2000                         continue;
2001 
2002                 do {
2003                         start = max(start, vma->vm_start);
2004                         end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2005                         end = min(end, vma->vm_end);
2006                         nr_pte_updates += change_prot_numa(vma, start, end);
2007 
2008                         /*
2009                          * Scan sysctl_numa_balancing_scan_size but ensure that
2010                          * at least one PTE is updated so that unused virtual
2011                          * address space is quickly skipped.
2012                          */
2013                         if (nr_pte_updates)
2014                                 pages -= (end - start) >> PAGE_SHIFT;
2015 
2016                         start = end;
2017                         if (pages <= 0)
2018                                 goto out;
2019 
2020                         cond_resched();
2021                 } while (end != vma->vm_end);
2022         }
2023 
2024 out:
2025         /*
2026          * It is possible to reach the end of the VMA list but the last few
2027          * VMAs are not guaranteed to the vma_migratable. If they are not, we
2028          * would find the !migratable VMA on the next scan but not reset the
2029          * scanner to the start so check it now.
2030          */
2031         if (vma)
2032                 mm->numa_scan_offset = start;
2033         else
2034                 reset_ptenuma_scan(p);
2035         up_read(&mm->mmap_sem);
2036 }
2037 
2038 /*
2039  * Drive the periodic memory faults..
2040  */
2041 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2042 {
2043         struct callback_head *work = &curr->numa_work;
2044         u64 period, now;
2045 
2046         /*
2047          * We don't care about NUMA placement if we don't have memory.
2048          */
2049         if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2050                 return;
2051 
2052         /*
2053          * Using runtime rather than walltime has the dual advantage that
2054          * we (mostly) drive the selection from busy threads and that the
2055          * task needs to have done some actual work before we bother with
2056          * NUMA placement.
2057          */
2058         now = curr->se.sum_exec_runtime;
2059         period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2060 
2061         if (now - curr->node_stamp > period) {
2062                 if (!curr->node_stamp)
2063                         curr->numa_scan_period = task_scan_min(curr);
2064                 curr->node_stamp += period;
2065 
2066                 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2067                         init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2068                         task_work_add(curr, work, true);
2069                 }
2070         }
2071 }
2072 #else
2073 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2074 {
2075 }
2076 
2077 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2078 {
2079 }
2080 
2081 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2082 {
2083 }
2084 #endif /* CONFIG_NUMA_BALANCING */
2085 
2086 static void
2087 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2088 {
2089         update_load_add(&cfs_rq->load, se->load.weight);
2090         if (!parent_entity(se))
2091                 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2092 #ifdef CONFIG_SMP
2093         if (entity_is_task(se)) {
2094                 struct rq *rq = rq_of(cfs_rq);
2095 
2096                 account_numa_enqueue(rq, task_of(se));
2097                 list_add(&se->group_node, &rq->cfs_tasks);
2098         }
2099 #endif
2100         cfs_rq->nr_running++;
2101 }
2102 
2103 static void
2104 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2105 {
2106         update_load_sub(&cfs_rq->load, se->load.weight);
2107         if (!parent_entity(se))
2108                 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2109         if (entity_is_task(se)) {
2110                 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2111                 list_del_init(&se->group_node);
2112         }
2113         cfs_rq->nr_running--;
2114 }
2115 
2116 #ifdef CONFIG_FAIR_GROUP_SCHED
2117 # ifdef CONFIG_SMP
2118 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2119 {
2120         long tg_weight;
2121 
2122         /*
2123          * Use this CPU's actual weight instead of the last load_contribution
2124          * to gain a more accurate current total weight. See
2125          * update_cfs_rq_load_contribution().
2126          */
2127         tg_weight = atomic_long_read(&tg->load_avg);
2128         tg_weight -= cfs_rq->tg_load_contrib;
2129         tg_weight += cfs_rq->load.weight;
2130 
2131         return tg_weight;
2132 }
2133 
2134 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2135 {
2136         long tg_weight, load, shares;
2137 
2138         tg_weight = calc_tg_weight(tg, cfs_rq);
2139         load = cfs_rq->load.weight;
2140 
2141         shares = (tg->shares * load);
2142         if (tg_weight)
2143                 shares /= tg_weight;
2144 
2145         if (shares < MIN_SHARES)
2146                 shares = MIN_SHARES;
2147         if (shares > tg->shares)
2148                 shares = tg->shares;
2149 
2150         return shares;
2151 }
2152 # else /* CONFIG_SMP */
2153 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2154 {
2155         return tg->shares;
2156 }
2157 # endif /* CONFIG_SMP */
2158 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2159                             unsigned long weight)
2160 {
2161         if (se->on_rq) {
2162                 /* commit outstanding execution time */
2163                 if (cfs_rq->curr == se)
2164                         update_curr(cfs_rq);
2165                 account_entity_dequeue(cfs_rq, se);
2166         }
2167 
2168         update_load_set(&se->load, weight);
2169 
2170         if (se->on_rq)
2171                 account_entity_enqueue(cfs_rq, se);
2172 }
2173 
2174 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2175 
2176 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2177 {
2178         struct task_group *tg;
2179         struct sched_entity *se;
2180         long shares;
2181 
2182         tg = cfs_rq->tg;
2183         se = tg->se[cpu_of(rq_of(cfs_rq))];
2184         if (!se || throttled_hierarchy(cfs_rq))
2185                 return;
2186 #ifndef CONFIG_SMP
2187         if (likely(se->load.weight == tg->shares))
2188                 return;
2189 #endif
2190         shares = calc_cfs_shares(cfs_rq, tg);
2191 
2192         reweight_entity(cfs_rq_of(se), se, shares);
2193 }
2194 #else /* CONFIG_FAIR_GROUP_SCHED */
2195 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2196 {
2197 }
2198 #endif /* CONFIG_FAIR_GROUP_SCHED */
2199 
2200 #ifdef CONFIG_SMP
2201 /*
2202  * We choose a half-life close to 1 scheduling period.
2203  * Note: The tables below are dependent on this value.
2204  */
2205 #define LOAD_AVG_PERIOD 32
2206 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
2207 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
2208 
2209 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2210 static const u32 runnable_avg_yN_inv[] = {
2211         0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2212         0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2213         0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2214         0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2215         0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2216         0x85aac367, 0x82cd8698,
2217 };
2218 
2219 /*
2220  * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
2221  * over-estimates when re-combining.
2222  */
2223 static const u32 runnable_avg_yN_sum[] = {
2224             0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2225          9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2226         17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2227 };
2228 
2229 /*
2230  * Approximate:
2231  *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
2232  */
2233 static __always_inline u64 decay_load(u64 val, u64 n)
2234 {
2235         unsigned int local_n;
2236 
2237         if (!n)
2238                 return val;
2239         else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2240                 return 0;
2241 
2242         /* after bounds checking we can collapse to 32-bit */
2243         local_n = n;
2244 
2245         /*
2246          * As y^PERIOD = 1/2, we can combine
2247          *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2248          * With a look-up table which covers y^n (n<PERIOD)
2249          *
2250          * To achieve constant time decay_load.
2251          */
2252         if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2253                 val >>= local_n / LOAD_AVG_PERIOD;
2254                 local_n %= LOAD_AVG_PERIOD;
2255         }
2256 
2257         val *= runnable_avg_yN_inv[local_n];
2258         /* We don't use SRR here since we always want to round down. */
2259         return val >> 32;
2260 }
2261 
2262 /*
2263  * For updates fully spanning n periods, the contribution to runnable
2264  * average will be: \Sum 1024*y^n
2265  *
2266  * We can compute this reasonably efficiently by combining:
2267  *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
2268  */
2269 static u32 __compute_runnable_contrib(u64 n)
2270 {
2271         u32 contrib = 0;
2272 
2273         if (likely(n <= LOAD_AVG_PERIOD))
2274                 return runnable_avg_yN_sum[n];
2275         else if (unlikely(n >= LOAD_AVG_MAX_N))
2276                 return LOAD_AVG_MAX;
2277 
2278         /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2279         do {
2280                 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2281                 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2282 
2283                 n -= LOAD_AVG_PERIOD;
2284         } while (n > LOAD_AVG_PERIOD);
2285 
2286         contrib = decay_load(contrib, n);
2287         return contrib + runnable_avg_yN_sum[n];
2288 }
2289 
2290 /*
2291  * We can represent the historical contribution to runnable average as the
2292  * coefficients of a geometric series.  To do this we sub-divide our runnable
2293  * history into segments of approximately 1ms (1024us); label the segment that
2294  * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2295  *
2296  * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2297  *      p0            p1           p2
2298  *     (now)       (~1ms ago)  (~2ms ago)
2299  *
2300  * Let u_i denote the fraction of p_i that the entity was runnable.
2301  *
2302  * We then designate the fractions u_i as our co-efficients, yielding the
2303  * following representation of historical load:
2304  *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2305  *
2306  * We choose y based on the with of a reasonably scheduling period, fixing:
2307  *   y^32 = 0.5
2308  *
2309  * This means that the contribution to load ~32ms ago (u_32) will be weighted
2310  * approximately half as much as the contribution to load within the last ms
2311  * (u_0).
2312  *
2313  * When a period "rolls over" and we have new u_0`, multiplying the previous
2314  * sum again by y is sufficient to update:
2315  *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2316  *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2317  */
2318 static __always_inline int __update_entity_runnable_avg(u64 now,
2319                                                         struct sched_avg *sa,
2320                                                         int runnable)
2321 {
2322         u64 delta, periods;
2323         u32 runnable_contrib;
2324         int delta_w, decayed = 0;
2325 
2326         delta = now - sa->last_runnable_update;
2327         /*
2328          * This should only happen when time goes backwards, which it
2329          * unfortunately does during sched clock init when we swap over to TSC.
2330          */
2331         if ((s64)delta < 0) {
2332                 sa->last_runnable_update = now;
2333                 return 0;
2334         }
2335 
2336         /*
2337          * Use 1024ns as the unit of measurement since it's a reasonable
2338          * approximation of 1us and fast to compute.
2339          */
2340         delta >>= 10;
2341         if (!delta)
2342                 return 0;
2343         sa->last_runnable_update = now;
2344 
2345         /* delta_w is the amount already accumulated against our next period */
2346         delta_w = sa->runnable_avg_period % 1024;
2347         if (delta + delta_w >= 1024) {
2348                 /* period roll-over */
2349                 decayed = 1;
2350 
2351                 /*
2352                  * Now that we know we're crossing a period boundary, figure
2353                  * out how much from delta we need to complete the current
2354                  * period and accrue it.
2355                  */
2356                 delta_w = 1024 - delta_w;
2357                 if (runnable)
2358                         sa->runnable_avg_sum += delta_w;
2359                 sa->runnable_avg_period += delta_w;
2360 
2361                 delta -= delta_w;
2362 
2363                 /* Figure out how many additional periods this update spans */
2364                 periods = delta / 1024;
2365                 delta %= 1024;
2366 
2367                 sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
2368                                                   periods + 1);
2369                 sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
2370                                                      periods + 1);
2371 
2372                 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2373                 runnable_contrib = __compute_runnable_contrib(periods);
2374                 if (runnable)
2375                         sa->runnable_avg_sum += runnable_contrib;
2376                 sa->runnable_avg_period += runnable_contrib;
2377         }
2378 
2379         /* Remainder of delta accrued against u_0` */
2380         if (runnable)
2381                 sa->runnable_avg_sum += delta;
2382         sa->runnable_avg_period += delta;
2383 
2384         return decayed;
2385 }
2386 
2387 /* Synchronize an entity's decay with its parenting cfs_rq.*/
2388 static inline u64 __synchronize_entity_decay(struct sched_entity *se)
2389 {
2390         struct cfs_rq *cfs_rq = cfs_rq_of(se);
2391         u64 decays = atomic64_read(&cfs_rq->decay_counter);
2392 
2393         decays -= se->avg.decay_count;
2394         if (!decays)
2395                 return 0;
2396 
2397         se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
2398         se->avg.decay_count = 0;
2399 
2400         return decays;
2401 }
2402 
2403 #ifdef CONFIG_FAIR_GROUP_SCHED
2404 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
2405                                                  int force_update)
2406 {
2407         struct task_group *tg = cfs_rq->tg;
2408         long tg_contrib;
2409 
2410         tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
2411         tg_contrib -= cfs_rq->tg_load_contrib;
2412 
2413         if (!tg_contrib)
2414                 return;
2415 
2416         if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
2417                 atomic_long_add(tg_contrib, &tg->load_avg);
2418                 cfs_rq->tg_load_contrib += tg_contrib;
2419         }
2420 }
2421 
2422 /*
2423  * Aggregate cfs_rq runnable averages into an equivalent task_group
2424  * representation for computing load contributions.
2425  */
2426 static inline void __update_tg_runnable_avg(struct sched_avg *sa,
2427                                                   struct cfs_rq *cfs_rq)
2428 {
2429         struct task_group *tg = cfs_rq->tg;
2430         long contrib;
2431 
2432         /* The fraction of a cpu used by this cfs_rq */
2433         contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
2434                           sa->runnable_avg_period + 1);
2435         contrib -= cfs_rq->tg_runnable_contrib;
2436 
2437         if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
2438                 atomic_add(contrib, &tg->runnable_avg);
2439                 cfs_rq->tg_runnable_contrib += contrib;
2440         }
2441 }
2442 
2443 static inline void __update_group_entity_contrib(struct sched_entity *se)
2444 {
2445         struct cfs_rq *cfs_rq = group_cfs_rq(se);
2446         struct task_group *tg = cfs_rq->tg;
2447         int runnable_avg;
2448 
2449         u64 contrib;
2450 
2451         contrib = cfs_rq->tg_load_contrib * tg->shares;
2452         se->avg.load_avg_contrib = div_u64(contrib,
2453                                      atomic_long_read(&tg->load_avg) + 1);
2454 
2455         /*
2456          * For group entities we need to compute a correction term in the case
2457          * that they are consuming <1 cpu so that we would contribute the same
2458          * load as a task of equal weight.
2459          *
2460          * Explicitly co-ordinating this measurement would be expensive, but
2461          * fortunately the sum of each cpus contribution forms a usable
2462          * lower-bound on the true value.
2463          *
2464          * Consider the aggregate of 2 contributions.  Either they are disjoint
2465          * (and the sum represents true value) or they are disjoint and we are
2466          * understating by the aggregate of their overlap.
2467          *
2468          * Extending this to N cpus, for a given overlap, the maximum amount we
2469          * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
2470          * cpus that overlap for this interval and w_i is the interval width.
2471          *
2472          * On a small machine; the first term is well-bounded which bounds the
2473          * total error since w_i is a subset of the period.  Whereas on a
2474          * larger machine, while this first term can be larger, if w_i is the
2475          * of consequential size guaranteed to see n_i*w_i quickly converge to
2476          * our upper bound of 1-cpu.
2477          */
2478         runnable_avg = atomic_read(&tg->runnable_avg);
2479         if (runnable_avg < NICE_0_LOAD) {
2480                 se->avg.load_avg_contrib *= runnable_avg;
2481                 se->avg.load_avg_contrib >>= NICE_0_SHIFT;
2482         }
2483 }
2484 
2485 static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
2486 {
2487         __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
2488         __update_tg_runnable_avg(&rq->avg, &rq->cfs);
2489 }
2490 #else /* CONFIG_FAIR_GROUP_SCHED */
2491 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
2492                                                  int force_update) {}
2493 static inline void __update_tg_runnable_avg(struct sched_avg *sa,
2494                                                   struct cfs_rq *cfs_rq) {}
2495 static inline void __update_group_entity_contrib(struct sched_entity *se) {}
2496 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2497 #endif /* CONFIG_FAIR_GROUP_SCHED */
2498 
2499 static inline void __update_task_entity_contrib(struct sched_entity *se)
2500 {
2501         u32 contrib;
2502 
2503         /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
2504         contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
2505         contrib /= (se->avg.runnable_avg_period + 1);
2506         se->avg.load_avg_contrib = scale_load(contrib);
2507 }
2508 
2509 /* Compute the current contribution to load_avg by se, return any delta */
2510 static long __update_entity_load_avg_contrib(struct sched_entity *se)
2511 {
2512         long old_contrib = se->avg.load_avg_contrib;
2513 
2514         if (entity_is_task(se)) {
2515                 __update_task_entity_contrib(se);
2516         } else {
2517                 __update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
2518                 __update_group_entity_contrib(se);
2519         }
2520 
2521         return se->avg.load_avg_contrib - old_contrib;
2522 }
2523 
2524 static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
2525                                                  long load_contrib)
2526 {
2527         if (likely(load_contrib < cfs_rq->blocked_load_avg))
2528                 cfs_rq->blocked_load_avg -= load_contrib;
2529         else
2530                 cfs_rq->blocked_load_avg = 0;
2531 }
2532 
2533 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2534 
2535 /* Update a sched_entity's runnable average */
2536 static inline void update_entity_load_avg(struct sched_entity *se,
2537                                           int update_cfs_rq)
2538 {
2539         struct cfs_rq *cfs_rq = cfs_rq_of(se);
2540         long contrib_delta;
2541         u64 now;
2542 
2543         /*
2544          * For a group entity we need to use their owned cfs_rq_clock_task() in
2545          * case they are the parent of a throttled hierarchy.
2546          */
2547         if (entity_is_task(se))
2548                 now = cfs_rq_clock_task(cfs_rq);
2549         else
2550                 now = cfs_rq_clock_task(group_cfs_rq(se));
2551 
2552         if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
2553                 return;
2554 
2555         contrib_delta = __update_entity_load_avg_contrib(se);
2556 
2557         if (!update_cfs_rq)
2558                 return;
2559 
2560         if (se->on_rq)
2561                 cfs_rq->runnable_load_avg += contrib_delta;
2562         else
2563                 subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
2564 }
2565 
2566 /*
2567  * Decay the load contributed by all blocked children and account this so that
2568  * their contribution may appropriately discounted when they wake up.
2569  */
2570 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
2571 {
2572         u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
2573         u64 decays;
2574 
2575         decays = now - cfs_rq->last_decay;
2576         if (!decays && !force_update)
2577                 return;
2578 
2579         if (atomic_long_read(&cfs_rq->removed_load)) {
2580                 unsigned long removed_load;
2581                 removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
2582                 subtract_blocked_load_contrib(cfs_rq, removed_load);
2583         }
2584 
2585         if (decays) {
2586                 cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
2587                                                       decays);
2588                 atomic64_add(decays, &cfs_rq->decay_counter);
2589                 cfs_rq->last_decay = now;
2590         }
2591 
2592         __update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
2593 }
2594 
2595 /* Add the load generated by se into cfs_rq's child load-average */
2596 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2597                                                   struct sched_entity *se,
2598                                                   int wakeup)
2599 {
2600         /*
2601          * We track migrations using entity decay_count <= 0, on a wake-up
2602          * migration we use a negative decay count to track the remote decays
2603          * accumulated while sleeping.
2604          *
2605          * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
2606          * are seen by enqueue_entity_load_avg() as a migration with an already
2607          * constructed load_avg_contrib.
2608          */
2609         if (unlikely(se->avg.decay_count <= 0)) {
2610                 se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
2611                 if (se->avg.decay_count) {
2612                         /*
2613                          * In a wake-up migration we have to approximate the
2614                          * time sleeping.  This is because we can't synchronize
2615                          * clock_task between the two cpus, and it is not
2616                          * guaranteed to be read-safe.  Instead, we can
2617                          * approximate this using our carried decays, which are
2618                          * explicitly atomically readable.
2619                          */
2620                         se->avg.last_runnable_update -= (-se->avg.decay_count)
2621                                                         << 20;
2622                         update_entity_load_avg(se, 0);
2623                         /* Indicate that we're now synchronized and on-rq */
2624                         se->avg.decay_count = 0;
2625                 }
2626                 wakeup = 0;
2627         } else {
2628                 __synchronize_entity_decay(se);
2629         }
2630 
2631         /* migrated tasks did not contribute to our blocked load */
2632         if (wakeup) {
2633                 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
2634                 update_entity_load_avg(se, 0);
2635         }
2636 
2637         cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
2638         /* we force update consideration on load-balancer moves */
2639         update_cfs_rq_blocked_load(cfs_rq, !wakeup);
2640 }
2641 
2642 /*
2643  * Remove se's load from this cfs_rq child load-average, if the entity is
2644  * transitioning to a blocked state we track its projected decay using
2645  * blocked_load_avg.
2646  */
2647 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2648                                                   struct sched_entity *se,
2649                                                   int sleep)
2650 {
2651         update_entity_load_avg(se, 1);
2652         /* we force update consideration on load-balancer moves */
2653         update_cfs_rq_blocked_load(cfs_rq, !sleep);
2654 
2655         cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
2656         if (sleep) {
2657                 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
2658                 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
2659         } /* migrations, e.g. sleep=0 leave decay_count == 0 */
2660 }
2661 
2662 /*
2663  * Update the rq's load with the elapsed running time before entering
2664  * idle. if the last scheduled task is not a CFS task, idle_enter will
2665  * be the only way to update the runnable statistic.
2666  */
2667 void idle_enter_fair(struct rq *this_rq)
2668 {
2669         update_rq_runnable_avg(this_rq, 1);
2670 }
2671 
2672 /*
2673  * Update the rq's load with the elapsed idle time before a task is
2674  * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2675  * be the only way to update the runnable statistic.
2676  */
2677 void idle_exit_fair(struct rq *this_rq)
2678 {
2679         update_rq_runnable_avg(this_rq, 0);
2680 }
2681 
2682 static int idle_balance(struct rq *this_rq);
2683 
2684 #else /* CONFIG_SMP */
2685 
2686 static inline void update_entity_load_avg(struct sched_entity *se,
2687                                           int update_cfs_rq) {}
2688 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2689 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2690                                            struct sched_entity *se,
2691                                            int wakeup) {}
2692 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2693                                            struct sched_entity *se,
2694                                            int sleep) {}
2695 static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
2696                                               int force_update) {}
2697 
2698 static inline int idle_balance(struct rq *rq)
2699 {
2700         return 0;
2701 }
2702 
2703 #endif /* CONFIG_SMP */
2704 
2705 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2706 {
2707 #ifdef CONFIG_SCHEDSTATS
2708         struct task_struct *tsk = NULL;
2709 
2710         if (entity_is_task(se))
2711                 tsk = task_of(se);
2712 
2713         if (se->statistics.sleep_start) {
2714                 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2715 
2716                 if ((s64)delta < 0)
2717                         delta = 0;
2718 
2719                 if (unlikely(delta > se->statistics.sleep_max))
2720                         se->statistics.sleep_max = delta;
2721 
2722                 se->statistics.sleep_start = 0;
2723                 se->statistics.sum_sleep_runtime += delta;
2724 
2725                 if (tsk) {
2726                         account_scheduler_latency(tsk, delta >> 10, 1);
2727                         trace_sched_stat_sleep(tsk, delta);
2728                 }
2729         }
2730         if (se->statistics.block_start) {
2731                 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2732 
2733                 if ((s64)delta < 0)
2734                         delta = 0;
2735 
2736                 if (unlikely(delta > se->statistics.block_max))
2737                         se->statistics.block_max = delta;
2738 
2739                 se->statistics.block_start = 0;
2740                 se->statistics.sum_sleep_runtime += delta;
2741 
2742                 if (tsk) {
2743                         if (tsk->in_iowait) {
2744                                 se->statistics.iowait_sum += delta;
2745                                 se->statistics.iowait_count++;
2746                                 trace_sched_stat_iowait(tsk, delta);
2747                         }
2748 
2749                         trace_sched_stat_blocked(tsk, delta);
2750 
2751                         /*
2752                          * Blocking time is in units of nanosecs, so shift by
2753                          * 20 to get a milliseconds-range estimation of the
2754                          * amount of time that the task spent sleeping:
2755                          */
2756                         if (unlikely(prof_on == SLEEP_PROFILING)) {
2757                                 profile_hits(SLEEP_PROFILING,
2758                                                 (void *)get_wchan(tsk),
2759                                                 delta >> 20);
2760                         }
2761                         account_scheduler_latency(tsk, delta >> 10, 0);
2762                 }
2763         }
2764 #endif
2765 }
2766 
2767 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2768 {
2769 #ifdef CONFIG_SCHED_DEBUG
2770         s64 d = se->vruntime - cfs_rq->min_vruntime;
2771 
2772         if (d < 0)
2773                 d = -d;
2774 
2775         if (d > 3*sysctl_sched_latency)
2776                 schedstat_inc(cfs_rq, nr_spread_over);
2777 #endif
2778 }
2779 
2780 static void
2781 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2782 {
2783         u64 vruntime = cfs_rq->min_vruntime;
2784 
2785         /*
2786          * The 'current' period is already promised to the current tasks,
2787          * however the extra weight of the new task will slow them down a
2788          * little, place the new task so that it fits in the slot that
2789          * stays open at the end.
2790          */
2791         if (initial && sched_feat(START_DEBIT))
2792                 vruntime += sched_vslice(cfs_rq, se);
2793 
2794         /* sleeps up to a single latency don't count. */
2795         if (!initial) {
2796                 unsigned long thresh = sysctl_sched_latency;
2797 
2798                 /*
2799                  * Halve their sleep time's effect, to allow
2800                  * for a gentler effect of sleepers:
2801                  */
2802                 if (sched_feat(GENTLE_FAIR_SLEEPERS))
2803                         thresh >>= 1;
2804 
2805                 vruntime -= thresh;
2806         }
2807 
2808         /* ensure we never gain time by being placed backwards. */
2809         se->vruntime = max_vruntime(se->vruntime, vruntime);
2810 }
2811 
2812 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
2813 
2814 static void
2815 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2816 {
2817         /*
2818          * Update the normalized vruntime before updating min_vruntime
2819          * through calling update_curr().
2820          */
2821         if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2822                 se->vruntime += cfs_rq->min_vruntime;
2823 
2824         /*
2825          * Update run-time statistics of the 'current'.
2826          */
2827         update_curr(cfs_rq);
2828         enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
2829         account_entity_enqueue(cfs_rq, se);
2830         update_cfs_shares(cfs_rq);
2831 
2832         if (flags & ENQUEUE_WAKEUP) {
2833                 place_entity(cfs_rq, se, 0);
2834                 enqueue_sleeper(cfs_rq, se);
2835         }
2836 
2837         update_stats_enqueue(cfs_rq, se);
2838         check_spread(cfs_rq, se);
2839         if (se != cfs_rq->curr)
2840                 __enqueue_entity(cfs_rq, se);
2841         se->on_rq = 1;
2842 
2843         if (cfs_rq->nr_running == 1) {
2844                 list_add_leaf_cfs_rq(cfs_rq);
2845                 check_enqueue_throttle(cfs_rq);
2846         }
2847 }
2848 
2849 static void __clear_buddies_last(struct sched_entity *se)
2850 {
2851         for_each_sched_entity(se) {
2852                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2853                 if (cfs_rq->last != se)
2854                         break;
2855 
2856                 cfs_rq->last = NULL;
2857         }
2858 }
2859 
2860 static void __clear_buddies_next(struct sched_entity *se)
2861 {
2862         for_each_sched_entity(se) {
2863                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2864                 if (cfs_rq->next != se)
2865                         break;
2866 
2867                 cfs_rq->next = NULL;
2868         }
2869 }
2870 
2871 static void __clear_buddies_skip(struct sched_entity *se)
2872 {
2873         for_each_sched_entity(se) {
2874                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2875                 if (cfs_rq->skip != se)
2876                         break;
2877 
2878                 cfs_rq->skip = NULL;
2879         }
2880 }
2881 
2882 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
2883 {
2884         if (cfs_rq->last == se)
2885                 __clear_buddies_last(se);
2886 
2887         if (cfs_rq->next == se)
2888                 __clear_buddies_next(se);
2889 
2890         if (cfs_rq->skip == se)
2891                 __clear_buddies_skip(se);
2892 }
2893 
2894 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2895 
2896 static void
2897 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2898 {
2899         /*
2900          * Update run-time statistics of the 'current'.
2901          */
2902         update_curr(cfs_rq);
2903         dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2904 
2905         update_stats_dequeue(cfs_rq, se);
2906         if (flags & DEQUEUE_SLEEP) {
2907 #ifdef CONFIG_SCHEDSTATS
2908                 if (entity_is_task(se)) {
2909                         struct task_struct *tsk = task_of(se);
2910 
2911                         if (tsk->state & TASK_INTERRUPTIBLE)
2912                                 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2913                         if (tsk->state & TASK_UNINTERRUPTIBLE)
2914                                 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2915                 }
2916 #endif
2917         }
2918 
2919         clear_buddies(cfs_rq, se);
2920 
2921         if (se != cfs_rq->curr)
2922                 __dequeue_entity(cfs_rq, se);
2923         se->on_rq = 0;
2924         account_entity_dequeue(cfs_rq, se);
2925 
2926         /*
2927          * Normalize the entity after updating the min_vruntime because the
2928          * update can refer to the ->curr item and we need to reflect this
2929          * movement in our normalized position.
2930          */
2931         if (!(flags & DEQUEUE_SLEEP))
2932                 se->vruntime -= cfs_rq->min_vruntime;
2933 
2934         /* return excess runtime on last dequeue */
2935         return_cfs_rq_runtime(cfs_rq);
2936 
2937         update_min_vruntime(cfs_rq);
2938         update_cfs_shares(cfs_rq);
2939 }
2940 
2941 /*
2942  * Preempt the current task with a newly woken task if needed:
2943  */
2944 static void
2945 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2946 {
2947         unsigned long ideal_runtime, delta_exec;
2948         struct sched_entity *se;
2949         s64 delta;
2950 
2951         ideal_runtime = sched_slice(cfs_rq, curr);
2952         delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2953         if (delta_exec > ideal_runtime) {
2954                 resched_curr(rq_of(cfs_rq));
2955                 /*
2956                  * The current task ran long enough, ensure it doesn't get
2957                  * re-elected due to buddy favours.
2958                  */
2959                 clear_buddies(cfs_rq, curr);
2960                 return;
2961         }
2962 
2963         /*
2964          * Ensure that a task that missed wakeup preemption by a
2965          * narrow margin doesn't have to wait for a full slice.
2966          * This also mitigates buddy induced latencies under load.
2967          */
2968         if (delta_exec < sysctl_sched_min_granularity)
2969                 return;
2970 
2971         se = __pick_first_entity(cfs_rq);
2972         delta = curr->vruntime - se->vruntime;
2973 
2974         if (delta < 0)
2975                 return;
2976 
2977         if (delta > ideal_runtime)
2978                 resched_curr(rq_of(cfs_rq));
2979 }
2980 
2981 static void
2982 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2983 {
2984         /* 'current' is not kept within the tree. */
2985         if (se->on_rq) {
2986                 /*
2987                  * Any task has to be enqueued before it get to execute on
2988                  * a CPU. So account for the time it spent waiting on the
2989                  * runqueue.
2990                  */
2991                 update_stats_wait_end(cfs_rq, se);
2992                 __dequeue_entity(cfs_rq, se);
2993         }
2994 
2995         update_stats_curr_start(cfs_rq, se);
2996         cfs_rq->curr = se;
2997 #ifdef CONFIG_SCHEDSTATS
2998         /*
2999          * Track our maximum slice length, if the CPU's load is at
3000          * least twice that of our own weight (i.e. dont track it
3001          * when there are only lesser-weight tasks around):
3002          */
3003         if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3004                 se->statistics.slice_max = max(se->statistics.slice_max,
3005                         se->sum_exec_runtime - se->prev_sum_exec_runtime);
3006         }
3007 #endif
3008         se->prev_sum_exec_runtime = se->sum_exec_runtime;
3009 }
3010 
3011 static int
3012 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3013 
3014 /*
3015  * Pick the next process, keeping these things in mind, in this order:
3016  * 1) keep things fair between processes/task groups
3017  * 2) pick the "next" process, since someone really wants that to run
3018  * 3) pick the "last" process, for cache locality
3019  * 4) do not run the "skip" process, if something else is available
3020  */
3021 static struct sched_entity *
3022 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3023 {
3024         struct sched_entity *left = __pick_first_entity(cfs_rq);
3025         struct sched_entity *se;
3026 
3027         /*
3028          * If curr is set we have to see if its left of the leftmost entity
3029          * still in the tree, provided there was anything in the tree at all.
3030          */
3031         if (!left || (curr && entity_before(curr, left)))
3032                 left = curr;
3033 
3034         se = left; /* ideally we run the leftmost entity */
3035 
3036         /*
3037          * Avoid running the skip buddy, if running something else can
3038          * be done without getting too unfair.
3039          */
3040         if (cfs_rq->skip == se) {
3041                 struct sched_entity *second;
3042 
3043                 if (se == curr) {
3044                         second = __pick_first_entity(cfs_rq);
3045                 } else {
3046                         second = __pick_next_entity(se);
3047                         if (!second || (curr && entity_before(curr, second)))
3048                                 second = curr;
3049                 }
3050 
3051                 if (second && wakeup_preempt_entity(second, left) < 1)
3052                         se = second;
3053         }
3054 
3055         /*
3056          * Prefer last buddy, try to return the CPU to a preempted task.
3057          */
3058         if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3059                 se = cfs_rq->last;
3060 
3061         /*
3062          * Someone really wants this to run. If it's not unfair, run it.
3063          */
3064         if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3065                 se = cfs_rq->next;
3066 
3067         clear_buddies(cfs_rq, se);
3068 
3069         return se;
3070 }
3071 
3072 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3073 
3074 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3075 {
3076         /*
3077          * If still on the runqueue then deactivate_task()
3078          * was not called and update_curr() has to be done:
3079          */
3080         if (prev->on_rq)
3081                 update_curr(cfs_rq);
3082 
3083         /* throttle cfs_rqs exceeding runtime */
3084         check_cfs_rq_runtime(cfs_rq);
3085 
3086         check_spread(cfs_rq, prev);
3087         if (prev->on_rq) {
3088                 update_stats_wait_start(cfs_rq, prev);
3089                 /* Put 'current' back into the tree. */
3090                 __enqueue_entity(cfs_rq, prev);
3091                 /* in !on_rq case, update occurred at dequeue */
3092                 update_entity_load_avg(prev, 1);
3093         }
3094         cfs_rq->curr = NULL;
3095 }
3096 
3097 static void
3098 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3099 {
3100         /*
3101          * Update run-time statistics of the 'current'.
3102          */
3103         update_curr(cfs_rq);
3104 
3105         /*
3106          * Ensure that runnable average is periodically updated.
3107          */
3108         update_entity_load_avg(curr, 1);
3109         update_cfs_rq_blocked_load(cfs_rq, 1);
3110         update_cfs_shares(cfs_rq);
3111 
3112 #ifdef CONFIG_SCHED_HRTICK
3113         /*
3114          * queued ticks are scheduled to match the slice, so don't bother
3115          * validating it and just reschedule.
3116          */
3117         if (queued) {
3118                 resched_curr(rq_of(cfs_rq));
3119                 return;
3120         }
3121         /*
3122          * don't let the period tick interfere with the hrtick preemption
3123          */
3124         if (!sched_feat(DOUBLE_TICK) &&
3125                         hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3126                 return;
3127 #endif
3128 
3129         if (cfs_rq->nr_running > 1)
3130                 check_preempt_tick(cfs_rq, curr);
3131 }
3132 
3133 
3134 /**************************************************
3135  * CFS bandwidth control machinery
3136  */
3137 
3138 #ifdef CONFIG_CFS_BANDWIDTH
3139 
3140 #ifdef HAVE_JUMP_LABEL
3141 static struct static_key __cfs_bandwidth_used;
3142 
3143 static inline bool cfs_bandwidth_used(void)
3144 {
3145         return static_key_false(&__cfs_bandwidth_used);
3146 }
3147 
3148 void cfs_bandwidth_usage_inc(void)
3149 {
3150         static_key_slow_inc(&__cfs_bandwidth_used);
3151 }
3152 
3153 void cfs_bandwidth_usage_dec(void)
3154 {
3155         static_key_slow_dec(&__cfs_bandwidth_used);
3156 }
3157 #else /* HAVE_JUMP_LABEL */
3158 static bool cfs_bandwidth_used(void)
3159 {
3160         return true;
3161 }
3162 
3163 void cfs_bandwidth_usage_inc(void) {}
3164 void cfs_bandwidth_usage_dec(void) {}
3165 #endif /* HAVE_JUMP_LABEL */
3166 
3167 /*
3168  * default period for cfs group bandwidth.
3169  * default: 0.1s, units: nanoseconds
3170  */
3171 static inline u64 default_cfs_period(void)
3172 {
3173         return 100000000ULL;
3174 }
3175 
3176 static inline u64 sched_cfs_bandwidth_slice(void)
3177 {
3178         return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3179 }
3180 
3181 /*
3182  * Replenish runtime according to assigned quota and update expiration time.
3183  * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3184  * additional synchronization around rq->lock.
3185  *
3186  * requires cfs_b->lock
3187  */
3188 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3189 {
3190         u64 now;
3191 
3192         if (cfs_b->quota == RUNTIME_INF)
3193                 return;
3194 
3195         now = sched_clock_cpu(smp_processor_id());
3196         cfs_b->runtime = cfs_b->quota;
3197         cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3198 }
3199 
3200 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3201 {
3202         return &tg->cfs_bandwidth;
3203 }
3204 
3205 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3206 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3207 {
3208         if (unlikely(cfs_rq->throttle_count))
3209                 return cfs_rq->throttled_clock_task;
3210 
3211         return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3212 }
3213 
3214 /* returns 0 on failure to allocate runtime */
3215 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3216 {
3217         struct task_group *tg = cfs_rq->tg;
3218         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3219         u64 amount = 0, min_amount, expires;
3220 
3221         /* note: this is a positive sum as runtime_remaining <= 0 */
3222         min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3223 
3224         raw_spin_lock(&cfs_b->lock);
3225         if (cfs_b->quota == RUNTIME_INF)
3226                 amount = min_amount;
3227         else {
3228                 /*
3229                  * If the bandwidth pool has become inactive, then at least one
3230                  * period must have elapsed since the last consumption.
3231                  * Refresh the global state and ensure bandwidth timer becomes
3232                  * active.
3233                  */
3234                 if (!cfs_b->timer_active) {
3235                         __refill_cfs_bandwidth_runtime(cfs_b);
3236                         __start_cfs_bandwidth(cfs_b, false);
3237                 }
3238 
3239                 if (cfs_b->runtime > 0) {
3240                         amount = min(cfs_b->runtime, min_amount);
3241                         cfs_b->runtime -= amount;
3242                         cfs_b->idle = 0;
3243                 }
3244         }
3245         expires = cfs_b->runtime_expires;
3246         raw_spin_unlock(&cfs_b->lock);
3247 
3248         cfs_rq->runtime_remaining += amount;
3249         /*
3250          * we may have advanced our local expiration to account for allowed
3251          * spread between our sched_clock and the one on which runtime was
3252          * issued.
3253          */
3254         if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3255                 cfs_rq->runtime_expires = expires;
3256 
3257         return cfs_rq->runtime_remaining > 0;
3258 }
3259 
3260 /*
3261  * Note: This depends on the synchronization provided by sched_clock and the
3262  * fact that rq->clock snapshots this value.
3263  */
3264 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3265 {
3266         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3267 
3268         /* if the deadline is ahead of our clock, nothing to do */
3269         if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3270                 return;
3271 
3272         if (cfs_rq->runtime_remaining < 0)
3273                 return;
3274 
3275         /*
3276          * If the local deadline has passed we have to consider the
3277          * possibility that our sched_clock is 'fast' and the global deadline
3278          * has not truly expired.
3279          *
3280          * Fortunately we can check determine whether this the case by checking
3281          * whether the global deadline has advanced. It is valid to compare
3282          * cfs_b->runtime_expires without any locks since we only care about
3283          * exact equality, so a partial write will still work.
3284          */
3285 
3286         if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3287                 /* extend local deadline, drift is bounded above by 2 ticks */
3288                 cfs_rq->runtime_expires += TICK_NSEC;
3289         } else {
3290                 /* global deadline is ahead, expiration has passed */
3291                 cfs_rq->runtime_remaining = 0;
3292         }
3293 }
3294 
3295 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3296 {
3297         /* dock delta_exec before expiring quota (as it could span periods) */
3298         cfs_rq->runtime_remaining -= delta_exec;
3299         expire_cfs_rq_runtime(cfs_rq);
3300 
3301         if (likely(cfs_rq->runtime_remaining > 0))
3302                 return;
3303 
3304         /*
3305          * if we're unable to extend our runtime we resched so that the active
3306          * hierarchy can be throttled
3307          */
3308         if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3309                 resched_curr(rq_of(cfs_rq));
3310 }
3311 
3312 static __always_inline
3313 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3314 {
3315         if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3316                 return;
3317 
3318         __account_cfs_rq_runtime(cfs_rq, delta_exec);
3319 }
3320 
3321 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3322 {
3323         return cfs_bandwidth_used() && cfs_rq->throttled;
3324 }
3325 
3326 /* check whether cfs_rq, or any parent, is throttled */
3327 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3328 {
3329         return cfs_bandwidth_used() && cfs_rq->throttle_count;
3330 }
3331 
3332 /*
3333  * Ensure that neither of the group entities corresponding to src_cpu or
3334  * dest_cpu are members of a throttled hierarchy when performing group
3335  * load-balance operations.
3336  */
3337 static inline int throttled_lb_pair(struct task_group *tg,
3338                                     int src_cpu, int dest_cpu)
3339 {
3340         struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3341 
3342         src_cfs_rq = tg->cfs_rq[src_cpu];
3343         dest_cfs_rq = tg->cfs_rq[dest_cpu];
3344 
3345         return throttled_hierarchy(src_cfs_rq) ||
3346                throttled_hierarchy(dest_cfs_rq);
3347 }
3348 
3349 /* updated child weight may affect parent so we have to do this bottom up */
3350 static int tg_unthrottle_up(struct task_group *tg, void *data)
3351 {
3352         struct rq *rq = data;
3353         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3354 
3355         cfs_rq->throttle_count--;
3356 #ifdef CONFIG_SMP
3357         if (!cfs_rq->throttle_count) {
3358                 /* adjust cfs_rq_clock_task() */
3359                 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3360                                              cfs_rq->throttled_clock_task;
3361         }
3362 #endif
3363 
3364         return 0;
3365 }
3366 
3367 static int tg_throttle_down(struct task_group *tg, void *data)
3368 {
3369         struct rq *rq = data;
3370         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3371 
3372         /* group is entering throttled state, stop time */
3373         if (!cfs_rq->throttle_count)
3374                 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3375         cfs_rq->throttle_count++;
3376 
3377         return 0;
3378 }
3379 
3380 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3381 {
3382         struct rq *rq = rq_of(cfs_rq);
3383         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3384         struct sched_entity *se;
3385         long task_delta, dequeue = 1;
3386 
3387         se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3388 
3389         /* freeze hierarchy runnable averages while throttled */
3390         rcu_read_lock();
3391         walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3392         rcu_read_unlock();
3393 
3394         task_delta = cfs_rq->h_nr_running;
3395         for_each_sched_entity(se) {
3396                 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3397                 /* throttled entity or throttle-on-deactivate */
3398                 if (!se->on_rq)
3399                         break;
3400 
3401                 if (dequeue)
3402                         dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3403                 qcfs_rq->h_nr_running -= task_delta;
3404 
3405                 if (qcfs_rq->load.weight)
3406                         dequeue = 0;
3407         }
3408 
3409         if (!se)
3410                 sub_nr_running(rq, task_delta);
3411 
3412         cfs_rq->throttled = 1;
3413         cfs_rq->throttled_clock = rq_clock(rq);
3414         raw_spin_lock(&cfs_b->lock);
3415         /*
3416          * Add to the _head_ of the list, so that an already-started
3417          * distribute_cfs_runtime will not see us
3418          */
3419         list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3420         if (!cfs_b->timer_active)
3421                 __start_cfs_bandwidth(cfs_b, false);
3422         raw_spin_unlock(&cfs_b->lock);
3423 }
3424 
3425 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3426 {
3427         struct rq *rq = rq_of(cfs_rq);
3428         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3429         struct sched_entity *se;
3430         int enqueue = 1;
3431         long task_delta;
3432 
3433         se = cfs_rq->tg->se[cpu_of(rq)];
3434 
3435         cfs_rq->throttled = 0;
3436 
3437         update_rq_clock(rq);
3438 
3439         raw_spin_lock(&cfs_b->lock);
3440         cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3441         list_del_rcu(&cfs_rq->throttled_list);
3442         raw_spin_unlock(&cfs_b->lock);
3443 
3444         /* update hierarchical throttle state */
3445         walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3446 
3447         if (!cfs_rq->load.weight)
3448                 return;
3449 
3450         task_delta = cfs_rq->h_nr_running;
3451         for_each_sched_entity(se) {
3452                 if (se->on_rq)
3453                         enqueue = 0;
3454 
3455                 cfs_rq = cfs_rq_of(se);
3456                 if (enqueue)
3457                         enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3458                 cfs_rq->h_nr_running += task_delta;
3459 
3460                 if (cfs_rq_throttled(cfs_rq))
3461                         break;
3462         }
3463 
3464         if (!se)
3465                 add_nr_running(rq, task_delta);
3466 
3467         /* determine whether we need to wake up potentially idle cpu */
3468         if (rq->curr == rq->idle && rq->cfs.nr_running)
3469                 resched_curr(rq);
3470 }
3471 
3472 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3473                 u64 remaining, u64 expires)
3474 {
3475         struct cfs_rq *cfs_rq;
3476         u64 runtime;
3477         u64 starting_runtime = remaining;
3478 
3479         rcu_read_lock();
3480         list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3481                                 throttled_list) {
3482                 struct rq *rq = rq_of(cfs_rq);
3483 
3484                 raw_spin_lock(&rq->lock);
3485                 if (!cfs_rq_throttled(cfs_rq))
3486                         goto next;
3487 
3488                 runtime = -cfs_rq->runtime_remaining + 1;
3489                 if (runtime > remaining)
3490                         runtime = remaining;
3491                 remaining -= runtime;
3492 
3493                 cfs_rq->runtime_remaining += runtime;
3494                 cfs_rq->runtime_expires = expires;
3495 
3496                 /* we check whether we're throttled above */
3497                 if (cfs_rq->runtime_remaining > 0)
3498                         unthrottle_cfs_rq(cfs_rq);
3499 
3500 next:
3501                 raw_spin_unlock(&rq->lock);
3502 
3503                 if (!remaining)
3504                         break;
3505         }
3506         rcu_read_unlock();
3507 
3508         return starting_runtime - remaining;
3509 }
3510 
3511 /*
3512  * Responsible for refilling a task_group's bandwidth and unthrottling its
3513  * cfs_rqs as appropriate. If there has been no activity within the last
3514  * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3515  * used to track this state.
3516  */
3517 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3518 {
3519         u64 runtime, runtime_expires;
3520         int throttled;
3521 
3522         /* no need to continue the timer with no bandwidth constraint */
3523         if (cfs_b->quota == RUNTIME_INF)
3524                 goto out_deactivate;
3525 
3526         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3527         cfs_b->nr_periods += overrun;
3528 
3529         /*
3530          * idle depends on !throttled (for the case of a large deficit), and if
3531          * we're going inactive then everything else can be deferred
3532          */
3533         if (cfs_b->idle && !throttled)
3534                 goto out_deactivate;
3535 
3536         /*
3537          * if we have relooped after returning idle once, we need to update our
3538          * status as actually running, so that other cpus doing
3539          * __start_cfs_bandwidth will stop trying to cancel us.
3540          */
3541         cfs_b->timer_active = 1;
3542 
3543         __refill_cfs_bandwidth_runtime(cfs_b);
3544 
3545         if (!throttled) {
3546                 /* mark as potentially idle for the upcoming period */
3547                 cfs_b->idle = 1;
3548                 return 0;
3549         }
3550 
3551         /* account preceding periods in which throttling occurred */
3552         cfs_b->nr_throttled += overrun;
3553 
3554         runtime_expires = cfs_b->runtime_expires;
3555 
3556         /*
3557          * This check is repeated as we are holding onto the new bandwidth while
3558          * we unthrottle. This can potentially race with an unthrottled group
3559          * trying to acquire new bandwidth from the global pool. This can result
3560          * in us over-using our runtime if it is all used during this loop, but
3561          * only by limited amounts in that extreme case.
3562          */
3563         while (throttled && cfs_b->runtime > 0) {
3564                 runtime = cfs_b->runtime;
3565                 raw_spin_unlock(&cfs_b->lock);
3566                 /* we can't nest cfs_b->lock while distributing bandwidth */
3567                 runtime = distribute_cfs_runtime(cfs_b, runtime,
3568                                                  runtime_expires);
3569                 raw_spin_lock(&cfs_b->lock);
3570 
3571                 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3572 
3573                 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3574         }
3575 
3576         /*
3577          * While we are ensured activity in the period following an
3578          * unthrottle, this also covers the case in which the new bandwidth is
3579          * insufficient to cover the existing bandwidth deficit.  (Forcing the
3580          * timer to remain active while there are any throttled entities.)
3581          */
3582         cfs_b->idle = 0;
3583 
3584         return 0;
3585 
3586 out_deactivate:
3587         cfs_b->timer_active = 0;
3588         return 1;
3589 }
3590 
3591 /* a cfs_rq won't donate quota below this amount */
3592 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3593 /* minimum remaining period time to redistribute slack quota */
3594 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3595 /* how long we wait to gather additional slack before distributing */
3596 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3597 
3598 /*
3599  * Are we near the end of the current quota period?
3600  *
3601  * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3602  * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
3603  * migrate_hrtimers, base is never cleared, so we are fine.
3604  */
3605 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3606 {
3607         struct hrtimer *refresh_timer = &cfs_b->period_timer;
3608         u64 remaining;
3609 
3610         /* if the call-back is running a quota refresh is already occurring */
3611         if (hrtimer_callback_running(refresh_timer))
3612                 return 1;
3613 
3614         /* is a quota refresh about to occur? */
3615         remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3616         if (remaining < min_expire)
3617                 return 1;
3618 
3619         return 0;
3620 }
3621 
3622 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3623 {
3624         u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3625 
3626         /* if there's a quota refresh soon don't bother with slack */
3627         if (runtime_refresh_within(cfs_b, min_left))
3628                 return;
3629 
3630         start_bandwidth_timer(&cfs_b->slack_timer,
3631                                 ns_to_ktime(cfs_bandwidth_slack_period));
3632 }
3633 
3634 /* we know any runtime found here is valid as update_curr() precedes return */
3635 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3636 {
3637         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3638         s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3639 
3640         if (slack_runtime <= 0)
3641                 return;
3642 
3643         raw_spin_lock(&cfs_b->lock);
3644         if (cfs_b->quota != RUNTIME_INF &&
3645             cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3646                 cfs_b->runtime += slack_runtime;
3647 
3648                 /* we are under rq->lock, defer unthrottling using a timer */
3649                 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3650                     !list_empty(&cfs_b->throttled_cfs_rq))
3651                         start_cfs_slack_bandwidth(cfs_b);
3652         }
3653         raw_spin_unlock(&cfs_b->lock);
3654 
3655         /* even if it's not valid for return we don't want to try again */
3656         cfs_rq->runtime_remaining -= slack_runtime;
3657 }
3658 
3659 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3660 {
3661         if (!cfs_bandwidth_used())
3662                 return;
3663 
3664         if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3665                 return;
3666 
3667         __return_cfs_rq_runtime(cfs_rq);
3668 }
3669 
3670 /*
3671  * This is done with a timer (instead of inline with bandwidth return) since
3672  * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3673  */
3674 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3675 {
3676         u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3677         u64 expires;
3678 
3679         /* confirm we're still not at a refresh boundary */
3680         raw_spin_lock(&cfs_b->lock);
3681         if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3682                 raw_spin_unlock(&cfs_b->lock);
3683                 return;
3684         }
3685 
3686         if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3687                 runtime = cfs_b->runtime;
3688 
3689         expires = cfs_b->runtime_expires;
3690         raw_spin_unlock(&cfs_b->lock);
3691 
3692         if (!runtime)
3693                 return;
3694 
3695         runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3696 
3697         raw_spin_lock(&cfs_b->lock);
3698         if (expires == cfs_b->runtime_expires)
3699                 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3700         raw_spin_unlock(&cfs_b->lock);
3701 }
3702 
3703 /*
3704  * When a group wakes up we want to make sure that its quota is not already
3705  * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3706  * runtime as update_curr() throttling can not not trigger until it's on-rq.
3707  */
3708 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3709 {
3710         if (!cfs_bandwidth_used())
3711                 return;
3712 
3713         /* an active group must be handled by the update_curr()->put() path */
3714         if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3715                 return;
3716 
3717         /* ensure the group is not already throttled */
3718         if (cfs_rq_throttled(cfs_rq))
3719                 return;
3720 
3721         /* update runtime allocation */
3722         account_cfs_rq_runtime(cfs_rq, 0);
3723         if (cfs_rq->runtime_remaining <= 0)
3724                 throttle_cfs_rq(cfs_rq);
3725 }
3726 
3727 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3728 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3729 {
3730         if (!cfs_bandwidth_used())
3731                 return false;
3732 
3733         if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3734                 return false;
3735 
3736         /*
3737          * it's possible for a throttled entity to be forced into a running
3738          * state (e.g. set_curr_task), in this case we're finished.
3739          */
3740         if (cfs_rq_throttled(cfs_rq))
3741                 return true;
3742 
3743         throttle_cfs_rq(cfs_rq);
3744         return true;
3745 }
3746 
3747 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3748 {
3749         struct cfs_bandwidth *cfs_b =
3750                 container_of(timer, struct cfs_bandwidth, slack_timer);
3751         do_sched_cfs_slack_timer(cfs_b);
3752 
3753         return HRTIMER_NORESTART;
3754 }
3755 
3756 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3757 {
3758         struct cfs_bandwidth *cfs_b =
3759                 container_of(timer, struct cfs_bandwidth, period_timer);
3760         ktime_t now;
3761         int overrun;
3762         int idle = 0;
3763 
3764         raw_spin_lock(&cfs_b->lock);
3765         for (;;) {
3766                 now = hrtimer_cb_get_time(timer);
3767                 overrun = hrtimer_forward(timer, now, cfs_b->period);
3768 
3769                 if (!overrun)
3770                         break;
3771 
3772                 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3773         }
3774         raw_spin_unlock(&cfs_b->lock);
3775 
3776         return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3777 }
3778 
3779 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3780 {
3781         raw_spin_lock_init(&cfs_b->lock);
3782         cfs_b->runtime = 0;
3783         cfs_b->quota = RUNTIME_INF;
3784         cfs_b->period = ns_to_ktime(default_cfs_period());
3785 
3786         INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3787         hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3788         cfs_b->period_timer.function = sched_cfs_period_timer;
3789         hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3790         cfs_b->slack_timer.function = sched_cfs_slack_timer;
3791 }
3792 
3793 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3794 {
3795         cfs_rq->runtime_enabled = 0;
3796         INIT_LIST_HEAD(&cfs_rq->throttled_list);
3797 }
3798 
3799 /* requires cfs_b->lock, may release to reprogram timer */
3800 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force)
3801 {
3802         /*
3803          * The timer may be active because we're trying to set a new bandwidth
3804          * period or because we're racing with the tear-down path
3805          * (timer_active==0 becomes visible before the hrtimer call-back
3806          * terminates).  In either case we ensure that it's re-programmed
3807          */
3808         while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
3809                hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
3810                 /* bounce the lock to allow do_sched_cfs_period_timer to run */
3811                 raw_spin_unlock(&cfs_b->lock);
3812                 cpu_relax();
3813                 raw_spin_lock(&cfs_b->lock);
3814                 /* if someone else restarted the timer then we're done */
3815                 if (!force && cfs_b->timer_active)
3816                         return;
3817         }
3818 
3819         cfs_b->timer_active = 1;
3820         start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
3821 }
3822 
3823 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3824 {
3825         hrtimer_cancel(&cfs_b->period_timer);
3826         hrtimer_cancel(&cfs_b->slack_timer);
3827 }
3828 
3829 static void __maybe_unused update_runtime_enabled(struct rq *rq)
3830 {
3831         struct cfs_rq *cfs_rq;
3832 
3833         for_each_leaf_cfs_rq(rq, cfs_rq) {
3834                 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
3835 
3836                 raw_spin_lock(&cfs_b->lock);
3837                 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
3838                 raw_spin_unlock(&cfs_b->lock);
3839         }
3840 }
3841 
3842 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3843 {
3844         struct cfs_rq *cfs_rq;
3845 
3846         for_each_leaf_cfs_rq(rq, cfs_rq) {
3847                 if (!cfs_rq->runtime_enabled)
3848                         continue;
3849 
3850                 /*
3851                  * clock_task is not advancing so we just need to make sure
3852                  * there's some valid quota amount
3853                  */
3854                 cfs_rq->runtime_remaining = 1;
3855                 /*
3856                  * Offline rq is schedulable till cpu is completely disabled
3857                  * in take_cpu_down(), so we prevent new cfs throttling here.
3858                  */
3859                 cfs_rq->runtime_enabled = 0;
3860 
3861                 if (cfs_rq_throttled(cfs_rq))
3862                         unthrottle_cfs_rq(cfs_rq);
3863         }
3864 }
3865 
3866 #else /* CONFIG_CFS_BANDWIDTH */
3867 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3868 {
3869         return rq_clock_task(rq_of(cfs_rq));
3870 }
3871 
3872 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
3873 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
3874 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3875 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3876 
3877 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3878 {
3879         return 0;
3880 }
3881 
3882 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3883 {
3884         return 0;
3885 }
3886 
3887 static inline int throttled_lb_pair(struct task_group *tg,
3888                                     int src_cpu, int dest_cpu)
3889 {
3890         return 0;
3891 }
3892 
3893 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
3894 
3895 #ifdef CONFIG_FAIR_GROUP_SCHED
3896 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3897 #endif
3898 
3899 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3900 {
3901         return NULL;
3902 }
3903 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
3904 static inline void update_runtime_enabled(struct rq *rq) {}
3905 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
3906 
3907 #endif /* CONFIG_CFS_BANDWIDTH */
3908 
3909 /**************************************************
3910  * CFS operations on tasks:
3911  */
3912 
3913 #ifdef CONFIG_SCHED_HRTICK
3914 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
3915 {
3916         struct sched_entity *se = &p->se;
3917         struct cfs_rq *cfs_rq = cfs_rq_of(se);
3918 
3919         WARN_ON(task_rq(p) != rq);
3920 
3921         if (cfs_rq->nr_running > 1) {
3922                 u64 slice = sched_slice(cfs_rq, se);
3923                 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
3924                 s64 delta = slice - ran;
3925 
3926                 if (delta < 0) {
3927                         if (rq->curr == p)
3928                                 resched_curr(rq);
3929                         return;
3930                 }
3931                 hrtick_start(rq, delta);
3932         }
3933 }
3934 
3935 /*
3936  * called from enqueue/dequeue and updates the hrtick when the
3937  * current task is from our class and nr_running is low enough
3938  * to matter.
3939  */
3940 static void hrtick_update(struct rq *rq)
3941 {
3942         struct task_struct *curr = rq->curr;
3943 
3944         if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3945                 return;
3946 
3947         if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
3948                 hrtick_start_fair(rq, curr);
3949 }
3950 #else /* !CONFIG_SCHED_HRTICK */
3951 static inline void
3952 hrtick_start_fair(struct rq *rq, struct task_struct *p)
3953 {
3954 }
3955 
3956 static inline void hrtick_update(struct rq *rq)
3957 {
3958 }
3959 #endif
3960 
3961 /*
3962  * The enqueue_task method is called before nr_running is
3963  * increased. Here we update the fair scheduling stats and
3964  * then put the task into the rbtree:
3965  */
3966 static void
3967 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3968 {
3969         struct cfs_rq *cfs_rq;
3970         struct sched_entity *se = &p->se;
3971 
3972         for_each_sched_entity(se) {
3973                 if (se->on_rq)
3974                         break;
3975                 cfs_rq = cfs_rq_of(se);
3976                 enqueue_entity(cfs_rq, se, flags);
3977 
3978                 /*
3979                  * end evaluation on encountering a throttled cfs_rq
3980                  *
3981                  * note: in the case of encountering a throttled cfs_rq we will
3982                  * post the final h_nr_running increment below.
3983                 */
3984                 if (cfs_rq_throttled(cfs_rq))
3985                         break;
3986                 cfs_rq->h_nr_running++;
3987 
3988                 flags = ENQUEUE_WAKEUP;
3989         }
3990 
3991         for_each_sched_entity(se) {
3992                 cfs_rq = cfs_rq_of(se);
3993                 cfs_rq->h_nr_running++;
3994 
3995                 if (cfs_rq_throttled(cfs_rq))
3996                         break;
3997 
3998                 update_cfs_shares(cfs_rq);
3999                 update_entity_load_avg(se, 1);
4000         }
4001 
4002         if (!se) {
4003                 update_rq_runnable_avg(rq, rq->nr_running);
4004                 add_nr_running(rq, 1);
4005         }
4006         hrtick_update(rq);
4007 }
4008 
4009 static void set_next_buddy(struct sched_entity *se);
4010 
4011 /*
4012  * The dequeue_task method is called before nr_running is
4013  * decreased. We remove the task from the rbtree and
4014  * update the fair scheduling stats:
4015  */
4016 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4017 {
4018         struct cfs_rq *cfs_rq;
4019         struct sched_entity *se = &p->se;
4020         int task_sleep = flags & DEQUEUE_SLEEP;
4021 
4022         for_each_sched_entity(se) {
4023                 cfs_rq = cfs_rq_of(se);
4024                 dequeue_entity(cfs_rq, se, flags);
4025 
4026                 /*
4027                  * end evaluation on encountering a throttled cfs_rq
4028                  *
4029                  * note: in the case of encountering a throttled cfs_rq we will
4030                  * post the final h_nr_running decrement below.
4031                 */
4032                 if (cfs_rq_throttled(cfs_rq))
4033                         break;
4034                 cfs_rq->h_nr_running--;
4035 
4036                 /* Don't dequeue parent if it has other entities besides us */
4037                 if (cfs_rq->load.weight) {
4038                         /*
4039                          * Bias pick_next to pick a task from this cfs_rq, as
4040                          * p is sleeping when it is within its sched_slice.
4041                          */
4042                         if (task_sleep && parent_entity(se))
4043                                 set_next_buddy(parent_entity(se));
4044 
4045                         /* avoid re-evaluating load for this entity */
4046                         se = parent_entity(se);
4047                         break;
4048                 }
4049                 flags |= DEQUEUE_SLEEP;
4050         }
4051 
4052         for_each_sched_entity(se) {
4053                 cfs_rq = cfs_rq_of(se);
4054                 cfs_rq->h_nr_running--;
4055 
4056                 if (cfs_rq_throttled(cfs_rq))
4057                         break;
4058 
4059                 update_cfs_shares(cfs_rq);
4060                 update_entity_load_avg(se, 1);
4061         }
4062 
4063         if (!se) {
4064                 sub_nr_running(rq, 1);
4065                 update_rq_runnable_avg(rq, 1);
4066         }
4067         hrtick_update(rq);
4068 }
4069 
4070 #ifdef CONFIG_SMP
4071 /* Used instead of source_load when we know the type == 0 */
4072 static unsigned long weighted_cpuload(const int cpu)
4073 {
4074         return cpu_rq(cpu)->cfs.runnable_load_avg;
4075 }
4076 
4077 /*
4078  * Return a low guess at the load of a migration-source cpu weighted
4079  * according to the scheduling class and "nice" value.
4080  *
4081  * We want to under-estimate the load of migration sources, to
4082  * balance conservatively.
4083  */
4084 static unsigned long source_load(int cpu, int type)
4085 {
4086         struct rq *rq = cpu_rq(cpu);
4087         unsigned long total = weighted_cpuload(cpu);
4088 
4089         if (type == 0 || !sched_feat(LB_BIAS))
4090                 return total;
4091 
4092         return min(rq->cpu_load[type-1], total);
4093 }
4094 
4095 /*
4096  * Return a high guess at the load of a migration-target cpu weighted
4097  * according to the scheduling class and "nice" value.
4098  */
4099 static unsigned long target_load(int cpu, int type)
4100 {
4101         struct rq *rq = cpu_rq(cpu);
4102         unsigned long total = weighted_cpuload(cpu);
4103 
4104         if (type == 0 || !sched_feat(LB_BIAS))
4105                 return total;
4106 
4107         return max(rq->cpu_load[type-1], total);
4108 }
4109 
4110 static unsigned long capacity_of(int cpu)
4111 {
4112         return cpu_rq(cpu)->cpu_capacity;
4113 }
4114 
4115 static unsigned long cpu_avg_load_per_task(int cpu)
4116 {
4117         struct rq *rq = cpu_rq(cpu);
4118         unsigned long nr_running = ACCESS_ONCE(rq->cfs.h_nr_running);
4119         unsigned long load_avg = rq->cfs.runnable_load_avg;
4120 
4121         if (nr_running)
4122                 return load_avg / nr_running;
4123 
4124         return 0;
4125 }
4126 
4127 static void record_wakee(struct task_struct *p)
4128 {
4129         /*
4130          * Rough decay (wiping) for cost saving, don't worry
4131          * about the boundary, really active task won't care
4132          * about the loss.
4133          */
4134         if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4135                 current->wakee_flips >>= 1;
4136                 current->wakee_flip_decay_ts = jiffies;
4137         }
4138 
4139         if (current->last_wakee != p) {
4140                 current->last_wakee = p;
4141                 current->wakee_flips++;
4142         }
4143 }
4144 
4145 static void task_waking_fair(struct task_struct *p)
4146 {
4147         struct sched_entity *se = &p->se;
4148         struct cfs_rq *cfs_rq = cfs_rq_of(se);
4149         u64 min_vruntime;
4150 
4151 #ifndef CONFIG_64BIT
4152         u64 min_vruntime_copy;
4153 
4154         do {
4155                 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4156                 smp_rmb();
4157                 min_vruntime = cfs_rq->min_vruntime;
4158         } while (min_vruntime != min_vruntime_copy);
4159 #else
4160         min_vruntime = cfs_rq->min_vruntime;
4161 #endif
4162 
4163         se->vruntime -= min_vruntime;
4164         record_wakee(p);
4165 }
4166 
4167 #ifdef CONFIG_FAIR_GROUP_SCHED
4168 /*
4169  * effective_load() calculates the load change as seen from the root_task_group
4170  *
4171  * Adding load to a group doesn't make a group heavier, but can cause movement
4172  * of group shares between cpus. Assuming the shares were perfectly aligned one
4173  * can calculate the shift in shares.
4174  *
4175  * Calculate the effective load difference if @wl is added (subtracted) to @tg
4176  * on this @cpu and results in a total addition (subtraction) of @wg to the
4177  * total group weight.
4178  *
4179  * Given a runqueue weight distribution (rw_i) we can compute a shares
4180  * distribution (s_i) using:
4181  *
4182  *   s_i = rw_i / \Sum rw_j                                             (1)
4183  *
4184  * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4185  * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4186  * shares distribution (s_i):
4187  *
4188  *   rw_i = {   2,   4,   1,   0 }
4189  *   s_i  = { 2/7, 4/7, 1/7,   0 }
4190  *
4191  * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4192  * task used to run on and the CPU the waker is running on), we need to
4193  * compute the effect of waking a task on either CPU and, in case of a sync
4194  * wakeup, compute the effect of the current task going to sleep.
4195  *
4196  * So for a change of @wl to the local @cpu with an overall group weight change
4197  * of @wl we can compute the new shares distribution (s'_i) using:
4198  *
4199  *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)                            (2)
4200  *
4201  * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4202  * differences in waking a task to CPU 0. The additional task changes the
4203  * weight and shares distributions like:
4204  *
4205  *   rw'_i = {   3,   4,   1,   0 }
4206  *   s'_i  = { 3/8, 4/8, 1/8,   0 }
4207  *
4208  * We can then compute the difference in effective weight by using:
4209  *
4210  *   dw_i = S * (s'_i - s_i)                                            (3)
4211  *
4212  * Where 'S' is the group weight as seen by its parent.
4213  *
4214  * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4215  * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4216  * 4/7) times the weight of the group.
4217  */
4218 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4219 {
4220         struct sched_entity *se = tg->se[cpu];
4221 
4222         if (!tg->parent)        /* the trivial, non-cgroup case */
4223                 return wl;
4224 
4225         for_each_sched_entity(se) {
4226                 long w, W;
4227 
4228                 tg = se->my_q->tg;
4229 
4230                 /*
4231                  * W = @wg + \Sum rw_j
4232                  */
4233                 W = wg + calc_tg_weight(tg, se->my_q);
4234 
4235                 /*
4236                  * w = rw_i + @wl
4237                  */
4238                 w = se->my_q->load.weight + wl;
4239 
4240                 /*
4241                  * wl = S * s'_i; see (2)
4242                  */
4243                 if (W > 0 && w < W)
4244                         wl = (w * tg->shares) / W;
4245                 else
4246                         wl = tg->shares;
4247 
4248                 /*
4249                  * Per the above, wl is the new se->load.weight value; since
4250                  * those are clipped to [MIN_SHARES, ...) do so now. See
4251                  * calc_cfs_shares().
4252                  */
4253                 if (wl < MIN_SHARES)
4254                         wl = MIN_SHARES;
4255 
4256                 /*
4257                  * wl = dw_i = S * (s'_i - s_i); see (3)
4258                  */
4259                 wl -= se->load.weight;
4260 
4261                 /*
4262                  * Recursively apply this logic to all parent groups to compute
4263                  * the final effective load change on the root group. Since
4264                  * only the @tg group gets extra weight, all parent groups can
4265                  * only redistribute existing shares. @wl is the shift in shares
4266                  * resulting from this level per the above.
4267                  */
4268                 wg = 0;
4269         }
4270 
4271         return wl;
4272 }
4273 #else
4274 
4275 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4276 {
4277         return wl;
4278 }
4279 
4280 #endif
4281 
4282 static int wake_wide(struct task_struct *p)
4283 {
4284         int factor = this_cpu_read(sd_llc_size);
4285 
4286         /*
4287          * Yeah, it's the switching-frequency, could means many wakee or
4288          * rapidly switch, use factor here will just help to automatically
4289          * adjust the loose-degree, so bigger node will lead to more pull.
4290          */
4291         if (p->wakee_flips > factor) {
4292                 /*
4293                  * wakee is somewhat hot, it needs certain amount of cpu
4294                  * resource, so if waker is far more hot, prefer to leave
4295                  * it alone.
4296                  */
4297                 if (current->wakee_flips > (factor * p->wakee_flips))
4298                         return 1;
4299         }
4300 
4301         return 0;
4302 }
4303 
4304 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4305 {
4306         s64 this_load, load;
4307         s64 this_eff_load, prev_eff_load;
4308         int idx, this_cpu, prev_cpu;
4309         struct task_group *tg;
4310         unsigned long weight;
4311         int balanced;
4312 
4313         /*
4314          * If we wake multiple tasks be careful to not bounce
4315          * ourselves around too much.
4316          */
4317         if (wake_wide(p))
4318                 return 0;
4319 
4320         idx       = sd->wake_idx;
4321         this_cpu  = smp_processor_id();
4322         prev_cpu  = task_cpu(p);
4323         load      = source_load(prev_cpu, idx);
4324         this_load = target_load(this_cpu, idx);
4325 
4326         /*
4327          * If sync wakeup then subtract the (maximum possible)
4328          * effect of the currently running task from the load
4329          * of the current CPU:
4330          */
4331         if (sync) {
4332                 tg = task_group(current);
4333                 weight = current->se.load.weight;
4334 
4335                 this_load += effective_load(tg, this_cpu, -weight, -weight);
4336                 load += effective_load(tg, prev_cpu, 0, -weight);
4337         }
4338 
4339         tg = task_group(p);
4340         weight = p->se.load.weight;
4341 
4342         /*
4343          * In low-load situations, where prev_cpu is idle and this_cpu is idle
4344          * due to the sync cause above having dropped this_load to 0, we'll
4345          * always have an imbalance, but there's really nothing you can do
4346          * about that, so that's good too.
4347          *
4348          * Otherwise check if either cpus are near enough in load to allow this
4349          * task to be woken on this_cpu.
4350          */
4351         this_eff_load = 100;
4352         this_eff_load *= capacity_of(prev_cpu);
4353 
4354         prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4355         prev_eff_load *= capacity_of(this_cpu);
4356 
4357         if (this_load > 0) {
4358                 this_eff_load *= this_load +
4359                         effective_load(tg, this_cpu, weight, weight);
4360 
4361                 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4362         }
4363 
4364         balanced = this_eff_load <= prev_eff_load;
4365 
4366         schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4367 
4368         if (!balanced)
4369                 return 0;
4370 
4371         schedstat_inc(sd, ttwu_move_affine);
4372         schedstat_inc(p, se.statistics.nr_wakeups_affine);
4373 
4374         return 1;
4375 }
4376 
4377 /*
4378  * find_idlest_group finds and returns the least busy CPU group within the
4379  * domain.
4380  */
4381 static struct sched_group *
4382 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4383                   int this_cpu, int sd_flag)
4384 {
4385         struct sched_group *idlest = NULL, *group = sd->groups;
4386         unsigned long min_load = ULONG_MAX, this_load = 0;
4387         int load_idx = sd->forkexec_idx;
4388         int imbalance = 100 + (sd->imbalance_pct-100)/2;
4389 
4390         if (sd_flag & SD_BALANCE_WAKE)
4391                 load_idx = sd->wake_idx;
4392 
4393         do {
4394                 unsigned long load, avg_load;
4395                 int local_group;
4396                 int i;
4397 
4398                 /* Skip over this group if it has no CPUs allowed */
4399                 if (!cpumask_intersects(sched_group_cpus(group),
4400                                         tsk_cpus_allowed(p)))
4401                         continue;
4402 
4403                 local_group = cpumask_test_cpu(this_cpu,
4404                                                sched_group_cpus(group));
4405 
4406                 /* Tally up the load of all CPUs in the group */
4407                 avg_load = 0;
4408 
4409                 for_each_cpu(i, sched_group_cpus(group)) {
4410                         /* Bias balancing toward cpus of our domain */
4411                         if (local_group)
4412                                 load = source_load(i, load_idx);
4413                         else
4414                                 load = target_load(i, load_idx);
4415 
4416                         avg_load += load;
4417                 }
4418 
4419                 /* Adjust by relative CPU capacity of the group */
4420                 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4421 
4422                 if (local_group) {
4423                         this_load = avg_load;
4424                 } else if (avg_load < min_load) {
4425                         min_load = avg_load;
4426                         idlest = group;
4427                 }
4428         } while (group = group->next, group != sd->groups);
4429 
4430         if (!idlest || 100*this_load < imbalance*min_load)
4431                 return NULL;
4432         return idlest;
4433 }
4434 
4435 /*
4436  * find_idlest_cpu - find the idlest cpu among the cpus in group.
4437  */
4438 static int
4439 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4440 {
4441         unsigned long load, min_load = ULONG_MAX;
4442         unsigned int min_exit_latency = UINT_MAX;
4443         u64 latest_idle_timestamp = 0;
4444         int least_loaded_cpu = this_cpu;
4445         int shallowest_idle_cpu = -1;
4446         int i;
4447 
4448         /* Traverse only the allowed CPUs */
4449         for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4450                 if (idle_cpu(i)) {
4451                         struct rq *rq = cpu_rq(i);
4452                         struct cpuidle_state *idle = idle_get_state(rq);
4453                         if (idle && idle->exit_latency < min_exit_latency) {
4454                                 /*
4455                                  * We give priority to a CPU whose idle state
4456                                  * has the smallest exit latency irrespective
4457                                  * of any idle timestamp.
4458                                  */
4459                                 min_exit_latency = idle->exit_latency;
4460                                 latest_idle_timestamp = rq->idle_stamp;
4461                                 shallowest_idle_cpu = i;
4462                         } else if ((!idle || idle->exit_latency == min_exit_latency) &&
4463                                    rq->idle_stamp > latest_idle_timestamp) {
4464                                 /*
4465                                  * If equal or no active idle state, then
4466                                  * the most recently idled CPU might have
4467                                  * a warmer cache.
4468                                  */
4469                                 latest_idle_timestamp = rq->idle_stamp;
4470                                 shallowest_idle_cpu = i;
4471                         }
4472                 } else {
4473                         load = weighted_cpuload(i);
4474                         if (load < min_load || (load == min_load && i == this_cpu)) {
4475                                 min_load = load;
4476                                 least_loaded_cpu = i;
4477                         }
4478                 }
4479         }
4480 
4481         return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4482 }
4483 
4484 /*
4485  * Try and locate an idle CPU in the sched_domain.
4486  */
4487 static int select_idle_sibling(struct task_struct *p, int target)
4488 {
4489         struct sched_domain *sd;
4490         struct sched_group *sg;
4491         int i = task_cpu(p);
4492 
4493         if (idle_cpu(target))
4494                 return target;
4495 
4496         /*
4497          * If the prevous cpu is cache affine and idle, don't be stupid.
4498          */
4499         if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4500                 return i;
4501 
4502         /*
4503          * Otherwise, iterate the domains and find an elegible idle cpu.
4504          */
4505         sd = rcu_dereference(per_cpu(sd_llc, target));
4506         for_each_lower_domain(sd) {
4507                 sg = sd->groups;
4508                 do {
4509                         if (!cpumask_intersects(sched_group_cpus(sg),
4510                                                 tsk_cpus_allowed(p)))
4511                                 goto next;
4512 
4513                         for_each_cpu(i, sched_group_cpus(sg)) {
4514                                 if (i == target || !idle_cpu(i))
4515                                         goto next;
4516                         }
4517 
4518                         target = cpumask_first_and(sched_group_cpus(sg),
4519                                         tsk_cpus_allowed(p));
4520                         goto done;
4521 next:
4522                         sg = sg->next;
4523                 } while (sg != sd->groups);
4524         }
4525 done:
4526         return target;
4527 }
4528 
4529 /*
4530  * select_task_rq_fair: Select target runqueue for the waking task in domains
4531  * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4532  * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4533  *
4534  * Balances load by selecting the idlest cpu in the idlest group, or under
4535  * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4536  *
4537  * Returns the target cpu number.
4538  *
4539  * preempt must be disabled.
4540  */
4541 static int
4542 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4543 {
4544         struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4545         int cpu = smp_processor_id();
4546         int new_cpu = cpu;
4547         int want_affine = 0;
4548         int sync = wake_flags & WF_SYNC;
4549 
4550         if (p->nr_cpus_allowed == 1)
4551                 return prev_cpu;
4552 
4553         if (sd_flag & SD_BALANCE_WAKE)
4554                 want_affine = cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4555 
4556         rcu_read_lock();
4557         for_each_domain(cpu, tmp) {
4558                 if (!(tmp->flags & SD_LOAD_BALANCE))
4559                         continue;
4560 
4561                 /*
4562                  * If both cpu and prev_cpu are part of this domain,
4563                  * cpu is a valid SD_WAKE_AFFINE target.
4564                  */
4565                 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4566                     cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4567                         affine_sd = tmp;
4568                         break;
4569                 }
4570 
4571                 if (tmp->flags & sd_flag)
4572                         sd = tmp;
4573         }
4574 
4575         if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4576                 prev_cpu = cpu;
4577 
4578         if (sd_flag & SD_BALANCE_WAKE) {
4579                 new_cpu = select_idle_sibling(p, prev_cpu);
4580                 goto unlock;
4581         }
4582 
4583         while (sd) {
4584                 struct sched_group *group;
4585                 int weight;
4586 
4587                 if (!(sd->flags & sd_flag)) {
4588                         sd = sd->child;
4589                         continue;
4590                 }
4591 
4592                 group = find_idlest_group(sd, p, cpu, sd_flag);
4593                 if (!group) {
4594                         sd = sd->child;
4595                         continue;
4596                 }
4597 
4598                 new_cpu = find_idlest_cpu(group, p, cpu);
4599                 if (new_cpu == -1 || new_cpu == cpu) {
4600                         /* Now try balancing at a lower domain level of cpu */
4601                         sd = sd->child;
4602                         continue;
4603                 }
4604 
4605                 /* Now try balancing at a lower domain level of new_cpu */
4606                 cpu = new_cpu;
4607                 weight = sd->span_weight;
4608                 sd = NULL;
4609                 for_each_domain(cpu, tmp) {
4610                         if (weight <= tmp->span_weight)
4611                                 break;
4612                         if (tmp->flags & sd_flag)
4613                                 sd = tmp;
4614                 }
4615                 /* while loop will break here if sd == NULL */
4616         }
4617 unlock:
4618         rcu_read_unlock();
4619 
4620         return new_cpu;
4621 }
4622 
4623 /*
4624  * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4625  * cfs_rq_of(p) references at time of call are still valid and identify the
4626  * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
4627  * other assumptions, including the state of rq->lock, should be made.
4628  */
4629 static void
4630 migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4631 {
4632         struct sched_entity *se = &p->se;
4633         struct cfs_rq *cfs_rq = cfs_rq_of(se);
4634 
4635         /*
4636          * Load tracking: accumulate removed load so that it can be processed
4637          * when we next update owning cfs_rq under rq->lock.  Tasks contribute
4638          * to blocked load iff they have a positive decay-count.  It can never
4639          * be negative here since on-rq tasks have decay-count == 0.
4640          */
4641         if (se->avg.decay_count) {
4642                 se->avg.decay_count = -__synchronize_entity_decay(se);
4643                 atomic_long_add(se->avg.load_avg_contrib,
4644                                                 &cfs_rq->removed_load);
4645         }
4646 
4647         /* We have migrated, no longer consider this task hot */
4648         se->exec_start = 0;
4649 }
4650 #endif /* CONFIG_SMP */
4651 
4652 static unsigned long
4653 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4654 {
4655         unsigned long gran = sysctl_sched_wakeup_granularity;
4656 
4657         /*
4658          * Since its curr running now, convert the gran from real-time
4659          * to virtual-time in his units.
4660          *
4661          * By using 'se' instead of 'curr' we penalize light tasks, so
4662          * they get preempted easier. That is, if 'se' < 'curr' then
4663          * the resulting gran will be larger, therefore penalizing the
4664          * lighter, if otoh 'se' > 'curr' then the resulting gran will
4665          * be smaller, again penalizing the lighter task.
4666          *
4667          * This is especially important for buddies when the leftmost
4668          * task is higher priority than the buddy.
4669          */
4670         return calc_delta_fair(gran, se);
4671 }
4672 
4673 /*
4674  * Should 'se' preempt 'curr'.
4675  *
4676  *             |s1
4677  *        |s2
4678  *   |s3
4679  *         g
4680  *      |<--->|c
4681  *
4682  *  w(c, s1) = -1
4683  *  w(c, s2) =  0
4684  *  w(c, s3) =  1
4685  *
4686  */
4687 static int
4688 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
4689 {
4690         s64 gran, vdiff = curr->vruntime - se->vruntime;
4691 
4692         if (vdiff <= 0)
4693                 return -1;
4694 
4695         gran = wakeup_gran(curr, se);
4696         if (vdiff > gran)
4697                 return 1;
4698 
4699         return 0;
4700 }
4701 
4702 static void set_last_buddy(struct sched_entity *se)
4703 {
4704         if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
4705                 return;
4706 
4707         for_each_sched_entity(se)
4708                 cfs_rq_of(se)->last = se;
4709 }
4710 
4711 static void set_next_buddy(struct sched_entity *se)
4712 {
4713         if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
4714                 return;
4715 
4716         for_each_sched_entity(se)
4717                 cfs_rq_of(se)->next = se;
4718 }
4719 
4720 static void set_skip_buddy(struct sched_entity *se)
4721 {
4722         for_each_sched_entity(se)
4723                 cfs_rq_of(se)->skip = se;
4724 }
4725 
4726 /*
4727  * Preempt the current task with a newly woken task if needed:
4728  */
4729 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4730 {
4731         struct task_struct *curr = rq->curr;
4732         struct sched_entity *se = &curr->se, *pse = &p->se;
4733         struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4734         int scale = cfs_rq->nr_running >= sched_nr_latency;
4735         int next_buddy_marked = 0;
4736 
4737         if (unlikely(se == pse))
4738                 return;
4739 
4740         /*
4741          * This is possible from callers such as attach_tasks(), in which we
4742          * unconditionally check_prempt_curr() after an enqueue (which may have
4743          * lead to a throttle).  This both saves work and prevents false
4744          * next-buddy nomination below.
4745          */
4746         if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
4747                 return;
4748 
4749         if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
4750                 set_next_buddy(pse);
4751                 next_buddy_marked = 1;
4752         }
4753 
4754         /*
4755          * We can come here with TIF_NEED_RESCHED already set from new task
4756          * wake up path.
4757          *
4758          * Note: this also catches the edge-case of curr being in a throttled
4759          * group (e.g. via set_curr_task), since update_curr() (in the
4760          * enqueue of curr) will have resulted in resched being set.  This
4761          * prevents us from potentially nominating it as a false LAST_BUDDY
4762          * below.
4763          */
4764         if (test_tsk_need_resched(curr))
4765                 return;
4766 
4767         /* Idle tasks are by definition preempted by non-idle tasks. */
4768         if (unlikely(curr->policy == SCHED_IDLE) &&
4769             likely(p->policy != SCHED_IDLE))
4770                 goto preempt;
4771 
4772         /*
4773          * Batch and idle tasks do not preempt non-idle tasks (their preemption
4774          * is driven by the tick):
4775          */
4776         if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
4777                 return;
4778 
4779         find_matching_se(&se, &pse);
4780         update_curr(cfs_rq_of(se));
4781         BUG_ON(!pse);
4782         if (wakeup_preempt_entity(se, pse) == 1) {
4783                 /*
4784                  * Bias pick_next to pick the sched entity that is
4785                  * triggering this preemption.
4786                  */
4787                 if (!next_buddy_marked)
4788                         set_next_buddy(pse);
4789                 goto preempt;
4790         }
4791 
4792         return;
4793 
4794 preempt:
4795         resched_curr(rq);
4796         /*
4797          * Only set the backward buddy when the current task is still
4798          * on the rq. This can happen when a wakeup gets interleaved
4799          * with schedule on the ->pre_schedule() or idle_balance()
4800          * point, either of which can * drop the rq lock.
4801          *
4802          * Also, during early boot the idle thread is in the fair class,
4803          * for obvious reasons its a bad idea to schedule back to it.
4804          */
4805         if (unlikely(!se->on_rq || curr == rq->idle))
4806                 return;
4807 
4808         if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
4809                 set_last_buddy(se);
4810 }
4811 
4812 static struct task_struct *
4813 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
4814 {
4815         struct cfs_rq *cfs_rq = &rq->cfs;
4816         struct sched_entity *se;
4817         struct task_struct *p;
4818         int new_tasks;
4819 
4820 again:
4821 #ifdef CONFIG_FAIR_GROUP_SCHED
4822         if (!cfs_rq->nr_running)
4823                 goto idle;
4824 
4825         if (prev->sched_class != &fair_sched_class)
4826                 goto simple;
4827 
4828         /*
4829          * Because of the set_next_buddy() in dequeue_task_fair() it is rather
4830          * likely that a next task is from the same cgroup as the current.
4831          *
4832          * Therefore attempt to avoid putting and setting the entire cgroup
4833          * hierarchy, only change the part that actually changes.
4834          */
4835 
4836         do {
4837                 struct sched_entity *curr = cfs_rq->curr;
4838 
4839                 /*
4840                  * Since we got here without doing put_prev_entity() we also
4841                  * have to consider cfs_rq->curr. If it is still a runnable
4842                  * entity, update_curr() will update its vruntime, otherwise
4843                  * forget we've ever seen it.
4844                  */
4845                 if (curr && curr->on_rq)
4846                         update_curr(cfs_rq);
4847                 else
4848                         curr = NULL;
4849 
4850                 /*
4851                  * This call to check_cfs_rq_runtime() will do the throttle and
4852                  * dequeue its entity in the parent(s). Therefore the 'simple'
4853                  * nr_running test will indeed be correct.
4854                  */
4855                 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
4856                         goto simple;
4857 
4858                 se = pick_next_entity(cfs_rq, curr);
4859                 cfs_rq = group_cfs_rq(se);
4860         } while (cfs_rq);
4861 
4862         p = task_of(se);
4863 
4864         /*
4865          * Since we haven't yet done put_prev_entity and if the selected task
4866          * is a different task than we started out with, try and touch the
4867          * least amount of cfs_rqs.
4868          */
4869         if (prev != p) {
4870                 struct sched_entity *pse = &prev->se;
4871 
4872                 while (!(cfs_rq = is_same_group(se, pse))) {
4873                         int se_depth = se->depth;
4874                         int pse_depth = pse->depth;
4875 
4876                         if (se_depth <= pse_depth) {
4877                                 put_prev_entity(cfs_rq_of(pse), pse);
4878                                 pse = parent_entity(pse);
4879                         }
4880                         if (se_depth >= pse_depth) {
4881                                 set_next_entity(cfs_rq_of(se), se);
4882                                 se = parent_entity(se);
4883                         }
4884                 }
4885 
4886                 put_prev_entity(cfs_rq, pse);
4887                 set_next_entity(cfs_rq, se);
4888         }
4889 
4890         if (hrtick_enabled(rq))
4891                 hrtick_start_fair(rq, p);
4892 
4893         return p;
4894 simple:
4895         cfs_rq = &rq->cfs;
4896 #endif
4897 
4898         if (!cfs_rq->nr_running)
4899                 goto idle;
4900 
4901         put_prev_task(rq, prev);
4902 
4903         do {
4904                 se = pick_next_entity(cfs_rq, NULL);
4905                 set_next_entity(cfs_rq, se);
4906                 cfs_rq = group_cfs_rq(se);
4907         } while (cfs_rq);
4908 
4909         p = task_of(se);
4910 
4911         if (hrtick_enabled(rq))
4912                 hrtick_start_fair(rq, p);
4913 
4914         return p;
4915 
4916 idle:
4917         new_tasks = idle_balance(rq);
4918         /*
4919          * Because idle_balance() releases (and re-acquires) rq->lock, it is
4920          * possible for any higher priority task to appear. In that case we
4921          * must re-start the pick_next_entity() loop.
4922          */
4923         if (new_tasks < 0)
4924                 return RETRY_TASK;
4925 
4926         if (new_tasks > 0)
4927                 goto again;
4928 
4929         return NULL;
4930 }
4931 
4932 /*
4933  * Account for a descheduled task:
4934  */
4935 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
4936 {
4937         struct sched_entity *se = &prev->se;
4938         struct cfs_rq *cfs_rq;
4939 
4940         for_each_sched_entity(se) {
4941                 cfs_rq = cfs_rq_of(se);
4942                 put_prev_entity(cfs_rq, se);
4943         }
4944 }
4945 
4946 /*
4947  * sched_yield() is very simple
4948  *
4949  * The magic of dealing with the ->skip buddy is in pick_next_entity.
4950  */
4951 static void yield_task_fair(struct rq *rq)
4952 {
4953         struct task_struct *curr = rq->curr;
4954         struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4955         struct sched_entity *se = &curr->se;
4956 
4957         /*
4958          * Are we the only task in the tree?
4959          */
4960         if (unlikely(rq->nr_running == 1))
4961                 return;
4962 
4963         clear_buddies(cfs_rq, se);
4964 
4965         if (curr->policy != SCHED_BATCH) {
4966                 update_rq_clock(rq);
4967                 /*
4968                  * Update run-time statistics of the 'current'.
4969                  */
4970                 update_curr(cfs_rq);
4971                 /*
4972                  * Tell update_rq_clock() that we've just updated,
4973                  * so we don't do microscopic update in schedule()
4974                  * and double the fastpath cost.
4975                  */
4976                  rq->skip_clock_update = 1;
4977         }
4978 
4979         set_skip_buddy(se);
4980 }
4981 
4982 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
4983 {
4984         struct sched_entity *se = &p->se;
4985 
4986         /* throttled hierarchies are not runnable */
4987         if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
4988                 return false;
4989 
4990         /* Tell the scheduler that we'd really like pse to run next. */
4991         set_next_buddy(se);
4992 
4993         yield_task_fair(rq);
4994 
4995         return true;
4996 }
4997 
4998 #ifdef CONFIG_SMP
4999 /**************************************************
5000  * Fair scheduling class load-balancing methods.
5001  *
5002  * BASICS
5003  *
5004  * The purpose of load-balancing is to achieve the same basic fairness the
5005  * per-cpu scheduler provides, namely provide a proportional amount of compute
5006  * time to each task. This is expressed in the following equation:
5007  *
5008  *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
5009  *
5010  * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5011  * W_i,0 is defined as:
5012  *
5013  *   W_i,0 = \Sum_j w_i,j                                             (2)
5014  *
5015  * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5016  * is derived from the nice value as per prio_to_weight[].
5017  *
5018  * The weight average is an exponential decay average of the instantaneous
5019  * weight:
5020  *
5021  *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
5022  *
5023  * C_i is the compute capacity of cpu i, typically it is the
5024  * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5025  * can also include other factors [XXX].
5026  *
5027  * To achieve this balance we define a measure of imbalance which follows
5028  * directly from (1):
5029  *
5030  *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
5031  *
5032  * We them move tasks around to minimize the imbalance. In the continuous
5033  * function space it is obvious this converges, in the discrete case we get
5034  * a few fun cases generally called infeasible weight scenarios.
5035  *
5036  * [XXX expand on:
5037  *     - infeasible weights;
5038  *     - local vs global optima in the discrete case. ]
5039  *
5040  *
5041  * SCHED DOMAINS
5042  *
5043  * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5044  * for all i,j solution, we create a tree of cpus that follows the hardware
5045  * topology where each level pairs two lower groups (or better). This results
5046  * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5047  * tree to only the first of the previous level and we decrease the frequency
5048  * of load-balance at each level inv. proportional to the number of cpus in
5049  * the groups.
5050  *
5051  * This yields:
5052  *
5053  *     log_2 n     1     n
5054  *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
5055  *     i = 0      2^i   2^i
5056  *                               `- size of each group
5057  *         |         |     `- number of cpus doing load-balance
5058  *         |         `- freq
5059  *         `- sum over all levels
5060  *
5061  * Coupled with a limit on how many tasks we can migrate every balance pass,
5062  * this makes (5) the runtime complexity of the balancer.
5063  *
5064  * An important property here is that each CPU is still (indirectly) connected
5065  * to every other cpu in at most O(log n) steps:
5066  *
5067  * The adjacency matrix of the resulting graph is given by:
5068  *
5069  *             log_2 n     
5070  *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
5071  *             k = 0
5072  *
5073  * And you'll find that:
5074  *
5075  *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
5076  *
5077  * Showing there's indeed a path between every cpu in at most O(log n) steps.
5078  * The task movement gives a factor of O(m), giving a convergence complexity
5079  * of:
5080  *
5081  *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
5082  *
5083  *
5084  * WORK CONSERVING
5085  *
5086  * In order to avoid CPUs going idle while there's still work to do, new idle
5087  * balancing is more aggressive and has the newly idle cpu iterate up the domain
5088  * tree itself instead of relying on other CPUs to bring it work.
5089  *
5090  * This adds some complexity to both (5) and (8) but it reduces the total idle
5091  * time.
5092  *
5093  * [XXX more?]
5094  *
5095  *
5096  * CGROUPS
5097  *
5098  * Cgroups make a horror show out of (2), instead of a simple sum we get:
5099  *
5100  *                                s_k,i
5101  *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
5102  *                                 S_k
5103  *
5104  * Where
5105  *
5106  *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
5107  *
5108  * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5109  *
5110  * The big problem is S_k, its a global sum needed to compute a local (W_i)
5111  * property.
5112  *
5113  * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5114  *      rewrite all of this once again.]
5115  */ 
5116 
5117 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5118 
5119 enum fbq_type { regular, remote, all };
5120 
5121 #define LBF_ALL_PINNED  0x01
5122 #define LBF_NEED_BREAK  0x02
5123 #define LBF_DST_PINNED  0x04
5124 #define LBF_SOME_PINNED 0x08
5125 
5126 struct lb_env {
5127         struct sched_domain     *sd;
5128 
5129         struct rq               *src_rq;
5130         int                     src_cpu;
5131 
5132         int                     dst_cpu;
5133         struct rq               *dst_rq;
5134 
5135         struct cpumask          *dst_grpmask;
5136         int                     new_dst_cpu;
5137         enum cpu_idle_type      idle;
5138         long                    imbalance;
5139         /* The set of CPUs under consideration for load-balancing */
5140         struct cpumask          *cpus;
5141 
5142         unsigned int            flags;
5143 
5144         unsigned int            loop;
5145         unsigned int            loop_break;
5146         unsigned int            loop_max;
5147 
5148         enum fbq_type           fbq_type;
5149         struct list_head        tasks;
5150 };
5151 
5152 /*
5153  * Is this task likely cache-hot:
5154  */
5155 static int task_hot(struct task_struct *p, struct lb_env *env)
5156 {
5157         s64 delta;
5158 
5159         lockdep_assert_held(&env->src_rq->lock);
5160 
5161         if (p->sched_class != &fair_sched_class)
5162                 return 0;
5163 
5164         if (unlikely(p->policy == SCHED_IDLE))
5165                 return 0;
5166 
5167         /*
5168          * Buddy candidates are cache hot:
5169          */
5170         if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5171                         (&p->se == cfs_rq_of(&p->se)->next ||
5172                          &p->se == cfs_rq_of(&p->se)->last))
5173                 return 1;
5174 
5175         if (sysctl_sched_migration_cost == -1)
5176                 return 1;
5177         if (sysctl_sched_migration_cost == 0)
5178                 return 0;
5179 
5180         delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5181 
5182         return delta < (s64)sysctl_sched_migration_cost;
5183 }
5184 
5185 #ifdef CONFIG_NUMA_BALANCING
5186 /* Returns true if the destination node has incurred more faults */
5187 static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
5188 {
5189         struct numa_group *numa_group = rcu_dereference(p->numa_group);
5190         int src_nid, dst_nid;
5191 
5192         if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults_memory ||
5193             !(env->sd->flags & SD_NUMA)) {
5194                 return false;
5195         }
5196 
5197         src_nid = cpu_to_node(env->src_cpu);
5198         dst_nid = cpu_to_node(env->dst_cpu);
5199 
5200         if (src_nid == dst_nid)
5201                 return false;
5202 
5203         if (numa_group) {
5204                 /* Task is already in the group's interleave set. */
5205                 if (node_isset(src_nid, numa_group->active_nodes))
5206                         return false;
5207 
5208                 /* Task is moving into the group's interleave set. */
5209                 if (node_isset(dst_nid, numa_group->active_nodes))
5210                         return true;
5211 
5212                 return group_faults(p, dst_nid) > group_faults(p, src_nid);
5213         }
5214 
5215         /* Encourage migration to the preferred node. */
5216         if (dst_nid == p->numa_preferred_nid)
5217                 return true;
5218 
5219         return task_faults(p, dst_nid) > task_faults(p, src_nid);
5220 }
5221 
5222 
5223 static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5224 {
5225         struct numa_group *numa_group = rcu_dereference(p->numa_group);
5226         int src_nid, dst_nid;
5227 
5228         if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
5229                 return false;
5230 
5231         if (!p->numa_faults_memory || !(env->sd->flags & SD_NUMA))
5232                 return false;
5233 
5234         src_nid = cpu_to_node(env->src_cpu);
5235         dst_nid = cpu_to_node(env->dst_cpu);
5236 
5237         if (src_nid == dst_nid)
5238                 return false;
5239 
5240         if (numa_group) {
5241                 /* Task is moving within/into the group's interleave set. */
5242                 if (node_isset(dst_nid, numa_group->active_nodes))
5243                         return false;
5244 
5245                 /* Task is moving out of the group's interleave set. */
5246                 if (node_isset(src_nid, numa_group->active_nodes))
5247                         return true;
5248 
5249                 return group_faults(p, dst_nid) < group_faults(p, src_nid);
5250         }
5251 
5252         /* Migrating away from the preferred node is always bad. */
5253         if (src_nid == p->numa_preferred_nid)
5254                 return true;
5255 
5256         return task_faults(p, dst_nid) < task_faults(p, src_nid);
5257 }
5258 
5259 #else
5260 static inline bool migrate_improves_locality(struct task_struct *p,
5261                                              struct lb_env *env)
5262 {
5263         return false;
5264 }
5265 
5266 static inline bool migrate_degrades_locality(struct task_struct *p,
5267                                              struct lb_env *env)
5268 {
5269         return false;
5270 }
5271 #endif
5272 
5273 /*
5274  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5275  */
5276 static
5277 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5278 {
5279         int tsk_cache_hot = 0;
5280 
5281         lockdep_assert_held(&env->src_rq->lock);
5282 
5283         /*
5284          * We do not migrate tasks that are:
5285          * 1) throttled_lb_pair, or
5286          * 2) cannot be migrated to this CPU due to cpus_allowed, or
5287          * 3) running (obviously), or
5288          * 4) are cache-hot on their current CPU.
5289          */
5290         if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5291                 return 0;
5292 
5293         if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5294                 int cpu;
5295 
5296                 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5297 
5298                 env->flags |= LBF_SOME_PINNED;
5299 
5300                 /*
5301                  * Remember if this task can be migrated to any other cpu in
5302                  * our sched_group. We may want to revisit it if we couldn't
5303                  * meet load balance goals by pulling other tasks on src_cpu.
5304                  *
5305                  * Also avoid computing new_dst_cpu if we have already computed
5306                  * one in current iteration.
5307                  */
5308                 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5309                         return 0;
5310 
5311                 /* Prevent to re-select dst_cpu via env's cpus */
5312                 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5313                         if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5314                                 env->flags |= LBF_DST_PINNED;
5315                                 env->new_dst_cpu = cpu;
5316                                 break;
5317                         }
5318                 }
5319 
5320                 return 0;
5321         }
5322 
5323         /* Record that we found atleast one task that could run on dst_cpu */
5324         env->flags &= ~LBF_ALL_PINNED;
5325 
5326         if (task_running(env->src_rq, p)) {
5327                 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5328                 return 0;
5329         }
5330 
5331         /*
5332          * Aggressive migration if:
5333          * 1) destination numa is preferred
5334          * 2) task is cache cold, or
5335          * 3) too many balance attempts have failed.
5336          */
5337         tsk_cache_hot = task_hot(p, env);
5338         if (!tsk_cache_hot)
5339                 tsk_cache_hot = migrate_degrades_locality(p, env);
5340 
5341         if (migrate_improves_locality(p, env) || !tsk_cache_hot ||
5342             env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5343                 if (tsk_cache_hot) {
5344                         schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5345                         schedstat_inc(p, se.statistics.nr_forced_migrations);
5346                 }
5347                 return 1;
5348         }
5349 
5350         schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5351         return 0;
5352 }
5353 
5354 /*
5355  * detach_task() -- detach the task for the migration specified in env
5356  */
5357 static void detach_task(struct task_struct *p, struct lb_env *env)
5358 {
5359         lockdep_assert_held(&env->src_rq->lock);
5360 
5361         deactivate_task(env->src_rq, p, 0);
5362         p->on_rq = TASK_ON_RQ_MIGRATING;
5363         set_task_cpu(p, env->dst_cpu);
5364 }
5365 
5366 /*
5367  * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5368  * part of active balancing operations within "domain".
5369  *
5370  * Returns a task if successful and NULL otherwise.
5371  */
5372 static struct task_struct *detach_one_task(struct lb_env *env)
5373 {
5374         struct task_struct *p, *n;
5375 
5376         lockdep_assert_held(&env->src_rq->lock);
5377 
5378         list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5379                 if (!can_migrate_task(p, env))
5380                         continue;
5381 
5382                 detach_task(p, env);
5383 
5384                 /*
5385                  * Right now, this is only the second place where
5386                  * lb_gained[env->idle] is updated (other is detach_tasks)
5387                  * so we can safely collect stats here rather than
5388                  * inside detach_tasks().
5389                  */
5390                 schedstat_inc(env->sd, lb_gained[env->idle]);
5391                 return p;
5392         }
5393         return NULL;
5394 }
5395 
5396 static const unsigned int sched_nr_migrate_break = 32;
5397 
5398 /*
5399  * detach_tasks() -- tries to detach up to imbalance weighted load from
5400  * busiest_rq, as part of a balancing operation within domain "sd".
5401  *
5402  * Returns number of detached tasks if successful and 0 otherwise.
5403  */
5404 static int detach_tasks(struct lb_env *env)
5405 {
5406         struct list_head *tasks = &env->src_rq->cfs_tasks;
5407         struct task_struct *p;
5408         unsigned long load;
5409         int detached = 0;
5410 
5411         lockdep_assert_held(&env->src_rq->lock);
5412 
5413         if (env->imbalance <= 0)
5414                 return 0;
5415 
5416         while (!list_empty(tasks)) {
5417                 p = list_first_entry(tasks, struct task_struct, se.group_node);
5418 
5419                 env->loop++;
5420                 /* We've more or less seen every task there is, call it quits */
5421                 if (env->loop > env->loop_max)
5422                         break;
5423 
5424                 /* take a breather every nr_migrate tasks */
5425                 if (env->loop > env->loop_break) {
5426                         env->loop_break += sched_nr_migrate_break;
5427                         env->flags |= LBF_NEED_BREAK;
5428                         break;
5429                 }
5430 
5431                 if (!can_migrate_task(p, env))
5432                         goto next;
5433 
5434                 load = task_h_load(p);
5435 
5436                 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5437                         goto next;
5438 
5439                 if ((load / 2) > env->imbalance)
5440                         goto next;
5441 
5442                 detach_task(p, env);
5443                 list_add(&p->se.group_node, &env->tasks);
5444 
5445                 detached++;
5446                 env->imbalance -= load;
5447 
5448 #ifdef CONFIG_PREEMPT
5449                 /*
5450                  * NEWIDLE balancing is a source of latency, so preemptible
5451                  * kernels will stop after the first task is detached to minimize
5452                  * the critical section.
5453                  */
5454                 if (env->idle == CPU_NEWLY_IDLE)
5455                         break;
5456 #endif
5457 
5458                 /*
5459                  * We only want to steal up to the prescribed amount of
5460                  * weighted load.
5461                  */
5462                 if (env->imbalance <= 0)
5463                         break;
5464 
5465                 continue;
5466 next:
5467                 list_move_tail(&p->se.group_node, tasks);
5468         }
5469 
5470         /*
5471          * Right now, this is one of only two places we collect this stat
5472          * so we can safely collect detach_one_task() stats here rather
5473          * than inside detach_one_task().
5474          */
5475         schedstat_add(env->sd, lb_gained[env->idle], detached);
5476 
5477         return detached;
5478 }
5479 
5480 /*
5481  * attach_task() -- attach the task detached by detach_task() to its new rq.
5482  */
5483 static void attach_task(struct rq *rq, struct task_struct *p)
5484 {
5485         lockdep_assert_held(&rq->lock);
5486 
5487         BUG_ON(task_rq(p) != rq);
5488         p->on_rq = TASK_ON_RQ_QUEUED;
5489         activate_task(rq, p, 0);
5490         check_preempt_curr(rq, p, 0);
5491 }
5492 
5493 /*
5494  * attach_one_task() -- attaches the task returned from detach_one_task() to
5495  * its new rq.
5496  */
5497 static void attach_one_task(struct rq *rq, struct task_struct *p)
5498 {
5499         raw_spin_lock(&rq->lock);
5500         attach_task(rq, p);
5501         raw_spin_unlock(&rq->lock);
5502 }
5503 
5504 /*
5505  * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5506  * new rq.
5507  */
5508 static void attach_tasks(struct lb_env *env)
5509 {
5510         struct list_head *tasks = &env->tasks;
5511         struct task_struct *p;
5512 
5513         raw_spin_lock(&env->dst_rq->lock);
5514 
5515         while (!list_empty(tasks)) {
5516                 p = list_first_entry(tasks, struct task_struct, se.group_node);
5517                 list_del_init(&p->se.group_node);
5518 
5519                 attach_task(env->dst_rq, p);
5520         }
5521 
5522         raw_spin_unlock(&env->dst_rq->lock);
5523 }
5524 
5525 #ifdef CONFIG_FAIR_GROUP_SCHED
5526 /*
5527  * update tg->load_weight by folding this cpu's load_avg
5528  */
5529 static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
5530 {
5531         struct sched_entity *se = tg->se[cpu];
5532         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
5533 
5534         /* throttled entities do not contribute to load */
5535         if (throttled_hierarchy(cfs_rq))
5536                 return;
5537 
5538         update_cfs_rq_blocked_load(cfs_rq, 1);
5539 
5540         if (se) {
5541                 update_entity_load_avg(se, 1);
5542                 /*
5543                  * We pivot on our runnable average having decayed to zero for
5544                  * list removal.  This generally implies that all our children
5545                  * have also been removed (modulo rounding error or bandwidth
5546                  * control); however, such cases are rare and we can fix these
5547                  * at enqueue.
5548                  *
5549                  * TODO: fix up out-of-order children on enqueue.
5550                  */
5551                 if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
5552                         list_del_leaf_cfs_rq(cfs_rq);
5553         } else {
5554                 struct rq *rq = rq_of(cfs_rq);
5555                 update_rq_runnable_avg(rq, rq->nr_running);
5556         }
5557 }
5558 
5559 static void update_blocked_averages(int cpu)
5560 {
5561         struct rq *rq = cpu_rq(cpu);
5562         struct cfs_rq *cfs_rq;
5563         unsigned long flags;
5564 
5565         raw_spin_lock_irqsave(&rq->lock, flags);
5566         update_rq_clock(rq);
5567         /*
5568          * Iterates the task_group tree in a bottom up fashion, see
5569          * list_add_leaf_cfs_rq() for details.
5570          */
5571         for_each_leaf_cfs_rq(rq, cfs_rq) {
5572                 /*
5573                  * Note: We may want to consider periodically releasing
5574                  * rq->lock about these updates so that creating many task
5575                  * groups does not result in continually extending hold time.
5576                  */
5577                 __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
5578         }
5579 
5580         raw_spin_unlock_irqrestore(&rq->lock, flags);
5581 }
5582 
5583 /*
5584  * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5585  * This needs to be done in a top-down fashion because the load of a child
5586  * group is a fraction of its parents load.
5587  */
5588 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5589 {
5590         struct rq *rq = rq_of(cfs_rq);
5591         struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5592         unsigned long now = jiffies;
5593         unsigned long load;
5594 
5595         if (cfs_rq->last_h_load_update == now)
5596                 return;
5597 
5598         cfs_rq->h_load_next = NULL;
5599         for_each_sched_entity(se) {
5600                 cfs_rq = cfs_rq_of(se);
5601                 cfs_rq->h_load_next = se;
5602                 if (cfs_rq->last_h_load_update == now)
5603                         break;
5604         }
5605 
5606         if (!se) {
5607                 cfs_rq->h_load = cfs_rq->runnable_load_avg;
5608                 cfs_rq->last_h_load_update = now;
5609         }
5610 
5611         while ((se = cfs_rq->h_load_next) != NULL) {
5612                 load = cfs_rq->h_load;
5613                 load = div64_ul(load * se->avg.load_avg_contrib,
5614                                 cfs_rq->runnable_load_avg + 1);
5615                 cfs_rq = group_cfs_rq(se);
5616                 cfs_rq->h_load = load;
5617                 cfs_rq->last_h_load_update = now;
5618         }
5619 }
5620 
5621 static unsigned long task_h_load(struct task_struct *p)
5622 {
5623         struct cfs_rq *cfs_rq = task_cfs_rq(p);
5624 
5625         update_cfs_rq_h_load(cfs_rq);
5626         return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
5627                         cfs_rq->runnable_load_avg + 1);
5628 }
5629 #else
5630 static inline void update_blocked_averages(int cpu)
5631 {
5632 }
5633 
5634 static unsigned long task_h_load(struct task_struct *p)
5635 {
5636         return p->se.avg.load_avg_contrib;
5637 }
5638 #endif
5639 
5640 /********** Helpers for find_busiest_group ************************/
5641 
5642 enum group_type {
5643         group_other = 0,
5644         group_imbalanced,
5645         group_overloaded,
5646 };
5647 
5648 /*
5649  * sg_lb_stats - stats of a sched_group required for load_balancing
5650  */
5651 struct sg_lb_stats {
5652         unsigned long avg_load; /*Avg load across the CPUs of the group */
5653         unsigned long group_load; /* Total load over the CPUs of the group */
5654         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
5655         unsigned long load_per_task;
5656         unsigned long group_capacity;
5657         unsigned int sum_nr_running; /* Nr tasks running in the group */
5658         unsigned int group_capacity_factor;
5659         unsigned int idle_cpus;
5660         unsigned int group_weight;
5661         enum group_type group_type;
5662         int group_has_free_capacity;
5663 #ifdef CONFIG_NUMA_BALANCING
5664         unsigned int nr_numa_running;
5665         unsigned int nr_preferred_running;
5666 #endif
5667 };
5668 
5669 /*
5670  * sd_lb_stats - Structure to store the statistics of a sched_domain
5671  *               during load balancing.
5672  */
5673 struct sd_lb_stats {
5674         struct sched_group *busiest;    /* Busiest group in this sd */
5675         struct sched_group *local;      /* Local group in this sd */
5676         unsigned long total_load;       /* Total load of all groups in sd */
5677         unsigned long total_capacity;   /* Total capacity of all groups in sd */
5678         unsigned long avg_load; /* Average load across all groups in sd */
5679 
5680         struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5681         struct sg_lb_stats local_stat;  /* Statistics of the local group */
5682 };
5683 
5684 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
5685 {
5686         /*
5687          * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5688          * local_stat because update_sg_lb_stats() does a full clear/assignment.
5689          * We must however clear busiest_stat::avg_load because
5690          * update_sd_pick_busiest() reads this before assignment.
5691          */
5692         *sds = (struct sd_lb_stats){
5693                 .busiest = NULL,
5694                 .local = NULL,
5695                 .total_load = 0UL,
5696                 .total_capacity = 0UL,
5697                 .busiest_stat = {
5698                         .avg_load = 0UL,
5699                         .sum_nr_running = 0,
5700                         .group_type = group_other,
5701                 },
5702         };
5703 }
5704 
5705 /**
5706  * get_sd_load_idx - Obtain the load index for a given sched domain.
5707  * @sd: The sched_domain whose load_idx is to be obtained.
5708  * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5709  *
5710  * Return: The load index.
5711  */
5712 static inline int get_sd_load_idx(struct sched_domain *sd,
5713                                         enum cpu_idle_type idle)
5714 {
5715         int load_idx;
5716 
5717         switch (idle) {
5718         case CPU_NOT_IDLE:
5719                 load_idx = sd->busy_idx;
5720                 break;
5721 
5722         case CPU_NEWLY_IDLE:
5723                 load_idx = sd->newidle_idx;
5724                 break;
5725         default:
5726                 load_idx = sd->idle_idx;
5727                 break;
5728         }
5729 
5730         return load_idx;
5731 }
5732 
5733 static unsigned long default_scale_capacity(struct sched_domain *sd, int cpu)
5734 {
5735         return SCHED_CAPACITY_SCALE;
5736 }
5737 
5738 unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu)
5739 {
5740         return default_scale_capacity(sd, cpu);
5741 }
5742 
5743 static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
5744 {
5745         if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
5746                 return sd->smt_gain / sd->span_weight;
5747 
5748         return SCHED_CAPACITY_SCALE;
5749 }
5750 
5751 unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
5752 {
5753         return default_scale_cpu_capacity(sd, cpu);
5754 }
5755 
5756 static unsigned long scale_rt_capacity(int cpu)
5757 {
5758         struct rq *rq = cpu_rq(cpu);
5759         u64 total, available, age_stamp, avg;
5760         s64 delta;
5761 
5762         /*
5763          * Since we're reading these variables without serialization make sure
5764          * we read them once before doing sanity checks on them.
5765          */
5766         age_stamp = ACCESS_ONCE(rq->age_stamp);
5767         avg = ACCESS_ONCE(rq->rt_avg);
5768 
5769         delta = rq_clock(rq) - age_stamp;
5770         if (unlikely(delta < 0))
5771                 delta = 0;
5772 
5773         total = sched_avg_period() + delta;
5774 
5775         if (unlikely(total < avg)) {
5776                 /* Ensures that capacity won't end up being negative */
5777                 available = 0;
5778         } else {
5779                 available = total - avg;
5780         }
5781 
5782         if (unlikely((s64)total < SCHED_CAPACITY_SCALE))
5783                 total = SCHED_CAPACITY_SCALE;
5784 
5785         total >>= SCHED_CAPACITY_SHIFT;
5786 
5787         return div_u64(available, total);
5788 }
5789 
5790 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
5791 {
5792         unsigned long capacity = SCHED_CAPACITY_SCALE;
5793         struct sched_group *sdg = sd->groups;
5794 
5795         if (sched_feat(ARCH_CAPACITY))
5796                 capacity *= arch_scale_cpu_capacity(sd, cpu);
5797         else
5798                 capacity *= default_scale_cpu_capacity(sd, cpu);
5799 
5800         capacity >>= SCHED_CAPACITY_SHIFT;
5801 
5802         sdg->sgc->capacity_orig = capacity;
5803 
5804         if (sched_feat(ARCH_CAPACITY))
5805                 capacity *= arch_scale_freq_capacity(sd, cpu);
5806         else
5807                 capacity *= default_scale_capacity(sd, cpu);
5808 
5809         capacity >>= SCHED_CAPACITY_SHIFT;
5810 
5811         capacity *= scale_rt_capacity(cpu);
5812         capacity >>= SCHED_CAPACITY_SHIFT;
5813 
5814         if (!capacity)
5815                 capacity = 1;
5816 
5817         cpu_rq(cpu)->cpu_capacity = capacity;
5818         sdg->sgc->capacity = capacity;
5819 }
5820 
5821 void update_group_capacity(struct sched_domain *sd, int cpu)
5822 {
5823         struct sched_domain *child = sd->child;
5824         struct sched_group *group, *sdg = sd->groups;
5825         unsigned long capacity, capacity_orig;
5826         unsigned long interval;
5827 
5828         interval = msecs_to_jiffies(sd->balance_interval);
5829         interval = clamp(interval, 1UL, max_load_balance_interval);
5830         sdg->sgc->next_update = jiffies + interval;
5831 
5832         if (!child) {
5833                 update_cpu_capacity(sd, cpu);
5834                 return;
5835         }
5836 
5837         capacity_orig = capacity = 0;
5838 
5839         if (child->flags & SD_OVERLAP) {
5840                 /*
5841                  * SD_OVERLAP domains cannot assume that child groups
5842                  * span the current group.
5843                  */
5844 
5845                 for_each_cpu(cpu, sched_group_cpus(sdg)) {
5846                         struct sched_group_capacity *sgc;
5847                         struct rq *rq = cpu_rq(cpu);
5848 
5849                         /*
5850                          * build_sched_domains() -> init_sched_groups_capacity()
5851                          * gets here before we've attached the domains to the
5852                          * runqueues.
5853                          *
5854                          * Use capacity_of(), which is set irrespective of domains
5855                          * in update_cpu_capacity().
5856                          *
5857                          * This avoids capacity/capacity_orig from being 0 and
5858                          * causing divide-by-zero issues on boot.
5859                          *
5860                          * Runtime updates will correct capacity_orig.
5861                          */
5862                         if (unlikely(!rq->sd)) {
5863                                 capacity_orig += capacity_of(cpu);
5864                                 capacity += capacity_of(cpu);
5865                                 continue;
5866                         }
5867 
5868                         sgc = rq->sd->groups->sgc;
5869                         capacity_orig += sgc->capacity_orig;
5870                         capacity += sgc->capacity;
5871                 }
5872         } else  {
5873                 /*
5874                  * !SD_OVERLAP domains can assume that child groups
5875                  * span the current group.
5876                  */ 
5877 
5878                 group = child->groups;
5879                 do {
5880                         capacity_orig += group->sgc->capacity_orig;
5881                         capacity += group->sgc->capacity;
5882                         group = group->next;
5883                 } while (group != child->groups);
5884         }
5885 
5886         sdg->sgc->capacity_orig = capacity_orig;
5887         sdg->sgc->capacity = capacity;
5888 }
5889 
5890 /*
5891  * Try and fix up capacity for tiny siblings, this is needed when
5892  * things like SD_ASYM_PACKING need f_b_g to select another sibling
5893  * which on its own isn't powerful enough.
5894  *
5895  * See update_sd_pick_busiest() and check_asym_packing().
5896  */
5897 static inline int
5898 fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
5899 {
5900         /*
5901          * Only siblings can have significantly less than SCHED_CAPACITY_SCALE
5902          */
5903         if (!(sd->flags & SD_SHARE_CPUCAPACITY))
5904                 return 0;
5905 
5906         /*
5907          * If ~90% of the cpu_capacity is still there, we're good.
5908          */
5909         if (group->sgc->capacity * 32 > group->sgc->capacity_orig * 29)
5910                 return 1;
5911 
5912         return 0;
5913 }
5914 
5915 /*
5916  * Group imbalance indicates (and tries to solve) the problem where balancing
5917  * groups is inadequate due to tsk_cpus_allowed() constraints.
5918  *
5919  * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
5920  * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
5921  * Something like:
5922  *
5923  *      { 0 1 2 3 } { 4 5 6 7 }
5924  *              *     * * *
5925  *
5926  * If we were to balance group-wise we'd place two tasks in the first group and
5927  * two tasks in the second group. Clearly this is undesired as it will overload
5928  * cpu 3 and leave one of the cpus in the second group unused.
5929  *
5930  * The current solution to this issue is detecting the skew in the first group
5931  * by noticing the lower domain failed to reach balance and had difficulty
5932  * moving tasks due to affinity constraints.
5933  *
5934  * When this is so detected; this group becomes a candidate for busiest; see
5935  * update_sd_pick_busiest(). And calculate_imbalance() and
5936  * find_busiest_group() avoid some of the usual balance conditions to allow it
5937  * to create an effective group imbalance.
5938  *
5939  * This is a somewhat tricky proposition since the next run might not find the
5940  * group imbalance and decide the groups need to be balanced again. A most
5941  * subtle and fragile situation.
5942  */
5943 
5944 static inline int sg_imbalanced(struct sched_group *group)
5945 {
5946         return group->sgc->imbalance;
5947 }
5948 
5949 /*
5950  * Compute the group capacity factor.
5951  *
5952  * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by
5953  * first dividing out the smt factor and computing the actual number of cores
5954  * and limit unit capacity with that.
5955  */
5956 static inline int sg_capacity_factor(struct lb_env *env, struct sched_group *group)
5957 {
5958         unsigned int capacity_factor, smt, cpus;
5959         unsigned int capacity, capacity_orig;
5960 
5961         capacity = group->sgc->capacity;
5962         capacity_orig = group->sgc->capacity_orig;
5963         cpus = group->group_weight;
5964 
5965         /* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */
5966         smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, capacity_orig);
5967         capacity_factor = cpus / smt; /* cores */
5968 
5969         capacity_factor = min_t(unsigned,
5970                 capacity_factor, DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE));
5971         if (!capacity_factor)
5972                 capacity_factor = fix_small_capacity(env->sd, group);
5973 
5974         return capacity_factor;
5975 }
5976 
5977 static enum group_type
5978 group_classify(struct sched_group *group, struct sg_lb_stats *sgs)
5979 {
5980         if (sgs->sum_nr_running > sgs->group_capacity_factor)
5981                 return group_overloaded;
5982 
5983         if (sg_imbalanced(group))
5984                 return group_imbalanced;
5985 
5986         return group_other;
5987 }
5988 
5989 /**
5990  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
5991  * @env: The load balancing environment.
5992  * @group: sched_group whose statistics are to be updated.
5993  * @load_idx: Load index of sched_domain of this_cpu for load calc.
5994  * @local_group: Does group contain this_cpu.
5995  * @sgs: variable to hold the statistics for this group.
5996  * @overload: Indicate more than one runnable task for any CPU.
5997  */
5998 static inline void update_sg_lb_stats(struct lb_env *env,
5999                         struct sched_group *group, int load_idx,
6000                         int local_group, struct sg_lb_stats *sgs,
6001                         bool *overload)
6002 {
6003         unsigned long load;
6004         int i;
6005 
6006         memset(sgs, 0, sizeof(*sgs));
6007 
6008         for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6009                 struct rq *rq = cpu_rq(i);
6010 
6011                 /* Bias balancing toward cpus of our domain */
6012                 if (local_group)
6013                         load = target_load(i, load_idx);
6014                 else
6015                         load = source_load(i, load_idx);
6016 
6017                 sgs->group_load += load;
6018                 sgs->sum_nr_running += rq->cfs.h_nr_running;
6019 
6020                 if (rq->nr_running > 1)
6021                         *overload = true;
6022 
6023 #ifdef CONFIG_NUMA_BALANCING
6024                 sgs->nr_numa_running += rq->nr_numa_running;
6025                 sgs->nr_preferred_running += rq->nr_preferred_running;
6026 #endif
6027                 sgs->sum_weighted_load += weighted_cpuload(i);
6028                 if (idle_cpu(i))
6029                         sgs->idle_cpus++;
6030         }
6031 
6032         /* Adjust by relative CPU capacity of the group */
6033         sgs->group_capacity = group->sgc->capacity;
6034         sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6035 
6036         if (sgs->sum_nr_running)
6037                 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6038 
6039         sgs->group_weight = group->group_weight;
6040         sgs->group_capacity_factor = sg_capacity_factor(env, group);
6041         sgs->group_type = group_classify(group, sgs);
6042 
6043         if (sgs->group_capacity_factor > sgs->sum_nr_running)
6044                 sgs->group_has_free_capacity = 1;
6045 }
6046 
6047 /**
6048  * update_sd_pick_busiest - return 1 on busiest group
6049  * @env: The load balancing environment.
6050  * @sds: sched_domain statistics
6051  * @sg: sched_group candidate to be checked for being the busiest
6052  * @sgs: sched_group statistics
6053  *
6054  * Determine if @sg is a busier group than the previously selected
6055  * busiest group.
6056  *
6057  * Return: %true if @sg is a busier group than the previously selected
6058  * busiest group. %false otherwise.
6059  */
6060 static bool update_sd_pick_busiest(struct lb_env *env,
6061                                    struct sd_lb_stats *sds,
6062                                    struct sched_group *sg,
6063                                    struct sg_lb_stats *sgs)
6064 {
6065         struct sg_lb_stats *busiest = &sds->busiest_stat;
6066 
6067         if (sgs->group_type > busiest->group_type)
6068                 return true;
6069 
6070         if (sgs->group_type < busiest->group_type)
6071                 return false;
6072 
6073         if (sgs->avg_load <= busiest->avg_load)
6074                 return false;
6075 
6076         /* This is the busiest node in its class. */
6077         if (!(env->sd->flags & SD_ASYM_PACKING))
6078                 return true;
6079 
6080         /*
6081          * ASYM_PACKING needs to move all the work to the lowest
6082          * numbered CPUs in the group, therefore mark all groups
6083          * higher than ourself as busy.
6084          */
6085         if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6086                 if (!sds->busiest)
6087                         return true;
6088 
6089                 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6090                         return true;
6091         }
6092 
6093         return false;
6094 }
6095 
6096 #ifdef CONFIG_NUMA_BALANCING
6097 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6098 {
6099         if (sgs->sum_nr_running > sgs->nr_numa_running)
6100                 return regular;
6101         if (sgs->sum_nr_running > sgs->nr_preferred_running)
6102                 return remote;
6103         return all;
6104 }
6105 
6106 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6107 {
6108         if (rq->nr_running > rq->nr_numa_running)
6109                 return regular;
6110         if (rq->nr_running > rq->nr_preferred_running)
6111                 return remote;
6112         return all;
6113 }
6114 #else
6115 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6116 {
6117         return all;
6118 }
6119 
6120 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6121 {
6122         return regular;
6123 }
6124 #endif /* CONFIG_NUMA_BALANCING */
6125 
6126 /**
6127  * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6128  * @env: The load balancing environment.
6129  * @sds: variable to hold the statistics for this sched_domain.
6130  */
6131 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6132 {
6133         struct sched_domain *child = env->sd->child;
6134         struct sched_group *sg = env->sd->groups;
6135         struct sg_lb_stats tmp_sgs;
6136         int load_idx, prefer_sibling = 0;
6137         bool overload = false;
6138 
6139         if (child && child->flags & SD_PREFER_SIBLING)
6140                 prefer_sibling = 1;
6141 
6142         load_idx = get_sd_load_idx(env->sd, env->idle);
6143 
6144         do {
6145                 struct sg_lb_stats *sgs = &tmp_sgs;
6146                 int local_group;
6147 
6148                 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6149                 if (local_group) {
6150                         sds->local = sg;
6151                         sgs = &sds->local_stat;
6152 
6153                         if (env->idle != CPU_NEWLY_IDLE ||
6154                             time_after_eq(jiffies, sg->sgc->next_update))
6155                                 update_group_capacity(env->sd, env->dst_cpu);
6156                 }
6157 
6158                 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6159                                                 &overload);
6160 
6161                 if (local_group)
6162                         goto next_group;
6163 
6164                 /*
6165                  * In case the child domain prefers tasks go to siblings
6166                  * first, lower the sg capacity factor to one so that we'll try
6167                  * and move all the excess tasks away. We lower the capacity
6168                  * of a group only if the local group has the capacity to fit
6169                  * these excess tasks, i.e. nr_running < group_capacity_factor. The
6170                  * extra check prevents the case where you always pull from the
6171                  * heaviest group when it is already under-utilized (possible
6172                  * with a large weight task outweighs the tasks on the system).
6173                  */
6174                 if (prefer_sibling && sds->local &&
6175                     sds->local_stat.group_has_free_capacity)
6176                         sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U);
6177 
6178                 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6179                         sds->busiest = sg;
6180                         sds->busiest_stat = *sgs;
6181                 }
6182 
6183 next_group:
6184                 /* Now, start updating sd_lb_stats */
6185                 sds->total_load += sgs->group_load;
6186                 sds->total_capacity += sgs->group_capacity;
6187 
6188                 sg = sg->next;
6189         } while (sg != env->sd->groups);
6190 
6191         if (env->sd->flags & SD_NUMA)
6192                 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6193 
6194         if (!env->sd->parent) {
6195                 /* update overload indicator if we are at root domain */
6196                 if (env->dst_rq->rd->overload != overload)
6197                         env->dst_rq->rd->overload = overload;
6198         }
6199 
6200 }
6201 
6202 /**
6203  * check_asym_packing - Check to see if the group is packed into the
6204  *                      sched doman.
6205  *
6206  * This is primarily intended to used at the sibling level.  Some
6207  * cores like POWER7 prefer to use lower numbered SMT threads.  In the
6208  * case of POWER7, it can move to lower SMT modes only when higher
6209  * threads are idle.  When in lower SMT modes, the threads will
6210  * perform better since they share less core resources.  Hence when we
6211  * have idle threads, we want them to be the higher ones.
6212  *
6213  * This packing function is run on idle threads.  It checks to see if
6214  * the busiest CPU in this domain (core in the P7 case) has a higher
6215  * CPU number than the packing function is being run on.  Here we are
6216  * assuming lower CPU number will be equivalent to lower a SMT thread
6217  * number.
6218  *
6219  * Return: 1 when packing is required and a task should be moved to
6220  * this CPU.  The amount of the imbalance is returned in *imbalance.
6221  *
6222  * @env: The load balancing environment.
6223  * @sds: Statistics of the sched_domain which is to be packed
6224  */
6225 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6226 {
6227         int busiest_cpu;
6228 
6229         if (!(env->sd->flags & SD_ASYM_PACKING))
6230                 return 0;
6231 
6232         if (!sds->busiest)
6233                 return 0;
6234 
6235         busiest_cpu = group_first_cpu(sds->busiest);
6236         if (env->dst_cpu > busiest_cpu)
6237                 return 0;
6238 
6239         env->imbalance = DIV_ROUND_CLOSEST(
6240                 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6241                 SCHED_CAPACITY_SCALE);
6242 
6243         return 1;
6244 }
6245 
6246 /**
6247  * fix_small_imbalance - Calculate the minor imbalance that exists
6248  *                      amongst the groups of a sched_domain, during
6249  *                      load balancing.
6250  * @env: The load balancing environment.
6251  * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6252  */
6253 static inline
6254 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6255 {
6256         unsigned long tmp, capa_now = 0, capa_move = 0;
6257         unsigned int imbn = 2;
6258         unsigned long scaled_busy_load_per_task;
6259         struct sg_lb_stats *local, *busiest;
6260 
6261         local = &sds->local_stat;
6262         busiest = &sds->busiest_stat;
6263 
6264         if (!local->sum_nr_running)
6265                 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6266         else if (busiest->load_per_task > local->load_per_task)
6267                 imbn = 1;
6268 
6269         scaled_busy_load_per_task =
6270                 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6271                 busiest->group_capacity;
6272 
6273         if (busiest->avg_load + scaled_busy_load_per_task >=
6274             local->avg_load + (scaled_busy_load_per_task * imbn)) {
6275                 env->imbalance = busiest->load_per_task;
6276                 return;
6277         }
6278 
6279         /*
6280          * OK, we don't have enough imbalance to justify moving tasks,
6281          * however we may be able to increase total CPU capacity used by
6282          * moving them.
6283          */
6284 
6285         capa_now += busiest->group_capacity *
6286                         min(busiest->load_per_task, busiest->avg_load);
6287         capa_now += local->group_capacity *
6288                         min(local->load_per_task, local->avg_load);
6289         capa_now /= SCHED_CAPACITY_SCALE;
6290 
6291         /* Amount of load we'd subtract */
6292         if (busiest->avg_load > scaled_busy_load_per_task) {
6293                 capa_move += busiest->group_capacity *
6294                             min(busiest->load_per_task,
6295                                 busiest->avg_load - scaled_busy_load_per_task);
6296         }
6297 
6298         /* Amount of load we'd add */
6299         if (busiest->avg_load * busiest->group_capacity <
6300             busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6301                 tmp = (busiest->avg_load * busiest->group_capacity) /
6302                       local->group_capacity;
6303         } else {
6304                 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6305                       local->group_capacity;
6306         }
6307         capa_move += local->group_capacity *
6308                     min(local->load_per_task, local->avg_load + tmp);
6309         capa_move /= SCHED_CAPACITY_SCALE;
6310 
6311         /* Move if we gain throughput */
6312         if (capa_move > capa_now)
6313                 env->imbalance = busiest->load_per_task;
6314 }
6315 
6316 /**
6317  * calculate_imbalance - Calculate the amount of imbalance present within the
6318  *                       groups of a given sched_domain during load balance.
6319  * @env: load balance environment
6320  * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6321  */
6322 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6323 {
6324         unsigned long max_pull, load_above_capacity = ~0UL;
6325         struct sg_lb_stats *local, *busiest;
6326 
6327         local = &sds->local_stat;
6328         busiest = &sds->busiest_stat;
6329 
6330         if (busiest->group_type == group_imbalanced) {
6331                 /*
6332                  * In the group_imb case we cannot rely on group-wide averages
6333                  * to ensure cpu-load equilibrium, look at wider averages. XXX
6334                  */
6335                 busiest->load_per_task =
6336                         min(busiest->load_per_task, sds->avg_load);
6337         }
6338 
6339         /*
6340          * In the presence of smp nice balancing, certain scenarios can have
6341          * max load less than avg load(as we skip the groups at or below
6342          * its cpu_capacity, while calculating max_load..)
6343          */
6344         if (busiest->avg_load <= sds->avg_load ||
6345             local->avg_load >= sds->avg_load) {
6346                 env->imbalance = 0;
6347                 return fix_small_imbalance(env, sds);
6348         }
6349 
6350         /*
6351          * If there aren't any idle cpus, avoid creating some.
6352          */
6353         if (busiest->group_type == group_overloaded &&
6354             local->group_type   == group_overloaded) {
6355                 load_above_capacity =
6356                         (busiest->sum_nr_running - busiest->group_capacity_factor);
6357 
6358                 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE);
6359                 load_above_capacity /= busiest->group_capacity;
6360         }
6361 
6362         /*
6363          * We're trying to get all the cpus to the average_load, so we don't
6364          * want to push ourselves above the average load, nor do we wish to
6365          * reduce the max loaded cpu below the average load. At the same time,
6366          * we also don't want to reduce the group load below the group capacity
6367          * (so that we can implement power-savings policies etc). Thus we look
6368          * for the minimum possible imbalance.
6369          */
6370         max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6371 
6372         /* How much load to actually move to equalise the imbalance */
6373         env->imbalance = min(
6374                 max_pull * busiest->group_capacity,
6375                 (sds->avg_load - local->avg_load) * local->group_capacity
6376         ) / SCHED_CAPACITY_SCALE;
6377 
6378         /*
6379          * if *imbalance is less than the average load per runnable task
6380          * there is no guarantee that any tasks will be moved so we'll have
6381          * a think about bumping its value to force at least one task to be
6382          * moved
6383          */
6384         if (env->imbalance < busiest->load_per_task)
6385                 return fix_small_imbalance(env, sds);
6386 }
6387 
6388 /******* find_busiest_group() helpers end here *********************/
6389 
6390 /**
6391  * find_busiest_group - Returns the busiest group within the sched_domain
6392  * if there is an imbalance. If there isn't an imbalance, and
6393  * the user has opted for power-savings, it returns a group whose
6394  * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6395  * such a group exists.
6396  *
6397  * Also calculates the amount of weighted load which should be moved
6398  * to restore balance.
6399  *
6400  * @env: The load balancing environment.
6401  *
6402  * Return:      - The busiest group if imbalance exists.
6403  *              - If no imbalance and user has opted for power-savings balance,
6404  *                 return the least loaded group whose CPUs can be
6405  *                 put to idle by rebalancing its tasks onto our group.
6406  */
6407 static struct sched_group *find_busiest_group(struct lb_env *env)
6408 {
6409         struct sg_lb_stats *local, *busiest;
6410         struct sd_lb_stats sds;
6411 
6412         init_sd_lb_stats(&sds);
6413 
6414         /*
6415          * Compute the various statistics relavent for load balancing at
6416          * this level.
6417          */
6418         update_sd_lb_stats(env, &sds);
6419         local = &sds.local_stat;
6420         busiest = &sds.busiest_stat;
6421 
6422         if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6423             check_asym_packing(env, &sds))
6424                 return sds.busiest;
6425 
6426         /* There is no busy sibling group to pull tasks from */
6427         if (!sds.busiest || busiest->sum_nr_running == 0)
6428                 goto out_balanced;
6429 
6430         sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6431                                                 / sds.total_capacity;
6432 
6433         /*
6434          * If the busiest group is imbalanced the below checks don't
6435          * work because they assume all things are equal, which typically
6436          * isn't true due to cpus_allowed constraints and the like.
6437          */
6438         if (busiest->group_type == group_imbalanced)
6439                 goto force_balance;
6440 
6441         /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6442         if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity &&
6443             !busiest->group_has_free_capacity)
6444                 goto force_balance;
6445 
6446         /*
6447          * If the local group is busier than the selected busiest group
6448          * don't try and pull any tasks.
6449          */
6450         if (local->avg_load >= busiest->avg_load)
6451                 goto out_balanced;
6452 
6453         /*
6454          * Don't pull any tasks if this group is already above the domain
6455          * average load.
6456          */
6457         if (local->avg_load >= sds.avg_load)
6458                 goto out_balanced;
6459 
6460         if (env->idle == CPU_IDLE) {
6461                 /*
6462                  * This cpu is idle. If the busiest group is not overloaded
6463                  * and there is no imbalance between this and busiest group
6464                  * wrt idle cpus, it is balanced. The imbalance becomes
6465                  * significant if the diff is greater than 1 otherwise we
6466                  * might end up to just move the imbalance on another group
6467                  */
6468                 if ((busiest->group_type != group_overloaded) &&
6469                                 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6470                         goto out_balanced;
6471         } else {
6472                 /*
6473                  * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6474                  * imbalance_pct to be conservative.
6475                  */
6476                 if (100 * busiest->avg_load <=
6477                                 env->sd->imbalance_pct * local->avg_load)
6478                         goto out_balanced;
6479         }
6480 
6481 force_balance:
6482         /* Looks like there is an imbalance. Compute it */
6483         calculate_imbalance(env, &sds);
6484         return sds.busiest;
6485 
6486 out_balanced:
6487         env->imbalance = 0;
6488         return NULL;
6489 }
6490 
6491 /*
6492  * find_busiest_queue - find the busiest runqueue among the cpus in group.
6493  */
6494 static struct rq *find_busiest_queue(struct lb_env *env,
6495                                      struct sched_group *group)
6496 {
6497         struct rq *busiest = NULL, *rq;
6498         unsigned long busiest_load = 0, busiest_capacity = 1;
6499         int i;
6500 
6501         for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6502                 unsigned long capacity, capacity_factor, wl;
6503                 enum fbq_type rt;
6504 
6505                 rq = cpu_rq(i);
6506                 rt = fbq_classify_rq(rq);
6507 
6508                 /*
6509                  * We classify groups/runqueues into three groups:
6510                  *  - regular: there are !numa tasks
6511                  *  - remote:  there are numa tasks that run on the 'wrong' node
6512                  *  - all:     there is no distinction
6513                  *
6514                  * In order to avoid migrating ideally placed numa tasks,
6515                  * ignore those when there's better options.
6516                  *
6517                  * If we ignore the actual busiest queue to migrate another
6518                  * task, the next balance pass can still reduce the busiest
6519                  * queue by moving tasks around inside the node.
6520                  *
6521                  * If we cannot move enough load due to this classification
6522                  * the next pass will adjust the group classification and
6523                  * allow migration of more tasks.
6524                  *
6525                  * Both cases only affect the total convergence complexity.
6526                  */
6527                 if (rt > env->fbq_type)
6528                         continue;
6529 
6530                 capacity = capacity_of(i);
6531                 capacity_factor = DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE);
6532                 if (!capacity_factor)
6533                         capacity_factor = fix_small_capacity(env->sd, group);
6534 
6535                 wl = weighted_cpuload(i);
6536 
6537                 /*
6538                  * When comparing with imbalance, use weighted_cpuload()
6539                  * which is not scaled with the cpu capacity.
6540                  */
6541                 if (capacity_factor && rq->nr_running == 1 && wl > env->imbalance)
6542                         continue;
6543 
6544                 /*
6545                  * For the load comparisons with the other cpu's, consider
6546                  * the weighted_cpuload() scaled with the cpu capacity, so
6547                  * that the load can be moved away from the cpu that is
6548                  * potentially running at a lower capacity.
6549                  *
6550                  * Thus we're looking for max(wl_i / capacity_i), crosswise
6551                  * multiplication to rid ourselves of the division works out
6552                  * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
6553                  * our previous maximum.
6554                  */
6555                 if (wl * busiest_capacity > busiest_load * capacity) {
6556                         busiest_load = wl;
6557                         busiest_capacity = capacity;
6558                         busiest = rq;
6559                 }
6560         }
6561 
6562         return busiest;
6563 }
6564 
6565 /*
6566  * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6567  * so long as it is large enough.
6568  */
6569 #define MAX_PINNED_INTERVAL     512
6570 
6571 /* Working cpumask for load_balance and load_balance_newidle. */
6572 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6573 
6574 static int need_active_balance(struct lb_env *env)
6575 {
6576         struct sched_domain *sd = env->sd;
6577 
6578         if (env->idle == CPU_NEWLY_IDLE) {
6579 
6580                 /*
6581                  * ASYM_PACKING needs to force migrate tasks from busy but
6582                  * higher numbered CPUs in order to pack all tasks in the
6583                  * lowest numbered CPUs.
6584                  */
6585                 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6586                         return 1;
6587         }
6588 
6589         return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6590 }
6591 
6592 static int active_load_balance_cpu_stop(void *data);
6593 
6594 static int should_we_balance(struct lb_env *env)
6595 {
6596         struct sched_group *sg = env->sd->groups;
6597         struct cpumask *sg_cpus, *sg_mask;
6598         int cpu, balance_cpu = -1;
6599 
6600         /*
6601          * In the newly idle case, we will allow all the cpu's
6602          * to do the newly idle load balance.
6603          */
6604         if (env->idle == CPU_NEWLY_IDLE)
6605                 return 1;
6606 
6607         sg_cpus = sched_group_cpus(sg);
6608         sg_mask = sched_group_mask(sg);
6609         /* Try to find first idle cpu */
6610         for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6611                 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6612                         continue;
6613 
6614                 balance_cpu = cpu;
6615                 break;
6616         }
6617 
6618         if (balance_cpu == -1)
6619                 balance_cpu = group_balance_cpu(sg);
6620 
6621         /*
6622          * First idle cpu or the first cpu(busiest) in this sched group
6623          * is eligible for doing load balancing at this and above domains.
6624          */
6625         return balance_cpu == env->dst_cpu;
6626 }
6627 
6628 /*
6629  * Check this_cpu to ensure it is balanced within domain. Attempt to move
6630  * tasks if there is an imbalance.
6631  */
6632 static int load_balance(int this_cpu, struct rq *this_rq,
6633                         struct sched_domain *sd, enum cpu_idle_type idle,
6634                         int *continue_balancing)
6635 {
6636         int ld_moved, cur_ld_moved, active_balance = 0;
6637         struct sched_domain *sd_parent = sd->parent;
6638         struct sched_group *group;
6639         struct rq *busiest;
6640         unsigned long flags;
6641         struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6642 
6643         struct lb_env env = {
6644                 .sd             = sd,
6645                 .dst_cpu        = this_cpu,
6646                 .dst_rq         = this_rq,
6647                 .dst_grpmask    = sched_group_cpus(sd->groups),
6648                 .idle           = idle,
6649                 .loop_break     = sched_nr_migrate_break,
6650                 .cpus           = cpus,
6651                 .fbq_type       = all,
6652                 .tasks          = LIST_HEAD_INIT(env.tasks),
6653         };
6654 
6655         /*
6656          * For NEWLY_IDLE load_balancing, we don't need to consider
6657          * other cpus in our group
6658          */
6659         if (idle == CPU_NEWLY_IDLE)
6660                 env.dst_grpmask = NULL;
6661 
6662         cpumask_copy(cpus, cpu_active_mask);
6663 
6664         schedstat_inc(sd, lb_count[idle]);
6665 
6666 redo:
6667         if (!should_we_balance(&env)) {
6668                 *continue_balancing = 0;
6669                 goto out_balanced;
6670         }
6671 
6672         group = find_busiest_group(&env);
6673         if (!group) {
6674                 schedstat_inc(sd, lb_nobusyg[idle]);
6675                 goto out_balanced;
6676         }
6677 
6678         busiest = find_busiest_queue(&env, group);
6679         if (!busiest) {
6680                 schedstat_inc(sd, lb_nobusyq[idle]);
6681                 goto out_balanced;
6682         }
6683 
6684         BUG_ON(busiest == env.dst_rq);
6685 
6686         schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6687 
6688         ld_moved = 0;
6689         if (busiest->nr_running > 1) {
6690                 /*
6691                  * Attempt to move tasks. If find_busiest_group has found
6692                  * an imbalance but busiest->nr_running <= 1, the group is
6693                  * still unbalanced. ld_moved simply stays zero, so it is
6694                  * correctly treated as an imbalance.
6695                  */
6696                 env.flags |= LBF_ALL_PINNED;
6697                 env.src_cpu   = busiest->cpu;
6698                 env.src_rq    = busiest;
6699                 env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6700 
6701 more_balance:
6702                 raw_spin_lock_irqsave(&busiest->lock, flags);
6703 
6704                 /*
6705                  * cur_ld_moved - load moved in current iteration
6706                  * ld_moved     - cumulative load moved across iterations
6707                  */
6708                 cur_ld_moved = detach_tasks(&env);
6709 
6710                 /*
6711                  * We've detached some tasks from busiest_rq. Every
6712                  * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
6713                  * unlock busiest->lock, and we are able to be sure
6714                  * that nobody can manipulate the tasks in parallel.
6715                  * See task_rq_lock() family for the details.
6716                  */
6717 
6718                 raw_spin_unlock(&busiest->lock);
6719 
6720                 if (cur_ld_moved) {
6721                         attach_tasks(&env);
6722                         ld_moved += cur_ld_moved;
6723                 }
6724 
6725                 local_irq_restore(flags);
6726 
6727                 if (env.flags & LBF_NEED_BREAK) {
6728                         env.flags &= ~LBF_NEED_BREAK;
6729                         goto more_balance;
6730                 }
6731 
6732                 /*
6733                  * Revisit (affine) tasks on src_cpu that couldn't be moved to
6734                  * us and move them to an alternate dst_cpu in our sched_group
6735                  * where they can run. The upper limit on how many times we
6736                  * iterate on same src_cpu is dependent on number of cpus in our
6737                  * sched_group.
6738                  *
6739                  * This changes load balance semantics a bit on who can move
6740                  * load to a given_cpu. In addition to the given_cpu itself
6741                  * (or a ilb_cpu acting on its behalf where given_cpu is
6742                  * nohz-idle), we now have balance_cpu in a position to move
6743                  * load to given_cpu. In rare situations, this may cause
6744                  * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
6745                  * _independently_ and at _same_ time to move some load to
6746                  * given_cpu) causing exceess load to be moved to given_cpu.
6747                  * This however should not happen so much in practice and
6748                  * moreover subsequent load balance cycles should correct the
6749                  * excess load moved.
6750                  */
6751                 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6752 
6753                         /* Prevent to re-select dst_cpu via env's cpus */
6754                         cpumask_clear_cpu(env.dst_cpu, env.cpus);
6755 
6756                         env.dst_rq       = cpu_rq(env.new_dst_cpu);
6757                         env.dst_cpu      = env.new_dst_cpu;
6758                         env.flags       &= ~LBF_DST_PINNED;
6759                         env.loop         = 0;
6760                         env.loop_break   = sched_nr_migrate_break;
6761 
6762                         /*
6763                          * Go back to "more_balance" rather than "redo" since we
6764                          * need to continue with same src_cpu.
6765                          */
6766                         goto more_balance;
6767                 }
6768 
6769                 /*
6770                  * We failed to reach balance because of affinity.
6771                  */
6772                 if (sd_parent) {
6773                         int *group_imbalance = &sd_parent->groups->sgc->imbalance;
6774 
6775                         if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
6776                                 *group_imbalance = 1;
6777                 }
6778 
6779                 /* All tasks on this runqueue were pinned by CPU affinity */
6780                 if (unlikely(env.flags & LBF_ALL_PINNED)) {
6781                         cpumask_clear_cpu(cpu_of(busiest), cpus);
6782                         if (!cpumask_empty(cpus)) {
6783                                 env.loop = 0;
6784                                 env.loop_break = sched_nr_migrate_break;
6785                                 goto redo;
6786                         }
6787                         goto out_all_pinned;
6788                 }
6789         }
6790 
6791         if (!ld_moved) {
6792                 schedstat_inc(sd, lb_failed[idle]);
6793                 /*
6794                  * Increment the failure counter only on periodic balance.
6795                  * We do not want newidle balance, which can be very
6796                  * frequent, pollute the failure counter causing
6797                  * excessive cache_hot migrations and active balances.
6798                  */
6799                 if (idle != CPU_NEWLY_IDLE)
6800                         sd->nr_balance_failed++;
6801 
6802                 if (need_active_balance(&env)) {
6803                         raw_spin_lock_irqsave(&busiest->lock, flags);
6804 
6805                         /* don't kick the active_load_balance_cpu_stop,
6806                          * if the curr task on busiest cpu can't be
6807                          * moved to this_cpu
6808                          */
6809                         if (!cpumask_test_cpu(this_cpu,
6810                                         tsk_cpus_allowed(busiest->curr))) {
6811                                 raw_spin_unlock_irqrestore(&busiest->lock,
6812                                                             flags);
6813                                 env.flags |= LBF_ALL_PINNED;
6814                                 goto out_one_pinned;
6815                         }
6816 
6817                         /*
6818                          * ->active_balance synchronizes accesses to
6819                          * ->active_balance_work.  Once set, it's cleared
6820                          * only after active load balance is finished.
6821                          */
6822                         if (!busiest->active_balance) {
6823                                 busiest->active_balance = 1;
6824                                 busiest->push_cpu = this_cpu;
6825                                 active_balance = 1;
6826                         }
6827                         raw_spin_unlock_irqrestore(&busiest->lock, flags);
6828 
6829                         if (active_balance) {
6830                                 stop_one_cpu_nowait(cpu_of(busiest),
6831                                         active_load_balance_cpu_stop, busiest,
6832                                         &busiest->active_balance_work);
6833                         }
6834 
6835                         /*
6836                          * We've kicked active balancing, reset the failure
6837                          * counter.
6838                          */
6839                         sd->nr_balance_failed = sd->cache_nice_tries+1;
6840                 }
6841         } else
6842                 sd->nr_balance_failed = 0;
6843 
6844         if (likely(!active_balance)) {
6845                 /* We were unbalanced, so reset the balancing interval */
6846                 sd->balance_interval = sd->min_interval;
6847         } else {
6848                 /*
6849                  * If we've begun active balancing, start to back off. This
6850                  * case may not be covered by the all_pinned logic if there
6851                  * is only 1 task on the busy runqueue (because we don't call
6852                  * detach_tasks).
6853                  */
6854                 if (sd->balance_interval < sd->max_interval)
6855                         sd->balance_interval *= 2;
6856         }
6857 
6858         goto out;
6859 
6860 out_balanced:
6861         /*
6862          * We reach balance although we may have faced some affinity
6863          * constraints. Clear the imbalance flag if it was set.
6864          */
6865         if (sd_parent) {
6866                 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
6867 
6868                 if (*group_imbalance)
6869                         *group_imbalance = 0;
6870         }
6871 
6872 out_all_pinned:
6873         /*
6874          * We reach balance because all tasks are pinned at this level so
6875          * we can't migrate them. Let the imbalance flag set so parent level
6876          * can try to migrate them.
6877          */
6878         schedstat_inc(sd, lb_balanced[idle]);
6879 
6880         sd->nr_balance_failed = 0;
6881 
6882 out_one_pinned:
6883         /* tune up the balancing interval */
6884         if (((env.flags & LBF_ALL_PINNED) &&
6885                         sd->balance_interval < MAX_PINNED_INTERVAL) ||
6886                         (sd->balance_interval < sd->max_interval))
6887                 sd->balance_interval *= 2;
6888 
6889         ld_moved = 0;
6890 out:
6891         return ld_moved;
6892 }
6893 
6894 static inline unsigned long
6895 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
6896 {
6897         unsigned long interval = sd->balance_interval;
6898 
6899         if (cpu_busy)
6900                 interval *= sd->busy_factor;
6901 
6902         /* scale ms to jiffies */
6903         interval = msecs_to_jiffies(interval);
6904         interval = clamp(interval, 1UL, max_load_balance_interval);
6905 
6906         return interval;
6907 }
6908 
6909 static inline void
6910 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
6911 {
6912         unsigned long interval, next;
6913 
6914         interval = get_sd_balance_interval(sd, cpu_busy);
6915         next = sd->last_balance + interval;
6916 
6917         if (time_after(*next_balance, next))
6918                 *next_balance = next;
6919 }
6920 
6921 /*
6922  * idle_balance is called by schedule() if this_cpu is about to become
6923  * idle. Attempts to pull tasks from other CPUs.
6924  */
6925 static int idle_balance(struct rq *this_rq)
6926 {
6927         unsigned long next_balance = jiffies + HZ;
6928         int this_cpu = this_rq->cpu;
6929         struct sched_domain *sd;
6930         int pulled_task = 0;
6931         u64 curr_cost = 0;
6932 
6933         idle_enter_fair(this_rq);
6934 
6935         /*
6936          * We must set idle_stamp _before_ calling idle_balance(), such that we
6937          * measure the duration of idle_balance() as idle time.
6938          */
6939         this_rq->idle_stamp = rq_clock(this_rq);
6940 
6941         if (this_rq->avg_idle < sysctl_sched_migration_cost ||
6942             !this_rq->rd->overload) {
6943                 rcu_read_lock();
6944                 sd = rcu_dereference_check_sched_domain(this_rq->sd);
6945                 if (sd)
6946                         update_next_balance(sd, 0, &next_balance);
6947                 rcu_read_unlock();
6948 
6949                 goto out;
6950         }
6951 
6952         /*
6953          * Drop the rq->lock, but keep IRQ/preempt disabled.
6954          */
6955         raw_spin_unlock(&this_rq->lock);
6956 
6957         update_blocked_averages(this_cpu);
6958         rcu_read_lock();
6959         for_each_domain(this_cpu, sd) {
6960                 int continue_balancing = 1;
6961                 u64 t0, domain_cost;
6962 
6963                 if (!(sd->flags & SD_LOAD_BALANCE))
6964                         continue;
6965 
6966                 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
6967                         update_next_balance(sd, 0, &next_balance);
6968                         break;
6969                 }
6970 
6971                 if (sd->flags & SD_BALANCE_NEWIDLE) {
6972                         t0 = sched_clock_cpu(this_cpu);
6973 
6974                         pulled_task = load_balance(this_cpu, this_rq,
6975                                                    sd, CPU_NEWLY_IDLE,
6976                                                    &continue_balancing);
6977 
6978                         domain_cost = sched_clock_cpu(this_cpu) - t0;
6979                         if (domain_cost > sd->max_newidle_lb_cost)
6980                                 sd->max_newidle_lb_cost = domain_cost;
6981 
6982                         curr_cost += domain_cost;
6983                 }
6984 
6985                 update_next_balance(sd, 0, &next_balance);
6986 
6987                 /*
6988                  * Stop searching for tasks to pull if there are
6989                  * now runnable tasks on this rq.
6990                  */
6991                 if (pulled_task || this_rq->nr_running > 0)
6992                         break;
6993         }
6994         rcu_read_unlock();
6995 
6996         raw_spin_lock(&this_rq->lock);
6997 
6998         if (curr_cost > this_rq->max_idle_balance_cost)
6999                 this_rq->max_idle_balance_cost = curr_cost;
7000 
7001         /*
7002          * While browsing the domains, we released the rq lock, a task could
7003          * have been enqueued in the meantime. Since we're not going idle,
7004          * pretend we pulled a task.
7005          */
7006         if (this_rq->cfs.h_nr_running && !pulled_task)
7007                 pulled_task = 1;
7008 
7009 out:
7010         /* Move the next balance forward */
7011         if (time_after(this_rq->next_balance, next_balance))
7012                 this_rq->next_balance = next_balance;
7013 
7014         /* Is there a task of a high priority class? */
7015         if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7016                 pulled_task = -1;
7017 
7018         if (pulled_task) {
7019                 idle_exit_fair(this_rq);
7020                 this_rq->idle_stamp = 0;
7021         }
7022 
7023         return pulled_task;
7024 }
7025 
7026 /*
7027  * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7028  * running tasks off the busiest CPU onto idle CPUs. It requires at
7029  * least 1 task to be running on each physical CPU where possible, and
7030  * avoids physical / logical imbalances.
7031  */
7032 static int active_load_balance_cpu_stop(void *data)
7033 {
7034         struct rq *busiest_rq = data;
7035         int busiest_cpu = cpu_of(busiest_rq);
7036         int target_cpu = busiest_rq->push_cpu;
7037         struct rq *target_rq = cpu_rq(target_cpu);
7038         struct sched_domain *sd;
7039         struct task_struct *p = NULL;
7040 
7041         raw_spin_lock_irq(&busiest_rq->lock);
7042 
7043         /* make sure the requested cpu hasn't gone down in the meantime */
7044         if (unlikely(busiest_cpu != smp_processor_id() ||
7045                      !busiest_rq->active_balance))
7046                 goto out_unlock;
7047 
7048         /* Is there any task to move? */
7049         if (busiest_rq->nr_running <= 1)
7050                 goto out_unlock;
7051 
7052         /*
7053          * This condition is "impossible", if it occurs
7054          * we need to fix it. Originally reported by
7055          * Bjorn Helgaas on a 128-cpu setup.
7056          */
7057         BUG_ON(busiest_rq == target_rq);
7058 
7059         /* Search for an sd spanning us and the target CPU. */
7060         rcu_read_lock();
7061         for_each_domain(target_cpu, sd) {
7062                 if ((sd->flags & SD_LOAD_BALANCE) &&
7063                     cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7064                                 break;
7065         }
7066 
7067         if (likely(sd)) {
7068                 struct lb_env env = {
7069                         .sd             = sd,
7070                         .dst_cpu        = target_cpu,
7071                         .dst_rq         = target_rq,
7072                         .src_cpu        = busiest_rq->cpu,
7073                         .src_rq         = busiest_rq,
7074                         .idle           = CPU_IDLE,
7075                 };
7076 
7077                 schedstat_inc(sd, alb_count);
7078 
7079                 p = detach_one_task(&env);
7080                 if (p)
7081                         schedstat_inc(sd, alb_pushed);
7082                 else
7083                         schedstat_inc(sd, alb_failed);
7084         }
7085         rcu_read_unlock();
7086 out_unlock:
7087         busiest_rq->active_balance = 0;
7088         raw_spin_unlock(&busiest_rq->lock);
7089 
7090         if (p)
7091                 attach_one_task(target_rq, p);
7092 
7093         local_irq_enable();
7094 
7095         return 0;
7096 }
7097 
7098 static inline int on_null_domain(struct rq *rq)
7099 {
7100         return unlikely(!rcu_dereference_sched(rq->sd));
7101 }
7102 
7103 #ifdef CONFIG_NO_HZ_COMMON
7104 /*
7105  * idle load balancing details
7106  * - When one of the busy CPUs notice that there may be an idle rebalancing
7107  *   needed, they will kick the idle load balancer, which then does idle
7108  *   load balancing for all the idle CPUs.
7109  */
7110 static struct {
7111         cpumask_var_t idle_cpus_mask;
7112         atomic_t nr_cpus;
7113         unsigned long next_balance;     /* in jiffy units */
7114 } nohz ____cacheline_aligned;
7115 
7116 static inline int find_new_ilb(void)
7117 {
7118         int ilb = cpumask_first(nohz.idle_cpus_mask);
7119 
7120         if (ilb < nr_cpu_ids && idle_cpu(ilb))
7121                 return ilb;
7122 
7123         return nr_cpu_ids;
7124 }
7125 
7126 /*
7127  * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7128  * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7129  * CPU (if there is one).
7130  */
7131 static void nohz_balancer_kick(void)
7132 {
7133         int ilb_cpu;
7134 
7135         nohz.next_balance++;
7136 
7137         ilb_cpu = find_new_ilb();
7138 
7139         if (ilb_cpu >= nr_cpu_ids)
7140                 return;
7141 
7142         if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7143                 return;
7144         /*
7145          * Use smp_send_reschedule() instead of resched_cpu().
7146          * This way we generate a sched IPI on the target cpu which
7147          * is idle. And the softirq performing nohz idle load balance
7148          * will be run before returning from the IPI.
7149          */
7150         smp_send_reschedule(ilb_cpu);
7151         return;
7152 }
7153 
7154 static inline void nohz_balance_exit_idle(int cpu)
7155 {
7156         if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7157                 /*
7158                  * Completely isolated CPUs don't ever set, so we must test.
7159                  */
7160                 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7161                         cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7162                         atomic_dec(&nohz.nr_cpus);
7163                 }
7164                 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7165         }
7166 }
7167 
7168 static inline void set_cpu_sd_state_busy(void)
7169 {
7170         struct sched_domain *sd;
7171         int cpu = smp_processor_id();
7172 
7173         rcu_read_lock();
7174         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7175 
7176         if (!sd || !sd->nohz_idle)
7177                 goto unlock;
7178         sd->nohz_idle = 0;
7179 
7180         atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7181 unlock:
7182         rcu_read_unlock();
7183 }
7184 
7185 void set_cpu_sd_state_idle(void)
7186 {
7187         struct sched_domain *sd;
7188         int cpu = smp_processor_id();
7189 
7190         rcu_read_lock();
7191         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7192 
7193         if (!sd || sd->nohz_idle)
7194                 goto unlock;
7195         sd->nohz_idle = 1;
7196 
7197         atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7198 unlock:
7199         rcu_read_unlock();
7200 }
7201 
7202 /*
7203  * This routine will record that the cpu is going idle with tick stopped.
7204  * This info will be used in performing idle load balancing in the future.
7205  */
7206 void nohz_balance_enter_idle(int cpu)
7207 {
7208         /*
7209          * If this cpu is going down, then nothing needs to be done.
7210          */
7211         if (!cpu_active(cpu))
7212                 return;
7213 
7214         if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7215                 return;
7216 
7217         /*
7218          * If we're a completely isolated CPU, we don't play.
7219          */
7220         if (on_null_domain(cpu_rq(cpu)))
7221                 return;
7222 
7223         cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7224         atomic_inc(&nohz.nr_cpus);
7225         set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7226 }
7227 
7228 static int sched_ilb_notifier(struct notifier_block *nfb,
7229                                         unsigned long action, void *hcpu)
7230 {
7231         switch (action & ~CPU_TASKS_FROZEN) {
7232         case CPU_DYING:
7233                 nohz_balance_exit_idle(smp_processor_id());
7234                 return NOTIFY_OK;
7235         default:
7236                 return NOTIFY_DONE;
7237         }
7238 }
7239 #endif
7240 
7241 static DEFINE_SPINLOCK(balancing);
7242 
7243 /*
7244  * Scale the max load_balance interval with the number of CPUs in the system.
7245  * This trades load-balance latency on larger machines for less cross talk.
7246  */
7247 void update_max_interval(void)
7248 {
7249         max_load_balance_interval = HZ*num_online_cpus()/10;
7250 }
7251 
7252 /*
7253  * It checks each scheduling domain to see if it is due to be balanced,
7254  * and initiates a balancing operation if so.
7255  *
7256  * Balancing parameters are set up in init_sched_domains.
7257  */
7258 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7259 {
7260         int continue_balancing = 1;
7261         int cpu = rq->cpu;
7262         unsigned long interval;
7263         struct sched_domain *sd;
7264         /* Earliest time when we have to do rebalance again */
7265         unsigned long next_balance = jiffies + 60*HZ;
7266         int update_next_balance = 0;
7267         int need_serialize, need_decay = 0;
7268         u64 max_cost = 0;
7269 
7270         update_blocked_averages(cpu);
7271 
7272         rcu_read_lock();
7273         for_each_domain(cpu, sd) {
7274                 /*
7275                  * Decay the newidle max times here because this is a regular
7276                  * visit to all the domains. Decay ~1% per second.
7277                  */
7278                 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7279                         sd->max_newidle_lb_cost =
7280                                 (sd->max_newidle_lb_cost * 253) / 256;
7281                         sd->next_decay_max_lb_cost = jiffies + HZ;
7282                         need_decay = 1;
7283                 }
7284                 max_cost += sd->max_newidle_lb_cost;
7285 
7286                 if (!(sd->flags & SD_LOAD_BALANCE))
7287                         continue;
7288 
7289                 /*
7290                  * Stop the load balance at this level. There is another
7291                  * CPU in our sched group which is doing load balancing more
7292                  * actively.
7293                  */
7294                 if (!continue_balancing) {
7295                         if (need_decay)
7296                                 continue;
7297                         break;
7298                 }
7299 
7300                 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7301 
7302                 need_serialize = sd->flags & SD_SERIALIZE;
7303                 if (need_serialize) {
7304                         if (!spin_trylock(&balancing))
7305                                 goto out;
7306                 }
7307 
7308                 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7309                         if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7310                                 /*
7311                                  * The LBF_DST_PINNED logic could have changed
7312                                  * env->dst_cpu, so we can't know our idle
7313                                  * state even if we migrated tasks. Update it.
7314                                  */
7315                                 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7316                         }
7317                         sd->last_balance = jiffies;
7318                         interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7319                 }
7320                 if (need_serialize)
7321                         spin_unlock(&balancing);
7322 out:
7323                 if (time_after(next_balance, sd->last_balance + interval)) {
7324                         next_balance = sd->last_balance + interval;
7325                         update_next_balance = 1;
7326                 }
7327         }
7328         if (need_decay) {
7329                 /*
7330                  * Ensure the rq-wide value also decays but keep it at a
7331                  * reasonable floor to avoid funnies with rq->avg_idle.
7332                  */
7333                 rq->max_idle_balance_cost =
7334                         max((u64)sysctl_sched_migration_cost, max_cost);
7335         }
7336         rcu_read_unlock();
7337 
7338         /*
7339          * next_balance will be updated only when there is a need.
7340          * When the cpu is attached to null domain for ex, it will not be
7341          * updated.
7342          */
7343         if (likely(update_next_balance))
7344                 rq->next_balance = next_balance;
7345 }
7346 
7347 #ifdef CONFIG_NO_HZ_COMMON
7348 /*
7349  * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7350  * rebalancing for all the cpus for whom scheduler ticks are stopped.
7351  */
7352 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7353 {
7354         int this_cpu = this_rq->cpu;
7355         struct rq *rq;
7356         int balance_cpu;
7357 
7358         if (idle != CPU_IDLE ||
7359             !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7360                 goto end;
7361 
7362         for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7363                 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7364                         continue;
7365 
7366                 /*
7367                  * If this cpu gets work to do, stop the load balancing
7368                  * work being done for other cpus. Next load
7369                  * balancing owner will pick it up.
7370                  */
7371                 if (need_resched())
7372                         break;
7373 
7374                 rq = cpu_rq(balance_cpu);
7375 
7376                 /*
7377                  * If time for next balance is due,
7378                  * do the balance.
7379                  */
7380                 if (time_after_eq(jiffies, rq->next_balance)) {
7381                         raw_spin_lock_irq(&rq->lock);
7382                         update_rq_clock(rq);
7383                         update_idle_cpu_load(rq);
7384                         raw_spin_unlock_irq(&rq->lock);
7385                         rebalance_domains(rq, CPU_IDLE);
7386                 }
7387 
7388                 if (time_after(this_rq->next_balance, rq->next_balance))
7389                         this_rq->next_balance = rq->next_balance;
7390         }
7391         nohz.next_balance = this_rq->next_balance;
7392 end:
7393         clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7394 }
7395 
7396 /*
7397  * Current heuristic for kicking the idle load balancer in the presence
7398  * of an idle cpu is the system.
7399  *   - This rq has more than one task.
7400  *   - At any scheduler domain level, this cpu's scheduler group has multiple
7401  *     busy cpu's exceeding the group's capacity.
7402  *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7403  *     domain span are idle.
7404  */
7405 static inline int nohz_kick_needed(struct rq *rq)
7406 {
7407         unsigned long now = jiffies;
7408         struct sched_domain *sd;
7409         struct sched_group_capacity *sgc;
7410         int nr_busy, cpu = rq->cpu;
7411 
7412         if (unlikely(rq->idle_balance))
7413                 return 0;
7414 
7415        /*
7416         * We may be recently in ticked or tickless idle mode. At the first
7417         * busy tick after returning from idle, we will update the busy stats.
7418         */
7419         set_cpu_sd_state_busy();
7420         nohz_balance_exit_idle(cpu);
7421 
7422         /*
7423          * None are in tickless mode and hence no need for NOHZ idle load
7424          * balancing.
7425          */
7426         if (likely(!atomic_read(&nohz.nr_cpus)))
7427                 return 0;
7428 
7429         if (time_before(now, nohz.next_balance))
7430                 return 0;
7431 
7432         if (rq->nr_running >= 2)
7433                 goto need_kick;
7434 
7435         rcu_read_lock();
7436         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7437 
7438         if (sd) {
7439                 sgc = sd->groups->sgc;
7440                 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7441 
7442                 if (nr_busy > 1)
7443                         goto need_kick_unlock;
7444         }
7445 
7446         sd = rcu_dereference(per_cpu(sd_asym, cpu));
7447 
7448         if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7449                                   sched_domain_span(sd)) < cpu))
7450                 goto need_kick_unlock;
7451 
7452         rcu_read_unlock();
7453         return 0;
7454 
7455 need_kick_unlock:
7456         rcu_read_unlock();
7457 need_kick:
7458         return 1;
7459 }
7460 #else
7461 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7462 #endif
7463 
7464 /*
7465  * run_rebalance_domains is triggered when needed from the scheduler tick.
7466  * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7467  */
7468 static void run_rebalance_domains(struct softirq_action *h)
7469 {
7470         struct rq *this_rq = this_rq();
7471         enum cpu_idle_type idle = this_rq->idle_balance ?
7472                                                 CPU_IDLE : CPU_NOT_IDLE;
7473 
7474         rebalance_domains(this_rq, idle);
7475 
7476         /*
7477          * If this cpu has a pending nohz_balance_kick, then do the
7478          * balancing on behalf of the other idle cpus whose ticks are
7479          * stopped.
7480          */
7481         nohz_idle_balance(this_rq, idle);
7482 }
7483 
7484 /*
7485  * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7486  */
7487 void trigger_load_balance(struct rq *rq)
7488 {
7489         /* Don't need to rebalance while attached to NULL domain */
7490         if (unlikely(on_null_domain(rq)))
7491                 return;
7492 
7493         if (time_after_eq(jiffies, rq->next_balance))
7494                 raise_softirq(SCHED_SOFTIRQ);
7495 #ifdef CONFIG_NO_HZ_COMMON
7496         if (nohz_kick_needed(rq))
7497                 nohz_balancer_kick();
7498 #endif
7499 }
7500 
7501 static void rq_online_fair(struct rq *rq)
7502 {
7503         update_sysctl();
7504 
7505         update_runtime_enabled(rq);
7506 }
7507 
7508 static void rq_offline_fair(struct rq *rq)
7509 {
7510         update_sysctl();
7511 
7512         /* Ensure any throttled groups are reachable by pick_next_task */
7513         unthrottle_offline_cfs_rqs(rq);
7514 }
7515 
7516 #endif /* CONFIG_SMP */
7517 
7518 /*
7519  * scheduler tick hitting a task of our scheduling class:
7520  */
7521 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7522 {
7523         struct cfs_rq *cfs_rq;
7524         struct sched_entity *se = &curr->se;
7525 
7526         for_each_sched_entity(se) {
7527                 cfs_rq = cfs_rq_of(se);
7528                 entity_tick(cfs_rq, se, queued);
7529         }
7530 
7531         if (numabalancing_enabled)
7532                 task_tick_numa(rq, curr);
7533 
7534         update_rq_runnable_avg(rq, 1);
7535 }
7536 
7537 /*
7538  * called on fork with the child task as argument from the parent's context
7539  *  - child not yet on the tasklist
7540  *  - preemption disabled
7541  */
7542 static void task_fork_fair(struct task_struct *p)
7543 {
7544         struct cfs_rq *cfs_rq;
7545         struct sched_entity *se = &p->se, *curr;
7546         int this_cpu = smp_processor_id();
7547         struct rq *rq = this_rq();
7548         unsigned long flags;
7549 
7550         raw_spin_lock_irqsave(&rq->lock, flags);
7551 
7552         update_rq_clock(rq);
7553 
7554         cfs_rq = task_cfs_rq(current);
7555         curr = cfs_rq->curr;
7556 
7557         /*
7558          * Not only the cpu but also the task_group of the parent might have
7559          * been changed after parent->se.parent,cfs_rq were copied to
7560          * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7561          * of child point to valid ones.
7562          */
7563         rcu_read_lock();
7564         __set_task_cpu(p, this_cpu);
7565         rcu_read_unlock();
7566 
7567         update_curr(cfs_rq);
7568 
7569         if (curr)
7570                 se->vruntime = curr->vruntime;
7571         place_entity(cfs_rq, se, 1);
7572 
7573         if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7574                 /*
7575                  * Upon rescheduling, sched_class::put_prev_task() will place
7576                  * 'current' within the tree based on its new key value.
7577                  */
7578                 swap(curr->vruntime, se->vruntime);
7579                 resched_curr(rq);
7580         }
7581 
7582         se->vruntime -= cfs_rq->min_vruntime;
7583 
7584         raw_spin_unlock_irqrestore(&rq->lock, flags);
7585 }
7586 
7587 /*
7588  * Priority of the task has changed. Check to see if we preempt
7589  * the current task.
7590  */
7591 static void
7592 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7593 {
7594         if (!task_on_rq_queued(p))
7595                 return;
7596 
7597         /*
7598          * Reschedule if we are currently running on this runqueue and
7599          * our priority decreased, or if we are not currently running on
7600          * this runqueue and our priority is higher than the current's
7601          */
7602         if (rq->curr == p) {
7603                 if (p->prio > oldprio)
7604                         resched_curr(rq);
7605         } else
7606                 check_preempt_curr(rq, p, 0);
7607 }
7608 
7609 static void switched_from_fair(struct rq *rq, struct task_struct *p)
7610 {
7611         struct sched_entity *se = &p->se;
7612         struct cfs_rq *cfs_rq = cfs_rq_of(se);
7613 
7614         /*
7615          * Ensure the task's vruntime is normalized, so that when it's
7616          * switched back to the fair class the enqueue_entity(.flags=0) will
7617          * do the right thing.
7618          *
7619          * If it's queued, then the dequeue_entity(.flags=0) will already
7620          * have normalized the vruntime, if it's !queued, then only when
7621          * the task is sleeping will it still have non-normalized vruntime.
7622          */
7623         if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
7624                 /*
7625                  * Fix up our vruntime so that the current sleep doesn't
7626                  * cause 'unlimited' sleep bonus.
7627                  */
7628                 place_entity(cfs_rq, se, 0);
7629                 se->vruntime -= cfs_rq->min_vruntime;
7630         }
7631 
7632 #ifdef CONFIG_SMP
7633         /*
7634         * Remove our load from contribution when we leave sched_fair
7635         * and ensure we don't carry in an old decay_count if we
7636         * switch back.
7637         */
7638         if (se->avg.decay_count) {
7639                 __synchronize_entity_decay(se);
7640                 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
7641         }
7642 #endif
7643 }
7644 
7645 /*
7646  * We switched to the sched_fair class.
7647  */
7648 static void switched_to_fair(struct rq *rq, struct task_struct *p)
7649 {
7650 #ifdef CONFIG_FAIR_GROUP_SCHED
7651         struct sched_entity *se = &p->se;
7652         /*
7653          * Since the real-depth could have been changed (only FAIR
7654          * class maintain depth value), reset depth properly.
7655          */
7656         se->depth = se->parent ? se->parent->depth + 1 : 0;
7657 #endif
7658         if (!task_on_rq_queued(p))
7659                 return;
7660 
7661         /*
7662          * We were most likely switched from sched_rt, so
7663          * kick off the schedule if running, otherwise just see
7664          * if we can still preempt the current task.
7665          */
7666         if (rq->curr == p)
7667                 resched_curr(rq);
7668         else
7669                 check_preempt_curr(rq, p, 0);
7670 }
7671 
7672 /* Account for a task changing its policy or group.
7673  *
7674  * This routine is mostly called to set cfs_rq->curr field when a task
7675  * migrates between groups/classes.
7676  */
7677 static void set_curr_task_fair(struct rq *rq)
7678 {
7679         struct sched_entity *se = &rq->curr->se;
7680 
7681         for_each_sched_entity(se) {
7682                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7683 
7684                 set_next_entity(cfs_rq, se);
7685                 /* ensure bandwidth has been allocated on our new cfs_rq */
7686                 account_cfs_rq_runtime(cfs_rq, 0);
7687         }
7688 }
7689 
7690 void init_cfs_rq(struct cfs_rq *cfs_rq)
7691 {
7692         cfs_rq->tasks_timeline = RB_ROOT;
7693         cfs_rq->min_vruntime = (u64)(-(1LL << 20));
7694 #ifndef CONFIG_64BIT
7695         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
7696 #endif
7697 #ifdef CONFIG_SMP
7698         atomic64_set(&cfs_rq->decay_counter, 1);
7699         atomic_long_set(&cfs_rq->removed_load, 0);
7700 #endif
7701 }
7702 
7703 #ifdef CONFIG_FAIR_GROUP_SCHED
7704 static void task_move_group_fair(struct task_struct *p, int queued)
7705 {
7706         struct sched_entity *se = &p->se;
7707         struct cfs_rq *cfs_rq;
7708 
7709         /*
7710          * If the task was not on the rq at the time of this cgroup movement
7711          * it must have been asleep, sleeping tasks keep their ->vruntime
7712          * absolute on their old rq until wakeup (needed for the fair sleeper
7713          * bonus in place_entity()).
7714          *
7715          * If it was on the rq, we've just 'preempted' it, which does convert
7716          * ->vruntime to a relative base.
7717          *
7718          * Make sure both cases convert their relative position when migrating
7719          * to another cgroup's rq. This does somewhat interfere with the
7720          * fair sleeper stuff for the first placement, but who cares.
7721          */
7722         /*
7723          * When !queued, vruntime of the task has usually NOT been normalized.
7724          * But there are some cases where it has already been normalized:
7725          *
7726          * - Moving a forked child which is waiting for being woken up by
7727          *   wake_up_new_task().
7728          * - Moving a task which has been woken up by try_to_wake_up() and
7729          *   waiting for actually being woken up by sched_ttwu_pending().
7730          *
7731          * To prevent boost or penalty in the new cfs_rq caused by delta
7732          * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
7733          */
7734         if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
7735                 queued = 1;
7736 
7737         if (!queued)
7738                 se->vruntime -= cfs_rq_of(se)->min_vruntime;
7739         set_task_rq(p, task_cpu(p));
7740         se->depth = se->parent ? se->parent->depth + 1 : 0;
7741         if (!queued) {
7742                 cfs_rq = cfs_rq_of(se);
7743                 se->vruntime += cfs_rq->min_vruntime;
7744 #ifdef CONFIG_SMP
7745                 /*
7746                  * migrate_task_rq_fair() will have removed our previous
7747                  * contribution, but we must synchronize for ongoing future
7748                  * decay.
7749                  */
7750                 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
7751                 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
7752 #endif
7753         }
7754 }
7755 
7756 void free_fair_sched_group(struct task_group *tg)
7757 {
7758         int i;
7759 
7760         destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
7761 
7762         for_each_possible_cpu(i) {
7763                 if (tg->cfs_rq)
7764                         kfree(tg->cfs_rq[i]);
7765                 if (tg->se)
7766                         kfree(tg->se[i]);
7767         }
7768 
7769         kfree(tg->cfs_rq);
7770         kfree(tg->se);
7771 }
7772 
7773 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
7774 {
7775         struct cfs_rq *cfs_rq;
7776         struct sched_entity *se;
7777         int i;
7778 
7779         tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
7780         if (!tg->cfs_rq)
7781                 goto err;
7782         tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
7783         if (!tg->se)
7784                 goto err;
7785 
7786         tg->shares = NICE_0_LOAD;
7787 
7788         init_cfs_bandwidth(tg_cfs_bandwidth(tg));
7789 
7790         for_each_possible_cpu(i) {
7791                 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
7792                                       GFP_KERNEL, cpu_to_node(i));
7793                 if (!cfs_rq)
7794                         goto err;
7795 
7796                 se = kzalloc_node(sizeof(struct sched_entity),
7797                                   GFP_KERNEL, cpu_to_node(i));
7798                 if (!se)
7799                         goto err_free_rq;
7800 
7801                 init_cfs_rq(cfs_rq);
7802                 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
7803         }
7804 
7805         return 1;
7806 
7807 err_free_rq:
7808         kfree(cfs_rq);
7809 err:
7810         return 0;
7811 }
7812 
7813 void unregister_fair_sched_group(struct task_group *tg, int cpu)
7814 {
7815         struct rq *rq = cpu_rq(cpu);
7816         unsigned long flags;
7817 
7818         /*
7819         * Only empty task groups can be destroyed; so we can speculatively
7820         * check on_list without danger of it being re-added.
7821         */
7822         if (!tg->cfs_rq[cpu]->on_list)
7823                 return;
7824 
7825         raw_spin_lock_irqsave(&rq->lock, flags);
7826         list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
7827         raw_spin_unlock_irqrestore(&rq->lock, flags);
7828 }
7829 
7830 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
7831                         struct sched_entity *se, int cpu,
7832                         struct sched_entity *parent)
7833 {
7834         struct rq *rq = cpu_rq(cpu);
7835 
7836         cfs_rq->tg = tg;
7837         cfs_rq->rq = rq;
7838         init_cfs_rq_runtime(cfs_rq);
7839 
7840         tg->cfs_rq[cpu] = cfs_rq;
7841         tg->se[cpu] = se;
7842 
7843         /* se could be NULL for root_task_group */
7844         if (!se)
7845                 return;
7846 
7847         if (!parent) {
7848                 se->cfs_rq = &rq->cfs;
7849                 se->depth = 0;
7850         } else {
7851                 se->cfs_rq = parent->my_q;
7852                 se->depth = parent->depth + 1;
7853         }
7854 
7855         se->my_q = cfs_rq;
7856         /* guarantee group entities always have weight */
7857         update_load_set(&se->load, NICE_0_LOAD);
7858         se->parent = parent;
7859 }
7860 
7861 static DEFINE_MUTEX(shares_mutex);
7862 
7863 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
7864 {
7865         int i;
7866         unsigned long flags;
7867 
7868         /*
7869          * We can't change the weight of the root cgroup.
7870          */
7871         if (!tg->se[0])
7872                 return -EINVAL;
7873 
7874         shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
7875 
7876         mutex_lock(&shares_mutex);
7877         if (tg->shares == shares)
7878                 goto done;
7879 
7880         tg->shares = shares;
7881         for_each_possible_cpu(i) {
7882                 struct rq *rq = cpu_rq(i);
7883                 struct sched_entity *se;
7884 
7885                 se = tg->se[i];
7886                 /* Propagate contribution to hierarchy */
7887                 raw_spin_lock_irqsave(&rq->lock, flags);
7888 
7889                 /* Possible calls to update_curr() need rq clock */
7890                 update_rq_clock(rq);
7891                 for_each_sched_entity(se)
7892                         update_cfs_shares(group_cfs_rq(se));
7893                 raw_spin_unlock_irqrestore(&rq->lock, flags);
7894         }
7895 
7896 done:
7897         mutex_unlock(&shares_mutex);
7898         return 0;
7899 }
7900 #else /* CONFIG_FAIR_GROUP_SCHED */
7901 
7902 void free_fair_sched_group(struct task_group *tg) { }
7903 
7904 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
7905 {
7906         return 1;
7907 }
7908 
7909 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
7910 
7911 #endif /* CONFIG_FAIR_GROUP_SCHED */
7912 
7913 
7914 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
7915 {
7916         struct sched_entity *se = &task->se;
7917         unsigned int rr_interval = 0;
7918 
7919         /*
7920          * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
7921          * idle runqueue:
7922          */
7923         if (rq->cfs.load.weight)
7924                 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
7925 
7926         return rr_interval;
7927 }
7928 
7929 /*
7930  * All the scheduling class methods:
7931  */
7932 const struct sched_class fair_sched_class = {
7933         .next                   = &idle_sched_class,
7934         .enqueue_task           = enqueue_task_fair,
7935         .dequeue_task           = dequeue_task_fair,
7936         .yield_task             = yield_task_fair,
7937         .yield_to_task          = yield_to_task_fair,
7938 
7939         .check_preempt_curr     = check_preempt_wakeup,
7940 
7941         .pick_next_task         = pick_next_task_fair,
7942         .put_prev_task          = put_prev_task_fair,
7943 
7944 #ifdef CONFIG_SMP
7945         .select_task_rq         = select_task_rq_fair,
7946         .migrate_task_rq        = migrate_task_rq_fair,
7947 
7948         .rq_online              = rq_online_fair,
7949         .rq_offline             = rq_offline_fair,
7950 
7951         .task_waking            = task_waking_fair,
7952 #endif
7953 
7954         .set_curr_task          = set_curr_task_fair,
7955         .task_tick              = task_tick_fair,
7956         .task_fork              = task_fork_fair,
7957 
7958         .prio_changed           = prio_changed_fair,
7959         .switched_from          = switched_from_fair,
7960         .switched_to            = switched_to_fair,
7961 
7962         .get_rr_interval        = get_rr_interval_fair,
7963 
7964         .update_curr            = update_curr_fair,
7965 
7966 #ifdef CONFIG_FAIR_GROUP_SCHED
7967         .task_move_group        = task_move_group_fair,
7968 #endif
7969 };
7970 
7971 #ifdef CONFIG_SCHED_DEBUG
7972 void print_cfs_stats(struct seq_file *m, int cpu)
7973 {
7974         struct cfs_rq *cfs_rq;
7975 
7976         rcu_read_lock();
7977         for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
7978                 print_cfs_rq(m, cpu, cfs_rq);
7979         rcu_read_unlock();
7980 }
7981 #endif
7982 
7983 __init void init_sched_fair_class(void)
7984 {
7985 #ifdef CONFIG_SMP
7986         open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
7987 
7988 #ifdef CONFIG_NO_HZ_COMMON
7989         nohz.next_balance = jiffies;
7990         zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
7991         cpu_notifier(sched_ilb_notifier, 0);
7992 #endif
7993 #endif /* SMP */
7994 
7995 }
7996 

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