2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
23 #include <linux/sched.h>
24 #include <linux/latencytop.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency = 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity = 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency = 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
94 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
117 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
123 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
129 static inline void update_load_set(struct load_weight *lw, unsigned long w)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static unsigned int get_update_sysctl_factor(void)
146 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling) {
150 case SCHED_TUNABLESCALING_NONE:
153 case SCHED_TUNABLESCALING_LINEAR:
156 case SCHED_TUNABLESCALING_LOG:
158 factor = 1 + ilog2(cpus);
165 static void update_sysctl(void)
167 unsigned int factor = get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity);
172 SET_SYSCTL(sched_latency);
173 SET_SYSCTL(sched_wakeup_granularity);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight *lw)
189 if (likely(lw->inv_weight))
192 w = scale_load_down(lw->weight);
194 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
196 else if (unlikely(!w))
197 lw->inv_weight = WMULT_CONST;
199 lw->inv_weight = WMULT_CONST / w;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
216 u64 fact = scale_load_down(weight);
217 int shift = WMULT_SHIFT;
219 __update_inv_weight(lw);
221 if (unlikely(fact >> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact = (u64)(u32)fact * lw->inv_weight;
236 return mul_u64_u32_shr(delta_exec, fact, shift);
240 const struct sched_class fair_sched_class;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct *task_of(struct sched_entity *se)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se));
262 return container_of(se, struct task_struct, se);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
288 if (!cfs_rq->on_list) {
290 * Ensure we either appear before our parent (if already
291 * enqueued) or force our parent to appear after us when it is
292 * enqueued. The fact that we always enqueue bottom-up
293 * reduces this to two cases.
295 if (cfs_rq->tg->parent &&
296 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
297 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
298 &rq_of(cfs_rq)->leaf_cfs_rq_list);
300 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
301 &rq_of(cfs_rq)->leaf_cfs_rq_list);
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
310 if (cfs_rq->on_list) {
311 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq *
322 is_same_group(struct sched_entity *se, struct sched_entity *pse)
324 if (se->cfs_rq == pse->cfs_rq)
330 static inline struct sched_entity *parent_entity(struct sched_entity *se)
336 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
338 int se_depth, pse_depth;
341 * preemption test can be made between sibling entities who are in the
342 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343 * both tasks until we find their ancestors who are siblings of common
347 /* First walk up until both entities are at same depth */
348 se_depth = (*se)->depth;
349 pse_depth = (*pse)->depth;
351 while (se_depth > pse_depth) {
353 *se = parent_entity(*se);
356 while (pse_depth > se_depth) {
358 *pse = parent_entity(*pse);
361 while (!is_same_group(*se, *pse)) {
362 *se = parent_entity(*se);
363 *pse = parent_entity(*pse);
367 #else /* !CONFIG_FAIR_GROUP_SCHED */
369 static inline struct task_struct *task_of(struct sched_entity *se)
371 return container_of(se, struct task_struct, se);
374 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
376 return container_of(cfs_rq, struct rq, cfs);
379 #define entity_is_task(se) 1
381 #define for_each_sched_entity(se) \
382 for (; se; se = NULL)
384 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
386 return &task_rq(p)->cfs;
389 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
391 struct task_struct *p = task_of(se);
392 struct rq *rq = task_rq(p);
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
414 static inline struct sched_entity *parent_entity(struct sched_entity *se)
420 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
424 #endif /* CONFIG_FAIR_GROUP_SCHED */
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
429 /**************************************************************
430 * Scheduling class tree data structure manipulation methods:
433 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
435 s64 delta = (s64)(vruntime - max_vruntime);
437 max_vruntime = vruntime;
442 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
444 s64 delta = (s64)(vruntime - min_vruntime);
446 min_vruntime = vruntime;
451 static inline int entity_before(struct sched_entity *a,
452 struct sched_entity *b)
454 return (s64)(a->vruntime - b->vruntime) < 0;
457 static void update_min_vruntime(struct cfs_rq *cfs_rq)
459 u64 vruntime = cfs_rq->min_vruntime;
462 vruntime = cfs_rq->curr->vruntime;
464 if (cfs_rq->rb_leftmost) {
465 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
470 vruntime = se->vruntime;
472 vruntime = min_vruntime(vruntime, se->vruntime);
475 /* ensure we never gain time by being placed backwards. */
476 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
479 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
484 * Enqueue an entity into the rb-tree:
486 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
488 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
489 struct rb_node *parent = NULL;
490 struct sched_entity *entry;
494 * Find the right place in the rbtree:
498 entry = rb_entry(parent, struct sched_entity, run_node);
500 * We dont care about collisions. Nodes with
501 * the same key stay together.
503 if (entity_before(se, entry)) {
504 link = &parent->rb_left;
506 link = &parent->rb_right;
512 * Maintain a cache of leftmost tree entries (it is frequently
516 cfs_rq->rb_leftmost = &se->run_node;
518 rb_link_node(&se->run_node, parent, link);
519 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
522 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
524 if (cfs_rq->rb_leftmost == &se->run_node) {
525 struct rb_node *next_node;
527 next_node = rb_next(&se->run_node);
528 cfs_rq->rb_leftmost = next_node;
531 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
534 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
536 struct rb_node *left = cfs_rq->rb_leftmost;
541 return rb_entry(left, struct sched_entity, run_node);
544 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
546 struct rb_node *next = rb_next(&se->run_node);
551 return rb_entry(next, struct sched_entity, run_node);
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
557 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
562 return rb_entry(last, struct sched_entity, run_node);
565 /**************************************************************
566 * Scheduling class statistics methods:
569 int sched_proc_update_handler(struct ctl_table *table, int write,
570 void __user *buffer, size_t *lenp,
573 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
574 unsigned int factor = get_update_sysctl_factor();
579 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
580 sysctl_sched_min_granularity);
582 #define WRT_SYSCTL(name) \
583 (normalized_sysctl_##name = sysctl_##name / (factor))
584 WRT_SYSCTL(sched_min_granularity);
585 WRT_SYSCTL(sched_latency);
586 WRT_SYSCTL(sched_wakeup_granularity);
596 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
598 if (unlikely(se->load.weight != NICE_0_LOAD))
599 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
605 * The idea is to set a period in which each task runs once.
607 * When there are too many tasks (sched_nr_latency) we have to stretch
608 * this period because otherwise the slices get too small.
610 * p = (nr <= nl) ? l : l*nr/nl
612 static u64 __sched_period(unsigned long nr_running)
614 if (unlikely(nr_running > sched_nr_latency))
615 return nr_running * sysctl_sched_min_granularity;
617 return sysctl_sched_latency;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
628 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
630 for_each_sched_entity(se) {
631 struct load_weight *load;
632 struct load_weight lw;
634 cfs_rq = cfs_rq_of(se);
635 load = &cfs_rq->load;
637 if (unlikely(!se->on_rq)) {
640 update_load_add(&lw, se->load.weight);
643 slice = __calc_delta(slice, se->load.weight, load);
649 * We calculate the vruntime slice of a to-be-inserted task.
653 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
655 return calc_delta_fair(sched_slice(cfs_rq, se), se);
659 static int select_idle_sibling(struct task_struct *p, int cpu);
660 static unsigned long task_h_load(struct task_struct *p);
663 * We choose a half-life close to 1 scheduling period.
664 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
665 * dependent on this value.
667 #define LOAD_AVG_PERIOD 32
668 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
671 /* Give new sched_entity start runnable values to heavy its load in infant time */
672 void init_entity_runnable_average(struct sched_entity *se)
674 struct sched_avg *sa = &se->avg;
676 sa->last_update_time = 0;
678 * sched_avg's period_contrib should be strictly less then 1024, so
679 * we give it 1023 to make sure it is almost a period (1024us), and
680 * will definitely be update (after enqueue).
682 sa->period_contrib = 1023;
683 sa->load_avg = scale_load_down(se->load.weight);
684 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
686 * At this point, util_avg won't be used in select_task_rq_fair anyway
690 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
693 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
694 static int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq);
695 static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force);
696 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se);
699 * With new tasks being created, their initial util_avgs are extrapolated
700 * based on the cfs_rq's current util_avg:
702 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
704 * However, in many cases, the above util_avg does not give a desired
705 * value. Moreover, the sum of the util_avgs may be divergent, such
706 * as when the series is a harmonic series.
708 * To solve this problem, we also cap the util_avg of successive tasks to
709 * only 1/2 of the left utilization budget:
711 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
713 * where n denotes the nth task.
715 * For example, a simplest series from the beginning would be like:
717 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
718 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
720 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
721 * if util_avg > util_avg_cap.
723 void post_init_entity_util_avg(struct sched_entity *se)
725 struct cfs_rq *cfs_rq = cfs_rq_of(se);
726 struct sched_avg *sa = &se->avg;
727 long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
728 u64 now = cfs_rq_clock_task(cfs_rq);
732 if (cfs_rq->avg.util_avg != 0) {
733 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight;
734 sa->util_avg /= (cfs_rq->avg.load_avg + 1);
736 if (sa->util_avg > cap)
741 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
744 if (entity_is_task(se)) {
745 struct task_struct *p = task_of(se);
746 if (p->sched_class != &fair_sched_class) {
748 * For !fair tasks do:
750 update_cfs_rq_load_avg(now, cfs_rq, false);
751 attach_entity_load_avg(cfs_rq, se);
752 switched_from_fair(rq, p);
754 * such that the next switched_to_fair() has the
757 se->avg.last_update_time = now;
762 tg_update = update_cfs_rq_load_avg(now, cfs_rq, false);
763 attach_entity_load_avg(cfs_rq, se);
765 update_tg_load_avg(cfs_rq, false);
768 #else /* !CONFIG_SMP */
769 void init_entity_runnable_average(struct sched_entity *se)
772 void post_init_entity_util_avg(struct sched_entity *se)
775 static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
778 #endif /* CONFIG_SMP */
781 * Update the current task's runtime statistics.
783 static void update_curr(struct cfs_rq *cfs_rq)
785 struct sched_entity *curr = cfs_rq->curr;
786 u64 now = rq_clock_task(rq_of(cfs_rq));
792 delta_exec = now - curr->exec_start;
793 if (unlikely((s64)delta_exec <= 0))
796 curr->exec_start = now;
798 schedstat_set(curr->statistics.exec_max,
799 max(delta_exec, curr->statistics.exec_max));
801 curr->sum_exec_runtime += delta_exec;
802 schedstat_add(cfs_rq, exec_clock, delta_exec);
804 curr->vruntime += calc_delta_fair(delta_exec, curr);
805 update_min_vruntime(cfs_rq);
807 if (entity_is_task(curr)) {
808 struct task_struct *curtask = task_of(curr);
810 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
811 cpuacct_charge(curtask, delta_exec);
812 account_group_exec_runtime(curtask, delta_exec);
815 account_cfs_rq_runtime(cfs_rq, delta_exec);
818 static void update_curr_fair(struct rq *rq)
820 update_curr(cfs_rq_of(&rq->curr->se));
823 #ifdef CONFIG_SCHEDSTATS
825 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
827 u64 wait_start = rq_clock(rq_of(cfs_rq));
829 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
830 likely(wait_start > se->statistics.wait_start))
831 wait_start -= se->statistics.wait_start;
833 se->statistics.wait_start = wait_start;
837 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
839 struct task_struct *p;
842 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
844 if (entity_is_task(se)) {
846 if (task_on_rq_migrating(p)) {
848 * Preserve migrating task's wait time so wait_start
849 * time stamp can be adjusted to accumulate wait time
850 * prior to migration.
852 se->statistics.wait_start = delta;
855 trace_sched_stat_wait(p, delta);
858 se->statistics.wait_max = max(se->statistics.wait_max, delta);
859 se->statistics.wait_count++;
860 se->statistics.wait_sum += delta;
861 se->statistics.wait_start = 0;
865 * Task is being enqueued - update stats:
868 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
871 * Are we enqueueing a waiting task? (for current tasks
872 * a dequeue/enqueue event is a NOP)
874 if (se != cfs_rq->curr)
875 update_stats_wait_start(cfs_rq, se);
879 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
882 * Mark the end of the wait period if dequeueing a
885 if (se != cfs_rq->curr)
886 update_stats_wait_end(cfs_rq, se);
888 if (flags & DEQUEUE_SLEEP) {
889 if (entity_is_task(se)) {
890 struct task_struct *tsk = task_of(se);
892 if (tsk->state & TASK_INTERRUPTIBLE)
893 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
894 if (tsk->state & TASK_UNINTERRUPTIBLE)
895 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
902 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
907 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
912 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
917 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
923 * We are picking a new current task - update its stats:
926 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
929 * We are starting a new run period:
931 se->exec_start = rq_clock_task(rq_of(cfs_rq));
934 /**************************************************
935 * Scheduling class queueing methods:
938 #ifdef CONFIG_NUMA_BALANCING
940 * Approximate time to scan a full NUMA task in ms. The task scan period is
941 * calculated based on the tasks virtual memory size and
942 * numa_balancing_scan_size.
944 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
945 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
947 /* Portion of address space to scan in MB */
948 unsigned int sysctl_numa_balancing_scan_size = 256;
950 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
951 unsigned int sysctl_numa_balancing_scan_delay = 1000;
953 static unsigned int task_nr_scan_windows(struct task_struct *p)
955 unsigned long rss = 0;
956 unsigned long nr_scan_pages;
959 * Calculations based on RSS as non-present and empty pages are skipped
960 * by the PTE scanner and NUMA hinting faults should be trapped based
963 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
964 rss = get_mm_rss(p->mm);
968 rss = round_up(rss, nr_scan_pages);
969 return rss / nr_scan_pages;
972 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
973 #define MAX_SCAN_WINDOW 2560
975 static unsigned int task_scan_min(struct task_struct *p)
977 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
978 unsigned int scan, floor;
979 unsigned int windows = 1;
981 if (scan_size < MAX_SCAN_WINDOW)
982 windows = MAX_SCAN_WINDOW / scan_size;
983 floor = 1000 / windows;
985 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
986 return max_t(unsigned int, floor, scan);
989 static unsigned int task_scan_max(struct task_struct *p)
991 unsigned int smin = task_scan_min(p);
994 /* Watch for min being lower than max due to floor calculations */
995 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
996 return max(smin, smax);
999 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
1001 rq->nr_numa_running += (p->numa_preferred_nid != -1);
1002 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
1005 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
1007 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
1008 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
1014 spinlock_t lock; /* nr_tasks, tasks */
1019 struct rcu_head rcu;
1020 unsigned long total_faults;
1021 unsigned long max_faults_cpu;
1023 * Faults_cpu is used to decide whether memory should move
1024 * towards the CPU. As a consequence, these stats are weighted
1025 * more by CPU use than by memory faults.
1027 unsigned long *faults_cpu;
1028 unsigned long faults[0];
1031 /* Shared or private faults. */
1032 #define NR_NUMA_HINT_FAULT_TYPES 2
1034 /* Memory and CPU locality */
1035 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1037 /* Averaged statistics, and temporary buffers. */
1038 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1040 pid_t task_numa_group_id(struct task_struct *p)
1042 return p->numa_group ? p->numa_group->gid : 0;
1046 * The averaged statistics, shared & private, memory & cpu,
1047 * occupy the first half of the array. The second half of the
1048 * array is for current counters, which are averaged into the
1049 * first set by task_numa_placement.
1051 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1053 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1056 static inline unsigned long task_faults(struct task_struct *p, int nid)
1058 if (!p->numa_faults)
1061 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1062 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1065 static inline unsigned long group_faults(struct task_struct *p, int nid)
1070 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
1071 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1074 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
1076 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
1077 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1081 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1082 * considered part of a numa group's pseudo-interleaving set. Migrations
1083 * between these nodes are slowed down, to allow things to settle down.
1085 #define ACTIVE_NODE_FRACTION 3
1087 static bool numa_is_active_node(int nid, struct numa_group *ng)
1089 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
1092 /* Handle placement on systems where not all nodes are directly connected. */
1093 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
1094 int maxdist, bool task)
1096 unsigned long score = 0;
1100 * All nodes are directly connected, and the same distance
1101 * from each other. No need for fancy placement algorithms.
1103 if (sched_numa_topology_type == NUMA_DIRECT)
1107 * This code is called for each node, introducing N^2 complexity,
1108 * which should be ok given the number of nodes rarely exceeds 8.
1110 for_each_online_node(node) {
1111 unsigned long faults;
1112 int dist = node_distance(nid, node);
1115 * The furthest away nodes in the system are not interesting
1116 * for placement; nid was already counted.
1118 if (dist == sched_max_numa_distance || node == nid)
1122 * On systems with a backplane NUMA topology, compare groups
1123 * of nodes, and move tasks towards the group with the most
1124 * memory accesses. When comparing two nodes at distance
1125 * "hoplimit", only nodes closer by than "hoplimit" are part
1126 * of each group. Skip other nodes.
1128 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1132 /* Add up the faults from nearby nodes. */
1134 faults = task_faults(p, node);
1136 faults = group_faults(p, node);
1139 * On systems with a glueless mesh NUMA topology, there are
1140 * no fixed "groups of nodes". Instead, nodes that are not
1141 * directly connected bounce traffic through intermediate
1142 * nodes; a numa_group can occupy any set of nodes.
1143 * The further away a node is, the less the faults count.
1144 * This seems to result in good task placement.
1146 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1147 faults *= (sched_max_numa_distance - dist);
1148 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1158 * These return the fraction of accesses done by a particular task, or
1159 * task group, on a particular numa node. The group weight is given a
1160 * larger multiplier, in order to group tasks together that are almost
1161 * evenly spread out between numa nodes.
1163 static inline unsigned long task_weight(struct task_struct *p, int nid,
1166 unsigned long faults, total_faults;
1168 if (!p->numa_faults)
1171 total_faults = p->total_numa_faults;
1176 faults = task_faults(p, nid);
1177 faults += score_nearby_nodes(p, nid, dist, true);
1179 return 1000 * faults / total_faults;
1182 static inline unsigned long group_weight(struct task_struct *p, int nid,
1185 unsigned long faults, total_faults;
1190 total_faults = p->numa_group->total_faults;
1195 faults = group_faults(p, nid);
1196 faults += score_nearby_nodes(p, nid, dist, false);
1198 return 1000 * faults / total_faults;
1201 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1202 int src_nid, int dst_cpu)
1204 struct numa_group *ng = p->numa_group;
1205 int dst_nid = cpu_to_node(dst_cpu);
1206 int last_cpupid, this_cpupid;
1208 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1211 * Multi-stage node selection is used in conjunction with a periodic
1212 * migration fault to build a temporal task<->page relation. By using
1213 * a two-stage filter we remove short/unlikely relations.
1215 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1216 * a task's usage of a particular page (n_p) per total usage of this
1217 * page (n_t) (in a given time-span) to a probability.
1219 * Our periodic faults will sample this probability and getting the
1220 * same result twice in a row, given these samples are fully
1221 * independent, is then given by P(n)^2, provided our sample period
1222 * is sufficiently short compared to the usage pattern.
1224 * This quadric squishes small probabilities, making it less likely we
1225 * act on an unlikely task<->page relation.
1227 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1228 if (!cpupid_pid_unset(last_cpupid) &&
1229 cpupid_to_nid(last_cpupid) != dst_nid)
1232 /* Always allow migrate on private faults */
1233 if (cpupid_match_pid(p, last_cpupid))
1236 /* A shared fault, but p->numa_group has not been set up yet. */
1241 * Destination node is much more heavily used than the source
1242 * node? Allow migration.
1244 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
1245 ACTIVE_NODE_FRACTION)
1249 * Distribute memory according to CPU & memory use on each node,
1250 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1252 * faults_cpu(dst) 3 faults_cpu(src)
1253 * --------------- * - > ---------------
1254 * faults_mem(dst) 4 faults_mem(src)
1256 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
1257 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1260 static unsigned long weighted_cpuload(const int cpu);
1261 static unsigned long source_load(int cpu, int type);
1262 static unsigned long target_load(int cpu, int type);
1263 static unsigned long capacity_of(int cpu);
1264 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1266 /* Cached statistics for all CPUs within a node */
1268 unsigned long nr_running;
1271 /* Total compute capacity of CPUs on a node */
1272 unsigned long compute_capacity;
1274 /* Approximate capacity in terms of runnable tasks on a node */
1275 unsigned long task_capacity;
1276 int has_free_capacity;
1280 * XXX borrowed from update_sg_lb_stats
1282 static void update_numa_stats(struct numa_stats *ns, int nid)
1284 int smt, cpu, cpus = 0;
1285 unsigned long capacity;
1287 memset(ns, 0, sizeof(*ns));
1288 for_each_cpu(cpu, cpumask_of_node(nid)) {
1289 struct rq *rq = cpu_rq(cpu);
1291 ns->nr_running += rq->nr_running;
1292 ns->load += weighted_cpuload(cpu);
1293 ns->compute_capacity += capacity_of(cpu);
1299 * If we raced with hotplug and there are no CPUs left in our mask
1300 * the @ns structure is NULL'ed and task_numa_compare() will
1301 * not find this node attractive.
1303 * We'll either bail at !has_free_capacity, or we'll detect a huge
1304 * imbalance and bail there.
1309 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1310 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1311 capacity = cpus / smt; /* cores */
1313 ns->task_capacity = min_t(unsigned, capacity,
1314 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1315 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1318 struct task_numa_env {
1319 struct task_struct *p;
1321 int src_cpu, src_nid;
1322 int dst_cpu, dst_nid;
1324 struct numa_stats src_stats, dst_stats;
1329 struct task_struct *best_task;
1334 static void task_numa_assign(struct task_numa_env *env,
1335 struct task_struct *p, long imp)
1338 put_task_struct(env->best_task);
1343 env->best_imp = imp;
1344 env->best_cpu = env->dst_cpu;
1347 static bool load_too_imbalanced(long src_load, long dst_load,
1348 struct task_numa_env *env)
1351 long orig_src_load, orig_dst_load;
1352 long src_capacity, dst_capacity;
1355 * The load is corrected for the CPU capacity available on each node.
1358 * ------------ vs ---------
1359 * src_capacity dst_capacity
1361 src_capacity = env->src_stats.compute_capacity;
1362 dst_capacity = env->dst_stats.compute_capacity;
1364 /* We care about the slope of the imbalance, not the direction. */
1365 if (dst_load < src_load)
1366 swap(dst_load, src_load);
1368 /* Is the difference below the threshold? */
1369 imb = dst_load * src_capacity * 100 -
1370 src_load * dst_capacity * env->imbalance_pct;
1375 * The imbalance is above the allowed threshold.
1376 * Compare it with the old imbalance.
1378 orig_src_load = env->src_stats.load;
1379 orig_dst_load = env->dst_stats.load;
1381 if (orig_dst_load < orig_src_load)
1382 swap(orig_dst_load, orig_src_load);
1384 old_imb = orig_dst_load * src_capacity * 100 -
1385 orig_src_load * dst_capacity * env->imbalance_pct;
1387 /* Would this change make things worse? */
1388 return (imb > old_imb);
1392 * This checks if the overall compute and NUMA accesses of the system would
1393 * be improved if the source tasks was migrated to the target dst_cpu taking
1394 * into account that it might be best if task running on the dst_cpu should
1395 * be exchanged with the source task
1397 static void task_numa_compare(struct task_numa_env *env,
1398 long taskimp, long groupimp)
1400 struct rq *src_rq = cpu_rq(env->src_cpu);
1401 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1402 struct task_struct *cur;
1403 long src_load, dst_load;
1405 long imp = env->p->numa_group ? groupimp : taskimp;
1407 int dist = env->dist;
1410 cur = task_rcu_dereference(&dst_rq->curr);
1411 if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1415 * Because we have preemption enabled we can get migrated around and
1416 * end try selecting ourselves (current == env->p) as a swap candidate.
1422 * "imp" is the fault differential for the source task between the
1423 * source and destination node. Calculate the total differential for
1424 * the source task and potential destination task. The more negative
1425 * the value is, the more rmeote accesses that would be expected to
1426 * be incurred if the tasks were swapped.
1429 /* Skip this swap candidate if cannot move to the source cpu */
1430 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1434 * If dst and source tasks are in the same NUMA group, or not
1435 * in any group then look only at task weights.
1437 if (cur->numa_group == env->p->numa_group) {
1438 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1439 task_weight(cur, env->dst_nid, dist);
1441 * Add some hysteresis to prevent swapping the
1442 * tasks within a group over tiny differences.
1444 if (cur->numa_group)
1448 * Compare the group weights. If a task is all by
1449 * itself (not part of a group), use the task weight
1452 if (cur->numa_group)
1453 imp += group_weight(cur, env->src_nid, dist) -
1454 group_weight(cur, env->dst_nid, dist);
1456 imp += task_weight(cur, env->src_nid, dist) -
1457 task_weight(cur, env->dst_nid, dist);
1461 if (imp <= env->best_imp && moveimp <= env->best_imp)
1465 /* Is there capacity at our destination? */
1466 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1467 !env->dst_stats.has_free_capacity)
1473 /* Balance doesn't matter much if we're running a task per cpu */
1474 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1475 dst_rq->nr_running == 1)
1479 * In the overloaded case, try and keep the load balanced.
1482 load = task_h_load(env->p);
1483 dst_load = env->dst_stats.load + load;
1484 src_load = env->src_stats.load - load;
1486 if (moveimp > imp && moveimp > env->best_imp) {
1488 * If the improvement from just moving env->p direction is
1489 * better than swapping tasks around, check if a move is
1490 * possible. Store a slightly smaller score than moveimp,
1491 * so an actually idle CPU will win.
1493 if (!load_too_imbalanced(src_load, dst_load, env)) {
1500 if (imp <= env->best_imp)
1504 load = task_h_load(cur);
1509 if (load_too_imbalanced(src_load, dst_load, env))
1513 * One idle CPU per node is evaluated for a task numa move.
1514 * Call select_idle_sibling to maybe find a better one.
1517 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1520 task_numa_assign(env, cur, imp);
1525 static void task_numa_find_cpu(struct task_numa_env *env,
1526 long taskimp, long groupimp)
1530 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1531 /* Skip this CPU if the source task cannot migrate */
1532 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1536 task_numa_compare(env, taskimp, groupimp);
1540 /* Only move tasks to a NUMA node less busy than the current node. */
1541 static bool numa_has_capacity(struct task_numa_env *env)
1543 struct numa_stats *src = &env->src_stats;
1544 struct numa_stats *dst = &env->dst_stats;
1546 if (src->has_free_capacity && !dst->has_free_capacity)
1550 * Only consider a task move if the source has a higher load
1551 * than the destination, corrected for CPU capacity on each node.
1553 * src->load dst->load
1554 * --------------------- vs ---------------------
1555 * src->compute_capacity dst->compute_capacity
1557 if (src->load * dst->compute_capacity * env->imbalance_pct >
1559 dst->load * src->compute_capacity * 100)
1565 static int task_numa_migrate(struct task_struct *p)
1567 struct task_numa_env env = {
1570 .src_cpu = task_cpu(p),
1571 .src_nid = task_node(p),
1573 .imbalance_pct = 112,
1579 struct sched_domain *sd;
1580 unsigned long taskweight, groupweight;
1582 long taskimp, groupimp;
1585 * Pick the lowest SD_NUMA domain, as that would have the smallest
1586 * imbalance and would be the first to start moving tasks about.
1588 * And we want to avoid any moving of tasks about, as that would create
1589 * random movement of tasks -- counter the numa conditions we're trying
1593 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1595 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1599 * Cpusets can break the scheduler domain tree into smaller
1600 * balance domains, some of which do not cross NUMA boundaries.
1601 * Tasks that are "trapped" in such domains cannot be migrated
1602 * elsewhere, so there is no point in (re)trying.
1604 if (unlikely(!sd)) {
1605 p->numa_preferred_nid = task_node(p);
1609 env.dst_nid = p->numa_preferred_nid;
1610 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1611 taskweight = task_weight(p, env.src_nid, dist);
1612 groupweight = group_weight(p, env.src_nid, dist);
1613 update_numa_stats(&env.src_stats, env.src_nid);
1614 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1615 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1616 update_numa_stats(&env.dst_stats, env.dst_nid);
1618 /* Try to find a spot on the preferred nid. */
1619 if (numa_has_capacity(&env))
1620 task_numa_find_cpu(&env, taskimp, groupimp);
1623 * Look at other nodes in these cases:
1624 * - there is no space available on the preferred_nid
1625 * - the task is part of a numa_group that is interleaved across
1626 * multiple NUMA nodes; in order to better consolidate the group,
1627 * we need to check other locations.
1629 if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1630 for_each_online_node(nid) {
1631 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1634 dist = node_distance(env.src_nid, env.dst_nid);
1635 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1637 taskweight = task_weight(p, env.src_nid, dist);
1638 groupweight = group_weight(p, env.src_nid, dist);
1641 /* Only consider nodes where both task and groups benefit */
1642 taskimp = task_weight(p, nid, dist) - taskweight;
1643 groupimp = group_weight(p, nid, dist) - groupweight;
1644 if (taskimp < 0 && groupimp < 0)
1649 update_numa_stats(&env.dst_stats, env.dst_nid);
1650 if (numa_has_capacity(&env))
1651 task_numa_find_cpu(&env, taskimp, groupimp);
1656 * If the task is part of a workload that spans multiple NUMA nodes,
1657 * and is migrating into one of the workload's active nodes, remember
1658 * this node as the task's preferred numa node, so the workload can
1660 * A task that migrated to a second choice node will be better off
1661 * trying for a better one later. Do not set the preferred node here.
1663 if (p->numa_group) {
1664 struct numa_group *ng = p->numa_group;
1666 if (env.best_cpu == -1)
1671 if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1672 sched_setnuma(p, env.dst_nid);
1675 /* No better CPU than the current one was found. */
1676 if (env.best_cpu == -1)
1680 * Reset the scan period if the task is being rescheduled on an
1681 * alternative node to recheck if the tasks is now properly placed.
1683 p->numa_scan_period = task_scan_min(p);
1685 if (env.best_task == NULL) {
1686 ret = migrate_task_to(p, env.best_cpu);
1688 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1692 ret = migrate_swap(p, env.best_task);
1694 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1695 put_task_struct(env.best_task);
1699 /* Attempt to migrate a task to a CPU on the preferred node. */
1700 static void numa_migrate_preferred(struct task_struct *p)
1702 unsigned long interval = HZ;
1704 /* This task has no NUMA fault statistics yet */
1705 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1708 /* Periodically retry migrating the task to the preferred node */
1709 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1710 p->numa_migrate_retry = jiffies + interval;
1712 /* Success if task is already running on preferred CPU */
1713 if (task_node(p) == p->numa_preferred_nid)
1716 /* Otherwise, try migrate to a CPU on the preferred node */
1717 task_numa_migrate(p);
1721 * Find out how many nodes on the workload is actively running on. Do this by
1722 * tracking the nodes from which NUMA hinting faults are triggered. This can
1723 * be different from the set of nodes where the workload's memory is currently
1726 static void numa_group_count_active_nodes(struct numa_group *numa_group)
1728 unsigned long faults, max_faults = 0;
1729 int nid, active_nodes = 0;
1731 for_each_online_node(nid) {
1732 faults = group_faults_cpu(numa_group, nid);
1733 if (faults > max_faults)
1734 max_faults = faults;
1737 for_each_online_node(nid) {
1738 faults = group_faults_cpu(numa_group, nid);
1739 if (faults * ACTIVE_NODE_FRACTION > max_faults)
1743 numa_group->max_faults_cpu = max_faults;
1744 numa_group->active_nodes = active_nodes;
1748 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1749 * increments. The more local the fault statistics are, the higher the scan
1750 * period will be for the next scan window. If local/(local+remote) ratio is
1751 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1752 * the scan period will decrease. Aim for 70% local accesses.
1754 #define NUMA_PERIOD_SLOTS 10
1755 #define NUMA_PERIOD_THRESHOLD 7
1758 * Increase the scan period (slow down scanning) if the majority of
1759 * our memory is already on our local node, or if the majority of
1760 * the page accesses are shared with other processes.
1761 * Otherwise, decrease the scan period.
1763 static void update_task_scan_period(struct task_struct *p,
1764 unsigned long shared, unsigned long private)
1766 unsigned int period_slot;
1770 unsigned long remote = p->numa_faults_locality[0];
1771 unsigned long local = p->numa_faults_locality[1];
1774 * If there were no record hinting faults then either the task is
1775 * completely idle or all activity is areas that are not of interest
1776 * to automatic numa balancing. Related to that, if there were failed
1777 * migration then it implies we are migrating too quickly or the local
1778 * node is overloaded. In either case, scan slower
1780 if (local + shared == 0 || p->numa_faults_locality[2]) {
1781 p->numa_scan_period = min(p->numa_scan_period_max,
1782 p->numa_scan_period << 1);
1784 p->mm->numa_next_scan = jiffies +
1785 msecs_to_jiffies(p->numa_scan_period);
1791 * Prepare to scale scan period relative to the current period.
1792 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1793 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1794 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1796 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1797 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1798 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1799 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1802 diff = slot * period_slot;
1804 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1807 * Scale scan rate increases based on sharing. There is an
1808 * inverse relationship between the degree of sharing and
1809 * the adjustment made to the scanning period. Broadly
1810 * speaking the intent is that there is little point
1811 * scanning faster if shared accesses dominate as it may
1812 * simply bounce migrations uselessly
1814 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1815 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1818 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1819 task_scan_min(p), task_scan_max(p));
1820 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1824 * Get the fraction of time the task has been running since the last
1825 * NUMA placement cycle. The scheduler keeps similar statistics, but
1826 * decays those on a 32ms period, which is orders of magnitude off
1827 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1828 * stats only if the task is so new there are no NUMA statistics yet.
1830 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1832 u64 runtime, delta, now;
1833 /* Use the start of this time slice to avoid calculations. */
1834 now = p->se.exec_start;
1835 runtime = p->se.sum_exec_runtime;
1837 if (p->last_task_numa_placement) {
1838 delta = runtime - p->last_sum_exec_runtime;
1839 *period = now - p->last_task_numa_placement;
1841 delta = p->se.avg.load_sum / p->se.load.weight;
1842 *period = LOAD_AVG_MAX;
1845 p->last_sum_exec_runtime = runtime;
1846 p->last_task_numa_placement = now;
1852 * Determine the preferred nid for a task in a numa_group. This needs to
1853 * be done in a way that produces consistent results with group_weight,
1854 * otherwise workloads might not converge.
1856 static int preferred_group_nid(struct task_struct *p, int nid)
1861 /* Direct connections between all NUMA nodes. */
1862 if (sched_numa_topology_type == NUMA_DIRECT)
1866 * On a system with glueless mesh NUMA topology, group_weight
1867 * scores nodes according to the number of NUMA hinting faults on
1868 * both the node itself, and on nearby nodes.
1870 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1871 unsigned long score, max_score = 0;
1872 int node, max_node = nid;
1874 dist = sched_max_numa_distance;
1876 for_each_online_node(node) {
1877 score = group_weight(p, node, dist);
1878 if (score > max_score) {
1887 * Finding the preferred nid in a system with NUMA backplane
1888 * interconnect topology is more involved. The goal is to locate
1889 * tasks from numa_groups near each other in the system, and
1890 * untangle workloads from different sides of the system. This requires
1891 * searching down the hierarchy of node groups, recursively searching
1892 * inside the highest scoring group of nodes. The nodemask tricks
1893 * keep the complexity of the search down.
1895 nodes = node_online_map;
1896 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1897 unsigned long max_faults = 0;
1898 nodemask_t max_group = NODE_MASK_NONE;
1901 /* Are there nodes at this distance from each other? */
1902 if (!find_numa_distance(dist))
1905 for_each_node_mask(a, nodes) {
1906 unsigned long faults = 0;
1907 nodemask_t this_group;
1908 nodes_clear(this_group);
1910 /* Sum group's NUMA faults; includes a==b case. */
1911 for_each_node_mask(b, nodes) {
1912 if (node_distance(a, b) < dist) {
1913 faults += group_faults(p, b);
1914 node_set(b, this_group);
1915 node_clear(b, nodes);
1919 /* Remember the top group. */
1920 if (faults > max_faults) {
1921 max_faults = faults;
1922 max_group = this_group;
1924 * subtle: at the smallest distance there is
1925 * just one node left in each "group", the
1926 * winner is the preferred nid.
1931 /* Next round, evaluate the nodes within max_group. */
1939 static void task_numa_placement(struct task_struct *p)
1941 int seq, nid, max_nid = -1, max_group_nid = -1;
1942 unsigned long max_faults = 0, max_group_faults = 0;
1943 unsigned long fault_types[2] = { 0, 0 };
1944 unsigned long total_faults;
1945 u64 runtime, period;
1946 spinlock_t *group_lock = NULL;
1949 * The p->mm->numa_scan_seq field gets updated without
1950 * exclusive access. Use READ_ONCE() here to ensure
1951 * that the field is read in a single access:
1953 seq = READ_ONCE(p->mm->numa_scan_seq);
1954 if (p->numa_scan_seq == seq)
1956 p->numa_scan_seq = seq;
1957 p->numa_scan_period_max = task_scan_max(p);
1959 total_faults = p->numa_faults_locality[0] +
1960 p->numa_faults_locality[1];
1961 runtime = numa_get_avg_runtime(p, &period);
1963 /* If the task is part of a group prevent parallel updates to group stats */
1964 if (p->numa_group) {
1965 group_lock = &p->numa_group->lock;
1966 spin_lock_irq(group_lock);
1969 /* Find the node with the highest number of faults */
1970 for_each_online_node(nid) {
1971 /* Keep track of the offsets in numa_faults array */
1972 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1973 unsigned long faults = 0, group_faults = 0;
1976 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1977 long diff, f_diff, f_weight;
1979 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1980 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1981 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1982 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1984 /* Decay existing window, copy faults since last scan */
1985 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1986 fault_types[priv] += p->numa_faults[membuf_idx];
1987 p->numa_faults[membuf_idx] = 0;
1990 * Normalize the faults_from, so all tasks in a group
1991 * count according to CPU use, instead of by the raw
1992 * number of faults. Tasks with little runtime have
1993 * little over-all impact on throughput, and thus their
1994 * faults are less important.
1996 f_weight = div64_u64(runtime << 16, period + 1);
1997 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1999 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
2000 p->numa_faults[cpubuf_idx] = 0;
2002 p->numa_faults[mem_idx] += diff;
2003 p->numa_faults[cpu_idx] += f_diff;
2004 faults += p->numa_faults[mem_idx];
2005 p->total_numa_faults += diff;
2006 if (p->numa_group) {
2008 * safe because we can only change our own group
2010 * mem_idx represents the offset for a given
2011 * nid and priv in a specific region because it
2012 * is at the beginning of the numa_faults array.
2014 p->numa_group->faults[mem_idx] += diff;
2015 p->numa_group->faults_cpu[mem_idx] += f_diff;
2016 p->numa_group->total_faults += diff;
2017 group_faults += p->numa_group->faults[mem_idx];
2021 if (faults > max_faults) {
2022 max_faults = faults;
2026 if (group_faults > max_group_faults) {
2027 max_group_faults = group_faults;
2028 max_group_nid = nid;
2032 update_task_scan_period(p, fault_types[0], fault_types[1]);
2034 if (p->numa_group) {
2035 numa_group_count_active_nodes(p->numa_group);
2036 spin_unlock_irq(group_lock);
2037 max_nid = preferred_group_nid(p, max_group_nid);
2041 /* Set the new preferred node */
2042 if (max_nid != p->numa_preferred_nid)
2043 sched_setnuma(p, max_nid);
2045 if (task_node(p) != p->numa_preferred_nid)
2046 numa_migrate_preferred(p);
2050 static inline int get_numa_group(struct numa_group *grp)
2052 return atomic_inc_not_zero(&grp->refcount);
2055 static inline void put_numa_group(struct numa_group *grp)
2057 if (atomic_dec_and_test(&grp->refcount))
2058 kfree_rcu(grp, rcu);
2061 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
2064 struct numa_group *grp, *my_grp;
2065 struct task_struct *tsk;
2067 int cpu = cpupid_to_cpu(cpupid);
2070 if (unlikely(!p->numa_group)) {
2071 unsigned int size = sizeof(struct numa_group) +
2072 4*nr_node_ids*sizeof(unsigned long);
2074 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
2078 atomic_set(&grp->refcount, 1);
2079 grp->active_nodes = 1;
2080 grp->max_faults_cpu = 0;
2081 spin_lock_init(&grp->lock);
2083 /* Second half of the array tracks nids where faults happen */
2084 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
2087 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2088 grp->faults[i] = p->numa_faults[i];
2090 grp->total_faults = p->total_numa_faults;
2093 rcu_assign_pointer(p->numa_group, grp);
2097 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2099 if (!cpupid_match_pid(tsk, cpupid))
2102 grp = rcu_dereference(tsk->numa_group);
2106 my_grp = p->numa_group;
2111 * Only join the other group if its bigger; if we're the bigger group,
2112 * the other task will join us.
2114 if (my_grp->nr_tasks > grp->nr_tasks)
2118 * Tie-break on the grp address.
2120 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2123 /* Always join threads in the same process. */
2124 if (tsk->mm == current->mm)
2127 /* Simple filter to avoid false positives due to PID collisions */
2128 if (flags & TNF_SHARED)
2131 /* Update priv based on whether false sharing was detected */
2134 if (join && !get_numa_group(grp))
2142 BUG_ON(irqs_disabled());
2143 double_lock_irq(&my_grp->lock, &grp->lock);
2145 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2146 my_grp->faults[i] -= p->numa_faults[i];
2147 grp->faults[i] += p->numa_faults[i];
2149 my_grp->total_faults -= p->total_numa_faults;
2150 grp->total_faults += p->total_numa_faults;
2155 spin_unlock(&my_grp->lock);
2156 spin_unlock_irq(&grp->lock);
2158 rcu_assign_pointer(p->numa_group, grp);
2160 put_numa_group(my_grp);
2168 void task_numa_free(struct task_struct *p)
2170 struct numa_group *grp = p->numa_group;
2171 void *numa_faults = p->numa_faults;
2172 unsigned long flags;
2176 spin_lock_irqsave(&grp->lock, flags);
2177 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2178 grp->faults[i] -= p->numa_faults[i];
2179 grp->total_faults -= p->total_numa_faults;
2182 spin_unlock_irqrestore(&grp->lock, flags);
2183 RCU_INIT_POINTER(p->numa_group, NULL);
2184 put_numa_group(grp);
2187 p->numa_faults = NULL;
2192 * Got a PROT_NONE fault for a page on @node.
2194 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2196 struct task_struct *p = current;
2197 bool migrated = flags & TNF_MIGRATED;
2198 int cpu_node = task_node(current);
2199 int local = !!(flags & TNF_FAULT_LOCAL);
2200 struct numa_group *ng;
2203 if (!static_branch_likely(&sched_numa_balancing))
2206 /* for example, ksmd faulting in a user's mm */
2210 /* Allocate buffer to track faults on a per-node basis */
2211 if (unlikely(!p->numa_faults)) {
2212 int size = sizeof(*p->numa_faults) *
2213 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2215 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2216 if (!p->numa_faults)
2219 p->total_numa_faults = 0;
2220 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2224 * First accesses are treated as private, otherwise consider accesses
2225 * to be private if the accessing pid has not changed
2227 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2230 priv = cpupid_match_pid(p, last_cpupid);
2231 if (!priv && !(flags & TNF_NO_GROUP))
2232 task_numa_group(p, last_cpupid, flags, &priv);
2236 * If a workload spans multiple NUMA nodes, a shared fault that
2237 * occurs wholly within the set of nodes that the workload is
2238 * actively using should be counted as local. This allows the
2239 * scan rate to slow down when a workload has settled down.
2242 if (!priv && !local && ng && ng->active_nodes > 1 &&
2243 numa_is_active_node(cpu_node, ng) &&
2244 numa_is_active_node(mem_node, ng))
2247 task_numa_placement(p);
2250 * Retry task to preferred node migration periodically, in case it
2251 * case it previously failed, or the scheduler moved us.
2253 if (time_after(jiffies, p->numa_migrate_retry))
2254 numa_migrate_preferred(p);
2257 p->numa_pages_migrated += pages;
2258 if (flags & TNF_MIGRATE_FAIL)
2259 p->numa_faults_locality[2] += pages;
2261 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2262 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2263 p->numa_faults_locality[local] += pages;
2266 static void reset_ptenuma_scan(struct task_struct *p)
2269 * We only did a read acquisition of the mmap sem, so
2270 * p->mm->numa_scan_seq is written to without exclusive access
2271 * and the update is not guaranteed to be atomic. That's not
2272 * much of an issue though, since this is just used for
2273 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2274 * expensive, to avoid any form of compiler optimizations:
2276 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2277 p->mm->numa_scan_offset = 0;
2281 * The expensive part of numa migration is done from task_work context.
2282 * Triggered from task_tick_numa().
2284 void task_numa_work(struct callback_head *work)
2286 unsigned long migrate, next_scan, now = jiffies;
2287 struct task_struct *p = current;
2288 struct mm_struct *mm = p->mm;
2289 u64 runtime = p->se.sum_exec_runtime;
2290 struct vm_area_struct *vma;
2291 unsigned long start, end;
2292 unsigned long nr_pte_updates = 0;
2293 long pages, virtpages;
2295 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2297 work->next = work; /* protect against double add */
2299 * Who cares about NUMA placement when they're dying.
2301 * NOTE: make sure not to dereference p->mm before this check,
2302 * exit_task_work() happens _after_ exit_mm() so we could be called
2303 * without p->mm even though we still had it when we enqueued this
2306 if (p->flags & PF_EXITING)
2309 if (!mm->numa_next_scan) {
2310 mm->numa_next_scan = now +
2311 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2315 * Enforce maximal scan/migration frequency..
2317 migrate = mm->numa_next_scan;
2318 if (time_before(now, migrate))
2321 if (p->numa_scan_period == 0) {
2322 p->numa_scan_period_max = task_scan_max(p);
2323 p->numa_scan_period = task_scan_min(p);
2326 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2327 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2331 * Delay this task enough that another task of this mm will likely win
2332 * the next time around.
2334 p->node_stamp += 2 * TICK_NSEC;
2336 start = mm->numa_scan_offset;
2337 pages = sysctl_numa_balancing_scan_size;
2338 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2339 virtpages = pages * 8; /* Scan up to this much virtual space */
2344 down_read(&mm->mmap_sem);
2345 vma = find_vma(mm, start);
2347 reset_ptenuma_scan(p);
2351 for (; vma; vma = vma->vm_next) {
2352 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2353 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2358 * Shared library pages mapped by multiple processes are not
2359 * migrated as it is expected they are cache replicated. Avoid
2360 * hinting faults in read-only file-backed mappings or the vdso
2361 * as migrating the pages will be of marginal benefit.
2364 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2368 * Skip inaccessible VMAs to avoid any confusion between
2369 * PROT_NONE and NUMA hinting ptes
2371 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2375 start = max(start, vma->vm_start);
2376 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2377 end = min(end, vma->vm_end);
2378 nr_pte_updates = change_prot_numa(vma, start, end);
2381 * Try to scan sysctl_numa_balancing_size worth of
2382 * hpages that have at least one present PTE that
2383 * is not already pte-numa. If the VMA contains
2384 * areas that are unused or already full of prot_numa
2385 * PTEs, scan up to virtpages, to skip through those
2389 pages -= (end - start) >> PAGE_SHIFT;
2390 virtpages -= (end - start) >> PAGE_SHIFT;
2393 if (pages <= 0 || virtpages <= 0)
2397 } while (end != vma->vm_end);
2402 * It is possible to reach the end of the VMA list but the last few
2403 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2404 * would find the !migratable VMA on the next scan but not reset the
2405 * scanner to the start so check it now.
2408 mm->numa_scan_offset = start;
2410 reset_ptenuma_scan(p);
2411 up_read(&mm->mmap_sem);
2414 * Make sure tasks use at least 32x as much time to run other code
2415 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2416 * Usually update_task_scan_period slows down scanning enough; on an
2417 * overloaded system we need to limit overhead on a per task basis.
2419 if (unlikely(p->se.sum_exec_runtime != runtime)) {
2420 u64 diff = p->se.sum_exec_runtime - runtime;
2421 p->node_stamp += 32 * diff;
2426 * Drive the periodic memory faults..
2428 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2430 struct callback_head *work = &curr->numa_work;
2434 * We don't care about NUMA placement if we don't have memory.
2436 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2440 * Using runtime rather than walltime has the dual advantage that
2441 * we (mostly) drive the selection from busy threads and that the
2442 * task needs to have done some actual work before we bother with
2445 now = curr->se.sum_exec_runtime;
2446 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2448 if (now > curr->node_stamp + period) {
2449 if (!curr->node_stamp)
2450 curr->numa_scan_period = task_scan_min(curr);
2451 curr->node_stamp += period;
2453 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2454 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2455 task_work_add(curr, work, true);
2460 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2464 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2468 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2471 #endif /* CONFIG_NUMA_BALANCING */
2474 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2476 update_load_add(&cfs_rq->load, se->load.weight);
2477 if (!parent_entity(se))
2478 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2480 if (entity_is_task(se)) {
2481 struct rq *rq = rq_of(cfs_rq);
2483 account_numa_enqueue(rq, task_of(se));
2484 list_add(&se->group_node, &rq->cfs_tasks);
2487 cfs_rq->nr_running++;
2491 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2493 update_load_sub(&cfs_rq->load, se->load.weight);
2494 if (!parent_entity(se))
2495 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2497 if (entity_is_task(se)) {
2498 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2499 list_del_init(&se->group_node);
2502 cfs_rq->nr_running--;
2505 #ifdef CONFIG_FAIR_GROUP_SCHED
2507 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2509 long tg_weight, load, shares;
2512 * This really should be: cfs_rq->avg.load_avg, but instead we use
2513 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
2514 * the shares for small weight interactive tasks.
2516 load = scale_load_down(cfs_rq->load.weight);
2518 tg_weight = atomic_long_read(&tg->load_avg);
2520 /* Ensure tg_weight >= load */
2521 tg_weight -= cfs_rq->tg_load_avg_contrib;
2524 shares = (tg->shares * load);
2526 shares /= tg_weight;
2528 if (shares < MIN_SHARES)
2529 shares = MIN_SHARES;
2530 if (shares > tg->shares)
2531 shares = tg->shares;
2535 # else /* CONFIG_SMP */
2536 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2540 # endif /* CONFIG_SMP */
2542 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2543 unsigned long weight)
2546 /* commit outstanding execution time */
2547 if (cfs_rq->curr == se)
2548 update_curr(cfs_rq);
2549 account_entity_dequeue(cfs_rq, se);
2552 update_load_set(&se->load, weight);
2555 account_entity_enqueue(cfs_rq, se);
2558 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2560 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2562 struct task_group *tg;
2563 struct sched_entity *se;
2567 se = tg->se[cpu_of(rq_of(cfs_rq))];
2568 if (!se || throttled_hierarchy(cfs_rq))
2571 if (likely(se->load.weight == tg->shares))
2574 shares = calc_cfs_shares(cfs_rq, tg);
2576 reweight_entity(cfs_rq_of(se), se, shares);
2578 #else /* CONFIG_FAIR_GROUP_SCHED */
2579 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2582 #endif /* CONFIG_FAIR_GROUP_SCHED */
2585 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2586 static const u32 runnable_avg_yN_inv[] = {
2587 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2588 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2589 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2590 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2591 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2592 0x85aac367, 0x82cd8698,
2596 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2597 * over-estimates when re-combining.
2599 static const u32 runnable_avg_yN_sum[] = {
2600 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2601 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2602 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2606 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
2607 * lower integers. See Documentation/scheduler/sched-avg.txt how these
2610 static const u32 __accumulated_sum_N32[] = {
2611 0, 23371, 35056, 40899, 43820, 45281,
2612 46011, 46376, 46559, 46650, 46696, 46719,
2617 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2619 static __always_inline u64 decay_load(u64 val, u64 n)
2621 unsigned int local_n;
2625 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2628 /* after bounds checking we can collapse to 32-bit */
2632 * As y^PERIOD = 1/2, we can combine
2633 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2634 * With a look-up table which covers y^n (n<PERIOD)
2636 * To achieve constant time decay_load.
2638 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2639 val >>= local_n / LOAD_AVG_PERIOD;
2640 local_n %= LOAD_AVG_PERIOD;
2643 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2648 * For updates fully spanning n periods, the contribution to runnable
2649 * average will be: \Sum 1024*y^n
2651 * We can compute this reasonably efficiently by combining:
2652 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2654 static u32 __compute_runnable_contrib(u64 n)
2658 if (likely(n <= LOAD_AVG_PERIOD))
2659 return runnable_avg_yN_sum[n];
2660 else if (unlikely(n >= LOAD_AVG_MAX_N))
2661 return LOAD_AVG_MAX;
2663 /* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
2664 contrib = __accumulated_sum_N32[n/LOAD_AVG_PERIOD];
2665 n %= LOAD_AVG_PERIOD;
2666 contrib = decay_load(contrib, n);
2667 return contrib + runnable_avg_yN_sum[n];
2670 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2673 * We can represent the historical contribution to runnable average as the
2674 * coefficients of a geometric series. To do this we sub-divide our runnable
2675 * history into segments of approximately 1ms (1024us); label the segment that
2676 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2678 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2680 * (now) (~1ms ago) (~2ms ago)
2682 * Let u_i denote the fraction of p_i that the entity was runnable.
2684 * We then designate the fractions u_i as our co-efficients, yielding the
2685 * following representation of historical load:
2686 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2688 * We choose y based on the with of a reasonably scheduling period, fixing:
2691 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2692 * approximately half as much as the contribution to load within the last ms
2695 * When a period "rolls over" and we have new u_0`, multiplying the previous
2696 * sum again by y is sufficient to update:
2697 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2698 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2700 static __always_inline int
2701 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2702 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2704 u64 delta, scaled_delta, periods;
2706 unsigned int delta_w, scaled_delta_w, decayed = 0;
2707 unsigned long scale_freq, scale_cpu;
2709 delta = now - sa->last_update_time;
2711 * This should only happen when time goes backwards, which it
2712 * unfortunately does during sched clock init when we swap over to TSC.
2714 if ((s64)delta < 0) {
2715 sa->last_update_time = now;
2720 * Use 1024ns as the unit of measurement since it's a reasonable
2721 * approximation of 1us and fast to compute.
2726 sa->last_update_time = now;
2728 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2729 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2731 /* delta_w is the amount already accumulated against our next period */
2732 delta_w = sa->period_contrib;
2733 if (delta + delta_w >= 1024) {
2736 /* how much left for next period will start over, we don't know yet */
2737 sa->period_contrib = 0;
2740 * Now that we know we're crossing a period boundary, figure
2741 * out how much from delta we need to complete the current
2742 * period and accrue it.
2744 delta_w = 1024 - delta_w;
2745 scaled_delta_w = cap_scale(delta_w, scale_freq);
2747 sa->load_sum += weight * scaled_delta_w;
2749 cfs_rq->runnable_load_sum +=
2750 weight * scaled_delta_w;
2754 sa->util_sum += scaled_delta_w * scale_cpu;
2758 /* Figure out how many additional periods this update spans */
2759 periods = delta / 1024;
2762 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2764 cfs_rq->runnable_load_sum =
2765 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2767 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2769 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2770 contrib = __compute_runnable_contrib(periods);
2771 contrib = cap_scale(contrib, scale_freq);
2773 sa->load_sum += weight * contrib;
2775 cfs_rq->runnable_load_sum += weight * contrib;
2778 sa->util_sum += contrib * scale_cpu;
2781 /* Remainder of delta accrued against u_0` */
2782 scaled_delta = cap_scale(delta, scale_freq);
2784 sa->load_sum += weight * scaled_delta;
2786 cfs_rq->runnable_load_sum += weight * scaled_delta;
2789 sa->util_sum += scaled_delta * scale_cpu;
2791 sa->period_contrib += delta;
2794 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2796 cfs_rq->runnable_load_avg =
2797 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2799 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2805 #ifdef CONFIG_FAIR_GROUP_SCHED
2807 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2808 * and effective_load (which is not done because it is too costly).
2810 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2812 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2815 * No need to update load_avg for root_task_group as it is not used.
2817 if (cfs_rq->tg == &root_task_group)
2820 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2821 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2822 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2827 * Called within set_task_rq() right before setting a task's cpu. The
2828 * caller only guarantees p->pi_lock is held; no other assumptions,
2829 * including the state of rq->lock, should be made.
2831 void set_task_rq_fair(struct sched_entity *se,
2832 struct cfs_rq *prev, struct cfs_rq *next)
2834 if (!sched_feat(ATTACH_AGE_LOAD))
2838 * We are supposed to update the task to "current" time, then its up to
2839 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2840 * getting what current time is, so simply throw away the out-of-date
2841 * time. This will result in the wakee task is less decayed, but giving
2842 * the wakee more load sounds not bad.
2844 if (se->avg.last_update_time && prev) {
2845 u64 p_last_update_time;
2846 u64 n_last_update_time;
2848 #ifndef CONFIG_64BIT
2849 u64 p_last_update_time_copy;
2850 u64 n_last_update_time_copy;
2853 p_last_update_time_copy = prev->load_last_update_time_copy;
2854 n_last_update_time_copy = next->load_last_update_time_copy;
2858 p_last_update_time = prev->avg.last_update_time;
2859 n_last_update_time = next->avg.last_update_time;
2861 } while (p_last_update_time != p_last_update_time_copy ||
2862 n_last_update_time != n_last_update_time_copy);
2864 p_last_update_time = prev->avg.last_update_time;
2865 n_last_update_time = next->avg.last_update_time;
2867 __update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
2868 &se->avg, 0, 0, NULL);
2869 se->avg.last_update_time = n_last_update_time;
2872 #else /* CONFIG_FAIR_GROUP_SCHED */
2873 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2874 #endif /* CONFIG_FAIR_GROUP_SCHED */
2876 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
2878 if (&this_rq()->cfs == cfs_rq) {
2879 struct rq *rq = rq_of(cfs_rq);
2882 * There are a few boundary cases this might miss but it should
2883 * get called often enough that that should (hopefully) not be
2884 * a real problem -- added to that it only calls on the local
2885 * CPU, so if we enqueue remotely we'll miss an update, but
2886 * the next tick/schedule should update.
2888 * It will not get called when we go idle, because the idle
2889 * thread is a different class (!fair), nor will the utilization
2890 * number include things like RT tasks.
2892 * As is, the util number is not freq-invariant (we'd have to
2893 * implement arch_scale_freq_capacity() for that).
2897 cpufreq_update_util(rq_clock(rq), 0);
2902 * Unsigned subtract and clamp on underflow.
2904 * Explicitly do a load-store to ensure the intermediate value never hits
2905 * memory. This allows lockless observations without ever seeing the negative
2908 #define sub_positive(_ptr, _val) do { \
2909 typeof(_ptr) ptr = (_ptr); \
2910 typeof(*ptr) val = (_val); \
2911 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2915 WRITE_ONCE(*ptr, res); \
2919 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
2920 * @now: current time, as per cfs_rq_clock_task()
2921 * @cfs_rq: cfs_rq to update
2922 * @update_freq: should we call cfs_rq_util_change() or will the call do so
2924 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
2925 * avg. The immediate corollary is that all (fair) tasks must be attached, see
2926 * post_init_entity_util_avg().
2928 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
2930 * Returns true if the load decayed or we removed utilization. It is expected
2931 * that one calls update_tg_load_avg() on this condition, but after you've
2932 * modified the cfs_rq avg (attach/detach), such that we propagate the new
2936 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
2938 struct sched_avg *sa = &cfs_rq->avg;
2939 int decayed, removed_load = 0, removed_util = 0;
2941 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2942 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2943 sub_positive(&sa->load_avg, r);
2944 sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
2948 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2949 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2950 sub_positive(&sa->util_avg, r);
2951 sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
2955 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2956 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2958 #ifndef CONFIG_64BIT
2960 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2963 if (update_freq && (decayed || removed_util))
2964 cfs_rq_util_change(cfs_rq);
2966 return decayed || removed_load;
2969 /* Update task and its cfs_rq load average */
2970 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2972 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2973 u64 now = cfs_rq_clock_task(cfs_rq);
2974 struct rq *rq = rq_of(cfs_rq);
2975 int cpu = cpu_of(rq);
2978 * Track task load average for carrying it to new CPU after migrated, and
2979 * track group sched_entity load average for task_h_load calc in migration
2981 __update_load_avg(now, cpu, &se->avg,
2982 se->on_rq * scale_load_down(se->load.weight),
2983 cfs_rq->curr == se, NULL);
2985 if (update_cfs_rq_load_avg(now, cfs_rq, true) && update_tg)
2986 update_tg_load_avg(cfs_rq, 0);
2990 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
2991 * @cfs_rq: cfs_rq to attach to
2992 * @se: sched_entity to attach
2994 * Must call update_cfs_rq_load_avg() before this, since we rely on
2995 * cfs_rq->avg.last_update_time being current.
2997 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2999 if (!sched_feat(ATTACH_AGE_LOAD))
3003 * If we got migrated (either between CPUs or between cgroups) we'll
3004 * have aged the average right before clearing @last_update_time.
3006 * Or we're fresh through post_init_entity_util_avg().
3008 if (se->avg.last_update_time) {
3009 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
3010 &se->avg, 0, 0, NULL);
3013 * XXX: we could have just aged the entire load away if we've been
3014 * absent from the fair class for too long.
3019 se->avg.last_update_time = cfs_rq->avg.last_update_time;
3020 cfs_rq->avg.load_avg += se->avg.load_avg;
3021 cfs_rq->avg.load_sum += se->avg.load_sum;
3022 cfs_rq->avg.util_avg += se->avg.util_avg;
3023 cfs_rq->avg.util_sum += se->avg.util_sum;
3025 cfs_rq_util_change(cfs_rq);
3029 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3030 * @cfs_rq: cfs_rq to detach from
3031 * @se: sched_entity to detach
3033 * Must call update_cfs_rq_load_avg() before this, since we rely on
3034 * cfs_rq->avg.last_update_time being current.
3036 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3038 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
3039 &se->avg, se->on_rq * scale_load_down(se->load.weight),
3040 cfs_rq->curr == se, NULL);
3042 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
3043 sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
3044 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
3045 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3047 cfs_rq_util_change(cfs_rq);
3050 /* Add the load generated by se into cfs_rq's load average */
3052 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3054 struct sched_avg *sa = &se->avg;
3055 u64 now = cfs_rq_clock_task(cfs_rq);
3056 int migrated, decayed;
3058 migrated = !sa->last_update_time;
3060 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3061 se->on_rq * scale_load_down(se->load.weight),
3062 cfs_rq->curr == se, NULL);
3065 decayed = update_cfs_rq_load_avg(now, cfs_rq, !migrated);
3067 cfs_rq->runnable_load_avg += sa->load_avg;
3068 cfs_rq->runnable_load_sum += sa->load_sum;
3071 attach_entity_load_avg(cfs_rq, se);
3073 if (decayed || migrated)
3074 update_tg_load_avg(cfs_rq, 0);
3077 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3079 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3081 update_load_avg(se, 1);
3083 cfs_rq->runnable_load_avg =
3084 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
3085 cfs_rq->runnable_load_sum =
3086 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3089 #ifndef CONFIG_64BIT
3090 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3092 u64 last_update_time_copy;
3093 u64 last_update_time;
3096 last_update_time_copy = cfs_rq->load_last_update_time_copy;
3098 last_update_time = cfs_rq->avg.last_update_time;
3099 } while (last_update_time != last_update_time_copy);
3101 return last_update_time;
3104 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
3106 return cfs_rq->avg.last_update_time;
3111 * Task first catches up with cfs_rq, and then subtract
3112 * itself from the cfs_rq (task must be off the queue now).
3114 void remove_entity_load_avg(struct sched_entity *se)
3116 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3117 u64 last_update_time;
3120 * tasks cannot exit without having gone through wake_up_new_task() ->
3121 * post_init_entity_util_avg() which will have added things to the
3122 * cfs_rq, so we can remove unconditionally.
3124 * Similarly for groups, they will have passed through
3125 * post_init_entity_util_avg() before unregister_sched_fair_group()
3129 last_update_time = cfs_rq_last_update_time(cfs_rq);
3131 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3132 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
3133 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3136 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
3138 return cfs_rq->runnable_load_avg;
3141 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
3143 return cfs_rq->avg.load_avg;
3146 static int idle_balance(struct rq *this_rq);
3148 #else /* CONFIG_SMP */
3151 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
3156 static inline void update_load_avg(struct sched_entity *se, int not_used)
3158 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3159 struct rq *rq = rq_of(cfs_rq);
3161 cpufreq_update_util(rq_clock(rq), 0);
3165 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3167 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3168 static inline void remove_entity_load_avg(struct sched_entity *se) {}
3171 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3173 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3175 static inline int idle_balance(struct rq *rq)
3180 #endif /* CONFIG_SMP */
3182 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3184 #ifdef CONFIG_SCHEDSTATS
3185 struct task_struct *tsk = NULL;
3187 if (entity_is_task(se))
3190 if (se->statistics.sleep_start) {
3191 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3196 if (unlikely(delta > se->statistics.sleep_max))
3197 se->statistics.sleep_max = delta;
3199 se->statistics.sleep_start = 0;
3200 se->statistics.sum_sleep_runtime += delta;
3203 account_scheduler_latency(tsk, delta >> 10, 1);
3204 trace_sched_stat_sleep(tsk, delta);
3207 if (se->statistics.block_start) {
3208 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3213 if (unlikely(delta > se->statistics.block_max))
3214 se->statistics.block_max = delta;
3216 se->statistics.block_start = 0;
3217 se->statistics.sum_sleep_runtime += delta;
3220 if (tsk->in_iowait) {
3221 se->statistics.iowait_sum += delta;
3222 se->statistics.iowait_count++;
3223 trace_sched_stat_iowait(tsk, delta);
3226 trace_sched_stat_blocked(tsk, delta);
3229 * Blocking time is in units of nanosecs, so shift by
3230 * 20 to get a milliseconds-range estimation of the
3231 * amount of time that the task spent sleeping:
3233 if (unlikely(prof_on == SLEEP_PROFILING)) {
3234 profile_hits(SLEEP_PROFILING,
3235 (void *)get_wchan(tsk),
3238 account_scheduler_latency(tsk, delta >> 10, 0);
3244 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
3246 #ifdef CONFIG_SCHED_DEBUG
3247 s64 d = se->vruntime - cfs_rq->min_vruntime;
3252 if (d > 3*sysctl_sched_latency)
3253 schedstat_inc(cfs_rq, nr_spread_over);
3258 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3260 u64 vruntime = cfs_rq->min_vruntime;
3263 * The 'current' period is already promised to the current tasks,
3264 * however the extra weight of the new task will slow them down a
3265 * little, place the new task so that it fits in the slot that
3266 * stays open at the end.
3268 if (initial && sched_feat(START_DEBIT))
3269 vruntime += sched_vslice(cfs_rq, se);
3271 /* sleeps up to a single latency don't count. */
3273 unsigned long thresh = sysctl_sched_latency;
3276 * Halve their sleep time's effect, to allow
3277 * for a gentler effect of sleepers:
3279 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3285 /* ensure we never gain time by being placed backwards. */
3286 se->vruntime = max_vruntime(se->vruntime, vruntime);
3289 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3291 static inline void check_schedstat_required(void)
3293 #ifdef CONFIG_SCHEDSTATS
3294 if (schedstat_enabled())
3297 /* Force schedstat enabled if a dependent tracepoint is active */
3298 if (trace_sched_stat_wait_enabled() ||
3299 trace_sched_stat_sleep_enabled() ||
3300 trace_sched_stat_iowait_enabled() ||
3301 trace_sched_stat_blocked_enabled() ||
3302 trace_sched_stat_runtime_enabled()) {
3303 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3304 "stat_blocked and stat_runtime require the "
3305 "kernel parameter schedstats=enabled or "
3306 "kernel.sched_schedstats=1\n");
3317 * update_min_vruntime()
3318 * vruntime -= min_vruntime
3322 * update_min_vruntime()
3323 * vruntime += min_vruntime
3325 * this way the vruntime transition between RQs is done when both
3326 * min_vruntime are up-to-date.
3330 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
3331 * vruntime -= min_vruntime
3335 * update_min_vruntime()
3336 * vruntime += min_vruntime
3338 * this way we don't have the most up-to-date min_vruntime on the originating
3339 * CPU and an up-to-date min_vruntime on the destination CPU.
3343 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3345 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
3346 bool curr = cfs_rq->curr == se;
3349 * If we're the current task, we must renormalise before calling
3353 se->vruntime += cfs_rq->min_vruntime;
3355 update_curr(cfs_rq);
3358 * Otherwise, renormalise after, such that we're placed at the current
3359 * moment in time, instead of some random moment in the past. Being
3360 * placed in the past could significantly boost this task to the
3361 * fairness detriment of existing tasks.
3363 if (renorm && !curr)
3364 se->vruntime += cfs_rq->min_vruntime;
3366 enqueue_entity_load_avg(cfs_rq, se);
3367 account_entity_enqueue(cfs_rq, se);
3368 update_cfs_shares(cfs_rq);
3370 if (flags & ENQUEUE_WAKEUP) {
3371 place_entity(cfs_rq, se, 0);
3372 if (schedstat_enabled())
3373 enqueue_sleeper(cfs_rq, se);
3376 check_schedstat_required();
3377 if (schedstat_enabled()) {
3378 update_stats_enqueue(cfs_rq, se);
3379 check_spread(cfs_rq, se);
3382 __enqueue_entity(cfs_rq, se);
3385 if (cfs_rq->nr_running == 1) {
3386 list_add_leaf_cfs_rq(cfs_rq);
3387 check_enqueue_throttle(cfs_rq);
3391 static void __clear_buddies_last(struct sched_entity *se)
3393 for_each_sched_entity(se) {
3394 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3395 if (cfs_rq->last != se)
3398 cfs_rq->last = NULL;
3402 static void __clear_buddies_next(struct sched_entity *se)
3404 for_each_sched_entity(se) {
3405 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3406 if (cfs_rq->next != se)
3409 cfs_rq->next = NULL;
3413 static void __clear_buddies_skip(struct sched_entity *se)
3415 for_each_sched_entity(se) {
3416 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3417 if (cfs_rq->skip != se)
3420 cfs_rq->skip = NULL;
3424 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3426 if (cfs_rq->last == se)
3427 __clear_buddies_last(se);
3429 if (cfs_rq->next == se)
3430 __clear_buddies_next(se);
3432 if (cfs_rq->skip == se)
3433 __clear_buddies_skip(se);
3436 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3439 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3442 * Update run-time statistics of the 'current'.
3444 update_curr(cfs_rq);
3445 dequeue_entity_load_avg(cfs_rq, se);
3447 if (schedstat_enabled())
3448 update_stats_dequeue(cfs_rq, se, flags);
3450 clear_buddies(cfs_rq, se);
3452 if (se != cfs_rq->curr)
3453 __dequeue_entity(cfs_rq, se);
3455 account_entity_dequeue(cfs_rq, se);
3458 * Normalize the entity after updating the min_vruntime because the
3459 * update can refer to the ->curr item and we need to reflect this
3460 * movement in our normalized position.
3462 if (!(flags & DEQUEUE_SLEEP))
3463 se->vruntime -= cfs_rq->min_vruntime;
3465 /* return excess runtime on last dequeue */
3466 return_cfs_rq_runtime(cfs_rq);
3468 update_min_vruntime(cfs_rq);
3469 update_cfs_shares(cfs_rq);
3473 * Preempt the current task with a newly woken task if needed:
3476 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3478 unsigned long ideal_runtime, delta_exec;
3479 struct sched_entity *se;
3482 ideal_runtime = sched_slice(cfs_rq, curr);
3483 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3484 if (delta_exec > ideal_runtime) {
3485 resched_curr(rq_of(cfs_rq));
3487 * The current task ran long enough, ensure it doesn't get
3488 * re-elected due to buddy favours.
3490 clear_buddies(cfs_rq, curr);
3495 * Ensure that a task that missed wakeup preemption by a
3496 * narrow margin doesn't have to wait for a full slice.
3497 * This also mitigates buddy induced latencies under load.
3499 if (delta_exec < sysctl_sched_min_granularity)
3502 se = __pick_first_entity(cfs_rq);
3503 delta = curr->vruntime - se->vruntime;
3508 if (delta > ideal_runtime)
3509 resched_curr(rq_of(cfs_rq));
3513 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3515 /* 'current' is not kept within the tree. */
3518 * Any task has to be enqueued before it get to execute on
3519 * a CPU. So account for the time it spent waiting on the
3522 if (schedstat_enabled())
3523 update_stats_wait_end(cfs_rq, se);
3524 __dequeue_entity(cfs_rq, se);
3525 update_load_avg(se, 1);
3528 update_stats_curr_start(cfs_rq, se);
3530 #ifdef CONFIG_SCHEDSTATS
3532 * Track our maximum slice length, if the CPU's load is at
3533 * least twice that of our own weight (i.e. dont track it
3534 * when there are only lesser-weight tasks around):
3536 if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3537 se->statistics.slice_max = max(se->statistics.slice_max,
3538 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3541 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3545 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3548 * Pick the next process, keeping these things in mind, in this order:
3549 * 1) keep things fair between processes/task groups
3550 * 2) pick the "next" process, since someone really wants that to run
3551 * 3) pick the "last" process, for cache locality
3552 * 4) do not run the "skip" process, if something else is available
3554 static struct sched_entity *
3555 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3557 struct sched_entity *left = __pick_first_entity(cfs_rq);
3558 struct sched_entity *se;
3561 * If curr is set we have to see if its left of the leftmost entity
3562 * still in the tree, provided there was anything in the tree at all.
3564 if (!left || (curr && entity_before(curr, left)))
3567 se = left; /* ideally we run the leftmost entity */
3570 * Avoid running the skip buddy, if running something else can
3571 * be done without getting too unfair.
3573 if (cfs_rq->skip == se) {
3574 struct sched_entity *second;
3577 second = __pick_first_entity(cfs_rq);
3579 second = __pick_next_entity(se);
3580 if (!second || (curr && entity_before(curr, second)))
3584 if (second && wakeup_preempt_entity(second, left) < 1)
3589 * Prefer last buddy, try to return the CPU to a preempted task.
3591 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3595 * Someone really wants this to run. If it's not unfair, run it.
3597 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3600 clear_buddies(cfs_rq, se);
3605 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3607 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3610 * If still on the runqueue then deactivate_task()
3611 * was not called and update_curr() has to be done:
3614 update_curr(cfs_rq);
3616 /* throttle cfs_rqs exceeding runtime */
3617 check_cfs_rq_runtime(cfs_rq);
3619 if (schedstat_enabled()) {
3620 check_spread(cfs_rq, prev);
3622 update_stats_wait_start(cfs_rq, prev);
3626 /* Put 'current' back into the tree. */
3627 __enqueue_entity(cfs_rq, prev);
3628 /* in !on_rq case, update occurred at dequeue */
3629 update_load_avg(prev, 0);
3631 cfs_rq->curr = NULL;
3635 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3638 * Update run-time statistics of the 'current'.
3640 update_curr(cfs_rq);
3643 * Ensure that runnable average is periodically updated.
3645 update_load_avg(curr, 1);
3646 update_cfs_shares(cfs_rq);
3648 #ifdef CONFIG_SCHED_HRTICK
3650 * queued ticks are scheduled to match the slice, so don't bother
3651 * validating it and just reschedule.
3654 resched_curr(rq_of(cfs_rq));
3658 * don't let the period tick interfere with the hrtick preemption
3660 if (!sched_feat(DOUBLE_TICK) &&
3661 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3665 if (cfs_rq->nr_running > 1)
3666 check_preempt_tick(cfs_rq, curr);
3670 /**************************************************
3671 * CFS bandwidth control machinery
3674 #ifdef CONFIG_CFS_BANDWIDTH
3676 #ifdef HAVE_JUMP_LABEL
3677 static struct static_key __cfs_bandwidth_used;
3679 static inline bool cfs_bandwidth_used(void)
3681 return static_key_false(&__cfs_bandwidth_used);
3684 void cfs_bandwidth_usage_inc(void)
3686 static_key_slow_inc(&__cfs_bandwidth_used);
3689 void cfs_bandwidth_usage_dec(void)
3691 static_key_slow_dec(&__cfs_bandwidth_used);
3693 #else /* HAVE_JUMP_LABEL */
3694 static bool cfs_bandwidth_used(void)
3699 void cfs_bandwidth_usage_inc(void) {}
3700 void cfs_bandwidth_usage_dec(void) {}
3701 #endif /* HAVE_JUMP_LABEL */
3704 * default period for cfs group bandwidth.
3705 * default: 0.1s, units: nanoseconds
3707 static inline u64 default_cfs_period(void)
3709 return 100000000ULL;
3712 static inline u64 sched_cfs_bandwidth_slice(void)
3714 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3718 * Replenish runtime according to assigned quota and update expiration time.
3719 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3720 * additional synchronization around rq->lock.
3722 * requires cfs_b->lock
3724 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3728 if (cfs_b->quota == RUNTIME_INF)
3731 now = sched_clock_cpu(smp_processor_id());
3732 cfs_b->runtime = cfs_b->quota;
3733 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3736 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3738 return &tg->cfs_bandwidth;
3741 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3742 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3744 if (unlikely(cfs_rq->throttle_count))
3745 return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
3747 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3750 /* returns 0 on failure to allocate runtime */
3751 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3753 struct task_group *tg = cfs_rq->tg;
3754 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3755 u64 amount = 0, min_amount, expires;
3757 /* note: this is a positive sum as runtime_remaining <= 0 */
3758 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3760 raw_spin_lock(&cfs_b->lock);
3761 if (cfs_b->quota == RUNTIME_INF)
3762 amount = min_amount;
3764 start_cfs_bandwidth(cfs_b);
3766 if (cfs_b->runtime > 0) {
3767 amount = min(cfs_b->runtime, min_amount);
3768 cfs_b->runtime -= amount;
3772 expires = cfs_b->runtime_expires;
3773 raw_spin_unlock(&cfs_b->lock);
3775 cfs_rq->runtime_remaining += amount;
3777 * we may have advanced our local expiration to account for allowed
3778 * spread between our sched_clock and the one on which runtime was
3781 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3782 cfs_rq->runtime_expires = expires;
3784 return cfs_rq->runtime_remaining > 0;
3788 * Note: This depends on the synchronization provided by sched_clock and the
3789 * fact that rq->clock snapshots this value.
3791 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3793 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3795 /* if the deadline is ahead of our clock, nothing to do */
3796 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3799 if (cfs_rq->runtime_remaining < 0)
3803 * If the local deadline has passed we have to consider the
3804 * possibility that our sched_clock is 'fast' and the global deadline
3805 * has not truly expired.
3807 * Fortunately we can check determine whether this the case by checking
3808 * whether the global deadline has advanced. It is valid to compare
3809 * cfs_b->runtime_expires without any locks since we only care about
3810 * exact equality, so a partial write will still work.
3813 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3814 /* extend local deadline, drift is bounded above by 2 ticks */
3815 cfs_rq->runtime_expires += TICK_NSEC;
3817 /* global deadline is ahead, expiration has passed */
3818 cfs_rq->runtime_remaining = 0;
3822 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3824 /* dock delta_exec before expiring quota (as it could span periods) */
3825 cfs_rq->runtime_remaining -= delta_exec;
3826 expire_cfs_rq_runtime(cfs_rq);
3828 if (likely(cfs_rq->runtime_remaining > 0))
3832 * if we're unable to extend our runtime we resched so that the active
3833 * hierarchy can be throttled
3835 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3836 resched_curr(rq_of(cfs_rq));
3839 static __always_inline
3840 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3842 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3845 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3848 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3850 return cfs_bandwidth_used() && cfs_rq->throttled;
3853 /* check whether cfs_rq, or any parent, is throttled */
3854 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3856 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3860 * Ensure that neither of the group entities corresponding to src_cpu or
3861 * dest_cpu are members of a throttled hierarchy when performing group
3862 * load-balance operations.
3864 static inline int throttled_lb_pair(struct task_group *tg,
3865 int src_cpu, int dest_cpu)
3867 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3869 src_cfs_rq = tg->cfs_rq[src_cpu];
3870 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3872 return throttled_hierarchy(src_cfs_rq) ||
3873 throttled_hierarchy(dest_cfs_rq);
3876 /* updated child weight may affect parent so we have to do this bottom up */
3877 static int tg_unthrottle_up(struct task_group *tg, void *data)
3879 struct rq *rq = data;
3880 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3882 cfs_rq->throttle_count--;
3883 if (!cfs_rq->throttle_count) {
3884 /* adjust cfs_rq_clock_task() */
3885 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3886 cfs_rq->throttled_clock_task;
3892 static int tg_throttle_down(struct task_group *tg, void *data)
3894 struct rq *rq = data;
3895 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3897 /* group is entering throttled state, stop time */
3898 if (!cfs_rq->throttle_count)
3899 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3900 cfs_rq->throttle_count++;
3905 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3907 struct rq *rq = rq_of(cfs_rq);
3908 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3909 struct sched_entity *se;
3910 long task_delta, dequeue = 1;
3913 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3915 /* freeze hierarchy runnable averages while throttled */
3917 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3920 task_delta = cfs_rq->h_nr_running;
3921 for_each_sched_entity(se) {
3922 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3923 /* throttled entity or throttle-on-deactivate */
3928 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3929 qcfs_rq->h_nr_running -= task_delta;
3931 if (qcfs_rq->load.weight)
3936 sub_nr_running(rq, task_delta);
3938 cfs_rq->throttled = 1;
3939 cfs_rq->throttled_clock = rq_clock(rq);
3940 raw_spin_lock(&cfs_b->lock);
3941 empty = list_empty(&cfs_b->throttled_cfs_rq);
3944 * Add to the _head_ of the list, so that an already-started
3945 * distribute_cfs_runtime will not see us
3947 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3950 * If we're the first throttled task, make sure the bandwidth
3954 start_cfs_bandwidth(cfs_b);
3956 raw_spin_unlock(&cfs_b->lock);
3959 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3961 struct rq *rq = rq_of(cfs_rq);
3962 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3963 struct sched_entity *se;
3967 se = cfs_rq->tg->se[cpu_of(rq)];
3969 cfs_rq->throttled = 0;
3971 update_rq_clock(rq);
3973 raw_spin_lock(&cfs_b->lock);
3974 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3975 list_del_rcu(&cfs_rq->throttled_list);
3976 raw_spin_unlock(&cfs_b->lock);
3978 /* update hierarchical throttle state */
3979 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3981 if (!cfs_rq->load.weight)
3984 task_delta = cfs_rq->h_nr_running;
3985 for_each_sched_entity(se) {
3989 cfs_rq = cfs_rq_of(se);
3991 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3992 cfs_rq->h_nr_running += task_delta;
3994 if (cfs_rq_throttled(cfs_rq))
3999 add_nr_running(rq, task_delta);
4001 /* determine whether we need to wake up potentially idle cpu */
4002 if (rq->curr == rq->idle && rq->cfs.nr_running)
4006 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
4007 u64 remaining, u64 expires)
4009 struct cfs_rq *cfs_rq;
4011 u64 starting_runtime = remaining;
4014 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
4016 struct rq *rq = rq_of(cfs_rq);
4018 raw_spin_lock(&rq->lock);
4019 if (!cfs_rq_throttled(cfs_rq))
4022 runtime = -cfs_rq->runtime_remaining + 1;
4023 if (runtime > remaining)
4024 runtime = remaining;
4025 remaining -= runtime;
4027 cfs_rq->runtime_remaining += runtime;
4028 cfs_rq->runtime_expires = expires;
4030 /* we check whether we're throttled above */
4031 if (cfs_rq->runtime_remaining > 0)
4032 unthrottle_cfs_rq(cfs_rq);
4035 raw_spin_unlock(&rq->lock);
4042 return starting_runtime - remaining;
4046 * Responsible for refilling a task_group's bandwidth and unthrottling its
4047 * cfs_rqs as appropriate. If there has been no activity within the last
4048 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4049 * used to track this state.
4051 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
4053 u64 runtime, runtime_expires;
4056 /* no need to continue the timer with no bandwidth constraint */
4057 if (cfs_b->quota == RUNTIME_INF)
4058 goto out_deactivate;
4060 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4061 cfs_b->nr_periods += overrun;
4064 * idle depends on !throttled (for the case of a large deficit), and if
4065 * we're going inactive then everything else can be deferred
4067 if (cfs_b->idle && !throttled)
4068 goto out_deactivate;
4070 __refill_cfs_bandwidth_runtime(cfs_b);
4073 /* mark as potentially idle for the upcoming period */
4078 /* account preceding periods in which throttling occurred */
4079 cfs_b->nr_throttled += overrun;
4081 runtime_expires = cfs_b->runtime_expires;
4084 * This check is repeated as we are holding onto the new bandwidth while
4085 * we unthrottle. This can potentially race with an unthrottled group
4086 * trying to acquire new bandwidth from the global pool. This can result
4087 * in us over-using our runtime if it is all used during this loop, but
4088 * only by limited amounts in that extreme case.
4090 while (throttled && cfs_b->runtime > 0) {
4091 runtime = cfs_b->runtime;
4092 raw_spin_unlock(&cfs_b->lock);
4093 /* we can't nest cfs_b->lock while distributing bandwidth */
4094 runtime = distribute_cfs_runtime(cfs_b, runtime,
4096 raw_spin_lock(&cfs_b->lock);
4098 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4100 cfs_b->runtime -= min(runtime, cfs_b->runtime);
4104 * While we are ensured activity in the period following an
4105 * unthrottle, this also covers the case in which the new bandwidth is
4106 * insufficient to cover the existing bandwidth deficit. (Forcing the
4107 * timer to remain active while there are any throttled entities.)
4117 /* a cfs_rq won't donate quota below this amount */
4118 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
4119 /* minimum remaining period time to redistribute slack quota */
4120 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
4121 /* how long we wait to gather additional slack before distributing */
4122 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
4125 * Are we near the end of the current quota period?
4127 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4128 * hrtimer base being cleared by hrtimer_start. In the case of
4129 * migrate_hrtimers, base is never cleared, so we are fine.
4131 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
4133 struct hrtimer *refresh_timer = &cfs_b->period_timer;
4136 /* if the call-back is running a quota refresh is already occurring */
4137 if (hrtimer_callback_running(refresh_timer))
4140 /* is a quota refresh about to occur? */
4141 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
4142 if (remaining < min_expire)
4148 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
4150 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
4152 /* if there's a quota refresh soon don't bother with slack */
4153 if (runtime_refresh_within(cfs_b, min_left))
4156 hrtimer_start(&cfs_b->slack_timer,
4157 ns_to_ktime(cfs_bandwidth_slack_period),
4161 /* we know any runtime found here is valid as update_curr() precedes return */
4162 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4164 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
4165 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
4167 if (slack_runtime <= 0)
4170 raw_spin_lock(&cfs_b->lock);
4171 if (cfs_b->quota != RUNTIME_INF &&
4172 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
4173 cfs_b->runtime += slack_runtime;
4175 /* we are under rq->lock, defer unthrottling using a timer */
4176 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
4177 !list_empty(&cfs_b->throttled_cfs_rq))
4178 start_cfs_slack_bandwidth(cfs_b);
4180 raw_spin_unlock(&cfs_b->lock);
4182 /* even if it's not valid for return we don't want to try again */
4183 cfs_rq->runtime_remaining -= slack_runtime;
4186 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4188 if (!cfs_bandwidth_used())
4191 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4194 __return_cfs_rq_runtime(cfs_rq);
4198 * This is done with a timer (instead of inline with bandwidth return) since
4199 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4201 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
4203 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
4206 /* confirm we're still not at a refresh boundary */
4207 raw_spin_lock(&cfs_b->lock);
4208 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
4209 raw_spin_unlock(&cfs_b->lock);
4213 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4214 runtime = cfs_b->runtime;
4216 expires = cfs_b->runtime_expires;
4217 raw_spin_unlock(&cfs_b->lock);
4222 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
4224 raw_spin_lock(&cfs_b->lock);
4225 if (expires == cfs_b->runtime_expires)
4226 cfs_b->runtime -= min(runtime, cfs_b->runtime);
4227 raw_spin_unlock(&cfs_b->lock);
4231 * When a group wakes up we want to make sure that its quota is not already
4232 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4233 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4235 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
4237 if (!cfs_bandwidth_used())
4240 /* an active group must be handled by the update_curr()->put() path */
4241 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
4244 /* ensure the group is not already throttled */
4245 if (cfs_rq_throttled(cfs_rq))
4248 /* update runtime allocation */
4249 account_cfs_rq_runtime(cfs_rq, 0);
4250 if (cfs_rq->runtime_remaining <= 0)
4251 throttle_cfs_rq(cfs_rq);
4254 static void sync_throttle(struct task_group *tg, int cpu)
4256 struct cfs_rq *pcfs_rq, *cfs_rq;
4258 if (!cfs_bandwidth_used())
4264 cfs_rq = tg->cfs_rq[cpu];
4265 pcfs_rq = tg->parent->cfs_rq[cpu];
4267 cfs_rq->throttle_count = pcfs_rq->throttle_count;
4268 cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4271 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4272 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4274 if (!cfs_bandwidth_used())
4277 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4281 * it's possible for a throttled entity to be forced into a running
4282 * state (e.g. set_curr_task), in this case we're finished.
4284 if (cfs_rq_throttled(cfs_rq))
4287 throttle_cfs_rq(cfs_rq);
4291 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
4293 struct cfs_bandwidth *cfs_b =
4294 container_of(timer, struct cfs_bandwidth, slack_timer);
4296 do_sched_cfs_slack_timer(cfs_b);
4298 return HRTIMER_NORESTART;
4301 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
4303 struct cfs_bandwidth *cfs_b =
4304 container_of(timer, struct cfs_bandwidth, period_timer);
4308 raw_spin_lock(&cfs_b->lock);
4310 overrun = hrtimer_forward_now(timer, cfs_b->period);
4314 idle = do_sched_cfs_period_timer(cfs_b, overrun);
4317 cfs_b->period_active = 0;
4318 raw_spin_unlock(&cfs_b->lock);
4320 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
4323 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4325 raw_spin_lock_init(&cfs_b->lock);
4327 cfs_b->quota = RUNTIME_INF;
4328 cfs_b->period = ns_to_ktime(default_cfs_period());
4330 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4331 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4332 cfs_b->period_timer.function = sched_cfs_period_timer;
4333 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4334 cfs_b->slack_timer.function = sched_cfs_slack_timer;
4337 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4339 cfs_rq->runtime_enabled = 0;
4340 INIT_LIST_HEAD(&cfs_rq->throttled_list);
4343 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4345 lockdep_assert_held(&cfs_b->lock);
4347 if (!cfs_b->period_active) {
4348 cfs_b->period_active = 1;
4349 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4350 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4354 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4356 /* init_cfs_bandwidth() was not called */
4357 if (!cfs_b->throttled_cfs_rq.next)
4360 hrtimer_cancel(&cfs_b->period_timer);
4361 hrtimer_cancel(&cfs_b->slack_timer);
4364 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4366 struct cfs_rq *cfs_rq;
4368 for_each_leaf_cfs_rq(rq, cfs_rq) {
4369 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4371 raw_spin_lock(&cfs_b->lock);
4372 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4373 raw_spin_unlock(&cfs_b->lock);
4377 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4379 struct cfs_rq *cfs_rq;
4381 for_each_leaf_cfs_rq(rq, cfs_rq) {
4382 if (!cfs_rq->runtime_enabled)
4386 * clock_task is not advancing so we just need to make sure
4387 * there's some valid quota amount
4389 cfs_rq->runtime_remaining = 1;
4391 * Offline rq is schedulable till cpu is completely disabled
4392 * in take_cpu_down(), so we prevent new cfs throttling here.
4394 cfs_rq->runtime_enabled = 0;
4396 if (cfs_rq_throttled(cfs_rq))
4397 unthrottle_cfs_rq(cfs_rq);
4401 #else /* CONFIG_CFS_BANDWIDTH */
4402 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4404 return rq_clock_task(rq_of(cfs_rq));
4407 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4408 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4409 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4410 static inline void sync_throttle(struct task_group *tg, int cpu) {}
4411 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4413 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4418 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4423 static inline int throttled_lb_pair(struct task_group *tg,
4424 int src_cpu, int dest_cpu)
4429 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4431 #ifdef CONFIG_FAIR_GROUP_SCHED
4432 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4435 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4439 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4440 static inline void update_runtime_enabled(struct rq *rq) {}
4441 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4443 #endif /* CONFIG_CFS_BANDWIDTH */
4445 /**************************************************
4446 * CFS operations on tasks:
4449 #ifdef CONFIG_SCHED_HRTICK
4450 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4452 struct sched_entity *se = &p->se;
4453 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4455 WARN_ON(task_rq(p) != rq);
4457 if (cfs_rq->nr_running > 1) {
4458 u64 slice = sched_slice(cfs_rq, se);
4459 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4460 s64 delta = slice - ran;
4467 hrtick_start(rq, delta);
4472 * called from enqueue/dequeue and updates the hrtick when the
4473 * current task is from our class and nr_running is low enough
4476 static void hrtick_update(struct rq *rq)
4478 struct task_struct *curr = rq->curr;
4480 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4483 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4484 hrtick_start_fair(rq, curr);
4486 #else /* !CONFIG_SCHED_HRTICK */
4488 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4492 static inline void hrtick_update(struct rq *rq)
4498 * The enqueue_task method is called before nr_running is
4499 * increased. Here we update the fair scheduling stats and
4500 * then put the task into the rbtree:
4503 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4505 struct cfs_rq *cfs_rq;
4506 struct sched_entity *se = &p->se;
4508 for_each_sched_entity(se) {
4511 cfs_rq = cfs_rq_of(se);
4512 enqueue_entity(cfs_rq, se, flags);
4515 * end evaluation on encountering a throttled cfs_rq
4517 * note: in the case of encountering a throttled cfs_rq we will
4518 * post the final h_nr_running increment below.
4520 if (cfs_rq_throttled(cfs_rq))
4522 cfs_rq->h_nr_running++;
4524 flags = ENQUEUE_WAKEUP;
4527 for_each_sched_entity(se) {
4528 cfs_rq = cfs_rq_of(se);
4529 cfs_rq->h_nr_running++;
4531 if (cfs_rq_throttled(cfs_rq))
4534 update_load_avg(se, 1);
4535 update_cfs_shares(cfs_rq);
4539 add_nr_running(rq, 1);
4544 static void set_next_buddy(struct sched_entity *se);
4547 * The dequeue_task method is called before nr_running is
4548 * decreased. We remove the task from the rbtree and
4549 * update the fair scheduling stats:
4551 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4553 struct cfs_rq *cfs_rq;
4554 struct sched_entity *se = &p->se;
4555 int task_sleep = flags & DEQUEUE_SLEEP;
4557 for_each_sched_entity(se) {
4558 cfs_rq = cfs_rq_of(se);
4559 dequeue_entity(cfs_rq, se, flags);
4562 * end evaluation on encountering a throttled cfs_rq
4564 * note: in the case of encountering a throttled cfs_rq we will
4565 * post the final h_nr_running decrement below.
4567 if (cfs_rq_throttled(cfs_rq))
4569 cfs_rq->h_nr_running--;
4571 /* Don't dequeue parent if it has other entities besides us */
4572 if (cfs_rq->load.weight) {
4573 /* Avoid re-evaluating load for this entity: */
4574 se = parent_entity(se);
4576 * Bias pick_next to pick a task from this cfs_rq, as
4577 * p is sleeping when it is within its sched_slice.
4579 if (task_sleep && se && !throttled_hierarchy(cfs_rq))
4583 flags |= DEQUEUE_SLEEP;
4586 for_each_sched_entity(se) {
4587 cfs_rq = cfs_rq_of(se);
4588 cfs_rq->h_nr_running--;
4590 if (cfs_rq_throttled(cfs_rq))
4593 update_load_avg(se, 1);
4594 update_cfs_shares(cfs_rq);
4598 sub_nr_running(rq, 1);
4604 #ifdef CONFIG_NO_HZ_COMMON
4606 * per rq 'load' arrray crap; XXX kill this.
4610 * The exact cpuload calculated at every tick would be:
4612 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4614 * If a cpu misses updates for n ticks (as it was idle) and update gets
4615 * called on the n+1-th tick when cpu may be busy, then we have:
4617 * load_n = (1 - 1/2^i)^n * load_0
4618 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4620 * decay_load_missed() below does efficient calculation of
4622 * load' = (1 - 1/2^i)^n * load
4624 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4625 * This allows us to precompute the above in said factors, thereby allowing the
4626 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4627 * fixed_power_int())
4629 * The calculation is approximated on a 128 point scale.
4631 #define DEGRADE_SHIFT 7
4633 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4634 static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4635 { 0, 0, 0, 0, 0, 0, 0, 0 },
4636 { 64, 32, 8, 0, 0, 0, 0, 0 },
4637 { 96, 72, 40, 12, 1, 0, 0, 0 },
4638 { 112, 98, 75, 43, 15, 1, 0, 0 },
4639 { 120, 112, 98, 76, 45, 16, 2, 0 }
4643 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4644 * would be when CPU is idle and so we just decay the old load without
4645 * adding any new load.
4647 static unsigned long
4648 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4652 if (!missed_updates)
4655 if (missed_updates >= degrade_zero_ticks[idx])
4659 return load >> missed_updates;
4661 while (missed_updates) {
4662 if (missed_updates % 2)
4663 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4665 missed_updates >>= 1;
4670 #endif /* CONFIG_NO_HZ_COMMON */
4673 * __cpu_load_update - update the rq->cpu_load[] statistics
4674 * @this_rq: The rq to update statistics for
4675 * @this_load: The current load
4676 * @pending_updates: The number of missed updates
4678 * Update rq->cpu_load[] statistics. This function is usually called every
4679 * scheduler tick (TICK_NSEC).
4681 * This function computes a decaying average:
4683 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4685 * Because of NOHZ it might not get called on every tick which gives need for
4686 * the @pending_updates argument.
4688 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4689 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4690 * = A * (A * load[i]_n-2 + B) + B
4691 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4692 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4693 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4694 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4695 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4697 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4698 * any change in load would have resulted in the tick being turned back on.
4700 * For regular NOHZ, this reduces to:
4702 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4704 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4707 static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
4708 unsigned long pending_updates)
4710 unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
4713 this_rq->nr_load_updates++;
4715 /* Update our load: */
4716 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4717 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4718 unsigned long old_load, new_load;
4720 /* scale is effectively 1 << i now, and >> i divides by scale */
4722 old_load = this_rq->cpu_load[i];
4723 #ifdef CONFIG_NO_HZ_COMMON
4724 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4725 if (tickless_load) {
4726 old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
4728 * old_load can never be a negative value because a
4729 * decayed tickless_load cannot be greater than the
4730 * original tickless_load.
4732 old_load += tickless_load;
4735 new_load = this_load;
4737 * Round up the averaging division if load is increasing. This
4738 * prevents us from getting stuck on 9 if the load is 10, for
4741 if (new_load > old_load)
4742 new_load += scale - 1;
4744 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4747 sched_avg_update(this_rq);
4750 /* Used instead of source_load when we know the type == 0 */
4751 static unsigned long weighted_cpuload(const int cpu)
4753 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4756 #ifdef CONFIG_NO_HZ_COMMON
4758 * There is no sane way to deal with nohz on smp when using jiffies because the
4759 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4760 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4762 * Therefore we need to avoid the delta approach from the regular tick when
4763 * possible since that would seriously skew the load calculation. This is why we
4764 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4765 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
4766 * loop exit, nohz_idle_balance, nohz full exit...)
4768 * This means we might still be one tick off for nohz periods.
4771 static void cpu_load_update_nohz(struct rq *this_rq,
4772 unsigned long curr_jiffies,
4775 unsigned long pending_updates;
4777 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4778 if (pending_updates) {
4779 this_rq->last_load_update_tick = curr_jiffies;
4781 * In the regular NOHZ case, we were idle, this means load 0.
4782 * In the NOHZ_FULL case, we were non-idle, we should consider
4783 * its weighted load.
4785 cpu_load_update(this_rq, load, pending_updates);
4790 * Called from nohz_idle_balance() to update the load ratings before doing the
4793 static void cpu_load_update_idle(struct rq *this_rq)
4796 * bail if there's load or we're actually up-to-date.
4798 if (weighted_cpuload(cpu_of(this_rq)))
4801 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
4805 * Record CPU load on nohz entry so we know the tickless load to account
4806 * on nohz exit. cpu_load[0] happens then to be updated more frequently
4807 * than other cpu_load[idx] but it should be fine as cpu_load readers
4808 * shouldn't rely into synchronized cpu_load[*] updates.
4810 void cpu_load_update_nohz_start(void)
4812 struct rq *this_rq = this_rq();
4815 * This is all lockless but should be fine. If weighted_cpuload changes
4816 * concurrently we'll exit nohz. And cpu_load write can race with
4817 * cpu_load_update_idle() but both updater would be writing the same.
4819 this_rq->cpu_load[0] = weighted_cpuload(cpu_of(this_rq));
4823 * Account the tickless load in the end of a nohz frame.
4825 void cpu_load_update_nohz_stop(void)
4827 unsigned long curr_jiffies = READ_ONCE(jiffies);
4828 struct rq *this_rq = this_rq();
4831 if (curr_jiffies == this_rq->last_load_update_tick)
4834 load = weighted_cpuload(cpu_of(this_rq));
4835 raw_spin_lock(&this_rq->lock);
4836 update_rq_clock(this_rq);
4837 cpu_load_update_nohz(this_rq, curr_jiffies, load);
4838 raw_spin_unlock(&this_rq->lock);
4840 #else /* !CONFIG_NO_HZ_COMMON */
4841 static inline void cpu_load_update_nohz(struct rq *this_rq,
4842 unsigned long curr_jiffies,
4843 unsigned long load) { }
4844 #endif /* CONFIG_NO_HZ_COMMON */
4846 static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
4848 #ifdef CONFIG_NO_HZ_COMMON
4849 /* See the mess around cpu_load_update_nohz(). */
4850 this_rq->last_load_update_tick = READ_ONCE(jiffies);
4852 cpu_load_update(this_rq, load, 1);
4856 * Called from scheduler_tick()
4858 void cpu_load_update_active(struct rq *this_rq)
4860 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4862 if (tick_nohz_tick_stopped())
4863 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
4865 cpu_load_update_periodic(this_rq, load);
4869 * Return a low guess at the load of a migration-source cpu weighted
4870 * according to the scheduling class and "nice" value.
4872 * We want to under-estimate the load of migration sources, to
4873 * balance conservatively.
4875 static unsigned long source_load(int cpu, int type)
4877 struct rq *rq = cpu_rq(cpu);
4878 unsigned long total = weighted_cpuload(cpu);
4880 if (type == 0 || !sched_feat(LB_BIAS))
4883 return min(rq->cpu_load[type-1], total);
4887 * Return a high guess at the load of a migration-target cpu weighted
4888 * according to the scheduling class and "nice" value.
4890 static unsigned long target_load(int cpu, int type)
4892 struct rq *rq = cpu_rq(cpu);
4893 unsigned long total = weighted_cpuload(cpu);
4895 if (type == 0 || !sched_feat(LB_BIAS))
4898 return max(rq->cpu_load[type-1], total);
4901 static unsigned long capacity_of(int cpu)
4903 return cpu_rq(cpu)->cpu_capacity;
4906 static unsigned long capacity_orig_of(int cpu)
4908 return cpu_rq(cpu)->cpu_capacity_orig;
4911 static unsigned long cpu_avg_load_per_task(int cpu)
4913 struct rq *rq = cpu_rq(cpu);
4914 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4915 unsigned long load_avg = weighted_cpuload(cpu);
4918 return load_avg / nr_running;
4923 #ifdef CONFIG_FAIR_GROUP_SCHED
4925 * effective_load() calculates the load change as seen from the root_task_group
4927 * Adding load to a group doesn't make a group heavier, but can cause movement
4928 * of group shares between cpus. Assuming the shares were perfectly aligned one
4929 * can calculate the shift in shares.
4931 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4932 * on this @cpu and results in a total addition (subtraction) of @wg to the
4933 * total group weight.
4935 * Given a runqueue weight distribution (rw_i) we can compute a shares
4936 * distribution (s_i) using:
4938 * s_i = rw_i / \Sum rw_j (1)
4940 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4941 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4942 * shares distribution (s_i):
4944 * rw_i = { 2, 4, 1, 0 }
4945 * s_i = { 2/7, 4/7, 1/7, 0 }
4947 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4948 * task used to run on and the CPU the waker is running on), we need to
4949 * compute the effect of waking a task on either CPU and, in case of a sync
4950 * wakeup, compute the effect of the current task going to sleep.
4952 * So for a change of @wl to the local @cpu with an overall group weight change
4953 * of @wl we can compute the new shares distribution (s'_i) using:
4955 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4957 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4958 * differences in waking a task to CPU 0. The additional task changes the
4959 * weight and shares distributions like:
4961 * rw'_i = { 3, 4, 1, 0 }
4962 * s'_i = { 3/8, 4/8, 1/8, 0 }
4964 * We can then compute the difference in effective weight by using:
4966 * dw_i = S * (s'_i - s_i) (3)
4968 * Where 'S' is the group weight as seen by its parent.
4970 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4971 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4972 * 4/7) times the weight of the group.
4974 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4976 struct sched_entity *se = tg->se[cpu];
4978 if (!tg->parent) /* the trivial, non-cgroup case */
4981 for_each_sched_entity(se) {
4982 struct cfs_rq *cfs_rq = se->my_q;
4983 long W, w = cfs_rq_load_avg(cfs_rq);
4988 * W = @wg + \Sum rw_j
4990 W = wg + atomic_long_read(&tg->load_avg);
4992 /* Ensure \Sum rw_j >= rw_i */
4993 W -= cfs_rq->tg_load_avg_contrib;
5002 * wl = S * s'_i; see (2)
5005 wl = (w * (long)tg->shares) / W;
5010 * Per the above, wl is the new se->load.weight value; since
5011 * those are clipped to [MIN_SHARES, ...) do so now. See
5012 * calc_cfs_shares().
5014 if (wl < MIN_SHARES)
5018 * wl = dw_i = S * (s'_i - s_i); see (3)
5020 wl -= se->avg.load_avg;
5023 * Recursively apply this logic to all parent groups to compute
5024 * the final effective load change on the root group. Since
5025 * only the @tg group gets extra weight, all parent groups can
5026 * only redistribute existing shares. @wl is the shift in shares
5027 * resulting from this level per the above.
5036 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
5043 static void record_wakee(struct task_struct *p)
5046 * Only decay a single time; tasks that have less then 1 wakeup per
5047 * jiffy will not have built up many flips.
5049 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
5050 current->wakee_flips >>= 1;
5051 current->wakee_flip_decay_ts = jiffies;
5054 if (current->last_wakee != p) {
5055 current->last_wakee = p;
5056 current->wakee_flips++;
5061 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5063 * A waker of many should wake a different task than the one last awakened
5064 * at a frequency roughly N times higher than one of its wakees.
5066 * In order to determine whether we should let the load spread vs consolidating
5067 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5068 * partner, and a factor of lls_size higher frequency in the other.
5070 * With both conditions met, we can be relatively sure that the relationship is
5071 * non-monogamous, with partner count exceeding socket size.
5073 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5074 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5077 static int wake_wide(struct task_struct *p)
5079 unsigned int master = current->wakee_flips;
5080 unsigned int slave = p->wakee_flips;
5081 int factor = this_cpu_read(sd_llc_size);
5084 swap(master, slave);
5085 if (slave < factor || master < slave * factor)
5090 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5092 s64 this_load, load;
5093 s64 this_eff_load, prev_eff_load;
5094 int idx, this_cpu, prev_cpu;
5095 struct task_group *tg;
5096 unsigned long weight;
5100 this_cpu = smp_processor_id();
5101 prev_cpu = task_cpu(p);
5102 load = source_load(prev_cpu, idx);
5103 this_load = target_load(this_cpu, idx);
5106 * If sync wakeup then subtract the (maximum possible)
5107 * effect of the currently running task from the load
5108 * of the current CPU:
5111 tg = task_group(current);
5112 weight = current->se.avg.load_avg;
5114 this_load += effective_load(tg, this_cpu, -weight, -weight);
5115 load += effective_load(tg, prev_cpu, 0, -weight);
5119 weight = p->se.avg.load_avg;
5122 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5123 * due to the sync cause above having dropped this_load to 0, we'll
5124 * always have an imbalance, but there's really nothing you can do
5125 * about that, so that's good too.
5127 * Otherwise check if either cpus are near enough in load to allow this
5128 * task to be woken on this_cpu.
5130 this_eff_load = 100;
5131 this_eff_load *= capacity_of(prev_cpu);
5133 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5134 prev_eff_load *= capacity_of(this_cpu);
5136 if (this_load > 0) {
5137 this_eff_load *= this_load +
5138 effective_load(tg, this_cpu, weight, weight);
5140 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5143 balanced = this_eff_load <= prev_eff_load;
5145 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5150 schedstat_inc(sd, ttwu_move_affine);
5151 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5157 * find_idlest_group finds and returns the least busy CPU group within the
5160 static struct sched_group *
5161 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5162 int this_cpu, int sd_flag)
5164 struct sched_group *idlest = NULL, *group = sd->groups;
5165 unsigned long min_load = ULONG_MAX, this_load = 0;
5166 int load_idx = sd->forkexec_idx;
5167 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5169 if (sd_flag & SD_BALANCE_WAKE)
5170 load_idx = sd->wake_idx;
5173 unsigned long load, avg_load;
5177 /* Skip over this group if it has no CPUs allowed */
5178 if (!cpumask_intersects(sched_group_cpus(group),
5179 tsk_cpus_allowed(p)))
5182 local_group = cpumask_test_cpu(this_cpu,
5183 sched_group_cpus(group));
5185 /* Tally up the load of all CPUs in the group */
5188 for_each_cpu(i, sched_group_cpus(group)) {
5189 /* Bias balancing toward cpus of our domain */
5191 load = source_load(i, load_idx);
5193 load = target_load(i, load_idx);
5198 /* Adjust by relative CPU capacity of the group */
5199 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5202 this_load = avg_load;
5203 } else if (avg_load < min_load) {
5204 min_load = avg_load;
5207 } while (group = group->next, group != sd->groups);
5209 if (!idlest || 100*this_load < imbalance*min_load)
5215 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5218 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5220 unsigned long load, min_load = ULONG_MAX;
5221 unsigned int min_exit_latency = UINT_MAX;
5222 u64 latest_idle_timestamp = 0;
5223 int least_loaded_cpu = this_cpu;
5224 int shallowest_idle_cpu = -1;
5227 /* Traverse only the allowed CPUs */
5228 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5230 struct rq *rq = cpu_rq(i);
5231 struct cpuidle_state *idle = idle_get_state(rq);
5232 if (idle && idle->exit_latency < min_exit_latency) {
5234 * We give priority to a CPU whose idle state
5235 * has the smallest exit latency irrespective
5236 * of any idle timestamp.
5238 min_exit_latency = idle->exit_latency;
5239 latest_idle_timestamp = rq->idle_stamp;
5240 shallowest_idle_cpu = i;
5241 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
5242 rq->idle_stamp > latest_idle_timestamp) {
5244 * If equal or no active idle state, then
5245 * the most recently idled CPU might have
5248 latest_idle_timestamp = rq->idle_stamp;
5249 shallowest_idle_cpu = i;
5251 } else if (shallowest_idle_cpu == -1) {
5252 load = weighted_cpuload(i);
5253 if (load < min_load || (load == min_load && i == this_cpu)) {
5255 least_loaded_cpu = i;
5260 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5264 * Try and locate an idle CPU in the sched_domain.
5266 static int select_idle_sibling(struct task_struct *p, int target)
5268 struct sched_domain *sd;
5269 struct sched_group *sg;
5270 int i = task_cpu(p);
5272 if (idle_cpu(target))
5276 * If the prevous cpu is cache affine and idle, don't be stupid.
5278 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5282 * Otherwise, iterate the domains and find an eligible idle cpu.
5284 * A completely idle sched group at higher domains is more
5285 * desirable than an idle group at a lower level, because lower
5286 * domains have smaller groups and usually share hardware
5287 * resources which causes tasks to contend on them, e.g. x86
5288 * hyperthread siblings in the lowest domain (SMT) can contend
5289 * on the shared cpu pipeline.
5291 * However, while we prefer idle groups at higher domains
5292 * finding an idle cpu at the lowest domain is still better than
5293 * returning 'target', which we've already established, isn't
5296 sd = rcu_dereference(per_cpu(sd_llc, target));
5297 for_each_lower_domain(sd) {
5300 if (!cpumask_intersects(sched_group_cpus(sg),
5301 tsk_cpus_allowed(p)))
5304 /* Ensure the entire group is idle */
5305 for_each_cpu(i, sched_group_cpus(sg)) {
5306 if (i == target || !idle_cpu(i))
5311 * It doesn't matter which cpu we pick, the
5312 * whole group is idle.
5314 target = cpumask_first_and(sched_group_cpus(sg),
5315 tsk_cpus_allowed(p));
5319 } while (sg != sd->groups);
5326 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5327 * tasks. The unit of the return value must be the one of capacity so we can
5328 * compare the utilization with the capacity of the CPU that is available for
5329 * CFS task (ie cpu_capacity).
5331 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5332 * recent utilization of currently non-runnable tasks on a CPU. It represents
5333 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5334 * capacity_orig is the cpu_capacity available at the highest frequency
5335 * (arch_scale_freq_capacity()).
5336 * The utilization of a CPU converges towards a sum equal to or less than the
5337 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5338 * the running time on this CPU scaled by capacity_curr.
5340 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5341 * higher than capacity_orig because of unfortunate rounding in
5342 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5343 * the average stabilizes with the new running time. We need to check that the
5344 * utilization stays within the range of [0..capacity_orig] and cap it if
5345 * necessary. Without utilization capping, a group could be seen as overloaded
5346 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5347 * available capacity. We allow utilization to overshoot capacity_curr (but not
5348 * capacity_orig) as it useful for predicting the capacity required after task
5349 * migrations (scheduler-driven DVFS).
5351 static int cpu_util(int cpu)
5353 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5354 unsigned long capacity = capacity_orig_of(cpu);
5356 return (util >= capacity) ? capacity : util;
5360 * select_task_rq_fair: Select target runqueue for the waking task in domains
5361 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5362 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5364 * Balances load by selecting the idlest cpu in the idlest group, or under
5365 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5367 * Returns the target cpu number.
5369 * preempt must be disabled.
5372 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5374 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5375 int cpu = smp_processor_id();
5376 int new_cpu = prev_cpu;
5377 int want_affine = 0;
5378 int sync = wake_flags & WF_SYNC;
5380 if (sd_flag & SD_BALANCE_WAKE) {
5382 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5386 for_each_domain(cpu, tmp) {
5387 if (!(tmp->flags & SD_LOAD_BALANCE))
5391 * If both cpu and prev_cpu are part of this domain,
5392 * cpu is a valid SD_WAKE_AFFINE target.
5394 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5395 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5400 if (tmp->flags & sd_flag)
5402 else if (!want_affine)
5407 sd = NULL; /* Prefer wake_affine over balance flags */
5408 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5413 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5414 new_cpu = select_idle_sibling(p, new_cpu);
5417 struct sched_group *group;
5420 if (!(sd->flags & sd_flag)) {
5425 group = find_idlest_group(sd, p, cpu, sd_flag);
5431 new_cpu = find_idlest_cpu(group, p, cpu);
5432 if (new_cpu == -1 || new_cpu == cpu) {
5433 /* Now try balancing at a lower domain level of cpu */
5438 /* Now try balancing at a lower domain level of new_cpu */
5440 weight = sd->span_weight;
5442 for_each_domain(cpu, tmp) {
5443 if (weight <= tmp->span_weight)
5445 if (tmp->flags & sd_flag)
5448 /* while loop will break here if sd == NULL */
5456 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5457 * cfs_rq_of(p) references at time of call are still valid and identify the
5458 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5460 static void migrate_task_rq_fair(struct task_struct *p)
5463 * As blocked tasks retain absolute vruntime the migration needs to
5464 * deal with this by subtracting the old and adding the new
5465 * min_vruntime -- the latter is done by enqueue_entity() when placing
5466 * the task on the new runqueue.
5468 if (p->state == TASK_WAKING) {
5469 struct sched_entity *se = &p->se;
5470 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5473 #ifndef CONFIG_64BIT
5474 u64 min_vruntime_copy;
5477 min_vruntime_copy = cfs_rq->min_vruntime_copy;
5479 min_vruntime = cfs_rq->min_vruntime;
5480 } while (min_vruntime != min_vruntime_copy);
5482 min_vruntime = cfs_rq->min_vruntime;
5485 se->vruntime -= min_vruntime;
5489 * We are supposed to update the task to "current" time, then its up to date
5490 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5491 * what current time is, so simply throw away the out-of-date time. This
5492 * will result in the wakee task is less decayed, but giving the wakee more
5493 * load sounds not bad.
5495 remove_entity_load_avg(&p->se);
5497 /* Tell new CPU we are migrated */
5498 p->se.avg.last_update_time = 0;
5500 /* We have migrated, no longer consider this task hot */
5501 p->se.exec_start = 0;
5504 static void task_dead_fair(struct task_struct *p)
5506 remove_entity_load_avg(&p->se);
5508 #endif /* CONFIG_SMP */
5510 static unsigned long
5511 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5513 unsigned long gran = sysctl_sched_wakeup_granularity;
5516 * Since its curr running now, convert the gran from real-time
5517 * to virtual-time in his units.
5519 * By using 'se' instead of 'curr' we penalize light tasks, so
5520 * they get preempted easier. That is, if 'se' < 'curr' then
5521 * the resulting gran will be larger, therefore penalizing the
5522 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5523 * be smaller, again penalizing the lighter task.
5525 * This is especially important for buddies when the leftmost
5526 * task is higher priority than the buddy.
5528 return calc_delta_fair(gran, se);
5532 * Should 'se' preempt 'curr'.
5546 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5548 s64 gran, vdiff = curr->vruntime - se->vruntime;
5553 gran = wakeup_gran(curr, se);
5560 static void set_last_buddy(struct sched_entity *se)
5562 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5565 for_each_sched_entity(se)
5566 cfs_rq_of(se)->last = se;
5569 static void set_next_buddy(struct sched_entity *se)
5571 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5574 for_each_sched_entity(se)
5575 cfs_rq_of(se)->next = se;
5578 static void set_skip_buddy(struct sched_entity *se)
5580 for_each_sched_entity(se)
5581 cfs_rq_of(se)->skip = se;
5585 * Preempt the current task with a newly woken task if needed:
5587 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5589 struct task_struct *curr = rq->curr;
5590 struct sched_entity *se = &curr->se, *pse = &p->se;
5591 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5592 int scale = cfs_rq->nr_running >= sched_nr_latency;
5593 int next_buddy_marked = 0;
5595 if (unlikely(se == pse))
5599 * This is possible from callers such as attach_tasks(), in which we
5600 * unconditionally check_prempt_curr() after an enqueue (which may have
5601 * lead to a throttle). This both saves work and prevents false
5602 * next-buddy nomination below.
5604 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5607 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5608 set_next_buddy(pse);
5609 next_buddy_marked = 1;
5613 * We can come here with TIF_NEED_RESCHED already set from new task
5616 * Note: this also catches the edge-case of curr being in a throttled
5617 * group (e.g. via set_curr_task), since update_curr() (in the
5618 * enqueue of curr) will have resulted in resched being set. This
5619 * prevents us from potentially nominating it as a false LAST_BUDDY
5622 if (test_tsk_need_resched(curr))
5625 /* Idle tasks are by definition preempted by non-idle tasks. */
5626 if (unlikely(curr->policy == SCHED_IDLE) &&
5627 likely(p->policy != SCHED_IDLE))
5631 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5632 * is driven by the tick):
5634 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5637 find_matching_se(&se, &pse);
5638 update_curr(cfs_rq_of(se));
5640 if (wakeup_preempt_entity(se, pse) == 1) {
5642 * Bias pick_next to pick the sched entity that is
5643 * triggering this preemption.
5645 if (!next_buddy_marked)
5646 set_next_buddy(pse);
5655 * Only set the backward buddy when the current task is still
5656 * on the rq. This can happen when a wakeup gets interleaved
5657 * with schedule on the ->pre_schedule() or idle_balance()
5658 * point, either of which can * drop the rq lock.
5660 * Also, during early boot the idle thread is in the fair class,
5661 * for obvious reasons its a bad idea to schedule back to it.
5663 if (unlikely(!se->on_rq || curr == rq->idle))
5666 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5670 static struct task_struct *
5671 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
5673 struct cfs_rq *cfs_rq = &rq->cfs;
5674 struct sched_entity *se;
5675 struct task_struct *p;
5679 #ifdef CONFIG_FAIR_GROUP_SCHED
5680 if (!cfs_rq->nr_running)
5683 if (prev->sched_class != &fair_sched_class)
5687 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5688 * likely that a next task is from the same cgroup as the current.
5690 * Therefore attempt to avoid putting and setting the entire cgroup
5691 * hierarchy, only change the part that actually changes.
5695 struct sched_entity *curr = cfs_rq->curr;
5698 * Since we got here without doing put_prev_entity() we also
5699 * have to consider cfs_rq->curr. If it is still a runnable
5700 * entity, update_curr() will update its vruntime, otherwise
5701 * forget we've ever seen it.
5705 update_curr(cfs_rq);
5710 * This call to check_cfs_rq_runtime() will do the
5711 * throttle and dequeue its entity in the parent(s).
5712 * Therefore the 'simple' nr_running test will indeed
5715 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5719 se = pick_next_entity(cfs_rq, curr);
5720 cfs_rq = group_cfs_rq(se);
5726 * Since we haven't yet done put_prev_entity and if the selected task
5727 * is a different task than we started out with, try and touch the
5728 * least amount of cfs_rqs.
5731 struct sched_entity *pse = &prev->se;
5733 while (!(cfs_rq = is_same_group(se, pse))) {
5734 int se_depth = se->depth;
5735 int pse_depth = pse->depth;
5737 if (se_depth <= pse_depth) {
5738 put_prev_entity(cfs_rq_of(pse), pse);
5739 pse = parent_entity(pse);
5741 if (se_depth >= pse_depth) {
5742 set_next_entity(cfs_rq_of(se), se);
5743 se = parent_entity(se);
5747 put_prev_entity(cfs_rq, pse);
5748 set_next_entity(cfs_rq, se);
5751 if (hrtick_enabled(rq))
5752 hrtick_start_fair(rq, p);
5759 if (!cfs_rq->nr_running)
5762 put_prev_task(rq, prev);
5765 se = pick_next_entity(cfs_rq, NULL);
5766 set_next_entity(cfs_rq, se);
5767 cfs_rq = group_cfs_rq(se);
5772 if (hrtick_enabled(rq))
5773 hrtick_start_fair(rq, p);
5779 * This is OK, because current is on_cpu, which avoids it being picked
5780 * for load-balance and preemption/IRQs are still disabled avoiding
5781 * further scheduler activity on it and we're being very careful to
5782 * re-start the picking loop.
5784 lockdep_unpin_lock(&rq->lock, cookie);
5785 new_tasks = idle_balance(rq);
5786 lockdep_repin_lock(&rq->lock, cookie);
5788 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5789 * possible for any higher priority task to appear. In that case we
5790 * must re-start the pick_next_entity() loop.
5802 * Account for a descheduled task:
5804 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5806 struct sched_entity *se = &prev->se;
5807 struct cfs_rq *cfs_rq;
5809 for_each_sched_entity(se) {
5810 cfs_rq = cfs_rq_of(se);
5811 put_prev_entity(cfs_rq, se);
5816 * sched_yield() is very simple
5818 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5820 static void yield_task_fair(struct rq *rq)
5822 struct task_struct *curr = rq->curr;
5823 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5824 struct sched_entity *se = &curr->se;
5827 * Are we the only task in the tree?
5829 if (unlikely(rq->nr_running == 1))
5832 clear_buddies(cfs_rq, se);
5834 if (curr->policy != SCHED_BATCH) {
5835 update_rq_clock(rq);
5837 * Update run-time statistics of the 'current'.
5839 update_curr(cfs_rq);
5841 * Tell update_rq_clock() that we've just updated,
5842 * so we don't do microscopic update in schedule()
5843 * and double the fastpath cost.
5845 rq_clock_skip_update(rq, true);
5851 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5853 struct sched_entity *se = &p->se;
5855 /* throttled hierarchies are not runnable */
5856 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5859 /* Tell the scheduler that we'd really like pse to run next. */
5862 yield_task_fair(rq);
5868 /**************************************************
5869 * Fair scheduling class load-balancing methods.
5873 * The purpose of load-balancing is to achieve the same basic fairness the
5874 * per-cpu scheduler provides, namely provide a proportional amount of compute
5875 * time to each task. This is expressed in the following equation:
5877 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5879 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5880 * W_i,0 is defined as:
5882 * W_i,0 = \Sum_j w_i,j (2)
5884 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5885 * is derived from the nice value as per sched_prio_to_weight[].
5887 * The weight average is an exponential decay average of the instantaneous
5890 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5892 * C_i is the compute capacity of cpu i, typically it is the
5893 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5894 * can also include other factors [XXX].
5896 * To achieve this balance we define a measure of imbalance which follows
5897 * directly from (1):
5899 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5901 * We them move tasks around to minimize the imbalance. In the continuous
5902 * function space it is obvious this converges, in the discrete case we get
5903 * a few fun cases generally called infeasible weight scenarios.
5906 * - infeasible weights;
5907 * - local vs global optima in the discrete case. ]
5912 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5913 * for all i,j solution, we create a tree of cpus that follows the hardware
5914 * topology where each level pairs two lower groups (or better). This results
5915 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5916 * tree to only the first of the previous level and we decrease the frequency
5917 * of load-balance at each level inv. proportional to the number of cpus in
5923 * \Sum { --- * --- * 2^i } = O(n) (5)
5925 * `- size of each group
5926 * | | `- number of cpus doing load-balance
5928 * `- sum over all levels
5930 * Coupled with a limit on how many tasks we can migrate every balance pass,
5931 * this makes (5) the runtime complexity of the balancer.
5933 * An important property here is that each CPU is still (indirectly) connected
5934 * to every other cpu in at most O(log n) steps:
5936 * The adjacency matrix of the resulting graph is given by:
5939 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5942 * And you'll find that:
5944 * A^(log_2 n)_i,j != 0 for all i,j (7)
5946 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5947 * The task movement gives a factor of O(m), giving a convergence complexity
5950 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5955 * In order to avoid CPUs going idle while there's still work to do, new idle
5956 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5957 * tree itself instead of relying on other CPUs to bring it work.
5959 * This adds some complexity to both (5) and (8) but it reduces the total idle
5967 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5970 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5975 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5977 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5979 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5982 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5983 * rewrite all of this once again.]
5986 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5988 enum fbq_type { regular, remote, all };
5990 #define LBF_ALL_PINNED 0x01
5991 #define LBF_NEED_BREAK 0x02
5992 #define LBF_DST_PINNED 0x04
5993 #define LBF_SOME_PINNED 0x08
5996 struct sched_domain *sd;
6004 struct cpumask *dst_grpmask;
6006 enum cpu_idle_type idle;
6008 /* The set of CPUs under consideration for load-balancing */
6009 struct cpumask *cpus;
6014 unsigned int loop_break;
6015 unsigned int loop_max;
6017 enum fbq_type fbq_type;
6018 struct list_head tasks;
6022 * Is this task likely cache-hot:
6024 static int task_hot(struct task_struct *p, struct lb_env *env)
6028 lockdep_assert_held(&env->src_rq->lock);
6030 if (p->sched_class != &fair_sched_class)
6033 if (unlikely(p->policy == SCHED_IDLE))
6037 * Buddy candidates are cache hot:
6039 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6040 (&p->se == cfs_rq_of(&p->se)->next ||
6041 &p->se == cfs_rq_of(&p->se)->last))
6044 if (sysctl_sched_migration_cost == -1)
6046 if (sysctl_sched_migration_cost == 0)
6049 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6051 return delta < (s64)sysctl_sched_migration_cost;
6054 #ifdef CONFIG_NUMA_BALANCING
6056 * Returns 1, if task migration degrades locality
6057 * Returns 0, if task migration improves locality i.e migration preferred.
6058 * Returns -1, if task migration is not affected by locality.
6060 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6062 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6063 unsigned long src_faults, dst_faults;
6064 int src_nid, dst_nid;
6066 if (!static_branch_likely(&sched_numa_balancing))
6069 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6072 src_nid = cpu_to_node(env->src_cpu);
6073 dst_nid = cpu_to_node(env->dst_cpu);
6075 if (src_nid == dst_nid)
6078 /* Migrating away from the preferred node is always bad. */
6079 if (src_nid == p->numa_preferred_nid) {
6080 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6086 /* Encourage migration to the preferred node. */
6087 if (dst_nid == p->numa_preferred_nid)
6091 src_faults = group_faults(p, src_nid);
6092 dst_faults = group_faults(p, dst_nid);
6094 src_faults = task_faults(p, src_nid);
6095 dst_faults = task_faults(p, dst_nid);
6098 return dst_faults < src_faults;
6102 static inline int migrate_degrades_locality(struct task_struct *p,
6110 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6113 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6117 lockdep_assert_held(&env->src_rq->lock);
6120 * We do not migrate tasks that are:
6121 * 1) throttled_lb_pair, or
6122 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6123 * 3) running (obviously), or
6124 * 4) are cache-hot on their current CPU.
6126 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6129 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6132 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6134 env->flags |= LBF_SOME_PINNED;
6137 * Remember if this task can be migrated to any other cpu in
6138 * our sched_group. We may want to revisit it if we couldn't
6139 * meet load balance goals by pulling other tasks on src_cpu.
6141 * Also avoid computing new_dst_cpu if we have already computed
6142 * one in current iteration.
6144 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6147 /* Prevent to re-select dst_cpu via env's cpus */
6148 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6149 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6150 env->flags |= LBF_DST_PINNED;
6151 env->new_dst_cpu = cpu;
6159 /* Record that we found atleast one task that could run on dst_cpu */
6160 env->flags &= ~LBF_ALL_PINNED;
6162 if (task_running(env->src_rq, p)) {
6163 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6168 * Aggressive migration if:
6169 * 1) destination numa is preferred
6170 * 2) task is cache cold, or
6171 * 3) too many balance attempts have failed.
6173 tsk_cache_hot = migrate_degrades_locality(p, env);
6174 if (tsk_cache_hot == -1)
6175 tsk_cache_hot = task_hot(p, env);
6177 if (tsk_cache_hot <= 0 ||
6178 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6179 if (tsk_cache_hot == 1) {
6180 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6181 schedstat_inc(p, se.statistics.nr_forced_migrations);
6186 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6191 * detach_task() -- detach the task for the migration specified in env
6193 static void detach_task(struct task_struct *p, struct lb_env *env)
6195 lockdep_assert_held(&env->src_rq->lock);
6197 p->on_rq = TASK_ON_RQ_MIGRATING;
6198 deactivate_task(env->src_rq, p, 0);
6199 set_task_cpu(p, env->dst_cpu);
6203 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6204 * part of active balancing operations within "domain".
6206 * Returns a task if successful and NULL otherwise.
6208 static struct task_struct *detach_one_task(struct lb_env *env)
6210 struct task_struct *p, *n;
6212 lockdep_assert_held(&env->src_rq->lock);
6214 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6215 if (!can_migrate_task(p, env))
6218 detach_task(p, env);
6221 * Right now, this is only the second place where
6222 * lb_gained[env->idle] is updated (other is detach_tasks)
6223 * so we can safely collect stats here rather than
6224 * inside detach_tasks().
6226 schedstat_inc(env->sd, lb_gained[env->idle]);
6232 static const unsigned int sched_nr_migrate_break = 32;
6235 * detach_tasks() -- tries to detach up to imbalance weighted load from
6236 * busiest_rq, as part of a balancing operation within domain "sd".
6238 * Returns number of detached tasks if successful and 0 otherwise.
6240 static int detach_tasks(struct lb_env *env)
6242 struct list_head *tasks = &env->src_rq->cfs_tasks;
6243 struct task_struct *p;
6247 lockdep_assert_held(&env->src_rq->lock);
6249 if (env->imbalance <= 0)
6252 while (!list_empty(tasks)) {
6254 * We don't want to steal all, otherwise we may be treated likewise,
6255 * which could at worst lead to a livelock crash.
6257 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6260 p = list_first_entry(tasks, struct task_struct, se.group_node);
6263 /* We've more or less seen every task there is, call it quits */
6264 if (env->loop > env->loop_max)
6267 /* take a breather every nr_migrate tasks */
6268 if (env->loop > env->loop_break) {
6269 env->loop_break += sched_nr_migrate_break;
6270 env->flags |= LBF_NEED_BREAK;
6274 if (!can_migrate_task(p, env))
6277 load = task_h_load(p);
6279 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6282 if ((load / 2) > env->imbalance)
6285 detach_task(p, env);
6286 list_add(&p->se.group_node, &env->tasks);
6289 env->imbalance -= load;
6291 #ifdef CONFIG_PREEMPT
6293 * NEWIDLE balancing is a source of latency, so preemptible
6294 * kernels will stop after the first task is detached to minimize
6295 * the critical section.
6297 if (env->idle == CPU_NEWLY_IDLE)
6302 * We only want to steal up to the prescribed amount of
6305 if (env->imbalance <= 0)
6310 list_move_tail(&p->se.group_node, tasks);
6314 * Right now, this is one of only two places we collect this stat
6315 * so we can safely collect detach_one_task() stats here rather
6316 * than inside detach_one_task().
6318 schedstat_add(env->sd, lb_gained[env->idle], detached);
6324 * attach_task() -- attach the task detached by detach_task() to its new rq.
6326 static void attach_task(struct rq *rq, struct task_struct *p)
6328 lockdep_assert_held(&rq->lock);
6330 BUG_ON(task_rq(p) != rq);
6331 activate_task(rq, p, 0);
6332 p->on_rq = TASK_ON_RQ_QUEUED;
6333 check_preempt_curr(rq, p, 0);
6337 * attach_one_task() -- attaches the task returned from detach_one_task() to
6340 static void attach_one_task(struct rq *rq, struct task_struct *p)
6342 raw_spin_lock(&rq->lock);
6344 raw_spin_unlock(&rq->lock);
6348 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6351 static void attach_tasks(struct lb_env *env)
6353 struct list_head *tasks = &env->tasks;
6354 struct task_struct *p;
6356 raw_spin_lock(&env->dst_rq->lock);
6358 while (!list_empty(tasks)) {
6359 p = list_first_entry(tasks, struct task_struct, se.group_node);
6360 list_del_init(&p->se.group_node);
6362 attach_task(env->dst_rq, p);
6365 raw_spin_unlock(&env->dst_rq->lock);
6368 #ifdef CONFIG_FAIR_GROUP_SCHED
6369 static void update_blocked_averages(int cpu)
6371 struct rq *rq = cpu_rq(cpu);
6372 struct cfs_rq *cfs_rq;
6373 unsigned long flags;
6375 raw_spin_lock_irqsave(&rq->lock, flags);
6376 update_rq_clock(rq);
6379 * Iterates the task_group tree in a bottom up fashion, see
6380 * list_add_leaf_cfs_rq() for details.
6382 for_each_leaf_cfs_rq(rq, cfs_rq) {
6383 /* throttled entities do not contribute to load */
6384 if (throttled_hierarchy(cfs_rq))
6387 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6388 update_tg_load_avg(cfs_rq, 0);
6390 raw_spin_unlock_irqrestore(&rq->lock, flags);
6394 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6395 * This needs to be done in a top-down fashion because the load of a child
6396 * group is a fraction of its parents load.
6398 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6400 struct rq *rq = rq_of(cfs_rq);
6401 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6402 unsigned long now = jiffies;
6405 if (cfs_rq->last_h_load_update == now)
6408 cfs_rq->h_load_next = NULL;
6409 for_each_sched_entity(se) {
6410 cfs_rq = cfs_rq_of(se);
6411 cfs_rq->h_load_next = se;
6412 if (cfs_rq->last_h_load_update == now)
6417 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6418 cfs_rq->last_h_load_update = now;
6421 while ((se = cfs_rq->h_load_next) != NULL) {
6422 load = cfs_rq->h_load;
6423 load = div64_ul(load * se->avg.load_avg,
6424 cfs_rq_load_avg(cfs_rq) + 1);
6425 cfs_rq = group_cfs_rq(se);
6426 cfs_rq->h_load = load;
6427 cfs_rq->last_h_load_update = now;
6431 static unsigned long task_h_load(struct task_struct *p)
6433 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6435 update_cfs_rq_h_load(cfs_rq);
6436 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6437 cfs_rq_load_avg(cfs_rq) + 1);
6440 static inline void update_blocked_averages(int cpu)
6442 struct rq *rq = cpu_rq(cpu);
6443 struct cfs_rq *cfs_rq = &rq->cfs;
6444 unsigned long flags;
6446 raw_spin_lock_irqsave(&rq->lock, flags);
6447 update_rq_clock(rq);
6448 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
6449 raw_spin_unlock_irqrestore(&rq->lock, flags);
6452 static unsigned long task_h_load(struct task_struct *p)
6454 return p->se.avg.load_avg;
6458 /********** Helpers for find_busiest_group ************************/
6467 * sg_lb_stats - stats of a sched_group required for load_balancing
6469 struct sg_lb_stats {
6470 unsigned long avg_load; /*Avg load across the CPUs of the group */
6471 unsigned long group_load; /* Total load over the CPUs of the group */
6472 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6473 unsigned long load_per_task;
6474 unsigned long group_capacity;
6475 unsigned long group_util; /* Total utilization of the group */
6476 unsigned int sum_nr_running; /* Nr tasks running in the group */
6477 unsigned int idle_cpus;
6478 unsigned int group_weight;
6479 enum group_type group_type;
6480 int group_no_capacity;
6481 #ifdef CONFIG_NUMA_BALANCING
6482 unsigned int nr_numa_running;
6483 unsigned int nr_preferred_running;
6488 * sd_lb_stats - Structure to store the statistics of a sched_domain
6489 * during load balancing.
6491 struct sd_lb_stats {
6492 struct sched_group *busiest; /* Busiest group in this sd */
6493 struct sched_group *local; /* Local group in this sd */
6494 unsigned long total_load; /* Total load of all groups in sd */
6495 unsigned long total_capacity; /* Total capacity of all groups in sd */
6496 unsigned long avg_load; /* Average load across all groups in sd */
6498 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6499 struct sg_lb_stats local_stat; /* Statistics of the local group */
6502 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6505 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6506 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6507 * We must however clear busiest_stat::avg_load because
6508 * update_sd_pick_busiest() reads this before assignment.
6510 *sds = (struct sd_lb_stats){
6514 .total_capacity = 0UL,
6517 .sum_nr_running = 0,
6518 .group_type = group_other,
6524 * get_sd_load_idx - Obtain the load index for a given sched domain.
6525 * @sd: The sched_domain whose load_idx is to be obtained.
6526 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6528 * Return: The load index.
6530 static inline int get_sd_load_idx(struct sched_domain *sd,
6531 enum cpu_idle_type idle)
6537 load_idx = sd->busy_idx;
6540 case CPU_NEWLY_IDLE:
6541 load_idx = sd->newidle_idx;
6544 load_idx = sd->idle_idx;
6551 static unsigned long scale_rt_capacity(int cpu)
6553 struct rq *rq = cpu_rq(cpu);
6554 u64 total, used, age_stamp, avg;
6558 * Since we're reading these variables without serialization make sure
6559 * we read them once before doing sanity checks on them.
6561 age_stamp = READ_ONCE(rq->age_stamp);
6562 avg = READ_ONCE(rq->rt_avg);
6563 delta = __rq_clock_broken(rq) - age_stamp;
6565 if (unlikely(delta < 0))
6568 total = sched_avg_period() + delta;
6570 used = div_u64(avg, total);
6572 if (likely(used < SCHED_CAPACITY_SCALE))
6573 return SCHED_CAPACITY_SCALE - used;
6578 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6580 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6581 struct sched_group *sdg = sd->groups;
6583 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6585 capacity *= scale_rt_capacity(cpu);
6586 capacity >>= SCHED_CAPACITY_SHIFT;
6591 cpu_rq(cpu)->cpu_capacity = capacity;
6592 sdg->sgc->capacity = capacity;
6595 void update_group_capacity(struct sched_domain *sd, int cpu)
6597 struct sched_domain *child = sd->child;
6598 struct sched_group *group, *sdg = sd->groups;
6599 unsigned long capacity;
6600 unsigned long interval;
6602 interval = msecs_to_jiffies(sd->balance_interval);
6603 interval = clamp(interval, 1UL, max_load_balance_interval);
6604 sdg->sgc->next_update = jiffies + interval;
6607 update_cpu_capacity(sd, cpu);
6613 if (child->flags & SD_OVERLAP) {
6615 * SD_OVERLAP domains cannot assume that child groups
6616 * span the current group.
6619 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6620 struct sched_group_capacity *sgc;
6621 struct rq *rq = cpu_rq(cpu);
6624 * build_sched_domains() -> init_sched_groups_capacity()
6625 * gets here before we've attached the domains to the
6628 * Use capacity_of(), which is set irrespective of domains
6629 * in update_cpu_capacity().
6631 * This avoids capacity from being 0 and
6632 * causing divide-by-zero issues on boot.
6634 if (unlikely(!rq->sd)) {
6635 capacity += capacity_of(cpu);
6639 sgc = rq->sd->groups->sgc;
6640 capacity += sgc->capacity;
6644 * !SD_OVERLAP domains can assume that child groups
6645 * span the current group.
6648 group = child->groups;
6650 capacity += group->sgc->capacity;
6651 group = group->next;
6652 } while (group != child->groups);
6655 sdg->sgc->capacity = capacity;
6659 * Check whether the capacity of the rq has been noticeably reduced by side
6660 * activity. The imbalance_pct is used for the threshold.
6661 * Return true is the capacity is reduced
6664 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6666 return ((rq->cpu_capacity * sd->imbalance_pct) <
6667 (rq->cpu_capacity_orig * 100));
6671 * Group imbalance indicates (and tries to solve) the problem where balancing
6672 * groups is inadequate due to tsk_cpus_allowed() constraints.
6674 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6675 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6678 * { 0 1 2 3 } { 4 5 6 7 }
6681 * If we were to balance group-wise we'd place two tasks in the first group and
6682 * two tasks in the second group. Clearly this is undesired as it will overload
6683 * cpu 3 and leave one of the cpus in the second group unused.
6685 * The current solution to this issue is detecting the skew in the first group
6686 * by noticing the lower domain failed to reach balance and had difficulty
6687 * moving tasks due to affinity constraints.
6689 * When this is so detected; this group becomes a candidate for busiest; see
6690 * update_sd_pick_busiest(). And calculate_imbalance() and
6691 * find_busiest_group() avoid some of the usual balance conditions to allow it
6692 * to create an effective group imbalance.
6694 * This is a somewhat tricky proposition since the next run might not find the
6695 * group imbalance and decide the groups need to be balanced again. A most
6696 * subtle and fragile situation.
6699 static inline int sg_imbalanced(struct sched_group *group)
6701 return group->sgc->imbalance;
6705 * group_has_capacity returns true if the group has spare capacity that could
6706 * be used by some tasks.
6707 * We consider that a group has spare capacity if the * number of task is
6708 * smaller than the number of CPUs or if the utilization is lower than the
6709 * available capacity for CFS tasks.
6710 * For the latter, we use a threshold to stabilize the state, to take into
6711 * account the variance of the tasks' load and to return true if the available
6712 * capacity in meaningful for the load balancer.
6713 * As an example, an available capacity of 1% can appear but it doesn't make
6714 * any benefit for the load balance.
6717 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6719 if (sgs->sum_nr_running < sgs->group_weight)
6722 if ((sgs->group_capacity * 100) >
6723 (sgs->group_util * env->sd->imbalance_pct))
6730 * group_is_overloaded returns true if the group has more tasks than it can
6732 * group_is_overloaded is not equals to !group_has_capacity because a group
6733 * with the exact right number of tasks, has no more spare capacity but is not
6734 * overloaded so both group_has_capacity and group_is_overloaded return
6738 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6740 if (sgs->sum_nr_running <= sgs->group_weight)
6743 if ((sgs->group_capacity * 100) <
6744 (sgs->group_util * env->sd->imbalance_pct))
6751 group_type group_classify(struct sched_group *group,
6752 struct sg_lb_stats *sgs)
6754 if (sgs->group_no_capacity)
6755 return group_overloaded;
6757 if (sg_imbalanced(group))
6758 return group_imbalanced;
6764 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6765 * @env: The load balancing environment.
6766 * @group: sched_group whose statistics are to be updated.
6767 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6768 * @local_group: Does group contain this_cpu.
6769 * @sgs: variable to hold the statistics for this group.
6770 * @overload: Indicate more than one runnable task for any CPU.
6772 static inline void update_sg_lb_stats(struct lb_env *env,
6773 struct sched_group *group, int load_idx,
6774 int local_group, struct sg_lb_stats *sgs,
6780 memset(sgs, 0, sizeof(*sgs));
6782 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6783 struct rq *rq = cpu_rq(i);
6785 /* Bias balancing toward cpus of our domain */
6787 load = target_load(i, load_idx);
6789 load = source_load(i, load_idx);
6791 sgs->group_load += load;
6792 sgs->group_util += cpu_util(i);
6793 sgs->sum_nr_running += rq->cfs.h_nr_running;
6795 nr_running = rq->nr_running;
6799 #ifdef CONFIG_NUMA_BALANCING
6800 sgs->nr_numa_running += rq->nr_numa_running;
6801 sgs->nr_preferred_running += rq->nr_preferred_running;
6803 sgs->sum_weighted_load += weighted_cpuload(i);
6805 * No need to call idle_cpu() if nr_running is not 0
6807 if (!nr_running && idle_cpu(i))
6811 /* Adjust by relative CPU capacity of the group */
6812 sgs->group_capacity = group->sgc->capacity;
6813 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6815 if (sgs->sum_nr_running)
6816 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6818 sgs->group_weight = group->group_weight;
6820 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6821 sgs->group_type = group_classify(group, sgs);
6825 * update_sd_pick_busiest - return 1 on busiest group
6826 * @env: The load balancing environment.
6827 * @sds: sched_domain statistics
6828 * @sg: sched_group candidate to be checked for being the busiest
6829 * @sgs: sched_group statistics
6831 * Determine if @sg is a busier group than the previously selected
6834 * Return: %true if @sg is a busier group than the previously selected
6835 * busiest group. %false otherwise.
6837 static bool update_sd_pick_busiest(struct lb_env *env,
6838 struct sd_lb_stats *sds,
6839 struct sched_group *sg,
6840 struct sg_lb_stats *sgs)
6842 struct sg_lb_stats *busiest = &sds->busiest_stat;
6844 if (sgs->group_type > busiest->group_type)
6847 if (sgs->group_type < busiest->group_type)
6850 if (sgs->avg_load <= busiest->avg_load)
6853 /* This is the busiest node in its class. */
6854 if (!(env->sd->flags & SD_ASYM_PACKING))
6857 /* No ASYM_PACKING if target cpu is already busy */
6858 if (env->idle == CPU_NOT_IDLE)
6861 * ASYM_PACKING needs to move all the work to the lowest
6862 * numbered CPUs in the group, therefore mark all groups
6863 * higher than ourself as busy.
6865 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6869 /* Prefer to move from highest possible cpu's work */
6870 if (group_first_cpu(sds->busiest) < group_first_cpu(sg))
6877 #ifdef CONFIG_NUMA_BALANCING
6878 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6880 if (sgs->sum_nr_running > sgs->nr_numa_running)
6882 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6887 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6889 if (rq->nr_running > rq->nr_numa_running)
6891 if (rq->nr_running > rq->nr_preferred_running)
6896 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6901 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6905 #endif /* CONFIG_NUMA_BALANCING */
6908 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6909 * @env: The load balancing environment.
6910 * @sds: variable to hold the statistics for this sched_domain.
6912 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6914 struct sched_domain *child = env->sd->child;
6915 struct sched_group *sg = env->sd->groups;
6916 struct sg_lb_stats tmp_sgs;
6917 int load_idx, prefer_sibling = 0;
6918 bool overload = false;
6920 if (child && child->flags & SD_PREFER_SIBLING)
6923 load_idx = get_sd_load_idx(env->sd, env->idle);
6926 struct sg_lb_stats *sgs = &tmp_sgs;
6929 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6932 sgs = &sds->local_stat;
6934 if (env->idle != CPU_NEWLY_IDLE ||
6935 time_after_eq(jiffies, sg->sgc->next_update))
6936 update_group_capacity(env->sd, env->dst_cpu);
6939 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6946 * In case the child domain prefers tasks go to siblings
6947 * first, lower the sg capacity so that we'll try
6948 * and move all the excess tasks away. We lower the capacity
6949 * of a group only if the local group has the capacity to fit
6950 * these excess tasks. The extra check prevents the case where
6951 * you always pull from the heaviest group when it is already
6952 * under-utilized (possible with a large weight task outweighs
6953 * the tasks on the system).
6955 if (prefer_sibling && sds->local &&
6956 group_has_capacity(env, &sds->local_stat) &&
6957 (sgs->sum_nr_running > 1)) {
6958 sgs->group_no_capacity = 1;
6959 sgs->group_type = group_classify(sg, sgs);
6962 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6964 sds->busiest_stat = *sgs;
6968 /* Now, start updating sd_lb_stats */
6969 sds->total_load += sgs->group_load;
6970 sds->total_capacity += sgs->group_capacity;
6973 } while (sg != env->sd->groups);
6975 if (env->sd->flags & SD_NUMA)
6976 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6978 if (!env->sd->parent) {
6979 /* update overload indicator if we are at root domain */
6980 if (env->dst_rq->rd->overload != overload)
6981 env->dst_rq->rd->overload = overload;
6987 * check_asym_packing - Check to see if the group is packed into the
6990 * This is primarily intended to used at the sibling level. Some
6991 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6992 * case of POWER7, it can move to lower SMT modes only when higher
6993 * threads are idle. When in lower SMT modes, the threads will
6994 * perform better since they share less core resources. Hence when we
6995 * have idle threads, we want them to be the higher ones.
6997 * This packing function is run on idle threads. It checks to see if
6998 * the busiest CPU in this domain (core in the P7 case) has a higher
6999 * CPU number than the packing function is being run on. Here we are
7000 * assuming lower CPU number will be equivalent to lower a SMT thread
7003 * Return: 1 when packing is required and a task should be moved to
7004 * this CPU. The amount of the imbalance is returned in *imbalance.
7006 * @env: The load balancing environment.
7007 * @sds: Statistics of the sched_domain which is to be packed
7009 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7013 if (!(env->sd->flags & SD_ASYM_PACKING))
7016 if (env->idle == CPU_NOT_IDLE)
7022 busiest_cpu = group_first_cpu(sds->busiest);
7023 if (env->dst_cpu > busiest_cpu)
7026 env->imbalance = DIV_ROUND_CLOSEST(
7027 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7028 SCHED_CAPACITY_SCALE);
7034 * fix_small_imbalance - Calculate the minor imbalance that exists
7035 * amongst the groups of a sched_domain, during
7037 * @env: The load balancing environment.
7038 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7041 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7043 unsigned long tmp, capa_now = 0, capa_move = 0;
7044 unsigned int imbn = 2;
7045 unsigned long scaled_busy_load_per_task;
7046 struct sg_lb_stats *local, *busiest;
7048 local = &sds->local_stat;
7049 busiest = &sds->busiest_stat;
7051 if (!local->sum_nr_running)
7052 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7053 else if (busiest->load_per_task > local->load_per_task)
7056 scaled_busy_load_per_task =
7057 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7058 busiest->group_capacity;
7060 if (busiest->avg_load + scaled_busy_load_per_task >=
7061 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7062 env->imbalance = busiest->load_per_task;
7067 * OK, we don't have enough imbalance to justify moving tasks,
7068 * however we may be able to increase total CPU capacity used by
7072 capa_now += busiest->group_capacity *
7073 min(busiest->load_per_task, busiest->avg_load);
7074 capa_now += local->group_capacity *
7075 min(local->load_per_task, local->avg_load);
7076 capa_now /= SCHED_CAPACITY_SCALE;
7078 /* Amount of load we'd subtract */
7079 if (busiest->avg_load > scaled_busy_load_per_task) {
7080 capa_move += busiest->group_capacity *
7081 min(busiest->load_per_task,
7082 busiest->avg_load - scaled_busy_load_per_task);
7085 /* Amount of load we'd add */
7086 if (busiest->avg_load * busiest->group_capacity <
7087 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7088 tmp = (busiest->avg_load * busiest->group_capacity) /
7089 local->group_capacity;
7091 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7092 local->group_capacity;
7094 capa_move += local->group_capacity *
7095 min(local->load_per_task, local->avg_load + tmp);
7096 capa_move /= SCHED_CAPACITY_SCALE;
7098 /* Move if we gain throughput */
7099 if (capa_move > capa_now)
7100 env->imbalance = busiest->load_per_task;
7104 * calculate_imbalance - Calculate the amount of imbalance present within the
7105 * groups of a given sched_domain during load balance.
7106 * @env: load balance environment
7107 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7109 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7111 unsigned long max_pull, load_above_capacity = ~0UL;
7112 struct sg_lb_stats *local, *busiest;
7114 local = &sds->local_stat;
7115 busiest = &sds->busiest_stat;
7117 if (busiest->group_type == group_imbalanced) {
7119 * In the group_imb case we cannot rely on group-wide averages
7120 * to ensure cpu-load equilibrium, look at wider averages. XXX
7122 busiest->load_per_task =
7123 min(busiest->load_per_task, sds->avg_load);
7127 * Avg load of busiest sg can be less and avg load of local sg can
7128 * be greater than avg load across all sgs of sd because avg load
7129 * factors in sg capacity and sgs with smaller group_type are
7130 * skipped when updating the busiest sg:
7132 if (busiest->avg_load <= sds->avg_load ||
7133 local->avg_load >= sds->avg_load) {
7135 return fix_small_imbalance(env, sds);
7139 * If there aren't any idle cpus, avoid creating some.
7141 if (busiest->group_type == group_overloaded &&
7142 local->group_type == group_overloaded) {
7143 load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7144 if (load_above_capacity > busiest->group_capacity) {
7145 load_above_capacity -= busiest->group_capacity;
7146 load_above_capacity *= NICE_0_LOAD;
7147 load_above_capacity /= busiest->group_capacity;
7149 load_above_capacity = ~0UL;
7153 * We're trying to get all the cpus to the average_load, so we don't
7154 * want to push ourselves above the average load, nor do we wish to
7155 * reduce the max loaded cpu below the average load. At the same time,
7156 * we also don't want to reduce the group load below the group
7157 * capacity. Thus we look for the minimum possible imbalance.
7159 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7161 /* How much load to actually move to equalise the imbalance */
7162 env->imbalance = min(
7163 max_pull * busiest->group_capacity,
7164 (sds->avg_load - local->avg_load) * local->group_capacity
7165 ) / SCHED_CAPACITY_SCALE;
7168 * if *imbalance is less than the average load per runnable task
7169 * there is no guarantee that any tasks will be moved so we'll have
7170 * a think about bumping its value to force at least one task to be
7173 if (env->imbalance < busiest->load_per_task)
7174 return fix_small_imbalance(env, sds);
7177 /******* find_busiest_group() helpers end here *********************/
7180 * find_busiest_group - Returns the busiest group within the sched_domain
7181 * if there is an imbalance.
7183 * Also calculates the amount of weighted load which should be moved
7184 * to restore balance.
7186 * @env: The load balancing environment.
7188 * Return: - The busiest group if imbalance exists.
7190 static struct sched_group *find_busiest_group(struct lb_env *env)
7192 struct sg_lb_stats *local, *busiest;
7193 struct sd_lb_stats sds;
7195 init_sd_lb_stats(&sds);
7198 * Compute the various statistics relavent for load balancing at
7201 update_sd_lb_stats(env, &sds);
7202 local = &sds.local_stat;
7203 busiest = &sds.busiest_stat;
7205 /* ASYM feature bypasses nice load balance check */
7206 if (check_asym_packing(env, &sds))
7209 /* There is no busy sibling group to pull tasks from */
7210 if (!sds.busiest || busiest->sum_nr_running == 0)
7213 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7214 / sds.total_capacity;
7217 * If the busiest group is imbalanced the below checks don't
7218 * work because they assume all things are equal, which typically
7219 * isn't true due to cpus_allowed constraints and the like.
7221 if (busiest->group_type == group_imbalanced)
7224 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7225 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7226 busiest->group_no_capacity)
7230 * If the local group is busier than the selected busiest group
7231 * don't try and pull any tasks.
7233 if (local->avg_load >= busiest->avg_load)
7237 * Don't pull any tasks if this group is already above the domain
7240 if (local->avg_load >= sds.avg_load)
7243 if (env->idle == CPU_IDLE) {
7245 * This cpu is idle. If the busiest group is not overloaded
7246 * and there is no imbalance between this and busiest group
7247 * wrt idle cpus, it is balanced. The imbalance becomes
7248 * significant if the diff is greater than 1 otherwise we
7249 * might end up to just move the imbalance on another group
7251 if ((busiest->group_type != group_overloaded) &&
7252 (local->idle_cpus <= (busiest->idle_cpus + 1)))
7256 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7257 * imbalance_pct to be conservative.
7259 if (100 * busiest->avg_load <=
7260 env->sd->imbalance_pct * local->avg_load)
7265 /* Looks like there is an imbalance. Compute it */
7266 calculate_imbalance(env, &sds);
7275 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7277 static struct rq *find_busiest_queue(struct lb_env *env,
7278 struct sched_group *group)
7280 struct rq *busiest = NULL, *rq;
7281 unsigned long busiest_load = 0, busiest_capacity = 1;
7284 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7285 unsigned long capacity, wl;
7289 rt = fbq_classify_rq(rq);
7292 * We classify groups/runqueues into three groups:
7293 * - regular: there are !numa tasks
7294 * - remote: there are numa tasks that run on the 'wrong' node
7295 * - all: there is no distinction
7297 * In order to avoid migrating ideally placed numa tasks,
7298 * ignore those when there's better options.
7300 * If we ignore the actual busiest queue to migrate another
7301 * task, the next balance pass can still reduce the busiest
7302 * queue by moving tasks around inside the node.
7304 * If we cannot move enough load due to this classification
7305 * the next pass will adjust the group classification and
7306 * allow migration of more tasks.
7308 * Both cases only affect the total convergence complexity.
7310 if (rt > env->fbq_type)
7313 capacity = capacity_of(i);
7315 wl = weighted_cpuload(i);
7318 * When comparing with imbalance, use weighted_cpuload()
7319 * which is not scaled with the cpu capacity.
7322 if (rq->nr_running == 1 && wl > env->imbalance &&
7323 !check_cpu_capacity(rq, env->sd))
7327 * For the load comparisons with the other cpu's, consider
7328 * the weighted_cpuload() scaled with the cpu capacity, so
7329 * that the load can be moved away from the cpu that is
7330 * potentially running at a lower capacity.
7332 * Thus we're looking for max(wl_i / capacity_i), crosswise
7333 * multiplication to rid ourselves of the division works out
7334 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7335 * our previous maximum.
7337 if (wl * busiest_capacity > busiest_load * capacity) {
7339 busiest_capacity = capacity;
7348 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7349 * so long as it is large enough.
7351 #define MAX_PINNED_INTERVAL 512
7353 /* Working cpumask for load_balance and load_balance_newidle. */
7354 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7356 static int need_active_balance(struct lb_env *env)
7358 struct sched_domain *sd = env->sd;
7360 if (env->idle == CPU_NEWLY_IDLE) {
7363 * ASYM_PACKING needs to force migrate tasks from busy but
7364 * higher numbered CPUs in order to pack all tasks in the
7365 * lowest numbered CPUs.
7367 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7372 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7373 * It's worth migrating the task if the src_cpu's capacity is reduced
7374 * because of other sched_class or IRQs if more capacity stays
7375 * available on dst_cpu.
7377 if ((env->idle != CPU_NOT_IDLE) &&
7378 (env->src_rq->cfs.h_nr_running == 1)) {
7379 if ((check_cpu_capacity(env->src_rq, sd)) &&
7380 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7384 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7387 static int active_load_balance_cpu_stop(void *data);
7389 static int should_we_balance(struct lb_env *env)
7391 struct sched_group *sg = env->sd->groups;
7392 struct cpumask *sg_cpus, *sg_mask;
7393 int cpu, balance_cpu = -1;
7396 * In the newly idle case, we will allow all the cpu's
7397 * to do the newly idle load balance.
7399 if (env->idle == CPU_NEWLY_IDLE)
7402 sg_cpus = sched_group_cpus(sg);
7403 sg_mask = sched_group_mask(sg);
7404 /* Try to find first idle cpu */
7405 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7406 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7413 if (balance_cpu == -1)
7414 balance_cpu = group_balance_cpu(sg);
7417 * First idle cpu or the first cpu(busiest) in this sched group
7418 * is eligible for doing load balancing at this and above domains.
7420 return balance_cpu == env->dst_cpu;
7424 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7425 * tasks if there is an imbalance.
7427 static int load_balance(int this_cpu, struct rq *this_rq,
7428 struct sched_domain *sd, enum cpu_idle_type idle,
7429 int *continue_balancing)
7431 int ld_moved, cur_ld_moved, active_balance = 0;
7432 struct sched_domain *sd_parent = sd->parent;
7433 struct sched_group *group;
7435 unsigned long flags;
7436 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7438 struct lb_env env = {
7440 .dst_cpu = this_cpu,
7442 .dst_grpmask = sched_group_cpus(sd->groups),
7444 .loop_break = sched_nr_migrate_break,
7447 .tasks = LIST_HEAD_INIT(env.tasks),
7451 * For NEWLY_IDLE load_balancing, we don't need to consider
7452 * other cpus in our group
7454 if (idle == CPU_NEWLY_IDLE)
7455 env.dst_grpmask = NULL;
7457 cpumask_copy(cpus, cpu_active_mask);
7459 schedstat_inc(sd, lb_count[idle]);
7462 if (!should_we_balance(&env)) {
7463 *continue_balancing = 0;
7467 group = find_busiest_group(&env);
7469 schedstat_inc(sd, lb_nobusyg[idle]);
7473 busiest = find_busiest_queue(&env, group);
7475 schedstat_inc(sd, lb_nobusyq[idle]);
7479 BUG_ON(busiest == env.dst_rq);
7481 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7483 env.src_cpu = busiest->cpu;
7484 env.src_rq = busiest;
7487 if (busiest->nr_running > 1) {
7489 * Attempt to move tasks. If find_busiest_group has found
7490 * an imbalance but busiest->nr_running <= 1, the group is
7491 * still unbalanced. ld_moved simply stays zero, so it is
7492 * correctly treated as an imbalance.
7494 env.flags |= LBF_ALL_PINNED;
7495 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7498 raw_spin_lock_irqsave(&busiest->lock, flags);
7501 * cur_ld_moved - load moved in current iteration
7502 * ld_moved - cumulative load moved across iterations
7504 cur_ld_moved = detach_tasks(&env);
7507 * We've detached some tasks from busiest_rq. Every
7508 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7509 * unlock busiest->lock, and we are able to be sure
7510 * that nobody can manipulate the tasks in parallel.
7511 * See task_rq_lock() family for the details.
7514 raw_spin_unlock(&busiest->lock);
7518 ld_moved += cur_ld_moved;
7521 local_irq_restore(flags);
7523 if (env.flags & LBF_NEED_BREAK) {
7524 env.flags &= ~LBF_NEED_BREAK;
7529 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7530 * us and move them to an alternate dst_cpu in our sched_group
7531 * where they can run. The upper limit on how many times we
7532 * iterate on same src_cpu is dependent on number of cpus in our
7535 * This changes load balance semantics a bit on who can move
7536 * load to a given_cpu. In addition to the given_cpu itself
7537 * (or a ilb_cpu acting on its behalf where given_cpu is
7538 * nohz-idle), we now have balance_cpu in a position to move
7539 * load to given_cpu. In rare situations, this may cause
7540 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7541 * _independently_ and at _same_ time to move some load to
7542 * given_cpu) causing exceess load to be moved to given_cpu.
7543 * This however should not happen so much in practice and
7544 * moreover subsequent load balance cycles should correct the
7545 * excess load moved.
7547 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7549 /* Prevent to re-select dst_cpu via env's cpus */
7550 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7552 env.dst_rq = cpu_rq(env.new_dst_cpu);
7553 env.dst_cpu = env.new_dst_cpu;
7554 env.flags &= ~LBF_DST_PINNED;
7556 env.loop_break = sched_nr_migrate_break;
7559 * Go back to "more_balance" rather than "redo" since we
7560 * need to continue with same src_cpu.
7566 * We failed to reach balance because of affinity.
7569 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7571 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7572 *group_imbalance = 1;
7575 /* All tasks on this runqueue were pinned by CPU affinity */
7576 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7577 cpumask_clear_cpu(cpu_of(busiest), cpus);
7578 if (!cpumask_empty(cpus)) {
7580 env.loop_break = sched_nr_migrate_break;
7583 goto out_all_pinned;
7588 schedstat_inc(sd, lb_failed[idle]);
7590 * Increment the failure counter only on periodic balance.
7591 * We do not want newidle balance, which can be very
7592 * frequent, pollute the failure counter causing
7593 * excessive cache_hot migrations and active balances.
7595 if (idle != CPU_NEWLY_IDLE)
7596 sd->nr_balance_failed++;
7598 if (need_active_balance(&env)) {
7599 raw_spin_lock_irqsave(&busiest->lock, flags);
7601 /* don't kick the active_load_balance_cpu_stop,
7602 * if the curr task on busiest cpu can't be
7605 if (!cpumask_test_cpu(this_cpu,
7606 tsk_cpus_allowed(busiest->curr))) {
7607 raw_spin_unlock_irqrestore(&busiest->lock,
7609 env.flags |= LBF_ALL_PINNED;
7610 goto out_one_pinned;
7614 * ->active_balance synchronizes accesses to
7615 * ->active_balance_work. Once set, it's cleared
7616 * only after active load balance is finished.
7618 if (!busiest->active_balance) {
7619 busiest->active_balance = 1;
7620 busiest->push_cpu = this_cpu;
7623 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7625 if (active_balance) {
7626 stop_one_cpu_nowait(cpu_of(busiest),
7627 active_load_balance_cpu_stop, busiest,
7628 &busiest->active_balance_work);
7631 /* We've kicked active balancing, force task migration. */
7632 sd->nr_balance_failed = sd->cache_nice_tries+1;
7635 sd->nr_balance_failed = 0;
7637 if (likely(!active_balance)) {
7638 /* We were unbalanced, so reset the balancing interval */
7639 sd->balance_interval = sd->min_interval;
7642 * If we've begun active balancing, start to back off. This
7643 * case may not be covered by the all_pinned logic if there
7644 * is only 1 task on the busy runqueue (because we don't call
7647 if (sd->balance_interval < sd->max_interval)
7648 sd->balance_interval *= 2;
7655 * We reach balance although we may have faced some affinity
7656 * constraints. Clear the imbalance flag if it was set.
7659 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7661 if (*group_imbalance)
7662 *group_imbalance = 0;
7667 * We reach balance because all tasks are pinned at this level so
7668 * we can't migrate them. Let the imbalance flag set so parent level
7669 * can try to migrate them.
7671 schedstat_inc(sd, lb_balanced[idle]);
7673 sd->nr_balance_failed = 0;
7676 /* tune up the balancing interval */
7677 if (((env.flags & LBF_ALL_PINNED) &&
7678 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7679 (sd->balance_interval < sd->max_interval))
7680 sd->balance_interval *= 2;
7687 static inline unsigned long
7688 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7690 unsigned long interval = sd->balance_interval;
7693 interval *= sd->busy_factor;
7695 /* scale ms to jiffies */
7696 interval = msecs_to_jiffies(interval);
7697 interval = clamp(interval, 1UL, max_load_balance_interval);
7703 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7705 unsigned long interval, next;
7707 interval = get_sd_balance_interval(sd, cpu_busy);
7708 next = sd->last_balance + interval;
7710 if (time_after(*next_balance, next))
7711 *next_balance = next;
7715 * idle_balance is called by schedule() if this_cpu is about to become
7716 * idle. Attempts to pull tasks from other CPUs.
7718 static int idle_balance(struct rq *this_rq)
7720 unsigned long next_balance = jiffies + HZ;
7721 int this_cpu = this_rq->cpu;
7722 struct sched_domain *sd;
7723 int pulled_task = 0;
7727 * We must set idle_stamp _before_ calling idle_balance(), such that we
7728 * measure the duration of idle_balance() as idle time.
7730 this_rq->idle_stamp = rq_clock(this_rq);
7732 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7733 !this_rq->rd->overload) {
7735 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7737 update_next_balance(sd, 0, &next_balance);
7743 raw_spin_unlock(&this_rq->lock);
7745 update_blocked_averages(this_cpu);
7747 for_each_domain(this_cpu, sd) {
7748 int continue_balancing = 1;
7749 u64 t0, domain_cost;
7751 if (!(sd->flags & SD_LOAD_BALANCE))
7754 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7755 update_next_balance(sd, 0, &next_balance);
7759 if (sd->flags & SD_BALANCE_NEWIDLE) {
7760 t0 = sched_clock_cpu(this_cpu);
7762 pulled_task = load_balance(this_cpu, this_rq,
7764 &continue_balancing);
7766 domain_cost = sched_clock_cpu(this_cpu) - t0;
7767 if (domain_cost > sd->max_newidle_lb_cost)
7768 sd->max_newidle_lb_cost = domain_cost;
7770 curr_cost += domain_cost;
7773 update_next_balance(sd, 0, &next_balance);
7776 * Stop searching for tasks to pull if there are
7777 * now runnable tasks on this rq.
7779 if (pulled_task || this_rq->nr_running > 0)
7784 raw_spin_lock(&this_rq->lock);
7786 if (curr_cost > this_rq->max_idle_balance_cost)
7787 this_rq->max_idle_balance_cost = curr_cost;
7790 * While browsing the domains, we released the rq lock, a task could
7791 * have been enqueued in the meantime. Since we're not going idle,
7792 * pretend we pulled a task.
7794 if (this_rq->cfs.h_nr_running && !pulled_task)
7798 /* Move the next balance forward */
7799 if (time_after(this_rq->next_balance, next_balance))
7800 this_rq->next_balance = next_balance;
7802 /* Is there a task of a high priority class? */
7803 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7807 this_rq->idle_stamp = 0;
7813 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7814 * running tasks off the busiest CPU onto idle CPUs. It requires at
7815 * least 1 task to be running on each physical CPU where possible, and
7816 * avoids physical / logical imbalances.
7818 static int active_load_balance_cpu_stop(void *data)
7820 struct rq *busiest_rq = data;
7821 int busiest_cpu = cpu_of(busiest_rq);
7822 int target_cpu = busiest_rq->push_cpu;
7823 struct rq *target_rq = cpu_rq(target_cpu);
7824 struct sched_domain *sd;
7825 struct task_struct *p = NULL;
7827 raw_spin_lock_irq(&busiest_rq->lock);
7829 /* make sure the requested cpu hasn't gone down in the meantime */
7830 if (unlikely(busiest_cpu != smp_processor_id() ||
7831 !busiest_rq->active_balance))
7834 /* Is there any task to move? */
7835 if (busiest_rq->nr_running <= 1)
7839 * This condition is "impossible", if it occurs
7840 * we need to fix it. Originally reported by
7841 * Bjorn Helgaas on a 128-cpu setup.
7843 BUG_ON(busiest_rq == target_rq);
7845 /* Search for an sd spanning us and the target CPU. */
7847 for_each_domain(target_cpu, sd) {
7848 if ((sd->flags & SD_LOAD_BALANCE) &&
7849 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7854 struct lb_env env = {
7856 .dst_cpu = target_cpu,
7857 .dst_rq = target_rq,
7858 .src_cpu = busiest_rq->cpu,
7859 .src_rq = busiest_rq,
7863 schedstat_inc(sd, alb_count);
7865 p = detach_one_task(&env);
7867 schedstat_inc(sd, alb_pushed);
7868 /* Active balancing done, reset the failure counter. */
7869 sd->nr_balance_failed = 0;
7871 schedstat_inc(sd, alb_failed);
7876 busiest_rq->active_balance = 0;
7877 raw_spin_unlock(&busiest_rq->lock);
7880 attach_one_task(target_rq, p);
7887 static inline int on_null_domain(struct rq *rq)
7889 return unlikely(!rcu_dereference_sched(rq->sd));
7892 #ifdef CONFIG_NO_HZ_COMMON
7894 * idle load balancing details
7895 * - When one of the busy CPUs notice that there may be an idle rebalancing
7896 * needed, they will kick the idle load balancer, which then does idle
7897 * load balancing for all the idle CPUs.
7900 cpumask_var_t idle_cpus_mask;
7902 unsigned long next_balance; /* in jiffy units */
7903 } nohz ____cacheline_aligned;
7905 static inline int find_new_ilb(void)
7907 int ilb = cpumask_first(nohz.idle_cpus_mask);
7909 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7916 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7917 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7918 * CPU (if there is one).
7920 static void nohz_balancer_kick(void)
7924 nohz.next_balance++;
7926 ilb_cpu = find_new_ilb();
7928 if (ilb_cpu >= nr_cpu_ids)
7931 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7934 * Use smp_send_reschedule() instead of resched_cpu().
7935 * This way we generate a sched IPI on the target cpu which
7936 * is idle. And the softirq performing nohz idle load balance
7937 * will be run before returning from the IPI.
7939 smp_send_reschedule(ilb_cpu);
7943 void nohz_balance_exit_idle(unsigned int cpu)
7945 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7947 * Completely isolated CPUs don't ever set, so we must test.
7949 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7950 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7951 atomic_dec(&nohz.nr_cpus);
7953 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7957 static inline void set_cpu_sd_state_busy(void)
7959 struct sched_domain *sd;
7960 int cpu = smp_processor_id();
7963 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7965 if (!sd || !sd->nohz_idle)
7969 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7974 void set_cpu_sd_state_idle(void)
7976 struct sched_domain *sd;
7977 int cpu = smp_processor_id();
7980 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7982 if (!sd || sd->nohz_idle)
7986 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7992 * This routine will record that the cpu is going idle with tick stopped.
7993 * This info will be used in performing idle load balancing in the future.
7995 void nohz_balance_enter_idle(int cpu)
7998 * If this cpu is going down, then nothing needs to be done.
8000 if (!cpu_active(cpu))
8003 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8007 * If we're a completely isolated CPU, we don't play.
8009 if (on_null_domain(cpu_rq(cpu)))
8012 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8013 atomic_inc(&nohz.nr_cpus);
8014 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8018 static DEFINE_SPINLOCK(balancing);
8021 * Scale the max load_balance interval with the number of CPUs in the system.
8022 * This trades load-balance latency on larger machines for less cross talk.
8024 void update_max_interval(void)
8026 max_load_balance_interval = HZ*num_online_cpus()/10;
8030 * It checks each scheduling domain to see if it is due to be balanced,
8031 * and initiates a balancing operation if so.
8033 * Balancing parameters are set up in init_sched_domains.
8035 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8037 int continue_balancing = 1;
8039 unsigned long interval;
8040 struct sched_domain *sd;
8041 /* Earliest time when we have to do rebalance again */
8042 unsigned long next_balance = jiffies + 60*HZ;
8043 int update_next_balance = 0;
8044 int need_serialize, need_decay = 0;
8047 update_blocked_averages(cpu);
8050 for_each_domain(cpu, sd) {
8052 * Decay the newidle max times here because this is a regular
8053 * visit to all the domains. Decay ~1% per second.
8055 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8056 sd->max_newidle_lb_cost =
8057 (sd->max_newidle_lb_cost * 253) / 256;
8058 sd->next_decay_max_lb_cost = jiffies + HZ;
8061 max_cost += sd->max_newidle_lb_cost;
8063 if (!(sd->flags & SD_LOAD_BALANCE))
8067 * Stop the load balance at this level. There is another
8068 * CPU in our sched group which is doing load balancing more
8071 if (!continue_balancing) {
8077 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8079 need_serialize = sd->flags & SD_SERIALIZE;
8080 if (need_serialize) {
8081 if (!spin_trylock(&balancing))
8085 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8086 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8088 * The LBF_DST_PINNED logic could have changed
8089 * env->dst_cpu, so we can't know our idle
8090 * state even if we migrated tasks. Update it.
8092 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8094 sd->last_balance = jiffies;
8095 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8098 spin_unlock(&balancing);
8100 if (time_after(next_balance, sd->last_balance + interval)) {
8101 next_balance = sd->last_balance + interval;
8102 update_next_balance = 1;
8107 * Ensure the rq-wide value also decays but keep it at a
8108 * reasonable floor to avoid funnies with rq->avg_idle.
8110 rq->max_idle_balance_cost =
8111 max((u64)sysctl_sched_migration_cost, max_cost);
8116 * next_balance will be updated only when there is a need.
8117 * When the cpu is attached to null domain for ex, it will not be
8120 if (likely(update_next_balance)) {
8121 rq->next_balance = next_balance;
8123 #ifdef CONFIG_NO_HZ_COMMON
8125 * If this CPU has been elected to perform the nohz idle
8126 * balance. Other idle CPUs have already rebalanced with
8127 * nohz_idle_balance() and nohz.next_balance has been
8128 * updated accordingly. This CPU is now running the idle load
8129 * balance for itself and we need to update the
8130 * nohz.next_balance accordingly.
8132 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8133 nohz.next_balance = rq->next_balance;
8138 #ifdef CONFIG_NO_HZ_COMMON
8140 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8141 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8143 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8145 int this_cpu = this_rq->cpu;
8148 /* Earliest time when we have to do rebalance again */
8149 unsigned long next_balance = jiffies + 60*HZ;
8150 int update_next_balance = 0;
8152 if (idle != CPU_IDLE ||
8153 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8156 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8157 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8161 * If this cpu gets work to do, stop the load balancing
8162 * work being done for other cpus. Next load
8163 * balancing owner will pick it up.
8168 rq = cpu_rq(balance_cpu);
8171 * If time for next balance is due,
8174 if (time_after_eq(jiffies, rq->next_balance)) {
8175 raw_spin_lock_irq(&rq->lock);
8176 update_rq_clock(rq);
8177 cpu_load_update_idle(rq);
8178 raw_spin_unlock_irq(&rq->lock);
8179 rebalance_domains(rq, CPU_IDLE);
8182 if (time_after(next_balance, rq->next_balance)) {
8183 next_balance = rq->next_balance;
8184 update_next_balance = 1;
8189 * next_balance will be updated only when there is a need.
8190 * When the CPU is attached to null domain for ex, it will not be
8193 if (likely(update_next_balance))
8194 nohz.next_balance = next_balance;
8196 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8200 * Current heuristic for kicking the idle load balancer in the presence
8201 * of an idle cpu in the system.
8202 * - This rq has more than one task.
8203 * - This rq has at least one CFS task and the capacity of the CPU is
8204 * significantly reduced because of RT tasks or IRQs.
8205 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8206 * multiple busy cpu.
8207 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8208 * domain span are idle.
8210 static inline bool nohz_kick_needed(struct rq *rq)
8212 unsigned long now = jiffies;
8213 struct sched_domain *sd;
8214 struct sched_group_capacity *sgc;
8215 int nr_busy, cpu = rq->cpu;
8218 if (unlikely(rq->idle_balance))
8222 * We may be recently in ticked or tickless idle mode. At the first
8223 * busy tick after returning from idle, we will update the busy stats.
8225 set_cpu_sd_state_busy();
8226 nohz_balance_exit_idle(cpu);
8229 * None are in tickless mode and hence no need for NOHZ idle load
8232 if (likely(!atomic_read(&nohz.nr_cpus)))
8235 if (time_before(now, nohz.next_balance))
8238 if (rq->nr_running >= 2)
8242 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8244 sgc = sd->groups->sgc;
8245 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8254 sd = rcu_dereference(rq->sd);
8256 if ((rq->cfs.h_nr_running >= 1) &&
8257 check_cpu_capacity(rq, sd)) {
8263 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8264 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8265 sched_domain_span(sd)) < cpu)) {
8275 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8279 * run_rebalance_domains is triggered when needed from the scheduler tick.
8280 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8282 static void run_rebalance_domains(struct softirq_action *h)
8284 struct rq *this_rq = this_rq();
8285 enum cpu_idle_type idle = this_rq->idle_balance ?
8286 CPU_IDLE : CPU_NOT_IDLE;
8289 * If this cpu has a pending nohz_balance_kick, then do the
8290 * balancing on behalf of the other idle cpus whose ticks are
8291 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8292 * give the idle cpus a chance to load balance. Else we may
8293 * load balance only within the local sched_domain hierarchy
8294 * and abort nohz_idle_balance altogether if we pull some load.
8296 nohz_idle_balance(this_rq, idle);
8297 rebalance_domains(this_rq, idle);
8301 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8303 void trigger_load_balance(struct rq *rq)
8305 /* Don't need to rebalance while attached to NULL domain */
8306 if (unlikely(on_null_domain(rq)))
8309 if (time_after_eq(jiffies, rq->next_balance))
8310 raise_softirq(SCHED_SOFTIRQ);
8311 #ifdef CONFIG_NO_HZ_COMMON
8312 if (nohz_kick_needed(rq))
8313 nohz_balancer_kick();
8317 static void rq_online_fair(struct rq *rq)
8321 update_runtime_enabled(rq);
8324 static void rq_offline_fair(struct rq *rq)
8328 /* Ensure any throttled groups are reachable by pick_next_task */
8329 unthrottle_offline_cfs_rqs(rq);
8332 #endif /* CONFIG_SMP */
8335 * scheduler tick hitting a task of our scheduling class:
8337 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8339 struct cfs_rq *cfs_rq;
8340 struct sched_entity *se = &curr->se;
8342 for_each_sched_entity(se) {
8343 cfs_rq = cfs_rq_of(se);
8344 entity_tick(cfs_rq, se, queued);
8347 if (static_branch_unlikely(&sched_numa_balancing))
8348 task_tick_numa(rq, curr);
8352 * called on fork with the child task as argument from the parent's context
8353 * - child not yet on the tasklist
8354 * - preemption disabled
8356 static void task_fork_fair(struct task_struct *p)
8358 struct cfs_rq *cfs_rq;
8359 struct sched_entity *se = &p->se, *curr;
8360 struct rq *rq = this_rq();
8362 raw_spin_lock(&rq->lock);
8363 update_rq_clock(rq);
8365 cfs_rq = task_cfs_rq(current);
8366 curr = cfs_rq->curr;
8368 update_curr(cfs_rq);
8369 se->vruntime = curr->vruntime;
8371 place_entity(cfs_rq, se, 1);
8373 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8375 * Upon rescheduling, sched_class::put_prev_task() will place
8376 * 'current' within the tree based on its new key value.
8378 swap(curr->vruntime, se->vruntime);
8382 se->vruntime -= cfs_rq->min_vruntime;
8383 raw_spin_unlock(&rq->lock);
8387 * Priority of the task has changed. Check to see if we preempt
8391 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8393 if (!task_on_rq_queued(p))
8397 * Reschedule if we are currently running on this runqueue and
8398 * our priority decreased, or if we are not currently running on
8399 * this runqueue and our priority is higher than the current's
8401 if (rq->curr == p) {
8402 if (p->prio > oldprio)
8405 check_preempt_curr(rq, p, 0);
8408 static inline bool vruntime_normalized(struct task_struct *p)
8410 struct sched_entity *se = &p->se;
8413 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8414 * the dequeue_entity(.flags=0) will already have normalized the
8421 * When !on_rq, vruntime of the task has usually NOT been normalized.
8422 * But there are some cases where it has already been normalized:
8424 * - A forked child which is waiting for being woken up by
8425 * wake_up_new_task().
8426 * - A task which has been woken up by try_to_wake_up() and
8427 * waiting for actually being woken up by sched_ttwu_pending().
8429 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8435 static void detach_task_cfs_rq(struct task_struct *p)
8437 struct sched_entity *se = &p->se;
8438 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8439 u64 now = cfs_rq_clock_task(cfs_rq);
8442 if (!vruntime_normalized(p)) {
8444 * Fix up our vruntime so that the current sleep doesn't
8445 * cause 'unlimited' sleep bonus.
8447 place_entity(cfs_rq, se, 0);
8448 se->vruntime -= cfs_rq->min_vruntime;
8451 /* Catch up with the cfs_rq and remove our load when we leave */
8452 tg_update = update_cfs_rq_load_avg(now, cfs_rq, false);
8453 detach_entity_load_avg(cfs_rq, se);
8455 update_tg_load_avg(cfs_rq, false);
8458 static void attach_task_cfs_rq(struct task_struct *p)
8460 struct sched_entity *se = &p->se;
8461 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8462 u64 now = cfs_rq_clock_task(cfs_rq);
8465 #ifdef CONFIG_FAIR_GROUP_SCHED
8467 * Since the real-depth could have been changed (only FAIR
8468 * class maintain depth value), reset depth properly.
8470 se->depth = se->parent ? se->parent->depth + 1 : 0;
8473 /* Synchronize task with its cfs_rq */
8474 tg_update = update_cfs_rq_load_avg(now, cfs_rq, false);
8475 attach_entity_load_avg(cfs_rq, se);
8477 update_tg_load_avg(cfs_rq, false);
8479 if (!vruntime_normalized(p))
8480 se->vruntime += cfs_rq->min_vruntime;
8483 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8485 detach_task_cfs_rq(p);
8488 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8490 attach_task_cfs_rq(p);
8492 if (task_on_rq_queued(p)) {
8494 * We were most likely switched from sched_rt, so
8495 * kick off the schedule if running, otherwise just see
8496 * if we can still preempt the current task.
8501 check_preempt_curr(rq, p, 0);
8505 /* Account for a task changing its policy or group.
8507 * This routine is mostly called to set cfs_rq->curr field when a task
8508 * migrates between groups/classes.
8510 static void set_curr_task_fair(struct rq *rq)
8512 struct sched_entity *se = &rq->curr->se;
8514 for_each_sched_entity(se) {
8515 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8517 set_next_entity(cfs_rq, se);
8518 /* ensure bandwidth has been allocated on our new cfs_rq */
8519 account_cfs_rq_runtime(cfs_rq, 0);
8523 void init_cfs_rq(struct cfs_rq *cfs_rq)
8525 cfs_rq->tasks_timeline = RB_ROOT;
8526 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8527 #ifndef CONFIG_64BIT
8528 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8531 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8532 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8536 #ifdef CONFIG_FAIR_GROUP_SCHED
8537 static void task_set_group_fair(struct task_struct *p)
8539 struct sched_entity *se = &p->se;
8541 set_task_rq(p, task_cpu(p));
8542 se->depth = se->parent ? se->parent->depth + 1 : 0;
8545 static void task_move_group_fair(struct task_struct *p)
8547 detach_task_cfs_rq(p);
8548 set_task_rq(p, task_cpu(p));
8551 /* Tell se's cfs_rq has been changed -- migrated */
8552 p->se.avg.last_update_time = 0;
8554 attach_task_cfs_rq(p);
8557 static void task_change_group_fair(struct task_struct *p, int type)
8560 case TASK_SET_GROUP:
8561 task_set_group_fair(p);
8564 case TASK_MOVE_GROUP:
8565 task_move_group_fair(p);
8570 void free_fair_sched_group(struct task_group *tg)
8574 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8576 for_each_possible_cpu(i) {
8578 kfree(tg->cfs_rq[i]);
8587 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8589 struct sched_entity *se;
8590 struct cfs_rq *cfs_rq;
8594 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8597 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8601 tg->shares = NICE_0_LOAD;
8603 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8605 for_each_possible_cpu(i) {
8608 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8609 GFP_KERNEL, cpu_to_node(i));
8613 se = kzalloc_node(sizeof(struct sched_entity),
8614 GFP_KERNEL, cpu_to_node(i));
8618 init_cfs_rq(cfs_rq);
8619 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8620 init_entity_runnable_average(se);
8631 void online_fair_sched_group(struct task_group *tg)
8633 struct sched_entity *se;
8637 for_each_possible_cpu(i) {
8641 raw_spin_lock_irq(&rq->lock);
8642 post_init_entity_util_avg(se);
8643 sync_throttle(tg, i);
8644 raw_spin_unlock_irq(&rq->lock);
8648 void unregister_fair_sched_group(struct task_group *tg)
8650 unsigned long flags;
8654 for_each_possible_cpu(cpu) {
8656 remove_entity_load_avg(tg->se[cpu]);
8659 * Only empty task groups can be destroyed; so we can speculatively
8660 * check on_list without danger of it being re-added.
8662 if (!tg->cfs_rq[cpu]->on_list)
8667 raw_spin_lock_irqsave(&rq->lock, flags);
8668 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8669 raw_spin_unlock_irqrestore(&rq->lock, flags);
8673 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8674 struct sched_entity *se, int cpu,
8675 struct sched_entity *parent)
8677 struct rq *rq = cpu_rq(cpu);
8681 init_cfs_rq_runtime(cfs_rq);
8683 tg->cfs_rq[cpu] = cfs_rq;
8686 /* se could be NULL for root_task_group */
8691 se->cfs_rq = &rq->cfs;
8694 se->cfs_rq = parent->my_q;
8695 se->depth = parent->depth + 1;
8699 /* guarantee group entities always have weight */
8700 update_load_set(&se->load, NICE_0_LOAD);
8701 se->parent = parent;
8704 static DEFINE_MUTEX(shares_mutex);
8706 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8709 unsigned long flags;
8712 * We can't change the weight of the root cgroup.
8717 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8719 mutex_lock(&shares_mutex);
8720 if (tg->shares == shares)
8723 tg->shares = shares;
8724 for_each_possible_cpu(i) {
8725 struct rq *rq = cpu_rq(i);
8726 struct sched_entity *se;
8729 /* Propagate contribution to hierarchy */
8730 raw_spin_lock_irqsave(&rq->lock, flags);
8732 /* Possible calls to update_curr() need rq clock */
8733 update_rq_clock(rq);
8734 for_each_sched_entity(se)
8735 update_cfs_shares(group_cfs_rq(se));
8736 raw_spin_unlock_irqrestore(&rq->lock, flags);
8740 mutex_unlock(&shares_mutex);
8743 #else /* CONFIG_FAIR_GROUP_SCHED */
8745 void free_fair_sched_group(struct task_group *tg) { }
8747 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8752 void online_fair_sched_group(struct task_group *tg) { }
8754 void unregister_fair_sched_group(struct task_group *tg) { }
8756 #endif /* CONFIG_FAIR_GROUP_SCHED */
8759 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8761 struct sched_entity *se = &task->se;
8762 unsigned int rr_interval = 0;
8765 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8768 if (rq->cfs.load.weight)
8769 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8775 * All the scheduling class methods:
8777 const struct sched_class fair_sched_class = {
8778 .next = &idle_sched_class,
8779 .enqueue_task = enqueue_task_fair,
8780 .dequeue_task = dequeue_task_fair,
8781 .yield_task = yield_task_fair,
8782 .yield_to_task = yield_to_task_fair,
8784 .check_preempt_curr = check_preempt_wakeup,
8786 .pick_next_task = pick_next_task_fair,
8787 .put_prev_task = put_prev_task_fair,
8790 .select_task_rq = select_task_rq_fair,
8791 .migrate_task_rq = migrate_task_rq_fair,
8793 .rq_online = rq_online_fair,
8794 .rq_offline = rq_offline_fair,
8796 .task_dead = task_dead_fair,
8797 .set_cpus_allowed = set_cpus_allowed_common,
8800 .set_curr_task = set_curr_task_fair,
8801 .task_tick = task_tick_fair,
8802 .task_fork = task_fork_fair,
8804 .prio_changed = prio_changed_fair,
8805 .switched_from = switched_from_fair,
8806 .switched_to = switched_to_fair,
8808 .get_rr_interval = get_rr_interval_fair,
8810 .update_curr = update_curr_fair,
8812 #ifdef CONFIG_FAIR_GROUP_SCHED
8813 .task_change_group = task_change_group_fair,
8817 #ifdef CONFIG_SCHED_DEBUG
8818 void print_cfs_stats(struct seq_file *m, int cpu)
8820 struct cfs_rq *cfs_rq;
8823 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8824 print_cfs_rq(m, cpu, cfs_rq);
8828 #ifdef CONFIG_NUMA_BALANCING
8829 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8832 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8834 for_each_online_node(node) {
8835 if (p->numa_faults) {
8836 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8837 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8839 if (p->numa_group) {
8840 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8841 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8843 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8846 #endif /* CONFIG_NUMA_BALANCING */
8847 #endif /* CONFIG_SCHED_DEBUG */
8849 __init void init_sched_fair_class(void)
8852 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8854 #ifdef CONFIG_NO_HZ_COMMON
8855 nohz.next_balance = jiffies;
8856 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);