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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/slab.h>
 27 #include <linux/profile.h>
 28 #include <linux/interrupt.h>
 29 #include <linux/mempolicy.h>
 30 #include <linux/migrate.h>
 31 #include <linux/task_work.h>
 32 
 33 #include <trace/events/sched.h>
 34 
 35 #include "sched.h"
 36 
 37 /*
 38  * Targeted preemption latency for CPU-bound tasks:
 39  * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
 40  *
 41  * NOTE: this latency value is not the same as the concept of
 42  * 'timeslice length' - timeslices in CFS are of variable length
 43  * and have no persistent notion like in traditional, time-slice
 44  * based scheduling concepts.
 45  *
 46  * (to see the precise effective timeslice length of your workload,
 47  *  run vmstat and monitor the context-switches (cs) field)
 48  */
 49 unsigned int sysctl_sched_latency = 6000000ULL;
 50 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
 51 
 52 /*
 53  * The initial- and re-scaling of tunables is configurable
 54  * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 55  *
 56  * Options are:
 57  * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 58  * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 59  * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 60  */
 61 enum sched_tunable_scaling sysctl_sched_tunable_scaling
 62         = SCHED_TUNABLESCALING_LOG;
 63 
 64 /*
 65  * Minimal preemption granularity for CPU-bound tasks:
 66  * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
 67  */
 68 unsigned int sysctl_sched_min_granularity = 750000ULL;
 69 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
 70 
 71 /*
 72  * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 73  */
 74 static unsigned int sched_nr_latency = 8;
 75 
 76 /*
 77  * After fork, child runs first. If set to 0 (default) then
 78  * parent will (try to) run first.
 79  */
 80 unsigned int sysctl_sched_child_runs_first __read_mostly;
 81 
 82 /*
 83  * SCHED_OTHER wake-up granularity.
 84  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
 85  *
 86  * This option delays the preemption effects of decoupled workloads
 87  * and reduces their over-scheduling. Synchronous workloads will still
 88  * have immediate wakeup/sleep latencies.
 89  */
 90 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
 91 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
 92 
 93 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
 94 
 95 /*
 96  * The exponential sliding  window over which load is averaged for shares
 97  * distribution.
 98  * (default: 10msec)
 99  */
100 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
101 
102 #ifdef CONFIG_CFS_BANDWIDTH
103 /*
104  * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
105  * each time a cfs_rq requests quota.
106  *
107  * Note: in the case that the slice exceeds the runtime remaining (either due
108  * to consumption or the quota being specified to be smaller than the slice)
109  * we will always only issue the remaining available time.
110  *
111  * default: 5 msec, units: microseconds
112   */
113 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
114 #endif
115 
116 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
117 {
118         lw->weight += inc;
119         lw->inv_weight = 0;
120 }
121 
122 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
123 {
124         lw->weight -= dec;
125         lw->inv_weight = 0;
126 }
127 
128 static inline void update_load_set(struct load_weight *lw, unsigned long w)
129 {
130         lw->weight = w;
131         lw->inv_weight = 0;
132 }
133 
134 /*
135  * Increase the granularity value when there are more CPUs,
136  * because with more CPUs the 'effective latency' as visible
137  * to users decreases. But the relationship is not linear,
138  * so pick a second-best guess by going with the log2 of the
139  * number of CPUs.
140  *
141  * This idea comes from the SD scheduler of Con Kolivas:
142  */
143 static int get_update_sysctl_factor(void)
144 {
145         unsigned int cpus = min_t(int, num_online_cpus(), 8);
146         unsigned int factor;
147 
148         switch (sysctl_sched_tunable_scaling) {
149         case SCHED_TUNABLESCALING_NONE:
150                 factor = 1;
151                 break;
152         case SCHED_TUNABLESCALING_LINEAR:
153                 factor = cpus;
154                 break;
155         case SCHED_TUNABLESCALING_LOG:
156         default:
157                 factor = 1 + ilog2(cpus);
158                 break;
159         }
160 
161         return factor;
162 }
163 
164 static void update_sysctl(void)
165 {
166         unsigned int factor = get_update_sysctl_factor();
167 
168 #define SET_SYSCTL(name) \
169         (sysctl_##name = (factor) * normalized_sysctl_##name)
170         SET_SYSCTL(sched_min_granularity);
171         SET_SYSCTL(sched_latency);
172         SET_SYSCTL(sched_wakeup_granularity);
173 #undef SET_SYSCTL
174 }
175 
176 void sched_init_granularity(void)
177 {
178         update_sysctl();
179 }
180 
181 #define WMULT_CONST     (~0U)
182 #define WMULT_SHIFT     32
183 
184 static void __update_inv_weight(struct load_weight *lw)
185 {
186         unsigned long w;
187 
188         if (likely(lw->inv_weight))
189                 return;
190 
191         w = scale_load_down(lw->weight);
192 
193         if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
194                 lw->inv_weight = 1;
195         else if (unlikely(!w))
196                 lw->inv_weight = WMULT_CONST;
197         else
198                 lw->inv_weight = WMULT_CONST / w;
199 }
200 
201 /*
202  * delta_exec * weight / lw.weight
203  *   OR
204  * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
205  *
206  * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
207  * we're guaranteed shift stays positive because inv_weight is guaranteed to
208  * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
209  *
210  * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
211  * weight/lw.weight <= 1, and therefore our shift will also be positive.
212  */
213 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
214 {
215         u64 fact = scale_load_down(weight);
216         int shift = WMULT_SHIFT;
217 
218         __update_inv_weight(lw);
219 
220         if (unlikely(fact >> 32)) {
221                 while (fact >> 32) {
222                         fact >>= 1;
223                         shift--;
224                 }
225         }
226 
227         /* hint to use a 32x32->64 mul */
228         fact = (u64)(u32)fact * lw->inv_weight;
229 
230         while (fact >> 32) {
231                 fact >>= 1;
232                 shift--;
233         }
234 
235         return mul_u64_u32_shr(delta_exec, fact, shift);
236 }
237 
238 
239 const struct sched_class fair_sched_class;
240 
241 /**************************************************************
242  * CFS operations on generic schedulable entities:
243  */
244 
245 #ifdef CONFIG_FAIR_GROUP_SCHED
246 
247 /* cpu runqueue to which this cfs_rq is attached */
248 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
249 {
250         return cfs_rq->rq;
251 }
252 
253 /* An entity is a task if it doesn't "own" a runqueue */
254 #define entity_is_task(se)      (!se->my_q)
255 
256 static inline struct task_struct *task_of(struct sched_entity *se)
257 {
258 #ifdef CONFIG_SCHED_DEBUG
259         WARN_ON_ONCE(!entity_is_task(se));
260 #endif
261         return container_of(se, struct task_struct, se);
262 }
263 
264 /* Walk up scheduling entities hierarchy */
265 #define for_each_sched_entity(se) \
266                 for (; se; se = se->parent)
267 
268 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
269 {
270         return p->se.cfs_rq;
271 }
272 
273 /* runqueue on which this entity is (to be) queued */
274 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
275 {
276         return se->cfs_rq;
277 }
278 
279 /* runqueue "owned" by this group */
280 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
281 {
282         return grp->my_q;
283 }
284 
285 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
286                                        int force_update);
287 
288 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
289 {
290         if (!cfs_rq->on_list) {
291                 /*
292                  * Ensure we either appear before our parent (if already
293                  * enqueued) or force our parent to appear after us when it is
294                  * enqueued.  The fact that we always enqueue bottom-up
295                  * reduces this to two cases.
296                  */
297                 if (cfs_rq->tg->parent &&
298                     cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
299                         list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
300                                 &rq_of(cfs_rq)->leaf_cfs_rq_list);
301                 } else {
302                         list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
303                                 &rq_of(cfs_rq)->leaf_cfs_rq_list);
304                 }
305 
306                 cfs_rq->on_list = 1;
307                 /* We should have no load, but we need to update last_decay. */
308                 update_cfs_rq_blocked_load(cfs_rq, 0);
309         }
310 }
311 
312 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
313 {
314         if (cfs_rq->on_list) {
315                 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
316                 cfs_rq->on_list = 0;
317         }
318 }
319 
320 /* Iterate thr' all leaf cfs_rq's on a runqueue */
321 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
322         list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
323 
324 /* Do the two (enqueued) entities belong to the same group ? */
325 static inline struct cfs_rq *
326 is_same_group(struct sched_entity *se, struct sched_entity *pse)
327 {
328         if (se->cfs_rq == pse->cfs_rq)
329                 return se->cfs_rq;
330 
331         return NULL;
332 }
333 
334 static inline struct sched_entity *parent_entity(struct sched_entity *se)
335 {
336         return se->parent;
337 }
338 
339 static void
340 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
341 {
342         int se_depth, pse_depth;
343 
344         /*
345          * preemption test can be made between sibling entities who are in the
346          * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
347          * both tasks until we find their ancestors who are siblings of common
348          * parent.
349          */
350 
351         /* First walk up until both entities are at same depth */
352         se_depth = (*se)->depth;
353         pse_depth = (*pse)->depth;
354 
355         while (se_depth > pse_depth) {
356                 se_depth--;
357                 *se = parent_entity(*se);
358         }
359 
360         while (pse_depth > se_depth) {
361                 pse_depth--;
362                 *pse = parent_entity(*pse);
363         }
364 
365         while (!is_same_group(*se, *pse)) {
366                 *se = parent_entity(*se);
367                 *pse = parent_entity(*pse);
368         }
369 }
370 
371 #else   /* !CONFIG_FAIR_GROUP_SCHED */
372 
373 static inline struct task_struct *task_of(struct sched_entity *se)
374 {
375         return container_of(se, struct task_struct, se);
376 }
377 
378 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
379 {
380         return container_of(cfs_rq, struct rq, cfs);
381 }
382 
383 #define entity_is_task(se)      1
384 
385 #define for_each_sched_entity(se) \
386                 for (; se; se = NULL)
387 
388 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
389 {
390         return &task_rq(p)->cfs;
391 }
392 
393 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
394 {
395         struct task_struct *p = task_of(se);
396         struct rq *rq = task_rq(p);
397 
398         return &rq->cfs;
399 }
400 
401 /* runqueue "owned" by this group */
402 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
403 {
404         return NULL;
405 }
406 
407 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
408 {
409 }
410 
411 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
412 {
413 }
414 
415 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
416                 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
417 
418 static inline struct sched_entity *parent_entity(struct sched_entity *se)
419 {
420         return NULL;
421 }
422 
423 static inline void
424 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
425 {
426 }
427 
428 #endif  /* CONFIG_FAIR_GROUP_SCHED */
429 
430 static __always_inline
431 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
432 
433 /**************************************************************
434  * Scheduling class tree data structure manipulation methods:
435  */
436 
437 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
438 {
439         s64 delta = (s64)(vruntime - max_vruntime);
440         if (delta > 0)
441                 max_vruntime = vruntime;
442 
443         return max_vruntime;
444 }
445 
446 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
447 {
448         s64 delta = (s64)(vruntime - min_vruntime);
449         if (delta < 0)
450                 min_vruntime = vruntime;
451 
452         return min_vruntime;
453 }
454 
455 static inline int entity_before(struct sched_entity *a,
456                                 struct sched_entity *b)
457 {
458         return (s64)(a->vruntime - b->vruntime) < 0;
459 }
460 
461 static void update_min_vruntime(struct cfs_rq *cfs_rq)
462 {
463         u64 vruntime = cfs_rq->min_vruntime;
464 
465         if (cfs_rq->curr)
466                 vruntime = cfs_rq->curr->vruntime;
467 
468         if (cfs_rq->rb_leftmost) {
469                 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
470                                                    struct sched_entity,
471                                                    run_node);
472 
473                 if (!cfs_rq->curr)
474                         vruntime = se->vruntime;
475                 else
476                         vruntime = min_vruntime(vruntime, se->vruntime);
477         }
478 
479         /* ensure we never gain time by being placed backwards. */
480         cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
481 #ifndef CONFIG_64BIT
482         smp_wmb();
483         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
484 #endif
485 }
486 
487 /*
488  * Enqueue an entity into the rb-tree:
489  */
490 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
491 {
492         struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
493         struct rb_node *parent = NULL;
494         struct sched_entity *entry;
495         int leftmost = 1;
496 
497         /*
498          * Find the right place in the rbtree:
499          */
500         while (*link) {
501                 parent = *link;
502                 entry = rb_entry(parent, struct sched_entity, run_node);
503                 /*
504                  * We dont care about collisions. Nodes with
505                  * the same key stay together.
506                  */
507                 if (entity_before(se, entry)) {
508                         link = &parent->rb_left;
509                 } else {
510                         link = &parent->rb_right;
511                         leftmost = 0;
512                 }
513         }
514 
515         /*
516          * Maintain a cache of leftmost tree entries (it is frequently
517          * used):
518          */
519         if (leftmost)
520                 cfs_rq->rb_leftmost = &se->run_node;
521 
522         rb_link_node(&se->run_node, parent, link);
523         rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
524 }
525 
526 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
527 {
528         if (cfs_rq->rb_leftmost == &se->run_node) {
529                 struct rb_node *next_node;
530 
531                 next_node = rb_next(&se->run_node);
532                 cfs_rq->rb_leftmost = next_node;
533         }
534 
535         rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
536 }
537 
538 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
539 {
540         struct rb_node *left = cfs_rq->rb_leftmost;
541 
542         if (!left)
543                 return NULL;
544 
545         return rb_entry(left, struct sched_entity, run_node);
546 }
547 
548 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
549 {
550         struct rb_node *next = rb_next(&se->run_node);
551 
552         if (!next)
553                 return NULL;
554 
555         return rb_entry(next, struct sched_entity, run_node);
556 }
557 
558 #ifdef CONFIG_SCHED_DEBUG
559 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
560 {
561         struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
562 
563         if (!last)
564                 return NULL;
565 
566         return rb_entry(last, struct sched_entity, run_node);
567 }
568 
569 /**************************************************************
570  * Scheduling class statistics methods:
571  */
572 
573 int sched_proc_update_handler(struct ctl_table *table, int write,
574                 void __user *buffer, size_t *lenp,
575                 loff_t *ppos)
576 {
577         int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
578         int factor = get_update_sysctl_factor();
579 
580         if (ret || !write)
581                 return ret;
582 
583         sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
584                                         sysctl_sched_min_granularity);
585 
586 #define WRT_SYSCTL(name) \
587         (normalized_sysctl_##name = sysctl_##name / (factor))
588         WRT_SYSCTL(sched_min_granularity);
589         WRT_SYSCTL(sched_latency);
590         WRT_SYSCTL(sched_wakeup_granularity);
591 #undef WRT_SYSCTL
592 
593         return 0;
594 }
595 #endif
596 
597 /*
598  * delta /= w
599  */
600 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
601 {
602         if (unlikely(se->load.weight != NICE_0_LOAD))
603                 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
604 
605         return delta;
606 }
607 
608 /*
609  * The idea is to set a period in which each task runs once.
610  *
611  * When there are too many tasks (sched_nr_latency) we have to stretch
612  * this period because otherwise the slices get too small.
613  *
614  * p = (nr <= nl) ? l : l*nr/nl
615  */
616 static u64 __sched_period(unsigned long nr_running)
617 {
618         u64 period = sysctl_sched_latency;
619         unsigned long nr_latency = sched_nr_latency;
620 
621         if (unlikely(nr_running > nr_latency)) {
622                 period = sysctl_sched_min_granularity;
623                 period *= nr_running;
624         }
625 
626         return period;
627 }
628 
629 /*
630  * We calculate the wall-time slice from the period by taking a part
631  * proportional to the weight.
632  *
633  * s = p*P[w/rw]
634  */
635 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
636 {
637         u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
638 
639         for_each_sched_entity(se) {
640                 struct load_weight *load;
641                 struct load_weight lw;
642 
643                 cfs_rq = cfs_rq_of(se);
644                 load = &cfs_rq->load;
645 
646                 if (unlikely(!se->on_rq)) {
647                         lw = cfs_rq->load;
648 
649                         update_load_add(&lw, se->load.weight);
650                         load = &lw;
651                 }
652                 slice = __calc_delta(slice, se->load.weight, load);
653         }
654         return slice;
655 }
656 
657 /*
658  * We calculate the vruntime slice of a to-be-inserted task.
659  *
660  * vs = s/w
661  */
662 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
663 {
664         return calc_delta_fair(sched_slice(cfs_rq, se), se);
665 }
666 
667 #ifdef CONFIG_SMP
668 static unsigned long task_h_load(struct task_struct *p);
669 
670 static inline void __update_task_entity_contrib(struct sched_entity *se);
671 
672 /* Give new task start runnable values to heavy its load in infant time */
673 void init_task_runnable_average(struct task_struct *p)
674 {
675         u32 slice;
676 
677         p->se.avg.decay_count = 0;
678         slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
679         p->se.avg.runnable_avg_sum = slice;
680         p->se.avg.runnable_avg_period = slice;
681         __update_task_entity_contrib(&p->se);
682 }
683 #else
684 void init_task_runnable_average(struct task_struct *p)
685 {
686 }
687 #endif
688 
689 /*
690  * Update the current task's runtime statistics.
691  */
692 static void update_curr(struct cfs_rq *cfs_rq)
693 {
694         struct sched_entity *curr = cfs_rq->curr;
695         u64 now = rq_clock_task(rq_of(cfs_rq));
696         u64 delta_exec;
697 
698         if (unlikely(!curr))
699                 return;
700 
701         delta_exec = now - curr->exec_start;
702         if (unlikely((s64)delta_exec <= 0))
703                 return;
704 
705         curr->exec_start = now;
706 
707         schedstat_set(curr->statistics.exec_max,
708                       max(delta_exec, curr->statistics.exec_max));
709 
710         curr->sum_exec_runtime += delta_exec;
711         schedstat_add(cfs_rq, exec_clock, delta_exec);
712 
713         curr->vruntime += calc_delta_fair(delta_exec, curr);
714         update_min_vruntime(cfs_rq);
715 
716         if (entity_is_task(curr)) {
717                 struct task_struct *curtask = task_of(curr);
718 
719                 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
720                 cpuacct_charge(curtask, delta_exec);
721                 account_group_exec_runtime(curtask, delta_exec);
722         }
723 
724         account_cfs_rq_runtime(cfs_rq, delta_exec);
725 }
726 
727 static inline void
728 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
729 {
730         schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
731 }
732 
733 /*
734  * Task is being enqueued - update stats:
735  */
736 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
737 {
738         /*
739          * Are we enqueueing a waiting task? (for current tasks
740          * a dequeue/enqueue event is a NOP)
741          */
742         if (se != cfs_rq->curr)
743                 update_stats_wait_start(cfs_rq, se);
744 }
745 
746 static void
747 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
748 {
749         schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
750                         rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
751         schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
752         schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
753                         rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
754 #ifdef CONFIG_SCHEDSTATS
755         if (entity_is_task(se)) {
756                 trace_sched_stat_wait(task_of(se),
757                         rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
758         }
759 #endif
760         schedstat_set(se->statistics.wait_start, 0);
761 }
762 
763 static inline void
764 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
765 {
766         /*
767          * Mark the end of the wait period if dequeueing a
768          * waiting task:
769          */
770         if (se != cfs_rq->curr)
771                 update_stats_wait_end(cfs_rq, se);
772 }
773 
774 /*
775  * We are picking a new current task - update its stats:
776  */
777 static inline void
778 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
779 {
780         /*
781          * We are starting a new run period:
782          */
783         se->exec_start = rq_clock_task(rq_of(cfs_rq));
784 }
785 
786 /**************************************************
787  * Scheduling class queueing methods:
788  */
789 
790 #ifdef CONFIG_NUMA_BALANCING
791 /*
792  * Approximate time to scan a full NUMA task in ms. The task scan period is
793  * calculated based on the tasks virtual memory size and
794  * numa_balancing_scan_size.
795  */
796 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
797 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
798 
799 /* Portion of address space to scan in MB */
800 unsigned int sysctl_numa_balancing_scan_size = 256;
801 
802 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
803 unsigned int sysctl_numa_balancing_scan_delay = 1000;
804 
805 static unsigned int task_nr_scan_windows(struct task_struct *p)
806 {
807         unsigned long rss = 0;
808         unsigned long nr_scan_pages;
809 
810         /*
811          * Calculations based on RSS as non-present and empty pages are skipped
812          * by the PTE scanner and NUMA hinting faults should be trapped based
813          * on resident pages
814          */
815         nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
816         rss = get_mm_rss(p->mm);
817         if (!rss)
818                 rss = nr_scan_pages;
819 
820         rss = round_up(rss, nr_scan_pages);
821         return rss / nr_scan_pages;
822 }
823 
824 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
825 #define MAX_SCAN_WINDOW 2560
826 
827 static unsigned int task_scan_min(struct task_struct *p)
828 {
829         unsigned int scan, floor;
830         unsigned int windows = 1;
831 
832         if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
833                 windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
834         floor = 1000 / windows;
835 
836         scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
837         return max_t(unsigned int, floor, scan);
838 }
839 
840 static unsigned int task_scan_max(struct task_struct *p)
841 {
842         unsigned int smin = task_scan_min(p);
843         unsigned int smax;
844 
845         /* Watch for min being lower than max due to floor calculations */
846         smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
847         return max(smin, smax);
848 }
849 
850 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
851 {
852         rq->nr_numa_running += (p->numa_preferred_nid != -1);
853         rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
854 }
855 
856 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
857 {
858         rq->nr_numa_running -= (p->numa_preferred_nid != -1);
859         rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
860 }
861 
862 struct numa_group {
863         atomic_t refcount;
864 
865         spinlock_t lock; /* nr_tasks, tasks */
866         int nr_tasks;
867         pid_t gid;
868         struct list_head task_list;
869 
870         struct rcu_head rcu;
871         nodemask_t active_nodes;
872         unsigned long total_faults;
873         /*
874          * Faults_cpu is used to decide whether memory should move
875          * towards the CPU. As a consequence, these stats are weighted
876          * more by CPU use than by memory faults.
877          */
878         unsigned long *faults_cpu;
879         unsigned long faults[0];
880 };
881 
882 /* Shared or private faults. */
883 #define NR_NUMA_HINT_FAULT_TYPES 2
884 
885 /* Memory and CPU locality */
886 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
887 
888 /* Averaged statistics, and temporary buffers. */
889 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
890 
891 pid_t task_numa_group_id(struct task_struct *p)
892 {
893         return p->numa_group ? p->numa_group->gid : 0;
894 }
895 
896 static inline int task_faults_idx(int nid, int priv)
897 {
898         return NR_NUMA_HINT_FAULT_TYPES * nid + priv;
899 }
900 
901 static inline unsigned long task_faults(struct task_struct *p, int nid)
902 {
903         if (!p->numa_faults_memory)
904                 return 0;
905 
906         return p->numa_faults_memory[task_faults_idx(nid, 0)] +
907                 p->numa_faults_memory[task_faults_idx(nid, 1)];
908 }
909 
910 static inline unsigned long group_faults(struct task_struct *p, int nid)
911 {
912         if (!p->numa_group)
913                 return 0;
914 
915         return p->numa_group->faults[task_faults_idx(nid, 0)] +
916                 p->numa_group->faults[task_faults_idx(nid, 1)];
917 }
918 
919 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
920 {
921         return group->faults_cpu[task_faults_idx(nid, 0)] +
922                 group->faults_cpu[task_faults_idx(nid, 1)];
923 }
924 
925 /*
926  * These return the fraction of accesses done by a particular task, or
927  * task group, on a particular numa node.  The group weight is given a
928  * larger multiplier, in order to group tasks together that are almost
929  * evenly spread out between numa nodes.
930  */
931 static inline unsigned long task_weight(struct task_struct *p, int nid)
932 {
933         unsigned long total_faults;
934 
935         if (!p->numa_faults_memory)
936                 return 0;
937 
938         total_faults = p->total_numa_faults;
939 
940         if (!total_faults)
941                 return 0;
942 
943         return 1000 * task_faults(p, nid) / total_faults;
944 }
945 
946 static inline unsigned long group_weight(struct task_struct *p, int nid)
947 {
948         if (!p->numa_group || !p->numa_group->total_faults)
949                 return 0;
950 
951         return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
952 }
953 
954 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
955                                 int src_nid, int dst_cpu)
956 {
957         struct numa_group *ng = p->numa_group;
958         int dst_nid = cpu_to_node(dst_cpu);
959         int last_cpupid, this_cpupid;
960 
961         this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
962 
963         /*
964          * Multi-stage node selection is used in conjunction with a periodic
965          * migration fault to build a temporal task<->page relation. By using
966          * a two-stage filter we remove short/unlikely relations.
967          *
968          * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
969          * a task's usage of a particular page (n_p) per total usage of this
970          * page (n_t) (in a given time-span) to a probability.
971          *
972          * Our periodic faults will sample this probability and getting the
973          * same result twice in a row, given these samples are fully
974          * independent, is then given by P(n)^2, provided our sample period
975          * is sufficiently short compared to the usage pattern.
976          *
977          * This quadric squishes small probabilities, making it less likely we
978          * act on an unlikely task<->page relation.
979          */
980         last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
981         if (!cpupid_pid_unset(last_cpupid) &&
982                                 cpupid_to_nid(last_cpupid) != dst_nid)
983                 return false;
984 
985         /* Always allow migrate on private faults */
986         if (cpupid_match_pid(p, last_cpupid))
987                 return true;
988 
989         /* A shared fault, but p->numa_group has not been set up yet. */
990         if (!ng)
991                 return true;
992 
993         /*
994          * Do not migrate if the destination is not a node that
995          * is actively used by this numa group.
996          */
997         if (!node_isset(dst_nid, ng->active_nodes))
998                 return false;
999 
1000         /*
1001          * Source is a node that is not actively used by this
1002          * numa group, while the destination is. Migrate.
1003          */
1004         if (!node_isset(src_nid, ng->active_nodes))
1005                 return true;
1006 
1007         /*
1008          * Both source and destination are nodes in active
1009          * use by this numa group. Maximize memory bandwidth
1010          * by migrating from more heavily used groups, to less
1011          * heavily used ones, spreading the load around.
1012          * Use a 1/4 hysteresis to avoid spurious page movement.
1013          */
1014         return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1015 }
1016 
1017 static unsigned long weighted_cpuload(const int cpu);
1018 static unsigned long source_load(int cpu, int type);
1019 static unsigned long target_load(int cpu, int type);
1020 static unsigned long capacity_of(int cpu);
1021 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1022 
1023 /* Cached statistics for all CPUs within a node */
1024 struct numa_stats {
1025         unsigned long nr_running;
1026         unsigned long load;
1027 
1028         /* Total compute capacity of CPUs on a node */
1029         unsigned long compute_capacity;
1030 
1031         /* Approximate capacity in terms of runnable tasks on a node */
1032         unsigned long task_capacity;
1033         int has_free_capacity;
1034 };
1035 
1036 /*
1037  * XXX borrowed from update_sg_lb_stats
1038  */
1039 static void update_numa_stats(struct numa_stats *ns, int nid)
1040 {
1041         int cpu, cpus = 0;
1042 
1043         memset(ns, 0, sizeof(*ns));
1044         for_each_cpu(cpu, cpumask_of_node(nid)) {
1045                 struct rq *rq = cpu_rq(cpu);
1046 
1047                 ns->nr_running += rq->nr_running;
1048                 ns->load += weighted_cpuload(cpu);
1049                 ns->compute_capacity += capacity_of(cpu);
1050 
1051                 cpus++;
1052         }
1053 
1054         /*
1055          * If we raced with hotplug and there are no CPUs left in our mask
1056          * the @ns structure is NULL'ed and task_numa_compare() will
1057          * not find this node attractive.
1058          *
1059          * We'll either bail at !has_free_capacity, or we'll detect a huge
1060          * imbalance and bail there.
1061          */
1062         if (!cpus)
1063                 return;
1064 
1065         ns->load = (ns->load * SCHED_CAPACITY_SCALE) / ns->compute_capacity;
1066         ns->task_capacity =
1067                 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE);
1068         ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1069 }
1070 
1071 struct task_numa_env {
1072         struct task_struct *p;
1073 
1074         int src_cpu, src_nid;
1075         int dst_cpu, dst_nid;
1076 
1077         struct numa_stats src_stats, dst_stats;
1078 
1079         int imbalance_pct;
1080 
1081         struct task_struct *best_task;
1082         long best_imp;
1083         int best_cpu;
1084 };
1085 
1086 static void task_numa_assign(struct task_numa_env *env,
1087                              struct task_struct *p, long imp)
1088 {
1089         if (env->best_task)
1090                 put_task_struct(env->best_task);
1091         if (p)
1092                 get_task_struct(p);
1093 
1094         env->best_task = p;
1095         env->best_imp = imp;
1096         env->best_cpu = env->dst_cpu;
1097 }
1098 
1099 static bool load_too_imbalanced(long orig_src_load, long orig_dst_load,
1100                                 long src_load, long dst_load,
1101                                 struct task_numa_env *env)
1102 {
1103         long imb, old_imb;
1104 
1105         /* We care about the slope of the imbalance, not the direction. */
1106         if (dst_load < src_load)
1107                 swap(dst_load, src_load);
1108 
1109         /* Is the difference below the threshold? */
1110         imb = dst_load * 100 - src_load * env->imbalance_pct;
1111         if (imb <= 0)
1112                 return false;
1113 
1114         /*
1115          * The imbalance is above the allowed threshold.
1116          * Compare it with the old imbalance.
1117          */
1118         if (orig_dst_load < orig_src_load)
1119                 swap(orig_dst_load, orig_src_load);
1120 
1121         old_imb = orig_dst_load * 100 - orig_src_load * env->imbalance_pct;
1122 
1123         /* Would this change make things worse? */
1124         return (imb > old_imb);
1125 }
1126 
1127 /*
1128  * This checks if the overall compute and NUMA accesses of the system would
1129  * be improved if the source tasks was migrated to the target dst_cpu taking
1130  * into account that it might be best if task running on the dst_cpu should
1131  * be exchanged with the source task
1132  */
1133 static void task_numa_compare(struct task_numa_env *env,
1134                               long taskimp, long groupimp)
1135 {
1136         struct rq *src_rq = cpu_rq(env->src_cpu);
1137         struct rq *dst_rq = cpu_rq(env->dst_cpu);
1138         struct task_struct *cur;
1139         long orig_src_load, src_load;
1140         long orig_dst_load, dst_load;
1141         long load;
1142         long imp = (groupimp > 0) ? groupimp : taskimp;
1143 
1144         rcu_read_lock();
1145         cur = ACCESS_ONCE(dst_rq->curr);
1146         if (cur->pid == 0) /* idle */
1147                 cur = NULL;
1148 
1149         /*
1150          * "imp" is the fault differential for the source task between the
1151          * source and destination node. Calculate the total differential for
1152          * the source task and potential destination task. The more negative
1153          * the value is, the more rmeote accesses that would be expected to
1154          * be incurred if the tasks were swapped.
1155          */
1156         if (cur) {
1157                 /* Skip this swap candidate if cannot move to the source cpu */
1158                 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1159                         goto unlock;
1160 
1161                 /*
1162                  * If dst and source tasks are in the same NUMA group, or not
1163                  * in any group then look only at task weights.
1164                  */
1165                 if (cur->numa_group == env->p->numa_group) {
1166                         imp = taskimp + task_weight(cur, env->src_nid) -
1167                               task_weight(cur, env->dst_nid);
1168                         /*
1169                          * Add some hysteresis to prevent swapping the
1170                          * tasks within a group over tiny differences.
1171                          */
1172                         if (cur->numa_group)
1173                                 imp -= imp/16;
1174                 } else {
1175                         /*
1176                          * Compare the group weights. If a task is all by
1177                          * itself (not part of a group), use the task weight
1178                          * instead.
1179                          */
1180                         if (env->p->numa_group)
1181                                 imp = groupimp;
1182                         else
1183                                 imp = taskimp;
1184 
1185                         if (cur->numa_group)
1186                                 imp += group_weight(cur, env->src_nid) -
1187                                        group_weight(cur, env->dst_nid);
1188                         else
1189                                 imp += task_weight(cur, env->src_nid) -
1190                                        task_weight(cur, env->dst_nid);
1191                 }
1192         }
1193 
1194         if (imp < env->best_imp)
1195                 goto unlock;
1196 
1197         if (!cur) {
1198                 /* Is there capacity at our destination? */
1199                 if (env->src_stats.has_free_capacity &&
1200                     !env->dst_stats.has_free_capacity)
1201                         goto unlock;
1202 
1203                 goto balance;
1204         }
1205 
1206         /* Balance doesn't matter much if we're running a task per cpu */
1207         if (src_rq->nr_running == 1 && dst_rq->nr_running == 1)
1208                 goto assign;
1209 
1210         /*
1211          * In the overloaded case, try and keep the load balanced.
1212          */
1213 balance:
1214         orig_dst_load = env->dst_stats.load;
1215         orig_src_load = env->src_stats.load;
1216 
1217         /* XXX missing capacity terms */
1218         load = task_h_load(env->p);
1219         dst_load = orig_dst_load + load;
1220         src_load = orig_src_load - load;
1221 
1222         if (cur) {
1223                 load = task_h_load(cur);
1224                 dst_load -= load;
1225                 src_load += load;
1226         }
1227 
1228         if (load_too_imbalanced(orig_src_load, orig_dst_load,
1229                                 src_load, dst_load, env))
1230                 goto unlock;
1231 
1232 assign:
1233         task_numa_assign(env, cur, imp);
1234 unlock:
1235         rcu_read_unlock();
1236 }
1237 
1238 static void task_numa_find_cpu(struct task_numa_env *env,
1239                                 long taskimp, long groupimp)
1240 {
1241         int cpu;
1242 
1243         for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1244                 /* Skip this CPU if the source task cannot migrate */
1245                 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1246                         continue;
1247 
1248                 env->dst_cpu = cpu;
1249                 task_numa_compare(env, taskimp, groupimp);
1250         }
1251 }
1252 
1253 static int task_numa_migrate(struct task_struct *p)
1254 {
1255         struct task_numa_env env = {
1256                 .p = p,
1257 
1258                 .src_cpu = task_cpu(p),
1259                 .src_nid = task_node(p),
1260 
1261                 .imbalance_pct = 112,
1262 
1263                 .best_task = NULL,
1264                 .best_imp = 0,
1265                 .best_cpu = -1
1266         };
1267         struct sched_domain *sd;
1268         unsigned long taskweight, groupweight;
1269         int nid, ret;
1270         long taskimp, groupimp;
1271 
1272         /*
1273          * Pick the lowest SD_NUMA domain, as that would have the smallest
1274          * imbalance and would be the first to start moving tasks about.
1275          *
1276          * And we want to avoid any moving of tasks about, as that would create
1277          * random movement of tasks -- counter the numa conditions we're trying
1278          * to satisfy here.
1279          */
1280         rcu_read_lock();
1281         sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1282         if (sd)
1283                 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1284         rcu_read_unlock();
1285 
1286         /*
1287          * Cpusets can break the scheduler domain tree into smaller
1288          * balance domains, some of which do not cross NUMA boundaries.
1289          * Tasks that are "trapped" in such domains cannot be migrated
1290          * elsewhere, so there is no point in (re)trying.
1291          */
1292         if (unlikely(!sd)) {
1293                 p->numa_preferred_nid = task_node(p);
1294                 return -EINVAL;
1295         }
1296 
1297         taskweight = task_weight(p, env.src_nid);
1298         groupweight = group_weight(p, env.src_nid);
1299         update_numa_stats(&env.src_stats, env.src_nid);
1300         env.dst_nid = p->numa_preferred_nid;
1301         taskimp = task_weight(p, env.dst_nid) - taskweight;
1302         groupimp = group_weight(p, env.dst_nid) - groupweight;
1303         update_numa_stats(&env.dst_stats, env.dst_nid);
1304 
1305         /* If the preferred nid has free capacity, try to use it. */
1306         if (env.dst_stats.has_free_capacity)
1307                 task_numa_find_cpu(&env, taskimp, groupimp);
1308 
1309         /* No space available on the preferred nid. Look elsewhere. */
1310         if (env.best_cpu == -1) {
1311                 for_each_online_node(nid) {
1312                         if (nid == env.src_nid || nid == p->numa_preferred_nid)
1313                                 continue;
1314 
1315                         /* Only consider nodes where both task and groups benefit */
1316                         taskimp = task_weight(p, nid) - taskweight;
1317                         groupimp = group_weight(p, nid) - groupweight;
1318                         if (taskimp < 0 && groupimp < 0)
1319                                 continue;
1320 
1321                         env.dst_nid = nid;
1322                         update_numa_stats(&env.dst_stats, env.dst_nid);
1323                         task_numa_find_cpu(&env, taskimp, groupimp);
1324                 }
1325         }
1326 
1327         /* No better CPU than the current one was found. */
1328         if (env.best_cpu == -1)
1329                 return -EAGAIN;
1330 
1331         /*
1332          * If the task is part of a workload that spans multiple NUMA nodes,
1333          * and is migrating into one of the workload's active nodes, remember
1334          * this node as the task's preferred numa node, so the workload can
1335          * settle down.
1336          * A task that migrated to a second choice node will be better off
1337          * trying for a better one later. Do not set the preferred node here.
1338          */
1339         if (p->numa_group && node_isset(env.dst_nid, p->numa_group->active_nodes))
1340                 sched_setnuma(p, env.dst_nid);
1341 
1342         /*
1343          * Reset the scan period if the task is being rescheduled on an
1344          * alternative node to recheck if the tasks is now properly placed.
1345          */
1346         p->numa_scan_period = task_scan_min(p);
1347 
1348         if (env.best_task == NULL) {
1349                 ret = migrate_task_to(p, env.best_cpu);
1350                 if (ret != 0)
1351                         trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1352                 return ret;
1353         }
1354 
1355         ret = migrate_swap(p, env.best_task);
1356         if (ret != 0)
1357                 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1358         put_task_struct(env.best_task);
1359         return ret;
1360 }
1361 
1362 /* Attempt to migrate a task to a CPU on the preferred node. */
1363 static void numa_migrate_preferred(struct task_struct *p)
1364 {
1365         unsigned long interval = HZ;
1366 
1367         /* This task has no NUMA fault statistics yet */
1368         if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults_memory))
1369                 return;
1370 
1371         /* Periodically retry migrating the task to the preferred node */
1372         interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1373         p->numa_migrate_retry = jiffies + interval;
1374 
1375         /* Success if task is already running on preferred CPU */
1376         if (task_node(p) == p->numa_preferred_nid)
1377                 return;
1378 
1379         /* Otherwise, try migrate to a CPU on the preferred node */
1380         task_numa_migrate(p);
1381 }
1382 
1383 /*
1384  * Find the nodes on which the workload is actively running. We do this by
1385  * tracking the nodes from which NUMA hinting faults are triggered. This can
1386  * be different from the set of nodes where the workload's memory is currently
1387  * located.
1388  *
1389  * The bitmask is used to make smarter decisions on when to do NUMA page
1390  * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1391  * are added when they cause over 6/16 of the maximum number of faults, but
1392  * only removed when they drop below 3/16.
1393  */
1394 static void update_numa_active_node_mask(struct numa_group *numa_group)
1395 {
1396         unsigned long faults, max_faults = 0;
1397         int nid;
1398 
1399         for_each_online_node(nid) {
1400                 faults = group_faults_cpu(numa_group, nid);
1401                 if (faults > max_faults)
1402                         max_faults = faults;
1403         }
1404 
1405         for_each_online_node(nid) {
1406                 faults = group_faults_cpu(numa_group, nid);
1407                 if (!node_isset(nid, numa_group->active_nodes)) {
1408                         if (faults > max_faults * 6 / 16)
1409                                 node_set(nid, numa_group->active_nodes);
1410                 } else if (faults < max_faults * 3 / 16)
1411                         node_clear(nid, numa_group->active_nodes);
1412         }
1413 }
1414 
1415 /*
1416  * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1417  * increments. The more local the fault statistics are, the higher the scan
1418  * period will be for the next scan window. If local/remote ratio is below
1419  * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
1420  * scan period will decrease
1421  */
1422 #define NUMA_PERIOD_SLOTS 10
1423 #define NUMA_PERIOD_THRESHOLD 3
1424 
1425 /*
1426  * Increase the scan period (slow down scanning) if the majority of
1427  * our memory is already on our local node, or if the majority of
1428  * the page accesses are shared with other processes.
1429  * Otherwise, decrease the scan period.
1430  */
1431 static void update_task_scan_period(struct task_struct *p,
1432                         unsigned long shared, unsigned long private)
1433 {
1434         unsigned int period_slot;
1435         int ratio;
1436         int diff;
1437 
1438         unsigned long remote = p->numa_faults_locality[0];
1439         unsigned long local = p->numa_faults_locality[1];
1440 
1441         /*
1442          * If there were no record hinting faults then either the task is
1443          * completely idle or all activity is areas that are not of interest
1444          * to automatic numa balancing. Scan slower
1445          */
1446         if (local + shared == 0) {
1447                 p->numa_scan_period = min(p->numa_scan_period_max,
1448                         p->numa_scan_period << 1);
1449 
1450                 p->mm->numa_next_scan = jiffies +
1451                         msecs_to_jiffies(p->numa_scan_period);
1452 
1453                 return;
1454         }
1455 
1456         /*
1457          * Prepare to scale scan period relative to the current period.
1458          *       == NUMA_PERIOD_THRESHOLD scan period stays the same
1459          *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1460          *       >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1461          */
1462         period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1463         ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1464         if (ratio >= NUMA_PERIOD_THRESHOLD) {
1465                 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1466                 if (!slot)
1467                         slot = 1;
1468                 diff = slot * period_slot;
1469         } else {
1470                 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1471 
1472                 /*
1473                  * Scale scan rate increases based on sharing. There is an
1474                  * inverse relationship between the degree of sharing and
1475                  * the adjustment made to the scanning period. Broadly
1476                  * speaking the intent is that there is little point
1477                  * scanning faster if shared accesses dominate as it may
1478                  * simply bounce migrations uselessly
1479                  */
1480                 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
1481                 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1482         }
1483 
1484         p->numa_scan_period = clamp(p->numa_scan_period + diff,
1485                         task_scan_min(p), task_scan_max(p));
1486         memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1487 }
1488 
1489 /*
1490  * Get the fraction of time the task has been running since the last
1491  * NUMA placement cycle. The scheduler keeps similar statistics, but
1492  * decays those on a 32ms period, which is orders of magnitude off
1493  * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1494  * stats only if the task is so new there are no NUMA statistics yet.
1495  */
1496 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1497 {
1498         u64 runtime, delta, now;
1499         /* Use the start of this time slice to avoid calculations. */
1500         now = p->se.exec_start;
1501         runtime = p->se.sum_exec_runtime;
1502 
1503         if (p->last_task_numa_placement) {
1504                 delta = runtime - p->last_sum_exec_runtime;
1505                 *period = now - p->last_task_numa_placement;
1506         } else {
1507                 delta = p->se.avg.runnable_avg_sum;
1508                 *period = p->se.avg.runnable_avg_period;
1509         }
1510 
1511         p->last_sum_exec_runtime = runtime;
1512         p->last_task_numa_placement = now;
1513 
1514         return delta;
1515 }
1516 
1517 static void task_numa_placement(struct task_struct *p)
1518 {
1519         int seq, nid, max_nid = -1, max_group_nid = -1;
1520         unsigned long max_faults = 0, max_group_faults = 0;
1521         unsigned long fault_types[2] = { 0, 0 };
1522         unsigned long total_faults;
1523         u64 runtime, period;
1524         spinlock_t *group_lock = NULL;
1525 
1526         seq = ACCESS_ONCE(p->mm->numa_scan_seq);
1527         if (p->numa_scan_seq == seq)
1528                 return;
1529         p->numa_scan_seq = seq;
1530         p->numa_scan_period_max = task_scan_max(p);
1531 
1532         total_faults = p->numa_faults_locality[0] +
1533                        p->numa_faults_locality[1];
1534         runtime = numa_get_avg_runtime(p, &period);
1535 
1536         /* If the task is part of a group prevent parallel updates to group stats */
1537         if (p->numa_group) {
1538                 group_lock = &p->numa_group->lock;
1539                 spin_lock_irq(group_lock);
1540         }
1541 
1542         /* Find the node with the highest number of faults */
1543         for_each_online_node(nid) {
1544                 unsigned long faults = 0, group_faults = 0;
1545                 int priv, i;
1546 
1547                 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1548                         long diff, f_diff, f_weight;
1549 
1550                         i = task_faults_idx(nid, priv);
1551 
1552                         /* Decay existing window, copy faults since last scan */
1553                         diff = p->numa_faults_buffer_memory[i] - p->numa_faults_memory[i] / 2;
1554                         fault_types[priv] += p->numa_faults_buffer_memory[i];
1555                         p->numa_faults_buffer_memory[i] = 0;
1556 
1557                         /*
1558                          * Normalize the faults_from, so all tasks in a group
1559                          * count according to CPU use, instead of by the raw
1560                          * number of faults. Tasks with little runtime have
1561                          * little over-all impact on throughput, and thus their
1562                          * faults are less important.
1563                          */
1564                         f_weight = div64_u64(runtime << 16, period + 1);
1565                         f_weight = (f_weight * p->numa_faults_buffer_cpu[i]) /
1566                                    (total_faults + 1);
1567                         f_diff = f_weight - p->numa_faults_cpu[i] / 2;
1568                         p->numa_faults_buffer_cpu[i] = 0;
1569 
1570                         p->numa_faults_memory[i] += diff;
1571                         p->numa_faults_cpu[i] += f_diff;
1572                         faults += p->numa_faults_memory[i];
1573                         p->total_numa_faults += diff;
1574                         if (p->numa_group) {
1575                                 /* safe because we can only change our own group */
1576                                 p->numa_group->faults[i] += diff;
1577                                 p->numa_group->faults_cpu[i] += f_diff;
1578                                 p->numa_group->total_faults += diff;
1579                                 group_faults += p->numa_group->faults[i];
1580                         }
1581                 }
1582 
1583                 if (faults > max_faults) {
1584                         max_faults = faults;
1585                         max_nid = nid;
1586                 }
1587 
1588                 if (group_faults > max_group_faults) {
1589                         max_group_faults = group_faults;
1590                         max_group_nid = nid;
1591                 }
1592         }
1593 
1594         update_task_scan_period(p, fault_types[0], fault_types[1]);
1595 
1596         if (p->numa_group) {
1597                 update_numa_active_node_mask(p->numa_group);
1598                 /*
1599                  * If the preferred task and group nids are different,
1600                  * iterate over the nodes again to find the best place.
1601                  */
1602                 if (max_nid != max_group_nid) {
1603                         unsigned long weight, max_weight = 0;
1604 
1605                         for_each_online_node(nid) {
1606                                 weight = task_weight(p, nid) + group_weight(p, nid);
1607                                 if (weight > max_weight) {
1608                                         max_weight = weight;
1609                                         max_nid = nid;
1610                                 }
1611                         }
1612                 }
1613 
1614                 spin_unlock_irq(group_lock);
1615         }
1616 
1617         /* Preferred node as the node with the most faults */
1618         if (max_faults && max_nid != p->numa_preferred_nid) {
1619                 /* Update the preferred nid and migrate task if possible */
1620                 sched_setnuma(p, max_nid);
1621                 numa_migrate_preferred(p);
1622         }
1623 }
1624 
1625 static inline int get_numa_group(struct numa_group *grp)
1626 {
1627         return atomic_inc_not_zero(&grp->refcount);
1628 }
1629 
1630 static inline void put_numa_group(struct numa_group *grp)
1631 {
1632         if (atomic_dec_and_test(&grp->refcount))
1633                 kfree_rcu(grp, rcu);
1634 }
1635 
1636 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1637                         int *priv)
1638 {
1639         struct numa_group *grp, *my_grp;
1640         struct task_struct *tsk;
1641         bool join = false;
1642         int cpu = cpupid_to_cpu(cpupid);
1643         int i;
1644 
1645         if (unlikely(!p->numa_group)) {
1646                 unsigned int size = sizeof(struct numa_group) +
1647                                     4*nr_node_ids*sizeof(unsigned long);
1648 
1649                 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1650                 if (!grp)
1651                         return;
1652 
1653                 atomic_set(&grp->refcount, 1);
1654                 spin_lock_init(&grp->lock);
1655                 INIT_LIST_HEAD(&grp->task_list);
1656                 grp->gid = p->pid;
1657                 /* Second half of the array tracks nids where faults happen */
1658                 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1659                                                 nr_node_ids;
1660 
1661                 node_set(task_node(current), grp->active_nodes);
1662 
1663                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1664                         grp->faults[i] = p->numa_faults_memory[i];
1665 
1666                 grp->total_faults = p->total_numa_faults;
1667 
1668                 list_add(&p->numa_entry, &grp->task_list);
1669                 grp->nr_tasks++;
1670                 rcu_assign_pointer(p->numa_group, grp);
1671         }
1672 
1673         rcu_read_lock();
1674         tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);
1675 
1676         if (!cpupid_match_pid(tsk, cpupid))
1677                 goto no_join;
1678 
1679         grp = rcu_dereference(tsk->numa_group);
1680         if (!grp)
1681                 goto no_join;
1682 
1683         my_grp = p->numa_group;
1684         if (grp == my_grp)
1685                 goto no_join;
1686 
1687         /*
1688          * Only join the other group if its bigger; if we're the bigger group,
1689          * the other task will join us.
1690          */
1691         if (my_grp->nr_tasks > grp->nr_tasks)
1692                 goto no_join;
1693 
1694         /*
1695          * Tie-break on the grp address.
1696          */
1697         if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1698                 goto no_join;
1699 
1700         /* Always join threads in the same process. */
1701         if (tsk->mm == current->mm)
1702                 join = true;
1703 
1704         /* Simple filter to avoid false positives due to PID collisions */
1705         if (flags & TNF_SHARED)
1706                 join = true;
1707 
1708         /* Update priv based on whether false sharing was detected */
1709         *priv = !join;
1710 
1711         if (join && !get_numa_group(grp))
1712                 goto no_join;
1713 
1714         rcu_read_unlock();
1715 
1716         if (!join)
1717                 return;
1718 
1719         BUG_ON(irqs_disabled());
1720         double_lock_irq(&my_grp->lock, &grp->lock);
1721 
1722         for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
1723                 my_grp->faults[i] -= p->numa_faults_memory[i];
1724                 grp->faults[i] += p->numa_faults_memory[i];
1725         }
1726         my_grp->total_faults -= p->total_numa_faults;
1727         grp->total_faults += p->total_numa_faults;
1728 
1729         list_move(&p->numa_entry, &grp->task_list);
1730         my_grp->nr_tasks--;
1731         grp->nr_tasks++;
1732 
1733         spin_unlock(&my_grp->lock);
1734         spin_unlock_irq(&grp->lock);
1735 
1736         rcu_assign_pointer(p->numa_group, grp);
1737 
1738         put_numa_group(my_grp);
1739         return;
1740 
1741 no_join:
1742         rcu_read_unlock();
1743         return;
1744 }
1745 
1746 void task_numa_free(struct task_struct *p)
1747 {
1748         struct numa_group *grp = p->numa_group;
1749         void *numa_faults = p->numa_faults_memory;
1750         unsigned long flags;
1751         int i;
1752 
1753         if (grp) {
1754                 spin_lock_irqsave(&grp->lock, flags);
1755                 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1756                         grp->faults[i] -= p->numa_faults_memory[i];
1757                 grp->total_faults -= p->total_numa_faults;
1758 
1759                 list_del(&p->numa_entry);
1760                 grp->nr_tasks--;
1761                 spin_unlock_irqrestore(&grp->lock, flags);
1762                 rcu_assign_pointer(p->numa_group, NULL);
1763                 put_numa_group(grp);
1764         }
1765 
1766         p->numa_faults_memory = NULL;
1767         p->numa_faults_buffer_memory = NULL;
1768         p->numa_faults_cpu= NULL;
1769         p->numa_faults_buffer_cpu = NULL;
1770         kfree(numa_faults);
1771 }
1772 
1773 /*
1774  * Got a PROT_NONE fault for a page on @node.
1775  */
1776 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
1777 {
1778         struct task_struct *p = current;
1779         bool migrated = flags & TNF_MIGRATED;
1780         int cpu_node = task_node(current);
1781         int local = !!(flags & TNF_FAULT_LOCAL);
1782         int priv;
1783 
1784         if (!numabalancing_enabled)
1785                 return;
1786 
1787         /* for example, ksmd faulting in a user's mm */
1788         if (!p->mm)
1789                 return;
1790 
1791         /* Do not worry about placement if exiting */
1792         if (p->state == TASK_DEAD)
1793                 return;
1794 
1795         /* Allocate buffer to track faults on a per-node basis */
1796         if (unlikely(!p->numa_faults_memory)) {
1797                 int size = sizeof(*p->numa_faults_memory) *
1798                            NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
1799 
1800                 p->numa_faults_memory = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
1801                 if (!p->numa_faults_memory)
1802                         return;
1803 
1804                 BUG_ON(p->numa_faults_buffer_memory);
1805                 /*
1806                  * The averaged statistics, shared & private, memory & cpu,
1807                  * occupy the first half of the array. The second half of the
1808                  * array is for current counters, which are averaged into the
1809                  * first set by task_numa_placement.
1810                  */
1811                 p->numa_faults_cpu = p->numa_faults_memory + (2 * nr_node_ids);
1812                 p->numa_faults_buffer_memory = p->numa_faults_memory + (4 * nr_node_ids);
1813                 p->numa_faults_buffer_cpu = p->numa_faults_memory + (6 * nr_node_ids);
1814                 p->total_numa_faults = 0;
1815                 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1816         }
1817 
1818         /*
1819          * First accesses are treated as private, otherwise consider accesses
1820          * to be private if the accessing pid has not changed
1821          */
1822         if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
1823                 priv = 1;
1824         } else {
1825                 priv = cpupid_match_pid(p, last_cpupid);
1826                 if (!priv && !(flags & TNF_NO_GROUP))
1827                         task_numa_group(p, last_cpupid, flags, &priv);
1828         }
1829 
1830         /*
1831          * If a workload spans multiple NUMA nodes, a shared fault that
1832          * occurs wholly within the set of nodes that the workload is
1833          * actively using should be counted as local. This allows the
1834          * scan rate to slow down when a workload has settled down.
1835          */
1836         if (!priv && !local && p->numa_group &&
1837                         node_isset(cpu_node, p->numa_group->active_nodes) &&
1838                         node_isset(mem_node, p->numa_group->active_nodes))
1839                 local = 1;
1840 
1841         task_numa_placement(p);
1842 
1843         /*
1844          * Retry task to preferred node migration periodically, in case it
1845          * case it previously failed, or the scheduler moved us.
1846          */
1847         if (time_after(jiffies, p->numa_migrate_retry))
1848                 numa_migrate_preferred(p);
1849 
1850         if (migrated)
1851                 p->numa_pages_migrated += pages;
1852 
1853         p->numa_faults_buffer_memory[task_faults_idx(mem_node, priv)] += pages;
1854         p->numa_faults_buffer_cpu[task_faults_idx(cpu_node, priv)] += pages;
1855         p->numa_faults_locality[local] += pages;
1856 }
1857 
1858 static void reset_ptenuma_scan(struct task_struct *p)
1859 {
1860         ACCESS_ONCE(p->mm->numa_scan_seq)++;
1861         p->mm->numa_scan_offset = 0;
1862 }
1863 
1864 /*
1865  * The expensive part of numa migration is done from task_work context.
1866  * Triggered from task_tick_numa().
1867  */
1868 void task_numa_work(struct callback_head *work)
1869 {
1870         unsigned long migrate, next_scan, now = jiffies;
1871         struct task_struct *p = current;
1872         struct mm_struct *mm = p->mm;
1873         struct vm_area_struct *vma;
1874         unsigned long start, end;
1875         unsigned long nr_pte_updates = 0;
1876         long pages;
1877 
1878         WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
1879 
1880         work->next = work; /* protect against double add */
1881         /*
1882          * Who cares about NUMA placement when they're dying.
1883          *
1884          * NOTE: make sure not to dereference p->mm before this check,
1885          * exit_task_work() happens _after_ exit_mm() so we could be called
1886          * without p->mm even though we still had it when we enqueued this
1887          * work.
1888          */
1889         if (p->flags & PF_EXITING)
1890                 return;
1891 
1892         if (!mm->numa_next_scan) {
1893                 mm->numa_next_scan = now +
1894                         msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
1895         }
1896 
1897         /*
1898          * Enforce maximal scan/migration frequency..
1899          */
1900         migrate = mm->numa_next_scan;
1901         if (time_before(now, migrate))
1902                 return;
1903 
1904         if (p->numa_scan_period == 0) {
1905                 p->numa_scan_period_max = task_scan_max(p);
1906                 p->numa_scan_period = task_scan_min(p);
1907         }
1908 
1909         next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1910         if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
1911                 return;
1912 
1913         /*
1914          * Delay this task enough that another task of this mm will likely win
1915          * the next time around.
1916          */
1917         p->node_stamp += 2 * TICK_NSEC;
1918 
1919         start = mm->numa_scan_offset;
1920         pages = sysctl_numa_balancing_scan_size;
1921         pages <<= 20 - PAGE_SHIFT; /* MB in pages */
1922         if (!pages)
1923                 return;
1924 
1925         down_read(&mm->mmap_sem);
1926         vma = find_vma(mm, start);
1927         if (!vma) {
1928                 reset_ptenuma_scan(p);
1929                 start = 0;
1930                 vma = mm->mmap;
1931         }
1932         for (; vma; vma = vma->vm_next) {
1933                 if (!vma_migratable(vma) || !vma_policy_mof(p, vma))
1934                         continue;
1935 
1936                 /*
1937                  * Shared library pages mapped by multiple processes are not
1938                  * migrated as it is expected they are cache replicated. Avoid
1939                  * hinting faults in read-only file-backed mappings or the vdso
1940                  * as migrating the pages will be of marginal benefit.
1941                  */
1942                 if (!vma->vm_mm ||
1943                     (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
1944                         continue;
1945 
1946                 /*
1947                  * Skip inaccessible VMAs to avoid any confusion between
1948                  * PROT_NONE and NUMA hinting ptes
1949                  */
1950                 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
1951                         continue;
1952 
1953                 do {
1954                         start = max(start, vma->vm_start);
1955                         end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
1956                         end = min(end, vma->vm_end);
1957                         nr_pte_updates += change_prot_numa(vma, start, end);
1958 
1959                         /*
1960                          * Scan sysctl_numa_balancing_scan_size but ensure that
1961                          * at least one PTE is updated so that unused virtual
1962                          * address space is quickly skipped.
1963                          */
1964                         if (nr_pte_updates)
1965                                 pages -= (end - start) >> PAGE_SHIFT;
1966 
1967                         start = end;
1968                         if (pages <= 0)
1969                                 goto out;
1970 
1971                         cond_resched();
1972                 } while (end != vma->vm_end);
1973         }
1974 
1975 out:
1976         /*
1977          * It is possible to reach the end of the VMA list but the last few
1978          * VMAs are not guaranteed to the vma_migratable. If they are not, we
1979          * would find the !migratable VMA on the next scan but not reset the
1980          * scanner to the start so check it now.
1981          */
1982         if (vma)
1983                 mm->numa_scan_offset = start;
1984         else
1985                 reset_ptenuma_scan(p);
1986         up_read(&mm->mmap_sem);
1987 }
1988 
1989 /*
1990  * Drive the periodic memory faults..
1991  */
1992 void task_tick_numa(struct rq *rq, struct task_struct *curr)
1993 {
1994         struct callback_head *work = &curr->numa_work;
1995         u64 period, now;
1996 
1997         /*
1998          * We don't care about NUMA placement if we don't have memory.
1999          */
2000         if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2001                 return;
2002 
2003         /*
2004          * Using runtime rather than walltime has the dual advantage that
2005          * we (mostly) drive the selection from busy threads and that the
2006          * task needs to have done some actual work before we bother with
2007          * NUMA placement.
2008          */
2009         now = curr->se.sum_exec_runtime;
2010         period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2011 
2012         if (now - curr->node_stamp > period) {
2013                 if (!curr->node_stamp)
2014                         curr->numa_scan_period = task_scan_min(curr);
2015                 curr->node_stamp += period;
2016 
2017                 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2018                         init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2019                         task_work_add(curr, work, true);
2020                 }
2021         }
2022 }
2023 #else
2024 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2025 {
2026 }
2027 
2028 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2029 {
2030 }
2031 
2032 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2033 {
2034 }
2035 #endif /* CONFIG_NUMA_BALANCING */
2036 
2037 static void
2038 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2039 {
2040         update_load_add(&cfs_rq->load, se->load.weight);
2041         if (!parent_entity(se))
2042                 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2043 #ifdef CONFIG_SMP
2044         if (entity_is_task(se)) {
2045                 struct rq *rq = rq_of(cfs_rq);
2046 
2047                 account_numa_enqueue(rq, task_of(se));
2048                 list_add(&se->group_node, &rq->cfs_tasks);
2049         }
2050 #endif
2051         cfs_rq->nr_running++;
2052 }
2053 
2054 static void
2055 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2056 {
2057         update_load_sub(&cfs_rq->load, se->load.weight);
2058         if (!parent_entity(se))
2059                 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2060         if (entity_is_task(se)) {
2061                 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2062                 list_del_init(&se->group_node);
2063         }
2064         cfs_rq->nr_running--;
2065 }
2066 
2067 #ifdef CONFIG_FAIR_GROUP_SCHED
2068 # ifdef CONFIG_SMP
2069 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2070 {
2071         long tg_weight;
2072 
2073         /*
2074          * Use this CPU's actual weight instead of the last load_contribution
2075          * to gain a more accurate current total weight. See
2076          * update_cfs_rq_load_contribution().
2077          */
2078         tg_weight = atomic_long_read(&tg->load_avg);
2079         tg_weight -= cfs_rq->tg_load_contrib;
2080         tg_weight += cfs_rq->load.weight;
2081 
2082         return tg_weight;
2083 }
2084 
2085 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2086 {
2087         long tg_weight, load, shares;
2088 
2089         tg_weight = calc_tg_weight(tg, cfs_rq);
2090         load = cfs_rq->load.weight;
2091 
2092         shares = (tg->shares * load);
2093         if (tg_weight)
2094                 shares /= tg_weight;
2095 
2096         if (shares < MIN_SHARES)
2097                 shares = MIN_SHARES;
2098         if (shares > tg->shares)
2099                 shares = tg->shares;
2100 
2101         return shares;
2102 }
2103 # else /* CONFIG_SMP */
2104 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2105 {
2106         return tg->shares;
2107 }
2108 # endif /* CONFIG_SMP */
2109 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2110                             unsigned long weight)
2111 {
2112         if (se->on_rq) {
2113                 /* commit outstanding execution time */
2114                 if (cfs_rq->curr == se)
2115                         update_curr(cfs_rq);
2116                 account_entity_dequeue(cfs_rq, se);
2117         }
2118 
2119         update_load_set(&se->load, weight);
2120 
2121         if (se->on_rq)
2122                 account_entity_enqueue(cfs_rq, se);
2123 }
2124 
2125 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2126 
2127 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2128 {
2129         struct task_group *tg;
2130         struct sched_entity *se;
2131         long shares;
2132 
2133         tg = cfs_rq->tg;
2134         se = tg->se[cpu_of(rq_of(cfs_rq))];
2135         if (!se || throttled_hierarchy(cfs_rq))
2136                 return;
2137 #ifndef CONFIG_SMP
2138         if (likely(se->load.weight == tg->shares))
2139                 return;
2140 #endif
2141         shares = calc_cfs_shares(cfs_rq, tg);
2142 
2143         reweight_entity(cfs_rq_of(se), se, shares);
2144 }
2145 #else /* CONFIG_FAIR_GROUP_SCHED */
2146 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2147 {
2148 }
2149 #endif /* CONFIG_FAIR_GROUP_SCHED */
2150 
2151 #ifdef CONFIG_SMP
2152 /*
2153  * We choose a half-life close to 1 scheduling period.
2154  * Note: The tables below are dependent on this value.
2155  */
2156 #define LOAD_AVG_PERIOD 32
2157 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
2158 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
2159 
2160 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2161 static const u32 runnable_avg_yN_inv[] = {
2162         0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2163         0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2164         0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2165         0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2166         0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2167         0x85aac367, 0x82cd8698,
2168 };
2169 
2170 /*
2171  * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
2172  * over-estimates when re-combining.
2173  */
2174 static const u32 runnable_avg_yN_sum[] = {
2175             0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2176          9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2177         17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2178 };
2179 
2180 /*
2181  * Approximate:
2182  *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
2183  */
2184 static __always_inline u64 decay_load(u64 val, u64 n)
2185 {
2186         unsigned int local_n;
2187 
2188         if (!n)
2189                 return val;
2190         else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2191                 return 0;
2192 
2193         /* after bounds checking we can collapse to 32-bit */
2194         local_n = n;
2195 
2196         /*
2197          * As y^PERIOD = 1/2, we can combine
2198          *    y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
2199          * With a look-up table which covers k^n (n<PERIOD)
2200          *
2201          * To achieve constant time decay_load.
2202          */
2203         if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2204                 val >>= local_n / LOAD_AVG_PERIOD;
2205                 local_n %= LOAD_AVG_PERIOD;
2206         }
2207 
2208         val *= runnable_avg_yN_inv[local_n];
2209         /* We don't use SRR here since we always want to round down. */
2210         return val >> 32;
2211 }
2212 
2213 /*
2214  * For updates fully spanning n periods, the contribution to runnable
2215  * average will be: \Sum 1024*y^n
2216  *
2217  * We can compute this reasonably efficiently by combining:
2218  *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
2219  */
2220 static u32 __compute_runnable_contrib(u64 n)
2221 {
2222         u32 contrib = 0;
2223 
2224         if (likely(n <= LOAD_AVG_PERIOD))
2225                 return runnable_avg_yN_sum[n];
2226         else if (unlikely(n >= LOAD_AVG_MAX_N))
2227                 return LOAD_AVG_MAX;
2228 
2229         /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2230         do {
2231                 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2232                 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2233 
2234                 n -= LOAD_AVG_PERIOD;
2235         } while (n > LOAD_AVG_PERIOD);
2236 
2237         contrib = decay_load(contrib, n);
2238         return contrib + runnable_avg_yN_sum[n];
2239 }
2240 
2241 /*
2242  * We can represent the historical contribution to runnable average as the
2243  * coefficients of a geometric series.  To do this we sub-divide our runnable
2244  * history into segments of approximately 1ms (1024us); label the segment that
2245  * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2246  *
2247  * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2248  *      p0            p1           p2
2249  *     (now)       (~1ms ago)  (~2ms ago)
2250  *
2251  * Let u_i denote the fraction of p_i that the entity was runnable.
2252  *
2253  * We then designate the fractions u_i as our co-efficients, yielding the
2254  * following representation of historical load:
2255  *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2256  *
2257  * We choose y based on the with of a reasonably scheduling period, fixing:
2258  *   y^32 = 0.5
2259  *
2260  * This means that the contribution to load ~32ms ago (u_32) will be weighted
2261  * approximately half as much as the contribution to load within the last ms
2262  * (u_0).
2263  *
2264  * When a period "rolls over" and we have new u_0`, multiplying the previous
2265  * sum again by y is sufficient to update:
2266  *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2267  *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2268  */
2269 static __always_inline int __update_entity_runnable_avg(u64 now,
2270                                                         struct sched_avg *sa,
2271                                                         int runnable)
2272 {
2273         u64 delta, periods;
2274         u32 runnable_contrib;
2275         int delta_w, decayed = 0;
2276 
2277         delta = now - sa->last_runnable_update;
2278         /*
2279          * This should only happen when time goes backwards, which it
2280          * unfortunately does during sched clock init when we swap over to TSC.
2281          */
2282         if ((s64)delta < 0) {
2283                 sa->last_runnable_update = now;
2284                 return 0;
2285         }
2286 
2287         /*
2288          * Use 1024ns as the unit of measurement since it's a reasonable
2289          * approximation of 1us and fast to compute.
2290          */
2291         delta >>= 10;
2292         if (!delta)
2293                 return 0;
2294         sa->last_runnable_update = now;
2295 
2296         /* delta_w is the amount already accumulated against our next period */
2297         delta_w = sa->runnable_avg_period % 1024;
2298         if (delta + delta_w >= 1024) {
2299                 /* period roll-over */
2300                 decayed = 1;
2301 
2302                 /*
2303                  * Now that we know we're crossing a period boundary, figure
2304                  * out how much from delta we need to complete the current
2305                  * period and accrue it.
2306                  */
2307                 delta_w = 1024 - delta_w;
2308                 if (runnable)
2309                         sa->runnable_avg_sum += delta_w;
2310                 sa->runnable_avg_period += delta_w;
2311 
2312                 delta -= delta_w;
2313 
2314                 /* Figure out how many additional periods this update spans */
2315                 periods = delta / 1024;
2316                 delta %= 1024;
2317 
2318                 sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
2319                                                   periods + 1);
2320                 sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
2321                                                      periods + 1);
2322 
2323                 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2324                 runnable_contrib = __compute_runnable_contrib(periods);
2325                 if (runnable)
2326                         sa->runnable_avg_sum += runnable_contrib;
2327                 sa->runnable_avg_period += runnable_contrib;
2328         }
2329 
2330         /* Remainder of delta accrued against u_0` */
2331         if (runnable)
2332                 sa->runnable_avg_sum += delta;
2333         sa->runnable_avg_period += delta;
2334 
2335         return decayed;
2336 }
2337 
2338 /* Synchronize an entity's decay with its parenting cfs_rq.*/
2339 static inline u64 __synchronize_entity_decay(struct sched_entity *se)
2340 {
2341         struct cfs_rq *cfs_rq = cfs_rq_of(se);
2342         u64 decays = atomic64_read(&cfs_rq->decay_counter);
2343 
2344         decays -= se->avg.decay_count;
2345         if (!decays)
2346                 return 0;
2347 
2348         se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
2349         se->avg.decay_count = 0;
2350 
2351         return decays;
2352 }
2353 
2354 #ifdef CONFIG_FAIR_GROUP_SCHED
2355 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
2356                                                  int force_update)
2357 {
2358         struct task_group *tg = cfs_rq->tg;
2359         long tg_contrib;
2360 
2361         tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
2362         tg_contrib -= cfs_rq->tg_load_contrib;
2363 
2364         if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
2365                 atomic_long_add(tg_contrib, &tg->load_avg);
2366                 cfs_rq->tg_load_contrib += tg_contrib;
2367         }
2368 }
2369 
2370 /*
2371  * Aggregate cfs_rq runnable averages into an equivalent task_group
2372  * representation for computing load contributions.
2373  */
2374 static inline void __update_tg_runnable_avg(struct sched_avg *sa,
2375                                                   struct cfs_rq *cfs_rq)
2376 {
2377         struct task_group *tg = cfs_rq->tg;
2378         long contrib;
2379 
2380         /* The fraction of a cpu used by this cfs_rq */
2381         contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
2382                           sa->runnable_avg_period + 1);
2383         contrib -= cfs_rq->tg_runnable_contrib;
2384 
2385         if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
2386                 atomic_add(contrib, &tg->runnable_avg);
2387                 cfs_rq->tg_runnable_contrib += contrib;
2388         }
2389 }
2390 
2391 static inline void __update_group_entity_contrib(struct sched_entity *se)
2392 {
2393         struct cfs_rq *cfs_rq = group_cfs_rq(se);
2394         struct task_group *tg = cfs_rq->tg;
2395         int runnable_avg;
2396 
2397         u64 contrib;
2398 
2399         contrib = cfs_rq->tg_load_contrib * tg->shares;
2400         se->avg.load_avg_contrib = div_u64(contrib,
2401                                      atomic_long_read(&tg->load_avg) + 1);
2402 
2403         /*
2404          * For group entities we need to compute a correction term in the case
2405          * that they are consuming <1 cpu so that we would contribute the same
2406          * load as a task of equal weight.
2407          *
2408          * Explicitly co-ordinating this measurement would be expensive, but
2409          * fortunately the sum of each cpus contribution forms a usable
2410          * lower-bound on the true value.
2411          *
2412          * Consider the aggregate of 2 contributions.  Either they are disjoint
2413          * (and the sum represents true value) or they are disjoint and we are
2414          * understating by the aggregate of their overlap.
2415          *
2416          * Extending this to N cpus, for a given overlap, the maximum amount we
2417          * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
2418          * cpus that overlap for this interval and w_i is the interval width.
2419          *
2420          * On a small machine; the first term is well-bounded which bounds the
2421          * total error since w_i is a subset of the period.  Whereas on a
2422          * larger machine, while this first term can be larger, if w_i is the
2423          * of consequential size guaranteed to see n_i*w_i quickly converge to
2424          * our upper bound of 1-cpu.
2425          */
2426         runnable_avg = atomic_read(&tg->runnable_avg);
2427         if (runnable_avg < NICE_0_LOAD) {
2428                 se->avg.load_avg_contrib *= runnable_avg;
2429                 se->avg.load_avg_contrib >>= NICE_0_SHIFT;
2430         }
2431 }
2432 
2433 static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
2434 {
2435         __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
2436         __update_tg_runnable_avg(&rq->avg, &rq->cfs);
2437 }
2438 #else /* CONFIG_FAIR_GROUP_SCHED */
2439 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
2440                                                  int force_update) {}
2441 static inline void __update_tg_runnable_avg(struct sched_avg *sa,
2442                                                   struct cfs_rq *cfs_rq) {}
2443 static inline void __update_group_entity_contrib(struct sched_entity *se) {}
2444 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2445 #endif /* CONFIG_FAIR_GROUP_SCHED */
2446 
2447 static inline void __update_task_entity_contrib(struct sched_entity *se)
2448 {
2449         u32 contrib;
2450 
2451         /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
2452         contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
2453         contrib /= (se->avg.runnable_avg_period + 1);
2454         se->avg.load_avg_contrib = scale_load(contrib);
2455 }
2456 
2457 /* Compute the current contribution to load_avg by se, return any delta */
2458 static long __update_entity_load_avg_contrib(struct sched_entity *se)
2459 {
2460         long old_contrib = se->avg.load_avg_contrib;
2461 
2462         if (entity_is_task(se)) {
2463                 __update_task_entity_contrib(se);
2464         } else {
2465                 __update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
2466                 __update_group_entity_contrib(se);
2467         }
2468 
2469         return se->avg.load_avg_contrib - old_contrib;
2470 }
2471 
2472 static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
2473                                                  long load_contrib)
2474 {
2475         if (likely(load_contrib < cfs_rq->blocked_load_avg))
2476                 cfs_rq->blocked_load_avg -= load_contrib;
2477         else
2478                 cfs_rq->blocked_load_avg = 0;
2479 }
2480 
2481 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2482 
2483 /* Update a sched_entity's runnable average */
2484 static inline void update_entity_load_avg(struct sched_entity *se,
2485                                           int update_cfs_rq)
2486 {
2487         struct cfs_rq *cfs_rq = cfs_rq_of(se);
2488         long contrib_delta;
2489         u64 now;
2490 
2491         /*
2492          * For a group entity we need to use their owned cfs_rq_clock_task() in
2493          * case they are the parent of a throttled hierarchy.
2494          */
2495         if (entity_is_task(se))
2496                 now = cfs_rq_clock_task(cfs_rq);
2497         else
2498                 now = cfs_rq_clock_task(group_cfs_rq(se));
2499 
2500         if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
2501                 return;
2502 
2503         contrib_delta = __update_entity_load_avg_contrib(se);
2504 
2505         if (!update_cfs_rq)
2506                 return;
2507 
2508         if (se->on_rq)
2509                 cfs_rq->runnable_load_avg += contrib_delta;
2510         else
2511                 subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
2512 }
2513 
2514 /*
2515  * Decay the load contributed by all blocked children and account this so that
2516  * their contribution may appropriately discounted when they wake up.
2517  */
2518 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
2519 {
2520         u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
2521         u64 decays;
2522 
2523         decays = now - cfs_rq->last_decay;
2524         if (!decays && !force_update)
2525                 return;
2526 
2527         if (atomic_long_read(&cfs_rq->removed_load)) {
2528                 unsigned long removed_load;
2529                 removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
2530                 subtract_blocked_load_contrib(cfs_rq, removed_load);
2531         }
2532 
2533         if (decays) {
2534                 cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
2535                                                       decays);
2536                 atomic64_add(decays, &cfs_rq->decay_counter);
2537                 cfs_rq->last_decay = now;
2538         }
2539 
2540         __update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
2541 }
2542 
2543 /* Add the load generated by se into cfs_rq's child load-average */
2544 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2545                                                   struct sched_entity *se,
2546                                                   int wakeup)
2547 {
2548         /*
2549          * We track migrations using entity decay_count <= 0, on a wake-up
2550          * migration we use a negative decay count to track the remote decays
2551          * accumulated while sleeping.
2552          *
2553          * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
2554          * are seen by enqueue_entity_load_avg() as a migration with an already
2555          * constructed load_avg_contrib.
2556          */
2557         if (unlikely(se->avg.decay_count <= 0)) {
2558                 se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
2559                 if (se->avg.decay_count) {
2560                         /*
2561                          * In a wake-up migration we have to approximate the
2562                          * time sleeping.  This is because we can't synchronize
2563                          * clock_task between the two cpus, and it is not
2564                          * guaranteed to be read-safe.  Instead, we can
2565                          * approximate this using our carried decays, which are
2566                          * explicitly atomically readable.
2567                          */
2568                         se->avg.last_runnable_update -= (-se->avg.decay_count)
2569                                                         << 20;
2570                         update_entity_load_avg(se, 0);
2571                         /* Indicate that we're now synchronized and on-rq */
2572                         se->avg.decay_count = 0;
2573                 }
2574                 wakeup = 0;
2575         } else {
2576                 __synchronize_entity_decay(se);
2577         }
2578 
2579         /* migrated tasks did not contribute to our blocked load */
2580         if (wakeup) {
2581                 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
2582                 update_entity_load_avg(se, 0);
2583         }
2584 
2585         cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
2586         /* we force update consideration on load-balancer moves */
2587         update_cfs_rq_blocked_load(cfs_rq, !wakeup);
2588 }
2589 
2590 /*
2591  * Remove se's load from this cfs_rq child load-average, if the entity is
2592  * transitioning to a blocked state we track its projected decay using
2593  * blocked_load_avg.
2594  */
2595 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2596                                                   struct sched_entity *se,
2597                                                   int sleep)
2598 {
2599         update_entity_load_avg(se, 1);
2600         /* we force update consideration on load-balancer moves */
2601         update_cfs_rq_blocked_load(cfs_rq, !sleep);
2602 
2603         cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
2604         if (sleep) {
2605                 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
2606                 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
2607         } /* migrations, e.g. sleep=0 leave decay_count == 0 */
2608 }
2609 
2610 /*
2611  * Update the rq's load with the elapsed running time before entering
2612  * idle. if the last scheduled task is not a CFS task, idle_enter will
2613  * be the only way to update the runnable statistic.
2614  */
2615 void idle_enter_fair(struct rq *this_rq)
2616 {
2617         update_rq_runnable_avg(this_rq, 1);
2618 }
2619 
2620 /*
2621  * Update the rq's load with the elapsed idle time before a task is
2622  * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2623  * be the only way to update the runnable statistic.
2624  */
2625 void idle_exit_fair(struct rq *this_rq)
2626 {
2627         update_rq_runnable_avg(this_rq, 0);
2628 }
2629 
2630 static int idle_balance(struct rq *this_rq);
2631 
2632 #else /* CONFIG_SMP */
2633 
2634 static inline void update_entity_load_avg(struct sched_entity *se,
2635                                           int update_cfs_rq) {}
2636 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2637 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2638                                            struct sched_entity *se,
2639                                            int wakeup) {}
2640 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2641                                            struct sched_entity *se,
2642                                            int sleep) {}
2643 static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
2644                                               int force_update) {}
2645 
2646 static inline int idle_balance(struct rq *rq)
2647 {
2648         return 0;
2649 }
2650 
2651 #endif /* CONFIG_SMP */
2652 
2653 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2654 {
2655 #ifdef CONFIG_SCHEDSTATS
2656         struct task_struct *tsk = NULL;
2657 
2658         if (entity_is_task(se))
2659                 tsk = task_of(se);
2660 
2661         if (se->statistics.sleep_start) {
2662                 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2663 
2664                 if ((s64)delta < 0)
2665                         delta = 0;
2666 
2667                 if (unlikely(delta > se->statistics.sleep_max))
2668                         se->statistics.sleep_max = delta;
2669 
2670                 se->statistics.sleep_start = 0;
2671                 se->statistics.sum_sleep_runtime += delta;
2672 
2673                 if (tsk) {
2674                         account_scheduler_latency(tsk, delta >> 10, 1);
2675                         trace_sched_stat_sleep(tsk, delta);
2676                 }
2677         }
2678         if (se->statistics.block_start) {
2679                 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2680 
2681                 if ((s64)delta < 0)
2682                         delta = 0;
2683 
2684                 if (unlikely(delta > se->statistics.block_max))
2685                         se->statistics.block_max = delta;
2686 
2687                 se->statistics.block_start = 0;
2688                 se->statistics.sum_sleep_runtime += delta;
2689 
2690                 if (tsk) {
2691                         if (tsk->in_iowait) {
2692                                 se->statistics.iowait_sum += delta;
2693                                 se->statistics.iowait_count++;
2694                                 trace_sched_stat_iowait(tsk, delta);
2695                         }
2696 
2697                         trace_sched_stat_blocked(tsk, delta);
2698 
2699                         /*
2700                          * Blocking time is in units of nanosecs, so shift by
2701                          * 20 to get a milliseconds-range estimation of the
2702                          * amount of time that the task spent sleeping:
2703                          */
2704                         if (unlikely(prof_on == SLEEP_PROFILING)) {
2705                                 profile_hits(SLEEP_PROFILING,
2706                                                 (void *)get_wchan(tsk),
2707                                                 delta >> 20);
2708                         }
2709                         account_scheduler_latency(tsk, delta >> 10, 0);
2710                 }
2711         }
2712 #endif
2713 }
2714 
2715 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2716 {
2717 #ifdef CONFIG_SCHED_DEBUG
2718         s64 d = se->vruntime - cfs_rq->min_vruntime;
2719 
2720         if (d < 0)
2721                 d = -d;
2722 
2723         if (d > 3*sysctl_sched_latency)
2724                 schedstat_inc(cfs_rq, nr_spread_over);
2725 #endif
2726 }
2727 
2728 static void
2729 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2730 {
2731         u64 vruntime = cfs_rq->min_vruntime;
2732 
2733         /*
2734          * The 'current' period is already promised to the current tasks,
2735          * however the extra weight of the new task will slow them down a
2736          * little, place the new task so that it fits in the slot that
2737          * stays open at the end.
2738          */
2739         if (initial && sched_feat(START_DEBIT))
2740                 vruntime += sched_vslice(cfs_rq, se);
2741 
2742         /* sleeps up to a single latency don't count. */
2743         if (!initial) {
2744                 unsigned long thresh = sysctl_sched_latency;
2745 
2746                 /*
2747                  * Halve their sleep time's effect, to allow
2748                  * for a gentler effect of sleepers:
2749                  */
2750                 if (sched_feat(GENTLE_FAIR_SLEEPERS))
2751                         thresh >>= 1;
2752 
2753                 vruntime -= thresh;
2754         }
2755 
2756         /* ensure we never gain time by being placed backwards. */
2757         se->vruntime = max_vruntime(se->vruntime, vruntime);
2758 }
2759 
2760 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
2761 
2762 static void
2763 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2764 {
2765         /*
2766          * Update the normalized vruntime before updating min_vruntime
2767          * through calling update_curr().
2768          */
2769         if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2770                 se->vruntime += cfs_rq->min_vruntime;
2771 
2772         /*
2773          * Update run-time statistics of the 'current'.
2774          */
2775         update_curr(cfs_rq);
2776         enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
2777         account_entity_enqueue(cfs_rq, se);
2778         update_cfs_shares(cfs_rq);
2779 
2780         if (flags & ENQUEUE_WAKEUP) {
2781                 place_entity(cfs_rq, se, 0);
2782                 enqueue_sleeper(cfs_rq, se);
2783         }
2784 
2785         update_stats_enqueue(cfs_rq, se);
2786         check_spread(cfs_rq, se);
2787         if (se != cfs_rq->curr)
2788                 __enqueue_entity(cfs_rq, se);
2789         se->on_rq = 1;
2790 
2791         if (cfs_rq->nr_running == 1) {
2792                 list_add_leaf_cfs_rq(cfs_rq);
2793                 check_enqueue_throttle(cfs_rq);
2794         }
2795 }
2796 
2797 static void __clear_buddies_last(struct sched_entity *se)
2798 {
2799         for_each_sched_entity(se) {
2800                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2801                 if (cfs_rq->last != se)
2802                         break;
2803 
2804                 cfs_rq->last = NULL;
2805         }
2806 }
2807 
2808 static void __clear_buddies_next(struct sched_entity *se)
2809 {
2810         for_each_sched_entity(se) {
2811                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2812                 if (cfs_rq->next != se)
2813                         break;
2814 
2815                 cfs_rq->next = NULL;
2816         }
2817 }
2818 
2819 static void __clear_buddies_skip(struct sched_entity *se)
2820 {
2821         for_each_sched_entity(se) {
2822                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2823                 if (cfs_rq->skip != se)
2824                         break;
2825 
2826                 cfs_rq->skip = NULL;
2827         }
2828 }
2829 
2830 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
2831 {
2832         if (cfs_rq->last == se)
2833                 __clear_buddies_last(se);
2834 
2835         if (cfs_rq->next == se)
2836                 __clear_buddies_next(se);
2837 
2838         if (cfs_rq->skip == se)
2839                 __clear_buddies_skip(se);
2840 }
2841 
2842 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2843 
2844 static void
2845 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2846 {
2847         /*
2848          * Update run-time statistics of the 'current'.
2849          */
2850         update_curr(cfs_rq);
2851         dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2852 
2853         update_stats_dequeue(cfs_rq, se);
2854         if (flags & DEQUEUE_SLEEP) {
2855 #ifdef CONFIG_SCHEDSTATS
2856                 if (entity_is_task(se)) {
2857                         struct task_struct *tsk = task_of(se);
2858 
2859                         if (tsk->state & TASK_INTERRUPTIBLE)
2860                                 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2861                         if (tsk->state & TASK_UNINTERRUPTIBLE)
2862                                 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2863                 }
2864 #endif
2865         }
2866 
2867         clear_buddies(cfs_rq, se);
2868 
2869         if (se != cfs_rq->curr)
2870                 __dequeue_entity(cfs_rq, se);
2871         se->on_rq = 0;
2872         account_entity_dequeue(cfs_rq, se);
2873 
2874         /*
2875          * Normalize the entity after updating the min_vruntime because the
2876          * update can refer to the ->curr item and we need to reflect this
2877          * movement in our normalized position.
2878          */
2879         if (!(flags & DEQUEUE_SLEEP))
2880                 se->vruntime -= cfs_rq->min_vruntime;
2881 
2882         /* return excess runtime on last dequeue */
2883         return_cfs_rq_runtime(cfs_rq);
2884 
2885         update_min_vruntime(cfs_rq);
2886         update_cfs_shares(cfs_rq);
2887 }
2888 
2889 /*
2890  * Preempt the current task with a newly woken task if needed:
2891  */
2892 static void
2893 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2894 {
2895         unsigned long ideal_runtime, delta_exec;
2896         struct sched_entity *se;
2897         s64 delta;
2898 
2899         ideal_runtime = sched_slice(cfs_rq, curr);
2900         delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2901         if (delta_exec > ideal_runtime) {
2902                 resched_task(rq_of(cfs_rq)->curr);
2903                 /*
2904                  * The current task ran long enough, ensure it doesn't get
2905                  * re-elected due to buddy favours.
2906                  */
2907                 clear_buddies(cfs_rq, curr);
2908                 return;
2909         }
2910 
2911         /*
2912          * Ensure that a task that missed wakeup preemption by a
2913          * narrow margin doesn't have to wait for a full slice.
2914          * This also mitigates buddy induced latencies under load.
2915          */
2916         if (delta_exec < sysctl_sched_min_granularity)
2917                 return;
2918 
2919         se = __pick_first_entity(cfs_rq);
2920         delta = curr->vruntime - se->vruntime;
2921 
2922         if (delta < 0)
2923                 return;
2924 
2925         if (delta > ideal_runtime)
2926                 resched_task(rq_of(cfs_rq)->curr);
2927 }
2928 
2929 static void
2930 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2931 {
2932         /* 'current' is not kept within the tree. */
2933         if (se->on_rq) {
2934                 /*
2935                  * Any task has to be enqueued before it get to execute on
2936                  * a CPU. So account for the time it spent waiting on the
2937                  * runqueue.
2938                  */
2939                 update_stats_wait_end(cfs_rq, se);
2940                 __dequeue_entity(cfs_rq, se);
2941         }
2942 
2943         update_stats_curr_start(cfs_rq, se);
2944         cfs_rq->curr = se;
2945 #ifdef CONFIG_SCHEDSTATS
2946         /*
2947          * Track our maximum slice length, if the CPU's load is at
2948          * least twice that of our own weight (i.e. dont track it
2949          * when there are only lesser-weight tasks around):
2950          */
2951         if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2952                 se->statistics.slice_max = max(se->statistics.slice_max,
2953                         se->sum_exec_runtime - se->prev_sum_exec_runtime);
2954         }
2955 #endif
2956         se->prev_sum_exec_runtime = se->sum_exec_runtime;
2957 }
2958 
2959 static int
2960 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
2961 
2962 /*
2963  * Pick the next process, keeping these things in mind, in this order:
2964  * 1) keep things fair between processes/task groups
2965  * 2) pick the "next" process, since someone really wants that to run
2966  * 3) pick the "last" process, for cache locality
2967  * 4) do not run the "skip" process, if something else is available
2968  */
2969 static struct sched_entity *
2970 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2971 {
2972         struct sched_entity *left = __pick_first_entity(cfs_rq);
2973         struct sched_entity *se;
2974 
2975         /*
2976          * If curr is set we have to see if its left of the leftmost entity
2977          * still in the tree, provided there was anything in the tree at all.
2978          */
2979         if (!left || (curr && entity_before(curr, left)))
2980                 left = curr;
2981 
2982         se = left; /* ideally we run the leftmost entity */
2983 
2984         /*
2985          * Avoid running the skip buddy, if running something else can
2986          * be done without getting too unfair.
2987          */
2988         if (cfs_rq->skip == se) {
2989                 struct sched_entity *second;
2990 
2991                 if (se == curr) {
2992                         second = __pick_first_entity(cfs_rq);
2993                 } else {
2994                         second = __pick_next_entity(se);
2995                         if (!second || (curr && entity_before(curr, second)))
2996                                 second = curr;
2997                 }
2998 
2999                 if (second && wakeup_preempt_entity(second, left) < 1)
3000                         se = second;
3001         }
3002 
3003         /*
3004          * Prefer last buddy, try to return the CPU to a preempted task.
3005          */
3006         if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3007                 se = cfs_rq->last;
3008 
3009         /*
3010          * Someone really wants this to run. If it's not unfair, run it.
3011          */
3012         if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3013                 se = cfs_rq->next;
3014 
3015         clear_buddies(cfs_rq, se);
3016 
3017         return se;
3018 }
3019 
3020 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3021 
3022 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3023 {
3024         /*
3025          * If still on the runqueue then deactivate_task()
3026          * was not called and update_curr() has to be done:
3027          */
3028         if (prev->on_rq)
3029                 update_curr(cfs_rq);
3030 
3031         /* throttle cfs_rqs exceeding runtime */
3032         check_cfs_rq_runtime(cfs_rq);
3033 
3034         check_spread(cfs_rq, prev);
3035         if (prev->on_rq) {
3036                 update_stats_wait_start(cfs_rq, prev);
3037                 /* Put 'current' back into the tree. */
3038                 __enqueue_entity(cfs_rq, prev);
3039                 /* in !on_rq case, update occurred at dequeue */
3040                 update_entity_load_avg(prev, 1);
3041         }
3042         cfs_rq->curr = NULL;
3043 }
3044 
3045 static void
3046 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3047 {
3048         /*
3049          * Update run-time statistics of the 'current'.
3050          */
3051         update_curr(cfs_rq);
3052 
3053         /*
3054          * Ensure that runnable average is periodically updated.
3055          */
3056         update_entity_load_avg(curr, 1);
3057         update_cfs_rq_blocked_load(cfs_rq, 1);
3058         update_cfs_shares(cfs_rq);
3059 
3060 #ifdef CONFIG_SCHED_HRTICK
3061         /*
3062          * queued ticks are scheduled to match the slice, so don't bother
3063          * validating it and just reschedule.
3064          */
3065         if (queued) {
3066                 resched_task(rq_of(cfs_rq)->curr);
3067                 return;
3068         }
3069         /*
3070          * don't let the period tick interfere with the hrtick preemption
3071          */
3072         if (!sched_feat(DOUBLE_TICK) &&
3073                         hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3074                 return;
3075 #endif
3076 
3077         if (cfs_rq->nr_running > 1)
3078                 check_preempt_tick(cfs_rq, curr);
3079 }
3080 
3081 
3082 /**************************************************
3083  * CFS bandwidth control machinery
3084  */
3085 
3086 #ifdef CONFIG_CFS_BANDWIDTH
3087 
3088 #ifdef HAVE_JUMP_LABEL
3089 static struct static_key __cfs_bandwidth_used;
3090 
3091 static inline bool cfs_bandwidth_used(void)
3092 {
3093         return static_key_false(&__cfs_bandwidth_used);
3094 }
3095 
3096 void cfs_bandwidth_usage_inc(void)
3097 {
3098         static_key_slow_inc(&__cfs_bandwidth_used);
3099 }
3100 
3101 void cfs_bandwidth_usage_dec(void)
3102 {
3103         static_key_slow_dec(&__cfs_bandwidth_used);
3104 }
3105 #else /* HAVE_JUMP_LABEL */
3106 static bool cfs_bandwidth_used(void)
3107 {
3108         return true;
3109 }
3110 
3111 void cfs_bandwidth_usage_inc(void) {}
3112 void cfs_bandwidth_usage_dec(void) {}
3113 #endif /* HAVE_JUMP_LABEL */
3114 
3115 /*
3116  * default period for cfs group bandwidth.
3117  * default: 0.1s, units: nanoseconds
3118  */
3119 static inline u64 default_cfs_period(void)
3120 {
3121         return 100000000ULL;
3122 }
3123 
3124 static inline u64 sched_cfs_bandwidth_slice(void)
3125 {
3126         return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3127 }
3128 
3129 /*
3130  * Replenish runtime according to assigned quota and update expiration time.
3131  * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3132  * additional synchronization around rq->lock.
3133  *
3134  * requires cfs_b->lock
3135  */
3136 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3137 {
3138         u64 now;
3139 
3140         if (cfs_b->quota == RUNTIME_INF)
3141                 return;
3142 
3143         now = sched_clock_cpu(smp_processor_id());
3144         cfs_b->runtime = cfs_b->quota;
3145         cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3146 }
3147 
3148 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3149 {
3150         return &tg->cfs_bandwidth;
3151 }
3152 
3153 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3154 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3155 {
3156         if (unlikely(cfs_rq->throttle_count))
3157                 return cfs_rq->throttled_clock_task;
3158 
3159         return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3160 }
3161 
3162 /* returns 0 on failure to allocate runtime */
3163 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3164 {
3165         struct task_group *tg = cfs_rq->tg;
3166         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3167         u64 amount = 0, min_amount, expires;
3168 
3169         /* note: this is a positive sum as runtime_remaining <= 0 */
3170         min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3171 
3172         raw_spin_lock(&cfs_b->lock);
3173         if (cfs_b->quota == RUNTIME_INF)
3174                 amount = min_amount;
3175         else {
3176                 /*
3177                  * If the bandwidth pool has become inactive, then at least one
3178                  * period must have elapsed since the last consumption.
3179                  * Refresh the global state and ensure bandwidth timer becomes
3180                  * active.
3181                  */
3182                 if (!cfs_b->timer_active) {
3183                         __refill_cfs_bandwidth_runtime(cfs_b);
3184                         __start_cfs_bandwidth(cfs_b, false);
3185                 }
3186 
3187                 if (cfs_b->runtime > 0) {
3188                         amount = min(cfs_b->runtime, min_amount);
3189                         cfs_b->runtime -= amount;
3190                         cfs_b->idle = 0;
3191                 }
3192         }
3193         expires = cfs_b->runtime_expires;
3194         raw_spin_unlock(&cfs_b->lock);
3195 
3196         cfs_rq->runtime_remaining += amount;
3197         /*
3198          * we may have advanced our local expiration to account for allowed
3199          * spread between our sched_clock and the one on which runtime was
3200          * issued.
3201          */
3202         if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3203                 cfs_rq->runtime_expires = expires;
3204 
3205         return cfs_rq->runtime_remaining > 0;
3206 }
3207 
3208 /*
3209  * Note: This depends on the synchronization provided by sched_clock and the
3210  * fact that rq->clock snapshots this value.
3211  */
3212 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3213 {
3214         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3215 
3216         /* if the deadline is ahead of our clock, nothing to do */
3217         if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3218                 return;
3219 
3220         if (cfs_rq->runtime_remaining < 0)
3221                 return;
3222 
3223         /*
3224          * If the local deadline has passed we have to consider the
3225          * possibility that our sched_clock is 'fast' and the global deadline
3226          * has not truly expired.
3227          *
3228          * Fortunately we can check determine whether this the case by checking
3229          * whether the global deadline has advanced. It is valid to compare
3230          * cfs_b->runtime_expires without any locks since we only care about
3231          * exact equality, so a partial write will still work.
3232          */
3233 
3234         if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3235                 /* extend local deadline, drift is bounded above by 2 ticks */
3236                 cfs_rq->runtime_expires += TICK_NSEC;
3237         } else {
3238                 /* global deadline is ahead, expiration has passed */
3239                 cfs_rq->runtime_remaining = 0;
3240         }
3241 }
3242 
3243 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3244 {
3245         /* dock delta_exec before expiring quota (as it could span periods) */
3246         cfs_rq->runtime_remaining -= delta_exec;
3247         expire_cfs_rq_runtime(cfs_rq);
3248 
3249         if (likely(cfs_rq->runtime_remaining > 0))
3250                 return;
3251 
3252         /*
3253          * if we're unable to extend our runtime we resched so that the active
3254          * hierarchy can be throttled
3255          */
3256         if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3257                 resched_task(rq_of(cfs_rq)->curr);
3258 }
3259 
3260 static __always_inline
3261 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3262 {
3263         if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3264                 return;
3265 
3266         __account_cfs_rq_runtime(cfs_rq, delta_exec);
3267 }
3268 
3269 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3270 {
3271         return cfs_bandwidth_used() && cfs_rq->throttled;
3272 }
3273 
3274 /* check whether cfs_rq, or any parent, is throttled */
3275 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3276 {
3277         return cfs_bandwidth_used() && cfs_rq->throttle_count;
3278 }
3279 
3280 /*
3281  * Ensure that neither of the group entities corresponding to src_cpu or
3282  * dest_cpu are members of a throttled hierarchy when performing group
3283  * load-balance operations.
3284  */
3285 static inline int throttled_lb_pair(struct task_group *tg,
3286                                     int src_cpu, int dest_cpu)
3287 {
3288         struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3289 
3290         src_cfs_rq = tg->cfs_rq[src_cpu];
3291         dest_cfs_rq = tg->cfs_rq[dest_cpu];
3292 
3293         return throttled_hierarchy(src_cfs_rq) ||
3294                throttled_hierarchy(dest_cfs_rq);
3295 }
3296 
3297 /* updated child weight may affect parent so we have to do this bottom up */
3298 static int tg_unthrottle_up(struct task_group *tg, void *data)
3299 {
3300         struct rq *rq = data;
3301         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3302 
3303         cfs_rq->throttle_count--;
3304 #ifdef CONFIG_SMP
3305         if (!cfs_rq->throttle_count) {
3306                 /* adjust cfs_rq_clock_task() */
3307                 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3308                                              cfs_rq->throttled_clock_task;
3309         }
3310 #endif
3311 
3312         return 0;
3313 }
3314 
3315 static int tg_throttle_down(struct task_group *tg, void *data)
3316 {
3317         struct rq *rq = data;
3318         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3319 
3320         /* group is entering throttled state, stop time */
3321         if (!cfs_rq->throttle_count)
3322                 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3323         cfs_rq->throttle_count++;
3324 
3325         return 0;
3326 }
3327 
3328 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3329 {
3330         struct rq *rq = rq_of(cfs_rq);
3331         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3332         struct sched_entity *se;
3333         long task_delta, dequeue = 1;
3334 
3335         se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3336 
3337         /* freeze hierarchy runnable averages while throttled */
3338         rcu_read_lock();
3339         walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3340         rcu_read_unlock();
3341 
3342         task_delta = cfs_rq->h_nr_running;
3343         for_each_sched_entity(se) {
3344                 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3345                 /* throttled entity or throttle-on-deactivate */
3346                 if (!se->on_rq)
3347                         break;
3348 
3349                 if (dequeue)
3350                         dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3351                 qcfs_rq->h_nr_running -= task_delta;
3352 
3353                 if (qcfs_rq->load.weight)
3354                         dequeue = 0;
3355         }
3356 
3357         if (!se)
3358                 sub_nr_running(rq, task_delta);
3359 
3360         cfs_rq->throttled = 1;
3361         cfs_rq->throttled_clock = rq_clock(rq);
3362         raw_spin_lock(&cfs_b->lock);
3363         list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3364         if (!cfs_b->timer_active)
3365                 __start_cfs_bandwidth(cfs_b, false);
3366         raw_spin_unlock(&cfs_b->lock);
3367 }
3368 
3369 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3370 {
3371         struct rq *rq = rq_of(cfs_rq);
3372         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3373         struct sched_entity *se;
3374         int enqueue = 1;
3375         long task_delta;
3376 
3377         se = cfs_rq->tg->se[cpu_of(rq)];
3378 
3379         cfs_rq->throttled = 0;
3380 
3381         update_rq_clock(rq);
3382 
3383         raw_spin_lock(&cfs_b->lock);
3384         cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3385         list_del_rcu(&cfs_rq->throttled_list);
3386         raw_spin_unlock(&cfs_b->lock);
3387 
3388         /* update hierarchical throttle state */
3389         walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3390 
3391         if (!cfs_rq->load.weight)
3392                 return;
3393 
3394         task_delta = cfs_rq->h_nr_running;
3395         for_each_sched_entity(se) {
3396                 if (se->on_rq)
3397                         enqueue = 0;
3398 
3399                 cfs_rq = cfs_rq_of(se);
3400                 if (enqueue)
3401                         enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3402                 cfs_rq->h_nr_running += task_delta;
3403 
3404                 if (cfs_rq_throttled(cfs_rq))
3405                         break;
3406         }
3407 
3408         if (!se)
3409                 add_nr_running(rq, task_delta);
3410 
3411         /* determine whether we need to wake up potentially idle cpu */
3412         if (rq->curr == rq->idle && rq->cfs.nr_running)
3413                 resched_task(rq->curr);
3414 }
3415 
3416 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3417                 u64 remaining, u64 expires)
3418 {
3419         struct cfs_rq *cfs_rq;
3420         u64 runtime = remaining;
3421 
3422         rcu_read_lock();
3423         list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3424                                 throttled_list) {
3425                 struct rq *rq = rq_of(cfs_rq);
3426 
3427                 raw_spin_lock(&rq->lock);
3428                 if (!cfs_rq_throttled(cfs_rq))
3429                         goto next;
3430 
3431                 runtime = -cfs_rq->runtime_remaining + 1;
3432                 if (runtime > remaining)
3433                         runtime = remaining;
3434                 remaining -= runtime;
3435 
3436                 cfs_rq->runtime_remaining += runtime;
3437                 cfs_rq->runtime_expires = expires;
3438 
3439                 /* we check whether we're throttled above */
3440                 if (cfs_rq->runtime_remaining > 0)
3441                         unthrottle_cfs_rq(cfs_rq);
3442 
3443 next:
3444                 raw_spin_unlock(&rq->lock);
3445 
3446                 if (!remaining)
3447                         break;
3448         }
3449         rcu_read_unlock();
3450 
3451         return remaining;
3452 }
3453 
3454 /*
3455  * Responsible for refilling a task_group's bandwidth and unthrottling its
3456  * cfs_rqs as appropriate. If there has been no activity within the last
3457  * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3458  * used to track this state.
3459  */
3460 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3461 {
3462         u64 runtime, runtime_expires;
3463         int throttled;
3464 
3465         /* no need to continue the timer with no bandwidth constraint */
3466         if (cfs_b->quota == RUNTIME_INF)
3467                 goto out_deactivate;
3468 
3469         throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3470         cfs_b->nr_periods += overrun;
3471 
3472         /*
3473          * idle depends on !throttled (for the case of a large deficit), and if
3474          * we're going inactive then everything else can be deferred
3475          */
3476         if (cfs_b->idle && !throttled)
3477                 goto out_deactivate;
3478 
3479         /*
3480          * if we have relooped after returning idle once, we need to update our
3481          * status as actually running, so that other cpus doing
3482          * __start_cfs_bandwidth will stop trying to cancel us.
3483          */
3484         cfs_b->timer_active = 1;
3485 
3486         __refill_cfs_bandwidth_runtime(cfs_b);
3487 
3488         if (!throttled) {
3489                 /* mark as potentially idle for the upcoming period */
3490                 cfs_b->idle = 1;
3491                 return 0;
3492         }
3493 
3494         /* account preceding periods in which throttling occurred */
3495         cfs_b->nr_throttled += overrun;
3496 
3497         /*
3498          * There are throttled entities so we must first use the new bandwidth
3499          * to unthrottle them before making it generally available.  This
3500          * ensures that all existing debts will be paid before a new cfs_rq is
3501          * allowed to run.
3502          */
3503         runtime = cfs_b->runtime;
3504         runtime_expires = cfs_b->runtime_expires;
3505         cfs_b->runtime = 0;
3506 
3507         /*
3508          * This check is repeated as we are holding onto the new bandwidth
3509          * while we unthrottle.  This can potentially race with an unthrottled
3510          * group trying to acquire new bandwidth from the global pool.
3511          */
3512         while (throttled && runtime > 0) {
3513                 raw_spin_unlock(&cfs_b->lock);
3514                 /* we can't nest cfs_b->lock while distributing bandwidth */
3515                 runtime = distribute_cfs_runtime(cfs_b, runtime,
3516                                                  runtime_expires);
3517                 raw_spin_lock(&cfs_b->lock);
3518 
3519                 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3520         }
3521 
3522         /* return (any) remaining runtime */
3523         cfs_b->runtime = runtime;
3524         /*
3525          * While we are ensured activity in the period following an
3526          * unthrottle, this also covers the case in which the new bandwidth is
3527          * insufficient to cover the existing bandwidth deficit.  (Forcing the
3528          * timer to remain active while there are any throttled entities.)
3529          */
3530         cfs_b->idle = 0;
3531 
3532         return 0;
3533 
3534 out_deactivate:
3535         cfs_b->timer_active = 0;
3536         return 1;
3537 }
3538 
3539 /* a cfs_rq won't donate quota below this amount */
3540 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3541 /* minimum remaining period time to redistribute slack quota */
3542 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3543 /* how long we wait to gather additional slack before distributing */
3544 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3545 
3546 /*
3547  * Are we near the end of the current quota period?
3548  *
3549  * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3550  * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
3551  * migrate_hrtimers, base is never cleared, so we are fine.
3552  */
3553 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3554 {
3555         struct hrtimer *refresh_timer = &cfs_b->period_timer;
3556         u64 remaining;
3557 
3558         /* if the call-back is running a quota refresh is already occurring */
3559         if (hrtimer_callback_running(refresh_timer))
3560                 return 1;
3561 
3562         /* is a quota refresh about to occur? */
3563         remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3564         if (remaining < min_expire)
3565                 return 1;
3566 
3567         return 0;
3568 }
3569 
3570 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3571 {
3572         u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3573 
3574         /* if there's a quota refresh soon don't bother with slack */
3575         if (runtime_refresh_within(cfs_b, min_left))
3576                 return;
3577 
3578         start_bandwidth_timer(&cfs_b->slack_timer,
3579                                 ns_to_ktime(cfs_bandwidth_slack_period));
3580 }
3581 
3582 /* we know any runtime found here is valid as update_curr() precedes return */
3583 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3584 {
3585         struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3586         s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3587 
3588         if (slack_runtime <= 0)
3589                 return;
3590 
3591         raw_spin_lock(&cfs_b->lock);
3592         if (cfs_b->quota != RUNTIME_INF &&
3593             cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3594                 cfs_b->runtime += slack_runtime;
3595 
3596                 /* we are under rq->lock, defer unthrottling using a timer */
3597                 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3598                     !list_empty(&cfs_b->throttled_cfs_rq))
3599                         start_cfs_slack_bandwidth(cfs_b);
3600         }
3601         raw_spin_unlock(&cfs_b->lock);
3602 
3603         /* even if it's not valid for return we don't want to try again */
3604         cfs_rq->runtime_remaining -= slack_runtime;
3605 }
3606 
3607 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3608 {
3609         if (!cfs_bandwidth_used())
3610                 return;
3611 
3612         if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3613                 return;
3614 
3615         __return_cfs_rq_runtime(cfs_rq);
3616 }
3617 
3618 /*
3619  * This is done with a timer (instead of inline with bandwidth return) since
3620  * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3621  */
3622 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3623 {
3624         u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3625         u64 expires;
3626 
3627         /* confirm we're still not at a refresh boundary */
3628         raw_spin_lock(&cfs_b->lock);
3629         if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3630                 raw_spin_unlock(&cfs_b->lock);
3631                 return;
3632         }
3633 
3634         if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
3635                 runtime = cfs_b->runtime;
3636                 cfs_b->runtime = 0;
3637         }
3638         expires = cfs_b->runtime_expires;
3639         raw_spin_unlock(&cfs_b->lock);
3640 
3641         if (!runtime)
3642                 return;
3643 
3644         runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3645 
3646         raw_spin_lock(&cfs_b->lock);
3647         if (expires == cfs_b->runtime_expires)
3648                 cfs_b->runtime = runtime;
3649         raw_spin_unlock(&cfs_b->lock);
3650 }
3651 
3652 /*
3653  * When a group wakes up we want to make sure that its quota is not already
3654  * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3655  * runtime as update_curr() throttling can not not trigger until it's on-rq.
3656  */
3657 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3658 {
3659         if (!cfs_bandwidth_used())
3660                 return;
3661 
3662         /* an active group must be handled by the update_curr()->put() path */
3663         if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3664                 return;
3665 
3666         /* ensure the group is not already throttled */
3667         if (cfs_rq_throttled(cfs_rq))
3668                 return;
3669 
3670         /* update runtime allocation */
3671         account_cfs_rq_runtime(cfs_rq, 0);
3672         if (cfs_rq->runtime_remaining <= 0)
3673                 throttle_cfs_rq(cfs_rq);
3674 }
3675 
3676 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3677 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3678 {
3679         if (!cfs_bandwidth_used())
3680                 return false;
3681 
3682         if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3683                 return false;
3684 
3685         /*
3686          * it's possible for a throttled entity to be forced into a running
3687          * state (e.g. set_curr_task), in this case we're finished.
3688          */
3689         if (cfs_rq_throttled(cfs_rq))
3690                 return true;
3691 
3692         throttle_cfs_rq(cfs_rq);
3693         return true;
3694 }
3695 
3696 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3697 {
3698         struct cfs_bandwidth *cfs_b =
3699                 container_of(timer, struct cfs_bandwidth, slack_timer);
3700         do_sched_cfs_slack_timer(cfs_b);
3701 
3702         return HRTIMER_NORESTART;
3703 }
3704 
3705 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3706 {
3707         struct cfs_bandwidth *cfs_b =
3708                 container_of(timer, struct cfs_bandwidth, period_timer);
3709         ktime_t now;
3710         int overrun;
3711         int idle = 0;
3712 
3713         raw_spin_lock(&cfs_b->lock);
3714         for (;;) {
3715                 now = hrtimer_cb_get_time(timer);
3716                 overrun = hrtimer_forward(timer, now, cfs_b->period);
3717 
3718                 if (!overrun)
3719                         break;
3720 
3721                 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3722         }
3723         raw_spin_unlock(&cfs_b->lock);
3724 
3725         return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3726 }
3727 
3728 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3729 {
3730         raw_spin_lock_init(&cfs_b->lock);
3731         cfs_b->runtime = 0;
3732         cfs_b->quota = RUNTIME_INF;
3733         cfs_b->period = ns_to_ktime(default_cfs_period());
3734 
3735         INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3736         hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3737         cfs_b->period_timer.function = sched_cfs_period_timer;
3738         hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3739         cfs_b->slack_timer.function = sched_cfs_slack_timer;
3740 }
3741 
3742 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3743 {
3744         cfs_rq->runtime_enabled = 0;
3745         INIT_LIST_HEAD(&cfs_rq->throttled_list);
3746 }
3747 
3748 /* requires cfs_b->lock, may release to reprogram timer */
3749 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force)
3750 {
3751         /*
3752          * The timer may be active because we're trying to set a new bandwidth
3753          * period or because we're racing with the tear-down path
3754          * (timer_active==0 becomes visible before the hrtimer call-back
3755          * terminates).  In either case we ensure that it's re-programmed
3756          */
3757         while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
3758                hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
3759                 /* bounce the lock to allow do_sched_cfs_period_timer to run */
3760                 raw_spin_unlock(&cfs_b->lock);
3761                 cpu_relax();
3762                 raw_spin_lock(&cfs_b->lock);
3763                 /* if someone else restarted the timer then we're done */
3764                 if (!force && cfs_b->timer_active)
3765                         return;
3766         }
3767 
3768         cfs_b->timer_active = 1;
3769         start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
3770 }
3771 
3772 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3773 {
3774         hrtimer_cancel(&cfs_b->period_timer);
3775         hrtimer_cancel(&cfs_b->slack_timer);
3776 }
3777 
3778 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3779 {
3780         struct cfs_rq *cfs_rq;
3781 
3782         for_each_leaf_cfs_rq(rq, cfs_rq) {
3783                 if (!cfs_rq->runtime_enabled)
3784                         continue;
3785 
3786                 /*
3787                  * clock_task is not advancing so we just need to make sure
3788                  * there's some valid quota amount
3789                  */
3790                 cfs_rq->runtime_remaining = 1;
3791                 if (cfs_rq_throttled(cfs_rq))
3792                         unthrottle_cfs_rq(cfs_rq);
3793         }
3794 }
3795 
3796 #else /* CONFIG_CFS_BANDWIDTH */
3797 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3798 {
3799         return rq_clock_task(rq_of(cfs_rq));
3800 }
3801 
3802 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
3803 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
3804 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3805 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3806 
3807 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3808 {
3809         return 0;
3810 }
3811 
3812 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3813 {
3814         return 0;
3815 }
3816 
3817 static inline int throttled_lb_pair(struct task_group *tg,
3818                                     int src_cpu, int dest_cpu)
3819 {
3820         return 0;
3821 }
3822 
3823 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
3824 
3825 #ifdef CONFIG_FAIR_GROUP_SCHED
3826 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3827 #endif
3828 
3829 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3830 {
3831         return NULL;
3832 }
3833 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
3834 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
3835 
3836 #endif /* CONFIG_CFS_BANDWIDTH */
3837 
3838 /**************************************************
3839  * CFS operations on tasks:
3840  */
3841 
3842 #ifdef CONFIG_SCHED_HRTICK
3843 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
3844 {
3845         struct sched_entity *se = &p->se;
3846         struct cfs_rq *cfs_rq = cfs_rq_of(se);
3847 
3848         WARN_ON(task_rq(p) != rq);
3849 
3850         if (cfs_rq->nr_running > 1) {
3851                 u64 slice = sched_slice(cfs_rq, se);
3852                 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
3853                 s64 delta = slice - ran;
3854 
3855                 if (delta < 0) {
3856                         if (rq->curr == p)
3857                                 resched_task(p);
3858                         return;
3859                 }
3860 
3861                 /*
3862                  * Don't schedule slices shorter than 10000ns, that just
3863                  * doesn't make sense. Rely on vruntime for fairness.
3864                  */
3865                 if (rq->curr != p)
3866                         delta = max_t(s64, 10000LL, delta);
3867 
3868                 hrtick_start(rq, delta);
3869         }
3870 }
3871 
3872 /*
3873  * called from enqueue/dequeue and updates the hrtick when the
3874  * current task is from our class and nr_running is low enough
3875  * to matter.
3876  */
3877 static void hrtick_update(struct rq *rq)
3878 {
3879         struct task_struct *curr = rq->curr;
3880 
3881         if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3882                 return;
3883 
3884         if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
3885                 hrtick_start_fair(rq, curr);
3886 }
3887 #else /* !CONFIG_SCHED_HRTICK */
3888 static inline void
3889 hrtick_start_fair(struct rq *rq, struct task_struct *p)
3890 {
3891 }
3892 
3893 static inline void hrtick_update(struct rq *rq)
3894 {
3895 }
3896 #endif
3897 
3898 /*
3899  * The enqueue_task method is called before nr_running is
3900  * increased. Here we update the fair scheduling stats and
3901  * then put the task into the rbtree:
3902  */
3903 static void
3904 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3905 {
3906         struct cfs_rq *cfs_rq;
3907         struct sched_entity *se = &p->se;
3908 
3909         for_each_sched_entity(se) {
3910                 if (se->on_rq)
3911                         break;
3912                 cfs_rq = cfs_rq_of(se);
3913                 enqueue_entity(cfs_rq, se, flags);
3914 
3915                 /*
3916                  * end evaluation on encountering a throttled cfs_rq
3917                  *
3918                  * note: in the case of encountering a throttled cfs_rq we will
3919                  * post the final h_nr_running increment below.
3920                 */
3921                 if (cfs_rq_throttled(cfs_rq))
3922                         break;
3923                 cfs_rq->h_nr_running++;
3924 
3925                 flags = ENQUEUE_WAKEUP;
3926         }
3927 
3928         for_each_sched_entity(se) {
3929                 cfs_rq = cfs_rq_of(se);
3930                 cfs_rq->h_nr_running++;
3931 
3932                 if (cfs_rq_throttled(cfs_rq))
3933                         break;
3934 
3935                 update_cfs_shares(cfs_rq);
3936                 update_entity_load_avg(se, 1);
3937         }
3938 
3939         if (!se) {
3940                 update_rq_runnable_avg(rq, rq->nr_running);
3941                 add_nr_running(rq, 1);
3942         }
3943         hrtick_update(rq);
3944 }
3945 
3946 static void set_next_buddy(struct sched_entity *se);
3947 
3948 /*
3949  * The dequeue_task method is called before nr_running is
3950  * decreased. We remove the task from the rbtree and
3951  * update the fair scheduling stats:
3952  */
3953 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3954 {
3955         struct cfs_rq *cfs_rq;
3956         struct sched_entity *se = &p->se;
3957         int task_sleep = flags & DEQUEUE_SLEEP;
3958 
3959         for_each_sched_entity(se) {
3960                 cfs_rq = cfs_rq_of(se);
3961                 dequeue_entity(cfs_rq, se, flags);
3962 
3963                 /*
3964                  * end evaluation on encountering a throttled cfs_rq
3965                  *
3966                  * note: in the case of encountering a throttled cfs_rq we will
3967                  * post the final h_nr_running decrement below.
3968                 */
3969                 if (cfs_rq_throttled(cfs_rq))
3970                         break;
3971                 cfs_rq->h_nr_running--;
3972 
3973                 /* Don't dequeue parent if it has other entities besides us */
3974                 if (cfs_rq->load.weight) {
3975                         /*
3976                          * Bias pick_next to pick a task from this cfs_rq, as
3977                          * p is sleeping when it is within its sched_slice.
3978                          */
3979                         if (task_sleep && parent_entity(se))
3980                                 set_next_buddy(parent_entity(se));
3981 
3982                         /* avoid re-evaluating load for this entity */
3983                         se = parent_entity(se);
3984                         break;
3985                 }
3986                 flags |= DEQUEUE_SLEEP;
3987         }
3988 
3989         for_each_sched_entity(se) {
3990                 cfs_rq = cfs_rq_of(se);
3991                 cfs_rq->h_nr_running--;
3992 
3993                 if (cfs_rq_throttled(cfs_rq))
3994                         break;
3995 
3996                 update_cfs_shares(cfs_rq);
3997                 update_entity_load_avg(se, 1);
3998         }
3999 
4000         if (!se) {
4001                 sub_nr_running(rq, 1);
4002                 update_rq_runnable_avg(rq, 1);
4003         }
4004         hrtick_update(rq);
4005 }
4006 
4007 #ifdef CONFIG_SMP
4008 /* Used instead of source_load when we know the type == 0 */
4009 static unsigned long weighted_cpuload(const int cpu)
4010 {
4011         return cpu_rq(cpu)->cfs.runnable_load_avg;
4012 }
4013 
4014 /*
4015  * Return a low guess at the load of a migration-source cpu weighted
4016  * according to the scheduling class and "nice" value.
4017  *
4018  * We want to under-estimate the load of migration sources, to
4019  * balance conservatively.
4020  */
4021 static unsigned long source_load(int cpu, int type)
4022 {
4023         struct rq *rq = cpu_rq(cpu);
4024         unsigned long total = weighted_cpuload(cpu);
4025 
4026         if (type == 0 || !sched_feat(LB_BIAS))
4027                 return total;
4028 
4029         return min(rq->cpu_load[type-1], total);
4030 }
4031 
4032 /*
4033  * Return a high guess at the load of a migration-target cpu weighted
4034  * according to the scheduling class and "nice" value.
4035  */
4036 static unsigned long target_load(int cpu, int type)
4037 {
4038         struct rq *rq = cpu_rq(cpu);
4039         unsigned long total = weighted_cpuload(cpu);
4040 
4041         if (type == 0 || !sched_feat(LB_BIAS))
4042                 return total;
4043 
4044         return max(rq->cpu_load[type-1], total);
4045 }
4046 
4047 static unsigned long capacity_of(int cpu)
4048 {
4049         return cpu_rq(cpu)->cpu_capacity;
4050 }
4051 
4052 static unsigned long cpu_avg_load_per_task(int cpu)
4053 {
4054         struct rq *rq = cpu_rq(cpu);
4055         unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
4056         unsigned long load_avg = rq->cfs.runnable_load_avg;
4057 
4058         if (nr_running)
4059                 return load_avg / nr_running;
4060 
4061         return 0;
4062 }
4063 
4064 static void record_wakee(struct task_struct *p)
4065 {
4066         /*
4067          * Rough decay (wiping) for cost saving, don't worry
4068          * about the boundary, really active task won't care
4069          * about the loss.
4070          */
4071         if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4072                 current->wakee_flips >>= 1;
4073                 current->wakee_flip_decay_ts = jiffies;
4074         }
4075 
4076         if (current->last_wakee != p) {
4077                 current->last_wakee = p;
4078                 current->wakee_flips++;
4079         }
4080 }
4081 
4082 static void task_waking_fair(struct task_struct *p)
4083 {
4084         struct sched_entity *se = &p->se;
4085         struct cfs_rq *cfs_rq = cfs_rq_of(se);
4086         u64 min_vruntime;
4087 
4088 #ifndef CONFIG_64BIT
4089         u64 min_vruntime_copy;
4090 
4091         do {
4092                 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4093                 smp_rmb();
4094                 min_vruntime = cfs_rq->min_vruntime;
4095         } while (min_vruntime != min_vruntime_copy);
4096 #else
4097         min_vruntime = cfs_rq->min_vruntime;
4098 #endif
4099 
4100         se->vruntime -= min_vruntime;
4101         record_wakee(p);
4102 }
4103 
4104 #ifdef CONFIG_FAIR_GROUP_SCHED
4105 /*
4106  * effective_load() calculates the load change as seen from the root_task_group
4107  *
4108  * Adding load to a group doesn't make a group heavier, but can cause movement
4109  * of group shares between cpus. Assuming the shares were perfectly aligned one
4110  * can calculate the shift in shares.
4111  *
4112  * Calculate the effective load difference if @wl is added (subtracted) to @tg
4113  * on this @cpu and results in a total addition (subtraction) of @wg to the
4114  * total group weight.
4115  *
4116  * Given a runqueue weight distribution (rw_i) we can compute a shares
4117  * distribution (s_i) using:
4118  *
4119  *   s_i = rw_i / \Sum rw_j                                             (1)
4120  *
4121  * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4122  * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4123  * shares distribution (s_i):
4124  *
4125  *   rw_i = {   2,   4,   1,   0 }
4126  *   s_i  = { 2/7, 4/7, 1/7,   0 }
4127  *
4128  * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4129  * task used to run on and the CPU the waker is running on), we need to
4130  * compute the effect of waking a task on either CPU and, in case of a sync
4131  * wakeup, compute the effect of the current task going to sleep.
4132  *
4133  * So for a change of @wl to the local @cpu with an overall group weight change
4134  * of @wl we can compute the new shares distribution (s'_i) using:
4135  *
4136  *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)                            (2)
4137  *
4138  * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4139  * differences in waking a task to CPU 0. The additional task changes the
4140  * weight and shares distributions like:
4141  *
4142  *   rw'_i = {   3,   4,   1,   0 }
4143  *   s'_i  = { 3/8, 4/8, 1/8,   0 }
4144  *
4145  * We can then compute the difference in effective weight by using:
4146  *
4147  *   dw_i = S * (s'_i - s_i)                                            (3)
4148  *
4149  * Where 'S' is the group weight as seen by its parent.
4150  *
4151  * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4152  * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4153  * 4/7) times the weight of the group.
4154  */
4155 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4156 {
4157         struct sched_entity *se = tg->se[cpu];
4158 
4159         if (!tg->parent)        /* the trivial, non-cgroup case */
4160                 return wl;
4161 
4162         for_each_sched_entity(se) {
4163                 long w, W;
4164 
4165                 tg = se->my_q->tg;
4166 
4167                 /*
4168                  * W = @wg + \Sum rw_j
4169                  */
4170                 W = wg + calc_tg_weight(tg, se->my_q);
4171 
4172                 /*
4173                  * w = rw_i + @wl
4174                  */
4175                 w = se->my_q->load.weight + wl;
4176 
4177                 /*
4178                  * wl = S * s'_i; see (2)
4179                  */
4180                 if (W > 0 && w < W)
4181                         wl = (w * tg->shares) / W;
4182                 else
4183                         wl = tg->shares;
4184 
4185                 /*
4186                  * Per the above, wl is the new se->load.weight value; since
4187                  * those are clipped to [MIN_SHARES, ...) do so now. See
4188                  * calc_cfs_shares().
4189                  */
4190                 if (wl < MIN_SHARES)
4191                         wl = MIN_SHARES;
4192 
4193                 /*
4194                  * wl = dw_i = S * (s'_i - s_i); see (3)
4195                  */
4196                 wl -= se->load.weight;
4197 
4198                 /*
4199                  * Recursively apply this logic to all parent groups to compute
4200                  * the final effective load change on the root group. Since
4201                  * only the @tg group gets extra weight, all parent groups can
4202                  * only redistribute existing shares. @wl is the shift in shares
4203                  * resulting from this level per the above.
4204                  */
4205                 wg = 0;
4206         }
4207 
4208         return wl;
4209 }
4210 #else
4211 
4212 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4213 {
4214         return wl;
4215 }
4216 
4217 #endif
4218 
4219 static int wake_wide(struct task_struct *p)
4220 {
4221         int factor = this_cpu_read(sd_llc_size);
4222 
4223         /*
4224          * Yeah, it's the switching-frequency, could means many wakee or
4225          * rapidly switch, use factor here will just help to automatically
4226          * adjust the loose-degree, so bigger node will lead to more pull.
4227          */
4228         if (p->wakee_flips > factor) {
4229                 /*
4230                  * wakee is somewhat hot, it needs certain amount of cpu
4231                  * resource, so if waker is far more hot, prefer to leave
4232                  * it alone.
4233                  */
4234                 if (current->wakee_flips > (factor * p->wakee_flips))
4235                         return 1;
4236         }
4237 
4238         return 0;
4239 }
4240 
4241 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4242 {
4243         s64 this_load, load;
4244         int idx, this_cpu, prev_cpu;
4245         unsigned long tl_per_task;
4246         struct task_group *tg;
4247         unsigned long weight;
4248         int balanced;
4249 
4250         /*
4251          * If we wake multiple tasks be careful to not bounce
4252          * ourselves around too much.
4253          */
4254         if (wake_wide(p))
4255                 return 0;
4256 
4257         idx       = sd->wake_idx;
4258         this_cpu  = smp_processor_id();
4259         prev_cpu  = task_cpu(p);
4260         load      = source_load(prev_cpu, idx);
4261         this_load = target_load(this_cpu, idx);
4262 
4263         /*
4264          * If sync wakeup then subtract the (maximum possible)
4265          * effect of the currently running task from the load
4266          * of the current CPU:
4267          */
4268         if (sync) {
4269                 tg = task_group(current);
4270                 weight = current->se.load.weight;
4271 
4272                 this_load += effective_load(tg, this_cpu, -weight, -weight);
4273                 load += effective_load(tg, prev_cpu, 0, -weight);
4274         }
4275 
4276         tg = task_group(p);
4277         weight = p->se.load.weight;
4278 
4279         /*
4280          * In low-load situations, where prev_cpu is idle and this_cpu is idle
4281          * due to the sync cause above having dropped this_load to 0, we'll
4282          * always have an imbalance, but there's really nothing you can do
4283          * about that, so that's good too.
4284          *
4285          * Otherwise check if either cpus are near enough in load to allow this
4286          * task to be woken on this_cpu.
4287          */
4288         if (this_load > 0) {
4289                 s64 this_eff_load, prev_eff_load;
4290 
4291                 this_eff_load = 100;
4292                 this_eff_load *= capacity_of(prev_cpu);
4293                 this_eff_load *= this_load +
4294                         effective_load(tg, this_cpu, weight, weight);
4295 
4296                 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4297                 prev_eff_load *= capacity_of(this_cpu);
4298                 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4299 
4300                 balanced = this_eff_load <= prev_eff_load;
4301         } else
4302                 balanced = true;
4303 
4304         /*
4305          * If the currently running task will sleep within
4306          * a reasonable amount of time then attract this newly
4307          * woken task:
4308          */
4309         if (sync && balanced)
4310                 return 1;
4311 
4312         schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4313         tl_per_task = cpu_avg_load_per_task(this_cpu);
4314 
4315         if (balanced ||
4316             (this_load <= load &&
4317              this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
4318                 /*
4319                  * This domain has SD_WAKE_AFFINE and
4320                  * p is cache cold in this domain, and
4321                  * there is no bad imbalance.
4322                  */
4323                 schedstat_inc(sd, ttwu_move_affine);
4324                 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4325 
4326                 return 1;
4327         }
4328         return 0;
4329 }
4330 
4331 /*
4332  * find_idlest_group finds and returns the least busy CPU group within the
4333  * domain.
4334  */
4335 static struct sched_group *
4336 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4337                   int this_cpu, int sd_flag)
4338 {
4339         struct sched_group *idlest = NULL, *group = sd->groups;
4340         unsigned long min_load = ULONG_MAX, this_load = 0;
4341         int load_idx = sd->forkexec_idx;
4342         int imbalance = 100 + (sd->imbalance_pct-100)/2;
4343 
4344         if (sd_flag & SD_BALANCE_WAKE)
4345                 load_idx = sd->wake_idx;
4346 
4347         do {
4348                 unsigned long load, avg_load;
4349                 int local_group;
4350                 int i;
4351 
4352                 /* Skip over this group if it has no CPUs allowed */
4353                 if (!cpumask_intersects(sched_group_cpus(group),
4354                                         tsk_cpus_allowed(p)))
4355                         continue;
4356 
4357                 local_group = cpumask_test_cpu(this_cpu,
4358                                                sched_group_cpus(group));
4359 
4360                 /* Tally up the load of all CPUs in the group */
4361                 avg_load = 0;
4362 
4363                 for_each_cpu(i, sched_group_cpus(group)) {
4364                         /* Bias balancing toward cpus of our domain */
4365                         if (local_group)
4366                                 load = source_load(i, load_idx);
4367                         else
4368                                 load = target_load(i, load_idx);
4369 
4370                         avg_load += load;
4371                 }
4372 
4373                 /* Adjust by relative CPU capacity of the group */
4374                 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4375 
4376                 if (local_group) {
4377                         this_load = avg_load;
4378                 } else if (avg_load < min_load) {
4379                         min_load = avg_load;
4380                         idlest = group;
4381                 }
4382         } while (group = group->next, group != sd->groups);
4383 
4384         if (!idlest || 100*this_load < imbalance*min_load)
4385                 return NULL;
4386         return idlest;
4387 }
4388 
4389 /*
4390  * find_idlest_cpu - find the idlest cpu among the cpus in group.
4391  */
4392 static int
4393 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4394 {
4395         unsigned long load, min_load = ULONG_MAX;
4396         int idlest = -1;
4397         int i;
4398 
4399         /* Traverse only the allowed CPUs */
4400         for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4401                 load = weighted_cpuload(i);
4402 
4403                 if (load < min_load || (load == min_load && i == this_cpu)) {
4404                         min_load = load;
4405                         idlest = i;
4406                 }
4407         }
4408 
4409         return idlest;
4410 }
4411 
4412 /*
4413  * Try and locate an idle CPU in the sched_domain.
4414  */
4415 static int select_idle_sibling(struct task_struct *p, int target)
4416 {
4417         struct sched_domain *sd;
4418         struct sched_group *sg;
4419         int i = task_cpu(p);
4420 
4421         if (idle_cpu(target))
4422                 return target;
4423 
4424         /*
4425          * If the prevous cpu is cache affine and idle, don't be stupid.
4426          */
4427         if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4428                 return i;
4429 
4430         /*
4431          * Otherwise, iterate the domains and find an elegible idle cpu.
4432          */
4433         sd = rcu_dereference(per_cpu(sd_llc, target));
4434         for_each_lower_domain(sd) {
4435                 sg = sd->groups;
4436                 do {
4437                         if (!cpumask_intersects(sched_group_cpus(sg),
4438                                                 tsk_cpus_allowed(p)))
4439                                 goto next;
4440 
4441                         for_each_cpu(i, sched_group_cpus(sg)) {
4442                                 if (i == target || !idle_cpu(i))
4443                                         goto next;
4444                         }
4445 
4446                         target = cpumask_first_and(sched_group_cpus(sg),
4447                                         tsk_cpus_allowed(p));
4448                         goto done;
4449 next:
4450                         sg = sg->next;
4451                 } while (sg != sd->groups);
4452         }
4453 done:
4454         return target;
4455 }
4456 
4457 /*
4458  * select_task_rq_fair: Select target runqueue for the waking task in domains
4459  * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4460  * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4461  *
4462  * Balances load by selecting the idlest cpu in the idlest group, or under
4463  * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4464  *
4465  * Returns the target cpu number.
4466  *
4467  * preempt must be disabled.
4468  */
4469 static int
4470 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4471 {
4472         struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4473         int cpu = smp_processor_id();
4474         int new_cpu = cpu;
4475         int want_affine = 0;
4476         int sync = wake_flags & WF_SYNC;
4477 
4478         if (p->nr_cpus_allowed == 1)
4479                 return prev_cpu;
4480 
4481         if (sd_flag & SD_BALANCE_WAKE) {
4482                 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
4483                         want_affine = 1;
4484                 new_cpu = prev_cpu;
4485         }
4486 
4487         rcu_read_lock();
4488         for_each_domain(cpu, tmp) {
4489                 if (!(tmp->flags & SD_LOAD_BALANCE))
4490                         continue;
4491 
4492                 /*
4493                  * If both cpu and prev_cpu are part of this domain,
4494                  * cpu is a valid SD_WAKE_AFFINE target.
4495                  */
4496                 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4497                     cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4498                         affine_sd = tmp;
4499                         break;
4500                 }
4501 
4502                 if (tmp->flags & sd_flag)
4503                         sd = tmp;
4504         }
4505 
4506         if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4507                 prev_cpu = cpu;
4508 
4509         if (sd_flag & SD_BALANCE_WAKE) {
4510                 new_cpu = select_idle_sibling(p, prev_cpu);
4511                 goto unlock;
4512         }
4513 
4514         while (sd) {
4515                 struct sched_group *group;
4516                 int weight;
4517 
4518                 if (!(sd->flags & sd_flag)) {
4519                         sd = sd->child;
4520                         continue;
4521                 }
4522 
4523                 group = find_idlest_group(sd, p, cpu, sd_flag);
4524                 if (!group) {
4525                         sd = sd->child;
4526                         continue;
4527                 }
4528 
4529                 new_cpu = find_idlest_cpu(group, p, cpu);
4530                 if (new_cpu == -1 || new_cpu == cpu) {
4531                         /* Now try balancing at a lower domain level of cpu */
4532                         sd = sd->child;
4533                         continue;
4534                 }
4535 
4536                 /* Now try balancing at a lower domain level of new_cpu */
4537                 cpu = new_cpu;
4538                 weight = sd->span_weight;
4539                 sd = NULL;
4540                 for_each_domain(cpu, tmp) {
4541                         if (weight <= tmp->span_weight)
4542                                 break;
4543                         if (tmp->flags & sd_flag)
4544                                 sd = tmp;
4545                 }
4546                 /* while loop will break here if sd == NULL */
4547         }
4548 unlock:
4549         rcu_read_unlock();
4550 
4551         return new_cpu;
4552 }
4553 
4554 /*
4555  * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
4556  * cfs_rq_of(p) references at time of call are still valid and identify the
4557  * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
4558  * other assumptions, including the state of rq->lock, should be made.
4559  */
4560 static void
4561 migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4562 {
4563         struct sched_entity *se = &p->se;
4564         struct cfs_rq *cfs_rq = cfs_rq_of(se);
4565 
4566         /*
4567          * Load tracking: accumulate removed load so that it can be processed
4568          * when we next update owning cfs_rq under rq->lock.  Tasks contribute
4569          * to blocked load iff they have a positive decay-count.  It can never
4570          * be negative here since on-rq tasks have decay-count == 0.
4571          */
4572         if (se->avg.decay_count) {
4573                 se->avg.decay_count = -__synchronize_entity_decay(se);
4574                 atomic_long_add(se->avg.load_avg_contrib,
4575                                                 &cfs_rq->removed_load);
4576         }
4577 
4578         /* We have migrated, no longer consider this task hot */
4579         se->exec_start = 0;
4580 }
4581 #endif /* CONFIG_SMP */
4582 
4583 static unsigned long
4584 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4585 {
4586         unsigned long gran = sysctl_sched_wakeup_granularity;
4587 
4588         /*
4589          * Since its curr running now, convert the gran from real-time
4590          * to virtual-time in his units.
4591          *
4592          * By using 'se' instead of 'curr' we penalize light tasks, so
4593          * they get preempted easier. That is, if 'se' < 'curr' then
4594          * the resulting gran will be larger, therefore penalizing the
4595          * lighter, if otoh 'se' > 'curr' then the resulting gran will
4596          * be smaller, again penalizing the lighter task.
4597          *
4598          * This is especially important for buddies when the leftmost
4599          * task is higher priority than the buddy.
4600          */
4601         return calc_delta_fair(gran, se);
4602 }
4603 
4604 /*
4605  * Should 'se' preempt 'curr'.
4606  *
4607  *             |s1
4608  *        |s2
4609  *   |s3
4610  *         g
4611  *      |<--->|c
4612  *
4613  *  w(c, s1) = -1
4614  *  w(c, s2) =  0
4615  *  w(c, s3) =  1
4616  *
4617  */
4618 static int
4619 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
4620 {
4621         s64 gran, vdiff = curr->vruntime - se->vruntime;
4622 
4623         if (vdiff <= 0)
4624                 return -1;
4625 
4626         gran = wakeup_gran(curr, se);
4627         if (vdiff > gran)
4628                 return 1;
4629 
4630         return 0;
4631 }
4632 
4633 static void set_last_buddy(struct sched_entity *se)
4634 {
4635         if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
4636                 return;
4637 
4638         for_each_sched_entity(se)
4639                 cfs_rq_of(se)->last = se;
4640 }
4641 
4642 static void set_next_buddy(struct sched_entity *se)
4643 {
4644         if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
4645                 return;
4646 
4647         for_each_sched_entity(se)
4648                 cfs_rq_of(se)->next = se;
4649 }
4650 
4651 static void set_skip_buddy(struct sched_entity *se)
4652 {
4653         for_each_sched_entity(se)
4654                 cfs_rq_of(se)->skip = se;
4655 }
4656 
4657 /*
4658  * Preempt the current task with a newly woken task if needed:
4659  */
4660 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4661 {
4662         struct task_struct *curr = rq->curr;
4663         struct sched_entity *se = &curr->se, *pse = &p->se;
4664         struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4665         int scale = cfs_rq->nr_running >= sched_nr_latency;
4666         int next_buddy_marked = 0;
4667 
4668         if (unlikely(se == pse))
4669                 return;
4670 
4671         /*
4672          * This is possible from callers such as move_task(), in which we
4673          * unconditionally check_prempt_curr() after an enqueue (which may have
4674          * lead to a throttle).  This both saves work and prevents false
4675          * next-buddy nomination below.
4676          */
4677         if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
4678                 return;
4679 
4680         if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
4681                 set_next_buddy(pse);
4682                 next_buddy_marked = 1;
4683         }
4684 
4685         /*
4686          * We can come here with TIF_NEED_RESCHED already set from new task
4687          * wake up path.
4688          *
4689          * Note: this also catches the edge-case of curr being in a throttled
4690          * group (e.g. via set_curr_task), since update_curr() (in the
4691          * enqueue of curr) will have resulted in resched being set.  This
4692          * prevents us from potentially nominating it as a false LAST_BUDDY
4693          * below.
4694          */
4695         if (test_tsk_need_resched(curr))
4696                 return;
4697 
4698         /* Idle tasks are by definition preempted by non-idle tasks. */
4699         if (unlikely(curr->policy == SCHED_IDLE) &&
4700             likely(p->policy != SCHED_IDLE))
4701                 goto preempt;
4702 
4703         /*
4704          * Batch and idle tasks do not preempt non-idle tasks (their preemption
4705          * is driven by the tick):
4706          */
4707         if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
4708                 return;
4709 
4710         find_matching_se(&se, &pse);
4711         update_curr(cfs_rq_of(se));
4712         BUG_ON(!pse);
4713         if (wakeup_preempt_entity(se, pse) == 1) {
4714                 /*
4715                  * Bias pick_next to pick the sched entity that is
4716                  * triggering this preemption.
4717                  */
4718                 if (!next_buddy_marked)
4719                         set_next_buddy(pse);
4720                 goto preempt;
4721         }
4722 
4723         return;
4724 
4725 preempt:
4726         resched_task(curr);
4727         /*
4728          * Only set the backward buddy when the current task is still
4729          * on the rq. This can happen when a wakeup gets interleaved
4730          * with schedule on the ->pre_schedule() or idle_balance()
4731          * point, either of which can * drop the rq lock.
4732          *
4733          * Also, during early boot the idle thread is in the fair class,
4734          * for obvious reasons its a bad idea to schedule back to it.
4735          */
4736         if (unlikely(!se->on_rq || curr == rq->idle))
4737                 return;
4738 
4739         if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
4740                 set_last_buddy(se);
4741 }
4742 
4743 static struct task_struct *
4744 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
4745 {
4746         struct cfs_rq *cfs_rq = &rq->cfs;
4747         struct sched_entity *se;
4748         struct task_struct *p;
4749         int new_tasks;
4750 
4751 again:
4752 #ifdef CONFIG_FAIR_GROUP_SCHED
4753         if (!cfs_rq->nr_running)
4754                 goto idle;
4755 
4756         if (prev->sched_class != &fair_sched_class)
4757                 goto simple;
4758 
4759         /*
4760          * Because of the set_next_buddy() in dequeue_task_fair() it is rather
4761          * likely that a next task is from the same cgroup as the current.
4762          *
4763          * Therefore attempt to avoid putting and setting the entire cgroup
4764          * hierarchy, only change the part that actually changes.
4765          */
4766 
4767         do {
4768                 struct sched_entity *curr = cfs_rq->curr;
4769 
4770                 /*
4771                  * Since we got here without doing put_prev_entity() we also
4772                  * have to consider cfs_rq->curr. If it is still a runnable
4773                  * entity, update_curr() will update its vruntime, otherwise
4774                  * forget we've ever seen it.
4775                  */
4776                 if (curr && curr->on_rq)
4777                         update_curr(cfs_rq);
4778                 else
4779                         curr = NULL;
4780 
4781                 /*
4782                  * This call to check_cfs_rq_runtime() will do the throttle and
4783                  * dequeue its entity in the parent(s). Therefore the 'simple'
4784                  * nr_running test will indeed be correct.
4785                  */
4786                 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
4787                         goto simple;
4788 
4789                 se = pick_next_entity(cfs_rq, curr);
4790                 cfs_rq = group_cfs_rq(se);
4791         } while (cfs_rq);
4792 
4793         p = task_of(se);
4794 
4795         /*
4796          * Since we haven't yet done put_prev_entity and if the selected task
4797          * is a different task than we started out with, try and touch the
4798          * least amount of cfs_rqs.
4799          */
4800         if (prev != p) {
4801                 struct sched_entity *pse = &prev->se;
4802 
4803                 while (!(cfs_rq = is_same_group(se, pse))) {
4804                         int se_depth = se->depth;
4805                         int pse_depth = pse->depth;
4806 
4807                         if (se_depth <= pse_depth) {
4808                                 put_prev_entity(cfs_rq_of(pse), pse);
4809                                 pse = parent_entity(pse);
4810                         }
4811                         if (se_depth >= pse_depth) {
4812                                 set_next_entity(cfs_rq_of(se), se);
4813                                 se = parent_entity(se);
4814                         }
4815                 }
4816 
4817                 put_prev_entity(cfs_rq, pse);
4818                 set_next_entity(cfs_rq, se);
4819         }
4820 
4821         if (hrtick_enabled(rq))
4822                 hrtick_start_fair(rq, p);
4823 
4824         return p;
4825 simple:
4826         cfs_rq = &rq->cfs;
4827 #endif
4828 
4829         if (!cfs_rq->nr_running)
4830                 goto idle;
4831 
4832         put_prev_task(rq, prev);
4833 
4834         do {
4835                 se = pick_next_entity(cfs_rq, NULL);
4836                 set_next_entity(cfs_rq, se);
4837                 cfs_rq = group_cfs_rq(se);
4838         } while (cfs_rq);
4839 
4840         p = task_of(se);
4841 
4842         if (hrtick_enabled(rq))
4843                 hrtick_start_fair(rq, p);
4844 
4845         return p;
4846 
4847 idle:
4848         new_tasks = idle_balance(rq);
4849         /*
4850          * Because idle_balance() releases (and re-acquires) rq->lock, it is
4851          * possible for any higher priority task to appear. In that case we
4852          * must re-start the pick_next_entity() loop.
4853          */
4854         if (new_tasks < 0)
4855                 return RETRY_TASK;
4856 
4857         if (new_tasks > 0)
4858                 goto again;
4859 
4860         return NULL;
4861 }
4862 
4863 /*
4864  * Account for a descheduled task:
4865  */
4866 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
4867 {
4868         struct sched_entity *se = &prev->se;
4869         struct cfs_rq *cfs_rq;
4870 
4871         for_each_sched_entity(se) {
4872                 cfs_rq = cfs_rq_of(se);
4873                 put_prev_entity(cfs_rq, se);
4874         }
4875 }
4876 
4877 /*
4878  * sched_yield() is very simple
4879  *
4880  * The magic of dealing with the ->skip buddy is in pick_next_entity.
4881  */
4882 static void yield_task_fair(struct rq *rq)
4883 {
4884         struct task_struct *curr = rq->curr;
4885         struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4886         struct sched_entity *se = &curr->se;
4887 
4888         /*
4889          * Are we the only task in the tree?
4890          */
4891         if (unlikely(rq->nr_running == 1))
4892                 return;
4893 
4894         clear_buddies(cfs_rq, se);
4895 
4896         if (curr->policy != SCHED_BATCH) {
4897                 update_rq_clock(rq);
4898                 /*
4899                  * Update run-time statistics of the 'current'.
4900                  */
4901                 update_curr(cfs_rq);
4902                 /*
4903                  * Tell update_rq_clock() that we've just updated,
4904                  * so we don't do microscopic update in schedule()
4905                  * and double the fastpath cost.
4906                  */
4907                  rq->skip_clock_update = 1;
4908         }
4909 
4910         set_skip_buddy(se);
4911 }
4912 
4913 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
4914 {
4915         struct sched_entity *se = &p->se;
4916 
4917         /* throttled hierarchies are not runnable */
4918         if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
4919                 return false;
4920 
4921         /* Tell the scheduler that we'd really like pse to run next. */
4922         set_next_buddy(se);
4923 
4924         yield_task_fair(rq);
4925 
4926         return true;
4927 }
4928 
4929 #ifdef CONFIG_SMP
4930 /**************************************************
4931  * Fair scheduling class load-balancing methods.
4932  *
4933  * BASICS
4934  *
4935  * The purpose of load-balancing is to achieve the same basic fairness the
4936  * per-cpu scheduler provides, namely provide a proportional amount of compute
4937  * time to each task. This is expressed in the following equation:
4938  *
4939  *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
4940  *
4941  * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
4942  * W_i,0 is defined as:
4943  *
4944  *   W_i,0 = \Sum_j w_i,j                                             (2)
4945  *
4946  * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
4947  * is derived from the nice value as per prio_to_weight[].
4948  *
4949  * The weight average is an exponential decay average of the instantaneous
4950  * weight:
4951  *
4952  *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
4953  *
4954  * C_i is the compute capacity of cpu i, typically it is the
4955  * fraction of 'recent' time available for SCHED_OTHER task execution. But it
4956  * can also include other factors [XXX].
4957  *
4958  * To achieve this balance we define a measure of imbalance which follows
4959  * directly from (1):
4960  *
4961  *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
4962  *
4963  * We them move tasks around to minimize the imbalance. In the continuous
4964  * function space it is obvious this converges, in the discrete case we get
4965  * a few fun cases generally called infeasible weight scenarios.
4966  *
4967  * [XXX expand on:
4968  *     - infeasible weights;
4969  *     - local vs global optima in the discrete case. ]
4970  *
4971  *
4972  * SCHED DOMAINS
4973  *
4974  * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
4975  * for all i,j solution, we create a tree of cpus that follows the hardware
4976  * topology where each level pairs two lower groups (or better). This results
4977  * in O(log n) layers. Furthermore we reduce the number of cpus going up the
4978  * tree to only the first of the previous level and we decrease the frequency
4979  * of load-balance at each level inv. proportional to the number of cpus in
4980  * the groups.
4981  *
4982  * This yields:
4983  *
4984  *     log_2 n     1     n
4985  *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
4986  *     i = 0      2^i   2^i
4987  *                               `- size of each group
4988  *         |         |     `- number of cpus doing load-balance
4989  *         |         `- freq
4990  *         `- sum over all levels
4991  *
4992  * Coupled with a limit on how many tasks we can migrate every balance pass,
4993  * this makes (5) the runtime complexity of the balancer.
4994  *
4995  * An important property here is that each CPU is still (indirectly) connected
4996  * to every other cpu in at most O(log n) steps:
4997  *
4998  * The adjacency matrix of the resulting graph is given by:
4999  *
5000  *             log_2 n     
5001  *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
5002  *             k = 0
5003  *
5004  * And you'll find that:
5005  *
5006  *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
5007  *
5008  * Showing there's indeed a path between every cpu in at most O(log n) steps.
5009  * The task movement gives a factor of O(m), giving a convergence complexity
5010  * of:
5011  *
5012  *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
5013  *
5014  *
5015  * WORK CONSERVING
5016  *
5017  * In order to avoid CPUs going idle while there's still work to do, new idle
5018  * balancing is more aggressive and has the newly idle cpu iterate up the domain
5019  * tree itself instead of relying on other CPUs to bring it work.
5020  *
5021  * This adds some complexity to both (5) and (8) but it reduces the total idle
5022  * time.
5023  *
5024  * [XXX more?]
5025  *
5026  *
5027  * CGROUPS
5028  *
5029  * Cgroups make a horror show out of (2), instead of a simple sum we get:
5030  *
5031  *                                s_k,i
5032  *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
5033  *                                 S_k
5034  *
5035  * Where
5036  *
5037  *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
5038  *
5039  * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5040  *
5041  * The big problem is S_k, its a global sum needed to compute a local (W_i)
5042  * property.
5043  *
5044  * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5045  *      rewrite all of this once again.]
5046  */ 
5047 
5048 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5049 
5050 enum fbq_type { regular, remote, all };
5051 
5052 #define LBF_ALL_PINNED  0x01
5053 #define LBF_NEED_BREAK  0x02
5054 #define LBF_DST_PINNED  0x04
5055 #define LBF_SOME_PINNED 0x08
5056 
5057 struct lb_env {
5058         struct sched_domain     *sd;
5059 
5060         struct rq               *src_rq;
5061         int                     src_cpu;
5062 
5063         int                     dst_cpu;
5064         struct rq               *dst_rq;
5065 
5066         struct cpumask          *dst_grpmask;
5067         int                     new_dst_cpu;
5068         enum cpu_idle_type      idle;
5069         long                    imbalance;
5070         /* The set of CPUs under consideration for load-balancing */
5071         struct cpumask          *cpus;
5072 
5073         unsigned int            flags;
5074 
5075         unsigned int            loop;
5076         unsigned int            loop_break;
5077         unsigned int            loop_max;
5078 
5079         enum fbq_type           fbq_type;
5080 };
5081 
5082 /*
5083  * move_task - move a task from one runqueue to another runqueue.
5084  * Both runqueues must be locked.
5085  */
5086 static void move_task(struct task_struct *p, struct lb_env *env)
5087 {
5088         deactivate_task(env->src_rq, p, 0);
5089         set_task_cpu(p, env->dst_cpu);
5090         activate_task(env->dst_rq, p, 0);
5091         check_preempt_curr(env->dst_rq, p, 0);
5092 }
5093 
5094 /*
5095  * Is this task likely cache-hot:
5096  */
5097 static int
5098 task_hot(struct task_struct *p, u64 now)
5099 {
5100         s64 delta;
5101 
5102         if (p->sched_class != &fair_sched_class)
5103                 return 0;
5104 
5105         if (unlikely(p->policy == SCHED_IDLE))
5106                 return 0;
5107 
5108         /*
5109          * Buddy candidates are cache hot:
5110          */
5111         if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
5112                         (&p->se == cfs_rq_of(&p->se)->next ||
5113                          &p->se == cfs_rq_of(&p->se)->last))
5114                 return 1;
5115 
5116         if (sysctl_sched_migration_cost == -1)
5117                 return 1;
5118         if (sysctl_sched_migration_cost == 0)
5119                 return 0;
5120 
5121         delta = now - p->se.exec_start;
5122 
5123         return delta < (s64)sysctl_sched_migration_cost;
5124 }
5125 
5126 #ifdef CONFIG_NUMA_BALANCING
5127 /* Returns true if the destination node has incurred more faults */
5128 static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
5129 {
5130         struct numa_group *numa_group = rcu_dereference(p->numa_group);
5131         int src_nid, dst_nid;
5132 
5133         if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults_memory ||
5134             !(env->sd->flags & SD_NUMA)) {
5135                 return false;
5136         }
5137 
5138         src_nid = cpu_to_node(env->src_cpu);
5139         dst_nid = cpu_to_node(env->dst_cpu);
5140 
5141         if (src_nid == dst_nid)
5142                 return false;
5143 
5144         if (numa_group) {
5145                 /* Task is already in the group's interleave set. */
5146                 if (node_isset(src_nid, numa_group->active_nodes))
5147                         return false;
5148 
5149                 /* Task is moving into the group's interleave set. */
5150                 if (node_isset(dst_nid, numa_group->active_nodes))
5151                         return true;
5152 
5153                 return group_faults(p, dst_nid) > group_faults(p, src_nid);
5154         }
5155 
5156         /* Encourage migration to the preferred node. */
5157         if (dst_nid == p->numa_preferred_nid)
5158                 return true;
5159 
5160         return task_faults(p, dst_nid) > task_faults(p, src_nid);
5161 }
5162 
5163 
5164 static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5165 {
5166         struct numa_group *numa_group = rcu_dereference(p->numa_group);
5167         int src_nid, dst_nid;
5168 
5169         if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
5170                 return false;
5171 
5172         if (!p->numa_faults_memory || !(env->sd->flags & SD_NUMA))
5173                 return false;
5174 
5175         src_nid = cpu_to_node(env->src_cpu);
5176         dst_nid = cpu_to_node(env->dst_cpu);
5177 
5178         if (src_nid == dst_nid)
5179                 return false;
5180 
5181         if (numa_group) {
5182                 /* Task is moving within/into the group's interleave set. */
5183                 if (node_isset(dst_nid, numa_group->active_nodes))
5184                         return false;
5185 
5186                 /* Task is moving out of the group's interleave set. */
5187                 if (node_isset(src_nid, numa_group->active_nodes))
5188                         return true;
5189 
5190                 return group_faults(p, dst_nid) < group_faults(p, src_nid);
5191         }
5192 
5193         /* Migrating away from the preferred node is always bad. */
5194         if (src_nid == p->numa_preferred_nid)
5195                 return true;
5196 
5197         return task_faults(p, dst_nid) < task_faults(p, src_nid);
5198 }
5199 
5200 #else
5201 static inline bool migrate_improves_locality(struct task_struct *p,
5202                                              struct lb_env *env)
5203 {
5204         return false;
5205 }
5206 
5207 static inline bool migrate_degrades_locality(struct task_struct *p,
5208                                              struct lb_env *env)
5209 {
5210         return false;
5211 }
5212 #endif
5213 
5214 /*
5215  * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5216  */
5217 static
5218 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5219 {
5220         int tsk_cache_hot = 0;
5221         /*
5222          * We do not migrate tasks that are:
5223          * 1) throttled_lb_pair, or
5224          * 2) cannot be migrated to this CPU due to cpus_allowed, or
5225          * 3) running (obviously), or
5226          * 4) are cache-hot on their current CPU.
5227          */
5228         if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5229                 return 0;
5230 
5231         if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5232                 int cpu;
5233 
5234                 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5235 
5236                 env->flags |= LBF_SOME_PINNED;
5237 
5238                 /*
5239                  * Remember if this task can be migrated to any other cpu in
5240                  * our sched_group. We may want to revisit it if we couldn't
5241                  * meet load balance goals by pulling other tasks on src_cpu.
5242                  *
5243                  * Also avoid computing new_dst_cpu if we have already computed
5244                  * one in current iteration.
5245                  */
5246                 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5247                         return 0;
5248 
5249                 /* Prevent to re-select dst_cpu via env's cpus */
5250                 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5251                         if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5252                                 env->flags |= LBF_DST_PINNED;
5253                                 env->new_dst_cpu = cpu;
5254                                 break;
5255                         }
5256                 }
5257 
5258                 return 0;
5259         }
5260 
5261         /* Record that we found atleast one task that could run on dst_cpu */
5262         env->flags &= ~LBF_ALL_PINNED;
5263 
5264         if (task_running(env->src_rq, p)) {
5265                 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5266                 return 0;
5267         }
5268 
5269         /*
5270          * Aggressive migration if:
5271          * 1) destination numa is preferred
5272          * 2) task is cache cold, or
5273          * 3) too many balance attempts have failed.
5274          */
5275         tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq));
5276         if (!tsk_cache_hot)
5277                 tsk_cache_hot = migrate_degrades_locality(p, env);
5278 
5279         if (migrate_improves_locality(p, env)) {
5280 #ifdef CONFIG_SCHEDSTATS
5281                 if (tsk_cache_hot) {
5282                         schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5283                         schedstat_inc(p, se.statistics.nr_forced_migrations);
5284                 }
5285 #endif
5286                 return 1;
5287         }
5288 
5289         if (!tsk_cache_hot ||
5290                 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5291 
5292                 if (tsk_cache_hot) {
5293                         schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5294                         schedstat_inc(p, se.statistics.nr_forced_migrations);
5295                 }
5296 
5297                 return 1;
5298         }
5299 
5300         schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5301         return 0;
5302 }
5303 
5304 /*
5305  * move_one_task tries to move exactly one task from busiest to this_rq, as
5306  * part of active balancing operations within "domain".
5307  * Returns 1 if successful and 0 otherwise.
5308  *
5309  * Called with both runqueues locked.
5310  */
5311 static int move_one_task(struct lb_env *env)
5312 {
5313         struct task_struct *p, *n;
5314 
5315         list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5316                 if (!can_migrate_task(p, env))
5317                         continue;
5318 
5319                 move_task(p, env);
5320                 /*
5321                  * Right now, this is only the second place move_task()
5322                  * is called, so we can safely collect move_task()
5323                  * stats here rather than inside move_task().
5324                  */
5325                 schedstat_inc(env->sd, lb_gained[env->idle]);
5326                 return 1;
5327         }
5328         return 0;
5329 }
5330 
5331 static const unsigned int sched_nr_migrate_break = 32;
5332 
5333 /*
5334  * move_tasks tries to move up to imbalance weighted load from busiest to
5335  * this_rq, as part of a balancing operation within domain "sd".
5336  * Returns 1 if successful and 0 otherwise.
5337  *
5338  * Called with both runqueues locked.
5339  */
5340 static int move_tasks(struct lb_env *env)
5341 {
5342         struct list_head *tasks = &env->src_rq->cfs_tasks;
5343         struct task_struct *p;
5344         unsigned long load;
5345         int pulled = 0;
5346 
5347         if (env->imbalance <= 0)
5348                 return 0;
5349 
5350         while (!list_empty(tasks)) {
5351                 p = list_first_entry(tasks, struct task_struct, se.group_node);
5352 
5353                 env->loop++;
5354                 /* We've more or less seen every task there is, call it quits */
5355                 if (env->loop > env->loop_max)
5356                         break;
5357 
5358                 /* take a breather every nr_migrate tasks */
5359                 if (env->loop > env->loop_break) {
5360                         env->loop_break += sched_nr_migrate_break;
5361                         env->flags |= LBF_NEED_BREAK;
5362                         break;
5363                 }
5364 
5365                 if (!can_migrate_task(p, env))
5366                         goto next;
5367 
5368                 load = task_h_load(p);
5369 
5370                 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5371                         goto next;
5372 
5373                 if ((load / 2) > env->imbalance)
5374                         goto next;
5375 
5376                 move_task(p, env);
5377                 pulled++;
5378                 env->imbalance -= load;
5379 
5380 #ifdef CONFIG_PREEMPT
5381                 /*
5382                  * NEWIDLE balancing is a source of latency, so preemptible
5383                  * kernels will stop after the first task is pulled to minimize
5384                  * the critical section.
5385                  */
5386                 if (env->idle == CPU_NEWLY_IDLE)
5387                         break;
5388 #endif
5389 
5390                 /*
5391                  * We only want to steal up to the prescribed amount of
5392                  * weighted load.
5393                  */
5394                 if (env->imbalance <= 0)
5395                         break;
5396 
5397                 continue;
5398 next:
5399                 list_move_tail(&p->se.group_node, tasks);
5400         }
5401 
5402         /*
5403          * Right now, this is one of only two places move_task() is called,
5404          * so we can safely collect move_task() stats here rather than
5405          * inside move_task().
5406          */
5407         schedstat_add(env->sd, lb_gained[env->idle], pulled);
5408 
5409         return pulled;
5410 }
5411 
5412 #ifdef CONFIG_FAIR_GROUP_SCHED
5413 /*
5414  * update tg->load_weight by folding this cpu's load_avg
5415  */
5416 static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
5417 {
5418         struct sched_entity *se = tg->se[cpu];
5419         struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
5420 
5421         /* throttled entities do not contribute to load */
5422         if (throttled_hierarchy(cfs_rq))
5423                 return;
5424 
5425         update_cfs_rq_blocked_load(cfs_rq, 1);
5426 
5427         if (se) {
5428                 update_entity_load_avg(se, 1);
5429                 /*
5430                  * We pivot on our runnable average having decayed to zero for
5431                  * list removal.  This generally implies that all our children
5432                  * have also been removed (modulo rounding error or bandwidth
5433                  * control); however, such cases are rare and we can fix these
5434                  * at enqueue.
5435                  *
5436                  * TODO: fix up out-of-order children on enqueue.
5437                  */
5438                 if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
5439                         list_del_leaf_cfs_rq(cfs_rq);
5440         } else {
5441                 struct rq *rq = rq_of(cfs_rq);
5442                 update_rq_runnable_avg(rq, rq->nr_running);
5443         }
5444 }
5445 
5446 static void update_blocked_averages(int cpu)
5447 {
5448         struct rq *rq = cpu_rq(cpu);
5449         struct cfs_rq *cfs_rq;
5450         unsigned long flags;
5451 
5452         raw_spin_lock_irqsave(&rq->lock, flags);
5453         update_rq_clock(rq);
5454         /*
5455          * Iterates the task_group tree in a bottom up fashion, see
5456          * list_add_leaf_cfs_rq() for details.
5457          */
5458         for_each_leaf_cfs_rq(rq, cfs_rq) {
5459                 /*
5460                  * Note: We may want to consider periodically releasing
5461                  * rq->lock about these updates so that creating many task
5462                  * groups does not result in continually extending hold time.
5463                  */
5464                 __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
5465         }
5466 
5467         raw_spin_unlock_irqrestore(&rq->lock, flags);
5468 }
5469 
5470 /*
5471  * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5472  * This needs to be done in a top-down fashion because the load of a child
5473  * group is a fraction of its parents load.
5474  */
5475 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5476 {
5477         struct rq *rq = rq_of(cfs_rq);
5478         struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5479         unsigned long now = jiffies;
5480         unsigned long load;
5481 
5482         if (cfs_rq->last_h_load_update == now)
5483                 return;
5484 
5485         cfs_rq->h_load_next = NULL;
5486         for_each_sched_entity(se) {
5487                 cfs_rq = cfs_rq_of(se);
5488                 cfs_rq->h_load_next = se;
5489                 if (cfs_rq->last_h_load_update == now)
5490                         break;
5491         }
5492 
5493         if (!se) {
5494                 cfs_rq->h_load = cfs_rq->runnable_load_avg;
5495                 cfs_rq->last_h_load_update = now;
5496         }
5497 
5498         while ((se = cfs_rq->h_load_next) != NULL) {
5499                 load = cfs_rq->h_load;
5500                 load = div64_ul(load * se->avg.load_avg_contrib,
5501                                 cfs_rq->runnable_load_avg + 1);
5502                 cfs_rq = group_cfs_rq(se);
5503                 cfs_rq->h_load = load;
5504                 cfs_rq->last_h_load_update = now;
5505         }
5506 }
5507 
5508 static unsigned long task_h_load(struct task_struct *p)
5509 {
5510         struct cfs_rq *cfs_rq = task_cfs_rq(p);
5511 
5512         update_cfs_rq_h_load(cfs_rq);
5513         return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
5514                         cfs_rq->runnable_load_avg + 1);
5515 }
5516 #else
5517 static inline void update_blocked_averages(int cpu)
5518 {
5519 }
5520 
5521 static unsigned long task_h_load(struct task_struct *p)
5522 {
5523         return p->se.avg.load_avg_contrib;
5524 }
5525 #endif
5526 
5527 /********** Helpers for find_busiest_group ************************/
5528 /*
5529  * sg_lb_stats - stats of a sched_group required for load_balancing
5530  */
5531 struct sg_lb_stats {
5532         unsigned long avg_load; /*Avg load across the CPUs of the group */
5533         unsigned long group_load; /* Total load over the CPUs of the group */
5534         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
5535         unsigned long load_per_task;
5536         unsigned long group_capacity;
5537         unsigned int sum_nr_running; /* Nr tasks running in the group */
5538         unsigned int group_capacity_factor;
5539         unsigned int idle_cpus;
5540         unsigned int group_weight;
5541         int group_imb; /* Is there an imbalance in the group ? */
5542         int group_has_free_capacity;
5543 #ifdef CONFIG_NUMA_BALANCING
5544         unsigned int nr_numa_running;
5545         unsigned int nr_preferred_running;
5546 #endif
5547 };
5548 
5549 /*
5550  * sd_lb_stats - Structure to store the statistics of a sched_domain
5551  *               during load balancing.
5552  */
5553 struct sd_lb_stats {
5554         struct sched_group *busiest;    /* Busiest group in this sd */
5555         struct sched_group *local;      /* Local group in this sd */
5556         unsigned long total_load;       /* Total load of all groups in sd */
5557         unsigned long total_capacity;   /* Total capacity of all groups in sd */
5558         unsigned long avg_load; /* Average load across all groups in sd */
5559 
5560         struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5561         struct sg_lb_stats local_stat;  /* Statistics of the local group */
5562 };
5563 
5564 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
5565 {
5566         /*
5567          * Skimp on the clearing to avoid duplicate work. We can avoid clearing
5568          * local_stat because update_sg_lb_stats() does a full clear/assignment.
5569          * We must however clear busiest_stat::avg_load because
5570          * update_sd_pick_busiest() reads this before assignment.
5571          */
5572         *sds = (struct sd_lb_stats){
5573                 .busiest = NULL,
5574                 .local = NULL,
5575                 .total_load = 0UL,
5576                 .total_capacity = 0UL,
5577                 .busiest_stat = {
5578                         .avg_load = 0UL,
5579                 },
5580         };
5581 }
5582 
5583 /**
5584  * get_sd_load_idx - Obtain the load index for a given sched domain.
5585  * @sd: The sched_domain whose load_idx is to be obtained.
5586  * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5587  *
5588  * Return: The load index.
5589  */
5590 static inline int get_sd_load_idx(struct sched_domain *sd,
5591                                         enum cpu_idle_type idle)
5592 {
5593         int load_idx;
5594 
5595         switch (idle) {
5596         case CPU_NOT_IDLE:
5597                 load_idx = sd->busy_idx;
5598                 break;
5599 
5600         case CPU_NEWLY_IDLE:
5601                 load_idx = sd->newidle_idx;
5602                 break;
5603         default:
5604                 load_idx = sd->idle_idx;
5605                 break;
5606         }
5607 
5608         return load_idx;
5609 }
5610 
5611 static unsigned long default_scale_capacity(struct sched_domain *sd, int cpu)
5612 {
5613         return SCHED_CAPACITY_SCALE;
5614 }
5615 
5616 unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu)
5617 {
5618         return default_scale_capacity(sd, cpu);
5619 }
5620 
5621 static unsigned long default_scale_smt_capacity(struct sched_domain *sd, int cpu)
5622 {
5623         unsigned long weight = sd->span_weight;
5624         unsigned long smt_gain = sd->smt_gain;
5625 
5626         smt_gain /= weight;
5627 
5628         return smt_gain;
5629 }
5630 
5631 unsigned long __weak arch_scale_smt_capacity(struct sched_domain *sd, int cpu)
5632 {
5633         return default_scale_smt_capacity(sd, cpu);
5634 }
5635 
5636 static unsigned long scale_rt_capacity(int cpu)
5637 {
5638         struct rq *rq = cpu_rq(cpu);
5639         u64 total, available, age_stamp, avg;
5640         s64 delta;
5641 
5642         /*
5643          * Since we're reading these variables without serialization make sure
5644          * we read them once before doing sanity checks on them.
5645          */
5646         age_stamp = ACCESS_ONCE(rq->age_stamp);
5647         avg = ACCESS_ONCE(rq->rt_avg);
5648 
5649         delta = rq_clock(rq) - age_stamp;
5650         if (unlikely(delta < 0))
5651                 delta = 0;
5652 
5653         total = sched_avg_period() + delta;
5654 
5655         if (unlikely(total < avg)) {
5656                 /* Ensures that capacity won't end up being negative */
5657                 available = 0;
5658         } else {
5659                 available = total - avg;
5660         }
5661 
5662         if (unlikely((s64)total < SCHED_CAPACITY_SCALE))
5663                 total = SCHED_CAPACITY_SCALE;
5664 
5665         total >>= SCHED_CAPACITY_SHIFT;
5666 
5667         return div_u64(available, total);
5668 }
5669 
5670 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
5671 {
5672         unsigned long weight = sd->span_weight;
5673         unsigned long capacity = SCHED_CAPACITY_SCALE;
5674         struct sched_group *sdg = sd->groups;
5675 
5676         if ((sd->flags & SD_SHARE_CPUCAPACITY) && weight > 1) {
5677                 if (sched_feat(ARCH_CAPACITY))
5678                         capacity *= arch_scale_smt_capacity(sd, cpu);
5679                 else
5680                         capacity *= default_scale_smt_capacity(sd, cpu);
5681 
5682                 capacity >>= SCHED_CAPACITY_SHIFT;
5683         }
5684 
5685         sdg->sgc->capacity_orig = capacity;
5686 
5687         if (sched_feat(ARCH_CAPACITY))
5688                 capacity *= arch_scale_freq_capacity(sd, cpu);
5689         else
5690                 capacity *= default_scale_capacity(sd, cpu);
5691 
5692         capacity >>= SCHED_CAPACITY_SHIFT;
5693 
5694         capacity *= scale_rt_capacity(cpu);
5695         capacity >>= SCHED_CAPACITY_SHIFT;
5696 
5697         if (!capacity)
5698                 capacity = 1;
5699 
5700         cpu_rq(cpu)->cpu_capacity = capacity;
5701         sdg->sgc->capacity = capacity;
5702 }
5703 
5704 void update_group_capacity(struct sched_domain *sd, int cpu)
5705 {
5706         struct sched_domain *child = sd->child;
5707         struct sched_group *group, *sdg = sd->groups;
5708         unsigned long capacity, capacity_orig;
5709         unsigned long interval;
5710 
5711         interval = msecs_to_jiffies(sd->balance_interval);
5712         interval = clamp(interval, 1UL, max_load_balance_interval);
5713         sdg->sgc->next_update = jiffies + interval;
5714 
5715         if (!child) {
5716                 update_cpu_capacity(sd, cpu);
5717                 return;
5718         }
5719 
5720         capacity_orig = capacity = 0;
5721 
5722         if (child->flags & SD_OVERLAP) {
5723                 /*
5724                  * SD_OVERLAP domains cannot assume that child groups
5725                  * span the current group.
5726                  */
5727 
5728                 for_each_cpu(cpu, sched_group_cpus(sdg)) {
5729                         struct sched_group_capacity *sgc;
5730                         struct rq *rq = cpu_rq(cpu);
5731 
5732                         /*
5733                          * build_sched_domains() -> init_sched_groups_capacity()
5734                          * gets here before we've attached the domains to the
5735                          * runqueues.
5736                          *
5737                          * Use capacity_of(), which is set irrespective of domains
5738                          * in update_cpu_capacity().
5739                          *
5740                          * This avoids capacity/capacity_orig from being 0 and
5741                          * causing divide-by-zero issues on boot.
5742                          *
5743                          * Runtime updates will correct capacity_orig.
5744                          */
5745                         if (unlikely(!rq->sd)) {
5746                                 capacity_orig += capacity_of(cpu);
5747                                 capacity += capacity_of(cpu);
5748                                 continue;
5749                         }
5750 
5751                         sgc = rq->sd->groups->sgc;
5752                         capacity_orig += sgc->capacity_orig;
5753                         capacity += sgc->capacity;
5754                 }
5755         } else  {
5756                 /*
5757                  * !SD_OVERLAP domains can assume that child groups
5758                  * span the current group.
5759                  */ 
5760 
5761                 group = child->groups;
5762                 do {
5763                         capacity_orig += group->sgc->capacity_orig;
5764                         capacity += group->sgc->capacity;
5765                         group = group->next;
5766                 } while (group != child->groups);
5767         }
5768 
5769         sdg->sgc->capacity_orig = capacity_orig;
5770         sdg->sgc->capacity = capacity;
5771 }
5772 
5773 /*
5774  * Try and fix up capacity for tiny siblings, this is needed when
5775  * things like SD_ASYM_PACKING need f_b_g to select another sibling
5776  * which on its own isn't powerful enough.
5777  *
5778  * See update_sd_pick_busiest() and check_asym_packing().
5779  */
5780 static inline int
5781 fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
5782 {
5783         /*
5784          * Only siblings can have significantly less than SCHED_CAPACITY_SCALE
5785          */
5786         if (!(sd->flags & SD_SHARE_CPUCAPACITY))
5787                 return 0;
5788 
5789         /*
5790          * If ~90% of the cpu_capacity is still there, we're good.
5791          */
5792         if (group->sgc->capacity * 32 > group->sgc->capacity_orig * 29)
5793                 return 1;
5794 
5795         return 0;
5796 }
5797 
5798 /*
5799  * Group imbalance indicates (and tries to solve) the problem where balancing
5800  * groups is inadequate due to tsk_cpus_allowed() constraints.
5801  *
5802  * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
5803  * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
5804  * Something like:
5805  *
5806  *      { 0 1 2 3 } { 4 5 6 7 }
5807  *              *     * * *
5808  *
5809  * If we were to balance group-wise we'd place two tasks in the first group and
5810  * two tasks in the second group. Clearly this is undesired as it will overload
5811  * cpu 3 and leave one of the cpus in the second group unused.
5812  *
5813  * The current solution to this issue is detecting the skew in the first group
5814  * by noticing the lower domain failed to reach balance and had difficulty
5815  * moving tasks due to affinity constraints.
5816  *
5817  * When this is so detected; this group becomes a candidate for busiest; see
5818  * update_sd_pick_busiest(). And calculate_imbalance() and
5819  * find_busiest_group() avoid some of the usual balance conditions to allow it
5820  * to create an effective group imbalance.
5821  *
5822  * This is a somewhat tricky proposition since the next run might not find the
5823  * group imbalance and decide the groups need to be balanced again. A most
5824  * subtle and fragile situation.
5825  */
5826 
5827 static inline int sg_imbalanced(struct sched_group *group)
5828 {
5829         return group->sgc->imbalance;
5830 }
5831 
5832 /*
5833  * Compute the group capacity factor.
5834  *
5835  * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by
5836  * first dividing out the smt factor and computing the actual number of cores
5837  * and limit unit capacity with that.
5838  */
5839 static inline int sg_capacity_factor(struct lb_env *env, struct sched_group *group)
5840 {
5841         unsigned int capacity_factor, smt, cpus;
5842         unsigned int capacity, capacity_orig;
5843 
5844         capacity = group->sgc->capacity;
5845         capacity_orig = group->sgc->capacity_orig;
5846         cpus = group->group_weight;
5847 
5848         /* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */
5849         smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, capacity_orig);
5850         capacity_factor = cpus / smt; /* cores */
5851 
5852         capacity_factor = min_t(unsigned,
5853                 capacity_factor, DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE));
5854         if (!capacity_factor)
5855                 capacity_factor = fix_small_capacity(env->sd, group);
5856 
5857         return capacity_factor;
5858 }
5859 
5860 /**
5861  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
5862  * @env: The load balancing environment.
5863  * @group: sched_group whose statistics are to be updated.
5864  * @load_idx: Load index of sched_domain of this_cpu for load calc.
5865  * @local_group: Does group contain this_cpu.
5866  * @sgs: variable to hold the statistics for this group.
5867  */
5868 static inline void update_sg_lb_stats(struct lb_env *env,
5869                         struct sched_group *group, int load_idx,
5870                         int local_group, struct sg_lb_stats *sgs)
5871 {
5872         unsigned long load;
5873         int i;
5874 
5875         memset(sgs, 0, sizeof(*sgs));
5876 
5877         for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5878                 struct rq *rq = cpu_rq(i);
5879 
5880                 /* Bias balancing toward cpus of our domain */
5881                 if (local_group)
5882                         load = target_load(i, load_idx);
5883                 else
5884                         load = source_load(i, load_idx);
5885 
5886                 sgs->group_load += load;
5887                 sgs->sum_nr_running += rq->nr_running;
5888 #ifdef CONFIG_NUMA_BALANCING
5889                 sgs->nr_numa_running += rq->nr_numa_running;
5890                 sgs->nr_preferred_running += rq->nr_preferred_running;
5891 #endif
5892                 sgs->sum_weighted_load += weighted_cpuload(i);
5893                 if (idle_cpu(i))
5894                         sgs->idle_cpus++;
5895         }
5896 
5897         /* Adjust by relative CPU capacity of the group */
5898         sgs->group_capacity = group->sgc->capacity;
5899         sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
5900 
5901         if (sgs->sum_nr_running)
5902                 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
5903 
5904         sgs->group_weight = group->group_weight;
5905 
5906         sgs->group_imb = sg_imbalanced(group);
5907         sgs->group_capacity_factor = sg_capacity_factor(env, group);
5908 
5909         if (sgs->group_capacity_factor > sgs->sum_nr_running)
5910                 sgs->group_has_free_capacity = 1;
5911 }
5912 
5913 /**
5914  * update_sd_pick_busiest - return 1 on busiest group
5915  * @env: The load balancing environment.
5916  * @sds: sched_domain statistics
5917  * @sg: sched_group candidate to be checked for being the busiest
5918  * @sgs: sched_group statistics
5919  *
5920  * Determine if @sg is a busier group than the previously selected
5921  * busiest group.
5922  *
5923  * Return: %true if @sg is a busier group than the previously selected
5924  * busiest group. %false otherwise.
5925  */
5926 static bool update_sd_pick_busiest(struct lb_env *env,
5927                                    struct sd_lb_stats *sds,
5928                                    struct sched_group *sg,
5929                                    struct sg_lb_stats *sgs)
5930 {
5931         if (sgs->avg_load <= sds->busiest_stat.avg_load)
5932                 return false;
5933 
5934         if (sgs->sum_nr_running > sgs->group_capacity_factor)
5935                 return true;
5936 
5937         if (sgs->group_imb)
5938                 return true;
5939 
5940         /*
5941          * ASYM_PACKING needs to move all the work to the lowest
5942          * numbered CPUs in the group, therefore mark all groups
5943          * higher than ourself as busy.
5944          */
5945         if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
5946             env->dst_cpu < group_first_cpu(sg)) {
5947                 if (!sds->busiest)
5948                         return true;
5949 
5950                 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
5951                         return true;
5952         }
5953 
5954         return false;
5955 }
5956 
5957 #ifdef CONFIG_NUMA_BALANCING
5958 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
5959 {
5960         if (sgs->sum_nr_running > sgs->nr_numa_running)
5961                 return regular;
5962         if (sgs->sum_nr_running > sgs->nr_preferred_running)
5963                 return remote;
5964         return all;
5965 }
5966 
5967 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
5968 {
5969         if (rq->nr_running > rq->nr_numa_running)
5970                 return regular;
5971         if (rq->nr_running > rq->nr_preferred_running)
5972                 return remote;
5973         return all;
5974 }
5975 #else
5976 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
5977 {
5978         return all;
5979 }
5980 
5981 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
5982 {
5983         return regular;
5984 }
5985 #endif /* CONFIG_NUMA_BALANCING */
5986 
5987 /**
5988  * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
5989  * @env: The load balancing environment.
5990  * @sds: variable to hold the statistics for this sched_domain.
5991  */
5992 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
5993 {
5994         struct sched_domain *child = env->sd->child;
5995         struct sched_group *sg = env->sd->groups;
5996         struct sg_lb_stats tmp_sgs;
5997         int load_idx, prefer_sibling = 0;
5998 
5999         if (child && child->flags & SD_PREFER_SIBLING)
6000                 prefer_sibling = 1;
6001 
6002         load_idx = get_sd_load_idx(env->sd, env->idle);
6003 
6004         do {
6005                 struct sg_lb_stats *sgs = &tmp_sgs;
6006                 int local_group;
6007 
6008                 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6009                 if (local_group) {
6010                         sds->local = sg;
6011                         sgs = &sds->local_stat;
6012 
6013                         if (env->idle != CPU_NEWLY_IDLE ||
6014                             time_after_eq(jiffies, sg->sgc->next_update))
6015                                 update_group_capacity(env->sd, env->dst_cpu);
6016                 }
6017 
6018                 update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
6019 
6020                 if (local_group)
6021                         goto next_group;
6022 
6023                 /*
6024                  * In case the child domain prefers tasks go to siblings
6025                  * first, lower the sg capacity factor to one so that we'll try
6026                  * and move all the excess tasks away. We lower the capacity
6027                  * of a group only if the local group has the capacity to fit
6028                  * these excess tasks, i.e. nr_running < group_capacity_factor. The
6029                  * extra check prevents the case where you always pull from the
6030                  * heaviest group when it is already under-utilized (possible
6031                  * with a large weight task outweighs the tasks on the system).
6032                  */
6033                 if (prefer_sibling && sds->local &&
6034                     sds->local_stat.group_has_free_capacity)
6035                         sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U);
6036 
6037                 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6038                         sds->busiest = sg;
6039                         sds->busiest_stat = *sgs;
6040                 }
6041 
6042 next_group:
6043                 /* Now, start updating sd_lb_stats */
6044                 sds->total_load += sgs->group_load;
6045                 sds->total_capacity += sgs->group_capacity;
6046 
6047                 sg = sg->next;
6048         } while (sg != env->sd->groups);
6049 
6050         if (env->sd->flags & SD_NUMA)
6051                 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6052 }
6053 
6054 /**
6055  * check_asym_packing - Check to see if the group is packed into the
6056  *                      sched doman.
6057  *
6058  * This is primarily intended to used at the sibling level.  Some
6059  * cores like POWER7 prefer to use lower numbered SMT threads.  In the
6060  * case of POWER7, it can move to lower SMT modes only when higher
6061  * threads are idle.  When in lower SMT modes, the threads will
6062  * perform better since they share less core resources.  Hence when we
6063  * have idle threads, we want them to be the higher ones.
6064  *
6065  * This packing function is run on idle threads.  It checks to see if
6066  * the busiest CPU in this domain (core in the P7 case) has a higher
6067  * CPU number than the packing function is being run on.  Here we are
6068  * assuming lower CPU number will be equivalent to lower a SMT thread
6069  * number.
6070  *
6071  * Return: 1 when packing is required and a task should be moved to
6072  * this CPU.  The amount of the imbalance is returned in *imbalance.
6073  *
6074  * @env: The load balancing environment.
6075  * @sds: Statistics of the sched_domain which is to be packed
6076  */
6077 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6078 {
6079         int busiest_cpu;
6080 
6081         if (!(env->sd->flags & SD_ASYM_PACKING))
6082                 return 0;
6083 
6084         if (!sds->busiest)
6085                 return 0;
6086 
6087         busiest_cpu = group_first_cpu(sds->busiest);
6088         if (env->dst_cpu > busiest_cpu)
6089                 return 0;
6090 
6091         env->imbalance = DIV_ROUND_CLOSEST(
6092                 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6093                 SCHED_CAPACITY_SCALE);
6094 
6095         return 1;
6096 }
6097 
6098 /**
6099  * fix_small_imbalance - Calculate the minor imbalance that exists
6100  *                      amongst the groups of a sched_domain, during
6101  *                      load balancing.
6102  * @env: The load balancing environment.
6103  * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6104  */
6105 static inline
6106 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6107 {
6108         unsigned long tmp, capa_now = 0, capa_move = 0;
6109         unsigned int imbn = 2;
6110         unsigned long scaled_busy_load_per_task;
6111         struct sg_lb_stats *local, *busiest;
6112 
6113         local = &sds->local_stat;
6114         busiest = &sds->busiest_stat;
6115 
6116         if (!local->sum_nr_running)
6117                 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6118         else if (busiest->load_per_task > local->load_per_task)
6119                 imbn = 1;
6120 
6121         scaled_busy_load_per_task =
6122                 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6123                 busiest->group_capacity;
6124 
6125         if (busiest->avg_load + scaled_busy_load_per_task >=
6126             local->avg_load + (scaled_busy_load_per_task * imbn)) {
6127                 env->imbalance = busiest->load_per_task;
6128                 return;
6129         }
6130 
6131         /*
6132          * OK, we don't have enough imbalance to justify moving tasks,
6133          * however we may be able to increase total CPU capacity used by
6134          * moving them.
6135          */
6136 
6137         capa_now += busiest->group_capacity *
6138                         min(busiest->load_per_task, busiest->avg_load);
6139         capa_now += local->group_capacity *
6140                         min(local->load_per_task, local->avg_load);
6141         capa_now /= SCHED_CAPACITY_SCALE;
6142 
6143         /* Amount of load we'd subtract */
6144         if (busiest->avg_load > scaled_busy_load_per_task) {
6145                 capa_move += busiest->group_capacity *
6146                             min(busiest->load_per_task,
6147                                 busiest->avg_load - scaled_busy_load_per_task);
6148         }
6149 
6150         /* Amount of load we'd add */
6151         if (busiest->avg_load * busiest->group_capacity <
6152             busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6153                 tmp = (busiest->avg_load * busiest->group_capacity) /
6154                       local->group_capacity;
6155         } else {
6156                 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6157                       local->group_capacity;
6158         }
6159         capa_move += local->group_capacity *
6160                     min(local->load_per_task, local->avg_load + tmp);
6161         capa_move /= SCHED_CAPACITY_SCALE;
6162 
6163         /* Move if we gain throughput */
6164         if (capa_move > capa_now)
6165                 env->imbalance = busiest->load_per_task;
6166 }
6167 
6168 /**
6169  * calculate_imbalance - Calculate the amount of imbalance present within the
6170  *                       groups of a given sched_domain during load balance.
6171  * @env: load balance environment
6172  * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6173  */
6174 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6175 {
6176         unsigned long max_pull, load_above_capacity = ~0UL;
6177         struct sg_lb_stats *local, *busiest;
6178 
6179         local = &sds->local_stat;
6180         busiest = &sds->busiest_stat;
6181 
6182         if (busiest->group_imb) {
6183                 /*
6184                  * In the group_imb case we cannot rely on group-wide averages
6185                  * to ensure cpu-load equilibrium, look at wider averages. XXX
6186                  */
6187                 busiest->load_per_task =
6188                         min(busiest->load_per_task, sds->avg_load);
6189         }
6190 
6191         /*
6192          * In the presence of smp nice balancing, certain scenarios can have
6193          * max load less than avg load(as we skip the groups at or below
6194          * its cpu_capacity, while calculating max_load..)
6195          */
6196         if (busiest->avg_load <= sds->avg_load ||
6197             local->avg_load >= sds->avg_load) {
6198                 env->imbalance = 0;
6199                 return fix_small_imbalance(env, sds);
6200         }
6201 
6202         if (!busiest->group_imb) {
6203                 /*
6204                  * Don't want to pull so many tasks that a group would go idle.
6205                  * Except of course for the group_imb case, since then we might
6206                  * have to drop below capacity to reach cpu-load equilibrium.
6207                  */
6208                 load_above_capacity =
6209                         (busiest->sum_nr_running - busiest->group_capacity_factor);
6210 
6211                 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE);
6212                 load_above_capacity /= busiest->group_capacity;
6213         }
6214 
6215         /*
6216          * We're trying to get all the cpus to the average_load, so we don't
6217          * want to push ourselves above the average load, nor do we wish to
6218          * reduce the max loaded cpu below the average load. At the same time,
6219          * we also don't want to reduce the group load below the group capacity
6220          * (so that we can implement power-savings policies etc). Thus we look
6221          * for the minimum possible imbalance.
6222          */
6223         max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6224 
6225         /* How much load to actually move to equalise the imbalance */
6226         env->imbalance = min(
6227                 max_pull * busiest->group_capacity,
6228                 (sds->avg_load - local->avg_load) * local->group_capacity
6229         ) / SCHED_CAPACITY_SCALE;
6230 
6231         /*
6232          * if *imbalance is less than the average load per runnable task
6233          * there is no guarantee that any tasks will be moved so we'll have
6234          * a think about bumping its value to force at least one task to be
6235          * moved
6236          */
6237         if (env->imbalance < busiest->load_per_task)
6238                 return fix_small_imbalance(env, sds);
6239 }
6240 
6241 /******* find_busiest_group() helpers end here *********************/
6242 
6243 /**
6244  * find_busiest_group - Returns the busiest group within the sched_domain
6245  * if there is an imbalance. If there isn't an imbalance, and
6246  * the user has opted for power-savings, it returns a group whose
6247  * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6248  * such a group exists.
6249  *
6250  * Also calculates the amount of weighted load which should be moved
6251  * to restore balance.
6252  *
6253  * @env: The load balancing environment.
6254  *
6255  * Return:      - The busiest group if imbalance exists.
6256  *              - If no imbalance and user has opted for power-savings balance,
6257  *                 return the least loaded group whose CPUs can be
6258  *                 put to idle by rebalancing its tasks onto our group.
6259  */
6260 static struct sched_group *find_busiest_group(struct lb_env *env)
6261 {
6262         struct sg_lb_stats *local, *busiest;
6263         struct sd_lb_stats sds;
6264 
6265         init_sd_lb_stats(&sds);
6266 
6267         /*
6268          * Compute the various statistics relavent for load balancing at
6269          * this level.
6270          */
6271         update_sd_lb_stats(env, &sds);
6272         local = &sds.local_stat;
6273         busiest = &sds.busiest_stat;
6274 
6275         if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6276             check_asym_packing(env, &sds))
6277                 return sds.busiest;
6278 
6279         /* There is no busy sibling group to pull tasks from */
6280         if (!sds.busiest || busiest->sum_nr_running == 0)
6281                 goto out_balanced;
6282 
6283         sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6284                                                 / sds.total_capacity;
6285 
6286         /*
6287          * If the busiest group is imbalanced the below checks don't
6288          * work because they assume all things are equal, which typically
6289          * isn't true due to cpus_allowed constraints and the like.
6290          */
6291         if (busiest->group_imb)
6292                 goto force_balance;
6293 
6294         /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6295         if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity &&
6296             !busiest->group_has_free_capacity)
6297                 goto force_balance;
6298 
6299         /*
6300          * If the local group is more busy than the selected busiest group
6301          * don't try and pull any tasks.
6302          */
6303         if (local->avg_load >= busiest->avg_load)
6304                 goto out_balanced;
6305 
6306         /*
6307          * Don't pull any tasks if this group is already above the domain
6308          * average load.
6309          */
6310         if (local->avg_load >= sds.avg_load)
6311                 goto out_balanced;
6312 
6313         if (env->idle == CPU_IDLE) {
6314                 /*
6315                  * This cpu is idle. If the busiest group load doesn't
6316                  * have more tasks than the number of available cpu's and
6317                  * there is no imbalance between this and busiest group
6318                  * wrt to idle cpu's, it is balanced.
6319                  */
6320                 if ((local->idle_cpus < busiest->idle_cpus) &&
6321                     busiest->sum_nr_running <= busiest->group_weight)
6322                         goto out_balanced;
6323         } else {
6324                 /*
6325                  * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6326                  * imbalance_pct to be conservative.
6327                  */
6328                 if (100 * busiest->avg_load <=
6329                                 env->sd->imbalance_pct * local->avg_load)
6330                         goto out_balanced;
6331         }
6332 
6333 force_balance:
6334         /* Looks like there is an imbalance. Compute it */
6335         calculate_imbalance(env, &sds);
6336         return sds.busiest;
6337 
6338 out_balanced:
6339         env->imbalance = 0;
6340         return NULL;
6341 }
6342 
6343 /*
6344  * find_busiest_queue - find the busiest runqueue among the cpus in group.
6345  */
6346 static struct rq *find_busiest_queue(struct lb_env *env,
6347                                      struct sched_group *group)
6348 {
6349         struct rq *busiest = NULL, *rq;
6350         unsigned long busiest_load = 0, busiest_capacity = 1;
6351         int i;
6352 
6353         for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6354                 unsigned long capacity, capacity_factor, wl;
6355                 enum fbq_type rt;
6356 
6357                 rq = cpu_rq(i);
6358                 rt = fbq_classify_rq(rq);
6359 
6360                 /*
6361                  * We classify groups/runqueues into three groups:
6362                  *  - regular: there are !numa tasks
6363                  *  - remote:  there are numa tasks that run on the 'wrong' node
6364                  *  - all:     there is no distinction
6365                  *
6366                  * In order to avoid migrating ideally placed numa tasks,
6367                  * ignore those when there's better options.
6368                  *
6369                  * If we ignore the actual busiest queue to migrate another
6370                  * task, the next balance pass can still reduce the busiest
6371                  * queue by moving tasks around inside the node.
6372                  *
6373                  * If we cannot move enough load due to this classification
6374                  * the next pass will adjust the group classification and
6375                  * allow migration of more tasks.
6376                  *
6377                  * Both cases only affect the total convergence complexity.
6378                  */
6379                 if (rt > env->fbq_type)
6380                         continue;
6381 
6382                 capacity = capacity_of(i);
6383                 capacity_factor = DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE);
6384                 if (!capacity_factor)
6385                         capacity_factor = fix_small_capacity(env->sd, group);
6386 
6387                 wl = weighted_cpuload(i);
6388 
6389                 /*
6390                  * When comparing with imbalance, use weighted_cpuload()
6391                  * which is not scaled with the cpu capacity.
6392                  */
6393                 if (capacity_factor && rq->nr_running == 1 && wl > env->imbalance)
6394                         continue;
6395 
6396                 /*
6397                  * For the load comparisons with the other cpu's, consider
6398                  * the weighted_cpuload() scaled with the cpu capacity, so
6399                  * that the load can be moved away from the cpu that is
6400                  * potentially running at a lower capacity.
6401                  *
6402                  * Thus we're looking for max(wl_i / capacity_i), crosswise
6403                  * multiplication to rid ourselves of the division works out
6404                  * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
6405                  * our previous maximum.
6406                  */
6407                 if (wl * busiest_capacity > busiest_load * capacity) {
6408                         busiest_load = wl;
6409                         busiest_capacity = capacity;
6410                         busiest = rq;
6411                 }
6412         }
6413 
6414         return busiest;
6415 }
6416 
6417 /*
6418  * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6419  * so long as it is large enough.
6420  */
6421 #define MAX_PINNED_INTERVAL     512
6422 
6423 /* Working cpumask for load_balance and load_balance_newidle. */
6424 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6425 
6426 static int need_active_balance(struct lb_env *env)
6427 {
6428         struct sched_domain *sd = env->sd;
6429 
6430         if (env->idle == CPU_NEWLY_IDLE) {
6431 
6432                 /*
6433                  * ASYM_PACKING needs to force migrate tasks from busy but
6434                  * higher numbered CPUs in order to pack all tasks in the
6435                  * lowest numbered CPUs.
6436                  */
6437                 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6438                         return 1;
6439         }
6440 
6441         return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6442 }
6443 
6444 static int active_load_balance_cpu_stop(void *data);
6445 
6446 static int should_we_balance(struct lb_env *env)
6447 {
6448         struct sched_group *sg = env->sd->groups;
6449         struct cpumask *sg_cpus, *sg_mask;
6450         int cpu, balance_cpu = -1;
6451 
6452         /*
6453          * In the newly idle case, we will allow all the cpu's
6454          * to do the newly idle load balance.
6455          */
6456         if (env->idle == CPU_NEWLY_IDLE)
6457                 return 1;
6458 
6459         sg_cpus = sched_group_cpus(sg);
6460         sg_mask = sched_group_mask(sg);
6461         /* Try to find first idle cpu */
6462         for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6463                 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6464                         continue;
6465 
6466                 balance_cpu = cpu;
6467                 break;
6468         }
6469 
6470         if (balance_cpu == -1)
6471                 balance_cpu = group_balance_cpu(sg);
6472 
6473         /*
6474          * First idle cpu or the first cpu(busiest) in this sched group
6475          * is eligible for doing load balancing at this and above domains.
6476          */
6477         return balance_cpu == env->dst_cpu;
6478 }
6479 
6480 /*
6481  * Check this_cpu to ensure it is balanced within domain. Attempt to move
6482  * tasks if there is an imbalance.
6483  */
6484 static int load_balance(int this_cpu, struct rq *this_rq,
6485                         struct sched_domain *sd, enum cpu_idle_type idle,
6486                         int *continue_balancing)
6487 {
6488         int ld_moved, cur_ld_moved, active_balance = 0;
6489         struct sched_domain *sd_parent = sd->parent;
6490         struct sched_group *group;
6491         struct rq *busiest;
6492         unsigned long flags;
6493         struct cpumask *cpus = __get_cpu_var(load_balance_mask);
6494 
6495         struct lb_env env = {
6496                 .sd             = sd,
6497                 .dst_cpu        = this_cpu,
6498                 .dst_rq         = this_rq,
6499                 .dst_grpmask    = sched_group_cpus(sd->groups),
6500                 .idle           = idle,
6501                 .loop_break     = sched_nr_migrate_break,
6502                 .cpus           = cpus,
6503                 .fbq_type       = all,
6504         };
6505 
6506         /*
6507          * For NEWLY_IDLE load_balancing, we don't need to consider
6508          * other cpus in our group
6509          */
6510         if (idle == CPU_NEWLY_IDLE)
6511                 env.dst_grpmask = NULL;
6512 
6513         cpumask_copy(cpus, cpu_active_mask);
6514 
6515         schedstat_inc(sd, lb_count[idle]);
6516 
6517 redo:
6518         if (!should_we_balance(&env)) {
6519                 *continue_balancing = 0;
6520                 goto out_balanced;
6521         }
6522 
6523         group = find_busiest_group(&env);
6524         if (!group) {
6525                 schedstat_inc(sd, lb_nobusyg[idle]);
6526                 goto out_balanced;
6527         }
6528 
6529         busiest = find_busiest_queue(&env, group);
6530         if (!busiest) {
6531                 schedstat_inc(sd, lb_nobusyq[idle]);
6532                 goto out_balanced;
6533         }
6534 
6535         BUG_ON(busiest == env.dst_rq);
6536 
6537         schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6538 
6539         ld_moved = 0;
6540         if (busiest->nr_running > 1) {
6541                 /*
6542                  * Attempt to move tasks. If find_busiest_group has found
6543                  * an imbalance but busiest->nr_running <= 1, the group is
6544                  * still unbalanced. ld_moved simply stays zero, so it is
6545                  * correctly treated as an imbalance.
6546                  */
6547                 env.flags |= LBF_ALL_PINNED;
6548                 env.src_cpu   = busiest->cpu;
6549                 env.src_rq    = busiest;
6550                 env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6551 
6552 more_balance:
6553                 local_irq_save(flags);
6554                 double_rq_lock(env.dst_rq, busiest);
6555 
6556                 /*
6557                  * cur_ld_moved - load moved in current iteration
6558                  * ld_moved     - cumulative load moved across iterations
6559                  */
6560                 cur_ld_moved = move_tasks(&env);
6561                 ld_moved += cur_ld_moved;
6562                 double_rq_unlock(env.dst_rq, busiest);
6563                 local_irq_restore(flags);
6564 
6565                 /*
6566                  * some other cpu did the load balance for us.
6567                  */
6568                 if (cur_ld_moved && env.dst_cpu != smp_processor_id())
6569                         resched_cpu(env.dst_cpu);
6570 
6571                 if (env.flags & LBF_NEED_BREAK) {
6572                         env.flags &= ~LBF_NEED_BREAK;
6573                         goto more_balance;
6574                 }
6575 
6576                 /*
6577                  * Revisit (affine) tasks on src_cpu that couldn't be moved to
6578                  * us and move them to an alternate dst_cpu in our sched_group
6579                  * where they can run. The upper limit on how many times we
6580                  * iterate on same src_cpu is dependent on number of cpus in our
6581                  * sched_group.
6582                  *
6583                  * This changes load balance semantics a bit on who can move
6584                  * load to a given_cpu. In addition to the given_cpu itself
6585                  * (or a ilb_cpu acting on its behalf where given_cpu is
6586                  * nohz-idle), we now have balance_cpu in a position to move
6587                  * load to given_cpu. In rare situations, this may cause
6588                  * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
6589                  * _independently_ and at _same_ time to move some load to
6590                  * given_cpu) causing exceess load to be moved to given_cpu.
6591                  * This however should not happen so much in practice and
6592                  * moreover subsequent load balance cycles should correct the
6593                  * excess load moved.
6594                  */
6595                 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6596 
6597                         /* Prevent to re-select dst_cpu via env's cpus */
6598                         cpumask_clear_cpu(env.dst_cpu, env.cpus);
6599 
6600                         env.dst_rq       = cpu_rq(env.new_dst_cpu);
6601                         env.dst_cpu      = env.new_dst_cpu;
6602                         env.flags       &= ~LBF_DST_PINNED;
6603                         env.loop         = 0;
6604                         env.loop_break   = sched_nr_migrate_break;
6605 
6606                         /*
6607                          * Go back to "more_balance" rather than "redo" since we
6608                          * need to continue with same src_cpu.
6609                          */
6610                         goto more_balance;
6611                 }
6612 
6613                 /*
6614                  * We failed to reach balance because of affinity.
6615                  */
6616                 if (sd_parent) {
6617                         int *group_imbalance = &sd_parent->groups->sgc->imbalance;
6618 
6619                         if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
6620                                 *group_imbalance = 1;
6621                         } else if (*group_imbalance)
6622                                 *group_imbalance = 0;
6623                 }
6624 
6625                 /* All tasks on this runqueue were pinned by CPU affinity */
6626                 if (unlikely(env.flags & LBF_ALL_PINNED)) {
6627                         cpumask_clear_cpu(cpu_of(busiest), cpus);
6628                         if (!cpumask_empty(cpus)) {
6629                                 env.loop = 0;
6630                                 env.loop_break = sched_nr_migrate_break;
6631                                 goto redo;
6632                         }
6633                         goto out_balanced;
6634                 }
6635         }
6636 
6637         if (!ld_moved) {
6638                 schedstat_inc(sd, lb_failed[idle]);
6639                 /*
6640                  * Increment the failure counter only on periodic balance.
6641                  * We do not want newidle balance, which can be very
6642                  * frequent, pollute the failure counter causing
6643                  * excessive cache_hot migrations and active balances.
6644                  */
6645                 if (idle != CPU_NEWLY_IDLE)
6646                         sd->nr_balance_failed++;
6647 
6648                 if (need_active_balance(&env)) {
6649                         raw_spin_lock_irqsave(&busiest->lock, flags);
6650 
6651                         /* don't kick the active_load_balance_cpu_stop,
6652                          * if the curr task on busiest cpu can't be
6653                          * moved to this_cpu
6654                          */
6655                         if (!cpumask_test_cpu(this_cpu,
6656                                         tsk_cpus_allowed(busiest->curr))) {
6657                                 raw_spin_unlock_irqrestore(&busiest->lock,
6658                                                             flags);
6659                                 env.flags |= LBF_ALL_PINNED;
6660                                 goto out_one_pinned;
6661                         }
6662 
6663                         /*
6664                          * ->active_balance synchronizes accesses to
6665                          * ->active_balance_work.  Once set, it's cleared
6666                          * only after active load balance is finished.
6667                          */
6668                         if (!busiest->active_balance) {
6669                                 busiest->active_balance = 1;
6670                                 busiest->push_cpu = this_cpu;
6671                                 active_balance = 1;
6672                         }
6673                         raw_spin_unlock_irqrestore(&busiest->lock, flags);
6674 
6675                         if (active_balance) {
6676                                 stop_one_cpu_nowait(cpu_of(busiest),
6677                                         active_load_balance_cpu_stop, busiest,
6678                                         &busiest->active_balance_work);
6679                         }
6680 
6681                         /*
6682                          * We've kicked active balancing, reset the failure
6683                          * counter.
6684                          */
6685                         sd->nr_balance_failed = sd->cache_nice_tries+1;
6686                 }
6687         } else
6688                 sd->nr_balance_failed = 0;
6689 
6690         if (likely(!active_balance)) {
6691                 /* We were unbalanced, so reset the balancing interval */
6692                 sd->balance_interval = sd->min_interval;
6693         } else {
6694                 /*
6695                  * If we've begun active balancing, start to back off. This
6696                  * case may not be covered by the all_pinned logic if there
6697                  * is only 1 task on the busy runqueue (because we don't call
6698                  * move_tasks).
6699                  */
6700                 if (sd->balance_interval < sd->max_interval)
6701                         sd->balance_interval *= 2;
6702         }
6703 
6704         goto out;
6705 
6706 out_balanced:
6707         schedstat_inc(sd, lb_balanced[idle]);
6708 
6709         sd->nr_balance_failed = 0;
6710 
6711 out_one_pinned:
6712         /* tune up the balancing interval */
6713         if (((env.flags & LBF_ALL_PINNED) &&
6714                         sd->balance_interval < MAX_PINNED_INTERVAL) ||
6715                         (sd->balance_interval < sd->max_interval))
6716                 sd->balance_interval *= 2;
6717 
6718         ld_moved = 0;
6719 out:
6720         return ld_moved;
6721 }
6722 
6723 static inline unsigned long
6724 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
6725 {
6726         unsigned long interval = sd->balance_interval;
6727 
6728         if (cpu_busy)
6729                 interval *= sd->busy_factor;
6730 
6731         /* scale ms to jiffies */
6732         interval = msecs_to_jiffies(interval);
6733         interval = clamp(interval, 1UL, max_load_balance_interval);
6734 
6735         return interval;
6736 }
6737 
6738 static inline void
6739 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
6740 {
6741         unsigned long interval, next;
6742 
6743         interval = get_sd_balance_interval(sd, cpu_busy);
6744         next = sd->last_balance + interval;
6745 
6746         if (time_after(*next_balance, next))
6747                 *next_balance = next;
6748 }
6749 
6750 /*
6751  * idle_balance is called by schedule() if this_cpu is about to become
6752  * idle. Attempts to pull tasks from other CPUs.
6753  */
6754 static int idle_balance(struct rq *this_rq)
6755 {
6756         unsigned long next_balance = jiffies + HZ;
6757         int this_cpu = this_rq->cpu;
6758         struct sched_domain *sd;
6759         int pulled_task = 0;
6760         u64 curr_cost = 0;
6761 
6762         idle_enter_fair(this_rq);
6763 
6764         /*
6765          * We must set idle_stamp _before_ calling idle_balance(), such that we
6766          * measure the duration of idle_balance() as idle time.
6767          */
6768         this_rq->idle_stamp = rq_clock(this_rq);
6769 
6770         if (this_rq->avg_idle < sysctl_sched_migration_cost) {
6771                 rcu_read_lock();
6772                 sd = rcu_dereference_check_sched_domain(this_rq->sd);
6773                 if (sd)
6774                         update_next_balance(sd, 0, &next_balance);
6775                 rcu_read_unlock();
6776 
6777                 goto out;
6778         }
6779 
6780         /*
6781          * Drop the rq->lock, but keep IRQ/preempt disabled.
6782          */
6783         raw_spin_unlock(&this_rq->lock);
6784 
6785         update_blocked_averages(this_cpu);
6786         rcu_read_lock();
6787         for_each_domain(this_cpu, sd) {
6788                 int continue_balancing = 1;
6789                 u64 t0, domain_cost;
6790 
6791                 if (!(sd->flags & SD_LOAD_BALANCE))
6792                         continue;
6793 
6794                 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
6795                         update_next_balance(sd, 0, &next_balance);
6796                         break;
6797                 }
6798 
6799                 if (sd->flags & SD_BALANCE_NEWIDLE) {
6800                         t0 = sched_clock_cpu(this_cpu);
6801 
6802                         pulled_task = load_balance(this_cpu, this_rq,
6803                                                    sd, CPU_NEWLY_IDLE,
6804                                                    &continue_balancing);
6805 
6806                         domain_cost = sched_clock_cpu(this_cpu) - t0;
6807                         if (domain_cost > sd->max_newidle_lb_cost)
6808                                 sd->max_newidle_lb_cost = domain_cost;
6809 
6810                         curr_cost += domain_cost;
6811                 }
6812 
6813                 update_next_balance(sd, 0, &next_balance);
6814 
6815                 /*
6816                  * Stop searching for tasks to pull if there are
6817                  * now runnable tasks on this rq.
6818                  */
6819                 if (pulled_task || this_rq->nr_running > 0)
6820                         break;
6821         }
6822         rcu_read_unlock();
6823 
6824         raw_spin_lock(&this_rq->lock);
6825 
6826         if (curr_cost > this_rq->max_idle_balance_cost)
6827                 this_rq->max_idle_balance_cost = curr_cost;
6828 
6829         /*
6830          * While browsing the domains, we released the rq lock, a task could
6831          * have been enqueued in the meantime. Since we're not going idle,
6832          * pretend we pulled a task.
6833          */
6834         if (this_rq->cfs.h_nr_running && !pulled_task)
6835                 pulled_task = 1;
6836 
6837 out:
6838         /* Move the next balance forward */
6839         if (time_after(this_rq->next_balance, next_balance))
6840                 this_rq->next_balance = next_balance;
6841 
6842         /* Is there a task of a high priority class? */
6843         if (this_rq->nr_running != this_rq->cfs.h_nr_running)
6844                 pulled_task = -1;
6845 
6846         if (pulled_task) {
6847                 idle_exit_fair(this_rq);
6848                 this_rq->idle_stamp = 0;
6849         }
6850 
6851         return pulled_task;
6852 }
6853 
6854 /*
6855  * active_load_balance_cpu_stop is run by cpu stopper. It pushes
6856  * running tasks off the busiest CPU onto idle CPUs. It requires at
6857  * least 1 task to be running on each physical CPU where possible, and
6858  * avoids physical / logical imbalances.
6859  */
6860 static int active_load_balance_cpu_stop(void *data)
6861 {
6862         struct rq *busiest_rq = data;
6863         int busiest_cpu = cpu_of(busiest_rq);
6864         int target_cpu = busiest_rq->push_cpu;
6865         struct rq *target_rq = cpu_rq(target_cpu);
6866         struct sched_domain *sd;
6867 
6868         raw_spin_lock_irq(&busiest_rq->lock);
6869 
6870         /* make sure the requested cpu hasn't gone down in the meantime */
6871         if (unlikely(busiest_cpu != smp_processor_id() ||
6872                      !busiest_rq->active_balance))
6873                 goto out_unlock;
6874 
6875         /* Is there any task to move? */
6876         if (busiest_rq->nr_running <= 1)
6877                 goto out_unlock;
6878 
6879         /*
6880          * This condition is "impossible", if it occurs
6881          * we need to fix it. Originally reported by
6882          * Bjorn Helgaas on a 128-cpu setup.
6883          */
6884         BUG_ON(busiest_rq == target_rq);
6885 
6886         /* move a task from busiest_rq to target_rq */
6887         double_lock_balance(busiest_rq, target_rq);
6888 
6889         /* Search for an sd spanning us and the target CPU. */
6890         rcu_read_lock();
6891         for_each_domain(target_cpu, sd) {
6892                 if ((sd->flags & SD_LOAD_BALANCE) &&
6893                     cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
6894                                 break;
6895         }
6896 
6897         if (likely(sd)) {
6898                 struct lb_env env = {
6899                         .sd             = sd,
6900                         .dst_cpu        = target_cpu,
6901                         .dst_rq         = target_rq,
6902                         .src_cpu        = busiest_rq->cpu,
6903                         .src_rq         = busiest_rq,
6904                         .idle           = CPU_IDLE,
6905                 };
6906 
6907                 schedstat_inc(sd, alb_count);
6908 
6909                 if (move_one_task(&env))
6910                         schedstat_inc(sd, alb_pushed);
6911                 else
6912                         schedstat_inc(sd, alb_failed);
6913         }
6914         rcu_read_unlock();
6915         double_unlock_balance(busiest_rq, target_rq);
6916 out_unlock:
6917         busiest_rq->active_balance = 0;
6918         raw_spin_unlock_irq(&busiest_rq->lock);
6919         return 0;
6920 }
6921 
6922 static inline int on_null_domain(struct rq *rq)
6923 {
6924         return unlikely(!rcu_dereference_sched(rq->sd));
6925 }
6926 
6927 #ifdef CONFIG_NO_HZ_COMMON
6928 /*
6929  * idle load balancing details
6930  * - When one of the busy CPUs notice that there may be an idle rebalancing
6931  *   needed, they will kick the idle load balancer, which then does idle
6932  *   load balancing for all the idle CPUs.
6933  */
6934 static struct {
6935         cpumask_var_t idle_cpus_mask;
6936         atomic_t nr_cpus;
6937         unsigned long next_balance;     /* in jiffy units */
6938 } nohz ____cacheline_aligned;
6939 
6940 static inline int find_new_ilb(void)
6941 {
6942         int ilb = cpumask_first(nohz.idle_cpus_mask);
6943 
6944         if (ilb < nr_cpu_ids && idle_cpu(ilb))
6945                 return ilb;
6946 
6947         return nr_cpu_ids;
6948 }
6949 
6950 /*
6951  * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
6952  * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
6953  * CPU (if there is one).
6954  */
6955 static void nohz_balancer_kick(void)
6956 {
6957         int ilb_cpu;
6958 
6959         nohz.next_balance++;
6960 
6961         ilb_cpu = find_new_ilb();
6962 
6963         if (ilb_cpu >= nr_cpu_ids)
6964                 return;
6965 
6966         if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
6967                 return;
6968         /*
6969          * Use smp_send_reschedule() instead of resched_cpu().
6970          * This way we generate a sched IPI on the target cpu which
6971          * is idle. And the softirq performing nohz idle load balance
6972          * will be run before returning from the IPI.
6973          */
6974         smp_send_reschedule(ilb_cpu);
6975         return;
6976 }
6977 
6978 static inline void nohz_balance_exit_idle(int cpu)
6979 {
6980         if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
6981                 /*
6982                  * Completely isolated CPUs don't ever set, so we must test.
6983                  */
6984                 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
6985                         cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
6986                         atomic_dec(&nohz.nr_cpus);
6987                 }
6988                 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
6989         }
6990 }
6991 
6992 static inline void set_cpu_sd_state_busy(void)
6993 {
6994         struct sched_domain *sd;
6995         int cpu = smp_processor_id();
6996 
6997         rcu_read_lock();
6998         sd = rcu_dereference(per_cpu(sd_busy, cpu));
6999 
7000         if (!sd || !sd->nohz_idle)
7001                 goto unlock;
7002         sd->nohz_idle = 0;
7003 
7004         atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7005 unlock:
7006         rcu_read_unlock();
7007 }
7008 
7009 void set_cpu_sd_state_idle(void)
7010 {
7011         struct sched_domain *sd;
7012         int cpu = smp_processor_id();
7013 
7014         rcu_read_lock();
7015         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7016 
7017         if (!sd || sd->nohz_idle)
7018                 goto unlock;
7019         sd->nohz_idle = 1;
7020 
7021         atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7022 unlock:
7023         rcu_read_unlock();
7024 }
7025 
7026 /*
7027  * This routine will record that the cpu is going idle with tick stopped.
7028  * This info will be used in performing idle load balancing in the future.
7029  */
7030 void nohz_balance_enter_idle(int cpu)
7031 {
7032         /*
7033          * If this cpu is going down, then nothing needs to be done.
7034          */
7035         if (!cpu_active(cpu))
7036                 return;
7037 
7038         if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7039                 return;
7040 
7041         /*
7042          * If we're a completely isolated CPU, we don't play.
7043          */
7044         if (on_null_domain(cpu_rq(cpu)))
7045                 return;
7046 
7047         cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7048         atomic_inc(&nohz.nr_cpus);
7049         set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7050 }
7051 
7052 static int sched_ilb_notifier(struct notifier_block *nfb,
7053                                         unsigned long action, void *hcpu)
7054 {
7055         switch (action & ~CPU_TASKS_FROZEN) {
7056         case CPU_DYING:
7057                 nohz_balance_exit_idle(smp_processor_id());
7058                 return NOTIFY_OK;
7059         default:
7060                 return NOTIFY_DONE;
7061         }
7062 }
7063 #endif
7064 
7065 static DEFINE_SPINLOCK(balancing);
7066 
7067 /*
7068  * Scale the max load_balance interval with the number of CPUs in the system.
7069  * This trades load-balance latency on larger machines for less cross talk.
7070  */
7071 void update_max_interval(void)
7072 {
7073         max_load_balance_interval = HZ*num_online_cpus()/10;
7074 }
7075 
7076 /*
7077  * It checks each scheduling domain to see if it is due to be balanced,
7078  * and initiates a balancing operation if so.
7079  *
7080  * Balancing parameters are set up in init_sched_domains.
7081  */
7082 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7083 {
7084         int continue_balancing = 1;
7085         int cpu = rq->cpu;
7086         unsigned long interval;
7087         struct sched_domain *sd;
7088         /* Earliest time when we have to do rebalance again */
7089         unsigned long next_balance = jiffies + 60*HZ;
7090         int update_next_balance = 0;
7091         int need_serialize, need_decay = 0;
7092         u64 max_cost = 0;
7093 
7094         update_blocked_averages(cpu);
7095 
7096         rcu_read_lock();
7097         for_each_domain(cpu, sd) {
7098                 /*
7099                  * Decay the newidle max times here because this is a regular
7100                  * visit to all the domains. Decay ~1% per second.
7101                  */
7102                 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7103                         sd->max_newidle_lb_cost =
7104                                 (sd->max_newidle_lb_cost * 253) / 256;
7105                         sd->next_decay_max_lb_cost = jiffies + HZ;
7106                         need_decay = 1;
7107                 }
7108                 max_cost += sd->max_newidle_lb_cost;
7109 
7110                 if (!(sd->flags & SD_LOAD_BALANCE))
7111                         continue;
7112 
7113                 /*
7114                  * Stop the load balance at this level. There is another
7115                  * CPU in our sched group which is doing load balancing more
7116                  * actively.
7117                  */
7118                 if (!continue_balancing) {
7119                         if (need_decay)
7120                                 continue;
7121                         break;
7122                 }
7123 
7124                 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7125 
7126                 need_serialize = sd->flags & SD_SERIALIZE;
7127                 if (need_serialize) {
7128                         if (!spin_trylock(&balancing))
7129                                 goto out;
7130                 }
7131 
7132                 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7133                         if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7134                                 /*
7135                                  * The LBF_DST_PINNED logic could have changed
7136                                  * env->dst_cpu, so we can't know our idle
7137                                  * state even if we migrated tasks. Update it.
7138                                  */
7139                                 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7140                         }
7141                         sd->last_balance = jiffies;
7142                         interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7143                 }
7144                 if (need_serialize)
7145                         spin_unlock(&balancing);
7146 out:
7147                 if (time_after(next_balance, sd->last_balance + interval)) {
7148                         next_balance = sd->last_balance + interval;
7149                         update_next_balance = 1;
7150                 }
7151         }
7152         if (need_decay) {
7153                 /*
7154                  * Ensure the rq-wide value also decays but keep it at a
7155                  * reasonable floor to avoid funnies with rq->avg_idle.
7156                  */
7157                 rq->max_idle_balance_cost =
7158                         max((u64)sysctl_sched_migration_cost, max_cost);
7159         }
7160         rcu_read_unlock();
7161 
7162         /*
7163          * next_balance will be updated only when there is a need.
7164          * When the cpu is attached to null domain for ex, it will not be
7165          * updated.
7166          */
7167         if (likely(update_next_balance))
7168                 rq->next_balance = next_balance;
7169 }
7170 
7171 #ifdef CONFIG_NO_HZ_COMMON
7172 /*
7173  * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7174  * rebalancing for all the cpus for whom scheduler ticks are stopped.
7175  */
7176 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7177 {
7178         int this_cpu = this_rq->cpu;
7179         struct rq *rq;
7180         int balance_cpu;
7181 
7182         if (idle != CPU_IDLE ||
7183             !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7184                 goto end;
7185 
7186         for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7187                 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7188                         continue;
7189 
7190                 /*
7191                  * If this cpu gets work to do, stop the load balancing
7192                  * work being done for other cpus. Next load
7193                  * balancing owner will pick it up.
7194                  */
7195                 if (need_resched())
7196                         break;
7197 
7198                 rq = cpu_rq(balance_cpu);
7199 
7200                 /*
7201                  * If time for next balance is due,
7202                  * do the balance.
7203                  */
7204                 if (time_after_eq(jiffies, rq->next_balance)) {
7205                         raw_spin_lock_irq(&rq->lock);
7206                         update_rq_clock(rq);
7207                         update_idle_cpu_load(rq);
7208                         raw_spin_unlock_irq(&rq->lock);
7209                         rebalance_domains(rq, CPU_IDLE);
7210                 }
7211 
7212                 if (time_after(this_rq->next_balance, rq->next_balance))
7213                         this_rq->next_balance = rq->next_balance;
7214         }
7215         nohz.next_balance = this_rq->next_balance;
7216 end:
7217         clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7218 }
7219 
7220 /*
7221  * Current heuristic for kicking the idle load balancer in the presence
7222  * of an idle cpu is the system.
7223  *   - This rq has more than one task.
7224  *   - At any scheduler domain level, this cpu's scheduler group has multiple
7225  *     busy cpu's exceeding the group's capacity.
7226  *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7227  *     domain span are idle.
7228  */
7229 static inline int nohz_kick_needed(struct rq *rq)
7230 {
7231         unsigned long now = jiffies;
7232         struct sched_domain *sd;
7233         struct sched_group_capacity *sgc;
7234         int nr_busy, cpu = rq->cpu;
7235 
7236         if (unlikely(rq->idle_balance))
7237                 return 0;
7238 
7239        /*
7240         * We may be recently in ticked or tickless idle mode. At the first
7241         * busy tick after returning from idle, we will update the busy stats.
7242         */
7243         set_cpu_sd_state_busy();
7244         nohz_balance_exit_idle(cpu);
7245 
7246         /*
7247          * None are in tickless mode and hence no need for NOHZ idle load
7248          * balancing.
7249          */
7250         if (likely(!atomic_read(&nohz.nr_cpus)))
7251                 return 0;
7252 
7253         if (time_before(now, nohz.next_balance))
7254                 return 0;
7255 
7256         if (rq->nr_running >= 2)
7257                 goto need_kick;
7258 
7259         rcu_read_lock();
7260         sd = rcu_dereference(per_cpu(sd_busy, cpu));
7261 
7262         if (sd) {
7263                 sgc = sd->groups->sgc;
7264                 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7265 
7266                 if (nr_busy > 1)
7267                         goto need_kick_unlock;
7268         }
7269 
7270         sd = rcu_dereference(per_cpu(sd_asym, cpu));
7271 
7272         if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7273                                   sched_domain_span(sd)) < cpu))
7274                 goto need_kick_unlock;
7275 
7276         rcu_read_unlock();
7277         return 0;
7278 
7279 need_kick_unlock:
7280         rcu_read_unlock();
7281 need_kick:
7282         return 1;
7283 }
7284 #else
7285 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7286 #endif
7287 
7288 /*
7289  * run_rebalance_domains is triggered when needed from the scheduler tick.
7290  * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7291  */
7292 static void run_rebalance_domains(struct softirq_action *h)
7293 {
7294         struct rq *this_rq = this_rq();
7295         enum cpu_idle_type idle = this_rq->idle_balance ?
7296                                                 CPU_IDLE : CPU_NOT_IDLE;
7297 
7298         rebalance_domains(this_rq, idle);
7299 
7300         /*
7301          * If this cpu has a pending nohz_balance_kick, then do the
7302          * balancing on behalf of the other idle cpus whose ticks are
7303          * stopped.
7304          */
7305         nohz_idle_balance(this_rq, idle);
7306 }
7307 
7308 /*
7309  * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7310  */
7311 void trigger_load_balance(struct rq *rq)
7312 {
7313         /* Don't need to rebalance while attached to NULL domain */
7314         if (unlikely(on_null_domain(rq)))
7315                 return;
7316 
7317         if (time_after_eq(jiffies, rq->next_balance))
7318                 raise_softirq(SCHED_SOFTIRQ);
7319 #ifdef CONFIG_NO_HZ_COMMON
7320         if (nohz_kick_needed(rq))
7321                 nohz_balancer_kick();
7322 #endif
7323 }
7324 
7325 static void rq_online_fair(struct rq *rq)
7326 {
7327         update_sysctl();
7328 }
7329 
7330 static void rq_offline_fair(struct rq *rq)
7331 {
7332         update_sysctl();
7333 
7334         /* Ensure any throttled groups are reachable by pick_next_task */
7335         unthrottle_offline_cfs_rqs(rq);
7336 }
7337 
7338 #endif /* CONFIG_SMP */
7339 
7340 /*
7341  * scheduler tick hitting a task of our scheduling class:
7342  */
7343 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7344 {
7345         struct cfs_rq *cfs_rq;
7346         struct sched_entity *se = &curr->se;
7347 
7348         for_each_sched_entity(se) {
7349                 cfs_rq = cfs_rq_of(se);
7350                 entity_tick(cfs_rq, se, queued);
7351         }
7352 
7353         if (numabalancing_enabled)
7354                 task_tick_numa(rq, curr);
7355 
7356         update_rq_runnable_avg(rq, 1);
7357 }
7358 
7359 /*
7360  * called on fork with the child task as argument from the parent's context
7361  *  - child not yet on the tasklist
7362  *  - preemption disabled
7363  */
7364 static void task_fork_fair(struct task_struct *p)
7365 {
7366         struct cfs_rq *cfs_rq;
7367         struct sched_entity *se = &p->se, *curr;
7368         int this_cpu = smp_processor_id();
7369         struct rq *rq = this_rq();
7370         unsigned long flags;
7371 
7372         raw_spin_lock_irqsave(&rq->lock, flags);
7373 
7374         update_rq_clock(rq);
7375 
7376         cfs_rq = task_cfs_rq(current);
7377         curr = cfs_rq->curr;
7378 
7379         /*
7380          * Not only the cpu but also the task_group of the parent might have
7381          * been changed after parent->se.parent,cfs_rq were copied to
7382          * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7383          * of child point to valid ones.
7384          */
7385         rcu_read_lock();
7386         __set_task_cpu(p, this_cpu);
7387         rcu_read_unlock();
7388 
7389         update_curr(cfs_rq);
7390 
7391         if (curr)
7392                 se->vruntime = curr->vruntime;
7393         place_entity(cfs_rq, se, 1);
7394 
7395         if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7396                 /*
7397                  * Upon rescheduling, sched_class::put_prev_task() will place
7398                  * 'current' within the tree based on its new key value.
7399                  */
7400                 swap(curr->vruntime, se->vruntime);
7401                 resched_task(rq->curr);
7402         }
7403 
7404         se->vruntime -= cfs_rq->min_vruntime;
7405 
7406         raw_spin_unlock_irqrestore(&rq->lock, flags);
7407 }
7408 
7409 /*
7410  * Priority of the task has changed. Check to see if we preempt
7411  * the current task.
7412  */
7413 static void
7414 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7415 {
7416         if (!p->se.on_rq)
7417                 return;
7418 
7419         /*
7420          * Reschedule if we are currently running on this runqueue and
7421          * our priority decreased, or if we are not currently running on
7422          * this runqueue and our priority is higher than the current's
7423          */
7424         if (rq->curr == p) {
7425                 if (p->prio > oldprio)
7426                         resched_task(rq->curr);
7427         } else
7428                 check_preempt_curr(rq, p, 0);
7429 }
7430 
7431 static void switched_from_fair(struct rq *rq, struct task_struct *p)
7432 {
7433         struct sched_entity *se = &p->se;
7434         struct cfs_rq *cfs_rq = cfs_rq_of(se);
7435 
7436         /*
7437          * Ensure the task's vruntime is normalized, so that when it's
7438          * switched back to the fair class the enqueue_entity(.flags=0) will
7439          * do the right thing.
7440          *
7441          * If it's on_rq, then the dequeue_entity(.flags=0) will already
7442          * have normalized the vruntime, if it's !on_rq, then only when
7443          * the task is sleeping will it still have non-normalized vruntime.
7444          */
7445         if (!p->on_rq && p->state != TASK_RUNNING) {
7446                 /*
7447                  * Fix up our vruntime so that the current sleep doesn't
7448                  * cause 'unlimited' sleep bonus.
7449                  */
7450                 place_entity(cfs_rq, se, 0);
7451                 se->vruntime -= cfs_rq->min_vruntime;
7452         }
7453 
7454 #ifdef CONFIG_SMP
7455         /*
7456         * Remove our load from contribution when we leave sched_fair
7457         * and ensure we don't carry in an old decay_count if we
7458         * switch back.
7459         */
7460         if (se->avg.decay_count) {
7461                 __synchronize_entity_decay(se);
7462                 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
7463         }
7464 #endif
7465 }
7466 
7467 /*
7468  * We switched to the sched_fair class.
7469  */
7470 static void switched_to_fair(struct rq *rq, struct task_struct *p)
7471 {
7472         struct sched_entity *se = &p->se;
7473 #ifdef CONFIG_FAIR_GROUP_SCHED
7474         /*
7475          * Since the real-depth could have been changed (only FAIR
7476          * class maintain depth value), reset depth properly.
7477          */
7478         se->depth = se->parent ? se->parent->depth + 1 : 0;
7479 #endif
7480         if (!se->on_rq)
7481                 return;
7482 
7483         /*
7484          * We were most likely switched from sched_rt, so
7485          * kick off the schedule if running, otherwise just see
7486          * if we can still preempt the current task.
7487          */
7488         if (rq->curr == p)
7489                 resched_task(rq->curr);
7490         else
7491                 check_preempt_curr(rq, p, 0);
7492 }
7493 
7494 /* Account for a task changing its policy or group.
7495  *
7496  * This routine is mostly called to set cfs_rq->curr field when a task
7497  * migrates between groups/classes.
7498  */
7499 static void set_curr_task_fair(struct rq *rq)
7500 {
7501         struct sched_entity *se = &rq->curr->se;
7502 
7503         for_each_sched_entity(se) {
7504                 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7505 
7506                 set_next_entity(cfs_rq, se);
7507                 /* ensure bandwidth has been allocated on our new cfs_rq */
7508                 account_cfs_rq_runtime(cfs_rq, 0);
7509         }
7510 }
7511 
7512 void init_cfs_rq(struct cfs_rq *cfs_rq)
7513 {
7514         cfs_rq->tasks_timeline = RB_ROOT;
7515         cfs_rq->min_vruntime = (u64)(-(1LL << 20));
7516 #ifndef CONFIG_64BIT
7517         cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
7518 #endif
7519 #ifdef CONFIG_SMP
7520         atomic64_set(&cfs_rq->decay_counter, 1);
7521         atomic_long_set(&cfs_rq->removed_load, 0);
7522 #endif
7523 }
7524 
7525 #ifdef CONFIG_FAIR_GROUP_SCHED
7526 static void task_move_group_fair(struct task_struct *p, int on_rq)
7527 {
7528         struct sched_entity *se = &p->se;
7529         struct cfs_rq *cfs_rq;
7530 
7531         /*
7532          * If the task was not on the rq at the time of this cgroup movement
7533          * it must have been asleep, sleeping tasks keep their ->vruntime
7534          * absolute on their old rq until wakeup (needed for the fair sleeper
7535          * bonus in place_entity()).
7536          *
7537          * If it was on the rq, we've just 'preempted' it, which does convert
7538          * ->vruntime to a relative base.
7539          *
7540          * Make sure both cases convert their relative position when migrating
7541          * to another cgroup's rq. This does somewhat interfere with the
7542          * fair sleeper stuff for the first placement, but who cares.
7543          */
7544         /*
7545          * When !on_rq, vruntime of the task has usually NOT been normalized.
7546          * But there are some cases where it has already been normalized:
7547          *
7548          * - Moving a forked child which is waiting for being woken up by
7549          *   wake_up_new_task().
7550          * - Moving a task which has been woken up by try_to_wake_up() and
7551          *   waiting for actually being woken up by sched_ttwu_pending().
7552          *
7553          * To prevent boost or penalty in the new cfs_rq caused by delta
7554          * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
7555          */
7556         if (!on_rq && (!se->sum_exec_runtime || p->state == TASK_WAKING))
7557                 on_rq = 1;
7558 
7559         if (!on_rq)
7560                 se->vruntime -= cfs_rq_of(se)->min_vruntime;
7561         set_task_rq(p, task_cpu(p));
7562         se->depth = se->parent ? se->parent->depth + 1 : 0;
7563         if (!on_rq) {
7564                 cfs_rq = cfs_rq_of(se);
7565                 se->vruntime += cfs_rq->min_vruntime;
7566 #ifdef CONFIG_SMP
7567                 /*
7568                  * migrate_task_rq_fair() will have removed our previous
7569                  * contribution, but we must synchronize for ongoing future
7570                  * decay.
7571                  */
7572                 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
7573                 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
7574 #endif
7575         }
7576 }
7577 
7578 void free_fair_sched_group(struct task_group *tg)
7579 {
7580         int i;
7581 
7582         destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
7583 
7584         for_each_possible_cpu(i) {
7585                 if (tg->cfs_rq)
7586                         kfree(tg->cfs_rq[i]);
7587                 if (tg->se)
7588                         kfree(tg->se[i]);
7589         }
7590 
7591         kfree(tg->cfs_rq);
7592         kfree(tg->se);
7593 }
7594 
7595 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
7596 {
7597         struct cfs_rq *cfs_rq;
7598         struct sched_entity *se;
7599         int i;
7600 
7601         tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
7602         if (!tg->cfs_rq)
7603                 goto err;
7604         tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
7605         if (!tg->se)
7606                 goto err;
7607 
7608         tg->shares = NICE_0_LOAD;
7609 
7610         init_cfs_bandwidth(tg_cfs_bandwidth(tg));
7611 
7612         for_each_possible_cpu(i) {
7613                 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
7614                                       GFP_KERNEL, cpu_to_node(i));
7615                 if (!cfs_rq)
7616                         goto err;
7617 
7618                 se = kzalloc_node(sizeof(struct sched_entity),
7619                                   GFP_KERNEL, cpu_to_node(i));
7620                 if (!se)
7621                         goto err_free_rq;
7622 
7623                 init_cfs_rq(cfs_rq);
7624                 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
7625         }
7626 
7627         return 1;
7628 
7629 err_free_rq:
7630         kfree(cfs_rq);
7631 err:
7632         return 0;
7633 }
7634 
7635 void unregister_fair_sched_group(struct task_group *tg, int cpu)
7636 {
7637         struct rq *rq = cpu_rq(cpu);
7638         unsigned long flags;
7639 
7640         /*
7641         * Only empty task groups can be destroyed; so we can speculatively
7642         * check on_list without danger of it being re-added.
7643         */
7644         if (!tg->cfs_rq[cpu]->on_list)
7645                 return;
7646 
7647         raw_spin_lock_irqsave(&rq->lock, flags);
7648         list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
7649         raw_spin_unlock_irqrestore(&rq->lock, flags);
7650 }
7651 
7652 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
7653                         struct sched_entity *se, int cpu,
7654                         struct sched_entity *parent)
7655 {
7656         struct rq *rq = cpu_rq(cpu);
7657 
7658         cfs_rq->tg = tg;
7659         cfs_rq->rq = rq;
7660         init_cfs_rq_runtime(cfs_rq);
7661 
7662         tg->cfs_rq[cpu] = cfs_rq;
7663         tg->se[cpu] = se;
7664 
7665         /* se could be NULL for root_task_group */
7666         if (!se)
7667                 return;
7668 
7669         if (!parent) {
7670                 se->cfs_rq = &rq->cfs;
7671                 se->depth = 0;
7672         } else {
7673                 se->cfs_rq = parent->my_q;
7674                 se->depth = parent->depth + 1;
7675         }
7676 
7677         se->my_q = cfs_rq;
7678         /* guarantee group entities always have weight */
7679         update_load_set(&se->load, NICE_0_LOAD);
7680         se->parent = parent;
7681 }
7682 
7683 static DEFINE_MUTEX(shares_mutex);
7684 
7685 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
7686 {
7687         int i;
7688         unsigned long flags;
7689 
7690         /*
7691          * We can't change the weight of the root cgroup.
7692          */
7693         if (!tg->se[0])
7694                 return -EINVAL;
7695 
7696         shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
7697 
7698         mutex_lock(&shares_mutex);
7699         if (tg->shares == shares)
7700                 goto done;
7701 
7702         tg->shares = shares;
7703         for_each_possible_cpu(i) {
7704                 struct rq *rq = cpu_rq(i);
7705                 struct sched_entity *se;
7706 
7707                 se = tg->se[i];
7708                 /* Propagate contribution to hierarchy */
7709                 raw_spin_lock_irqsave(&rq->lock, flags);
7710 
7711                 /* Possible calls to update_curr() need rq clock */
7712                 update_rq_clock(rq);
7713                 for_each_sched_entity(se)
7714                         update_cfs_shares(group_cfs_rq(se));
7715                 raw_spin_unlock_irqrestore(&rq->lock, flags);
7716         }
7717 
7718 done:
7719         mutex_unlock(&shares_mutex);
7720         return 0;
7721 }
7722 #else /* CONFIG_FAIR_GROUP_SCHED */
7723 
7724 void free_fair_sched_group(struct task_group *tg) { }
7725 
7726 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
7727 {
7728         return 1;
7729 }
7730 
7731 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
7732 
7733 #endif /* CONFIG_FAIR_GROUP_SCHED */
7734 
7735 
7736 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
7737 {
7738         struct sched_entity *se = &task->se;
7739         unsigned int rr_interval = 0;
7740 
7741         /*
7742          * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
7743          * idle runqueue:
7744          */
7745         if (rq->cfs.load.weight)
7746                 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
7747 
7748         return rr_interval;
7749 }
7750 
7751 /*
7752  * All the scheduling class methods:
7753  */
7754 const struct sched_class fair_sched_class = {
7755         .next                   = &idle_sched_class,
7756         .enqueue_task           = enqueue_task_fair,
7757         .dequeue_task           = dequeue_task_fair,
7758         .yield_task             = yield_task_fair,
7759         .yield_to_task          = yield_to_task_fair,
7760 
7761         .check_preempt_curr     = check_preempt_wakeup,
7762 
7763         .pick_next_task         = pick_next_task_fair,
7764         .put_prev_task          = put_prev_task_fair,
7765 
7766 #ifdef CONFIG_SMP
7767         .select_task_rq         = select_task_rq_fair,
7768         .migrate_task_rq        = migrate_task_rq_fair,
7769 
7770         .rq_online              = rq_online_fair,
7771         .rq_offline             = rq_offline_fair,
7772 
7773         .task_waking            = task_waking_fair,
7774 #endif
7775 
7776         .set_curr_task          = set_curr_task_fair,
7777         .task_tick              = task_tick_fair,
7778         .task_fork              = task_fork_fair,
7779 
7780         .prio_changed           = prio_changed_fair,
7781         .switched_from          = switched_from_fair,
7782         .switched_to            = switched_to_fair,
7783 
7784         .get_rr_interval        = get_rr_interval_fair,
7785 
7786 #ifdef CONFIG_FAIR_GROUP_SCHED
7787         .task_move_group        = task_move_group_fair,
7788 #endif
7789 };
7790 
7791 #ifdef CONFIG_SCHED_DEBUG
7792 void print_cfs_stats(struct seq_file *m, int cpu)
7793 {
7794         struct cfs_rq *cfs_rq;
7795 
7796         rcu_read_lock();
7797         for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
7798                 print_cfs_rq(m, cpu, cfs_rq);
7799         rcu_read_unlock();
7800 }
7801 #endif
7802 
7803 __init void init_sched_fair_class(void)
7804 {
7805 #ifdef CONFIG_SMP
7806         open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
7807 
7808 #ifdef CONFIG_NO_HZ_COMMON
7809         nohz.next_balance = jiffies;
7810         zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
7811         cpu_notifier(sched_ilb_notifier, 0);
7812 #endif
7813 #endif /* SMP */
7814 
7815 }
7816 

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