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/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
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 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;
685 sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
686 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
687 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
691 void init_entity_runnable_average(struct sched_entity *se)
697 * Update the current task's runtime statistics.
699 static void update_curr(struct cfs_rq *cfs_rq)
701 struct sched_entity *curr = cfs_rq->curr;
702 u64 now = rq_clock_task(rq_of(cfs_rq));
708 delta_exec = now - curr->exec_start;
709 if (unlikely((s64)delta_exec <= 0))
712 curr->exec_start = now;
714 schedstat_set(curr->statistics.exec_max,
715 max(delta_exec, curr->statistics.exec_max));
717 curr->sum_exec_runtime += delta_exec;
718 schedstat_add(cfs_rq, exec_clock, delta_exec);
720 curr->vruntime += calc_delta_fair(delta_exec, curr);
721 update_min_vruntime(cfs_rq);
723 if (entity_is_task(curr)) {
724 struct task_struct *curtask = task_of(curr);
726 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
727 cpuacct_charge(curtask, delta_exec);
728 account_group_exec_runtime(curtask, delta_exec);
731 account_cfs_rq_runtime(cfs_rq, delta_exec);
734 static void update_curr_fair(struct rq *rq)
736 update_curr(cfs_rq_of(&rq->curr->se));
740 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
742 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
746 * Task is being enqueued - update stats:
748 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
751 * Are we enqueueing a waiting task? (for current tasks
752 * a dequeue/enqueue event is a NOP)
754 if (se != cfs_rq->curr)
755 update_stats_wait_start(cfs_rq, se);
759 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
761 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
762 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
763 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
764 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
765 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
766 #ifdef CONFIG_SCHEDSTATS
767 if (entity_is_task(se)) {
768 trace_sched_stat_wait(task_of(se),
769 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
772 schedstat_set(se->statistics.wait_start, 0);
776 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
779 * Mark the end of the wait period if dequeueing a
782 if (se != cfs_rq->curr)
783 update_stats_wait_end(cfs_rq, se);
787 * We are picking a new current task - update its stats:
790 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
793 * We are starting a new run period:
795 se->exec_start = rq_clock_task(rq_of(cfs_rq));
798 /**************************************************
799 * Scheduling class queueing methods:
802 #ifdef CONFIG_NUMA_BALANCING
804 * Approximate time to scan a full NUMA task in ms. The task scan period is
805 * calculated based on the tasks virtual memory size and
806 * numa_balancing_scan_size.
808 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
809 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
811 /* Portion of address space to scan in MB */
812 unsigned int sysctl_numa_balancing_scan_size = 256;
814 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
815 unsigned int sysctl_numa_balancing_scan_delay = 1000;
817 static unsigned int task_nr_scan_windows(struct task_struct *p)
819 unsigned long rss = 0;
820 unsigned long nr_scan_pages;
823 * Calculations based on RSS as non-present and empty pages are skipped
824 * by the PTE scanner and NUMA hinting faults should be trapped based
827 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
828 rss = get_mm_rss(p->mm);
832 rss = round_up(rss, nr_scan_pages);
833 return rss / nr_scan_pages;
836 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
837 #define MAX_SCAN_WINDOW 2560
839 static unsigned int task_scan_min(struct task_struct *p)
841 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
842 unsigned int scan, floor;
843 unsigned int windows = 1;
845 if (scan_size < MAX_SCAN_WINDOW)
846 windows = MAX_SCAN_WINDOW / scan_size;
847 floor = 1000 / windows;
849 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
850 return max_t(unsigned int, floor, scan);
853 static unsigned int task_scan_max(struct task_struct *p)
855 unsigned int smin = task_scan_min(p);
858 /* Watch for min being lower than max due to floor calculations */
859 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
860 return max(smin, smax);
863 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
865 rq->nr_numa_running += (p->numa_preferred_nid != -1);
866 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
869 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
871 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
872 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
878 spinlock_t lock; /* nr_tasks, tasks */
883 nodemask_t active_nodes;
884 unsigned long total_faults;
886 * Faults_cpu is used to decide whether memory should move
887 * towards the CPU. As a consequence, these stats are weighted
888 * more by CPU use than by memory faults.
890 unsigned long *faults_cpu;
891 unsigned long faults[0];
894 /* Shared or private faults. */
895 #define NR_NUMA_HINT_FAULT_TYPES 2
897 /* Memory and CPU locality */
898 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
900 /* Averaged statistics, and temporary buffers. */
901 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
903 pid_t task_numa_group_id(struct task_struct *p)
905 return p->numa_group ? p->numa_group->gid : 0;
909 * The averaged statistics, shared & private, memory & cpu,
910 * occupy the first half of the array. The second half of the
911 * array is for current counters, which are averaged into the
912 * first set by task_numa_placement.
914 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
916 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
919 static inline unsigned long task_faults(struct task_struct *p, int nid)
924 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
925 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
928 static inline unsigned long group_faults(struct task_struct *p, int nid)
933 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
934 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
937 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
939 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
940 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
943 /* Handle placement on systems where not all nodes are directly connected. */
944 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
945 int maxdist, bool task)
947 unsigned long score = 0;
951 * All nodes are directly connected, and the same distance
952 * from each other. No need for fancy placement algorithms.
954 if (sched_numa_topology_type == NUMA_DIRECT)
958 * This code is called for each node, introducing N^2 complexity,
959 * which should be ok given the number of nodes rarely exceeds 8.
961 for_each_online_node(node) {
962 unsigned long faults;
963 int dist = node_distance(nid, node);
966 * The furthest away nodes in the system are not interesting
967 * for placement; nid was already counted.
969 if (dist == sched_max_numa_distance || node == nid)
973 * On systems with a backplane NUMA topology, compare groups
974 * of nodes, and move tasks towards the group with the most
975 * memory accesses. When comparing two nodes at distance
976 * "hoplimit", only nodes closer by than "hoplimit" are part
977 * of each group. Skip other nodes.
979 if (sched_numa_topology_type == NUMA_BACKPLANE &&
983 /* Add up the faults from nearby nodes. */
985 faults = task_faults(p, node);
987 faults = group_faults(p, node);
990 * On systems with a glueless mesh NUMA topology, there are
991 * no fixed "groups of nodes". Instead, nodes that are not
992 * directly connected bounce traffic through intermediate
993 * nodes; a numa_group can occupy any set of nodes.
994 * The further away a node is, the less the faults count.
995 * This seems to result in good task placement.
997 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
998 faults *= (sched_max_numa_distance - dist);
999 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1009 * These return the fraction of accesses done by a particular task, or
1010 * task group, on a particular numa node. The group weight is given a
1011 * larger multiplier, in order to group tasks together that are almost
1012 * evenly spread out between numa nodes.
1014 static inline unsigned long task_weight(struct task_struct *p, int nid,
1017 unsigned long faults, total_faults;
1019 if (!p->numa_faults)
1022 total_faults = p->total_numa_faults;
1027 faults = task_faults(p, nid);
1028 faults += score_nearby_nodes(p, nid, dist, true);
1030 return 1000 * faults / total_faults;
1033 static inline unsigned long group_weight(struct task_struct *p, int nid,
1036 unsigned long faults, total_faults;
1041 total_faults = p->numa_group->total_faults;
1046 faults = group_faults(p, nid);
1047 faults += score_nearby_nodes(p, nid, dist, false);
1049 return 1000 * faults / total_faults;
1052 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1053 int src_nid, int dst_cpu)
1055 struct numa_group *ng = p->numa_group;
1056 int dst_nid = cpu_to_node(dst_cpu);
1057 int last_cpupid, this_cpupid;
1059 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1062 * Multi-stage node selection is used in conjunction with a periodic
1063 * migration fault to build a temporal task<->page relation. By using
1064 * a two-stage filter we remove short/unlikely relations.
1066 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1067 * a task's usage of a particular page (n_p) per total usage of this
1068 * page (n_t) (in a given time-span) to a probability.
1070 * Our periodic faults will sample this probability and getting the
1071 * same result twice in a row, given these samples are fully
1072 * independent, is then given by P(n)^2, provided our sample period
1073 * is sufficiently short compared to the usage pattern.
1075 * This quadric squishes small probabilities, making it less likely we
1076 * act on an unlikely task<->page relation.
1078 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1079 if (!cpupid_pid_unset(last_cpupid) &&
1080 cpupid_to_nid(last_cpupid) != dst_nid)
1083 /* Always allow migrate on private faults */
1084 if (cpupid_match_pid(p, last_cpupid))
1087 /* A shared fault, but p->numa_group has not been set up yet. */
1092 * Do not migrate if the destination is not a node that
1093 * is actively used by this numa group.
1095 if (!node_isset(dst_nid, ng->active_nodes))
1099 * Source is a node that is not actively used by this
1100 * numa group, while the destination is. Migrate.
1102 if (!node_isset(src_nid, ng->active_nodes))
1106 * Both source and destination are nodes in active
1107 * use by this numa group. Maximize memory bandwidth
1108 * by migrating from more heavily used groups, to less
1109 * heavily used ones, spreading the load around.
1110 * Use a 1/4 hysteresis to avoid spurious page movement.
1112 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1115 static unsigned long weighted_cpuload(const int cpu);
1116 static unsigned long source_load(int cpu, int type);
1117 static unsigned long target_load(int cpu, int type);
1118 static unsigned long capacity_of(int cpu);
1119 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1121 /* Cached statistics for all CPUs within a node */
1123 unsigned long nr_running;
1126 /* Total compute capacity of CPUs on a node */
1127 unsigned long compute_capacity;
1129 /* Approximate capacity in terms of runnable tasks on a node */
1130 unsigned long task_capacity;
1131 int has_free_capacity;
1135 * XXX borrowed from update_sg_lb_stats
1137 static void update_numa_stats(struct numa_stats *ns, int nid)
1139 int smt, cpu, cpus = 0;
1140 unsigned long capacity;
1142 memset(ns, 0, sizeof(*ns));
1143 for_each_cpu(cpu, cpumask_of_node(nid)) {
1144 struct rq *rq = cpu_rq(cpu);
1146 ns->nr_running += rq->nr_running;
1147 ns->load += weighted_cpuload(cpu);
1148 ns->compute_capacity += capacity_of(cpu);
1154 * If we raced with hotplug and there are no CPUs left in our mask
1155 * the @ns structure is NULL'ed and task_numa_compare() will
1156 * not find this node attractive.
1158 * We'll either bail at !has_free_capacity, or we'll detect a huge
1159 * imbalance and bail there.
1164 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1165 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1166 capacity = cpus / smt; /* cores */
1168 ns->task_capacity = min_t(unsigned, capacity,
1169 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1170 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1173 struct task_numa_env {
1174 struct task_struct *p;
1176 int src_cpu, src_nid;
1177 int dst_cpu, dst_nid;
1179 struct numa_stats src_stats, dst_stats;
1184 struct task_struct *best_task;
1189 static void task_numa_assign(struct task_numa_env *env,
1190 struct task_struct *p, long imp)
1193 put_task_struct(env->best_task);
1198 env->best_imp = imp;
1199 env->best_cpu = env->dst_cpu;
1202 static bool load_too_imbalanced(long src_load, long dst_load,
1203 struct task_numa_env *env)
1206 long orig_src_load, orig_dst_load;
1207 long src_capacity, dst_capacity;
1210 * The load is corrected for the CPU capacity available on each node.
1213 * ------------ vs ---------
1214 * src_capacity dst_capacity
1216 src_capacity = env->src_stats.compute_capacity;
1217 dst_capacity = env->dst_stats.compute_capacity;
1219 /* We care about the slope of the imbalance, not the direction. */
1220 if (dst_load < src_load)
1221 swap(dst_load, src_load);
1223 /* Is the difference below the threshold? */
1224 imb = dst_load * src_capacity * 100 -
1225 src_load * dst_capacity * env->imbalance_pct;
1230 * The imbalance is above the allowed threshold.
1231 * Compare it with the old imbalance.
1233 orig_src_load = env->src_stats.load;
1234 orig_dst_load = env->dst_stats.load;
1236 if (orig_dst_load < orig_src_load)
1237 swap(orig_dst_load, orig_src_load);
1239 old_imb = orig_dst_load * src_capacity * 100 -
1240 orig_src_load * dst_capacity * env->imbalance_pct;
1242 /* Would this change make things worse? */
1243 return (imb > old_imb);
1247 * This checks if the overall compute and NUMA accesses of the system would
1248 * be improved if the source tasks was migrated to the target dst_cpu taking
1249 * into account that it might be best if task running on the dst_cpu should
1250 * be exchanged with the source task
1252 static void task_numa_compare(struct task_numa_env *env,
1253 long taskimp, long groupimp)
1255 struct rq *src_rq = cpu_rq(env->src_cpu);
1256 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1257 struct task_struct *cur;
1258 long src_load, dst_load;
1260 long imp = env->p->numa_group ? groupimp : taskimp;
1262 int dist = env->dist;
1266 raw_spin_lock_irq(&dst_rq->lock);
1269 * No need to move the exiting task, and this ensures that ->curr
1270 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1271 * is safe under RCU read lock.
1272 * Note that rcu_read_lock() itself can't protect from the final
1273 * put_task_struct() after the last schedule().
1275 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1277 raw_spin_unlock_irq(&dst_rq->lock);
1280 * Because we have preemption enabled we can get migrated around and
1281 * end try selecting ourselves (current == env->p) as a swap candidate.
1287 * "imp" is the fault differential for the source task between the
1288 * source and destination node. Calculate the total differential for
1289 * the source task and potential destination task. The more negative
1290 * the value is, the more rmeote accesses that would be expected to
1291 * be incurred if the tasks were swapped.
1294 /* Skip this swap candidate if cannot move to the source cpu */
1295 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1299 * If dst and source tasks are in the same NUMA group, or not
1300 * in any group then look only at task weights.
1302 if (cur->numa_group == env->p->numa_group) {
1303 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1304 task_weight(cur, env->dst_nid, dist);
1306 * Add some hysteresis to prevent swapping the
1307 * tasks within a group over tiny differences.
1309 if (cur->numa_group)
1313 * Compare the group weights. If a task is all by
1314 * itself (not part of a group), use the task weight
1317 if (cur->numa_group)
1318 imp += group_weight(cur, env->src_nid, dist) -
1319 group_weight(cur, env->dst_nid, dist);
1321 imp += task_weight(cur, env->src_nid, dist) -
1322 task_weight(cur, env->dst_nid, dist);
1326 if (imp <= env->best_imp && moveimp <= env->best_imp)
1330 /* Is there capacity at our destination? */
1331 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1332 !env->dst_stats.has_free_capacity)
1338 /* Balance doesn't matter much if we're running a task per cpu */
1339 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1340 dst_rq->nr_running == 1)
1344 * In the overloaded case, try and keep the load balanced.
1347 load = task_h_load(env->p);
1348 dst_load = env->dst_stats.load + load;
1349 src_load = env->src_stats.load - load;
1351 if (moveimp > imp && moveimp > env->best_imp) {
1353 * If the improvement from just moving env->p direction is
1354 * better than swapping tasks around, check if a move is
1355 * possible. Store a slightly smaller score than moveimp,
1356 * so an actually idle CPU will win.
1358 if (!load_too_imbalanced(src_load, dst_load, env)) {
1365 if (imp <= env->best_imp)
1369 load = task_h_load(cur);
1374 if (load_too_imbalanced(src_load, dst_load, env))
1378 * One idle CPU per node is evaluated for a task numa move.
1379 * Call select_idle_sibling to maybe find a better one.
1382 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1385 task_numa_assign(env, cur, imp);
1390 static void task_numa_find_cpu(struct task_numa_env *env,
1391 long taskimp, long groupimp)
1395 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1396 /* Skip this CPU if the source task cannot migrate */
1397 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1401 task_numa_compare(env, taskimp, groupimp);
1405 /* Only move tasks to a NUMA node less busy than the current node. */
1406 static bool numa_has_capacity(struct task_numa_env *env)
1408 struct numa_stats *src = &env->src_stats;
1409 struct numa_stats *dst = &env->dst_stats;
1411 if (src->has_free_capacity && !dst->has_free_capacity)
1415 * Only consider a task move if the source has a higher load
1416 * than the destination, corrected for CPU capacity on each node.
1418 * src->load dst->load
1419 * --------------------- vs ---------------------
1420 * src->compute_capacity dst->compute_capacity
1422 if (src->load * dst->compute_capacity * env->imbalance_pct >
1424 dst->load * src->compute_capacity * 100)
1430 static int task_numa_migrate(struct task_struct *p)
1432 struct task_numa_env env = {
1435 .src_cpu = task_cpu(p),
1436 .src_nid = task_node(p),
1438 .imbalance_pct = 112,
1444 struct sched_domain *sd;
1445 unsigned long taskweight, groupweight;
1447 long taskimp, groupimp;
1450 * Pick the lowest SD_NUMA domain, as that would have the smallest
1451 * imbalance and would be the first to start moving tasks about.
1453 * And we want to avoid any moving of tasks about, as that would create
1454 * random movement of tasks -- counter the numa conditions we're trying
1458 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1460 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1464 * Cpusets can break the scheduler domain tree into smaller
1465 * balance domains, some of which do not cross NUMA boundaries.
1466 * Tasks that are "trapped" in such domains cannot be migrated
1467 * elsewhere, so there is no point in (re)trying.
1469 if (unlikely(!sd)) {
1470 p->numa_preferred_nid = task_node(p);
1474 env.dst_nid = p->numa_preferred_nid;
1475 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1476 taskweight = task_weight(p, env.src_nid, dist);
1477 groupweight = group_weight(p, env.src_nid, dist);
1478 update_numa_stats(&env.src_stats, env.src_nid);
1479 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1480 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1481 update_numa_stats(&env.dst_stats, env.dst_nid);
1483 /* Try to find a spot on the preferred nid. */
1484 if (numa_has_capacity(&env))
1485 task_numa_find_cpu(&env, taskimp, groupimp);
1488 * Look at other nodes in these cases:
1489 * - there is no space available on the preferred_nid
1490 * - the task is part of a numa_group that is interleaved across
1491 * multiple NUMA nodes; in order to better consolidate the group,
1492 * we need to check other locations.
1494 if (env.best_cpu == -1 || (p->numa_group &&
1495 nodes_weight(p->numa_group->active_nodes) > 1)) {
1496 for_each_online_node(nid) {
1497 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1500 dist = node_distance(env.src_nid, env.dst_nid);
1501 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1503 taskweight = task_weight(p, env.src_nid, dist);
1504 groupweight = group_weight(p, env.src_nid, dist);
1507 /* Only consider nodes where both task and groups benefit */
1508 taskimp = task_weight(p, nid, dist) - taskweight;
1509 groupimp = group_weight(p, nid, dist) - groupweight;
1510 if (taskimp < 0 && groupimp < 0)
1515 update_numa_stats(&env.dst_stats, env.dst_nid);
1516 if (numa_has_capacity(&env))
1517 task_numa_find_cpu(&env, taskimp, groupimp);
1522 * If the task is part of a workload that spans multiple NUMA nodes,
1523 * and is migrating into one of the workload's active nodes, remember
1524 * this node as the task's preferred numa node, so the workload can
1526 * A task that migrated to a second choice node will be better off
1527 * trying for a better one later. Do not set the preferred node here.
1529 if (p->numa_group) {
1530 if (env.best_cpu == -1)
1535 if (node_isset(nid, p->numa_group->active_nodes))
1536 sched_setnuma(p, env.dst_nid);
1539 /* No better CPU than the current one was found. */
1540 if (env.best_cpu == -1)
1544 * Reset the scan period if the task is being rescheduled on an
1545 * alternative node to recheck if the tasks is now properly placed.
1547 p->numa_scan_period = task_scan_min(p);
1549 if (env.best_task == NULL) {
1550 ret = migrate_task_to(p, env.best_cpu);
1552 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1556 ret = migrate_swap(p, env.best_task);
1558 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1559 put_task_struct(env.best_task);
1563 /* Attempt to migrate a task to a CPU on the preferred node. */
1564 static void numa_migrate_preferred(struct task_struct *p)
1566 unsigned long interval = HZ;
1568 /* This task has no NUMA fault statistics yet */
1569 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1572 /* Periodically retry migrating the task to the preferred node */
1573 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1574 p->numa_migrate_retry = jiffies + interval;
1576 /* Success if task is already running on preferred CPU */
1577 if (task_node(p) == p->numa_preferred_nid)
1580 /* Otherwise, try migrate to a CPU on the preferred node */
1581 task_numa_migrate(p);
1585 * Find the nodes on which the workload is actively running. We do this by
1586 * tracking the nodes from which NUMA hinting faults are triggered. This can
1587 * be different from the set of nodes where the workload's memory is currently
1590 * The bitmask is used to make smarter decisions on when to do NUMA page
1591 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1592 * are added when they cause over 6/16 of the maximum number of faults, but
1593 * only removed when they drop below 3/16.
1595 static void update_numa_active_node_mask(struct numa_group *numa_group)
1597 unsigned long faults, max_faults = 0;
1600 for_each_online_node(nid) {
1601 faults = group_faults_cpu(numa_group, nid);
1602 if (faults > max_faults)
1603 max_faults = faults;
1606 for_each_online_node(nid) {
1607 faults = group_faults_cpu(numa_group, nid);
1608 if (!node_isset(nid, numa_group->active_nodes)) {
1609 if (faults > max_faults * 6 / 16)
1610 node_set(nid, numa_group->active_nodes);
1611 } else if (faults < max_faults * 3 / 16)
1612 node_clear(nid, numa_group->active_nodes);
1617 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1618 * increments. The more local the fault statistics are, the higher the scan
1619 * period will be for the next scan window. If local/(local+remote) ratio is
1620 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1621 * the scan period will decrease. Aim for 70% local accesses.
1623 #define NUMA_PERIOD_SLOTS 10
1624 #define NUMA_PERIOD_THRESHOLD 7
1627 * Increase the scan period (slow down scanning) if the majority of
1628 * our memory is already on our local node, or if the majority of
1629 * the page accesses are shared with other processes.
1630 * Otherwise, decrease the scan period.
1632 static void update_task_scan_period(struct task_struct *p,
1633 unsigned long shared, unsigned long private)
1635 unsigned int period_slot;
1639 unsigned long remote = p->numa_faults_locality[0];
1640 unsigned long local = p->numa_faults_locality[1];
1643 * If there were no record hinting faults then either the task is
1644 * completely idle or all activity is areas that are not of interest
1645 * to automatic numa balancing. Related to that, if there were failed
1646 * migration then it implies we are migrating too quickly or the local
1647 * node is overloaded. In either case, scan slower
1649 if (local + shared == 0 || p->numa_faults_locality[2]) {
1650 p->numa_scan_period = min(p->numa_scan_period_max,
1651 p->numa_scan_period << 1);
1653 p->mm->numa_next_scan = jiffies +
1654 msecs_to_jiffies(p->numa_scan_period);
1660 * Prepare to scale scan period relative to the current period.
1661 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1662 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1663 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1665 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1666 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1667 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1668 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1671 diff = slot * period_slot;
1673 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1676 * Scale scan rate increases based on sharing. There is an
1677 * inverse relationship between the degree of sharing and
1678 * the adjustment made to the scanning period. Broadly
1679 * speaking the intent is that there is little point
1680 * scanning faster if shared accesses dominate as it may
1681 * simply bounce migrations uselessly
1683 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1684 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1687 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1688 task_scan_min(p), task_scan_max(p));
1689 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1693 * Get the fraction of time the task has been running since the last
1694 * NUMA placement cycle. The scheduler keeps similar statistics, but
1695 * decays those on a 32ms period, which is orders of magnitude off
1696 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1697 * stats only if the task is so new there are no NUMA statistics yet.
1699 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1701 u64 runtime, delta, now;
1702 /* Use the start of this time slice to avoid calculations. */
1703 now = p->se.exec_start;
1704 runtime = p->se.sum_exec_runtime;
1706 if (p->last_task_numa_placement) {
1707 delta = runtime - p->last_sum_exec_runtime;
1708 *period = now - p->last_task_numa_placement;
1710 delta = p->se.avg.load_sum / p->se.load.weight;
1711 *period = LOAD_AVG_MAX;
1714 p->last_sum_exec_runtime = runtime;
1715 p->last_task_numa_placement = now;
1721 * Determine the preferred nid for a task in a numa_group. This needs to
1722 * be done in a way that produces consistent results with group_weight,
1723 * otherwise workloads might not converge.
1725 static int preferred_group_nid(struct task_struct *p, int nid)
1730 /* Direct connections between all NUMA nodes. */
1731 if (sched_numa_topology_type == NUMA_DIRECT)
1735 * On a system with glueless mesh NUMA topology, group_weight
1736 * scores nodes according to the number of NUMA hinting faults on
1737 * both the node itself, and on nearby nodes.
1739 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1740 unsigned long score, max_score = 0;
1741 int node, max_node = nid;
1743 dist = sched_max_numa_distance;
1745 for_each_online_node(node) {
1746 score = group_weight(p, node, dist);
1747 if (score > max_score) {
1756 * Finding the preferred nid in a system with NUMA backplane
1757 * interconnect topology is more involved. The goal is to locate
1758 * tasks from numa_groups near each other in the system, and
1759 * untangle workloads from different sides of the system. This requires
1760 * searching down the hierarchy of node groups, recursively searching
1761 * inside the highest scoring group of nodes. The nodemask tricks
1762 * keep the complexity of the search down.
1764 nodes = node_online_map;
1765 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1766 unsigned long max_faults = 0;
1767 nodemask_t max_group = NODE_MASK_NONE;
1770 /* Are there nodes at this distance from each other? */
1771 if (!find_numa_distance(dist))
1774 for_each_node_mask(a, nodes) {
1775 unsigned long faults = 0;
1776 nodemask_t this_group;
1777 nodes_clear(this_group);
1779 /* Sum group's NUMA faults; includes a==b case. */
1780 for_each_node_mask(b, nodes) {
1781 if (node_distance(a, b) < dist) {
1782 faults += group_faults(p, b);
1783 node_set(b, this_group);
1784 node_clear(b, nodes);
1788 /* Remember the top group. */
1789 if (faults > max_faults) {
1790 max_faults = faults;
1791 max_group = this_group;
1793 * subtle: at the smallest distance there is
1794 * just one node left in each "group", the
1795 * winner is the preferred nid.
1800 /* Next round, evaluate the nodes within max_group. */
1808 static void task_numa_placement(struct task_struct *p)
1810 int seq, nid, max_nid = -1, max_group_nid = -1;
1811 unsigned long max_faults = 0, max_group_faults = 0;
1812 unsigned long fault_types[2] = { 0, 0 };
1813 unsigned long total_faults;
1814 u64 runtime, period;
1815 spinlock_t *group_lock = NULL;
1818 * The p->mm->numa_scan_seq field gets updated without
1819 * exclusive access. Use READ_ONCE() here to ensure
1820 * that the field is read in a single access:
1822 seq = READ_ONCE(p->mm->numa_scan_seq);
1823 if (p->numa_scan_seq == seq)
1825 p->numa_scan_seq = seq;
1826 p->numa_scan_period_max = task_scan_max(p);
1828 total_faults = p->numa_faults_locality[0] +
1829 p->numa_faults_locality[1];
1830 runtime = numa_get_avg_runtime(p, &period);
1832 /* If the task is part of a group prevent parallel updates to group stats */
1833 if (p->numa_group) {
1834 group_lock = &p->numa_group->lock;
1835 spin_lock_irq(group_lock);
1838 /* Find the node with the highest number of faults */
1839 for_each_online_node(nid) {
1840 /* Keep track of the offsets in numa_faults array */
1841 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1842 unsigned long faults = 0, group_faults = 0;
1845 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1846 long diff, f_diff, f_weight;
1848 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1849 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1850 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1851 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1853 /* Decay existing window, copy faults since last scan */
1854 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1855 fault_types[priv] += p->numa_faults[membuf_idx];
1856 p->numa_faults[membuf_idx] = 0;
1859 * Normalize the faults_from, so all tasks in a group
1860 * count according to CPU use, instead of by the raw
1861 * number of faults. Tasks with little runtime have
1862 * little over-all impact on throughput, and thus their
1863 * faults are less important.
1865 f_weight = div64_u64(runtime << 16, period + 1);
1866 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1868 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1869 p->numa_faults[cpubuf_idx] = 0;
1871 p->numa_faults[mem_idx] += diff;
1872 p->numa_faults[cpu_idx] += f_diff;
1873 faults += p->numa_faults[mem_idx];
1874 p->total_numa_faults += diff;
1875 if (p->numa_group) {
1877 * safe because we can only change our own group
1879 * mem_idx represents the offset for a given
1880 * nid and priv in a specific region because it
1881 * is at the beginning of the numa_faults array.
1883 p->numa_group->faults[mem_idx] += diff;
1884 p->numa_group->faults_cpu[mem_idx] += f_diff;
1885 p->numa_group->total_faults += diff;
1886 group_faults += p->numa_group->faults[mem_idx];
1890 if (faults > max_faults) {
1891 max_faults = faults;
1895 if (group_faults > max_group_faults) {
1896 max_group_faults = group_faults;
1897 max_group_nid = nid;
1901 update_task_scan_period(p, fault_types[0], fault_types[1]);
1903 if (p->numa_group) {
1904 update_numa_active_node_mask(p->numa_group);
1905 spin_unlock_irq(group_lock);
1906 max_nid = preferred_group_nid(p, max_group_nid);
1910 /* Set the new preferred node */
1911 if (max_nid != p->numa_preferred_nid)
1912 sched_setnuma(p, max_nid);
1914 if (task_node(p) != p->numa_preferred_nid)
1915 numa_migrate_preferred(p);
1919 static inline int get_numa_group(struct numa_group *grp)
1921 return atomic_inc_not_zero(&grp->refcount);
1924 static inline void put_numa_group(struct numa_group *grp)
1926 if (atomic_dec_and_test(&grp->refcount))
1927 kfree_rcu(grp, rcu);
1930 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1933 struct numa_group *grp, *my_grp;
1934 struct task_struct *tsk;
1936 int cpu = cpupid_to_cpu(cpupid);
1939 if (unlikely(!p->numa_group)) {
1940 unsigned int size = sizeof(struct numa_group) +
1941 4*nr_node_ids*sizeof(unsigned long);
1943 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1947 atomic_set(&grp->refcount, 1);
1948 spin_lock_init(&grp->lock);
1950 /* Second half of the array tracks nids where faults happen */
1951 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1954 node_set(task_node(current), grp->active_nodes);
1956 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1957 grp->faults[i] = p->numa_faults[i];
1959 grp->total_faults = p->total_numa_faults;
1962 rcu_assign_pointer(p->numa_group, grp);
1966 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1968 if (!cpupid_match_pid(tsk, cpupid))
1971 grp = rcu_dereference(tsk->numa_group);
1975 my_grp = p->numa_group;
1980 * Only join the other group if its bigger; if we're the bigger group,
1981 * the other task will join us.
1983 if (my_grp->nr_tasks > grp->nr_tasks)
1987 * Tie-break on the grp address.
1989 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1992 /* Always join threads in the same process. */
1993 if (tsk->mm == current->mm)
1996 /* Simple filter to avoid false positives due to PID collisions */
1997 if (flags & TNF_SHARED)
2000 /* Update priv based on whether false sharing was detected */
2003 if (join && !get_numa_group(grp))
2011 BUG_ON(irqs_disabled());
2012 double_lock_irq(&my_grp->lock, &grp->lock);
2014 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2015 my_grp->faults[i] -= p->numa_faults[i];
2016 grp->faults[i] += p->numa_faults[i];
2018 my_grp->total_faults -= p->total_numa_faults;
2019 grp->total_faults += p->total_numa_faults;
2024 spin_unlock(&my_grp->lock);
2025 spin_unlock_irq(&grp->lock);
2027 rcu_assign_pointer(p->numa_group, grp);
2029 put_numa_group(my_grp);
2037 void task_numa_free(struct task_struct *p)
2039 struct numa_group *grp = p->numa_group;
2040 void *numa_faults = p->numa_faults;
2041 unsigned long flags;
2045 spin_lock_irqsave(&grp->lock, flags);
2046 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2047 grp->faults[i] -= p->numa_faults[i];
2048 grp->total_faults -= p->total_numa_faults;
2051 spin_unlock_irqrestore(&grp->lock, flags);
2052 RCU_INIT_POINTER(p->numa_group, NULL);
2053 put_numa_group(grp);
2056 p->numa_faults = NULL;
2061 * Got a PROT_NONE fault for a page on @node.
2063 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2065 struct task_struct *p = current;
2066 bool migrated = flags & TNF_MIGRATED;
2067 int cpu_node = task_node(current);
2068 int local = !!(flags & TNF_FAULT_LOCAL);
2071 if (!static_branch_likely(&sched_numa_balancing))
2074 /* for example, ksmd faulting in a user's mm */
2078 /* Allocate buffer to track faults on a per-node basis */
2079 if (unlikely(!p->numa_faults)) {
2080 int size = sizeof(*p->numa_faults) *
2081 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2083 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2084 if (!p->numa_faults)
2087 p->total_numa_faults = 0;
2088 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2092 * First accesses are treated as private, otherwise consider accesses
2093 * to be private if the accessing pid has not changed
2095 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2098 priv = cpupid_match_pid(p, last_cpupid);
2099 if (!priv && !(flags & TNF_NO_GROUP))
2100 task_numa_group(p, last_cpupid, flags, &priv);
2104 * If a workload spans multiple NUMA nodes, a shared fault that
2105 * occurs wholly within the set of nodes that the workload is
2106 * actively using should be counted as local. This allows the
2107 * scan rate to slow down when a workload has settled down.
2109 if (!priv && !local && p->numa_group &&
2110 node_isset(cpu_node, p->numa_group->active_nodes) &&
2111 node_isset(mem_node, p->numa_group->active_nodes))
2114 task_numa_placement(p);
2117 * Retry task to preferred node migration periodically, in case it
2118 * case it previously failed, or the scheduler moved us.
2120 if (time_after(jiffies, p->numa_migrate_retry))
2121 numa_migrate_preferred(p);
2124 p->numa_pages_migrated += pages;
2125 if (flags & TNF_MIGRATE_FAIL)
2126 p->numa_faults_locality[2] += pages;
2128 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2129 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2130 p->numa_faults_locality[local] += pages;
2133 static void reset_ptenuma_scan(struct task_struct *p)
2136 * We only did a read acquisition of the mmap sem, so
2137 * p->mm->numa_scan_seq is written to without exclusive access
2138 * and the update is not guaranteed to be atomic. That's not
2139 * much of an issue though, since this is just used for
2140 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2141 * expensive, to avoid any form of compiler optimizations:
2143 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2144 p->mm->numa_scan_offset = 0;
2148 * The expensive part of numa migration is done from task_work context.
2149 * Triggered from task_tick_numa().
2151 void task_numa_work(struct callback_head *work)
2153 unsigned long migrate, next_scan, now = jiffies;
2154 struct task_struct *p = current;
2155 struct mm_struct *mm = p->mm;
2156 struct vm_area_struct *vma;
2157 unsigned long start, end;
2158 unsigned long nr_pte_updates = 0;
2159 long pages, virtpages;
2161 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2163 work->next = work; /* protect against double add */
2165 * Who cares about NUMA placement when they're dying.
2167 * NOTE: make sure not to dereference p->mm before this check,
2168 * exit_task_work() happens _after_ exit_mm() so we could be called
2169 * without p->mm even though we still had it when we enqueued this
2172 if (p->flags & PF_EXITING)
2175 if (!mm->numa_next_scan) {
2176 mm->numa_next_scan = now +
2177 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2181 * Enforce maximal scan/migration frequency..
2183 migrate = mm->numa_next_scan;
2184 if (time_before(now, migrate))
2187 if (p->numa_scan_period == 0) {
2188 p->numa_scan_period_max = task_scan_max(p);
2189 p->numa_scan_period = task_scan_min(p);
2192 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2193 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2197 * Delay this task enough that another task of this mm will likely win
2198 * the next time around.
2200 p->node_stamp += 2 * TICK_NSEC;
2202 start = mm->numa_scan_offset;
2203 pages = sysctl_numa_balancing_scan_size;
2204 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2205 virtpages = pages * 8; /* Scan up to this much virtual space */
2210 down_read(&mm->mmap_sem);
2211 vma = find_vma(mm, start);
2213 reset_ptenuma_scan(p);
2217 for (; vma; vma = vma->vm_next) {
2218 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2219 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2224 * Shared library pages mapped by multiple processes are not
2225 * migrated as it is expected they are cache replicated. Avoid
2226 * hinting faults in read-only file-backed mappings or the vdso
2227 * as migrating the pages will be of marginal benefit.
2230 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2234 * Skip inaccessible VMAs to avoid any confusion between
2235 * PROT_NONE and NUMA hinting ptes
2237 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2241 start = max(start, vma->vm_start);
2242 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2243 end = min(end, vma->vm_end);
2244 nr_pte_updates = change_prot_numa(vma, start, end);
2247 * Try to scan sysctl_numa_balancing_size worth of
2248 * hpages that have at least one present PTE that
2249 * is not already pte-numa. If the VMA contains
2250 * areas that are unused or already full of prot_numa
2251 * PTEs, scan up to virtpages, to skip through those
2255 pages -= (end - start) >> PAGE_SHIFT;
2256 virtpages -= (end - start) >> PAGE_SHIFT;
2259 if (pages <= 0 || virtpages <= 0)
2263 } while (end != vma->vm_end);
2268 * It is possible to reach the end of the VMA list but the last few
2269 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2270 * would find the !migratable VMA on the next scan but not reset the
2271 * scanner to the start so check it now.
2274 mm->numa_scan_offset = start;
2276 reset_ptenuma_scan(p);
2277 up_read(&mm->mmap_sem);
2281 * Drive the periodic memory faults..
2283 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2285 struct callback_head *work = &curr->numa_work;
2289 * We don't care about NUMA placement if we don't have memory.
2291 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2295 * Using runtime rather than walltime has the dual advantage that
2296 * we (mostly) drive the selection from busy threads and that the
2297 * task needs to have done some actual work before we bother with
2300 now = curr->se.sum_exec_runtime;
2301 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2303 if (now > curr->node_stamp + period) {
2304 if (!curr->node_stamp)
2305 curr->numa_scan_period = task_scan_min(curr);
2306 curr->node_stamp += period;
2308 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2309 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2310 task_work_add(curr, work, true);
2315 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2319 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2323 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2326 #endif /* CONFIG_NUMA_BALANCING */
2329 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2331 update_load_add(&cfs_rq->load, se->load.weight);
2332 if (!parent_entity(se))
2333 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2335 if (entity_is_task(se)) {
2336 struct rq *rq = rq_of(cfs_rq);
2338 account_numa_enqueue(rq, task_of(se));
2339 list_add(&se->group_node, &rq->cfs_tasks);
2342 cfs_rq->nr_running++;
2346 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2348 update_load_sub(&cfs_rq->load, se->load.weight);
2349 if (!parent_entity(se))
2350 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2351 if (entity_is_task(se)) {
2352 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2353 list_del_init(&se->group_node);
2355 cfs_rq->nr_running--;
2358 #ifdef CONFIG_FAIR_GROUP_SCHED
2360 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2365 * Use this CPU's real-time load instead of the last load contribution
2366 * as the updating of the contribution is delayed, and we will use the
2367 * the real-time load to calc the share. See update_tg_load_avg().
2369 tg_weight = atomic_long_read(&tg->load_avg);
2370 tg_weight -= cfs_rq->tg_load_avg_contrib;
2371 tg_weight += cfs_rq->load.weight;
2376 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2378 long tg_weight, load, shares;
2380 tg_weight = calc_tg_weight(tg, cfs_rq);
2381 load = cfs_rq->load.weight;
2383 shares = (tg->shares * load);
2385 shares /= tg_weight;
2387 if (shares < MIN_SHARES)
2388 shares = MIN_SHARES;
2389 if (shares > tg->shares)
2390 shares = tg->shares;
2394 # else /* CONFIG_SMP */
2395 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2399 # endif /* CONFIG_SMP */
2400 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2401 unsigned long weight)
2404 /* commit outstanding execution time */
2405 if (cfs_rq->curr == se)
2406 update_curr(cfs_rq);
2407 account_entity_dequeue(cfs_rq, se);
2410 update_load_set(&se->load, weight);
2413 account_entity_enqueue(cfs_rq, se);
2416 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2418 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2420 struct task_group *tg;
2421 struct sched_entity *se;
2425 se = tg->se[cpu_of(rq_of(cfs_rq))];
2426 if (!se || throttled_hierarchy(cfs_rq))
2429 if (likely(se->load.weight == tg->shares))
2432 shares = calc_cfs_shares(cfs_rq, tg);
2434 reweight_entity(cfs_rq_of(se), se, shares);
2436 #else /* CONFIG_FAIR_GROUP_SCHED */
2437 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2440 #endif /* CONFIG_FAIR_GROUP_SCHED */
2443 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2444 static const u32 runnable_avg_yN_inv[] = {
2445 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2446 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2447 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2448 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2449 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2450 0x85aac367, 0x82cd8698,
2454 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2455 * over-estimates when re-combining.
2457 static const u32 runnable_avg_yN_sum[] = {
2458 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2459 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2460 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2465 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2467 static __always_inline u64 decay_load(u64 val, u64 n)
2469 unsigned int local_n;
2473 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2476 /* after bounds checking we can collapse to 32-bit */
2480 * As y^PERIOD = 1/2, we can combine
2481 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2482 * With a look-up table which covers y^n (n<PERIOD)
2484 * To achieve constant time decay_load.
2486 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2487 val >>= local_n / LOAD_AVG_PERIOD;
2488 local_n %= LOAD_AVG_PERIOD;
2491 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2496 * For updates fully spanning n periods, the contribution to runnable
2497 * average will be: \Sum 1024*y^n
2499 * We can compute this reasonably efficiently by combining:
2500 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2502 static u32 __compute_runnable_contrib(u64 n)
2506 if (likely(n <= LOAD_AVG_PERIOD))
2507 return runnable_avg_yN_sum[n];
2508 else if (unlikely(n >= LOAD_AVG_MAX_N))
2509 return LOAD_AVG_MAX;
2511 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2513 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2514 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2516 n -= LOAD_AVG_PERIOD;
2517 } while (n > LOAD_AVG_PERIOD);
2519 contrib = decay_load(contrib, n);
2520 return contrib + runnable_avg_yN_sum[n];
2523 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2524 #error "load tracking assumes 2^10 as unit"
2527 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2530 * We can represent the historical contribution to runnable average as the
2531 * coefficients of a geometric series. To do this we sub-divide our runnable
2532 * history into segments of approximately 1ms (1024us); label the segment that
2533 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2535 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2537 * (now) (~1ms ago) (~2ms ago)
2539 * Let u_i denote the fraction of p_i that the entity was runnable.
2541 * We then designate the fractions u_i as our co-efficients, yielding the
2542 * following representation of historical load:
2543 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2545 * We choose y based on the with of a reasonably scheduling period, fixing:
2548 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2549 * approximately half as much as the contribution to load within the last ms
2552 * When a period "rolls over" and we have new u_0`, multiplying the previous
2553 * sum again by y is sufficient to update:
2554 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2555 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2557 static __always_inline int
2558 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2559 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2561 u64 delta, scaled_delta, periods;
2563 unsigned int delta_w, scaled_delta_w, decayed = 0;
2564 unsigned long scale_freq, scale_cpu;
2566 delta = now - sa->last_update_time;
2568 * This should only happen when time goes backwards, which it
2569 * unfortunately does during sched clock init when we swap over to TSC.
2571 if ((s64)delta < 0) {
2572 sa->last_update_time = now;
2577 * Use 1024ns as the unit of measurement since it's a reasonable
2578 * approximation of 1us and fast to compute.
2583 sa->last_update_time = now;
2585 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2586 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2588 /* delta_w is the amount already accumulated against our next period */
2589 delta_w = sa->period_contrib;
2590 if (delta + delta_w >= 1024) {
2593 /* how much left for next period will start over, we don't know yet */
2594 sa->period_contrib = 0;
2597 * Now that we know we're crossing a period boundary, figure
2598 * out how much from delta we need to complete the current
2599 * period and accrue it.
2601 delta_w = 1024 - delta_w;
2602 scaled_delta_w = cap_scale(delta_w, scale_freq);
2604 sa->load_sum += weight * scaled_delta_w;
2606 cfs_rq->runnable_load_sum +=
2607 weight * scaled_delta_w;
2611 sa->util_sum += scaled_delta_w * scale_cpu;
2615 /* Figure out how many additional periods this update spans */
2616 periods = delta / 1024;
2619 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2621 cfs_rq->runnable_load_sum =
2622 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2624 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2626 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2627 contrib = __compute_runnable_contrib(periods);
2628 contrib = cap_scale(contrib, scale_freq);
2630 sa->load_sum += weight * contrib;
2632 cfs_rq->runnable_load_sum += weight * contrib;
2635 sa->util_sum += contrib * scale_cpu;
2638 /* Remainder of delta accrued against u_0` */
2639 scaled_delta = cap_scale(delta, scale_freq);
2641 sa->load_sum += weight * scaled_delta;
2643 cfs_rq->runnable_load_sum += weight * scaled_delta;
2646 sa->util_sum += scaled_delta * scale_cpu;
2648 sa->period_contrib += delta;
2651 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2653 cfs_rq->runnable_load_avg =
2654 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2656 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2662 #ifdef CONFIG_FAIR_GROUP_SCHED
2664 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2665 * and effective_load (which is not done because it is too costly).
2667 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2669 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2671 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2672 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2673 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2677 #else /* CONFIG_FAIR_GROUP_SCHED */
2678 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2679 #endif /* CONFIG_FAIR_GROUP_SCHED */
2681 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2684 * Unsigned subtract and clamp on underflow.
2686 * Explicitly do a load-store to ensure the intermediate value never hits
2687 * memory. This allows lockless observations without ever seeing the negative
2690 #define sub_positive(_ptr, _val) do { \
2691 typeof(_ptr) ptr = (_ptr); \
2692 typeof(*ptr) val = (_val); \
2693 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2697 WRITE_ONCE(*ptr, res); \
2700 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2701 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2703 struct sched_avg *sa = &cfs_rq->avg;
2704 int decayed, removed = 0;
2706 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2707 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2708 sub_positive(&sa->load_avg, r);
2709 sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
2713 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2714 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2715 sub_positive(&sa->util_avg, r);
2716 sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
2719 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2720 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2722 #ifndef CONFIG_64BIT
2724 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2727 return decayed || removed;
2730 /* Update task and its cfs_rq load average */
2731 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2733 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2734 u64 now = cfs_rq_clock_task(cfs_rq);
2735 int cpu = cpu_of(rq_of(cfs_rq));
2738 * Track task load average for carrying it to new CPU after migrated, and
2739 * track group sched_entity load average for task_h_load calc in migration
2741 __update_load_avg(now, cpu, &se->avg,
2742 se->on_rq * scale_load_down(se->load.weight),
2743 cfs_rq->curr == se, NULL);
2745 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2746 update_tg_load_avg(cfs_rq, 0);
2749 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2751 if (!sched_feat(ATTACH_AGE_LOAD))
2755 * If we got migrated (either between CPUs or between cgroups) we'll
2756 * have aged the average right before clearing @last_update_time.
2758 if (se->avg.last_update_time) {
2759 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2760 &se->avg, 0, 0, NULL);
2763 * XXX: we could have just aged the entire load away if we've been
2764 * absent from the fair class for too long.
2769 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2770 cfs_rq->avg.load_avg += se->avg.load_avg;
2771 cfs_rq->avg.load_sum += se->avg.load_sum;
2772 cfs_rq->avg.util_avg += se->avg.util_avg;
2773 cfs_rq->avg.util_sum += se->avg.util_sum;
2776 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2778 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2779 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2780 cfs_rq->curr == se, NULL);
2782 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
2783 sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
2784 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
2785 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
2788 /* Add the load generated by se into cfs_rq's load average */
2790 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2792 struct sched_avg *sa = &se->avg;
2793 u64 now = cfs_rq_clock_task(cfs_rq);
2794 int migrated, decayed;
2796 migrated = !sa->last_update_time;
2798 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2799 se->on_rq * scale_load_down(se->load.weight),
2800 cfs_rq->curr == se, NULL);
2803 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2805 cfs_rq->runnable_load_avg += sa->load_avg;
2806 cfs_rq->runnable_load_sum += sa->load_sum;
2809 attach_entity_load_avg(cfs_rq, se);
2811 if (decayed || migrated)
2812 update_tg_load_avg(cfs_rq, 0);
2815 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2817 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2819 update_load_avg(se, 1);
2821 cfs_rq->runnable_load_avg =
2822 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2823 cfs_rq->runnable_load_sum =
2824 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2827 #ifndef CONFIG_64BIT
2828 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2830 u64 last_update_time_copy;
2831 u64 last_update_time;
2834 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2836 last_update_time = cfs_rq->avg.last_update_time;
2837 } while (last_update_time != last_update_time_copy);
2839 return last_update_time;
2842 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2844 return cfs_rq->avg.last_update_time;
2849 * Task first catches up with cfs_rq, and then subtract
2850 * itself from the cfs_rq (task must be off the queue now).
2852 void remove_entity_load_avg(struct sched_entity *se)
2854 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2855 u64 last_update_time;
2858 * Newly created task or never used group entity should not be removed
2859 * from its (source) cfs_rq
2861 if (se->avg.last_update_time == 0)
2864 last_update_time = cfs_rq_last_update_time(cfs_rq);
2866 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2867 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2868 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2872 * Update the rq's load with the elapsed running time before entering
2873 * idle. if the last scheduled task is not a CFS task, idle_enter will
2874 * be the only way to update the runnable statistic.
2876 void idle_enter_fair(struct rq *this_rq)
2881 * Update the rq's load with the elapsed idle time before a task is
2882 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2883 * be the only way to update the runnable statistic.
2885 void idle_exit_fair(struct rq *this_rq)
2889 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2891 return cfs_rq->runnable_load_avg;
2894 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2896 return cfs_rq->avg.load_avg;
2899 static int idle_balance(struct rq *this_rq);
2901 #else /* CONFIG_SMP */
2903 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2905 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2907 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2908 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2911 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2913 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2915 static inline int idle_balance(struct rq *rq)
2920 #endif /* CONFIG_SMP */
2922 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2924 #ifdef CONFIG_SCHEDSTATS
2925 struct task_struct *tsk = NULL;
2927 if (entity_is_task(se))
2930 if (se->statistics.sleep_start) {
2931 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2936 if (unlikely(delta > se->statistics.sleep_max))
2937 se->statistics.sleep_max = delta;
2939 se->statistics.sleep_start = 0;
2940 se->statistics.sum_sleep_runtime += delta;
2943 account_scheduler_latency(tsk, delta >> 10, 1);
2944 trace_sched_stat_sleep(tsk, delta);
2947 if (se->statistics.block_start) {
2948 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2953 if (unlikely(delta > se->statistics.block_max))
2954 se->statistics.block_max = delta;
2956 se->statistics.block_start = 0;
2957 se->statistics.sum_sleep_runtime += delta;
2960 if (tsk->in_iowait) {
2961 se->statistics.iowait_sum += delta;
2962 se->statistics.iowait_count++;
2963 trace_sched_stat_iowait(tsk, delta);
2966 trace_sched_stat_blocked(tsk, delta);
2967 trace_sched_blocked_reason(tsk);
2970 * Blocking time is in units of nanosecs, so shift by
2971 * 20 to get a milliseconds-range estimation of the
2972 * amount of time that the task spent sleeping:
2974 if (unlikely(prof_on == SLEEP_PROFILING)) {
2975 profile_hits(SLEEP_PROFILING,
2976 (void *)get_wchan(tsk),
2979 account_scheduler_latency(tsk, delta >> 10, 0);
2985 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2987 #ifdef CONFIG_SCHED_DEBUG
2988 s64 d = se->vruntime - cfs_rq->min_vruntime;
2993 if (d > 3*sysctl_sched_latency)
2994 schedstat_inc(cfs_rq, nr_spread_over);
2999 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3001 u64 vruntime = cfs_rq->min_vruntime;
3004 * The 'current' period is already promised to the current tasks,
3005 * however the extra weight of the new task will slow them down a
3006 * little, place the new task so that it fits in the slot that
3007 * stays open at the end.
3009 if (initial && sched_feat(START_DEBIT))
3010 vruntime += sched_vslice(cfs_rq, se);
3012 /* sleeps up to a single latency don't count. */
3014 unsigned long thresh = sysctl_sched_latency;
3017 * Halve their sleep time's effect, to allow
3018 * for a gentler effect of sleepers:
3020 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3026 /* ensure we never gain time by being placed backwards. */
3027 se->vruntime = max_vruntime(se->vruntime, vruntime);
3030 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3033 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3036 * Update the normalized vruntime before updating min_vruntime
3037 * through calling update_curr().
3039 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3040 se->vruntime += cfs_rq->min_vruntime;
3043 * Update run-time statistics of the 'current'.
3045 update_curr(cfs_rq);
3046 enqueue_entity_load_avg(cfs_rq, se);
3047 account_entity_enqueue(cfs_rq, se);
3048 update_cfs_shares(cfs_rq);
3050 if (flags & ENQUEUE_WAKEUP) {
3051 place_entity(cfs_rq, se, 0);
3052 enqueue_sleeper(cfs_rq, se);
3055 update_stats_enqueue(cfs_rq, se);
3056 check_spread(cfs_rq, se);
3057 if (se != cfs_rq->curr)
3058 __enqueue_entity(cfs_rq, se);
3061 if (cfs_rq->nr_running == 1) {
3062 list_add_leaf_cfs_rq(cfs_rq);
3063 check_enqueue_throttle(cfs_rq);
3067 static void __clear_buddies_last(struct sched_entity *se)
3069 for_each_sched_entity(se) {
3070 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3071 if (cfs_rq->last != se)
3074 cfs_rq->last = NULL;
3078 static void __clear_buddies_next(struct sched_entity *se)
3080 for_each_sched_entity(se) {
3081 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3082 if (cfs_rq->next != se)
3085 cfs_rq->next = NULL;
3089 static void __clear_buddies_skip(struct sched_entity *se)
3091 for_each_sched_entity(se) {
3092 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3093 if (cfs_rq->skip != se)
3096 cfs_rq->skip = NULL;
3100 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3102 if (cfs_rq->last == se)
3103 __clear_buddies_last(se);
3105 if (cfs_rq->next == se)
3106 __clear_buddies_next(se);
3108 if (cfs_rq->skip == se)
3109 __clear_buddies_skip(se);
3112 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3115 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3118 * Update run-time statistics of the 'current'.
3120 update_curr(cfs_rq);
3121 dequeue_entity_load_avg(cfs_rq, se);
3123 update_stats_dequeue(cfs_rq, se);
3124 if (flags & DEQUEUE_SLEEP) {
3125 #ifdef CONFIG_SCHEDSTATS
3126 if (entity_is_task(se)) {
3127 struct task_struct *tsk = task_of(se);
3129 if (tsk->state & TASK_INTERRUPTIBLE)
3130 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3131 if (tsk->state & TASK_UNINTERRUPTIBLE)
3132 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3137 clear_buddies(cfs_rq, se);
3139 if (se != cfs_rq->curr)
3140 __dequeue_entity(cfs_rq, se);
3142 account_entity_dequeue(cfs_rq, se);
3145 * Normalize the entity after updating the min_vruntime because the
3146 * update can refer to the ->curr item and we need to reflect this
3147 * movement in our normalized position.
3149 if (!(flags & DEQUEUE_SLEEP))
3150 se->vruntime -= cfs_rq->min_vruntime;
3152 /* return excess runtime on last dequeue */
3153 return_cfs_rq_runtime(cfs_rq);
3155 update_min_vruntime(cfs_rq);
3156 update_cfs_shares(cfs_rq);
3160 * Preempt the current task with a newly woken task if needed:
3163 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3165 unsigned long ideal_runtime, delta_exec;
3166 struct sched_entity *se;
3169 ideal_runtime = sched_slice(cfs_rq, curr);
3170 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3171 if (delta_exec > ideal_runtime) {
3172 resched_curr(rq_of(cfs_rq));
3174 * The current task ran long enough, ensure it doesn't get
3175 * re-elected due to buddy favours.
3177 clear_buddies(cfs_rq, curr);
3182 * Ensure that a task that missed wakeup preemption by a
3183 * narrow margin doesn't have to wait for a full slice.
3184 * This also mitigates buddy induced latencies under load.
3186 if (delta_exec < sysctl_sched_min_granularity)
3189 se = __pick_first_entity(cfs_rq);
3190 delta = curr->vruntime - se->vruntime;
3195 if (delta > ideal_runtime)
3196 resched_curr(rq_of(cfs_rq));
3200 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3202 /* 'current' is not kept within the tree. */
3205 * Any task has to be enqueued before it get to execute on
3206 * a CPU. So account for the time it spent waiting on the
3209 update_stats_wait_end(cfs_rq, se);
3210 __dequeue_entity(cfs_rq, se);
3211 update_load_avg(se, 1);
3214 update_stats_curr_start(cfs_rq, se);
3216 #ifdef CONFIG_SCHEDSTATS
3218 * Track our maximum slice length, if the CPU's load is at
3219 * least twice that of our own weight (i.e. dont track it
3220 * when there are only lesser-weight tasks around):
3222 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3223 se->statistics.slice_max = max(se->statistics.slice_max,
3224 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3227 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3231 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3234 * Pick the next process, keeping these things in mind, in this order:
3235 * 1) keep things fair between processes/task groups
3236 * 2) pick the "next" process, since someone really wants that to run
3237 * 3) pick the "last" process, for cache locality
3238 * 4) do not run the "skip" process, if something else is available
3240 static struct sched_entity *
3241 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3243 struct sched_entity *left = __pick_first_entity(cfs_rq);
3244 struct sched_entity *se;
3247 * If curr is set we have to see if its left of the leftmost entity
3248 * still in the tree, provided there was anything in the tree at all.
3250 if (!left || (curr && entity_before(curr, left)))
3253 se = left; /* ideally we run the leftmost entity */
3256 * Avoid running the skip buddy, if running something else can
3257 * be done without getting too unfair.
3259 if (cfs_rq->skip == se) {
3260 struct sched_entity *second;
3263 second = __pick_first_entity(cfs_rq);
3265 second = __pick_next_entity(se);
3266 if (!second || (curr && entity_before(curr, second)))
3270 if (second && wakeup_preempt_entity(second, left) < 1)
3275 * Prefer last buddy, try to return the CPU to a preempted task.
3277 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3281 * Someone really wants this to run. If it's not unfair, run it.
3283 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3286 clear_buddies(cfs_rq, se);
3291 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3293 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3296 * If still on the runqueue then deactivate_task()
3297 * was not called and update_curr() has to be done:
3300 update_curr(cfs_rq);
3302 /* throttle cfs_rqs exceeding runtime */
3303 check_cfs_rq_runtime(cfs_rq);
3305 check_spread(cfs_rq, prev);
3307 update_stats_wait_start(cfs_rq, prev);
3308 /* Put 'current' back into the tree. */
3309 __enqueue_entity(cfs_rq, prev);
3310 /* in !on_rq case, update occurred at dequeue */
3311 update_load_avg(prev, 0);
3313 cfs_rq->curr = NULL;
3317 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3320 * Update run-time statistics of the 'current'.
3322 update_curr(cfs_rq);
3325 * Ensure that runnable average is periodically updated.
3327 update_load_avg(curr, 1);
3328 update_cfs_shares(cfs_rq);
3330 #ifdef CONFIG_SCHED_HRTICK
3332 * queued ticks are scheduled to match the slice, so don't bother
3333 * validating it and just reschedule.
3336 resched_curr(rq_of(cfs_rq));
3340 * don't let the period tick interfere with the hrtick preemption
3342 if (!sched_feat(DOUBLE_TICK) &&
3343 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3347 if (cfs_rq->nr_running > 1)
3348 check_preempt_tick(cfs_rq, curr);
3352 /**************************************************
3353 * CFS bandwidth control machinery
3356 #ifdef CONFIG_CFS_BANDWIDTH
3358 #ifdef HAVE_JUMP_LABEL
3359 static struct static_key __cfs_bandwidth_used;
3361 static inline bool cfs_bandwidth_used(void)
3363 return static_key_false(&__cfs_bandwidth_used);
3366 void cfs_bandwidth_usage_inc(void)
3368 static_key_slow_inc(&__cfs_bandwidth_used);
3371 void cfs_bandwidth_usage_dec(void)
3373 static_key_slow_dec(&__cfs_bandwidth_used);
3375 #else /* HAVE_JUMP_LABEL */
3376 static bool cfs_bandwidth_used(void)
3381 void cfs_bandwidth_usage_inc(void) {}
3382 void cfs_bandwidth_usage_dec(void) {}
3383 #endif /* HAVE_JUMP_LABEL */
3386 * default period for cfs group bandwidth.
3387 * default: 0.1s, units: nanoseconds
3389 static inline u64 default_cfs_period(void)
3391 return 100000000ULL;
3394 static inline u64 sched_cfs_bandwidth_slice(void)
3396 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3400 * Replenish runtime according to assigned quota and update expiration time.
3401 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3402 * additional synchronization around rq->lock.
3404 * requires cfs_b->lock
3406 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3410 if (cfs_b->quota == RUNTIME_INF)
3413 now = sched_clock_cpu(smp_processor_id());
3414 cfs_b->runtime = cfs_b->quota;
3415 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3418 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3420 return &tg->cfs_bandwidth;
3423 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3424 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3426 if (unlikely(cfs_rq->throttle_count))
3427 return cfs_rq->throttled_clock_task;
3429 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3432 /* returns 0 on failure to allocate runtime */
3433 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3435 struct task_group *tg = cfs_rq->tg;
3436 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3437 u64 amount = 0, min_amount, expires;
3439 /* note: this is a positive sum as runtime_remaining <= 0 */
3440 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3442 raw_spin_lock(&cfs_b->lock);
3443 if (cfs_b->quota == RUNTIME_INF)
3444 amount = min_amount;
3446 start_cfs_bandwidth(cfs_b);
3448 if (cfs_b->runtime > 0) {
3449 amount = min(cfs_b->runtime, min_amount);
3450 cfs_b->runtime -= amount;
3454 expires = cfs_b->runtime_expires;
3455 raw_spin_unlock(&cfs_b->lock);
3457 cfs_rq->runtime_remaining += amount;
3459 * we may have advanced our local expiration to account for allowed
3460 * spread between our sched_clock and the one on which runtime was
3463 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3464 cfs_rq->runtime_expires = expires;
3466 return cfs_rq->runtime_remaining > 0;
3470 * Note: This depends on the synchronization provided by sched_clock and the
3471 * fact that rq->clock snapshots this value.
3473 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3475 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3477 /* if the deadline is ahead of our clock, nothing to do */
3478 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3481 if (cfs_rq->runtime_remaining < 0)
3485 * If the local deadline has passed we have to consider the
3486 * possibility that our sched_clock is 'fast' and the global deadline
3487 * has not truly expired.
3489 * Fortunately we can check determine whether this the case by checking
3490 * whether the global deadline has advanced. It is valid to compare
3491 * cfs_b->runtime_expires without any locks since we only care about
3492 * exact equality, so a partial write will still work.
3495 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3496 /* extend local deadline, drift is bounded above by 2 ticks */
3497 cfs_rq->runtime_expires += TICK_NSEC;
3499 /* global deadline is ahead, expiration has passed */
3500 cfs_rq->runtime_remaining = 0;
3504 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3506 /* dock delta_exec before expiring quota (as it could span periods) */
3507 cfs_rq->runtime_remaining -= delta_exec;
3508 expire_cfs_rq_runtime(cfs_rq);
3510 if (likely(cfs_rq->runtime_remaining > 0))
3514 * if we're unable to extend our runtime we resched so that the active
3515 * hierarchy can be throttled
3517 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3518 resched_curr(rq_of(cfs_rq));
3521 static __always_inline
3522 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3524 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3527 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3530 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3532 return cfs_bandwidth_used() && cfs_rq->throttled;
3535 /* check whether cfs_rq, or any parent, is throttled */
3536 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3538 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3542 * Ensure that neither of the group entities corresponding to src_cpu or
3543 * dest_cpu are members of a throttled hierarchy when performing group
3544 * load-balance operations.
3546 static inline int throttled_lb_pair(struct task_group *tg,
3547 int src_cpu, int dest_cpu)
3549 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3551 src_cfs_rq = tg->cfs_rq[src_cpu];
3552 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3554 return throttled_hierarchy(src_cfs_rq) ||
3555 throttled_hierarchy(dest_cfs_rq);
3558 /* updated child weight may affect parent so we have to do this bottom up */
3559 static int tg_unthrottle_up(struct task_group *tg, void *data)
3561 struct rq *rq = data;
3562 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3564 cfs_rq->throttle_count--;
3566 if (!cfs_rq->throttle_count) {
3567 /* adjust cfs_rq_clock_task() */
3568 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3569 cfs_rq->throttled_clock_task;
3576 static int tg_throttle_down(struct task_group *tg, void *data)
3578 struct rq *rq = data;
3579 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3581 /* group is entering throttled state, stop time */
3582 if (!cfs_rq->throttle_count)
3583 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3584 cfs_rq->throttle_count++;
3589 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3591 struct rq *rq = rq_of(cfs_rq);
3592 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3593 struct sched_entity *se;
3594 long task_delta, dequeue = 1;
3597 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3599 /* freeze hierarchy runnable averages while throttled */
3601 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3604 task_delta = cfs_rq->h_nr_running;
3605 for_each_sched_entity(se) {
3606 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3607 /* throttled entity or throttle-on-deactivate */
3612 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3613 qcfs_rq->h_nr_running -= task_delta;
3615 if (qcfs_rq->load.weight)
3620 sub_nr_running(rq, task_delta);
3622 cfs_rq->throttled = 1;
3623 cfs_rq->throttled_clock = rq_clock(rq);
3624 raw_spin_lock(&cfs_b->lock);
3625 empty = list_empty(&cfs_b->throttled_cfs_rq);
3628 * Add to the _head_ of the list, so that an already-started
3629 * distribute_cfs_runtime will not see us
3631 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3634 * If we're the first throttled task, make sure the bandwidth
3638 start_cfs_bandwidth(cfs_b);
3640 raw_spin_unlock(&cfs_b->lock);
3643 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3645 struct rq *rq = rq_of(cfs_rq);
3646 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3647 struct sched_entity *se;
3651 se = cfs_rq->tg->se[cpu_of(rq)];
3653 cfs_rq->throttled = 0;
3655 update_rq_clock(rq);
3657 raw_spin_lock(&cfs_b->lock);
3658 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3659 list_del_rcu(&cfs_rq->throttled_list);
3660 raw_spin_unlock(&cfs_b->lock);
3662 /* update hierarchical throttle state */
3663 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3665 if (!cfs_rq->load.weight)
3668 task_delta = cfs_rq->h_nr_running;
3669 for_each_sched_entity(se) {
3673 cfs_rq = cfs_rq_of(se);
3675 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3676 cfs_rq->h_nr_running += task_delta;
3678 if (cfs_rq_throttled(cfs_rq))
3683 add_nr_running(rq, task_delta);
3685 /* determine whether we need to wake up potentially idle cpu */
3686 if (rq->curr == rq->idle && rq->cfs.nr_running)
3690 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3691 u64 remaining, u64 expires)
3693 struct cfs_rq *cfs_rq;
3695 u64 starting_runtime = remaining;
3698 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3700 struct rq *rq = rq_of(cfs_rq);
3702 raw_spin_lock(&rq->lock);
3703 if (!cfs_rq_throttled(cfs_rq))
3706 runtime = -cfs_rq->runtime_remaining + 1;
3707 if (runtime > remaining)
3708 runtime = remaining;
3709 remaining -= runtime;
3711 cfs_rq->runtime_remaining += runtime;
3712 cfs_rq->runtime_expires = expires;
3714 /* we check whether we're throttled above */
3715 if (cfs_rq->runtime_remaining > 0)
3716 unthrottle_cfs_rq(cfs_rq);
3719 raw_spin_unlock(&rq->lock);
3726 return starting_runtime - remaining;
3730 * Responsible for refilling a task_group's bandwidth and unthrottling its
3731 * cfs_rqs as appropriate. If there has been no activity within the last
3732 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3733 * used to track this state.
3735 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3737 u64 runtime, runtime_expires;
3740 /* no need to continue the timer with no bandwidth constraint */
3741 if (cfs_b->quota == RUNTIME_INF)
3742 goto out_deactivate;
3744 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3745 cfs_b->nr_periods += overrun;
3748 * idle depends on !throttled (for the case of a large deficit), and if
3749 * we're going inactive then everything else can be deferred
3751 if (cfs_b->idle && !throttled)
3752 goto out_deactivate;
3754 __refill_cfs_bandwidth_runtime(cfs_b);
3757 /* mark as potentially idle for the upcoming period */
3762 /* account preceding periods in which throttling occurred */
3763 cfs_b->nr_throttled += overrun;
3765 runtime_expires = cfs_b->runtime_expires;
3768 * This check is repeated as we are holding onto the new bandwidth while
3769 * we unthrottle. This can potentially race with an unthrottled group
3770 * trying to acquire new bandwidth from the global pool. This can result
3771 * in us over-using our runtime if it is all used during this loop, but
3772 * only by limited amounts in that extreme case.
3774 while (throttled && cfs_b->runtime > 0) {
3775 runtime = cfs_b->runtime;
3776 raw_spin_unlock(&cfs_b->lock);
3777 /* we can't nest cfs_b->lock while distributing bandwidth */
3778 runtime = distribute_cfs_runtime(cfs_b, runtime,
3780 raw_spin_lock(&cfs_b->lock);
3782 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3784 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3788 * While we are ensured activity in the period following an
3789 * unthrottle, this also covers the case in which the new bandwidth is
3790 * insufficient to cover the existing bandwidth deficit. (Forcing the
3791 * timer to remain active while there are any throttled entities.)
3801 /* a cfs_rq won't donate quota below this amount */
3802 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3803 /* minimum remaining period time to redistribute slack quota */
3804 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3805 /* how long we wait to gather additional slack before distributing */
3806 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3809 * Are we near the end of the current quota period?
3811 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3812 * hrtimer base being cleared by hrtimer_start. In the case of
3813 * migrate_hrtimers, base is never cleared, so we are fine.
3815 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3817 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3820 /* if the call-back is running a quota refresh is already occurring */
3821 if (hrtimer_callback_running(refresh_timer))
3824 /* is a quota refresh about to occur? */
3825 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3826 if (remaining < min_expire)
3832 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3834 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3836 /* if there's a quota refresh soon don't bother with slack */
3837 if (runtime_refresh_within(cfs_b, min_left))
3840 hrtimer_start(&cfs_b->slack_timer,
3841 ns_to_ktime(cfs_bandwidth_slack_period),
3845 /* we know any runtime found here is valid as update_curr() precedes return */
3846 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3848 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3849 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3851 if (slack_runtime <= 0)
3854 raw_spin_lock(&cfs_b->lock);
3855 if (cfs_b->quota != RUNTIME_INF &&
3856 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3857 cfs_b->runtime += slack_runtime;
3859 /* we are under rq->lock, defer unthrottling using a timer */
3860 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3861 !list_empty(&cfs_b->throttled_cfs_rq))
3862 start_cfs_slack_bandwidth(cfs_b);
3864 raw_spin_unlock(&cfs_b->lock);
3866 /* even if it's not valid for return we don't want to try again */
3867 cfs_rq->runtime_remaining -= slack_runtime;
3870 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3872 if (!cfs_bandwidth_used())
3875 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3878 __return_cfs_rq_runtime(cfs_rq);
3882 * This is done with a timer (instead of inline with bandwidth return) since
3883 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3885 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3887 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3890 /* confirm we're still not at a refresh boundary */
3891 raw_spin_lock(&cfs_b->lock);
3892 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3893 raw_spin_unlock(&cfs_b->lock);
3897 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3898 runtime = cfs_b->runtime;
3900 expires = cfs_b->runtime_expires;
3901 raw_spin_unlock(&cfs_b->lock);
3906 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3908 raw_spin_lock(&cfs_b->lock);
3909 if (expires == cfs_b->runtime_expires)
3910 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3911 raw_spin_unlock(&cfs_b->lock);
3915 * When a group wakes up we want to make sure that its quota is not already
3916 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3917 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3919 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3921 if (!cfs_bandwidth_used())
3924 /* an active group must be handled by the update_curr()->put() path */
3925 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3928 /* ensure the group is not already throttled */
3929 if (cfs_rq_throttled(cfs_rq))
3932 /* update runtime allocation */
3933 account_cfs_rq_runtime(cfs_rq, 0);
3934 if (cfs_rq->runtime_remaining <= 0)
3935 throttle_cfs_rq(cfs_rq);
3938 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3939 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3941 if (!cfs_bandwidth_used())
3944 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3948 * it's possible for a throttled entity to be forced into a running
3949 * state (e.g. set_curr_task), in this case we're finished.
3951 if (cfs_rq_throttled(cfs_rq))
3954 throttle_cfs_rq(cfs_rq);
3958 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3960 struct cfs_bandwidth *cfs_b =
3961 container_of(timer, struct cfs_bandwidth, slack_timer);
3963 do_sched_cfs_slack_timer(cfs_b);
3965 return HRTIMER_NORESTART;
3968 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3970 struct cfs_bandwidth *cfs_b =
3971 container_of(timer, struct cfs_bandwidth, period_timer);
3975 raw_spin_lock(&cfs_b->lock);
3977 overrun = hrtimer_forward_now(timer, cfs_b->period);
3981 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3984 cfs_b->period_active = 0;
3985 raw_spin_unlock(&cfs_b->lock);
3987 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3990 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3992 raw_spin_lock_init(&cfs_b->lock);
3994 cfs_b->quota = RUNTIME_INF;
3995 cfs_b->period = ns_to_ktime(default_cfs_period());
3997 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3998 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3999 cfs_b->period_timer.function = sched_cfs_period_timer;
4000 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4001 cfs_b->slack_timer.function = sched_cfs_slack_timer;
4004 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4006 cfs_rq->runtime_enabled = 0;
4007 INIT_LIST_HEAD(&cfs_rq->throttled_list);
4010 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4012 lockdep_assert_held(&cfs_b->lock);
4014 if (!cfs_b->period_active) {
4015 cfs_b->period_active = 1;
4016 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4017 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4021 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4023 /* init_cfs_bandwidth() was not called */
4024 if (!cfs_b->throttled_cfs_rq.next)
4027 hrtimer_cancel(&cfs_b->period_timer);
4028 hrtimer_cancel(&cfs_b->slack_timer);
4031 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4033 struct cfs_rq *cfs_rq;
4035 for_each_leaf_cfs_rq(rq, cfs_rq) {
4036 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4038 raw_spin_lock(&cfs_b->lock);
4039 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4040 raw_spin_unlock(&cfs_b->lock);
4044 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4046 struct cfs_rq *cfs_rq;
4048 for_each_leaf_cfs_rq(rq, cfs_rq) {
4049 if (!cfs_rq->runtime_enabled)
4053 * clock_task is not advancing so we just need to make sure
4054 * there's some valid quota amount
4056 cfs_rq->runtime_remaining = 1;
4058 * Offline rq is schedulable till cpu is completely disabled
4059 * in take_cpu_down(), so we prevent new cfs throttling here.
4061 cfs_rq->runtime_enabled = 0;
4063 if (cfs_rq_throttled(cfs_rq))
4064 unthrottle_cfs_rq(cfs_rq);
4068 #else /* CONFIG_CFS_BANDWIDTH */
4069 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4071 return rq_clock_task(rq_of(cfs_rq));
4074 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4075 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4076 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4077 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4079 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4084 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4089 static inline int throttled_lb_pair(struct task_group *tg,
4090 int src_cpu, int dest_cpu)
4095 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4097 #ifdef CONFIG_FAIR_GROUP_SCHED
4098 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4101 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4105 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4106 static inline void update_runtime_enabled(struct rq *rq) {}
4107 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4109 #endif /* CONFIG_CFS_BANDWIDTH */
4111 /**************************************************
4112 * CFS operations on tasks:
4115 #ifdef CONFIG_SCHED_HRTICK
4116 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4118 struct sched_entity *se = &p->se;
4119 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4121 WARN_ON(task_rq(p) != rq);
4123 if (cfs_rq->nr_running > 1) {
4124 u64 slice = sched_slice(cfs_rq, se);
4125 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4126 s64 delta = slice - ran;
4133 hrtick_start(rq, delta);
4138 * called from enqueue/dequeue and updates the hrtick when the
4139 * current task is from our class and nr_running is low enough
4142 static void hrtick_update(struct rq *rq)
4144 struct task_struct *curr = rq->curr;
4146 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4149 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4150 hrtick_start_fair(rq, curr);
4152 #else /* !CONFIG_SCHED_HRTICK */
4154 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4158 static inline void hrtick_update(struct rq *rq)
4164 * The enqueue_task method is called before nr_running is
4165 * increased. Here we update the fair scheduling stats and
4166 * then put the task into the rbtree:
4169 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4171 struct cfs_rq *cfs_rq;
4172 struct sched_entity *se = &p->se;
4174 for_each_sched_entity(se) {
4177 cfs_rq = cfs_rq_of(se);
4178 enqueue_entity(cfs_rq, se, flags);
4181 * end evaluation on encountering a throttled cfs_rq
4183 * note: in the case of encountering a throttled cfs_rq we will
4184 * post the final h_nr_running increment below.
4186 if (cfs_rq_throttled(cfs_rq))
4188 cfs_rq->h_nr_running++;
4190 flags = ENQUEUE_WAKEUP;
4193 for_each_sched_entity(se) {
4194 cfs_rq = cfs_rq_of(se);
4195 cfs_rq->h_nr_running++;
4197 if (cfs_rq_throttled(cfs_rq))
4200 update_load_avg(se, 1);
4201 update_cfs_shares(cfs_rq);
4205 add_nr_running(rq, 1);
4210 static void set_next_buddy(struct sched_entity *se);
4213 * The dequeue_task method is called before nr_running is
4214 * decreased. We remove the task from the rbtree and
4215 * update the fair scheduling stats:
4217 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4219 struct cfs_rq *cfs_rq;
4220 struct sched_entity *se = &p->se;
4221 int task_sleep = flags & DEQUEUE_SLEEP;
4223 for_each_sched_entity(se) {
4224 cfs_rq = cfs_rq_of(se);
4225 dequeue_entity(cfs_rq, se, flags);
4228 * end evaluation on encountering a throttled cfs_rq
4230 * note: in the case of encountering a throttled cfs_rq we will
4231 * post the final h_nr_running decrement below.
4233 if (cfs_rq_throttled(cfs_rq))
4235 cfs_rq->h_nr_running--;
4237 /* Don't dequeue parent if it has other entities besides us */
4238 if (cfs_rq->load.weight) {
4240 * Bias pick_next to pick a task from this cfs_rq, as
4241 * p is sleeping when it is within its sched_slice.
4243 if (task_sleep && parent_entity(se))
4244 set_next_buddy(parent_entity(se));
4246 /* avoid re-evaluating load for this entity */
4247 se = parent_entity(se);
4250 flags |= DEQUEUE_SLEEP;
4253 for_each_sched_entity(se) {
4254 cfs_rq = cfs_rq_of(se);
4255 cfs_rq->h_nr_running--;
4257 if (cfs_rq_throttled(cfs_rq))
4260 update_load_avg(se, 1);
4261 update_cfs_shares(cfs_rq);
4265 sub_nr_running(rq, 1);
4273 * per rq 'load' arrray crap; XXX kill this.
4277 * The exact cpuload at various idx values, calculated at every tick would be
4278 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4280 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4281 * on nth tick when cpu may be busy, then we have:
4282 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4283 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4285 * decay_load_missed() below does efficient calculation of
4286 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4287 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4289 * The calculation is approximated on a 128 point scale.
4290 * degrade_zero_ticks is the number of ticks after which load at any
4291 * particular idx is approximated to be zero.
4292 * degrade_factor is a precomputed table, a row for each load idx.
4293 * Each column corresponds to degradation factor for a power of two ticks,
4294 * based on 128 point scale.
4296 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4297 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4299 * With this power of 2 load factors, we can degrade the load n times
4300 * by looking at 1 bits in n and doing as many mult/shift instead of
4301 * n mult/shifts needed by the exact degradation.
4303 #define DEGRADE_SHIFT 7
4304 static const unsigned char
4305 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4306 static const unsigned char
4307 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4308 {0, 0, 0, 0, 0, 0, 0, 0},
4309 {64, 32, 8, 0, 0, 0, 0, 0},
4310 {96, 72, 40, 12, 1, 0, 0},
4311 {112, 98, 75, 43, 15, 1, 0},
4312 {120, 112, 98, 76, 45, 16, 2} };
4315 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4316 * would be when CPU is idle and so we just decay the old load without
4317 * adding any new load.
4319 static unsigned long
4320 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4324 if (!missed_updates)
4327 if (missed_updates >= degrade_zero_ticks[idx])
4331 return load >> missed_updates;
4333 while (missed_updates) {
4334 if (missed_updates % 2)
4335 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4337 missed_updates >>= 1;
4344 * Update rq->cpu_load[] statistics. This function is usually called every
4345 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4346 * every tick. We fix it up based on jiffies.
4348 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4349 unsigned long pending_updates)
4353 this_rq->nr_load_updates++;
4355 /* Update our load: */
4356 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4357 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4358 unsigned long old_load, new_load;
4360 /* scale is effectively 1 << i now, and >> i divides by scale */
4362 old_load = this_rq->cpu_load[i];
4363 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4364 new_load = this_load;
4366 * Round up the averaging division if load is increasing. This
4367 * prevents us from getting stuck on 9 if the load is 10, for
4370 if (new_load > old_load)
4371 new_load += scale - 1;
4373 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4376 sched_avg_update(this_rq);
4379 /* Used instead of source_load when we know the type == 0 */
4380 static unsigned long weighted_cpuload(const int cpu)
4382 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4385 #ifdef CONFIG_NO_HZ_COMMON
4387 * There is no sane way to deal with nohz on smp when using jiffies because the
4388 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4389 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4391 * Therefore we cannot use the delta approach from the regular tick since that
4392 * would seriously skew the load calculation. However we'll make do for those
4393 * updates happening while idle (nohz_idle_balance) or coming out of idle
4394 * (tick_nohz_idle_exit).
4396 * This means we might still be one tick off for nohz periods.
4400 * Called from nohz_idle_balance() to update the load ratings before doing the
4403 static void update_idle_cpu_load(struct rq *this_rq)
4405 unsigned long curr_jiffies = READ_ONCE(jiffies);
4406 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4407 unsigned long pending_updates;
4410 * bail if there's load or we're actually up-to-date.
4412 if (load || curr_jiffies == this_rq->last_load_update_tick)
4415 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4416 this_rq->last_load_update_tick = curr_jiffies;
4418 __update_cpu_load(this_rq, load, pending_updates);
4422 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4424 void update_cpu_load_nohz(void)
4426 struct rq *this_rq = this_rq();
4427 unsigned long curr_jiffies = READ_ONCE(jiffies);
4428 unsigned long pending_updates;
4430 if (curr_jiffies == this_rq->last_load_update_tick)
4433 raw_spin_lock(&this_rq->lock);
4434 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4435 if (pending_updates) {
4436 this_rq->last_load_update_tick = curr_jiffies;
4438 * We were idle, this means load 0, the current load might be
4439 * !0 due to remote wakeups and the sort.
4441 __update_cpu_load(this_rq, 0, pending_updates);
4443 raw_spin_unlock(&this_rq->lock);
4445 #endif /* CONFIG_NO_HZ */
4448 * Called from scheduler_tick()
4450 void update_cpu_load_active(struct rq *this_rq)
4452 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4454 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4456 this_rq->last_load_update_tick = jiffies;
4457 __update_cpu_load(this_rq, load, 1);
4461 * Return a low guess at the load of a migration-source cpu weighted
4462 * according to the scheduling class and "nice" value.
4464 * We want to under-estimate the load of migration sources, to
4465 * balance conservatively.
4467 static unsigned long source_load(int cpu, int type)
4469 struct rq *rq = cpu_rq(cpu);
4470 unsigned long total = weighted_cpuload(cpu);
4472 if (type == 0 || !sched_feat(LB_BIAS))
4475 return min(rq->cpu_load[type-1], total);
4479 * Return a high guess at the load of a migration-target cpu weighted
4480 * according to the scheduling class and "nice" value.
4482 static unsigned long target_load(int cpu, int type)
4484 struct rq *rq = cpu_rq(cpu);
4485 unsigned long total = weighted_cpuload(cpu);
4487 if (type == 0 || !sched_feat(LB_BIAS))
4490 return max(rq->cpu_load[type-1], total);
4493 static unsigned long capacity_of(int cpu)
4495 return cpu_rq(cpu)->cpu_capacity;
4498 static unsigned long capacity_orig_of(int cpu)
4500 return cpu_rq(cpu)->cpu_capacity_orig;
4503 static unsigned long cpu_avg_load_per_task(int cpu)
4505 struct rq *rq = cpu_rq(cpu);
4506 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4507 unsigned long load_avg = weighted_cpuload(cpu);
4510 return load_avg / nr_running;
4515 static void record_wakee(struct task_struct *p)
4518 * Rough decay (wiping) for cost saving, don't worry
4519 * about the boundary, really active task won't care
4522 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4523 current->wakee_flips >>= 1;
4524 current->wakee_flip_decay_ts = jiffies;
4527 if (current->last_wakee != p) {
4528 current->last_wakee = p;
4529 current->wakee_flips++;
4533 static void task_waking_fair(struct task_struct *p)
4535 struct sched_entity *se = &p->se;
4536 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4539 #ifndef CONFIG_64BIT
4540 u64 min_vruntime_copy;
4543 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4545 min_vruntime = cfs_rq->min_vruntime;
4546 } while (min_vruntime != min_vruntime_copy);
4548 min_vruntime = cfs_rq->min_vruntime;
4551 se->vruntime -= min_vruntime;
4555 #ifdef CONFIG_FAIR_GROUP_SCHED
4557 * effective_load() calculates the load change as seen from the root_task_group
4559 * Adding load to a group doesn't make a group heavier, but can cause movement
4560 * of group shares between cpus. Assuming the shares were perfectly aligned one
4561 * can calculate the shift in shares.
4563 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4564 * on this @cpu and results in a total addition (subtraction) of @wg to the
4565 * total group weight.
4567 * Given a runqueue weight distribution (rw_i) we can compute a shares
4568 * distribution (s_i) using:
4570 * s_i = rw_i / \Sum rw_j (1)
4572 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4573 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4574 * shares distribution (s_i):
4576 * rw_i = { 2, 4, 1, 0 }
4577 * s_i = { 2/7, 4/7, 1/7, 0 }
4579 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4580 * task used to run on and the CPU the waker is running on), we need to
4581 * compute the effect of waking a task on either CPU and, in case of a sync
4582 * wakeup, compute the effect of the current task going to sleep.
4584 * So for a change of @wl to the local @cpu with an overall group weight change
4585 * of @wl we can compute the new shares distribution (s'_i) using:
4587 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4589 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4590 * differences in waking a task to CPU 0. The additional task changes the
4591 * weight and shares distributions like:
4593 * rw'_i = { 3, 4, 1, 0 }
4594 * s'_i = { 3/8, 4/8, 1/8, 0 }
4596 * We can then compute the difference in effective weight by using:
4598 * dw_i = S * (s'_i - s_i) (3)
4600 * Where 'S' is the group weight as seen by its parent.
4602 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4603 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4604 * 4/7) times the weight of the group.
4606 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4608 struct sched_entity *se = tg->se[cpu];
4610 if (!tg->parent) /* the trivial, non-cgroup case */
4613 for_each_sched_entity(se) {
4614 struct cfs_rq *cfs_rq = se->my_q;
4615 long W, w = cfs_rq_load_avg(cfs_rq);
4620 * W = @wg + \Sum rw_j
4622 W = wg + atomic_long_read(&tg->load_avg);
4624 /* Ensure \Sum rw_j >= rw_i */
4625 W -= cfs_rq->tg_load_avg_contrib;
4634 * wl = S * s'_i; see (2)
4637 wl = (w * (long)tg->shares) / W;
4642 * Per the above, wl is the new se->load.weight value; since
4643 * those are clipped to [MIN_SHARES, ...) do so now. See
4644 * calc_cfs_shares().
4646 if (wl < MIN_SHARES)
4650 * wl = dw_i = S * (s'_i - s_i); see (3)
4652 wl -= se->avg.load_avg;
4655 * Recursively apply this logic to all parent groups to compute
4656 * the final effective load change on the root group. Since
4657 * only the @tg group gets extra weight, all parent groups can
4658 * only redistribute existing shares. @wl is the shift in shares
4659 * resulting from this level per the above.
4668 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4676 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4677 * A waker of many should wake a different task than the one last awakened
4678 * at a frequency roughly N times higher than one of its wakees. In order
4679 * to determine whether we should let the load spread vs consolodating to
4680 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4681 * partner, and a factor of lls_size higher frequency in the other. With
4682 * both conditions met, we can be relatively sure that the relationship is
4683 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4684 * being client/server, worker/dispatcher, interrupt source or whatever is
4685 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4687 static int wake_wide(struct task_struct *p)
4689 unsigned int master = current->wakee_flips;
4690 unsigned int slave = p->wakee_flips;
4691 int factor = this_cpu_read(sd_llc_size);
4694 swap(master, slave);
4695 if (slave < factor || master < slave * factor)
4700 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4702 s64 this_load, load;
4703 s64 this_eff_load, prev_eff_load;
4704 int idx, this_cpu, prev_cpu;
4705 struct task_group *tg;
4706 unsigned long weight;
4710 this_cpu = smp_processor_id();
4711 prev_cpu = task_cpu(p);
4712 load = source_load(prev_cpu, idx);
4713 this_load = target_load(this_cpu, idx);
4716 * If sync wakeup then subtract the (maximum possible)
4717 * effect of the currently running task from the load
4718 * of the current CPU:
4721 tg = task_group(current);
4722 weight = current->se.avg.load_avg;
4724 this_load += effective_load(tg, this_cpu, -weight, -weight);
4725 load += effective_load(tg, prev_cpu, 0, -weight);
4729 weight = p->se.avg.load_avg;
4732 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4733 * due to the sync cause above having dropped this_load to 0, we'll
4734 * always have an imbalance, but there's really nothing you can do
4735 * about that, so that's good too.
4737 * Otherwise check if either cpus are near enough in load to allow this
4738 * task to be woken on this_cpu.
4740 this_eff_load = 100;
4741 this_eff_load *= capacity_of(prev_cpu);
4743 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4744 prev_eff_load *= capacity_of(this_cpu);
4746 if (this_load > 0) {
4747 this_eff_load *= this_load +
4748 effective_load(tg, this_cpu, weight, weight);
4750 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4753 balanced = this_eff_load <= prev_eff_load;
4755 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4760 schedstat_inc(sd, ttwu_move_affine);
4761 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4766 static inline unsigned long task_util(struct task_struct *p)
4768 return p->se.avg.util_avg;
4771 static unsigned int capacity_margin = 1280; /* ~20% margin */
4773 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
4775 unsigned long capacity = capacity_of(cpu);
4777 util += task_util(p);
4779 return (capacity * 1024) > (util * capacity_margin);
4782 static inline bool task_fits_max(struct task_struct *p, int cpu)
4784 unsigned long capacity = capacity_of(cpu);
4785 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity;
4787 if (capacity == max_capacity)
4790 if (capacity * capacity_margin > max_capacity * 1024)
4793 return __task_fits(p, cpu, 0);
4796 static int cpu_util(int cpu);
4798 static inline bool task_fits_spare(struct task_struct *p, int cpu)
4800 return __task_fits(p, cpu, cpu_util(cpu));
4803 static bool cpu_overutilized(int cpu)
4805 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
4809 * find_idlest_group finds and returns the least busy CPU group within the
4812 static struct sched_group *
4813 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4814 int this_cpu, int sd_flag)
4816 struct sched_group *idlest = NULL, *group = sd->groups;
4817 struct sched_group *fit_group = NULL, *spare_group = NULL;
4818 unsigned long min_load = ULONG_MAX, this_load = 0;
4819 unsigned long fit_capacity = ULONG_MAX;
4820 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
4821 int load_idx = sd->forkexec_idx;
4822 int imbalance = 100 + (sd->imbalance_pct-100)/2;
4824 if (sd_flag & SD_BALANCE_WAKE)
4825 load_idx = sd->wake_idx;
4828 unsigned long load, avg_load, spare_capacity;
4832 /* Skip over this group if it has no CPUs allowed */
4833 if (!cpumask_intersects(sched_group_cpus(group),
4834 tsk_cpus_allowed(p)))
4837 local_group = cpumask_test_cpu(this_cpu,
4838 sched_group_cpus(group));
4840 /* Tally up the load of all CPUs in the group */
4843 for_each_cpu(i, sched_group_cpus(group)) {
4844 /* Bias balancing toward cpus of our domain */
4846 load = source_load(i, load_idx);
4848 load = target_load(i, load_idx);
4853 * Look for most energy-efficient group that can fit
4854 * that can fit the task.
4856 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
4857 fit_capacity = capacity_of(i);
4862 * Look for group which has most spare capacity on a
4865 spare_capacity = capacity_of(i) - cpu_util(i);
4866 if (spare_capacity > max_spare_capacity) {
4867 max_spare_capacity = spare_capacity;
4868 spare_group = group;
4872 /* Adjust by relative CPU capacity of the group */
4873 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4876 this_load = avg_load;
4877 } else if (avg_load < min_load) {
4878 min_load = avg_load;
4881 } while (group = group->next, group != sd->groups);
4889 if (!idlest || 100*this_load < imbalance*min_load)
4895 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4898 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4900 unsigned long load, min_load = ULONG_MAX;
4901 unsigned int min_exit_latency = UINT_MAX;
4902 u64 latest_idle_timestamp = 0;
4903 int least_loaded_cpu = this_cpu;
4904 int shallowest_idle_cpu = -1;
4907 /* Traverse only the allowed CPUs */
4908 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4909 if (task_fits_spare(p, i)) {
4910 struct rq *rq = cpu_rq(i);
4911 struct cpuidle_state *idle = idle_get_state(rq);
4912 if (idle && idle->exit_latency < min_exit_latency) {
4914 * We give priority to a CPU whose idle state
4915 * has the smallest exit latency irrespective
4916 * of any idle timestamp.
4918 min_exit_latency = idle->exit_latency;
4919 latest_idle_timestamp = rq->idle_stamp;
4920 shallowest_idle_cpu = i;
4921 } else if (idle_cpu(i) &&
4922 (!idle || idle->exit_latency == min_exit_latency) &&
4923 rq->idle_stamp > latest_idle_timestamp) {
4925 * If equal or no active idle state, then
4926 * the most recently idled CPU might have
4929 latest_idle_timestamp = rq->idle_stamp;
4930 shallowest_idle_cpu = i;
4931 } else if (shallowest_idle_cpu == -1) {
4933 * If we haven't found an idle CPU yet
4934 * pick a non-idle one that can fit the task as
4937 shallowest_idle_cpu = i;
4939 } else if (shallowest_idle_cpu == -1) {
4940 load = weighted_cpuload(i);
4941 if (load < min_load || (load == min_load && i == this_cpu)) {
4943 least_loaded_cpu = i;
4948 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4952 * Try and locate an idle CPU in the sched_domain.
4954 static int select_idle_sibling(struct task_struct *p, int target)
4956 struct sched_domain *sd;
4957 struct sched_group *sg;
4958 int i = task_cpu(p);
4960 if (idle_cpu(target))
4964 * If the prevous cpu is cache affine and idle, don't be stupid.
4966 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4970 * Otherwise, iterate the domains and find an elegible idle cpu.
4972 sd = rcu_dereference(per_cpu(sd_llc, target));
4973 for_each_lower_domain(sd) {
4976 if (!cpumask_intersects(sched_group_cpus(sg),
4977 tsk_cpus_allowed(p)))
4980 for_each_cpu(i, sched_group_cpus(sg)) {
4981 if (i == target || !idle_cpu(i))
4985 target = cpumask_first_and(sched_group_cpus(sg),
4986 tsk_cpus_allowed(p));
4990 } while (sg != sd->groups);
4997 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4998 * tasks. The unit of the return value must be the one of capacity so we can
4999 * compare the utilization with the capacity of the CPU that is available for
5000 * CFS task (ie cpu_capacity).
5002 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5003 * recent utilization of currently non-runnable tasks on a CPU. It represents
5004 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5005 * capacity_orig is the cpu_capacity available at the highest frequency
5006 * (arch_scale_freq_capacity()).
5007 * The utilization of a CPU converges towards a sum equal to or less than the
5008 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5009 * the running time on this CPU scaled by capacity_curr.
5011 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5012 * higher than capacity_orig because of unfortunate rounding in
5013 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5014 * the average stabilizes with the new running time. We need to check that the
5015 * utilization stays within the range of [0..capacity_orig] and cap it if
5016 * necessary. Without utilization capping, a group could be seen as overloaded
5017 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5018 * available capacity. We allow utilization to overshoot capacity_curr (but not
5019 * capacity_orig) as it useful for predicting the capacity required after task
5020 * migrations (scheduler-driven DVFS).
5022 static int cpu_util(int cpu)
5024 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5025 unsigned long capacity = capacity_orig_of(cpu);
5027 return (util >= capacity) ? capacity : util;
5031 * select_task_rq_fair: Select target runqueue for the waking task in domains
5032 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5033 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5035 * Balances load by selecting the idlest cpu in the idlest group, or under
5036 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5038 * Returns the target cpu number.
5040 * preempt must be disabled.
5043 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5045 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5046 int cpu = smp_processor_id();
5047 int new_cpu = prev_cpu;
5048 int want_affine = 0;
5049 int sync = wake_flags & WF_SYNC;
5051 if (sd_flag & SD_BALANCE_WAKE)
5052 want_affine = !wake_wide(p) && task_fits_max(p, cpu) &&
5053 cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5056 for_each_domain(cpu, tmp) {
5057 if (!(tmp->flags & SD_LOAD_BALANCE))
5061 * If both cpu and prev_cpu are part of this domain,
5062 * cpu is a valid SD_WAKE_AFFINE target.
5064 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5065 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5070 if (tmp->flags & sd_flag)
5072 else if (!want_affine)
5077 sd = NULL; /* Prefer wake_affine over balance flags */
5078 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5083 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5084 new_cpu = select_idle_sibling(p, new_cpu);
5087 struct sched_group *group;
5090 if (!(sd->flags & sd_flag)) {
5095 group = find_idlest_group(sd, p, cpu, sd_flag);
5101 new_cpu = find_idlest_cpu(group, p, cpu);
5102 if (new_cpu == -1 || new_cpu == cpu) {
5103 /* Now try balancing at a lower domain level of cpu */
5108 /* Now try balancing at a lower domain level of new_cpu */
5110 weight = sd->span_weight;
5112 for_each_domain(cpu, tmp) {
5113 if (weight <= tmp->span_weight)
5115 if (tmp->flags & sd_flag)
5118 /* while loop will break here if sd == NULL */
5126 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5127 * cfs_rq_of(p) references at time of call are still valid and identify the
5128 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5129 * other assumptions, including the state of rq->lock, should be made.
5131 static void migrate_task_rq_fair(struct task_struct *p)
5134 * We are supposed to update the task to "current" time, then its up to date
5135 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5136 * what current time is, so simply throw away the out-of-date time. This
5137 * will result in the wakee task is less decayed, but giving the wakee more
5138 * load sounds not bad.
5140 remove_entity_load_avg(&p->se);
5142 /* Tell new CPU we are migrated */
5143 p->se.avg.last_update_time = 0;
5145 /* We have migrated, no longer consider this task hot */
5146 p->se.exec_start = 0;
5149 static void task_dead_fair(struct task_struct *p)
5151 remove_entity_load_avg(&p->se);
5153 #endif /* CONFIG_SMP */
5155 static unsigned long
5156 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5158 unsigned long gran = sysctl_sched_wakeup_granularity;
5161 * Since its curr running now, convert the gran from real-time
5162 * to virtual-time in his units.
5164 * By using 'se' instead of 'curr' we penalize light tasks, so
5165 * they get preempted easier. That is, if 'se' < 'curr' then
5166 * the resulting gran will be larger, therefore penalizing the
5167 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5168 * be smaller, again penalizing the lighter task.
5170 * This is especially important for buddies when the leftmost
5171 * task is higher priority than the buddy.
5173 return calc_delta_fair(gran, se);
5177 * Should 'se' preempt 'curr'.
5191 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5193 s64 gran, vdiff = curr->vruntime - se->vruntime;
5198 gran = wakeup_gran(curr, se);
5205 static void set_last_buddy(struct sched_entity *se)
5207 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5210 for_each_sched_entity(se)
5211 cfs_rq_of(se)->last = se;
5214 static void set_next_buddy(struct sched_entity *se)
5216 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5219 for_each_sched_entity(se)
5220 cfs_rq_of(se)->next = se;
5223 static void set_skip_buddy(struct sched_entity *se)
5225 for_each_sched_entity(se)
5226 cfs_rq_of(se)->skip = se;
5230 * Preempt the current task with a newly woken task if needed:
5232 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5234 struct task_struct *curr = rq->curr;
5235 struct sched_entity *se = &curr->se, *pse = &p->se;
5236 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5237 int scale = cfs_rq->nr_running >= sched_nr_latency;
5238 int next_buddy_marked = 0;
5240 if (unlikely(se == pse))
5244 * This is possible from callers such as attach_tasks(), in which we
5245 * unconditionally check_prempt_curr() after an enqueue (which may have
5246 * lead to a throttle). This both saves work and prevents false
5247 * next-buddy nomination below.
5249 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5252 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5253 set_next_buddy(pse);
5254 next_buddy_marked = 1;
5258 * We can come here with TIF_NEED_RESCHED already set from new task
5261 * Note: this also catches the edge-case of curr being in a throttled
5262 * group (e.g. via set_curr_task), since update_curr() (in the
5263 * enqueue of curr) will have resulted in resched being set. This
5264 * prevents us from potentially nominating it as a false LAST_BUDDY
5267 if (test_tsk_need_resched(curr))
5270 /* Idle tasks are by definition preempted by non-idle tasks. */
5271 if (unlikely(curr->policy == SCHED_IDLE) &&
5272 likely(p->policy != SCHED_IDLE))
5276 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5277 * is driven by the tick):
5279 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5282 find_matching_se(&se, &pse);
5283 update_curr(cfs_rq_of(se));
5285 if (wakeup_preempt_entity(se, pse) == 1) {
5287 * Bias pick_next to pick the sched entity that is
5288 * triggering this preemption.
5290 if (!next_buddy_marked)
5291 set_next_buddy(pse);
5300 * Only set the backward buddy when the current task is still
5301 * on the rq. This can happen when a wakeup gets interleaved
5302 * with schedule on the ->pre_schedule() or idle_balance()
5303 * point, either of which can * drop the rq lock.
5305 * Also, during early boot the idle thread is in the fair class,
5306 * for obvious reasons its a bad idea to schedule back to it.
5308 if (unlikely(!se->on_rq || curr == rq->idle))
5311 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5315 static struct task_struct *
5316 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5318 struct cfs_rq *cfs_rq = &rq->cfs;
5319 struct sched_entity *se;
5320 struct task_struct *p;
5324 #ifdef CONFIG_FAIR_GROUP_SCHED
5325 if (!cfs_rq->nr_running)
5328 if (prev->sched_class != &fair_sched_class)
5332 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5333 * likely that a next task is from the same cgroup as the current.
5335 * Therefore attempt to avoid putting and setting the entire cgroup
5336 * hierarchy, only change the part that actually changes.
5340 struct sched_entity *curr = cfs_rq->curr;
5343 * Since we got here without doing put_prev_entity() we also
5344 * have to consider cfs_rq->curr. If it is still a runnable
5345 * entity, update_curr() will update its vruntime, otherwise
5346 * forget we've ever seen it.
5350 update_curr(cfs_rq);
5355 * This call to check_cfs_rq_runtime() will do the
5356 * throttle and dequeue its entity in the parent(s).
5357 * Therefore the 'simple' nr_running test will indeed
5360 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5364 se = pick_next_entity(cfs_rq, curr);
5365 cfs_rq = group_cfs_rq(se);
5371 * Since we haven't yet done put_prev_entity and if the selected task
5372 * is a different task than we started out with, try and touch the
5373 * least amount of cfs_rqs.
5376 struct sched_entity *pse = &prev->se;
5378 while (!(cfs_rq = is_same_group(se, pse))) {
5379 int se_depth = se->depth;
5380 int pse_depth = pse->depth;
5382 if (se_depth <= pse_depth) {
5383 put_prev_entity(cfs_rq_of(pse), pse);
5384 pse = parent_entity(pse);
5386 if (se_depth >= pse_depth) {
5387 set_next_entity(cfs_rq_of(se), se);
5388 se = parent_entity(se);
5392 put_prev_entity(cfs_rq, pse);
5393 set_next_entity(cfs_rq, se);
5396 if (hrtick_enabled(rq))
5397 hrtick_start_fair(rq, p);
5404 if (!cfs_rq->nr_running)
5407 put_prev_task(rq, prev);
5410 se = pick_next_entity(cfs_rq, NULL);
5411 set_next_entity(cfs_rq, se);
5412 cfs_rq = group_cfs_rq(se);
5417 if (hrtick_enabled(rq))
5418 hrtick_start_fair(rq, p);
5424 * This is OK, because current is on_cpu, which avoids it being picked
5425 * for load-balance and preemption/IRQs are still disabled avoiding
5426 * further scheduler activity on it and we're being very careful to
5427 * re-start the picking loop.
5429 lockdep_unpin_lock(&rq->lock);
5430 new_tasks = idle_balance(rq);
5431 lockdep_pin_lock(&rq->lock);
5433 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5434 * possible for any higher priority task to appear. In that case we
5435 * must re-start the pick_next_entity() loop.
5447 * Account for a descheduled task:
5449 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5451 struct sched_entity *se = &prev->se;
5452 struct cfs_rq *cfs_rq;
5454 for_each_sched_entity(se) {
5455 cfs_rq = cfs_rq_of(se);
5456 put_prev_entity(cfs_rq, se);
5461 * sched_yield() is very simple
5463 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5465 static void yield_task_fair(struct rq *rq)
5467 struct task_struct *curr = rq->curr;
5468 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5469 struct sched_entity *se = &curr->se;
5472 * Are we the only task in the tree?
5474 if (unlikely(rq->nr_running == 1))
5477 clear_buddies(cfs_rq, se);
5479 if (curr->policy != SCHED_BATCH) {
5480 update_rq_clock(rq);
5482 * Update run-time statistics of the 'current'.
5484 update_curr(cfs_rq);
5486 * Tell update_rq_clock() that we've just updated,
5487 * so we don't do microscopic update in schedule()
5488 * and double the fastpath cost.
5490 rq_clock_skip_update(rq, true);
5496 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5498 struct sched_entity *se = &p->se;
5500 /* throttled hierarchies are not runnable */
5501 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5504 /* Tell the scheduler that we'd really like pse to run next. */
5507 yield_task_fair(rq);
5513 /**************************************************
5514 * Fair scheduling class load-balancing methods.
5518 * The purpose of load-balancing is to achieve the same basic fairness the
5519 * per-cpu scheduler provides, namely provide a proportional amount of compute
5520 * time to each task. This is expressed in the following equation:
5522 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5524 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5525 * W_i,0 is defined as:
5527 * W_i,0 = \Sum_j w_i,j (2)
5529 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5530 * is derived from the nice value as per prio_to_weight[].
5532 * The weight average is an exponential decay average of the instantaneous
5535 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5537 * C_i is the compute capacity of cpu i, typically it is the
5538 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5539 * can also include other factors [XXX].
5541 * To achieve this balance we define a measure of imbalance which follows
5542 * directly from (1):
5544 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5546 * We them move tasks around to minimize the imbalance. In the continuous
5547 * function space it is obvious this converges, in the discrete case we get
5548 * a few fun cases generally called infeasible weight scenarios.
5551 * - infeasible weights;
5552 * - local vs global optima in the discrete case. ]
5557 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5558 * for all i,j solution, we create a tree of cpus that follows the hardware
5559 * topology where each level pairs two lower groups (or better). This results
5560 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5561 * tree to only the first of the previous level and we decrease the frequency
5562 * of load-balance at each level inv. proportional to the number of cpus in
5568 * \Sum { --- * --- * 2^i } = O(n) (5)
5570 * `- size of each group
5571 * | | `- number of cpus doing load-balance
5573 * `- sum over all levels
5575 * Coupled with a limit on how many tasks we can migrate every balance pass,
5576 * this makes (5) the runtime complexity of the balancer.
5578 * An important property here is that each CPU is still (indirectly) connected
5579 * to every other cpu in at most O(log n) steps:
5581 * The adjacency matrix of the resulting graph is given by:
5584 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5587 * And you'll find that:
5589 * A^(log_2 n)_i,j != 0 for all i,j (7)
5591 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5592 * The task movement gives a factor of O(m), giving a convergence complexity
5595 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5600 * In order to avoid CPUs going idle while there's still work to do, new idle
5601 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5602 * tree itself instead of relying on other CPUs to bring it work.
5604 * This adds some complexity to both (5) and (8) but it reduces the total idle
5612 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5615 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5620 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5622 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5624 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5627 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5628 * rewrite all of this once again.]
5631 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5633 enum fbq_type { regular, remote, all };
5635 #define LBF_ALL_PINNED 0x01
5636 #define LBF_NEED_BREAK 0x02
5637 #define LBF_DST_PINNED 0x04
5638 #define LBF_SOME_PINNED 0x08
5641 struct sched_domain *sd;
5649 struct cpumask *dst_grpmask;
5651 enum cpu_idle_type idle;
5653 unsigned int src_grp_nr_running;
5654 /* The set of CPUs under consideration for load-balancing */
5655 struct cpumask *cpus;
5660 unsigned int loop_break;
5661 unsigned int loop_max;
5663 enum fbq_type fbq_type;
5664 struct list_head tasks;
5668 * Is this task likely cache-hot:
5670 static int task_hot(struct task_struct *p, struct lb_env *env)
5674 lockdep_assert_held(&env->src_rq->lock);
5676 if (p->sched_class != &fair_sched_class)
5679 if (unlikely(p->policy == SCHED_IDLE))
5683 * Buddy candidates are cache hot:
5685 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5686 (&p->se == cfs_rq_of(&p->se)->next ||
5687 &p->se == cfs_rq_of(&p->se)->last))
5690 if (sysctl_sched_migration_cost == -1)
5692 if (sysctl_sched_migration_cost == 0)
5695 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5697 return delta < (s64)sysctl_sched_migration_cost;
5700 #ifdef CONFIG_NUMA_BALANCING
5702 * Returns 1, if task migration degrades locality
5703 * Returns 0, if task migration improves locality i.e migration preferred.
5704 * Returns -1, if task migration is not affected by locality.
5706 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5708 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5709 unsigned long src_faults, dst_faults;
5710 int src_nid, dst_nid;
5712 if (!static_branch_likely(&sched_numa_balancing))
5715 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5718 src_nid = cpu_to_node(env->src_cpu);
5719 dst_nid = cpu_to_node(env->dst_cpu);
5721 if (src_nid == dst_nid)
5724 /* Migrating away from the preferred node is always bad. */
5725 if (src_nid == p->numa_preferred_nid) {
5726 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5732 /* Encourage migration to the preferred node. */
5733 if (dst_nid == p->numa_preferred_nid)
5737 src_faults = group_faults(p, src_nid);
5738 dst_faults = group_faults(p, dst_nid);
5740 src_faults = task_faults(p, src_nid);
5741 dst_faults = task_faults(p, dst_nid);
5744 return dst_faults < src_faults;
5748 static inline int migrate_degrades_locality(struct task_struct *p,
5756 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5759 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5763 lockdep_assert_held(&env->src_rq->lock);
5766 * We do not migrate tasks that are:
5767 * 1) throttled_lb_pair, or
5768 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5769 * 3) running (obviously), or
5770 * 4) are cache-hot on their current CPU.
5772 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5775 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5778 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5780 env->flags |= LBF_SOME_PINNED;
5783 * Remember if this task can be migrated to any other cpu in
5784 * our sched_group. We may want to revisit it if we couldn't
5785 * meet load balance goals by pulling other tasks on src_cpu.
5787 * Also avoid computing new_dst_cpu if we have already computed
5788 * one in current iteration.
5790 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5793 /* Prevent to re-select dst_cpu via env's cpus */
5794 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5795 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5796 env->flags |= LBF_DST_PINNED;
5797 env->new_dst_cpu = cpu;
5805 /* Record that we found atleast one task that could run on dst_cpu */
5806 env->flags &= ~LBF_ALL_PINNED;
5808 if (task_running(env->src_rq, p)) {
5809 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5814 * Aggressive migration if:
5815 * 1) destination numa is preferred
5816 * 2) task is cache cold, or
5817 * 3) too many balance attempts have failed.
5819 tsk_cache_hot = migrate_degrades_locality(p, env);
5820 if (tsk_cache_hot == -1)
5821 tsk_cache_hot = task_hot(p, env);
5823 if (tsk_cache_hot <= 0 ||
5824 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5825 if (tsk_cache_hot == 1) {
5826 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5827 schedstat_inc(p, se.statistics.nr_forced_migrations);
5832 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5837 * detach_task() -- detach the task for the migration specified in env
5839 static void detach_task(struct task_struct *p, struct lb_env *env)
5841 lockdep_assert_held(&env->src_rq->lock);
5843 deactivate_task(env->src_rq, p, 0);
5844 p->on_rq = TASK_ON_RQ_MIGRATING;
5845 set_task_cpu(p, env->dst_cpu);
5849 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5850 * part of active balancing operations within "domain".
5852 * Returns a task if successful and NULL otherwise.
5854 static struct task_struct *detach_one_task(struct lb_env *env)
5856 struct task_struct *p, *n;
5858 lockdep_assert_held(&env->src_rq->lock);
5860 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5861 if (!can_migrate_task(p, env))
5864 detach_task(p, env);
5867 * Right now, this is only the second place where
5868 * lb_gained[env->idle] is updated (other is detach_tasks)
5869 * so we can safely collect stats here rather than
5870 * inside detach_tasks().
5872 schedstat_inc(env->sd, lb_gained[env->idle]);
5878 static const unsigned int sched_nr_migrate_break = 32;
5881 * detach_tasks() -- tries to detach up to imbalance weighted load from
5882 * busiest_rq, as part of a balancing operation within domain "sd".
5884 * Returns number of detached tasks if successful and 0 otherwise.
5886 static int detach_tasks(struct lb_env *env)
5888 struct list_head *tasks = &env->src_rq->cfs_tasks;
5889 struct task_struct *p;
5893 lockdep_assert_held(&env->src_rq->lock);
5895 if (env->imbalance <= 0)
5898 while (!list_empty(tasks)) {
5900 * We don't want to steal all, otherwise we may be treated likewise,
5901 * which could at worst lead to a livelock crash.
5903 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
5906 p = list_first_entry(tasks, struct task_struct, se.group_node);
5909 /* We've more or less seen every task there is, call it quits */
5910 if (env->loop > env->loop_max)
5913 /* take a breather every nr_migrate tasks */
5914 if (env->loop > env->loop_break) {
5915 env->loop_break += sched_nr_migrate_break;
5916 env->flags |= LBF_NEED_BREAK;
5920 if (!can_migrate_task(p, env))
5923 load = task_h_load(p);
5925 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5928 if ((load / 2) > env->imbalance)
5931 detach_task(p, env);
5932 list_add(&p->se.group_node, &env->tasks);
5935 env->imbalance -= load;
5937 #ifdef CONFIG_PREEMPT
5939 * NEWIDLE balancing is a source of latency, so preemptible
5940 * kernels will stop after the first task is detached to minimize
5941 * the critical section.
5943 if (env->idle == CPU_NEWLY_IDLE)
5948 * We only want to steal up to the prescribed amount of
5951 if (env->imbalance <= 0)
5956 list_move_tail(&p->se.group_node, tasks);
5960 * Right now, this is one of only two places we collect this stat
5961 * so we can safely collect detach_one_task() stats here rather
5962 * than inside detach_one_task().
5964 schedstat_add(env->sd, lb_gained[env->idle], detached);
5970 * attach_task() -- attach the task detached by detach_task() to its new rq.
5972 static void attach_task(struct rq *rq, struct task_struct *p)
5974 lockdep_assert_held(&rq->lock);
5976 BUG_ON(task_rq(p) != rq);
5977 p->on_rq = TASK_ON_RQ_QUEUED;
5978 activate_task(rq, p, 0);
5979 check_preempt_curr(rq, p, 0);
5983 * attach_one_task() -- attaches the task returned from detach_one_task() to
5986 static void attach_one_task(struct rq *rq, struct task_struct *p)
5988 raw_spin_lock(&rq->lock);
5990 raw_spin_unlock(&rq->lock);
5994 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5997 static void attach_tasks(struct lb_env *env)
5999 struct list_head *tasks = &env->tasks;
6000 struct task_struct *p;
6002 raw_spin_lock(&env->dst_rq->lock);
6004 while (!list_empty(tasks)) {
6005 p = list_first_entry(tasks, struct task_struct, se.group_node);
6006 list_del_init(&p->se.group_node);
6008 attach_task(env->dst_rq, p);
6011 raw_spin_unlock(&env->dst_rq->lock);
6014 #ifdef CONFIG_FAIR_GROUP_SCHED
6015 static void update_blocked_averages(int cpu)
6017 struct rq *rq = cpu_rq(cpu);
6018 struct cfs_rq *cfs_rq;
6019 unsigned long flags;
6021 raw_spin_lock_irqsave(&rq->lock, flags);
6022 update_rq_clock(rq);
6025 * Iterates the task_group tree in a bottom up fashion, see
6026 * list_add_leaf_cfs_rq() for details.
6028 for_each_leaf_cfs_rq(rq, cfs_rq) {
6029 /* throttled entities do not contribute to load */
6030 if (throttled_hierarchy(cfs_rq))
6033 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6034 update_tg_load_avg(cfs_rq, 0);
6036 raw_spin_unlock_irqrestore(&rq->lock, flags);
6040 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6041 * This needs to be done in a top-down fashion because the load of a child
6042 * group is a fraction of its parents load.
6044 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6046 struct rq *rq = rq_of(cfs_rq);
6047 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6048 unsigned long now = jiffies;
6051 if (cfs_rq->last_h_load_update == now)
6054 cfs_rq->h_load_next = NULL;
6055 for_each_sched_entity(se) {
6056 cfs_rq = cfs_rq_of(se);
6057 cfs_rq->h_load_next = se;
6058 if (cfs_rq->last_h_load_update == now)
6063 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6064 cfs_rq->last_h_load_update = now;
6067 while ((se = cfs_rq->h_load_next) != NULL) {
6068 load = cfs_rq->h_load;
6069 load = div64_ul(load * se->avg.load_avg,
6070 cfs_rq_load_avg(cfs_rq) + 1);
6071 cfs_rq = group_cfs_rq(se);
6072 cfs_rq->h_load = load;
6073 cfs_rq->last_h_load_update = now;
6077 static unsigned long task_h_load(struct task_struct *p)
6079 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6081 update_cfs_rq_h_load(cfs_rq);
6082 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6083 cfs_rq_load_avg(cfs_rq) + 1);
6086 static inline void update_blocked_averages(int cpu)
6088 struct rq *rq = cpu_rq(cpu);
6089 struct cfs_rq *cfs_rq = &rq->cfs;
6090 unsigned long flags;
6092 raw_spin_lock_irqsave(&rq->lock, flags);
6093 update_rq_clock(rq);
6094 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6095 raw_spin_unlock_irqrestore(&rq->lock, flags);
6098 static unsigned long task_h_load(struct task_struct *p)
6100 return p->se.avg.load_avg;
6104 /********** Helpers for find_busiest_group ************************/
6113 * sg_lb_stats - stats of a sched_group required for load_balancing
6115 struct sg_lb_stats {
6116 unsigned long avg_load; /*Avg load across the CPUs of the group */
6117 unsigned long group_load; /* Total load over the CPUs of the group */
6118 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6119 unsigned long load_per_task;
6120 unsigned long group_capacity;
6121 unsigned long group_util; /* Total utilization of the group */
6122 unsigned int sum_nr_running; /* Nr tasks running in the group */
6123 unsigned int idle_cpus;
6124 unsigned int group_weight;
6125 enum group_type group_type;
6126 int group_no_capacity;
6127 #ifdef CONFIG_NUMA_BALANCING
6128 unsigned int nr_numa_running;
6129 unsigned int nr_preferred_running;
6134 * sd_lb_stats - Structure to store the statistics of a sched_domain
6135 * during load balancing.
6137 struct sd_lb_stats {
6138 struct sched_group *busiest; /* Busiest group in this sd */
6139 struct sched_group *local; /* Local group in this sd */
6140 unsigned long total_load; /* Total load of all groups in sd */
6141 unsigned long total_capacity; /* Total capacity of all groups in sd */
6142 unsigned long avg_load; /* Average load across all groups in sd */
6144 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6145 struct sg_lb_stats local_stat; /* Statistics of the local group */
6148 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6151 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6152 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6153 * We must however clear busiest_stat::avg_load because
6154 * update_sd_pick_busiest() reads this before assignment.
6156 *sds = (struct sd_lb_stats){
6160 .total_capacity = 0UL,
6163 .sum_nr_running = 0,
6164 .group_type = group_other,
6170 * get_sd_load_idx - Obtain the load index for a given sched domain.
6171 * @sd: The sched_domain whose load_idx is to be obtained.
6172 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6174 * Return: The load index.
6176 static inline int get_sd_load_idx(struct sched_domain *sd,
6177 enum cpu_idle_type idle)
6183 load_idx = sd->busy_idx;
6186 case CPU_NEWLY_IDLE:
6187 load_idx = sd->newidle_idx;
6190 load_idx = sd->idle_idx;
6197 static unsigned long scale_rt_capacity(int cpu)
6199 struct rq *rq = cpu_rq(cpu);
6200 u64 total, used, age_stamp, avg;
6204 * Since we're reading these variables without serialization make sure
6205 * we read them once before doing sanity checks on them.
6207 age_stamp = READ_ONCE(rq->age_stamp);
6208 avg = READ_ONCE(rq->rt_avg);
6209 delta = __rq_clock_broken(rq) - age_stamp;
6211 if (unlikely(delta < 0))
6214 total = sched_avg_period() + delta;
6216 used = div_u64(avg, total);
6218 if (likely(used < SCHED_CAPACITY_SCALE))
6219 return SCHED_CAPACITY_SCALE - used;
6224 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6226 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6227 struct sched_group *sdg = sd->groups;
6229 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6231 capacity *= scale_rt_capacity(cpu);
6232 capacity >>= SCHED_CAPACITY_SHIFT;
6237 cpu_rq(cpu)->cpu_capacity = capacity;
6238 sdg->sgc->capacity = capacity;
6241 void update_group_capacity(struct sched_domain *sd, int cpu)
6243 struct sched_domain *child = sd->child;
6244 struct sched_group *group, *sdg = sd->groups;
6245 unsigned long capacity;
6246 unsigned long interval;
6248 interval = msecs_to_jiffies(sd->balance_interval);
6249 interval = clamp(interval, 1UL, max_load_balance_interval);
6250 sdg->sgc->next_update = jiffies + interval;
6253 update_cpu_capacity(sd, cpu);
6259 if (child->flags & SD_OVERLAP) {
6261 * SD_OVERLAP domains cannot assume that child groups
6262 * span the current group.
6265 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6266 struct sched_group_capacity *sgc;
6267 struct rq *rq = cpu_rq(cpu);
6270 * build_sched_domains() -> init_sched_groups_capacity()
6271 * gets here before we've attached the domains to the
6274 * Use capacity_of(), which is set irrespective of domains
6275 * in update_cpu_capacity().
6277 * This avoids capacity from being 0 and
6278 * causing divide-by-zero issues on boot.
6280 if (unlikely(!rq->sd)) {
6281 capacity += capacity_of(cpu);
6285 sgc = rq->sd->groups->sgc;
6286 capacity += sgc->capacity;
6290 * !SD_OVERLAP domains can assume that child groups
6291 * span the current group.
6294 group = child->groups;
6296 capacity += group->sgc->capacity;
6297 group = group->next;
6298 } while (group != child->groups);
6301 sdg->sgc->capacity = capacity;
6305 * Check whether the capacity of the rq has been noticeably reduced by side
6306 * activity. The imbalance_pct is used for the threshold.
6307 * Return true is the capacity is reduced
6310 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6312 return ((rq->cpu_capacity * sd->imbalance_pct) <
6313 (rq->cpu_capacity_orig * 100));
6317 * Group imbalance indicates (and tries to solve) the problem where balancing
6318 * groups is inadequate due to tsk_cpus_allowed() constraints.
6320 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6321 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6324 * { 0 1 2 3 } { 4 5 6 7 }
6327 * If we were to balance group-wise we'd place two tasks in the first group and
6328 * two tasks in the second group. Clearly this is undesired as it will overload
6329 * cpu 3 and leave one of the cpus in the second group unused.
6331 * The current solution to this issue is detecting the skew in the first group
6332 * by noticing the lower domain failed to reach balance and had difficulty
6333 * moving tasks due to affinity constraints.
6335 * When this is so detected; this group becomes a candidate for busiest; see
6336 * update_sd_pick_busiest(). And calculate_imbalance() and
6337 * find_busiest_group() avoid some of the usual balance conditions to allow it
6338 * to create an effective group imbalance.
6340 * This is a somewhat tricky proposition since the next run might not find the
6341 * group imbalance and decide the groups need to be balanced again. A most
6342 * subtle and fragile situation.
6345 static inline int sg_imbalanced(struct sched_group *group)
6347 return group->sgc->imbalance;
6351 * group_has_capacity returns true if the group has spare capacity that could
6352 * be used by some tasks.
6353 * We consider that a group has spare capacity if the * number of task is
6354 * smaller than the number of CPUs or if the utilization is lower than the
6355 * available capacity for CFS tasks.
6356 * For the latter, we use a threshold to stabilize the state, to take into
6357 * account the variance of the tasks' load and to return true if the available
6358 * capacity in meaningful for the load balancer.
6359 * As an example, an available capacity of 1% can appear but it doesn't make
6360 * any benefit for the load balance.
6363 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6365 if (sgs->sum_nr_running < sgs->group_weight)
6368 if ((sgs->group_capacity * 100) >
6369 (sgs->group_util * env->sd->imbalance_pct))
6376 * group_is_overloaded returns true if the group has more tasks than it can
6378 * group_is_overloaded is not equals to !group_has_capacity because a group
6379 * with the exact right number of tasks, has no more spare capacity but is not
6380 * overloaded so both group_has_capacity and group_is_overloaded return
6384 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6386 if (sgs->sum_nr_running <= sgs->group_weight)
6389 if ((sgs->group_capacity * 100) <
6390 (sgs->group_util * env->sd->imbalance_pct))
6397 group_type group_classify(struct sched_group *group,
6398 struct sg_lb_stats *sgs)
6400 if (sgs->group_no_capacity)
6401 return group_overloaded;
6403 if (sg_imbalanced(group))
6404 return group_imbalanced;
6410 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6411 * @env: The load balancing environment.
6412 * @group: sched_group whose statistics are to be updated.
6413 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6414 * @local_group: Does group contain this_cpu.
6415 * @sgs: variable to hold the statistics for this group.
6416 * @overload: Indicate more than one runnable task for any CPU.
6418 static inline void update_sg_lb_stats(struct lb_env *env,
6419 struct sched_group *group, int load_idx,
6420 int local_group, struct sg_lb_stats *sgs,
6426 memset(sgs, 0, sizeof(*sgs));
6428 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6429 struct rq *rq = cpu_rq(i);
6431 /* Bias balancing toward cpus of our domain */
6433 load = target_load(i, load_idx);
6435 load = source_load(i, load_idx);
6437 sgs->group_load += load;
6438 sgs->group_util += cpu_util(i);
6439 sgs->sum_nr_running += rq->cfs.h_nr_running;
6441 if (rq->nr_running > 1)
6444 #ifdef CONFIG_NUMA_BALANCING
6445 sgs->nr_numa_running += rq->nr_numa_running;
6446 sgs->nr_preferred_running += rq->nr_preferred_running;
6448 sgs->sum_weighted_load += weighted_cpuload(i);
6453 /* Adjust by relative CPU capacity of the group */
6454 sgs->group_capacity = group->sgc->capacity;
6455 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6457 if (sgs->sum_nr_running)
6458 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6460 sgs->group_weight = group->group_weight;
6462 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6463 sgs->group_type = group_classify(group, sgs);
6467 * update_sd_pick_busiest - return 1 on busiest group
6468 * @env: The load balancing environment.
6469 * @sds: sched_domain statistics
6470 * @sg: sched_group candidate to be checked for being the busiest
6471 * @sgs: sched_group statistics
6473 * Determine if @sg is a busier group than the previously selected
6476 * Return: %true if @sg is a busier group than the previously selected
6477 * busiest group. %false otherwise.
6479 static bool update_sd_pick_busiest(struct lb_env *env,
6480 struct sd_lb_stats *sds,
6481 struct sched_group *sg,
6482 struct sg_lb_stats *sgs)
6484 struct sg_lb_stats *busiest = &sds->busiest_stat;
6486 if (sgs->group_type > busiest->group_type)
6489 if (sgs->group_type < busiest->group_type)
6492 if (sgs->avg_load <= busiest->avg_load)
6495 /* This is the busiest node in its class. */
6496 if (!(env->sd->flags & SD_ASYM_PACKING))
6500 * ASYM_PACKING needs to move all the work to the lowest
6501 * numbered CPUs in the group, therefore mark all groups
6502 * higher than ourself as busy.
6504 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6508 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6515 #ifdef CONFIG_NUMA_BALANCING
6516 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6518 if (sgs->sum_nr_running > sgs->nr_numa_running)
6520 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6525 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6527 if (rq->nr_running > rq->nr_numa_running)
6529 if (rq->nr_running > rq->nr_preferred_running)
6534 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6539 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6543 #endif /* CONFIG_NUMA_BALANCING */
6546 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6547 * @env: The load balancing environment.
6548 * @sds: variable to hold the statistics for this sched_domain.
6550 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6552 struct sched_domain *child = env->sd->child;
6553 struct sched_group *sg = env->sd->groups;
6554 struct sg_lb_stats tmp_sgs;
6555 int load_idx, prefer_sibling = 0;
6556 bool overload = false;
6558 if (child && child->flags & SD_PREFER_SIBLING)
6561 load_idx = get_sd_load_idx(env->sd, env->idle);
6564 struct sg_lb_stats *sgs = &tmp_sgs;
6567 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6570 sgs = &sds->local_stat;
6572 if (env->idle != CPU_NEWLY_IDLE ||
6573 time_after_eq(jiffies, sg->sgc->next_update))
6574 update_group_capacity(env->sd, env->dst_cpu);
6577 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6584 * In case the child domain prefers tasks go to siblings
6585 * first, lower the sg capacity so that we'll try
6586 * and move all the excess tasks away. We lower the capacity
6587 * of a group only if the local group has the capacity to fit
6588 * these excess tasks. The extra check prevents the case where
6589 * you always pull from the heaviest group when it is already
6590 * under-utilized (possible with a large weight task outweighs
6591 * the tasks on the system).
6593 if (prefer_sibling && sds->local &&
6594 group_has_capacity(env, &sds->local_stat) &&
6595 (sgs->sum_nr_running > 1)) {
6596 sgs->group_no_capacity = 1;
6597 sgs->group_type = group_classify(sg, sgs);
6600 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6602 sds->busiest_stat = *sgs;
6606 /* Now, start updating sd_lb_stats */
6607 sds->total_load += sgs->group_load;
6608 sds->total_capacity += sgs->group_capacity;
6611 } while (sg != env->sd->groups);
6613 if (env->sd->flags & SD_NUMA)
6614 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6616 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
6618 if (!env->sd->parent) {
6619 /* update overload indicator if we are at root domain */
6620 if (env->dst_rq->rd->overload != overload)
6621 env->dst_rq->rd->overload = overload;
6627 * check_asym_packing - Check to see if the group is packed into the
6630 * This is primarily intended to used at the sibling level. Some
6631 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6632 * case of POWER7, it can move to lower SMT modes only when higher
6633 * threads are idle. When in lower SMT modes, the threads will
6634 * perform better since they share less core resources. Hence when we
6635 * have idle threads, we want them to be the higher ones.
6637 * This packing function is run on idle threads. It checks to see if
6638 * the busiest CPU in this domain (core in the P7 case) has a higher
6639 * CPU number than the packing function is being run on. Here we are
6640 * assuming lower CPU number will be equivalent to lower a SMT thread
6643 * Return: 1 when packing is required and a task should be moved to
6644 * this CPU. The amount of the imbalance is returned in *imbalance.
6646 * @env: The load balancing environment.
6647 * @sds: Statistics of the sched_domain which is to be packed
6649 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6653 if (!(env->sd->flags & SD_ASYM_PACKING))
6659 busiest_cpu = group_first_cpu(sds->busiest);
6660 if (env->dst_cpu > busiest_cpu)
6663 env->imbalance = DIV_ROUND_CLOSEST(
6664 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6665 SCHED_CAPACITY_SCALE);
6671 * fix_small_imbalance - Calculate the minor imbalance that exists
6672 * amongst the groups of a sched_domain, during
6674 * @env: The load balancing environment.
6675 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6678 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6680 unsigned long tmp, capa_now = 0, capa_move = 0;
6681 unsigned int imbn = 2;
6682 unsigned long scaled_busy_load_per_task;
6683 struct sg_lb_stats *local, *busiest;
6685 local = &sds->local_stat;
6686 busiest = &sds->busiest_stat;
6688 if (!local->sum_nr_running)
6689 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6690 else if (busiest->load_per_task > local->load_per_task)
6693 scaled_busy_load_per_task =
6694 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6695 busiest->group_capacity;
6697 if (busiest->avg_load + scaled_busy_load_per_task >=
6698 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6699 env->imbalance = busiest->load_per_task;
6704 * OK, we don't have enough imbalance to justify moving tasks,
6705 * however we may be able to increase total CPU capacity used by
6709 capa_now += busiest->group_capacity *
6710 min(busiest->load_per_task, busiest->avg_load);
6711 capa_now += local->group_capacity *
6712 min(local->load_per_task, local->avg_load);
6713 capa_now /= SCHED_CAPACITY_SCALE;
6715 /* Amount of load we'd subtract */
6716 if (busiest->avg_load > scaled_busy_load_per_task) {
6717 capa_move += busiest->group_capacity *
6718 min(busiest->load_per_task,
6719 busiest->avg_load - scaled_busy_load_per_task);
6722 /* Amount of load we'd add */
6723 if (busiest->avg_load * busiest->group_capacity <
6724 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6725 tmp = (busiest->avg_load * busiest->group_capacity) /
6726 local->group_capacity;
6728 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6729 local->group_capacity;
6731 capa_move += local->group_capacity *
6732 min(local->load_per_task, local->avg_load + tmp);
6733 capa_move /= SCHED_CAPACITY_SCALE;
6735 /* Move if we gain throughput */
6736 if (capa_move > capa_now)
6737 env->imbalance = busiest->load_per_task;
6741 * calculate_imbalance - Calculate the amount of imbalance present within the
6742 * groups of a given sched_domain during load balance.
6743 * @env: load balance environment
6744 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6746 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6748 unsigned long max_pull, load_above_capacity = ~0UL;
6749 struct sg_lb_stats *local, *busiest;
6751 local = &sds->local_stat;
6752 busiest = &sds->busiest_stat;
6754 if (busiest->group_type == group_imbalanced) {
6756 * In the group_imb case we cannot rely on group-wide averages
6757 * to ensure cpu-load equilibrium, look at wider averages. XXX
6759 busiest->load_per_task =
6760 min(busiest->load_per_task, sds->avg_load);
6764 * In the presence of smp nice balancing, certain scenarios can have
6765 * max load less than avg load(as we skip the groups at or below
6766 * its cpu_capacity, while calculating max_load..)
6768 if (busiest->avg_load <= sds->avg_load ||
6769 local->avg_load >= sds->avg_load) {
6771 return fix_small_imbalance(env, sds);
6775 * If there aren't any idle cpus, avoid creating some.
6777 if (busiest->group_type == group_overloaded &&
6778 local->group_type == group_overloaded) {
6779 load_above_capacity = busiest->sum_nr_running *
6781 if (load_above_capacity > busiest->group_capacity)
6782 load_above_capacity -= busiest->group_capacity;
6784 load_above_capacity = ~0UL;
6788 * We're trying to get all the cpus to the average_load, so we don't
6789 * want to push ourselves above the average load, nor do we wish to
6790 * reduce the max loaded cpu below the average load. At the same time,
6791 * we also don't want to reduce the group load below the group capacity
6792 * (so that we can implement power-savings policies etc). Thus we look
6793 * for the minimum possible imbalance.
6795 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6797 /* How much load to actually move to equalise the imbalance */
6798 env->imbalance = min(
6799 max_pull * busiest->group_capacity,
6800 (sds->avg_load - local->avg_load) * local->group_capacity
6801 ) / SCHED_CAPACITY_SCALE;
6804 * if *imbalance is less than the average load per runnable task
6805 * there is no guarantee that any tasks will be moved so we'll have
6806 * a think about bumping its value to force at least one task to be
6809 if (env->imbalance < busiest->load_per_task)
6810 return fix_small_imbalance(env, sds);
6813 /******* find_busiest_group() helpers end here *********************/
6816 * find_busiest_group - Returns the busiest group within the sched_domain
6817 * if there is an imbalance. If there isn't an imbalance, and
6818 * the user has opted for power-savings, it returns a group whose
6819 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6820 * such a group exists.
6822 * Also calculates the amount of weighted load which should be moved
6823 * to restore balance.
6825 * @env: The load balancing environment.
6827 * Return: - The busiest group if imbalance exists.
6828 * - If no imbalance and user has opted for power-savings balance,
6829 * return the least loaded group whose CPUs can be
6830 * put to idle by rebalancing its tasks onto our group.
6832 static struct sched_group *find_busiest_group(struct lb_env *env)
6834 struct sg_lb_stats *local, *busiest;
6835 struct sd_lb_stats sds;
6837 init_sd_lb_stats(&sds);
6840 * Compute the various statistics relavent for load balancing at
6843 update_sd_lb_stats(env, &sds);
6844 local = &sds.local_stat;
6845 busiest = &sds.busiest_stat;
6847 /* ASYM feature bypasses nice load balance check */
6848 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6849 check_asym_packing(env, &sds))
6852 /* There is no busy sibling group to pull tasks from */
6853 if (!sds.busiest || busiest->sum_nr_running == 0)
6856 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6857 / sds.total_capacity;
6860 * If the busiest group is imbalanced the below checks don't
6861 * work because they assume all things are equal, which typically
6862 * isn't true due to cpus_allowed constraints and the like.
6864 if (busiest->group_type == group_imbalanced)
6867 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6868 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6869 busiest->group_no_capacity)
6873 * If the local group is busier than the selected busiest group
6874 * don't try and pull any tasks.
6876 if (local->avg_load >= busiest->avg_load)
6880 * Don't pull any tasks if this group is already above the domain
6883 if (local->avg_load >= sds.avg_load)
6886 if (env->idle == CPU_IDLE) {
6888 * This cpu is idle. If the busiest group is not overloaded
6889 * and there is no imbalance between this and busiest group
6890 * wrt idle cpus, it is balanced. The imbalance becomes
6891 * significant if the diff is greater than 1 otherwise we
6892 * might end up to just move the imbalance on another group
6894 if ((busiest->group_type != group_overloaded) &&
6895 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6899 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6900 * imbalance_pct to be conservative.
6902 if (100 * busiest->avg_load <=
6903 env->sd->imbalance_pct * local->avg_load)
6908 /* Looks like there is an imbalance. Compute it */
6909 calculate_imbalance(env, &sds);
6918 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6920 static struct rq *find_busiest_queue(struct lb_env *env,
6921 struct sched_group *group)
6923 struct rq *busiest = NULL, *rq;
6924 unsigned long busiest_load = 0, busiest_capacity = 1;
6927 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6928 unsigned long capacity, wl;
6932 rt = fbq_classify_rq(rq);
6935 * We classify groups/runqueues into three groups:
6936 * - regular: there are !numa tasks
6937 * - remote: there are numa tasks that run on the 'wrong' node
6938 * - all: there is no distinction
6940 * In order to avoid migrating ideally placed numa tasks,
6941 * ignore those when there's better options.
6943 * If we ignore the actual busiest queue to migrate another
6944 * task, the next balance pass can still reduce the busiest
6945 * queue by moving tasks around inside the node.
6947 * If we cannot move enough load due to this classification
6948 * the next pass will adjust the group classification and
6949 * allow migration of more tasks.
6951 * Both cases only affect the total convergence complexity.
6953 if (rt > env->fbq_type)
6956 capacity = capacity_of(i);
6958 wl = weighted_cpuload(i);
6961 * When comparing with imbalance, use weighted_cpuload()
6962 * which is not scaled with the cpu capacity.
6965 if (rq->nr_running == 1 && wl > env->imbalance &&
6966 !check_cpu_capacity(rq, env->sd))
6970 * For the load comparisons with the other cpu's, consider
6971 * the weighted_cpuload() scaled with the cpu capacity, so
6972 * that the load can be moved away from the cpu that is
6973 * potentially running at a lower capacity.
6975 * Thus we're looking for max(wl_i / capacity_i), crosswise
6976 * multiplication to rid ourselves of the division works out
6977 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
6978 * our previous maximum.
6980 if (wl * busiest_capacity > busiest_load * capacity) {
6982 busiest_capacity = capacity;
6991 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6992 * so long as it is large enough.
6994 #define MAX_PINNED_INTERVAL 512
6996 /* Working cpumask for load_balance and load_balance_newidle. */
6997 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6999 static int need_active_balance(struct lb_env *env)
7001 struct sched_domain *sd = env->sd;
7003 if (env->idle == CPU_NEWLY_IDLE) {
7006 * ASYM_PACKING needs to force migrate tasks from busy but
7007 * higher numbered CPUs in order to pack all tasks in the
7008 * lowest numbered CPUs.
7010 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7015 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7016 * It's worth migrating the task if the src_cpu's capacity is reduced
7017 * because of other sched_class or IRQs if more capacity stays
7018 * available on dst_cpu.
7020 if ((env->idle != CPU_NOT_IDLE) &&
7021 (env->src_rq->cfs.h_nr_running == 1)) {
7022 if ((check_cpu_capacity(env->src_rq, sd)) &&
7023 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7027 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7028 env->src_rq->cfs.h_nr_running == 1 &&
7029 cpu_overutilized(env->src_cpu) &&
7030 !cpu_overutilized(env->dst_cpu)) {
7034 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7037 static int active_load_balance_cpu_stop(void *data);
7039 static int should_we_balance(struct lb_env *env)
7041 struct sched_group *sg = env->sd->groups;
7042 struct cpumask *sg_cpus, *sg_mask;
7043 int cpu, balance_cpu = -1;
7046 * In the newly idle case, we will allow all the cpu's
7047 * to do the newly idle load balance.
7049 if (env->idle == CPU_NEWLY_IDLE)
7052 sg_cpus = sched_group_cpus(sg);
7053 sg_mask = sched_group_mask(sg);
7054 /* Try to find first idle cpu */
7055 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7056 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7063 if (balance_cpu == -1)
7064 balance_cpu = group_balance_cpu(sg);
7067 * First idle cpu or the first cpu(busiest) in this sched group
7068 * is eligible for doing load balancing at this and above domains.
7070 return balance_cpu == env->dst_cpu;
7074 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7075 * tasks if there is an imbalance.
7077 static int load_balance(int this_cpu, struct rq *this_rq,
7078 struct sched_domain *sd, enum cpu_idle_type idle,
7079 int *continue_balancing)
7081 int ld_moved, cur_ld_moved, active_balance = 0;
7082 struct sched_domain *sd_parent = sd->parent;
7083 struct sched_group *group;
7085 unsigned long flags;
7086 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7088 struct lb_env env = {
7090 .dst_cpu = this_cpu,
7092 .dst_grpmask = sched_group_cpus(sd->groups),
7094 .loop_break = sched_nr_migrate_break,
7097 .tasks = LIST_HEAD_INIT(env.tasks),
7101 * For NEWLY_IDLE load_balancing, we don't need to consider
7102 * other cpus in our group
7104 if (idle == CPU_NEWLY_IDLE)
7105 env.dst_grpmask = NULL;
7107 cpumask_copy(cpus, cpu_active_mask);
7109 schedstat_inc(sd, lb_count[idle]);
7112 if (!should_we_balance(&env)) {
7113 *continue_balancing = 0;
7117 group = find_busiest_group(&env);
7119 schedstat_inc(sd, lb_nobusyg[idle]);
7123 busiest = find_busiest_queue(&env, group);
7125 schedstat_inc(sd, lb_nobusyq[idle]);
7129 BUG_ON(busiest == env.dst_rq);
7131 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7133 env.src_cpu = busiest->cpu;
7134 env.src_rq = busiest;
7137 if (busiest->nr_running > 1) {
7139 * Attempt to move tasks. If find_busiest_group has found
7140 * an imbalance but busiest->nr_running <= 1, the group is
7141 * still unbalanced. ld_moved simply stays zero, so it is
7142 * correctly treated as an imbalance.
7144 env.flags |= LBF_ALL_PINNED;
7145 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7148 raw_spin_lock_irqsave(&busiest->lock, flags);
7151 * cur_ld_moved - load moved in current iteration
7152 * ld_moved - cumulative load moved across iterations
7154 cur_ld_moved = detach_tasks(&env);
7157 * We've detached some tasks from busiest_rq. Every
7158 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7159 * unlock busiest->lock, and we are able to be sure
7160 * that nobody can manipulate the tasks in parallel.
7161 * See task_rq_lock() family for the details.
7164 raw_spin_unlock(&busiest->lock);
7168 ld_moved += cur_ld_moved;
7171 local_irq_restore(flags);
7173 if (env.flags & LBF_NEED_BREAK) {
7174 env.flags &= ~LBF_NEED_BREAK;
7179 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7180 * us and move them to an alternate dst_cpu in our sched_group
7181 * where they can run. The upper limit on how many times we
7182 * iterate on same src_cpu is dependent on number of cpus in our
7185 * This changes load balance semantics a bit on who can move
7186 * load to a given_cpu. In addition to the given_cpu itself
7187 * (or a ilb_cpu acting on its behalf where given_cpu is
7188 * nohz-idle), we now have balance_cpu in a position to move
7189 * load to given_cpu. In rare situations, this may cause
7190 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7191 * _independently_ and at _same_ time to move some load to
7192 * given_cpu) causing exceess load to be moved to given_cpu.
7193 * This however should not happen so much in practice and
7194 * moreover subsequent load balance cycles should correct the
7195 * excess load moved.
7197 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7199 /* Prevent to re-select dst_cpu via env's cpus */
7200 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7202 env.dst_rq = cpu_rq(env.new_dst_cpu);
7203 env.dst_cpu = env.new_dst_cpu;
7204 env.flags &= ~LBF_DST_PINNED;
7206 env.loop_break = sched_nr_migrate_break;
7209 * Go back to "more_balance" rather than "redo" since we
7210 * need to continue with same src_cpu.
7216 * We failed to reach balance because of affinity.
7219 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7221 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7222 *group_imbalance = 1;
7225 /* All tasks on this runqueue were pinned by CPU affinity */
7226 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7227 cpumask_clear_cpu(cpu_of(busiest), cpus);
7228 if (!cpumask_empty(cpus)) {
7230 env.loop_break = sched_nr_migrate_break;
7233 goto out_all_pinned;
7238 schedstat_inc(sd, lb_failed[idle]);
7240 * Increment the failure counter only on periodic balance.
7241 * We do not want newidle balance, which can be very
7242 * frequent, pollute the failure counter causing
7243 * excessive cache_hot migrations and active balances.
7245 if (idle != CPU_NEWLY_IDLE)
7246 if (env.src_grp_nr_running > 1)
7247 sd->nr_balance_failed++;
7249 if (need_active_balance(&env)) {
7250 raw_spin_lock_irqsave(&busiest->lock, flags);
7252 /* don't kick the active_load_balance_cpu_stop,
7253 * if the curr task on busiest cpu can't be
7256 if (!cpumask_test_cpu(this_cpu,
7257 tsk_cpus_allowed(busiest->curr))) {
7258 raw_spin_unlock_irqrestore(&busiest->lock,
7260 env.flags |= LBF_ALL_PINNED;
7261 goto out_one_pinned;
7265 * ->active_balance synchronizes accesses to
7266 * ->active_balance_work. Once set, it's cleared
7267 * only after active load balance is finished.
7269 if (!busiest->active_balance) {
7270 busiest->active_balance = 1;
7271 busiest->push_cpu = this_cpu;
7274 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7276 if (active_balance) {
7277 stop_one_cpu_nowait(cpu_of(busiest),
7278 active_load_balance_cpu_stop, busiest,
7279 &busiest->active_balance_work);
7283 * We've kicked active balancing, reset the failure
7286 sd->nr_balance_failed = sd->cache_nice_tries+1;
7289 sd->nr_balance_failed = 0;
7291 if (likely(!active_balance)) {
7292 /* We were unbalanced, so reset the balancing interval */
7293 sd->balance_interval = sd->min_interval;
7296 * If we've begun active balancing, start to back off. This
7297 * case may not be covered by the all_pinned logic if there
7298 * is only 1 task on the busy runqueue (because we don't call
7301 if (sd->balance_interval < sd->max_interval)
7302 sd->balance_interval *= 2;
7309 * We reach balance although we may have faced some affinity
7310 * constraints. Clear the imbalance flag if it was set.
7313 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7315 if (*group_imbalance)
7316 *group_imbalance = 0;
7321 * We reach balance because all tasks are pinned at this level so
7322 * we can't migrate them. Let the imbalance flag set so parent level
7323 * can try to migrate them.
7325 schedstat_inc(sd, lb_balanced[idle]);
7327 sd->nr_balance_failed = 0;
7330 /* tune up the balancing interval */
7331 if (((env.flags & LBF_ALL_PINNED) &&
7332 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7333 (sd->balance_interval < sd->max_interval))
7334 sd->balance_interval *= 2;
7341 static inline unsigned long
7342 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7344 unsigned long interval = sd->balance_interval;
7347 interval *= sd->busy_factor;
7349 /* scale ms to jiffies */
7350 interval = msecs_to_jiffies(interval);
7351 interval = clamp(interval, 1UL, max_load_balance_interval);
7357 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7359 unsigned long interval, next;
7361 interval = get_sd_balance_interval(sd, cpu_busy);
7362 next = sd->last_balance + interval;
7364 if (time_after(*next_balance, next))
7365 *next_balance = next;
7369 * idle_balance is called by schedule() if this_cpu is about to become
7370 * idle. Attempts to pull tasks from other CPUs.
7372 static int idle_balance(struct rq *this_rq)
7374 unsigned long next_balance = jiffies + HZ;
7375 int this_cpu = this_rq->cpu;
7376 struct sched_domain *sd;
7377 int pulled_task = 0;
7380 idle_enter_fair(this_rq);
7383 * We must set idle_stamp _before_ calling idle_balance(), such that we
7384 * measure the duration of idle_balance() as idle time.
7386 this_rq->idle_stamp = rq_clock(this_rq);
7388 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7389 !this_rq->rd->overload) {
7391 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7393 update_next_balance(sd, 0, &next_balance);
7399 raw_spin_unlock(&this_rq->lock);
7401 update_blocked_averages(this_cpu);
7403 for_each_domain(this_cpu, sd) {
7404 int continue_balancing = 1;
7405 u64 t0, domain_cost;
7407 if (!(sd->flags & SD_LOAD_BALANCE))
7410 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7411 update_next_balance(sd, 0, &next_balance);
7415 if (sd->flags & SD_BALANCE_NEWIDLE) {
7416 t0 = sched_clock_cpu(this_cpu);
7418 pulled_task = load_balance(this_cpu, this_rq,
7420 &continue_balancing);
7422 domain_cost = sched_clock_cpu(this_cpu) - t0;
7423 if (domain_cost > sd->max_newidle_lb_cost)
7424 sd->max_newidle_lb_cost = domain_cost;
7426 curr_cost += domain_cost;
7429 update_next_balance(sd, 0, &next_balance);
7432 * Stop searching for tasks to pull if there are
7433 * now runnable tasks on this rq.
7435 if (pulled_task || this_rq->nr_running > 0)
7440 raw_spin_lock(&this_rq->lock);
7442 if (curr_cost > this_rq->max_idle_balance_cost)
7443 this_rq->max_idle_balance_cost = curr_cost;
7446 * While browsing the domains, we released the rq lock, a task could
7447 * have been enqueued in the meantime. Since we're not going idle,
7448 * pretend we pulled a task.
7450 if (this_rq->cfs.h_nr_running && !pulled_task)
7454 /* Move the next balance forward */
7455 if (time_after(this_rq->next_balance, next_balance))
7456 this_rq->next_balance = next_balance;
7458 /* Is there a task of a high priority class? */
7459 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7463 idle_exit_fair(this_rq);
7464 this_rq->idle_stamp = 0;
7471 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7472 * running tasks off the busiest CPU onto idle CPUs. It requires at
7473 * least 1 task to be running on each physical CPU where possible, and
7474 * avoids physical / logical imbalances.
7476 static int active_load_balance_cpu_stop(void *data)
7478 struct rq *busiest_rq = data;
7479 int busiest_cpu = cpu_of(busiest_rq);
7480 int target_cpu = busiest_rq->push_cpu;
7481 struct rq *target_rq = cpu_rq(target_cpu);
7482 struct sched_domain *sd;
7483 struct task_struct *p = NULL;
7485 raw_spin_lock_irq(&busiest_rq->lock);
7487 /* make sure the requested cpu hasn't gone down in the meantime */
7488 if (unlikely(busiest_cpu != smp_processor_id() ||
7489 !busiest_rq->active_balance))
7492 /* Is there any task to move? */
7493 if (busiest_rq->nr_running <= 1)
7497 * This condition is "impossible", if it occurs
7498 * we need to fix it. Originally reported by
7499 * Bjorn Helgaas on a 128-cpu setup.
7501 BUG_ON(busiest_rq == target_rq);
7503 /* Search for an sd spanning us and the target CPU. */
7505 for_each_domain(target_cpu, sd) {
7506 if ((sd->flags & SD_LOAD_BALANCE) &&
7507 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7512 struct lb_env env = {
7514 .dst_cpu = target_cpu,
7515 .dst_rq = target_rq,
7516 .src_cpu = busiest_rq->cpu,
7517 .src_rq = busiest_rq,
7521 schedstat_inc(sd, alb_count);
7523 p = detach_one_task(&env);
7525 schedstat_inc(sd, alb_pushed);
7527 schedstat_inc(sd, alb_failed);
7531 busiest_rq->active_balance = 0;
7532 raw_spin_unlock(&busiest_rq->lock);
7535 attach_one_task(target_rq, p);
7542 static inline int on_null_domain(struct rq *rq)
7544 return unlikely(!rcu_dereference_sched(rq->sd));
7547 #ifdef CONFIG_NO_HZ_COMMON
7549 * idle load balancing details
7550 * - When one of the busy CPUs notice that there may be an idle rebalancing
7551 * needed, they will kick the idle load balancer, which then does idle
7552 * load balancing for all the idle CPUs.
7555 cpumask_var_t idle_cpus_mask;
7557 unsigned long next_balance; /* in jiffy units */
7558 } nohz ____cacheline_aligned;
7560 static inline int find_new_ilb(void)
7562 int ilb = cpumask_first(nohz.idle_cpus_mask);
7564 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7571 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7572 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7573 * CPU (if there is one).
7575 static void nohz_balancer_kick(void)
7579 nohz.next_balance++;
7581 ilb_cpu = find_new_ilb();
7583 if (ilb_cpu >= nr_cpu_ids)
7586 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7589 * Use smp_send_reschedule() instead of resched_cpu().
7590 * This way we generate a sched IPI on the target cpu which
7591 * is idle. And the softirq performing nohz idle load balance
7592 * will be run before returning from the IPI.
7594 smp_send_reschedule(ilb_cpu);
7598 static inline void nohz_balance_exit_idle(int cpu)
7600 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7602 * Completely isolated CPUs don't ever set, so we must test.
7604 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7605 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7606 atomic_dec(&nohz.nr_cpus);
7608 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7612 static inline void set_cpu_sd_state_busy(void)
7614 struct sched_domain *sd;
7615 int cpu = smp_processor_id();
7618 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7620 if (!sd || !sd->nohz_idle)
7624 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7629 void set_cpu_sd_state_idle(void)
7631 struct sched_domain *sd;
7632 int cpu = smp_processor_id();
7635 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7637 if (!sd || sd->nohz_idle)
7641 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7647 * This routine will record that the cpu is going idle with tick stopped.
7648 * This info will be used in performing idle load balancing in the future.
7650 void nohz_balance_enter_idle(int cpu)
7653 * If this cpu is going down, then nothing needs to be done.
7655 if (!cpu_active(cpu))
7658 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7662 * If we're a completely isolated CPU, we don't play.
7664 if (on_null_domain(cpu_rq(cpu)))
7667 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7668 atomic_inc(&nohz.nr_cpus);
7669 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7672 static int sched_ilb_notifier(struct notifier_block *nfb,
7673 unsigned long action, void *hcpu)
7675 switch (action & ~CPU_TASKS_FROZEN) {
7677 nohz_balance_exit_idle(smp_processor_id());
7685 static DEFINE_SPINLOCK(balancing);
7688 * Scale the max load_balance interval with the number of CPUs in the system.
7689 * This trades load-balance latency on larger machines for less cross talk.
7691 void update_max_interval(void)
7693 max_load_balance_interval = HZ*num_online_cpus()/10;
7697 * It checks each scheduling domain to see if it is due to be balanced,
7698 * and initiates a balancing operation if so.
7700 * Balancing parameters are set up in init_sched_domains.
7702 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7704 int continue_balancing = 1;
7706 unsigned long interval;
7707 struct sched_domain *sd;
7708 /* Earliest time when we have to do rebalance again */
7709 unsigned long next_balance = jiffies + 60*HZ;
7710 int update_next_balance = 0;
7711 int need_serialize, need_decay = 0;
7714 update_blocked_averages(cpu);
7717 for_each_domain(cpu, sd) {
7719 * Decay the newidle max times here because this is a regular
7720 * visit to all the domains. Decay ~1% per second.
7722 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7723 sd->max_newidle_lb_cost =
7724 (sd->max_newidle_lb_cost * 253) / 256;
7725 sd->next_decay_max_lb_cost = jiffies + HZ;
7728 max_cost += sd->max_newidle_lb_cost;
7730 if (!(sd->flags & SD_LOAD_BALANCE))
7734 * Stop the load balance at this level. There is another
7735 * CPU in our sched group which is doing load balancing more
7738 if (!continue_balancing) {
7744 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7746 need_serialize = sd->flags & SD_SERIALIZE;
7747 if (need_serialize) {
7748 if (!spin_trylock(&balancing))
7752 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7753 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7755 * The LBF_DST_PINNED logic could have changed
7756 * env->dst_cpu, so we can't know our idle
7757 * state even if we migrated tasks. Update it.
7759 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7761 sd->last_balance = jiffies;
7762 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7765 spin_unlock(&balancing);
7767 if (time_after(next_balance, sd->last_balance + interval)) {
7768 next_balance = sd->last_balance + interval;
7769 update_next_balance = 1;
7774 * Ensure the rq-wide value also decays but keep it at a
7775 * reasonable floor to avoid funnies with rq->avg_idle.
7777 rq->max_idle_balance_cost =
7778 max((u64)sysctl_sched_migration_cost, max_cost);
7783 * next_balance will be updated only when there is a need.
7784 * When the cpu is attached to null domain for ex, it will not be
7787 if (likely(update_next_balance)) {
7788 rq->next_balance = next_balance;
7790 #ifdef CONFIG_NO_HZ_COMMON
7792 * If this CPU has been elected to perform the nohz idle
7793 * balance. Other idle CPUs have already rebalanced with
7794 * nohz_idle_balance() and nohz.next_balance has been
7795 * updated accordingly. This CPU is now running the idle load
7796 * balance for itself and we need to update the
7797 * nohz.next_balance accordingly.
7799 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
7800 nohz.next_balance = rq->next_balance;
7805 #ifdef CONFIG_NO_HZ_COMMON
7807 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7808 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7810 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7812 int this_cpu = this_rq->cpu;
7815 /* Earliest time when we have to do rebalance again */
7816 unsigned long next_balance = jiffies + 60*HZ;
7817 int update_next_balance = 0;
7819 if (idle != CPU_IDLE ||
7820 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7823 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7824 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7828 * If this cpu gets work to do, stop the load balancing
7829 * work being done for other cpus. Next load
7830 * balancing owner will pick it up.
7835 rq = cpu_rq(balance_cpu);
7838 * If time for next balance is due,
7841 if (time_after_eq(jiffies, rq->next_balance)) {
7842 raw_spin_lock_irq(&rq->lock);
7843 update_rq_clock(rq);
7844 update_idle_cpu_load(rq);
7845 raw_spin_unlock_irq(&rq->lock);
7846 rebalance_domains(rq, CPU_IDLE);
7849 if (time_after(next_balance, rq->next_balance)) {
7850 next_balance = rq->next_balance;
7851 update_next_balance = 1;
7856 * next_balance will be updated only when there is a need.
7857 * When the CPU is attached to null domain for ex, it will not be
7860 if (likely(update_next_balance))
7861 nohz.next_balance = next_balance;
7863 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7867 * Current heuristic for kicking the idle load balancer in the presence
7868 * of an idle cpu in the system.
7869 * - This rq has more than one task.
7870 * - This rq has at least one CFS task and the capacity of the CPU is
7871 * significantly reduced because of RT tasks or IRQs.
7872 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
7873 * multiple busy cpu.
7874 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7875 * domain span are idle.
7877 static inline bool nohz_kick_needed(struct rq *rq)
7879 unsigned long now = jiffies;
7880 struct sched_domain *sd;
7881 struct sched_group_capacity *sgc;
7882 int nr_busy, cpu = rq->cpu;
7885 if (unlikely(rq->idle_balance))
7889 * We may be recently in ticked or tickless idle mode. At the first
7890 * busy tick after returning from idle, we will update the busy stats.
7892 set_cpu_sd_state_busy();
7893 nohz_balance_exit_idle(cpu);
7896 * None are in tickless mode and hence no need for NOHZ idle load
7899 if (likely(!atomic_read(&nohz.nr_cpus)))
7902 if (time_before(now, nohz.next_balance))
7905 if (rq->nr_running >= 2)
7909 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7911 sgc = sd->groups->sgc;
7912 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7921 sd = rcu_dereference(rq->sd);
7923 if ((rq->cfs.h_nr_running >= 1) &&
7924 check_cpu_capacity(rq, sd)) {
7930 sd = rcu_dereference(per_cpu(sd_asym, cpu));
7931 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7932 sched_domain_span(sd)) < cpu)) {
7942 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7946 * run_rebalance_domains is triggered when needed from the scheduler tick.
7947 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7949 static void run_rebalance_domains(struct softirq_action *h)
7951 struct rq *this_rq = this_rq();
7952 enum cpu_idle_type idle = this_rq->idle_balance ?
7953 CPU_IDLE : CPU_NOT_IDLE;
7956 * If this cpu has a pending nohz_balance_kick, then do the
7957 * balancing on behalf of the other idle cpus whose ticks are
7958 * stopped. Do nohz_idle_balance *before* rebalance_domains to
7959 * give the idle cpus a chance to load balance. Else we may
7960 * load balance only within the local sched_domain hierarchy
7961 * and abort nohz_idle_balance altogether if we pull some load.
7963 nohz_idle_balance(this_rq, idle);
7964 rebalance_domains(this_rq, idle);
7968 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7970 void trigger_load_balance(struct rq *rq)
7972 /* Don't need to rebalance while attached to NULL domain */
7973 if (unlikely(on_null_domain(rq)))
7976 if (time_after_eq(jiffies, rq->next_balance))
7977 raise_softirq(SCHED_SOFTIRQ);
7978 #ifdef CONFIG_NO_HZ_COMMON
7979 if (nohz_kick_needed(rq))
7980 nohz_balancer_kick();
7984 static void rq_online_fair(struct rq *rq)
7988 update_runtime_enabled(rq);
7991 static void rq_offline_fair(struct rq *rq)
7995 /* Ensure any throttled groups are reachable by pick_next_task */
7996 unthrottle_offline_cfs_rqs(rq);
7999 #endif /* CONFIG_SMP */
8002 * scheduler tick hitting a task of our scheduling class:
8004 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8006 struct cfs_rq *cfs_rq;
8007 struct sched_entity *se = &curr->se;
8009 for_each_sched_entity(se) {
8010 cfs_rq = cfs_rq_of(se);
8011 entity_tick(cfs_rq, se, queued);
8014 if (static_branch_unlikely(&sched_numa_balancing))
8015 task_tick_numa(rq, curr);
8019 * called on fork with the child task as argument from the parent's context
8020 * - child not yet on the tasklist
8021 * - preemption disabled
8023 static void task_fork_fair(struct task_struct *p)
8025 struct cfs_rq *cfs_rq;
8026 struct sched_entity *se = &p->se, *curr;
8027 int this_cpu = smp_processor_id();
8028 struct rq *rq = this_rq();
8029 unsigned long flags;
8031 raw_spin_lock_irqsave(&rq->lock, flags);
8033 update_rq_clock(rq);
8035 cfs_rq = task_cfs_rq(current);
8036 curr = cfs_rq->curr;
8039 * Not only the cpu but also the task_group of the parent might have
8040 * been changed after parent->se.parent,cfs_rq were copied to
8041 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8042 * of child point to valid ones.
8045 __set_task_cpu(p, this_cpu);
8048 update_curr(cfs_rq);
8051 se->vruntime = curr->vruntime;
8052 place_entity(cfs_rq, se, 1);
8054 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8056 * Upon rescheduling, sched_class::put_prev_task() will place
8057 * 'current' within the tree based on its new key value.
8059 swap(curr->vruntime, se->vruntime);
8063 se->vruntime -= cfs_rq->min_vruntime;
8065 raw_spin_unlock_irqrestore(&rq->lock, flags);
8069 * Priority of the task has changed. Check to see if we preempt
8073 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8075 if (!task_on_rq_queued(p))
8079 * Reschedule if we are currently running on this runqueue and
8080 * our priority decreased, or if we are not currently running on
8081 * this runqueue and our priority is higher than the current's
8083 if (rq->curr == p) {
8084 if (p->prio > oldprio)
8087 check_preempt_curr(rq, p, 0);
8090 static inline bool vruntime_normalized(struct task_struct *p)
8092 struct sched_entity *se = &p->se;
8095 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8096 * the dequeue_entity(.flags=0) will already have normalized the
8103 * When !on_rq, vruntime of the task has usually NOT been normalized.
8104 * But there are some cases where it has already been normalized:
8106 * - A forked child which is waiting for being woken up by
8107 * wake_up_new_task().
8108 * - A task which has been woken up by try_to_wake_up() and
8109 * waiting for actually being woken up by sched_ttwu_pending().
8111 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8117 static void detach_task_cfs_rq(struct task_struct *p)
8119 struct sched_entity *se = &p->se;
8120 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8122 if (!vruntime_normalized(p)) {
8124 * Fix up our vruntime so that the current sleep doesn't
8125 * cause 'unlimited' sleep bonus.
8127 place_entity(cfs_rq, se, 0);
8128 se->vruntime -= cfs_rq->min_vruntime;
8131 /* Catch up with the cfs_rq and remove our load when we leave */
8132 detach_entity_load_avg(cfs_rq, se);
8135 static void attach_task_cfs_rq(struct task_struct *p)
8137 struct sched_entity *se = &p->se;
8138 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8140 #ifdef CONFIG_FAIR_GROUP_SCHED
8142 * Since the real-depth could have been changed (only FAIR
8143 * class maintain depth value), reset depth properly.
8145 se->depth = se->parent ? se->parent->depth + 1 : 0;
8148 /* Synchronize task with its cfs_rq */
8149 attach_entity_load_avg(cfs_rq, se);
8151 if (!vruntime_normalized(p))
8152 se->vruntime += cfs_rq->min_vruntime;
8155 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8157 detach_task_cfs_rq(p);
8160 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8162 attach_task_cfs_rq(p);
8164 if (task_on_rq_queued(p)) {
8166 * We were most likely switched from sched_rt, so
8167 * kick off the schedule if running, otherwise just see
8168 * if we can still preempt the current task.
8173 check_preempt_curr(rq, p, 0);
8177 /* Account for a task changing its policy or group.
8179 * This routine is mostly called to set cfs_rq->curr field when a task
8180 * migrates between groups/classes.
8182 static void set_curr_task_fair(struct rq *rq)
8184 struct sched_entity *se = &rq->curr->se;
8186 for_each_sched_entity(se) {
8187 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8189 set_next_entity(cfs_rq, se);
8190 /* ensure bandwidth has been allocated on our new cfs_rq */
8191 account_cfs_rq_runtime(cfs_rq, 0);
8195 void init_cfs_rq(struct cfs_rq *cfs_rq)
8197 cfs_rq->tasks_timeline = RB_ROOT;
8198 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8199 #ifndef CONFIG_64BIT
8200 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8203 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8204 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8208 #ifdef CONFIG_FAIR_GROUP_SCHED
8209 static void task_move_group_fair(struct task_struct *p)
8211 detach_task_cfs_rq(p);
8212 set_task_rq(p, task_cpu(p));
8215 /* Tell se's cfs_rq has been changed -- migrated */
8216 p->se.avg.last_update_time = 0;
8218 attach_task_cfs_rq(p);
8221 void free_fair_sched_group(struct task_group *tg)
8225 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8227 for_each_possible_cpu(i) {
8229 kfree(tg->cfs_rq[i]);
8232 remove_entity_load_avg(tg->se[i]);
8241 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8243 struct cfs_rq *cfs_rq;
8244 struct sched_entity *se;
8247 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8250 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8254 tg->shares = NICE_0_LOAD;
8256 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8258 for_each_possible_cpu(i) {
8259 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8260 GFP_KERNEL, cpu_to_node(i));
8264 se = kzalloc_node(sizeof(struct sched_entity),
8265 GFP_KERNEL, cpu_to_node(i));
8269 init_cfs_rq(cfs_rq);
8270 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8271 init_entity_runnable_average(se);
8282 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8284 struct rq *rq = cpu_rq(cpu);
8285 unsigned long flags;
8288 * Only empty task groups can be destroyed; so we can speculatively
8289 * check on_list without danger of it being re-added.
8291 if (!tg->cfs_rq[cpu]->on_list)
8294 raw_spin_lock_irqsave(&rq->lock, flags);
8295 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8296 raw_spin_unlock_irqrestore(&rq->lock, flags);
8299 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8300 struct sched_entity *se, int cpu,
8301 struct sched_entity *parent)
8303 struct rq *rq = cpu_rq(cpu);
8307 init_cfs_rq_runtime(cfs_rq);
8309 tg->cfs_rq[cpu] = cfs_rq;
8312 /* se could be NULL for root_task_group */
8317 se->cfs_rq = &rq->cfs;
8320 se->cfs_rq = parent->my_q;
8321 se->depth = parent->depth + 1;
8325 /* guarantee group entities always have weight */
8326 update_load_set(&se->load, NICE_0_LOAD);
8327 se->parent = parent;
8330 static DEFINE_MUTEX(shares_mutex);
8332 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8335 unsigned long flags;
8338 * We can't change the weight of the root cgroup.
8343 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8345 mutex_lock(&shares_mutex);
8346 if (tg->shares == shares)
8349 tg->shares = shares;
8350 for_each_possible_cpu(i) {
8351 struct rq *rq = cpu_rq(i);
8352 struct sched_entity *se;
8355 /* Propagate contribution to hierarchy */
8356 raw_spin_lock_irqsave(&rq->lock, flags);
8358 /* Possible calls to update_curr() need rq clock */
8359 update_rq_clock(rq);
8360 for_each_sched_entity(se)
8361 update_cfs_shares(group_cfs_rq(se));
8362 raw_spin_unlock_irqrestore(&rq->lock, flags);
8366 mutex_unlock(&shares_mutex);
8369 #else /* CONFIG_FAIR_GROUP_SCHED */
8371 void free_fair_sched_group(struct task_group *tg) { }
8373 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8378 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8380 #endif /* CONFIG_FAIR_GROUP_SCHED */
8383 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8385 struct sched_entity *se = &task->se;
8386 unsigned int rr_interval = 0;
8389 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8392 if (rq->cfs.load.weight)
8393 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8399 * All the scheduling class methods:
8401 const struct sched_class fair_sched_class = {
8402 .next = &idle_sched_class,
8403 .enqueue_task = enqueue_task_fair,
8404 .dequeue_task = dequeue_task_fair,
8405 .yield_task = yield_task_fair,
8406 .yield_to_task = yield_to_task_fair,
8408 .check_preempt_curr = check_preempt_wakeup,
8410 .pick_next_task = pick_next_task_fair,
8411 .put_prev_task = put_prev_task_fair,
8414 .select_task_rq = select_task_rq_fair,
8415 .migrate_task_rq = migrate_task_rq_fair,
8417 .rq_online = rq_online_fair,
8418 .rq_offline = rq_offline_fair,
8420 .task_waking = task_waking_fair,
8421 .task_dead = task_dead_fair,
8422 .set_cpus_allowed = set_cpus_allowed_common,
8425 .set_curr_task = set_curr_task_fair,
8426 .task_tick = task_tick_fair,
8427 .task_fork = task_fork_fair,
8429 .prio_changed = prio_changed_fair,
8430 .switched_from = switched_from_fair,
8431 .switched_to = switched_to_fair,
8433 .get_rr_interval = get_rr_interval_fair,
8435 .update_curr = update_curr_fair,
8437 #ifdef CONFIG_FAIR_GROUP_SCHED
8438 .task_move_group = task_move_group_fair,
8442 #ifdef CONFIG_SCHED_DEBUG
8443 void print_cfs_stats(struct seq_file *m, int cpu)
8445 struct cfs_rq *cfs_rq;
8448 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8449 print_cfs_rq(m, cpu, cfs_rq);
8453 #ifdef CONFIG_NUMA_BALANCING
8454 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8457 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8459 for_each_online_node(node) {
8460 if (p->numa_faults) {
8461 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8462 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8464 if (p->numa_group) {
8465 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8466 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8468 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8471 #endif /* CONFIG_NUMA_BALANCING */
8472 #endif /* CONFIG_SCHED_DEBUG */
8474 __init void init_sched_fair_class(void)
8477 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8479 #ifdef CONFIG_NO_HZ_COMMON
8480 nohz.next_balance = jiffies;
8481 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8482 cpu_notifier(sched_ilb_notifier, 0);