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 */
690 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
691 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
693 void init_entity_runnable_average(struct sched_entity *se)
699 * Update the current task's runtime statistics.
701 static void update_curr(struct cfs_rq *cfs_rq)
703 struct sched_entity *curr = cfs_rq->curr;
704 u64 now = rq_clock_task(rq_of(cfs_rq));
710 delta_exec = now - curr->exec_start;
711 if (unlikely((s64)delta_exec <= 0))
714 curr->exec_start = now;
716 schedstat_set(curr->statistics.exec_max,
717 max(delta_exec, curr->statistics.exec_max));
719 curr->sum_exec_runtime += delta_exec;
720 schedstat_add(cfs_rq, exec_clock, delta_exec);
722 curr->vruntime += calc_delta_fair(delta_exec, curr);
723 update_min_vruntime(cfs_rq);
725 if (entity_is_task(curr)) {
726 struct task_struct *curtask = task_of(curr);
728 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
729 cpuacct_charge(curtask, delta_exec);
730 account_group_exec_runtime(curtask, delta_exec);
733 account_cfs_rq_runtime(cfs_rq, delta_exec);
736 static void update_curr_fair(struct rq *rq)
738 update_curr(cfs_rq_of(&rq->curr->se));
742 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
744 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
748 * Task is being enqueued - update stats:
750 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
753 * Are we enqueueing a waiting task? (for current tasks
754 * a dequeue/enqueue event is a NOP)
756 if (se != cfs_rq->curr)
757 update_stats_wait_start(cfs_rq, se);
761 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
763 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
764 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
765 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
766 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
767 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
768 #ifdef CONFIG_SCHEDSTATS
769 if (entity_is_task(se)) {
770 trace_sched_stat_wait(task_of(se),
771 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
774 schedstat_set(se->statistics.wait_start, 0);
778 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
781 * Mark the end of the wait period if dequeueing a
784 if (se != cfs_rq->curr)
785 update_stats_wait_end(cfs_rq, se);
789 * We are picking a new current task - update its stats:
792 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
795 * We are starting a new run period:
797 se->exec_start = rq_clock_task(rq_of(cfs_rq));
800 /**************************************************
801 * Scheduling class queueing methods:
804 #ifdef CONFIG_NUMA_BALANCING
806 * Approximate time to scan a full NUMA task in ms. The task scan period is
807 * calculated based on the tasks virtual memory size and
808 * numa_balancing_scan_size.
810 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
811 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
813 /* Portion of address space to scan in MB */
814 unsigned int sysctl_numa_balancing_scan_size = 256;
816 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
817 unsigned int sysctl_numa_balancing_scan_delay = 1000;
819 static unsigned int task_nr_scan_windows(struct task_struct *p)
821 unsigned long rss = 0;
822 unsigned long nr_scan_pages;
825 * Calculations based on RSS as non-present and empty pages are skipped
826 * by the PTE scanner and NUMA hinting faults should be trapped based
829 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
830 rss = get_mm_rss(p->mm);
834 rss = round_up(rss, nr_scan_pages);
835 return rss / nr_scan_pages;
838 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
839 #define MAX_SCAN_WINDOW 2560
841 static unsigned int task_scan_min(struct task_struct *p)
843 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
844 unsigned int scan, floor;
845 unsigned int windows = 1;
847 if (scan_size < MAX_SCAN_WINDOW)
848 windows = MAX_SCAN_WINDOW / scan_size;
849 floor = 1000 / windows;
851 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
852 return max_t(unsigned int, floor, scan);
855 static unsigned int task_scan_max(struct task_struct *p)
857 unsigned int smin = task_scan_min(p);
860 /* Watch for min being lower than max due to floor calculations */
861 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
862 return max(smin, smax);
865 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
867 rq->nr_numa_running += (p->numa_preferred_nid != -1);
868 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
871 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
873 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
874 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
880 spinlock_t lock; /* nr_tasks, tasks */
885 nodemask_t active_nodes;
886 unsigned long total_faults;
888 * Faults_cpu is used to decide whether memory should move
889 * towards the CPU. As a consequence, these stats are weighted
890 * more by CPU use than by memory faults.
892 unsigned long *faults_cpu;
893 unsigned long faults[0];
896 /* Shared or private faults. */
897 #define NR_NUMA_HINT_FAULT_TYPES 2
899 /* Memory and CPU locality */
900 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
902 /* Averaged statistics, and temporary buffers. */
903 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
905 pid_t task_numa_group_id(struct task_struct *p)
907 return p->numa_group ? p->numa_group->gid : 0;
911 * The averaged statistics, shared & private, memory & cpu,
912 * occupy the first half of the array. The second half of the
913 * array is for current counters, which are averaged into the
914 * first set by task_numa_placement.
916 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
918 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
921 static inline unsigned long task_faults(struct task_struct *p, int nid)
926 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
927 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
930 static inline unsigned long group_faults(struct task_struct *p, int nid)
935 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
936 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
939 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
941 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
942 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
945 /* Handle placement on systems where not all nodes are directly connected. */
946 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
947 int maxdist, bool task)
949 unsigned long score = 0;
953 * All nodes are directly connected, and the same distance
954 * from each other. No need for fancy placement algorithms.
956 if (sched_numa_topology_type == NUMA_DIRECT)
960 * This code is called for each node, introducing N^2 complexity,
961 * which should be ok given the number of nodes rarely exceeds 8.
963 for_each_online_node(node) {
964 unsigned long faults;
965 int dist = node_distance(nid, node);
968 * The furthest away nodes in the system are not interesting
969 * for placement; nid was already counted.
971 if (dist == sched_max_numa_distance || node == nid)
975 * On systems with a backplane NUMA topology, compare groups
976 * of nodes, and move tasks towards the group with the most
977 * memory accesses. When comparing two nodes at distance
978 * "hoplimit", only nodes closer by than "hoplimit" are part
979 * of each group. Skip other nodes.
981 if (sched_numa_topology_type == NUMA_BACKPLANE &&
985 /* Add up the faults from nearby nodes. */
987 faults = task_faults(p, node);
989 faults = group_faults(p, node);
992 * On systems with a glueless mesh NUMA topology, there are
993 * no fixed "groups of nodes". Instead, nodes that are not
994 * directly connected bounce traffic through intermediate
995 * nodes; a numa_group can occupy any set of nodes.
996 * The further away a node is, the less the faults count.
997 * This seems to result in good task placement.
999 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1000 faults *= (sched_max_numa_distance - dist);
1001 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1011 * These return the fraction of accesses done by a particular task, or
1012 * task group, on a particular numa node. The group weight is given a
1013 * larger multiplier, in order to group tasks together that are almost
1014 * evenly spread out between numa nodes.
1016 static inline unsigned long task_weight(struct task_struct *p, int nid,
1019 unsigned long faults, total_faults;
1021 if (!p->numa_faults)
1024 total_faults = p->total_numa_faults;
1029 faults = task_faults(p, nid);
1030 faults += score_nearby_nodes(p, nid, dist, true);
1032 return 1000 * faults / total_faults;
1035 static inline unsigned long group_weight(struct task_struct *p, int nid,
1038 unsigned long faults, total_faults;
1043 total_faults = p->numa_group->total_faults;
1048 faults = group_faults(p, nid);
1049 faults += score_nearby_nodes(p, nid, dist, false);
1051 return 1000 * faults / total_faults;
1054 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1055 int src_nid, int dst_cpu)
1057 struct numa_group *ng = p->numa_group;
1058 int dst_nid = cpu_to_node(dst_cpu);
1059 int last_cpupid, this_cpupid;
1061 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1064 * Multi-stage node selection is used in conjunction with a periodic
1065 * migration fault to build a temporal task<->page relation. By using
1066 * a two-stage filter we remove short/unlikely relations.
1068 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1069 * a task's usage of a particular page (n_p) per total usage of this
1070 * page (n_t) (in a given time-span) to a probability.
1072 * Our periodic faults will sample this probability and getting the
1073 * same result twice in a row, given these samples are fully
1074 * independent, is then given by P(n)^2, provided our sample period
1075 * is sufficiently short compared to the usage pattern.
1077 * This quadric squishes small probabilities, making it less likely we
1078 * act on an unlikely task<->page relation.
1080 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1081 if (!cpupid_pid_unset(last_cpupid) &&
1082 cpupid_to_nid(last_cpupid) != dst_nid)
1085 /* Always allow migrate on private faults */
1086 if (cpupid_match_pid(p, last_cpupid))
1089 /* A shared fault, but p->numa_group has not been set up yet. */
1094 * Do not migrate if the destination is not a node that
1095 * is actively used by this numa group.
1097 if (!node_isset(dst_nid, ng->active_nodes))
1101 * Source is a node that is not actively used by this
1102 * numa group, while the destination is. Migrate.
1104 if (!node_isset(src_nid, ng->active_nodes))
1108 * Both source and destination are nodes in active
1109 * use by this numa group. Maximize memory bandwidth
1110 * by migrating from more heavily used groups, to less
1111 * heavily used ones, spreading the load around.
1112 * Use a 1/4 hysteresis to avoid spurious page movement.
1114 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1117 static unsigned long weighted_cpuload(const int cpu);
1118 static unsigned long source_load(int cpu, int type);
1119 static unsigned long target_load(int cpu, int type);
1120 static unsigned long capacity_of(int cpu);
1121 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1123 /* Cached statistics for all CPUs within a node */
1125 unsigned long nr_running;
1128 /* Total compute capacity of CPUs on a node */
1129 unsigned long compute_capacity;
1131 /* Approximate capacity in terms of runnable tasks on a node */
1132 unsigned long task_capacity;
1133 int has_free_capacity;
1137 * XXX borrowed from update_sg_lb_stats
1139 static void update_numa_stats(struct numa_stats *ns, int nid)
1141 int smt, cpu, cpus = 0;
1142 unsigned long capacity;
1144 memset(ns, 0, sizeof(*ns));
1145 for_each_cpu(cpu, cpumask_of_node(nid)) {
1146 struct rq *rq = cpu_rq(cpu);
1148 ns->nr_running += rq->nr_running;
1149 ns->load += weighted_cpuload(cpu);
1150 ns->compute_capacity += capacity_of(cpu);
1156 * If we raced with hotplug and there are no CPUs left in our mask
1157 * the @ns structure is NULL'ed and task_numa_compare() will
1158 * not find this node attractive.
1160 * We'll either bail at !has_free_capacity, or we'll detect a huge
1161 * imbalance and bail there.
1166 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1167 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1168 capacity = cpus / smt; /* cores */
1170 ns->task_capacity = min_t(unsigned, capacity,
1171 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1172 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1175 struct task_numa_env {
1176 struct task_struct *p;
1178 int src_cpu, src_nid;
1179 int dst_cpu, dst_nid;
1181 struct numa_stats src_stats, dst_stats;
1186 struct task_struct *best_task;
1191 static void task_numa_assign(struct task_numa_env *env,
1192 struct task_struct *p, long imp)
1195 put_task_struct(env->best_task);
1200 env->best_imp = imp;
1201 env->best_cpu = env->dst_cpu;
1204 static bool load_too_imbalanced(long src_load, long dst_load,
1205 struct task_numa_env *env)
1208 long orig_src_load, orig_dst_load;
1209 long src_capacity, dst_capacity;
1212 * The load is corrected for the CPU capacity available on each node.
1215 * ------------ vs ---------
1216 * src_capacity dst_capacity
1218 src_capacity = env->src_stats.compute_capacity;
1219 dst_capacity = env->dst_stats.compute_capacity;
1221 /* We care about the slope of the imbalance, not the direction. */
1222 if (dst_load < src_load)
1223 swap(dst_load, src_load);
1225 /* Is the difference below the threshold? */
1226 imb = dst_load * src_capacity * 100 -
1227 src_load * dst_capacity * env->imbalance_pct;
1232 * The imbalance is above the allowed threshold.
1233 * Compare it with the old imbalance.
1235 orig_src_load = env->src_stats.load;
1236 orig_dst_load = env->dst_stats.load;
1238 if (orig_dst_load < orig_src_load)
1239 swap(orig_dst_load, orig_src_load);
1241 old_imb = orig_dst_load * src_capacity * 100 -
1242 orig_src_load * dst_capacity * env->imbalance_pct;
1244 /* Would this change make things worse? */
1245 return (imb > old_imb);
1249 * This checks if the overall compute and NUMA accesses of the system would
1250 * be improved if the source tasks was migrated to the target dst_cpu taking
1251 * into account that it might be best if task running on the dst_cpu should
1252 * be exchanged with the source task
1254 static void task_numa_compare(struct task_numa_env *env,
1255 long taskimp, long groupimp)
1257 struct rq *src_rq = cpu_rq(env->src_cpu);
1258 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1259 struct task_struct *cur;
1260 long src_load, dst_load;
1262 long imp = env->p->numa_group ? groupimp : taskimp;
1264 int dist = env->dist;
1268 raw_spin_lock_irq(&dst_rq->lock);
1271 * No need to move the exiting task, and this ensures that ->curr
1272 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1273 * is safe under RCU read lock.
1274 * Note that rcu_read_lock() itself can't protect from the final
1275 * put_task_struct() after the last schedule().
1277 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1279 raw_spin_unlock_irq(&dst_rq->lock);
1282 * Because we have preemption enabled we can get migrated around and
1283 * end try selecting ourselves (current == env->p) as a swap candidate.
1289 * "imp" is the fault differential for the source task between the
1290 * source and destination node. Calculate the total differential for
1291 * the source task and potential destination task. The more negative
1292 * the value is, the more rmeote accesses that would be expected to
1293 * be incurred if the tasks were swapped.
1296 /* Skip this swap candidate if cannot move to the source cpu */
1297 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1301 * If dst and source tasks are in the same NUMA group, or not
1302 * in any group then look only at task weights.
1304 if (cur->numa_group == env->p->numa_group) {
1305 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1306 task_weight(cur, env->dst_nid, dist);
1308 * Add some hysteresis to prevent swapping the
1309 * tasks within a group over tiny differences.
1311 if (cur->numa_group)
1315 * Compare the group weights. If a task is all by
1316 * itself (not part of a group), use the task weight
1319 if (cur->numa_group)
1320 imp += group_weight(cur, env->src_nid, dist) -
1321 group_weight(cur, env->dst_nid, dist);
1323 imp += task_weight(cur, env->src_nid, dist) -
1324 task_weight(cur, env->dst_nid, dist);
1328 if (imp <= env->best_imp && moveimp <= env->best_imp)
1332 /* Is there capacity at our destination? */
1333 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1334 !env->dst_stats.has_free_capacity)
1340 /* Balance doesn't matter much if we're running a task per cpu */
1341 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1342 dst_rq->nr_running == 1)
1346 * In the overloaded case, try and keep the load balanced.
1349 load = task_h_load(env->p);
1350 dst_load = env->dst_stats.load + load;
1351 src_load = env->src_stats.load - load;
1353 if (moveimp > imp && moveimp > env->best_imp) {
1355 * If the improvement from just moving env->p direction is
1356 * better than swapping tasks around, check if a move is
1357 * possible. Store a slightly smaller score than moveimp,
1358 * so an actually idle CPU will win.
1360 if (!load_too_imbalanced(src_load, dst_load, env)) {
1367 if (imp <= env->best_imp)
1371 load = task_h_load(cur);
1376 if (load_too_imbalanced(src_load, dst_load, env))
1380 * One idle CPU per node is evaluated for a task numa move.
1381 * Call select_idle_sibling to maybe find a better one.
1384 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1387 task_numa_assign(env, cur, imp);
1392 static void task_numa_find_cpu(struct task_numa_env *env,
1393 long taskimp, long groupimp)
1397 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1398 /* Skip this CPU if the source task cannot migrate */
1399 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1403 task_numa_compare(env, taskimp, groupimp);
1407 /* Only move tasks to a NUMA node less busy than the current node. */
1408 static bool numa_has_capacity(struct task_numa_env *env)
1410 struct numa_stats *src = &env->src_stats;
1411 struct numa_stats *dst = &env->dst_stats;
1413 if (src->has_free_capacity && !dst->has_free_capacity)
1417 * Only consider a task move if the source has a higher load
1418 * than the destination, corrected for CPU capacity on each node.
1420 * src->load dst->load
1421 * --------------------- vs ---------------------
1422 * src->compute_capacity dst->compute_capacity
1424 if (src->load * dst->compute_capacity * env->imbalance_pct >
1426 dst->load * src->compute_capacity * 100)
1432 static int task_numa_migrate(struct task_struct *p)
1434 struct task_numa_env env = {
1437 .src_cpu = task_cpu(p),
1438 .src_nid = task_node(p),
1440 .imbalance_pct = 112,
1446 struct sched_domain *sd;
1447 unsigned long taskweight, groupweight;
1449 long taskimp, groupimp;
1452 * Pick the lowest SD_NUMA domain, as that would have the smallest
1453 * imbalance and would be the first to start moving tasks about.
1455 * And we want to avoid any moving of tasks about, as that would create
1456 * random movement of tasks -- counter the numa conditions we're trying
1460 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1462 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1466 * Cpusets can break the scheduler domain tree into smaller
1467 * balance domains, some of which do not cross NUMA boundaries.
1468 * Tasks that are "trapped" in such domains cannot be migrated
1469 * elsewhere, so there is no point in (re)trying.
1471 if (unlikely(!sd)) {
1472 p->numa_preferred_nid = task_node(p);
1476 env.dst_nid = p->numa_preferred_nid;
1477 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1478 taskweight = task_weight(p, env.src_nid, dist);
1479 groupweight = group_weight(p, env.src_nid, dist);
1480 update_numa_stats(&env.src_stats, env.src_nid);
1481 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1482 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1483 update_numa_stats(&env.dst_stats, env.dst_nid);
1485 /* Try to find a spot on the preferred nid. */
1486 if (numa_has_capacity(&env))
1487 task_numa_find_cpu(&env, taskimp, groupimp);
1490 * Look at other nodes in these cases:
1491 * - there is no space available on the preferred_nid
1492 * - the task is part of a numa_group that is interleaved across
1493 * multiple NUMA nodes; in order to better consolidate the group,
1494 * we need to check other locations.
1496 if (env.best_cpu == -1 || (p->numa_group &&
1497 nodes_weight(p->numa_group->active_nodes) > 1)) {
1498 for_each_online_node(nid) {
1499 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1502 dist = node_distance(env.src_nid, env.dst_nid);
1503 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1505 taskweight = task_weight(p, env.src_nid, dist);
1506 groupweight = group_weight(p, env.src_nid, dist);
1509 /* Only consider nodes where both task and groups benefit */
1510 taskimp = task_weight(p, nid, dist) - taskweight;
1511 groupimp = group_weight(p, nid, dist) - groupweight;
1512 if (taskimp < 0 && groupimp < 0)
1517 update_numa_stats(&env.dst_stats, env.dst_nid);
1518 if (numa_has_capacity(&env))
1519 task_numa_find_cpu(&env, taskimp, groupimp);
1524 * If the task is part of a workload that spans multiple NUMA nodes,
1525 * and is migrating into one of the workload's active nodes, remember
1526 * this node as the task's preferred numa node, so the workload can
1528 * A task that migrated to a second choice node will be better off
1529 * trying for a better one later. Do not set the preferred node here.
1531 if (p->numa_group) {
1532 if (env.best_cpu == -1)
1537 if (node_isset(nid, p->numa_group->active_nodes))
1538 sched_setnuma(p, env.dst_nid);
1541 /* No better CPU than the current one was found. */
1542 if (env.best_cpu == -1)
1546 * Reset the scan period if the task is being rescheduled on an
1547 * alternative node to recheck if the tasks is now properly placed.
1549 p->numa_scan_period = task_scan_min(p);
1551 if (env.best_task == NULL) {
1552 ret = migrate_task_to(p, env.best_cpu);
1554 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1558 ret = migrate_swap(p, env.best_task);
1560 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1561 put_task_struct(env.best_task);
1565 /* Attempt to migrate a task to a CPU on the preferred node. */
1566 static void numa_migrate_preferred(struct task_struct *p)
1568 unsigned long interval = HZ;
1570 /* This task has no NUMA fault statistics yet */
1571 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1574 /* Periodically retry migrating the task to the preferred node */
1575 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1576 p->numa_migrate_retry = jiffies + interval;
1578 /* Success if task is already running on preferred CPU */
1579 if (task_node(p) == p->numa_preferred_nid)
1582 /* Otherwise, try migrate to a CPU on the preferred node */
1583 task_numa_migrate(p);
1587 * Find the nodes on which the workload is actively running. We do this by
1588 * tracking the nodes from which NUMA hinting faults are triggered. This can
1589 * be different from the set of nodes where the workload's memory is currently
1592 * The bitmask is used to make smarter decisions on when to do NUMA page
1593 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1594 * are added when they cause over 6/16 of the maximum number of faults, but
1595 * only removed when they drop below 3/16.
1597 static void update_numa_active_node_mask(struct numa_group *numa_group)
1599 unsigned long faults, max_faults = 0;
1602 for_each_online_node(nid) {
1603 faults = group_faults_cpu(numa_group, nid);
1604 if (faults > max_faults)
1605 max_faults = faults;
1608 for_each_online_node(nid) {
1609 faults = group_faults_cpu(numa_group, nid);
1610 if (!node_isset(nid, numa_group->active_nodes)) {
1611 if (faults > max_faults * 6 / 16)
1612 node_set(nid, numa_group->active_nodes);
1613 } else if (faults < max_faults * 3 / 16)
1614 node_clear(nid, numa_group->active_nodes);
1619 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1620 * increments. The more local the fault statistics are, the higher the scan
1621 * period will be for the next scan window. If local/(local+remote) ratio is
1622 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1623 * the scan period will decrease. Aim for 70% local accesses.
1625 #define NUMA_PERIOD_SLOTS 10
1626 #define NUMA_PERIOD_THRESHOLD 7
1629 * Increase the scan period (slow down scanning) if the majority of
1630 * our memory is already on our local node, or if the majority of
1631 * the page accesses are shared with other processes.
1632 * Otherwise, decrease the scan period.
1634 static void update_task_scan_period(struct task_struct *p,
1635 unsigned long shared, unsigned long private)
1637 unsigned int period_slot;
1641 unsigned long remote = p->numa_faults_locality[0];
1642 unsigned long local = p->numa_faults_locality[1];
1645 * If there were no record hinting faults then either the task is
1646 * completely idle or all activity is areas that are not of interest
1647 * to automatic numa balancing. Related to that, if there were failed
1648 * migration then it implies we are migrating too quickly or the local
1649 * node is overloaded. In either case, scan slower
1651 if (local + shared == 0 || p->numa_faults_locality[2]) {
1652 p->numa_scan_period = min(p->numa_scan_period_max,
1653 p->numa_scan_period << 1);
1655 p->mm->numa_next_scan = jiffies +
1656 msecs_to_jiffies(p->numa_scan_period);
1662 * Prepare to scale scan period relative to the current period.
1663 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1664 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1665 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1667 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1668 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1669 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1670 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1673 diff = slot * period_slot;
1675 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1678 * Scale scan rate increases based on sharing. There is an
1679 * inverse relationship between the degree of sharing and
1680 * the adjustment made to the scanning period. Broadly
1681 * speaking the intent is that there is little point
1682 * scanning faster if shared accesses dominate as it may
1683 * simply bounce migrations uselessly
1685 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1686 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1689 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1690 task_scan_min(p), task_scan_max(p));
1691 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1695 * Get the fraction of time the task has been running since the last
1696 * NUMA placement cycle. The scheduler keeps similar statistics, but
1697 * decays those on a 32ms period, which is orders of magnitude off
1698 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1699 * stats only if the task is so new there are no NUMA statistics yet.
1701 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1703 u64 runtime, delta, now;
1704 /* Use the start of this time slice to avoid calculations. */
1705 now = p->se.exec_start;
1706 runtime = p->se.sum_exec_runtime;
1708 if (p->last_task_numa_placement) {
1709 delta = runtime - p->last_sum_exec_runtime;
1710 *period = now - p->last_task_numa_placement;
1712 delta = p->se.avg.load_sum / p->se.load.weight;
1713 *period = LOAD_AVG_MAX;
1716 p->last_sum_exec_runtime = runtime;
1717 p->last_task_numa_placement = now;
1723 * Determine the preferred nid for a task in a numa_group. This needs to
1724 * be done in a way that produces consistent results with group_weight,
1725 * otherwise workloads might not converge.
1727 static int preferred_group_nid(struct task_struct *p, int nid)
1732 /* Direct connections between all NUMA nodes. */
1733 if (sched_numa_topology_type == NUMA_DIRECT)
1737 * On a system with glueless mesh NUMA topology, group_weight
1738 * scores nodes according to the number of NUMA hinting faults on
1739 * both the node itself, and on nearby nodes.
1741 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1742 unsigned long score, max_score = 0;
1743 int node, max_node = nid;
1745 dist = sched_max_numa_distance;
1747 for_each_online_node(node) {
1748 score = group_weight(p, node, dist);
1749 if (score > max_score) {
1758 * Finding the preferred nid in a system with NUMA backplane
1759 * interconnect topology is more involved. The goal is to locate
1760 * tasks from numa_groups near each other in the system, and
1761 * untangle workloads from different sides of the system. This requires
1762 * searching down the hierarchy of node groups, recursively searching
1763 * inside the highest scoring group of nodes. The nodemask tricks
1764 * keep the complexity of the search down.
1766 nodes = node_online_map;
1767 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1768 unsigned long max_faults = 0;
1769 nodemask_t max_group = NODE_MASK_NONE;
1772 /* Are there nodes at this distance from each other? */
1773 if (!find_numa_distance(dist))
1776 for_each_node_mask(a, nodes) {
1777 unsigned long faults = 0;
1778 nodemask_t this_group;
1779 nodes_clear(this_group);
1781 /* Sum group's NUMA faults; includes a==b case. */
1782 for_each_node_mask(b, nodes) {
1783 if (node_distance(a, b) < dist) {
1784 faults += group_faults(p, b);
1785 node_set(b, this_group);
1786 node_clear(b, nodes);
1790 /* Remember the top group. */
1791 if (faults > max_faults) {
1792 max_faults = faults;
1793 max_group = this_group;
1795 * subtle: at the smallest distance there is
1796 * just one node left in each "group", the
1797 * winner is the preferred nid.
1802 /* Next round, evaluate the nodes within max_group. */
1810 static void task_numa_placement(struct task_struct *p)
1812 int seq, nid, max_nid = -1, max_group_nid = -1;
1813 unsigned long max_faults = 0, max_group_faults = 0;
1814 unsigned long fault_types[2] = { 0, 0 };
1815 unsigned long total_faults;
1816 u64 runtime, period;
1817 spinlock_t *group_lock = NULL;
1820 * The p->mm->numa_scan_seq field gets updated without
1821 * exclusive access. Use READ_ONCE() here to ensure
1822 * that the field is read in a single access:
1824 seq = READ_ONCE(p->mm->numa_scan_seq);
1825 if (p->numa_scan_seq == seq)
1827 p->numa_scan_seq = seq;
1828 p->numa_scan_period_max = task_scan_max(p);
1830 total_faults = p->numa_faults_locality[0] +
1831 p->numa_faults_locality[1];
1832 runtime = numa_get_avg_runtime(p, &period);
1834 /* If the task is part of a group prevent parallel updates to group stats */
1835 if (p->numa_group) {
1836 group_lock = &p->numa_group->lock;
1837 spin_lock_irq(group_lock);
1840 /* Find the node with the highest number of faults */
1841 for_each_online_node(nid) {
1842 /* Keep track of the offsets in numa_faults array */
1843 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1844 unsigned long faults = 0, group_faults = 0;
1847 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1848 long diff, f_diff, f_weight;
1850 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1851 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1852 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1853 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1855 /* Decay existing window, copy faults since last scan */
1856 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1857 fault_types[priv] += p->numa_faults[membuf_idx];
1858 p->numa_faults[membuf_idx] = 0;
1861 * Normalize the faults_from, so all tasks in a group
1862 * count according to CPU use, instead of by the raw
1863 * number of faults. Tasks with little runtime have
1864 * little over-all impact on throughput, and thus their
1865 * faults are less important.
1867 f_weight = div64_u64(runtime << 16, period + 1);
1868 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1870 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1871 p->numa_faults[cpubuf_idx] = 0;
1873 p->numa_faults[mem_idx] += diff;
1874 p->numa_faults[cpu_idx] += f_diff;
1875 faults += p->numa_faults[mem_idx];
1876 p->total_numa_faults += diff;
1877 if (p->numa_group) {
1879 * safe because we can only change our own group
1881 * mem_idx represents the offset for a given
1882 * nid and priv in a specific region because it
1883 * is at the beginning of the numa_faults array.
1885 p->numa_group->faults[mem_idx] += diff;
1886 p->numa_group->faults_cpu[mem_idx] += f_diff;
1887 p->numa_group->total_faults += diff;
1888 group_faults += p->numa_group->faults[mem_idx];
1892 if (faults > max_faults) {
1893 max_faults = faults;
1897 if (group_faults > max_group_faults) {
1898 max_group_faults = group_faults;
1899 max_group_nid = nid;
1903 update_task_scan_period(p, fault_types[0], fault_types[1]);
1905 if (p->numa_group) {
1906 update_numa_active_node_mask(p->numa_group);
1907 spin_unlock_irq(group_lock);
1908 max_nid = preferred_group_nid(p, max_group_nid);
1912 /* Set the new preferred node */
1913 if (max_nid != p->numa_preferred_nid)
1914 sched_setnuma(p, max_nid);
1916 if (task_node(p) != p->numa_preferred_nid)
1917 numa_migrate_preferred(p);
1921 static inline int get_numa_group(struct numa_group *grp)
1923 return atomic_inc_not_zero(&grp->refcount);
1926 static inline void put_numa_group(struct numa_group *grp)
1928 if (atomic_dec_and_test(&grp->refcount))
1929 kfree_rcu(grp, rcu);
1932 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1935 struct numa_group *grp, *my_grp;
1936 struct task_struct *tsk;
1938 int cpu = cpupid_to_cpu(cpupid);
1941 if (unlikely(!p->numa_group)) {
1942 unsigned int size = sizeof(struct numa_group) +
1943 4*nr_node_ids*sizeof(unsigned long);
1945 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1949 atomic_set(&grp->refcount, 1);
1950 spin_lock_init(&grp->lock);
1952 /* Second half of the array tracks nids where faults happen */
1953 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1956 node_set(task_node(current), grp->active_nodes);
1958 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1959 grp->faults[i] = p->numa_faults[i];
1961 grp->total_faults = p->total_numa_faults;
1964 rcu_assign_pointer(p->numa_group, grp);
1968 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1970 if (!cpupid_match_pid(tsk, cpupid))
1973 grp = rcu_dereference(tsk->numa_group);
1977 my_grp = p->numa_group;
1982 * Only join the other group if its bigger; if we're the bigger group,
1983 * the other task will join us.
1985 if (my_grp->nr_tasks > grp->nr_tasks)
1989 * Tie-break on the grp address.
1991 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1994 /* Always join threads in the same process. */
1995 if (tsk->mm == current->mm)
1998 /* Simple filter to avoid false positives due to PID collisions */
1999 if (flags & TNF_SHARED)
2002 /* Update priv based on whether false sharing was detected */
2005 if (join && !get_numa_group(grp))
2013 BUG_ON(irqs_disabled());
2014 double_lock_irq(&my_grp->lock, &grp->lock);
2016 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2017 my_grp->faults[i] -= p->numa_faults[i];
2018 grp->faults[i] += p->numa_faults[i];
2020 my_grp->total_faults -= p->total_numa_faults;
2021 grp->total_faults += p->total_numa_faults;
2026 spin_unlock(&my_grp->lock);
2027 spin_unlock_irq(&grp->lock);
2029 rcu_assign_pointer(p->numa_group, grp);
2031 put_numa_group(my_grp);
2039 void task_numa_free(struct task_struct *p)
2041 struct numa_group *grp = p->numa_group;
2042 void *numa_faults = p->numa_faults;
2043 unsigned long flags;
2047 spin_lock_irqsave(&grp->lock, flags);
2048 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2049 grp->faults[i] -= p->numa_faults[i];
2050 grp->total_faults -= p->total_numa_faults;
2053 spin_unlock_irqrestore(&grp->lock, flags);
2054 RCU_INIT_POINTER(p->numa_group, NULL);
2055 put_numa_group(grp);
2058 p->numa_faults = NULL;
2063 * Got a PROT_NONE fault for a page on @node.
2065 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2067 struct task_struct *p = current;
2068 bool migrated = flags & TNF_MIGRATED;
2069 int cpu_node = task_node(current);
2070 int local = !!(flags & TNF_FAULT_LOCAL);
2073 if (!static_branch_likely(&sched_numa_balancing))
2076 /* for example, ksmd faulting in a user's mm */
2080 /* Allocate buffer to track faults on a per-node basis */
2081 if (unlikely(!p->numa_faults)) {
2082 int size = sizeof(*p->numa_faults) *
2083 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2085 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2086 if (!p->numa_faults)
2089 p->total_numa_faults = 0;
2090 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2094 * First accesses are treated as private, otherwise consider accesses
2095 * to be private if the accessing pid has not changed
2097 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2100 priv = cpupid_match_pid(p, last_cpupid);
2101 if (!priv && !(flags & TNF_NO_GROUP))
2102 task_numa_group(p, last_cpupid, flags, &priv);
2106 * If a workload spans multiple NUMA nodes, a shared fault that
2107 * occurs wholly within the set of nodes that the workload is
2108 * actively using should be counted as local. This allows the
2109 * scan rate to slow down when a workload has settled down.
2111 if (!priv && !local && p->numa_group &&
2112 node_isset(cpu_node, p->numa_group->active_nodes) &&
2113 node_isset(mem_node, p->numa_group->active_nodes))
2116 task_numa_placement(p);
2119 * Retry task to preferred node migration periodically, in case it
2120 * case it previously failed, or the scheduler moved us.
2122 if (time_after(jiffies, p->numa_migrate_retry))
2123 numa_migrate_preferred(p);
2126 p->numa_pages_migrated += pages;
2127 if (flags & TNF_MIGRATE_FAIL)
2128 p->numa_faults_locality[2] += pages;
2130 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2131 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2132 p->numa_faults_locality[local] += pages;
2135 static void reset_ptenuma_scan(struct task_struct *p)
2138 * We only did a read acquisition of the mmap sem, so
2139 * p->mm->numa_scan_seq is written to without exclusive access
2140 * and the update is not guaranteed to be atomic. That's not
2141 * much of an issue though, since this is just used for
2142 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2143 * expensive, to avoid any form of compiler optimizations:
2145 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2146 p->mm->numa_scan_offset = 0;
2150 * The expensive part of numa migration is done from task_work context.
2151 * Triggered from task_tick_numa().
2153 void task_numa_work(struct callback_head *work)
2155 unsigned long migrate, next_scan, now = jiffies;
2156 struct task_struct *p = current;
2157 struct mm_struct *mm = p->mm;
2158 struct vm_area_struct *vma;
2159 unsigned long start, end;
2160 unsigned long nr_pte_updates = 0;
2161 long pages, virtpages;
2163 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2165 work->next = work; /* protect against double add */
2167 * Who cares about NUMA placement when they're dying.
2169 * NOTE: make sure not to dereference p->mm before this check,
2170 * exit_task_work() happens _after_ exit_mm() so we could be called
2171 * without p->mm even though we still had it when we enqueued this
2174 if (p->flags & PF_EXITING)
2177 if (!mm->numa_next_scan) {
2178 mm->numa_next_scan = now +
2179 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2183 * Enforce maximal scan/migration frequency..
2185 migrate = mm->numa_next_scan;
2186 if (time_before(now, migrate))
2189 if (p->numa_scan_period == 0) {
2190 p->numa_scan_period_max = task_scan_max(p);
2191 p->numa_scan_period = task_scan_min(p);
2194 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2195 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2199 * Delay this task enough that another task of this mm will likely win
2200 * the next time around.
2202 p->node_stamp += 2 * TICK_NSEC;
2204 start = mm->numa_scan_offset;
2205 pages = sysctl_numa_balancing_scan_size;
2206 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2207 virtpages = pages * 8; /* Scan up to this much virtual space */
2212 down_read(&mm->mmap_sem);
2213 vma = find_vma(mm, start);
2215 reset_ptenuma_scan(p);
2219 for (; vma; vma = vma->vm_next) {
2220 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2221 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2226 * Shared library pages mapped by multiple processes are not
2227 * migrated as it is expected they are cache replicated. Avoid
2228 * hinting faults in read-only file-backed mappings or the vdso
2229 * as migrating the pages will be of marginal benefit.
2232 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2236 * Skip inaccessible VMAs to avoid any confusion between
2237 * PROT_NONE and NUMA hinting ptes
2239 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2243 start = max(start, vma->vm_start);
2244 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2245 end = min(end, vma->vm_end);
2246 nr_pte_updates = change_prot_numa(vma, start, end);
2249 * Try to scan sysctl_numa_balancing_size worth of
2250 * hpages that have at least one present PTE that
2251 * is not already pte-numa. If the VMA contains
2252 * areas that are unused or already full of prot_numa
2253 * PTEs, scan up to virtpages, to skip through those
2257 pages -= (end - start) >> PAGE_SHIFT;
2258 virtpages -= (end - start) >> PAGE_SHIFT;
2261 if (pages <= 0 || virtpages <= 0)
2265 } while (end != vma->vm_end);
2270 * It is possible to reach the end of the VMA list but the last few
2271 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2272 * would find the !migratable VMA on the next scan but not reset the
2273 * scanner to the start so check it now.
2276 mm->numa_scan_offset = start;
2278 reset_ptenuma_scan(p);
2279 up_read(&mm->mmap_sem);
2283 * Drive the periodic memory faults..
2285 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2287 struct callback_head *work = &curr->numa_work;
2291 * We don't care about NUMA placement if we don't have memory.
2293 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2297 * Using runtime rather than walltime has the dual advantage that
2298 * we (mostly) drive the selection from busy threads and that the
2299 * task needs to have done some actual work before we bother with
2302 now = curr->se.sum_exec_runtime;
2303 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2305 if (now > curr->node_stamp + period) {
2306 if (!curr->node_stamp)
2307 curr->numa_scan_period = task_scan_min(curr);
2308 curr->node_stamp += period;
2310 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2311 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2312 task_work_add(curr, work, true);
2317 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2321 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2325 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2328 #endif /* CONFIG_NUMA_BALANCING */
2331 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2333 update_load_add(&cfs_rq->load, se->load.weight);
2334 if (!parent_entity(se))
2335 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2337 if (entity_is_task(se)) {
2338 struct rq *rq = rq_of(cfs_rq);
2340 account_numa_enqueue(rq, task_of(se));
2341 list_add(&se->group_node, &rq->cfs_tasks);
2344 cfs_rq->nr_running++;
2348 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2350 update_load_sub(&cfs_rq->load, se->load.weight);
2351 if (!parent_entity(se))
2352 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2353 if (entity_is_task(se)) {
2354 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2355 list_del_init(&se->group_node);
2357 cfs_rq->nr_running--;
2360 #ifdef CONFIG_FAIR_GROUP_SCHED
2362 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2367 * Use this CPU's real-time load instead of the last load contribution
2368 * as the updating of the contribution is delayed, and we will use the
2369 * the real-time load to calc the share. See update_tg_load_avg().
2371 tg_weight = atomic_long_read(&tg->load_avg);
2372 tg_weight -= cfs_rq->tg_load_avg_contrib;
2373 tg_weight += cfs_rq->load.weight;
2378 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2380 long tg_weight, load, shares;
2382 tg_weight = calc_tg_weight(tg, cfs_rq);
2383 load = cfs_rq->load.weight;
2385 shares = (tg->shares * load);
2387 shares /= tg_weight;
2389 if (shares < MIN_SHARES)
2390 shares = MIN_SHARES;
2391 if (shares > tg->shares)
2392 shares = tg->shares;
2396 # else /* CONFIG_SMP */
2397 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2401 # endif /* CONFIG_SMP */
2402 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2403 unsigned long weight)
2406 /* commit outstanding execution time */
2407 if (cfs_rq->curr == se)
2408 update_curr(cfs_rq);
2409 account_entity_dequeue(cfs_rq, se);
2412 update_load_set(&se->load, weight);
2415 account_entity_enqueue(cfs_rq, se);
2418 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2420 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2422 struct task_group *tg;
2423 struct sched_entity *se;
2427 se = tg->se[cpu_of(rq_of(cfs_rq))];
2428 if (!se || throttled_hierarchy(cfs_rq))
2431 if (likely(se->load.weight == tg->shares))
2434 shares = calc_cfs_shares(cfs_rq, tg);
2436 reweight_entity(cfs_rq_of(se), se, shares);
2438 #else /* CONFIG_FAIR_GROUP_SCHED */
2439 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2442 #endif /* CONFIG_FAIR_GROUP_SCHED */
2445 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2446 static const u32 runnable_avg_yN_inv[] = {
2447 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2448 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2449 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2450 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2451 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2452 0x85aac367, 0x82cd8698,
2456 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2457 * over-estimates when re-combining.
2459 static const u32 runnable_avg_yN_sum[] = {
2460 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2461 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2462 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2467 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2469 static __always_inline u64 decay_load(u64 val, u64 n)
2471 unsigned int local_n;
2475 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2478 /* after bounds checking we can collapse to 32-bit */
2482 * As y^PERIOD = 1/2, we can combine
2483 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2484 * With a look-up table which covers y^n (n<PERIOD)
2486 * To achieve constant time decay_load.
2488 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2489 val >>= local_n / LOAD_AVG_PERIOD;
2490 local_n %= LOAD_AVG_PERIOD;
2493 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2498 * For updates fully spanning n periods, the contribution to runnable
2499 * average will be: \Sum 1024*y^n
2501 * We can compute this reasonably efficiently by combining:
2502 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2504 static u32 __compute_runnable_contrib(u64 n)
2508 if (likely(n <= LOAD_AVG_PERIOD))
2509 return runnable_avg_yN_sum[n];
2510 else if (unlikely(n >= LOAD_AVG_MAX_N))
2511 return LOAD_AVG_MAX;
2513 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2515 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2516 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2518 n -= LOAD_AVG_PERIOD;
2519 } while (n > LOAD_AVG_PERIOD);
2521 contrib = decay_load(contrib, n);
2522 return contrib + runnable_avg_yN_sum[n];
2525 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2526 #error "load tracking assumes 2^10 as unit"
2529 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2532 * We can represent the historical contribution to runnable average as the
2533 * coefficients of a geometric series. To do this we sub-divide our runnable
2534 * history into segments of approximately 1ms (1024us); label the segment that
2535 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2537 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2539 * (now) (~1ms ago) (~2ms ago)
2541 * Let u_i denote the fraction of p_i that the entity was runnable.
2543 * We then designate the fractions u_i as our co-efficients, yielding the
2544 * following representation of historical load:
2545 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2547 * We choose y based on the with of a reasonably scheduling period, fixing:
2550 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2551 * approximately half as much as the contribution to load within the last ms
2554 * When a period "rolls over" and we have new u_0`, multiplying the previous
2555 * sum again by y is sufficient to update:
2556 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2557 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2559 static __always_inline int
2560 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2561 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2563 u64 delta, scaled_delta, periods;
2565 unsigned int delta_w, scaled_delta_w, decayed = 0;
2566 unsigned long scale_freq, scale_cpu;
2568 delta = now - sa->last_update_time;
2570 * This should only happen when time goes backwards, which it
2571 * unfortunately does during sched clock init when we swap over to TSC.
2573 if ((s64)delta < 0) {
2574 sa->last_update_time = now;
2579 * Use 1024ns as the unit of measurement since it's a reasonable
2580 * approximation of 1us and fast to compute.
2585 sa->last_update_time = now;
2587 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2588 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2590 /* delta_w is the amount already accumulated against our next period */
2591 delta_w = sa->period_contrib;
2592 if (delta + delta_w >= 1024) {
2595 /* how much left for next period will start over, we don't know yet */
2596 sa->period_contrib = 0;
2599 * Now that we know we're crossing a period boundary, figure
2600 * out how much from delta we need to complete the current
2601 * period and accrue it.
2603 delta_w = 1024 - delta_w;
2604 scaled_delta_w = cap_scale(delta_w, scale_freq);
2606 sa->load_sum += weight * scaled_delta_w;
2608 cfs_rq->runnable_load_sum +=
2609 weight * scaled_delta_w;
2613 sa->util_sum += scaled_delta_w * scale_cpu;
2617 /* Figure out how many additional periods this update spans */
2618 periods = delta / 1024;
2621 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2623 cfs_rq->runnable_load_sum =
2624 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2626 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2628 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2629 contrib = __compute_runnable_contrib(periods);
2630 contrib = cap_scale(contrib, scale_freq);
2632 sa->load_sum += weight * contrib;
2634 cfs_rq->runnable_load_sum += weight * contrib;
2637 sa->util_sum += contrib * scale_cpu;
2640 /* Remainder of delta accrued against u_0` */
2641 scaled_delta = cap_scale(delta, scale_freq);
2643 sa->load_sum += weight * scaled_delta;
2645 cfs_rq->runnable_load_sum += weight * scaled_delta;
2648 sa->util_sum += scaled_delta * scale_cpu;
2650 sa->period_contrib += delta;
2653 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2655 cfs_rq->runnable_load_avg =
2656 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2658 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2664 #ifdef CONFIG_FAIR_GROUP_SCHED
2666 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2667 * and effective_load (which is not done because it is too costly).
2669 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2671 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2673 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2674 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2675 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2679 #else /* CONFIG_FAIR_GROUP_SCHED */
2680 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2681 #endif /* CONFIG_FAIR_GROUP_SCHED */
2683 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2686 * Unsigned subtract and clamp on underflow.
2688 * Explicitly do a load-store to ensure the intermediate value never hits
2689 * memory. This allows lockless observations without ever seeing the negative
2692 #define sub_positive(_ptr, _val) do { \
2693 typeof(_ptr) ptr = (_ptr); \
2694 typeof(*ptr) val = (_val); \
2695 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2699 WRITE_ONCE(*ptr, res); \
2702 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2703 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2705 struct sched_avg *sa = &cfs_rq->avg;
2706 int decayed, removed = 0;
2708 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2709 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2710 sub_positive(&sa->load_avg, r);
2711 sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
2715 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2716 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2717 sub_positive(&sa->util_avg, r);
2718 sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
2721 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2722 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2724 #ifndef CONFIG_64BIT
2726 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2729 return decayed || removed;
2732 /* Update task and its cfs_rq load average */
2733 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2735 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2736 u64 now = cfs_rq_clock_task(cfs_rq);
2737 int cpu = cpu_of(rq_of(cfs_rq));
2740 * Track task load average for carrying it to new CPU after migrated, and
2741 * track group sched_entity load average for task_h_load calc in migration
2743 __update_load_avg(now, cpu, &se->avg,
2744 se->on_rq * scale_load_down(se->load.weight),
2745 cfs_rq->curr == se, NULL);
2747 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2748 update_tg_load_avg(cfs_rq, 0);
2751 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2753 if (!sched_feat(ATTACH_AGE_LOAD))
2757 * If we got migrated (either between CPUs or between cgroups) we'll
2758 * have aged the average right before clearing @last_update_time.
2760 if (se->avg.last_update_time) {
2761 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2762 &se->avg, 0, 0, NULL);
2765 * XXX: we could have just aged the entire load away if we've been
2766 * absent from the fair class for too long.
2771 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2772 cfs_rq->avg.load_avg += se->avg.load_avg;
2773 cfs_rq->avg.load_sum += se->avg.load_sum;
2774 cfs_rq->avg.util_avg += se->avg.util_avg;
2775 cfs_rq->avg.util_sum += se->avg.util_sum;
2778 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2780 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2781 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2782 cfs_rq->curr == se, NULL);
2784 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
2785 sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
2786 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
2787 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
2790 /* Add the load generated by se into cfs_rq's load average */
2792 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2794 struct sched_avg *sa = &se->avg;
2795 u64 now = cfs_rq_clock_task(cfs_rq);
2796 int migrated, decayed;
2798 migrated = !sa->last_update_time;
2800 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2801 se->on_rq * scale_load_down(se->load.weight),
2802 cfs_rq->curr == se, NULL);
2805 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2807 cfs_rq->runnable_load_avg += sa->load_avg;
2808 cfs_rq->runnable_load_sum += sa->load_sum;
2811 attach_entity_load_avg(cfs_rq, se);
2813 if (decayed || migrated)
2814 update_tg_load_avg(cfs_rq, 0);
2817 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2819 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2821 update_load_avg(se, 1);
2823 cfs_rq->runnable_load_avg =
2824 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2825 cfs_rq->runnable_load_sum =
2826 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2830 * Task first catches up with cfs_rq, and then subtract
2831 * itself from the cfs_rq (task must be off the queue now).
2833 void remove_entity_load_avg(struct sched_entity *se)
2835 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2836 u64 last_update_time;
2838 #ifndef CONFIG_64BIT
2839 u64 last_update_time_copy;
2842 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2844 last_update_time = cfs_rq->avg.last_update_time;
2845 } while (last_update_time != last_update_time_copy);
2847 last_update_time = cfs_rq->avg.last_update_time;
2850 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2851 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2852 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2856 * Update the rq's load with the elapsed running time before entering
2857 * idle. if the last scheduled task is not a CFS task, idle_enter will
2858 * be the only way to update the runnable statistic.
2860 void idle_enter_fair(struct rq *this_rq)
2865 * Update the rq's load with the elapsed idle time before a task is
2866 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2867 * be the only way to update the runnable statistic.
2869 void idle_exit_fair(struct rq *this_rq)
2873 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2875 return cfs_rq->runnable_load_avg;
2878 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2880 return cfs_rq->avg.load_avg;
2883 static int idle_balance(struct rq *this_rq);
2885 #else /* CONFIG_SMP */
2887 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2889 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2891 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2892 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2895 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2897 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2899 static inline int idle_balance(struct rq *rq)
2904 #endif /* CONFIG_SMP */
2906 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2908 #ifdef CONFIG_SCHEDSTATS
2909 struct task_struct *tsk = NULL;
2911 if (entity_is_task(se))
2914 if (se->statistics.sleep_start) {
2915 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2920 if (unlikely(delta > se->statistics.sleep_max))
2921 se->statistics.sleep_max = delta;
2923 se->statistics.sleep_start = 0;
2924 se->statistics.sum_sleep_runtime += delta;
2927 account_scheduler_latency(tsk, delta >> 10, 1);
2928 trace_sched_stat_sleep(tsk, delta);
2931 if (se->statistics.block_start) {
2932 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2937 if (unlikely(delta > se->statistics.block_max))
2938 se->statistics.block_max = delta;
2940 se->statistics.block_start = 0;
2941 se->statistics.sum_sleep_runtime += delta;
2944 if (tsk->in_iowait) {
2945 se->statistics.iowait_sum += delta;
2946 se->statistics.iowait_count++;
2947 trace_sched_stat_iowait(tsk, delta);
2950 trace_sched_stat_blocked(tsk, delta);
2953 * Blocking time is in units of nanosecs, so shift by
2954 * 20 to get a milliseconds-range estimation of the
2955 * amount of time that the task spent sleeping:
2957 if (unlikely(prof_on == SLEEP_PROFILING)) {
2958 profile_hits(SLEEP_PROFILING,
2959 (void *)get_wchan(tsk),
2962 account_scheduler_latency(tsk, delta >> 10, 0);
2968 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2970 #ifdef CONFIG_SCHED_DEBUG
2971 s64 d = se->vruntime - cfs_rq->min_vruntime;
2976 if (d > 3*sysctl_sched_latency)
2977 schedstat_inc(cfs_rq, nr_spread_over);
2982 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2984 u64 vruntime = cfs_rq->min_vruntime;
2987 * The 'current' period is already promised to the current tasks,
2988 * however the extra weight of the new task will slow them down a
2989 * little, place the new task so that it fits in the slot that
2990 * stays open at the end.
2992 if (initial && sched_feat(START_DEBIT))
2993 vruntime += sched_vslice(cfs_rq, se);
2995 /* sleeps up to a single latency don't count. */
2997 unsigned long thresh = sysctl_sched_latency;
3000 * Halve their sleep time's effect, to allow
3001 * for a gentler effect of sleepers:
3003 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3009 /* ensure we never gain time by being placed backwards. */
3010 se->vruntime = max_vruntime(se->vruntime, vruntime);
3013 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3016 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3019 * Update the normalized vruntime before updating min_vruntime
3020 * through calling update_curr().
3022 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3023 se->vruntime += cfs_rq->min_vruntime;
3026 * Update run-time statistics of the 'current'.
3028 update_curr(cfs_rq);
3029 enqueue_entity_load_avg(cfs_rq, se);
3030 account_entity_enqueue(cfs_rq, se);
3031 update_cfs_shares(cfs_rq);
3033 if (flags & ENQUEUE_WAKEUP) {
3034 place_entity(cfs_rq, se, 0);
3035 enqueue_sleeper(cfs_rq, se);
3038 update_stats_enqueue(cfs_rq, se);
3039 check_spread(cfs_rq, se);
3040 if (se != cfs_rq->curr)
3041 __enqueue_entity(cfs_rq, se);
3044 if (cfs_rq->nr_running == 1) {
3045 list_add_leaf_cfs_rq(cfs_rq);
3046 check_enqueue_throttle(cfs_rq);
3050 static void __clear_buddies_last(struct sched_entity *se)
3052 for_each_sched_entity(se) {
3053 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3054 if (cfs_rq->last != se)
3057 cfs_rq->last = NULL;
3061 static void __clear_buddies_next(struct sched_entity *se)
3063 for_each_sched_entity(se) {
3064 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3065 if (cfs_rq->next != se)
3068 cfs_rq->next = NULL;
3072 static void __clear_buddies_skip(struct sched_entity *se)
3074 for_each_sched_entity(se) {
3075 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3076 if (cfs_rq->skip != se)
3079 cfs_rq->skip = NULL;
3083 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3085 if (cfs_rq->last == se)
3086 __clear_buddies_last(se);
3088 if (cfs_rq->next == se)
3089 __clear_buddies_next(se);
3091 if (cfs_rq->skip == se)
3092 __clear_buddies_skip(se);
3095 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3098 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3101 * Update run-time statistics of the 'current'.
3103 update_curr(cfs_rq);
3104 dequeue_entity_load_avg(cfs_rq, se);
3106 update_stats_dequeue(cfs_rq, se);
3107 if (flags & DEQUEUE_SLEEP) {
3108 #ifdef CONFIG_SCHEDSTATS
3109 if (entity_is_task(se)) {
3110 struct task_struct *tsk = task_of(se);
3112 if (tsk->state & TASK_INTERRUPTIBLE)
3113 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3114 if (tsk->state & TASK_UNINTERRUPTIBLE)
3115 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3120 clear_buddies(cfs_rq, se);
3122 if (se != cfs_rq->curr)
3123 __dequeue_entity(cfs_rq, se);
3125 account_entity_dequeue(cfs_rq, se);
3128 * Normalize the entity after updating the min_vruntime because the
3129 * update can refer to the ->curr item and we need to reflect this
3130 * movement in our normalized position.
3132 if (!(flags & DEQUEUE_SLEEP))
3133 se->vruntime -= cfs_rq->min_vruntime;
3135 /* return excess runtime on last dequeue */
3136 return_cfs_rq_runtime(cfs_rq);
3138 update_min_vruntime(cfs_rq);
3139 update_cfs_shares(cfs_rq);
3143 * Preempt the current task with a newly woken task if needed:
3146 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3148 unsigned long ideal_runtime, delta_exec;
3149 struct sched_entity *se;
3152 ideal_runtime = sched_slice(cfs_rq, curr);
3153 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3154 if (delta_exec > ideal_runtime) {
3155 resched_curr(rq_of(cfs_rq));
3157 * The current task ran long enough, ensure it doesn't get
3158 * re-elected due to buddy favours.
3160 clear_buddies(cfs_rq, curr);
3165 * Ensure that a task that missed wakeup preemption by a
3166 * narrow margin doesn't have to wait for a full slice.
3167 * This also mitigates buddy induced latencies under load.
3169 if (delta_exec < sysctl_sched_min_granularity)
3172 se = __pick_first_entity(cfs_rq);
3173 delta = curr->vruntime - se->vruntime;
3178 if (delta > ideal_runtime)
3179 resched_curr(rq_of(cfs_rq));
3183 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3185 /* 'current' is not kept within the tree. */
3188 * Any task has to be enqueued before it get to execute on
3189 * a CPU. So account for the time it spent waiting on the
3192 update_stats_wait_end(cfs_rq, se);
3193 __dequeue_entity(cfs_rq, se);
3194 update_load_avg(se, 1);
3197 update_stats_curr_start(cfs_rq, se);
3199 #ifdef CONFIG_SCHEDSTATS
3201 * Track our maximum slice length, if the CPU's load is at
3202 * least twice that of our own weight (i.e. dont track it
3203 * when there are only lesser-weight tasks around):
3205 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3206 se->statistics.slice_max = max(se->statistics.slice_max,
3207 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3210 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3214 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3217 * Pick the next process, keeping these things in mind, in this order:
3218 * 1) keep things fair between processes/task groups
3219 * 2) pick the "next" process, since someone really wants that to run
3220 * 3) pick the "last" process, for cache locality
3221 * 4) do not run the "skip" process, if something else is available
3223 static struct sched_entity *
3224 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3226 struct sched_entity *left = __pick_first_entity(cfs_rq);
3227 struct sched_entity *se;
3230 * If curr is set we have to see if its left of the leftmost entity
3231 * still in the tree, provided there was anything in the tree at all.
3233 if (!left || (curr && entity_before(curr, left)))
3236 se = left; /* ideally we run the leftmost entity */
3239 * Avoid running the skip buddy, if running something else can
3240 * be done without getting too unfair.
3242 if (cfs_rq->skip == se) {
3243 struct sched_entity *second;
3246 second = __pick_first_entity(cfs_rq);
3248 second = __pick_next_entity(se);
3249 if (!second || (curr && entity_before(curr, second)))
3253 if (second && wakeup_preempt_entity(second, left) < 1)
3258 * Prefer last buddy, try to return the CPU to a preempted task.
3260 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3264 * Someone really wants this to run. If it's not unfair, run it.
3266 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3269 clear_buddies(cfs_rq, se);
3274 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3276 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3279 * If still on the runqueue then deactivate_task()
3280 * was not called and update_curr() has to be done:
3283 update_curr(cfs_rq);
3285 /* throttle cfs_rqs exceeding runtime */
3286 check_cfs_rq_runtime(cfs_rq);
3288 check_spread(cfs_rq, prev);
3290 update_stats_wait_start(cfs_rq, prev);
3291 /* Put 'current' back into the tree. */
3292 __enqueue_entity(cfs_rq, prev);
3293 /* in !on_rq case, update occurred at dequeue */
3294 update_load_avg(prev, 0);
3296 cfs_rq->curr = NULL;
3300 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3303 * Update run-time statistics of the 'current'.
3305 update_curr(cfs_rq);
3308 * Ensure that runnable average is periodically updated.
3310 update_load_avg(curr, 1);
3311 update_cfs_shares(cfs_rq);
3313 #ifdef CONFIG_SCHED_HRTICK
3315 * queued ticks are scheduled to match the slice, so don't bother
3316 * validating it and just reschedule.
3319 resched_curr(rq_of(cfs_rq));
3323 * don't let the period tick interfere with the hrtick preemption
3325 if (!sched_feat(DOUBLE_TICK) &&
3326 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3330 if (cfs_rq->nr_running > 1)
3331 check_preempt_tick(cfs_rq, curr);
3335 /**************************************************
3336 * CFS bandwidth control machinery
3339 #ifdef CONFIG_CFS_BANDWIDTH
3341 #ifdef HAVE_JUMP_LABEL
3342 static struct static_key __cfs_bandwidth_used;
3344 static inline bool cfs_bandwidth_used(void)
3346 return static_key_false(&__cfs_bandwidth_used);
3349 void cfs_bandwidth_usage_inc(void)
3351 static_key_slow_inc(&__cfs_bandwidth_used);
3354 void cfs_bandwidth_usage_dec(void)
3356 static_key_slow_dec(&__cfs_bandwidth_used);
3358 #else /* HAVE_JUMP_LABEL */
3359 static bool cfs_bandwidth_used(void)
3364 void cfs_bandwidth_usage_inc(void) {}
3365 void cfs_bandwidth_usage_dec(void) {}
3366 #endif /* HAVE_JUMP_LABEL */
3369 * default period for cfs group bandwidth.
3370 * default: 0.1s, units: nanoseconds
3372 static inline u64 default_cfs_period(void)
3374 return 100000000ULL;
3377 static inline u64 sched_cfs_bandwidth_slice(void)
3379 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3383 * Replenish runtime according to assigned quota and update expiration time.
3384 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3385 * additional synchronization around rq->lock.
3387 * requires cfs_b->lock
3389 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3393 if (cfs_b->quota == RUNTIME_INF)
3396 now = sched_clock_cpu(smp_processor_id());
3397 cfs_b->runtime = cfs_b->quota;
3398 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3401 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3403 return &tg->cfs_bandwidth;
3406 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3407 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3409 if (unlikely(cfs_rq->throttle_count))
3410 return cfs_rq->throttled_clock_task;
3412 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3415 /* returns 0 on failure to allocate runtime */
3416 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3418 struct task_group *tg = cfs_rq->tg;
3419 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3420 u64 amount = 0, min_amount, expires;
3422 /* note: this is a positive sum as runtime_remaining <= 0 */
3423 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3425 raw_spin_lock(&cfs_b->lock);
3426 if (cfs_b->quota == RUNTIME_INF)
3427 amount = min_amount;
3429 start_cfs_bandwidth(cfs_b);
3431 if (cfs_b->runtime > 0) {
3432 amount = min(cfs_b->runtime, min_amount);
3433 cfs_b->runtime -= amount;
3437 expires = cfs_b->runtime_expires;
3438 raw_spin_unlock(&cfs_b->lock);
3440 cfs_rq->runtime_remaining += amount;
3442 * we may have advanced our local expiration to account for allowed
3443 * spread between our sched_clock and the one on which runtime was
3446 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3447 cfs_rq->runtime_expires = expires;
3449 return cfs_rq->runtime_remaining > 0;
3453 * Note: This depends on the synchronization provided by sched_clock and the
3454 * fact that rq->clock snapshots this value.
3456 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3458 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3460 /* if the deadline is ahead of our clock, nothing to do */
3461 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3464 if (cfs_rq->runtime_remaining < 0)
3468 * If the local deadline has passed we have to consider the
3469 * possibility that our sched_clock is 'fast' and the global deadline
3470 * has not truly expired.
3472 * Fortunately we can check determine whether this the case by checking
3473 * whether the global deadline has advanced. It is valid to compare
3474 * cfs_b->runtime_expires without any locks since we only care about
3475 * exact equality, so a partial write will still work.
3478 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3479 /* extend local deadline, drift is bounded above by 2 ticks */
3480 cfs_rq->runtime_expires += TICK_NSEC;
3482 /* global deadline is ahead, expiration has passed */
3483 cfs_rq->runtime_remaining = 0;
3487 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3489 /* dock delta_exec before expiring quota (as it could span periods) */
3490 cfs_rq->runtime_remaining -= delta_exec;
3491 expire_cfs_rq_runtime(cfs_rq);
3493 if (likely(cfs_rq->runtime_remaining > 0))
3497 * if we're unable to extend our runtime we resched so that the active
3498 * hierarchy can be throttled
3500 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3501 resched_curr(rq_of(cfs_rq));
3504 static __always_inline
3505 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3507 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3510 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3513 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3515 return cfs_bandwidth_used() && cfs_rq->throttled;
3518 /* check whether cfs_rq, or any parent, is throttled */
3519 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3521 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3525 * Ensure that neither of the group entities corresponding to src_cpu or
3526 * dest_cpu are members of a throttled hierarchy when performing group
3527 * load-balance operations.
3529 static inline int throttled_lb_pair(struct task_group *tg,
3530 int src_cpu, int dest_cpu)
3532 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3534 src_cfs_rq = tg->cfs_rq[src_cpu];
3535 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3537 return throttled_hierarchy(src_cfs_rq) ||
3538 throttled_hierarchy(dest_cfs_rq);
3541 /* updated child weight may affect parent so we have to do this bottom up */
3542 static int tg_unthrottle_up(struct task_group *tg, void *data)
3544 struct rq *rq = data;
3545 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3547 cfs_rq->throttle_count--;
3549 if (!cfs_rq->throttle_count) {
3550 /* adjust cfs_rq_clock_task() */
3551 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3552 cfs_rq->throttled_clock_task;
3559 static int tg_throttle_down(struct task_group *tg, void *data)
3561 struct rq *rq = data;
3562 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3564 /* group is entering throttled state, stop time */
3565 if (!cfs_rq->throttle_count)
3566 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3567 cfs_rq->throttle_count++;
3572 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3574 struct rq *rq = rq_of(cfs_rq);
3575 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3576 struct sched_entity *se;
3577 long task_delta, dequeue = 1;
3580 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3582 /* freeze hierarchy runnable averages while throttled */
3584 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3587 task_delta = cfs_rq->h_nr_running;
3588 for_each_sched_entity(se) {
3589 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3590 /* throttled entity or throttle-on-deactivate */
3595 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3596 qcfs_rq->h_nr_running -= task_delta;
3598 if (qcfs_rq->load.weight)
3603 sub_nr_running(rq, task_delta);
3605 cfs_rq->throttled = 1;
3606 cfs_rq->throttled_clock = rq_clock(rq);
3607 raw_spin_lock(&cfs_b->lock);
3608 empty = list_empty(&cfs_b->throttled_cfs_rq);
3611 * Add to the _head_ of the list, so that an already-started
3612 * distribute_cfs_runtime will not see us
3614 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3617 * If we're the first throttled task, make sure the bandwidth
3621 start_cfs_bandwidth(cfs_b);
3623 raw_spin_unlock(&cfs_b->lock);
3626 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3628 struct rq *rq = rq_of(cfs_rq);
3629 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3630 struct sched_entity *se;
3634 se = cfs_rq->tg->se[cpu_of(rq)];
3636 cfs_rq->throttled = 0;
3638 update_rq_clock(rq);
3640 raw_spin_lock(&cfs_b->lock);
3641 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3642 list_del_rcu(&cfs_rq->throttled_list);
3643 raw_spin_unlock(&cfs_b->lock);
3645 /* update hierarchical throttle state */
3646 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3648 if (!cfs_rq->load.weight)
3651 task_delta = cfs_rq->h_nr_running;
3652 for_each_sched_entity(se) {
3656 cfs_rq = cfs_rq_of(se);
3658 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3659 cfs_rq->h_nr_running += task_delta;
3661 if (cfs_rq_throttled(cfs_rq))
3666 add_nr_running(rq, task_delta);
3668 /* determine whether we need to wake up potentially idle cpu */
3669 if (rq->curr == rq->idle && rq->cfs.nr_running)
3673 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3674 u64 remaining, u64 expires)
3676 struct cfs_rq *cfs_rq;
3678 u64 starting_runtime = remaining;
3681 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3683 struct rq *rq = rq_of(cfs_rq);
3685 raw_spin_lock(&rq->lock);
3686 if (!cfs_rq_throttled(cfs_rq))
3689 runtime = -cfs_rq->runtime_remaining + 1;
3690 if (runtime > remaining)
3691 runtime = remaining;
3692 remaining -= runtime;
3694 cfs_rq->runtime_remaining += runtime;
3695 cfs_rq->runtime_expires = expires;
3697 /* we check whether we're throttled above */
3698 if (cfs_rq->runtime_remaining > 0)
3699 unthrottle_cfs_rq(cfs_rq);
3702 raw_spin_unlock(&rq->lock);
3709 return starting_runtime - remaining;
3713 * Responsible for refilling a task_group's bandwidth and unthrottling its
3714 * cfs_rqs as appropriate. If there has been no activity within the last
3715 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3716 * used to track this state.
3718 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3720 u64 runtime, runtime_expires;
3723 /* no need to continue the timer with no bandwidth constraint */
3724 if (cfs_b->quota == RUNTIME_INF)
3725 goto out_deactivate;
3727 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3728 cfs_b->nr_periods += overrun;
3731 * idle depends on !throttled (for the case of a large deficit), and if
3732 * we're going inactive then everything else can be deferred
3734 if (cfs_b->idle && !throttled)
3735 goto out_deactivate;
3737 __refill_cfs_bandwidth_runtime(cfs_b);
3740 /* mark as potentially idle for the upcoming period */
3745 /* account preceding periods in which throttling occurred */
3746 cfs_b->nr_throttled += overrun;
3748 runtime_expires = cfs_b->runtime_expires;
3751 * This check is repeated as we are holding onto the new bandwidth while
3752 * we unthrottle. This can potentially race with an unthrottled group
3753 * trying to acquire new bandwidth from the global pool. This can result
3754 * in us over-using our runtime if it is all used during this loop, but
3755 * only by limited amounts in that extreme case.
3757 while (throttled && cfs_b->runtime > 0) {
3758 runtime = cfs_b->runtime;
3759 raw_spin_unlock(&cfs_b->lock);
3760 /* we can't nest cfs_b->lock while distributing bandwidth */
3761 runtime = distribute_cfs_runtime(cfs_b, runtime,
3763 raw_spin_lock(&cfs_b->lock);
3765 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3767 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3771 * While we are ensured activity in the period following an
3772 * unthrottle, this also covers the case in which the new bandwidth is
3773 * insufficient to cover the existing bandwidth deficit. (Forcing the
3774 * timer to remain active while there are any throttled entities.)
3784 /* a cfs_rq won't donate quota below this amount */
3785 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3786 /* minimum remaining period time to redistribute slack quota */
3787 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3788 /* how long we wait to gather additional slack before distributing */
3789 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3792 * Are we near the end of the current quota period?
3794 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3795 * hrtimer base being cleared by hrtimer_start. In the case of
3796 * migrate_hrtimers, base is never cleared, so we are fine.
3798 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3800 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3803 /* if the call-back is running a quota refresh is already occurring */
3804 if (hrtimer_callback_running(refresh_timer))
3807 /* is a quota refresh about to occur? */
3808 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3809 if (remaining < min_expire)
3815 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3817 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3819 /* if there's a quota refresh soon don't bother with slack */
3820 if (runtime_refresh_within(cfs_b, min_left))
3823 hrtimer_start(&cfs_b->slack_timer,
3824 ns_to_ktime(cfs_bandwidth_slack_period),
3828 /* we know any runtime found here is valid as update_curr() precedes return */
3829 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3831 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3832 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3834 if (slack_runtime <= 0)
3837 raw_spin_lock(&cfs_b->lock);
3838 if (cfs_b->quota != RUNTIME_INF &&
3839 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3840 cfs_b->runtime += slack_runtime;
3842 /* we are under rq->lock, defer unthrottling using a timer */
3843 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3844 !list_empty(&cfs_b->throttled_cfs_rq))
3845 start_cfs_slack_bandwidth(cfs_b);
3847 raw_spin_unlock(&cfs_b->lock);
3849 /* even if it's not valid for return we don't want to try again */
3850 cfs_rq->runtime_remaining -= slack_runtime;
3853 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3855 if (!cfs_bandwidth_used())
3858 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3861 __return_cfs_rq_runtime(cfs_rq);
3865 * This is done with a timer (instead of inline with bandwidth return) since
3866 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3868 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3870 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3873 /* confirm we're still not at a refresh boundary */
3874 raw_spin_lock(&cfs_b->lock);
3875 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3876 raw_spin_unlock(&cfs_b->lock);
3880 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3881 runtime = cfs_b->runtime;
3883 expires = cfs_b->runtime_expires;
3884 raw_spin_unlock(&cfs_b->lock);
3889 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3891 raw_spin_lock(&cfs_b->lock);
3892 if (expires == cfs_b->runtime_expires)
3893 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3894 raw_spin_unlock(&cfs_b->lock);
3898 * When a group wakes up we want to make sure that its quota is not already
3899 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3900 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3902 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3904 if (!cfs_bandwidth_used())
3907 /* an active group must be handled by the update_curr()->put() path */
3908 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3911 /* ensure the group is not already throttled */
3912 if (cfs_rq_throttled(cfs_rq))
3915 /* update runtime allocation */
3916 account_cfs_rq_runtime(cfs_rq, 0);
3917 if (cfs_rq->runtime_remaining <= 0)
3918 throttle_cfs_rq(cfs_rq);
3921 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3922 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3924 if (!cfs_bandwidth_used())
3927 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3931 * it's possible for a throttled entity to be forced into a running
3932 * state (e.g. set_curr_task), in this case we're finished.
3934 if (cfs_rq_throttled(cfs_rq))
3937 throttle_cfs_rq(cfs_rq);
3941 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3943 struct cfs_bandwidth *cfs_b =
3944 container_of(timer, struct cfs_bandwidth, slack_timer);
3946 do_sched_cfs_slack_timer(cfs_b);
3948 return HRTIMER_NORESTART;
3951 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3953 struct cfs_bandwidth *cfs_b =
3954 container_of(timer, struct cfs_bandwidth, period_timer);
3958 raw_spin_lock(&cfs_b->lock);
3960 overrun = hrtimer_forward_now(timer, cfs_b->period);
3964 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3967 cfs_b->period_active = 0;
3968 raw_spin_unlock(&cfs_b->lock);
3970 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3973 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3975 raw_spin_lock_init(&cfs_b->lock);
3977 cfs_b->quota = RUNTIME_INF;
3978 cfs_b->period = ns_to_ktime(default_cfs_period());
3980 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3981 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3982 cfs_b->period_timer.function = sched_cfs_period_timer;
3983 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3984 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3987 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3989 cfs_rq->runtime_enabled = 0;
3990 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3993 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3995 lockdep_assert_held(&cfs_b->lock);
3997 if (!cfs_b->period_active) {
3998 cfs_b->period_active = 1;
3999 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4000 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4004 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4006 /* init_cfs_bandwidth() was not called */
4007 if (!cfs_b->throttled_cfs_rq.next)
4010 hrtimer_cancel(&cfs_b->period_timer);
4011 hrtimer_cancel(&cfs_b->slack_timer);
4014 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4016 struct cfs_rq *cfs_rq;
4018 for_each_leaf_cfs_rq(rq, cfs_rq) {
4019 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4021 raw_spin_lock(&cfs_b->lock);
4022 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4023 raw_spin_unlock(&cfs_b->lock);
4027 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4029 struct cfs_rq *cfs_rq;
4031 for_each_leaf_cfs_rq(rq, cfs_rq) {
4032 if (!cfs_rq->runtime_enabled)
4036 * clock_task is not advancing so we just need to make sure
4037 * there's some valid quota amount
4039 cfs_rq->runtime_remaining = 1;
4041 * Offline rq is schedulable till cpu is completely disabled
4042 * in take_cpu_down(), so we prevent new cfs throttling here.
4044 cfs_rq->runtime_enabled = 0;
4046 if (cfs_rq_throttled(cfs_rq))
4047 unthrottle_cfs_rq(cfs_rq);
4051 #else /* CONFIG_CFS_BANDWIDTH */
4052 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4054 return rq_clock_task(rq_of(cfs_rq));
4057 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4058 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4059 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4060 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4062 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4067 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4072 static inline int throttled_lb_pair(struct task_group *tg,
4073 int src_cpu, int dest_cpu)
4078 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4080 #ifdef CONFIG_FAIR_GROUP_SCHED
4081 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4084 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4088 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4089 static inline void update_runtime_enabled(struct rq *rq) {}
4090 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4092 #endif /* CONFIG_CFS_BANDWIDTH */
4094 /**************************************************
4095 * CFS operations on tasks:
4098 #ifdef CONFIG_SCHED_HRTICK
4099 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4101 struct sched_entity *se = &p->se;
4102 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4104 WARN_ON(task_rq(p) != rq);
4106 if (cfs_rq->nr_running > 1) {
4107 u64 slice = sched_slice(cfs_rq, se);
4108 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4109 s64 delta = slice - ran;
4116 hrtick_start(rq, delta);
4121 * called from enqueue/dequeue and updates the hrtick when the
4122 * current task is from our class and nr_running is low enough
4125 static void hrtick_update(struct rq *rq)
4127 struct task_struct *curr = rq->curr;
4129 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4132 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4133 hrtick_start_fair(rq, curr);
4135 #else /* !CONFIG_SCHED_HRTICK */
4137 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4141 static inline void hrtick_update(struct rq *rq)
4147 * The enqueue_task method is called before nr_running is
4148 * increased. Here we update the fair scheduling stats and
4149 * then put the task into the rbtree:
4152 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4154 struct cfs_rq *cfs_rq;
4155 struct sched_entity *se = &p->se;
4157 for_each_sched_entity(se) {
4160 cfs_rq = cfs_rq_of(se);
4161 enqueue_entity(cfs_rq, se, flags);
4164 * end evaluation on encountering a throttled cfs_rq
4166 * note: in the case of encountering a throttled cfs_rq we will
4167 * post the final h_nr_running increment below.
4169 if (cfs_rq_throttled(cfs_rq))
4171 cfs_rq->h_nr_running++;
4173 flags = ENQUEUE_WAKEUP;
4176 for_each_sched_entity(se) {
4177 cfs_rq = cfs_rq_of(se);
4178 cfs_rq->h_nr_running++;
4180 if (cfs_rq_throttled(cfs_rq))
4183 update_load_avg(se, 1);
4184 update_cfs_shares(cfs_rq);
4188 add_nr_running(rq, 1);
4193 static void set_next_buddy(struct sched_entity *se);
4196 * The dequeue_task method is called before nr_running is
4197 * decreased. We remove the task from the rbtree and
4198 * update the fair scheduling stats:
4200 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4202 struct cfs_rq *cfs_rq;
4203 struct sched_entity *se = &p->se;
4204 int task_sleep = flags & DEQUEUE_SLEEP;
4206 for_each_sched_entity(se) {
4207 cfs_rq = cfs_rq_of(se);
4208 dequeue_entity(cfs_rq, se, flags);
4211 * end evaluation on encountering a throttled cfs_rq
4213 * note: in the case of encountering a throttled cfs_rq we will
4214 * post the final h_nr_running decrement below.
4216 if (cfs_rq_throttled(cfs_rq))
4218 cfs_rq->h_nr_running--;
4220 /* Don't dequeue parent if it has other entities besides us */
4221 if (cfs_rq->load.weight) {
4223 * Bias pick_next to pick a task from this cfs_rq, as
4224 * p is sleeping when it is within its sched_slice.
4226 if (task_sleep && parent_entity(se))
4227 set_next_buddy(parent_entity(se));
4229 /* avoid re-evaluating load for this entity */
4230 se = parent_entity(se);
4233 flags |= DEQUEUE_SLEEP;
4236 for_each_sched_entity(se) {
4237 cfs_rq = cfs_rq_of(se);
4238 cfs_rq->h_nr_running--;
4240 if (cfs_rq_throttled(cfs_rq))
4243 update_load_avg(se, 1);
4244 update_cfs_shares(cfs_rq);
4248 sub_nr_running(rq, 1);
4256 * per rq 'load' arrray crap; XXX kill this.
4260 * The exact cpuload at various idx values, calculated at every tick would be
4261 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4263 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4264 * on nth tick when cpu may be busy, then we have:
4265 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4266 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4268 * decay_load_missed() below does efficient calculation of
4269 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4270 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4272 * The calculation is approximated on a 128 point scale.
4273 * degrade_zero_ticks is the number of ticks after which load at any
4274 * particular idx is approximated to be zero.
4275 * degrade_factor is a precomputed table, a row for each load idx.
4276 * Each column corresponds to degradation factor for a power of two ticks,
4277 * based on 128 point scale.
4279 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4280 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4282 * With this power of 2 load factors, we can degrade the load n times
4283 * by looking at 1 bits in n and doing as many mult/shift instead of
4284 * n mult/shifts needed by the exact degradation.
4286 #define DEGRADE_SHIFT 7
4287 static const unsigned char
4288 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4289 static const unsigned char
4290 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4291 {0, 0, 0, 0, 0, 0, 0, 0},
4292 {64, 32, 8, 0, 0, 0, 0, 0},
4293 {96, 72, 40, 12, 1, 0, 0},
4294 {112, 98, 75, 43, 15, 1, 0},
4295 {120, 112, 98, 76, 45, 16, 2} };
4298 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4299 * would be when CPU is idle and so we just decay the old load without
4300 * adding any new load.
4302 static unsigned long
4303 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4307 if (!missed_updates)
4310 if (missed_updates >= degrade_zero_ticks[idx])
4314 return load >> missed_updates;
4316 while (missed_updates) {
4317 if (missed_updates % 2)
4318 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4320 missed_updates >>= 1;
4327 * Update rq->cpu_load[] statistics. This function is usually called every
4328 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4329 * every tick. We fix it up based on jiffies.
4331 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4332 unsigned long pending_updates)
4336 this_rq->nr_load_updates++;
4338 /* Update our load: */
4339 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4340 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4341 unsigned long old_load, new_load;
4343 /* scale is effectively 1 << i now, and >> i divides by scale */
4345 old_load = this_rq->cpu_load[i];
4346 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4347 new_load = this_load;
4349 * Round up the averaging division if load is increasing. This
4350 * prevents us from getting stuck on 9 if the load is 10, for
4353 if (new_load > old_load)
4354 new_load += scale - 1;
4356 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4359 sched_avg_update(this_rq);
4362 /* Used instead of source_load when we know the type == 0 */
4363 static unsigned long weighted_cpuload(const int cpu)
4365 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4368 #ifdef CONFIG_NO_HZ_COMMON
4370 * There is no sane way to deal with nohz on smp when using jiffies because the
4371 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4372 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4374 * Therefore we cannot use the delta approach from the regular tick since that
4375 * would seriously skew the load calculation. However we'll make do for those
4376 * updates happening while idle (nohz_idle_balance) or coming out of idle
4377 * (tick_nohz_idle_exit).
4379 * This means we might still be one tick off for nohz periods.
4383 * Called from nohz_idle_balance() to update the load ratings before doing the
4386 static void update_idle_cpu_load(struct rq *this_rq)
4388 unsigned long curr_jiffies = READ_ONCE(jiffies);
4389 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4390 unsigned long pending_updates;
4393 * bail if there's load or we're actually up-to-date.
4395 if (load || curr_jiffies == this_rq->last_load_update_tick)
4398 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4399 this_rq->last_load_update_tick = curr_jiffies;
4401 __update_cpu_load(this_rq, load, pending_updates);
4405 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4407 void update_cpu_load_nohz(void)
4409 struct rq *this_rq = this_rq();
4410 unsigned long curr_jiffies = READ_ONCE(jiffies);
4411 unsigned long pending_updates;
4413 if (curr_jiffies == this_rq->last_load_update_tick)
4416 raw_spin_lock(&this_rq->lock);
4417 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4418 if (pending_updates) {
4419 this_rq->last_load_update_tick = curr_jiffies;
4421 * We were idle, this means load 0, the current load might be
4422 * !0 due to remote wakeups and the sort.
4424 __update_cpu_load(this_rq, 0, pending_updates);
4426 raw_spin_unlock(&this_rq->lock);
4428 #endif /* CONFIG_NO_HZ */
4431 * Called from scheduler_tick()
4433 void update_cpu_load_active(struct rq *this_rq)
4435 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4437 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4439 this_rq->last_load_update_tick = jiffies;
4440 __update_cpu_load(this_rq, load, 1);
4444 * Return a low guess at the load of a migration-source cpu weighted
4445 * according to the scheduling class and "nice" value.
4447 * We want to under-estimate the load of migration sources, to
4448 * balance conservatively.
4450 static unsigned long source_load(int cpu, int type)
4452 struct rq *rq = cpu_rq(cpu);
4453 unsigned long total = weighted_cpuload(cpu);
4455 if (type == 0 || !sched_feat(LB_BIAS))
4458 return min(rq->cpu_load[type-1], total);
4462 * Return a high guess at the load of a migration-target cpu weighted
4463 * according to the scheduling class and "nice" value.
4465 static unsigned long target_load(int cpu, int type)
4467 struct rq *rq = cpu_rq(cpu);
4468 unsigned long total = weighted_cpuload(cpu);
4470 if (type == 0 || !sched_feat(LB_BIAS))
4473 return max(rq->cpu_load[type-1], total);
4476 static unsigned long capacity_of(int cpu)
4478 return cpu_rq(cpu)->cpu_capacity;
4481 static unsigned long capacity_orig_of(int cpu)
4483 return cpu_rq(cpu)->cpu_capacity_orig;
4486 static unsigned long cpu_avg_load_per_task(int cpu)
4488 struct rq *rq = cpu_rq(cpu);
4489 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4490 unsigned long load_avg = weighted_cpuload(cpu);
4493 return load_avg / nr_running;
4498 static void record_wakee(struct task_struct *p)
4501 * Rough decay (wiping) for cost saving, don't worry
4502 * about the boundary, really active task won't care
4505 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4506 current->wakee_flips >>= 1;
4507 current->wakee_flip_decay_ts = jiffies;
4510 if (current->last_wakee != p) {
4511 current->last_wakee = p;
4512 current->wakee_flips++;
4516 static void task_waking_fair(struct task_struct *p)
4518 struct sched_entity *se = &p->se;
4519 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4522 #ifndef CONFIG_64BIT
4523 u64 min_vruntime_copy;
4526 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4528 min_vruntime = cfs_rq->min_vruntime;
4529 } while (min_vruntime != min_vruntime_copy);
4531 min_vruntime = cfs_rq->min_vruntime;
4534 se->vruntime -= min_vruntime;
4538 #ifdef CONFIG_FAIR_GROUP_SCHED
4540 * effective_load() calculates the load change as seen from the root_task_group
4542 * Adding load to a group doesn't make a group heavier, but can cause movement
4543 * of group shares between cpus. Assuming the shares were perfectly aligned one
4544 * can calculate the shift in shares.
4546 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4547 * on this @cpu and results in a total addition (subtraction) of @wg to the
4548 * total group weight.
4550 * Given a runqueue weight distribution (rw_i) we can compute a shares
4551 * distribution (s_i) using:
4553 * s_i = rw_i / \Sum rw_j (1)
4555 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4556 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4557 * shares distribution (s_i):
4559 * rw_i = { 2, 4, 1, 0 }
4560 * s_i = { 2/7, 4/7, 1/7, 0 }
4562 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4563 * task used to run on and the CPU the waker is running on), we need to
4564 * compute the effect of waking a task on either CPU and, in case of a sync
4565 * wakeup, compute the effect of the current task going to sleep.
4567 * So for a change of @wl to the local @cpu with an overall group weight change
4568 * of @wl we can compute the new shares distribution (s'_i) using:
4570 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4572 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4573 * differences in waking a task to CPU 0. The additional task changes the
4574 * weight and shares distributions like:
4576 * rw'_i = { 3, 4, 1, 0 }
4577 * s'_i = { 3/8, 4/8, 1/8, 0 }
4579 * We can then compute the difference in effective weight by using:
4581 * dw_i = S * (s'_i - s_i) (3)
4583 * Where 'S' is the group weight as seen by its parent.
4585 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4586 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4587 * 4/7) times the weight of the group.
4589 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4591 struct sched_entity *se = tg->se[cpu];
4593 if (!tg->parent) /* the trivial, non-cgroup case */
4596 for_each_sched_entity(se) {
4602 * W = @wg + \Sum rw_j
4604 W = wg + calc_tg_weight(tg, se->my_q);
4609 w = cfs_rq_load_avg(se->my_q) + wl;
4612 * wl = S * s'_i; see (2)
4615 wl = (w * (long)tg->shares) / W;
4620 * Per the above, wl is the new se->load.weight value; since
4621 * those are clipped to [MIN_SHARES, ...) do so now. See
4622 * calc_cfs_shares().
4624 if (wl < MIN_SHARES)
4628 * wl = dw_i = S * (s'_i - s_i); see (3)
4630 wl -= se->avg.load_avg;
4633 * Recursively apply this logic to all parent groups to compute
4634 * the final effective load change on the root group. Since
4635 * only the @tg group gets extra weight, all parent groups can
4636 * only redistribute existing shares. @wl is the shift in shares
4637 * resulting from this level per the above.
4646 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4654 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4655 * A waker of many should wake a different task than the one last awakened
4656 * at a frequency roughly N times higher than one of its wakees. In order
4657 * to determine whether we should let the load spread vs consolodating to
4658 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4659 * partner, and a factor of lls_size higher frequency in the other. With
4660 * both conditions met, we can be relatively sure that the relationship is
4661 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4662 * being client/server, worker/dispatcher, interrupt source or whatever is
4663 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4665 static int wake_wide(struct task_struct *p)
4667 unsigned int master = current->wakee_flips;
4668 unsigned int slave = p->wakee_flips;
4669 int factor = this_cpu_read(sd_llc_size);
4672 swap(master, slave);
4673 if (slave < factor || master < slave * factor)
4678 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4680 s64 this_load, load;
4681 s64 this_eff_load, prev_eff_load;
4682 int idx, this_cpu, prev_cpu;
4683 struct task_group *tg;
4684 unsigned long weight;
4688 this_cpu = smp_processor_id();
4689 prev_cpu = task_cpu(p);
4690 load = source_load(prev_cpu, idx);
4691 this_load = target_load(this_cpu, idx);
4694 * If sync wakeup then subtract the (maximum possible)
4695 * effect of the currently running task from the load
4696 * of the current CPU:
4699 tg = task_group(current);
4700 weight = current->se.avg.load_avg;
4702 this_load += effective_load(tg, this_cpu, -weight, -weight);
4703 load += effective_load(tg, prev_cpu, 0, -weight);
4707 weight = p->se.avg.load_avg;
4710 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4711 * due to the sync cause above having dropped this_load to 0, we'll
4712 * always have an imbalance, but there's really nothing you can do
4713 * about that, so that's good too.
4715 * Otherwise check if either cpus are near enough in load to allow this
4716 * task to be woken on this_cpu.
4718 this_eff_load = 100;
4719 this_eff_load *= capacity_of(prev_cpu);
4721 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4722 prev_eff_load *= capacity_of(this_cpu);
4724 if (this_load > 0) {
4725 this_eff_load *= this_load +
4726 effective_load(tg, this_cpu, weight, weight);
4728 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4731 balanced = this_eff_load <= prev_eff_load;
4733 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4738 schedstat_inc(sd, ttwu_move_affine);
4739 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4745 * find_idlest_group finds and returns the least busy CPU group within the
4748 static struct sched_group *
4749 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4750 int this_cpu, int sd_flag)
4752 struct sched_group *idlest = NULL, *group = sd->groups;
4753 unsigned long min_load = ULONG_MAX, this_load = 0;
4754 int load_idx = sd->forkexec_idx;
4755 int imbalance = 100 + (sd->imbalance_pct-100)/2;
4757 if (sd_flag & SD_BALANCE_WAKE)
4758 load_idx = sd->wake_idx;
4761 unsigned long load, avg_load;
4765 /* Skip over this group if it has no CPUs allowed */
4766 if (!cpumask_intersects(sched_group_cpus(group),
4767 tsk_cpus_allowed(p)))
4770 local_group = cpumask_test_cpu(this_cpu,
4771 sched_group_cpus(group));
4773 /* Tally up the load of all CPUs in the group */
4776 for_each_cpu(i, sched_group_cpus(group)) {
4777 /* Bias balancing toward cpus of our domain */
4779 load = source_load(i, load_idx);
4781 load = target_load(i, load_idx);
4786 /* Adjust by relative CPU capacity of the group */
4787 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4790 this_load = avg_load;
4791 } else if (avg_load < min_load) {
4792 min_load = avg_load;
4795 } while (group = group->next, group != sd->groups);
4797 if (!idlest || 100*this_load < imbalance*min_load)
4803 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4806 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4808 unsigned long load, min_load = ULONG_MAX;
4809 unsigned int min_exit_latency = UINT_MAX;
4810 u64 latest_idle_timestamp = 0;
4811 int least_loaded_cpu = this_cpu;
4812 int shallowest_idle_cpu = -1;
4815 /* Traverse only the allowed CPUs */
4816 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4818 struct rq *rq = cpu_rq(i);
4819 struct cpuidle_state *idle = idle_get_state(rq);
4820 if (idle && idle->exit_latency < min_exit_latency) {
4822 * We give priority to a CPU whose idle state
4823 * has the smallest exit latency irrespective
4824 * of any idle timestamp.
4826 min_exit_latency = idle->exit_latency;
4827 latest_idle_timestamp = rq->idle_stamp;
4828 shallowest_idle_cpu = i;
4829 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
4830 rq->idle_stamp > latest_idle_timestamp) {
4832 * If equal or no active idle state, then
4833 * the most recently idled CPU might have
4836 latest_idle_timestamp = rq->idle_stamp;
4837 shallowest_idle_cpu = i;
4839 } else if (shallowest_idle_cpu == -1) {
4840 load = weighted_cpuload(i);
4841 if (load < min_load || (load == min_load && i == this_cpu)) {
4843 least_loaded_cpu = i;
4848 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4852 * Try and locate an idle CPU in the sched_domain.
4854 static int select_idle_sibling(struct task_struct *p, int target)
4856 struct sched_domain *sd;
4857 struct sched_group *sg;
4858 int i = task_cpu(p);
4860 if (idle_cpu(target))
4864 * If the prevous cpu is cache affine and idle, don't be stupid.
4866 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4870 * Otherwise, iterate the domains and find an elegible idle cpu.
4872 sd = rcu_dereference(per_cpu(sd_llc, target));
4873 for_each_lower_domain(sd) {
4876 if (!cpumask_intersects(sched_group_cpus(sg),
4877 tsk_cpus_allowed(p)))
4880 for_each_cpu(i, sched_group_cpus(sg)) {
4881 if (i == target || !idle_cpu(i))
4885 target = cpumask_first_and(sched_group_cpus(sg),
4886 tsk_cpus_allowed(p));
4890 } while (sg != sd->groups);
4897 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4898 * tasks. The unit of the return value must be the one of capacity so we can
4899 * compare the utilization with the capacity of the CPU that is available for
4900 * CFS task (ie cpu_capacity).
4902 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
4903 * recent utilization of currently non-runnable tasks on a CPU. It represents
4904 * the amount of utilization of a CPU in the range [0..capacity_orig] where
4905 * capacity_orig is the cpu_capacity available at the highest frequency
4906 * (arch_scale_freq_capacity()).
4907 * The utilization of a CPU converges towards a sum equal to or less than the
4908 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
4909 * the running time on this CPU scaled by capacity_curr.
4911 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
4912 * higher than capacity_orig because of unfortunate rounding in
4913 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
4914 * the average stabilizes with the new running time. We need to check that the
4915 * utilization stays within the range of [0..capacity_orig] and cap it if
4916 * necessary. Without utilization capping, a group could be seen as overloaded
4917 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
4918 * available capacity. We allow utilization to overshoot capacity_curr (but not
4919 * capacity_orig) as it useful for predicting the capacity required after task
4920 * migrations (scheduler-driven DVFS).
4922 static int cpu_util(int cpu)
4924 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
4925 unsigned long capacity = capacity_orig_of(cpu);
4927 return (util >= capacity) ? capacity : util;
4931 * select_task_rq_fair: Select target runqueue for the waking task in domains
4932 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4933 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4935 * Balances load by selecting the idlest cpu in the idlest group, or under
4936 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4938 * Returns the target cpu number.
4940 * preempt must be disabled.
4943 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4945 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4946 int cpu = smp_processor_id();
4947 int new_cpu = prev_cpu;
4948 int want_affine = 0;
4949 int sync = wake_flags & WF_SYNC;
4951 if (sd_flag & SD_BALANCE_WAKE)
4952 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4955 for_each_domain(cpu, tmp) {
4956 if (!(tmp->flags & SD_LOAD_BALANCE))
4960 * If both cpu and prev_cpu are part of this domain,
4961 * cpu is a valid SD_WAKE_AFFINE target.
4963 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4964 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4969 if (tmp->flags & sd_flag)
4971 else if (!want_affine)
4976 sd = NULL; /* Prefer wake_affine over balance flags */
4977 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4982 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
4983 new_cpu = select_idle_sibling(p, new_cpu);
4986 struct sched_group *group;
4989 if (!(sd->flags & sd_flag)) {
4994 group = find_idlest_group(sd, p, cpu, sd_flag);
5000 new_cpu = find_idlest_cpu(group, p, cpu);
5001 if (new_cpu == -1 || new_cpu == cpu) {
5002 /* Now try balancing at a lower domain level of cpu */
5007 /* Now try balancing at a lower domain level of new_cpu */
5009 weight = sd->span_weight;
5011 for_each_domain(cpu, tmp) {
5012 if (weight <= tmp->span_weight)
5014 if (tmp->flags & sd_flag)
5017 /* while loop will break here if sd == NULL */
5025 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5026 * cfs_rq_of(p) references at time of call are still valid and identify the
5027 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5028 * other assumptions, including the state of rq->lock, should be made.
5030 static void migrate_task_rq_fair(struct task_struct *p)
5033 * We are supposed to update the task to "current" time, then its up to date
5034 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5035 * what current time is, so simply throw away the out-of-date time. This
5036 * will result in the wakee task is less decayed, but giving the wakee more
5037 * load sounds not bad.
5039 remove_entity_load_avg(&p->se);
5041 /* Tell new CPU we are migrated */
5042 p->se.avg.last_update_time = 0;
5044 /* We have migrated, no longer consider this task hot */
5045 p->se.exec_start = 0;
5048 static void task_dead_fair(struct task_struct *p)
5050 remove_entity_load_avg(&p->se);
5052 #endif /* CONFIG_SMP */
5054 static unsigned long
5055 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5057 unsigned long gran = sysctl_sched_wakeup_granularity;
5060 * Since its curr running now, convert the gran from real-time
5061 * to virtual-time in his units.
5063 * By using 'se' instead of 'curr' we penalize light tasks, so
5064 * they get preempted easier. That is, if 'se' < 'curr' then
5065 * the resulting gran will be larger, therefore penalizing the
5066 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5067 * be smaller, again penalizing the lighter task.
5069 * This is especially important for buddies when the leftmost
5070 * task is higher priority than the buddy.
5072 return calc_delta_fair(gran, se);
5076 * Should 'se' preempt 'curr'.
5090 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5092 s64 gran, vdiff = curr->vruntime - se->vruntime;
5097 gran = wakeup_gran(curr, se);
5104 static void set_last_buddy(struct sched_entity *se)
5106 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5109 for_each_sched_entity(se)
5110 cfs_rq_of(se)->last = se;
5113 static void set_next_buddy(struct sched_entity *se)
5115 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5118 for_each_sched_entity(se)
5119 cfs_rq_of(se)->next = se;
5122 static void set_skip_buddy(struct sched_entity *se)
5124 for_each_sched_entity(se)
5125 cfs_rq_of(se)->skip = se;
5129 * Preempt the current task with a newly woken task if needed:
5131 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5133 struct task_struct *curr = rq->curr;
5134 struct sched_entity *se = &curr->se, *pse = &p->se;
5135 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5136 int scale = cfs_rq->nr_running >= sched_nr_latency;
5137 int next_buddy_marked = 0;
5139 if (unlikely(se == pse))
5143 * This is possible from callers such as attach_tasks(), in which we
5144 * unconditionally check_prempt_curr() after an enqueue (which may have
5145 * lead to a throttle). This both saves work and prevents false
5146 * next-buddy nomination below.
5148 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5151 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5152 set_next_buddy(pse);
5153 next_buddy_marked = 1;
5157 * We can come here with TIF_NEED_RESCHED already set from new task
5160 * Note: this also catches the edge-case of curr being in a throttled
5161 * group (e.g. via set_curr_task), since update_curr() (in the
5162 * enqueue of curr) will have resulted in resched being set. This
5163 * prevents us from potentially nominating it as a false LAST_BUDDY
5166 if (test_tsk_need_resched(curr))
5169 /* Idle tasks are by definition preempted by non-idle tasks. */
5170 if (unlikely(curr->policy == SCHED_IDLE) &&
5171 likely(p->policy != SCHED_IDLE))
5175 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5176 * is driven by the tick):
5178 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5181 find_matching_se(&se, &pse);
5182 update_curr(cfs_rq_of(se));
5184 if (wakeup_preempt_entity(se, pse) == 1) {
5186 * Bias pick_next to pick the sched entity that is
5187 * triggering this preemption.
5189 if (!next_buddy_marked)
5190 set_next_buddy(pse);
5199 * Only set the backward buddy when the current task is still
5200 * on the rq. This can happen when a wakeup gets interleaved
5201 * with schedule on the ->pre_schedule() or idle_balance()
5202 * point, either of which can * drop the rq lock.
5204 * Also, during early boot the idle thread is in the fair class,
5205 * for obvious reasons its a bad idea to schedule back to it.
5207 if (unlikely(!se->on_rq || curr == rq->idle))
5210 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5214 static struct task_struct *
5215 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5217 struct cfs_rq *cfs_rq = &rq->cfs;
5218 struct sched_entity *se;
5219 struct task_struct *p;
5223 #ifdef CONFIG_FAIR_GROUP_SCHED
5224 if (!cfs_rq->nr_running)
5227 if (prev->sched_class != &fair_sched_class)
5231 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5232 * likely that a next task is from the same cgroup as the current.
5234 * Therefore attempt to avoid putting and setting the entire cgroup
5235 * hierarchy, only change the part that actually changes.
5239 struct sched_entity *curr = cfs_rq->curr;
5242 * Since we got here without doing put_prev_entity() we also
5243 * have to consider cfs_rq->curr. If it is still a runnable
5244 * entity, update_curr() will update its vruntime, otherwise
5245 * forget we've ever seen it.
5249 update_curr(cfs_rq);
5254 * This call to check_cfs_rq_runtime() will do the
5255 * throttle and dequeue its entity in the parent(s).
5256 * Therefore the 'simple' nr_running test will indeed
5259 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5263 se = pick_next_entity(cfs_rq, curr);
5264 cfs_rq = group_cfs_rq(se);
5270 * Since we haven't yet done put_prev_entity and if the selected task
5271 * is a different task than we started out with, try and touch the
5272 * least amount of cfs_rqs.
5275 struct sched_entity *pse = &prev->se;
5277 while (!(cfs_rq = is_same_group(se, pse))) {
5278 int se_depth = se->depth;
5279 int pse_depth = pse->depth;
5281 if (se_depth <= pse_depth) {
5282 put_prev_entity(cfs_rq_of(pse), pse);
5283 pse = parent_entity(pse);
5285 if (se_depth >= pse_depth) {
5286 set_next_entity(cfs_rq_of(se), se);
5287 se = parent_entity(se);
5291 put_prev_entity(cfs_rq, pse);
5292 set_next_entity(cfs_rq, se);
5295 if (hrtick_enabled(rq))
5296 hrtick_start_fair(rq, p);
5303 if (!cfs_rq->nr_running)
5306 put_prev_task(rq, prev);
5309 se = pick_next_entity(cfs_rq, NULL);
5310 set_next_entity(cfs_rq, se);
5311 cfs_rq = group_cfs_rq(se);
5316 if (hrtick_enabled(rq))
5317 hrtick_start_fair(rq, p);
5323 * This is OK, because current is on_cpu, which avoids it being picked
5324 * for load-balance and preemption/IRQs are still disabled avoiding
5325 * further scheduler activity on it and we're being very careful to
5326 * re-start the picking loop.
5328 lockdep_unpin_lock(&rq->lock);
5329 new_tasks = idle_balance(rq);
5330 lockdep_pin_lock(&rq->lock);
5332 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5333 * possible for any higher priority task to appear. In that case we
5334 * must re-start the pick_next_entity() loop.
5346 * Account for a descheduled task:
5348 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5350 struct sched_entity *se = &prev->se;
5351 struct cfs_rq *cfs_rq;
5353 for_each_sched_entity(se) {
5354 cfs_rq = cfs_rq_of(se);
5355 put_prev_entity(cfs_rq, se);
5360 * sched_yield() is very simple
5362 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5364 static void yield_task_fair(struct rq *rq)
5366 struct task_struct *curr = rq->curr;
5367 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5368 struct sched_entity *se = &curr->se;
5371 * Are we the only task in the tree?
5373 if (unlikely(rq->nr_running == 1))
5376 clear_buddies(cfs_rq, se);
5378 if (curr->policy != SCHED_BATCH) {
5379 update_rq_clock(rq);
5381 * Update run-time statistics of the 'current'.
5383 update_curr(cfs_rq);
5385 * Tell update_rq_clock() that we've just updated,
5386 * so we don't do microscopic update in schedule()
5387 * and double the fastpath cost.
5389 rq_clock_skip_update(rq, true);
5395 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5397 struct sched_entity *se = &p->se;
5399 /* throttled hierarchies are not runnable */
5400 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5403 /* Tell the scheduler that we'd really like pse to run next. */
5406 yield_task_fair(rq);
5412 /**************************************************
5413 * Fair scheduling class load-balancing methods.
5417 * The purpose of load-balancing is to achieve the same basic fairness the
5418 * per-cpu scheduler provides, namely provide a proportional amount of compute
5419 * time to each task. This is expressed in the following equation:
5421 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5423 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5424 * W_i,0 is defined as:
5426 * W_i,0 = \Sum_j w_i,j (2)
5428 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5429 * is derived from the nice value as per prio_to_weight[].
5431 * The weight average is an exponential decay average of the instantaneous
5434 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5436 * C_i is the compute capacity of cpu i, typically it is the
5437 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5438 * can also include other factors [XXX].
5440 * To achieve this balance we define a measure of imbalance which follows
5441 * directly from (1):
5443 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5445 * We them move tasks around to minimize the imbalance. In the continuous
5446 * function space it is obvious this converges, in the discrete case we get
5447 * a few fun cases generally called infeasible weight scenarios.
5450 * - infeasible weights;
5451 * - local vs global optima in the discrete case. ]
5456 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5457 * for all i,j solution, we create a tree of cpus that follows the hardware
5458 * topology where each level pairs two lower groups (or better). This results
5459 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5460 * tree to only the first of the previous level and we decrease the frequency
5461 * of load-balance at each level inv. proportional to the number of cpus in
5467 * \Sum { --- * --- * 2^i } = O(n) (5)
5469 * `- size of each group
5470 * | | `- number of cpus doing load-balance
5472 * `- sum over all levels
5474 * Coupled with a limit on how many tasks we can migrate every balance pass,
5475 * this makes (5) the runtime complexity of the balancer.
5477 * An important property here is that each CPU is still (indirectly) connected
5478 * to every other cpu in at most O(log n) steps:
5480 * The adjacency matrix of the resulting graph is given by:
5483 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5486 * And you'll find that:
5488 * A^(log_2 n)_i,j != 0 for all i,j (7)
5490 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5491 * The task movement gives a factor of O(m), giving a convergence complexity
5494 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5499 * In order to avoid CPUs going idle while there's still work to do, new idle
5500 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5501 * tree itself instead of relying on other CPUs to bring it work.
5503 * This adds some complexity to both (5) and (8) but it reduces the total idle
5511 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5514 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5519 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5521 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5523 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5526 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5527 * rewrite all of this once again.]
5530 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5532 enum fbq_type { regular, remote, all };
5534 #define LBF_ALL_PINNED 0x01
5535 #define LBF_NEED_BREAK 0x02
5536 #define LBF_DST_PINNED 0x04
5537 #define LBF_SOME_PINNED 0x08
5540 struct sched_domain *sd;
5548 struct cpumask *dst_grpmask;
5550 enum cpu_idle_type idle;
5552 /* The set of CPUs under consideration for load-balancing */
5553 struct cpumask *cpus;
5558 unsigned int loop_break;
5559 unsigned int loop_max;
5561 enum fbq_type fbq_type;
5562 struct list_head tasks;
5566 * Is this task likely cache-hot:
5568 static int task_hot(struct task_struct *p, struct lb_env *env)
5572 lockdep_assert_held(&env->src_rq->lock);
5574 if (p->sched_class != &fair_sched_class)
5577 if (unlikely(p->policy == SCHED_IDLE))
5581 * Buddy candidates are cache hot:
5583 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5584 (&p->se == cfs_rq_of(&p->se)->next ||
5585 &p->se == cfs_rq_of(&p->se)->last))
5588 if (sysctl_sched_migration_cost == -1)
5590 if (sysctl_sched_migration_cost == 0)
5593 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5595 return delta < (s64)sysctl_sched_migration_cost;
5598 #ifdef CONFIG_NUMA_BALANCING
5600 * Returns 1, if task migration degrades locality
5601 * Returns 0, if task migration improves locality i.e migration preferred.
5602 * Returns -1, if task migration is not affected by locality.
5604 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5606 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5607 unsigned long src_faults, dst_faults;
5608 int src_nid, dst_nid;
5610 if (!static_branch_likely(&sched_numa_balancing))
5613 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5616 src_nid = cpu_to_node(env->src_cpu);
5617 dst_nid = cpu_to_node(env->dst_cpu);
5619 if (src_nid == dst_nid)
5622 /* Migrating away from the preferred node is always bad. */
5623 if (src_nid == p->numa_preferred_nid) {
5624 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5630 /* Encourage migration to the preferred node. */
5631 if (dst_nid == p->numa_preferred_nid)
5635 src_faults = group_faults(p, src_nid);
5636 dst_faults = group_faults(p, dst_nid);
5638 src_faults = task_faults(p, src_nid);
5639 dst_faults = task_faults(p, dst_nid);
5642 return dst_faults < src_faults;
5646 static inline int migrate_degrades_locality(struct task_struct *p,
5654 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5657 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5661 lockdep_assert_held(&env->src_rq->lock);
5664 * We do not migrate tasks that are:
5665 * 1) throttled_lb_pair, or
5666 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5667 * 3) running (obviously), or
5668 * 4) are cache-hot on their current CPU.
5670 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5673 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5676 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5678 env->flags |= LBF_SOME_PINNED;
5681 * Remember if this task can be migrated to any other cpu in
5682 * our sched_group. We may want to revisit it if we couldn't
5683 * meet load balance goals by pulling other tasks on src_cpu.
5685 * Also avoid computing new_dst_cpu if we have already computed
5686 * one in current iteration.
5688 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5691 /* Prevent to re-select dst_cpu via env's cpus */
5692 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5693 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5694 env->flags |= LBF_DST_PINNED;
5695 env->new_dst_cpu = cpu;
5703 /* Record that we found atleast one task that could run on dst_cpu */
5704 env->flags &= ~LBF_ALL_PINNED;
5706 if (task_running(env->src_rq, p)) {
5707 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5712 * Aggressive migration if:
5713 * 1) destination numa is preferred
5714 * 2) task is cache cold, or
5715 * 3) too many balance attempts have failed.
5717 tsk_cache_hot = migrate_degrades_locality(p, env);
5718 if (tsk_cache_hot == -1)
5719 tsk_cache_hot = task_hot(p, env);
5721 if (tsk_cache_hot <= 0 ||
5722 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5723 if (tsk_cache_hot == 1) {
5724 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5725 schedstat_inc(p, se.statistics.nr_forced_migrations);
5730 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5735 * detach_task() -- detach the task for the migration specified in env
5737 static void detach_task(struct task_struct *p, struct lb_env *env)
5739 lockdep_assert_held(&env->src_rq->lock);
5741 deactivate_task(env->src_rq, p, 0);
5742 p->on_rq = TASK_ON_RQ_MIGRATING;
5743 set_task_cpu(p, env->dst_cpu);
5747 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5748 * part of active balancing operations within "domain".
5750 * Returns a task if successful and NULL otherwise.
5752 static struct task_struct *detach_one_task(struct lb_env *env)
5754 struct task_struct *p, *n;
5756 lockdep_assert_held(&env->src_rq->lock);
5758 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5759 if (!can_migrate_task(p, env))
5762 detach_task(p, env);
5765 * Right now, this is only the second place where
5766 * lb_gained[env->idle] is updated (other is detach_tasks)
5767 * so we can safely collect stats here rather than
5768 * inside detach_tasks().
5770 schedstat_inc(env->sd, lb_gained[env->idle]);
5776 static const unsigned int sched_nr_migrate_break = 32;
5779 * detach_tasks() -- tries to detach up to imbalance weighted load from
5780 * busiest_rq, as part of a balancing operation within domain "sd".
5782 * Returns number of detached tasks if successful and 0 otherwise.
5784 static int detach_tasks(struct lb_env *env)
5786 struct list_head *tasks = &env->src_rq->cfs_tasks;
5787 struct task_struct *p;
5791 lockdep_assert_held(&env->src_rq->lock);
5793 if (env->imbalance <= 0)
5796 while (!list_empty(tasks)) {
5798 * We don't want to steal all, otherwise we may be treated likewise,
5799 * which could at worst lead to a livelock crash.
5801 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
5804 p = list_first_entry(tasks, struct task_struct, se.group_node);
5807 /* We've more or less seen every task there is, call it quits */
5808 if (env->loop > env->loop_max)
5811 /* take a breather every nr_migrate tasks */
5812 if (env->loop > env->loop_break) {
5813 env->loop_break += sched_nr_migrate_break;
5814 env->flags |= LBF_NEED_BREAK;
5818 if (!can_migrate_task(p, env))
5821 load = task_h_load(p);
5823 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5826 if ((load / 2) > env->imbalance)
5829 detach_task(p, env);
5830 list_add(&p->se.group_node, &env->tasks);
5833 env->imbalance -= load;
5835 #ifdef CONFIG_PREEMPT
5837 * NEWIDLE balancing is a source of latency, so preemptible
5838 * kernels will stop after the first task is detached to minimize
5839 * the critical section.
5841 if (env->idle == CPU_NEWLY_IDLE)
5846 * We only want to steal up to the prescribed amount of
5849 if (env->imbalance <= 0)
5854 list_move_tail(&p->se.group_node, tasks);
5858 * Right now, this is one of only two places we collect this stat
5859 * so we can safely collect detach_one_task() stats here rather
5860 * than inside detach_one_task().
5862 schedstat_add(env->sd, lb_gained[env->idle], detached);
5868 * attach_task() -- attach the task detached by detach_task() to its new rq.
5870 static void attach_task(struct rq *rq, struct task_struct *p)
5872 lockdep_assert_held(&rq->lock);
5874 BUG_ON(task_rq(p) != rq);
5875 p->on_rq = TASK_ON_RQ_QUEUED;
5876 activate_task(rq, p, 0);
5877 check_preempt_curr(rq, p, 0);
5881 * attach_one_task() -- attaches the task returned from detach_one_task() to
5884 static void attach_one_task(struct rq *rq, struct task_struct *p)
5886 raw_spin_lock(&rq->lock);
5888 raw_spin_unlock(&rq->lock);
5892 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5895 static void attach_tasks(struct lb_env *env)
5897 struct list_head *tasks = &env->tasks;
5898 struct task_struct *p;
5900 raw_spin_lock(&env->dst_rq->lock);
5902 while (!list_empty(tasks)) {
5903 p = list_first_entry(tasks, struct task_struct, se.group_node);
5904 list_del_init(&p->se.group_node);
5906 attach_task(env->dst_rq, p);
5909 raw_spin_unlock(&env->dst_rq->lock);
5912 #ifdef CONFIG_FAIR_GROUP_SCHED
5913 static void update_blocked_averages(int cpu)
5915 struct rq *rq = cpu_rq(cpu);
5916 struct cfs_rq *cfs_rq;
5917 unsigned long flags;
5919 raw_spin_lock_irqsave(&rq->lock, flags);
5920 update_rq_clock(rq);
5923 * Iterates the task_group tree in a bottom up fashion, see
5924 * list_add_leaf_cfs_rq() for details.
5926 for_each_leaf_cfs_rq(rq, cfs_rq) {
5927 /* throttled entities do not contribute to load */
5928 if (throttled_hierarchy(cfs_rq))
5931 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
5932 update_tg_load_avg(cfs_rq, 0);
5934 raw_spin_unlock_irqrestore(&rq->lock, flags);
5938 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5939 * This needs to be done in a top-down fashion because the load of a child
5940 * group is a fraction of its parents load.
5942 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5944 struct rq *rq = rq_of(cfs_rq);
5945 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5946 unsigned long now = jiffies;
5949 if (cfs_rq->last_h_load_update == now)
5952 cfs_rq->h_load_next = NULL;
5953 for_each_sched_entity(se) {
5954 cfs_rq = cfs_rq_of(se);
5955 cfs_rq->h_load_next = se;
5956 if (cfs_rq->last_h_load_update == now)
5961 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5962 cfs_rq->last_h_load_update = now;
5965 while ((se = cfs_rq->h_load_next) != NULL) {
5966 load = cfs_rq->h_load;
5967 load = div64_ul(load * se->avg.load_avg,
5968 cfs_rq_load_avg(cfs_rq) + 1);
5969 cfs_rq = group_cfs_rq(se);
5970 cfs_rq->h_load = load;
5971 cfs_rq->last_h_load_update = now;
5975 static unsigned long task_h_load(struct task_struct *p)
5977 struct cfs_rq *cfs_rq = task_cfs_rq(p);
5979 update_cfs_rq_h_load(cfs_rq);
5980 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
5981 cfs_rq_load_avg(cfs_rq) + 1);
5984 static inline void update_blocked_averages(int cpu)
5986 struct rq *rq = cpu_rq(cpu);
5987 struct cfs_rq *cfs_rq = &rq->cfs;
5988 unsigned long flags;
5990 raw_spin_lock_irqsave(&rq->lock, flags);
5991 update_rq_clock(rq);
5992 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
5993 raw_spin_unlock_irqrestore(&rq->lock, flags);
5996 static unsigned long task_h_load(struct task_struct *p)
5998 return p->se.avg.load_avg;
6002 /********** Helpers for find_busiest_group ************************/
6011 * sg_lb_stats - stats of a sched_group required for load_balancing
6013 struct sg_lb_stats {
6014 unsigned long avg_load; /*Avg load across the CPUs of the group */
6015 unsigned long group_load; /* Total load over the CPUs of the group */
6016 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6017 unsigned long load_per_task;
6018 unsigned long group_capacity;
6019 unsigned long group_util; /* Total utilization of the group */
6020 unsigned int sum_nr_running; /* Nr tasks running in the group */
6021 unsigned int idle_cpus;
6022 unsigned int group_weight;
6023 enum group_type group_type;
6024 int group_no_capacity;
6025 #ifdef CONFIG_NUMA_BALANCING
6026 unsigned int nr_numa_running;
6027 unsigned int nr_preferred_running;
6032 * sd_lb_stats - Structure to store the statistics of a sched_domain
6033 * during load balancing.
6035 struct sd_lb_stats {
6036 struct sched_group *busiest; /* Busiest group in this sd */
6037 struct sched_group *local; /* Local group in this sd */
6038 unsigned long total_load; /* Total load of all groups in sd */
6039 unsigned long total_capacity; /* Total capacity of all groups in sd */
6040 unsigned long avg_load; /* Average load across all groups in sd */
6042 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6043 struct sg_lb_stats local_stat; /* Statistics of the local group */
6046 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6049 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6050 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6051 * We must however clear busiest_stat::avg_load because
6052 * update_sd_pick_busiest() reads this before assignment.
6054 *sds = (struct sd_lb_stats){
6058 .total_capacity = 0UL,
6061 .sum_nr_running = 0,
6062 .group_type = group_other,
6068 * get_sd_load_idx - Obtain the load index for a given sched domain.
6069 * @sd: The sched_domain whose load_idx is to be obtained.
6070 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6072 * Return: The load index.
6074 static inline int get_sd_load_idx(struct sched_domain *sd,
6075 enum cpu_idle_type idle)
6081 load_idx = sd->busy_idx;
6084 case CPU_NEWLY_IDLE:
6085 load_idx = sd->newidle_idx;
6088 load_idx = sd->idle_idx;
6095 static unsigned long scale_rt_capacity(int cpu)
6097 struct rq *rq = cpu_rq(cpu);
6098 u64 total, used, age_stamp, avg;
6102 * Since we're reading these variables without serialization make sure
6103 * we read them once before doing sanity checks on them.
6105 age_stamp = READ_ONCE(rq->age_stamp);
6106 avg = READ_ONCE(rq->rt_avg);
6107 delta = __rq_clock_broken(rq) - age_stamp;
6109 if (unlikely(delta < 0))
6112 total = sched_avg_period() + delta;
6114 used = div_u64(avg, total);
6116 if (likely(used < SCHED_CAPACITY_SCALE))
6117 return SCHED_CAPACITY_SCALE - used;
6122 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6124 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6125 struct sched_group *sdg = sd->groups;
6127 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6129 capacity *= scale_rt_capacity(cpu);
6130 capacity >>= SCHED_CAPACITY_SHIFT;
6135 cpu_rq(cpu)->cpu_capacity = capacity;
6136 sdg->sgc->capacity = capacity;
6139 void update_group_capacity(struct sched_domain *sd, int cpu)
6141 struct sched_domain *child = sd->child;
6142 struct sched_group *group, *sdg = sd->groups;
6143 unsigned long capacity;
6144 unsigned long interval;
6146 interval = msecs_to_jiffies(sd->balance_interval);
6147 interval = clamp(interval, 1UL, max_load_balance_interval);
6148 sdg->sgc->next_update = jiffies + interval;
6151 update_cpu_capacity(sd, cpu);
6157 if (child->flags & SD_OVERLAP) {
6159 * SD_OVERLAP domains cannot assume that child groups
6160 * span the current group.
6163 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6164 struct sched_group_capacity *sgc;
6165 struct rq *rq = cpu_rq(cpu);
6168 * build_sched_domains() -> init_sched_groups_capacity()
6169 * gets here before we've attached the domains to the
6172 * Use capacity_of(), which is set irrespective of domains
6173 * in update_cpu_capacity().
6175 * This avoids capacity from being 0 and
6176 * causing divide-by-zero issues on boot.
6178 if (unlikely(!rq->sd)) {
6179 capacity += capacity_of(cpu);
6183 sgc = rq->sd->groups->sgc;
6184 capacity += sgc->capacity;
6188 * !SD_OVERLAP domains can assume that child groups
6189 * span the current group.
6192 group = child->groups;
6194 capacity += group->sgc->capacity;
6195 group = group->next;
6196 } while (group != child->groups);
6199 sdg->sgc->capacity = capacity;
6203 * Check whether the capacity of the rq has been noticeably reduced by side
6204 * activity. The imbalance_pct is used for the threshold.
6205 * Return true is the capacity is reduced
6208 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6210 return ((rq->cpu_capacity * sd->imbalance_pct) <
6211 (rq->cpu_capacity_orig * 100));
6215 * Group imbalance indicates (and tries to solve) the problem where balancing
6216 * groups is inadequate due to tsk_cpus_allowed() constraints.
6218 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6219 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6222 * { 0 1 2 3 } { 4 5 6 7 }
6225 * If we were to balance group-wise we'd place two tasks in the first group and
6226 * two tasks in the second group. Clearly this is undesired as it will overload
6227 * cpu 3 and leave one of the cpus in the second group unused.
6229 * The current solution to this issue is detecting the skew in the first group
6230 * by noticing the lower domain failed to reach balance and had difficulty
6231 * moving tasks due to affinity constraints.
6233 * When this is so detected; this group becomes a candidate for busiest; see
6234 * update_sd_pick_busiest(). And calculate_imbalance() and
6235 * find_busiest_group() avoid some of the usual balance conditions to allow it
6236 * to create an effective group imbalance.
6238 * This is a somewhat tricky proposition since the next run might not find the
6239 * group imbalance and decide the groups need to be balanced again. A most
6240 * subtle and fragile situation.
6243 static inline int sg_imbalanced(struct sched_group *group)
6245 return group->sgc->imbalance;
6249 * group_has_capacity returns true if the group has spare capacity that could
6250 * be used by some tasks.
6251 * We consider that a group has spare capacity if the * number of task is
6252 * smaller than the number of CPUs or if the utilization is lower than the
6253 * available capacity for CFS tasks.
6254 * For the latter, we use a threshold to stabilize the state, to take into
6255 * account the variance of the tasks' load and to return true if the available
6256 * capacity in meaningful for the load balancer.
6257 * As an example, an available capacity of 1% can appear but it doesn't make
6258 * any benefit for the load balance.
6261 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6263 if (sgs->sum_nr_running < sgs->group_weight)
6266 if ((sgs->group_capacity * 100) >
6267 (sgs->group_util * env->sd->imbalance_pct))
6274 * group_is_overloaded returns true if the group has more tasks than it can
6276 * group_is_overloaded is not equals to !group_has_capacity because a group
6277 * with the exact right number of tasks, has no more spare capacity but is not
6278 * overloaded so both group_has_capacity and group_is_overloaded return
6282 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6284 if (sgs->sum_nr_running <= sgs->group_weight)
6287 if ((sgs->group_capacity * 100) <
6288 (sgs->group_util * env->sd->imbalance_pct))
6295 group_type group_classify(struct sched_group *group,
6296 struct sg_lb_stats *sgs)
6298 if (sgs->group_no_capacity)
6299 return group_overloaded;
6301 if (sg_imbalanced(group))
6302 return group_imbalanced;
6308 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6309 * @env: The load balancing environment.
6310 * @group: sched_group whose statistics are to be updated.
6311 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6312 * @local_group: Does group contain this_cpu.
6313 * @sgs: variable to hold the statistics for this group.
6314 * @overload: Indicate more than one runnable task for any CPU.
6316 static inline void update_sg_lb_stats(struct lb_env *env,
6317 struct sched_group *group, int load_idx,
6318 int local_group, struct sg_lb_stats *sgs,
6324 memset(sgs, 0, sizeof(*sgs));
6326 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6327 struct rq *rq = cpu_rq(i);
6329 /* Bias balancing toward cpus of our domain */
6331 load = target_load(i, load_idx);
6333 load = source_load(i, load_idx);
6335 sgs->group_load += load;
6336 sgs->group_util += cpu_util(i);
6337 sgs->sum_nr_running += rq->cfs.h_nr_running;
6339 if (rq->nr_running > 1)
6342 #ifdef CONFIG_NUMA_BALANCING
6343 sgs->nr_numa_running += rq->nr_numa_running;
6344 sgs->nr_preferred_running += rq->nr_preferred_running;
6346 sgs->sum_weighted_load += weighted_cpuload(i);
6351 /* Adjust by relative CPU capacity of the group */
6352 sgs->group_capacity = group->sgc->capacity;
6353 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6355 if (sgs->sum_nr_running)
6356 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6358 sgs->group_weight = group->group_weight;
6360 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6361 sgs->group_type = group_classify(group, sgs);
6365 * update_sd_pick_busiest - return 1 on busiest group
6366 * @env: The load balancing environment.
6367 * @sds: sched_domain statistics
6368 * @sg: sched_group candidate to be checked for being the busiest
6369 * @sgs: sched_group statistics
6371 * Determine if @sg is a busier group than the previously selected
6374 * Return: %true if @sg is a busier group than the previously selected
6375 * busiest group. %false otherwise.
6377 static bool update_sd_pick_busiest(struct lb_env *env,
6378 struct sd_lb_stats *sds,
6379 struct sched_group *sg,
6380 struct sg_lb_stats *sgs)
6382 struct sg_lb_stats *busiest = &sds->busiest_stat;
6384 if (sgs->group_type > busiest->group_type)
6387 if (sgs->group_type < busiest->group_type)
6390 if (sgs->avg_load <= busiest->avg_load)
6393 /* This is the busiest node in its class. */
6394 if (!(env->sd->flags & SD_ASYM_PACKING))
6398 * ASYM_PACKING needs to move all the work to the lowest
6399 * numbered CPUs in the group, therefore mark all groups
6400 * higher than ourself as busy.
6402 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6406 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6413 #ifdef CONFIG_NUMA_BALANCING
6414 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6416 if (sgs->sum_nr_running > sgs->nr_numa_running)
6418 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6423 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6425 if (rq->nr_running > rq->nr_numa_running)
6427 if (rq->nr_running > rq->nr_preferred_running)
6432 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6437 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6441 #endif /* CONFIG_NUMA_BALANCING */
6444 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6445 * @env: The load balancing environment.
6446 * @sds: variable to hold the statistics for this sched_domain.
6448 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6450 struct sched_domain *child = env->sd->child;
6451 struct sched_group *sg = env->sd->groups;
6452 struct sg_lb_stats tmp_sgs;
6453 int load_idx, prefer_sibling = 0;
6454 bool overload = false;
6456 if (child && child->flags & SD_PREFER_SIBLING)
6459 load_idx = get_sd_load_idx(env->sd, env->idle);
6462 struct sg_lb_stats *sgs = &tmp_sgs;
6465 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6468 sgs = &sds->local_stat;
6470 if (env->idle != CPU_NEWLY_IDLE ||
6471 time_after_eq(jiffies, sg->sgc->next_update))
6472 update_group_capacity(env->sd, env->dst_cpu);
6475 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6482 * In case the child domain prefers tasks go to siblings
6483 * first, lower the sg capacity so that we'll try
6484 * and move all the excess tasks away. We lower the capacity
6485 * of a group only if the local group has the capacity to fit
6486 * these excess tasks. The extra check prevents the case where
6487 * you always pull from the heaviest group when it is already
6488 * under-utilized (possible with a large weight task outweighs
6489 * the tasks on the system).
6491 if (prefer_sibling && sds->local &&
6492 group_has_capacity(env, &sds->local_stat) &&
6493 (sgs->sum_nr_running > 1)) {
6494 sgs->group_no_capacity = 1;
6495 sgs->group_type = group_classify(sg, sgs);
6498 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6500 sds->busiest_stat = *sgs;
6504 /* Now, start updating sd_lb_stats */
6505 sds->total_load += sgs->group_load;
6506 sds->total_capacity += sgs->group_capacity;
6509 } while (sg != env->sd->groups);
6511 if (env->sd->flags & SD_NUMA)
6512 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6514 if (!env->sd->parent) {
6515 /* update overload indicator if we are at root domain */
6516 if (env->dst_rq->rd->overload != overload)
6517 env->dst_rq->rd->overload = overload;
6523 * check_asym_packing - Check to see if the group is packed into the
6526 * This is primarily intended to used at the sibling level. Some
6527 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6528 * case of POWER7, it can move to lower SMT modes only when higher
6529 * threads are idle. When in lower SMT modes, the threads will
6530 * perform better since they share less core resources. Hence when we
6531 * have idle threads, we want them to be the higher ones.
6533 * This packing function is run on idle threads. It checks to see if
6534 * the busiest CPU in this domain (core in the P7 case) has a higher
6535 * CPU number than the packing function is being run on. Here we are
6536 * assuming lower CPU number will be equivalent to lower a SMT thread
6539 * Return: 1 when packing is required and a task should be moved to
6540 * this CPU. The amount of the imbalance is returned in *imbalance.
6542 * @env: The load balancing environment.
6543 * @sds: Statistics of the sched_domain which is to be packed
6545 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6549 if (!(env->sd->flags & SD_ASYM_PACKING))
6555 busiest_cpu = group_first_cpu(sds->busiest);
6556 if (env->dst_cpu > busiest_cpu)
6559 env->imbalance = DIV_ROUND_CLOSEST(
6560 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6561 SCHED_CAPACITY_SCALE);
6567 * fix_small_imbalance - Calculate the minor imbalance that exists
6568 * amongst the groups of a sched_domain, during
6570 * @env: The load balancing environment.
6571 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6574 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6576 unsigned long tmp, capa_now = 0, capa_move = 0;
6577 unsigned int imbn = 2;
6578 unsigned long scaled_busy_load_per_task;
6579 struct sg_lb_stats *local, *busiest;
6581 local = &sds->local_stat;
6582 busiest = &sds->busiest_stat;
6584 if (!local->sum_nr_running)
6585 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6586 else if (busiest->load_per_task > local->load_per_task)
6589 scaled_busy_load_per_task =
6590 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6591 busiest->group_capacity;
6593 if (busiest->avg_load + scaled_busy_load_per_task >=
6594 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6595 env->imbalance = busiest->load_per_task;
6600 * OK, we don't have enough imbalance to justify moving tasks,
6601 * however we may be able to increase total CPU capacity used by
6605 capa_now += busiest->group_capacity *
6606 min(busiest->load_per_task, busiest->avg_load);
6607 capa_now += local->group_capacity *
6608 min(local->load_per_task, local->avg_load);
6609 capa_now /= SCHED_CAPACITY_SCALE;
6611 /* Amount of load we'd subtract */
6612 if (busiest->avg_load > scaled_busy_load_per_task) {
6613 capa_move += busiest->group_capacity *
6614 min(busiest->load_per_task,
6615 busiest->avg_load - scaled_busy_load_per_task);
6618 /* Amount of load we'd add */
6619 if (busiest->avg_load * busiest->group_capacity <
6620 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6621 tmp = (busiest->avg_load * busiest->group_capacity) /
6622 local->group_capacity;
6624 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6625 local->group_capacity;
6627 capa_move += local->group_capacity *
6628 min(local->load_per_task, local->avg_load + tmp);
6629 capa_move /= SCHED_CAPACITY_SCALE;
6631 /* Move if we gain throughput */
6632 if (capa_move > capa_now)
6633 env->imbalance = busiest->load_per_task;
6637 * calculate_imbalance - Calculate the amount of imbalance present within the
6638 * groups of a given sched_domain during load balance.
6639 * @env: load balance environment
6640 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6642 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6644 unsigned long max_pull, load_above_capacity = ~0UL;
6645 struct sg_lb_stats *local, *busiest;
6647 local = &sds->local_stat;
6648 busiest = &sds->busiest_stat;
6650 if (busiest->group_type == group_imbalanced) {
6652 * In the group_imb case we cannot rely on group-wide averages
6653 * to ensure cpu-load equilibrium, look at wider averages. XXX
6655 busiest->load_per_task =
6656 min(busiest->load_per_task, sds->avg_load);
6660 * In the presence of smp nice balancing, certain scenarios can have
6661 * max load less than avg load(as we skip the groups at or below
6662 * its cpu_capacity, while calculating max_load..)
6664 if (busiest->avg_load <= sds->avg_load ||
6665 local->avg_load >= sds->avg_load) {
6667 return fix_small_imbalance(env, sds);
6671 * If there aren't any idle cpus, avoid creating some.
6673 if (busiest->group_type == group_overloaded &&
6674 local->group_type == group_overloaded) {
6675 load_above_capacity = busiest->sum_nr_running *
6677 if (load_above_capacity > busiest->group_capacity)
6678 load_above_capacity -= busiest->group_capacity;
6680 load_above_capacity = ~0UL;
6684 * We're trying to get all the cpus to the average_load, so we don't
6685 * want to push ourselves above the average load, nor do we wish to
6686 * reduce the max loaded cpu below the average load. At the same time,
6687 * we also don't want to reduce the group load below the group capacity
6688 * (so that we can implement power-savings policies etc). Thus we look
6689 * for the minimum possible imbalance.
6691 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6693 /* How much load to actually move to equalise the imbalance */
6694 env->imbalance = min(
6695 max_pull * busiest->group_capacity,
6696 (sds->avg_load - local->avg_load) * local->group_capacity
6697 ) / SCHED_CAPACITY_SCALE;
6700 * if *imbalance is less than the average load per runnable task
6701 * there is no guarantee that any tasks will be moved so we'll have
6702 * a think about bumping its value to force at least one task to be
6705 if (env->imbalance < busiest->load_per_task)
6706 return fix_small_imbalance(env, sds);
6709 /******* find_busiest_group() helpers end here *********************/
6712 * find_busiest_group - Returns the busiest group within the sched_domain
6713 * if there is an imbalance. If there isn't an imbalance, and
6714 * the user has opted for power-savings, it returns a group whose
6715 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6716 * such a group exists.
6718 * Also calculates the amount of weighted load which should be moved
6719 * to restore balance.
6721 * @env: The load balancing environment.
6723 * Return: - The busiest group if imbalance exists.
6724 * - If no imbalance and user has opted for power-savings balance,
6725 * return the least loaded group whose CPUs can be
6726 * put to idle by rebalancing its tasks onto our group.
6728 static struct sched_group *find_busiest_group(struct lb_env *env)
6730 struct sg_lb_stats *local, *busiest;
6731 struct sd_lb_stats sds;
6733 init_sd_lb_stats(&sds);
6736 * Compute the various statistics relavent for load balancing at
6739 update_sd_lb_stats(env, &sds);
6740 local = &sds.local_stat;
6741 busiest = &sds.busiest_stat;
6743 /* ASYM feature bypasses nice load balance check */
6744 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6745 check_asym_packing(env, &sds))
6748 /* There is no busy sibling group to pull tasks from */
6749 if (!sds.busiest || busiest->sum_nr_running == 0)
6752 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6753 / sds.total_capacity;
6756 * If the busiest group is imbalanced the below checks don't
6757 * work because they assume all things are equal, which typically
6758 * isn't true due to cpus_allowed constraints and the like.
6760 if (busiest->group_type == group_imbalanced)
6763 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6764 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6765 busiest->group_no_capacity)
6769 * If the local group is busier than the selected busiest group
6770 * don't try and pull any tasks.
6772 if (local->avg_load >= busiest->avg_load)
6776 * Don't pull any tasks if this group is already above the domain
6779 if (local->avg_load >= sds.avg_load)
6782 if (env->idle == CPU_IDLE) {
6784 * This cpu is idle. If the busiest group is not overloaded
6785 * and there is no imbalance between this and busiest group
6786 * wrt idle cpus, it is balanced. The imbalance becomes
6787 * significant if the diff is greater than 1 otherwise we
6788 * might end up to just move the imbalance on another group
6790 if ((busiest->group_type != group_overloaded) &&
6791 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6795 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6796 * imbalance_pct to be conservative.
6798 if (100 * busiest->avg_load <=
6799 env->sd->imbalance_pct * local->avg_load)
6804 /* Looks like there is an imbalance. Compute it */
6805 calculate_imbalance(env, &sds);
6814 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6816 static struct rq *find_busiest_queue(struct lb_env *env,
6817 struct sched_group *group)
6819 struct rq *busiest = NULL, *rq;
6820 unsigned long busiest_load = 0, busiest_capacity = 1;
6823 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6824 unsigned long capacity, wl;
6828 rt = fbq_classify_rq(rq);
6831 * We classify groups/runqueues into three groups:
6832 * - regular: there are !numa tasks
6833 * - remote: there are numa tasks that run on the 'wrong' node
6834 * - all: there is no distinction
6836 * In order to avoid migrating ideally placed numa tasks,
6837 * ignore those when there's better options.
6839 * If we ignore the actual busiest queue to migrate another
6840 * task, the next balance pass can still reduce the busiest
6841 * queue by moving tasks around inside the node.
6843 * If we cannot move enough load due to this classification
6844 * the next pass will adjust the group classification and
6845 * allow migration of more tasks.
6847 * Both cases only affect the total convergence complexity.
6849 if (rt > env->fbq_type)
6852 capacity = capacity_of(i);
6854 wl = weighted_cpuload(i);
6857 * When comparing with imbalance, use weighted_cpuload()
6858 * which is not scaled with the cpu capacity.
6861 if (rq->nr_running == 1 && wl > env->imbalance &&
6862 !check_cpu_capacity(rq, env->sd))
6866 * For the load comparisons with the other cpu's, consider
6867 * the weighted_cpuload() scaled with the cpu capacity, so
6868 * that the load can be moved away from the cpu that is
6869 * potentially running at a lower capacity.
6871 * Thus we're looking for max(wl_i / capacity_i), crosswise
6872 * multiplication to rid ourselves of the division works out
6873 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
6874 * our previous maximum.
6876 if (wl * busiest_capacity > busiest_load * capacity) {
6878 busiest_capacity = capacity;
6887 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6888 * so long as it is large enough.
6890 #define MAX_PINNED_INTERVAL 512
6892 /* Working cpumask for load_balance and load_balance_newidle. */
6893 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6895 static int need_active_balance(struct lb_env *env)
6897 struct sched_domain *sd = env->sd;
6899 if (env->idle == CPU_NEWLY_IDLE) {
6902 * ASYM_PACKING needs to force migrate tasks from busy but
6903 * higher numbered CPUs in order to pack all tasks in the
6904 * lowest numbered CPUs.
6906 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6911 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
6912 * It's worth migrating the task if the src_cpu's capacity is reduced
6913 * because of other sched_class or IRQs if more capacity stays
6914 * available on dst_cpu.
6916 if ((env->idle != CPU_NOT_IDLE) &&
6917 (env->src_rq->cfs.h_nr_running == 1)) {
6918 if ((check_cpu_capacity(env->src_rq, sd)) &&
6919 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
6923 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6926 static int active_load_balance_cpu_stop(void *data);
6928 static int should_we_balance(struct lb_env *env)
6930 struct sched_group *sg = env->sd->groups;
6931 struct cpumask *sg_cpus, *sg_mask;
6932 int cpu, balance_cpu = -1;
6935 * In the newly idle case, we will allow all the cpu's
6936 * to do the newly idle load balance.
6938 if (env->idle == CPU_NEWLY_IDLE)
6941 sg_cpus = sched_group_cpus(sg);
6942 sg_mask = sched_group_mask(sg);
6943 /* Try to find first idle cpu */
6944 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6945 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6952 if (balance_cpu == -1)
6953 balance_cpu = group_balance_cpu(sg);
6956 * First idle cpu or the first cpu(busiest) in this sched group
6957 * is eligible for doing load balancing at this and above domains.
6959 return balance_cpu == env->dst_cpu;
6963 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6964 * tasks if there is an imbalance.
6966 static int load_balance(int this_cpu, struct rq *this_rq,
6967 struct sched_domain *sd, enum cpu_idle_type idle,
6968 int *continue_balancing)
6970 int ld_moved, cur_ld_moved, active_balance = 0;
6971 struct sched_domain *sd_parent = sd->parent;
6972 struct sched_group *group;
6974 unsigned long flags;
6975 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6977 struct lb_env env = {
6979 .dst_cpu = this_cpu,
6981 .dst_grpmask = sched_group_cpus(sd->groups),
6983 .loop_break = sched_nr_migrate_break,
6986 .tasks = LIST_HEAD_INIT(env.tasks),
6990 * For NEWLY_IDLE load_balancing, we don't need to consider
6991 * other cpus in our group
6993 if (idle == CPU_NEWLY_IDLE)
6994 env.dst_grpmask = NULL;
6996 cpumask_copy(cpus, cpu_active_mask);
6998 schedstat_inc(sd, lb_count[idle]);
7001 if (!should_we_balance(&env)) {
7002 *continue_balancing = 0;
7006 group = find_busiest_group(&env);
7008 schedstat_inc(sd, lb_nobusyg[idle]);
7012 busiest = find_busiest_queue(&env, group);
7014 schedstat_inc(sd, lb_nobusyq[idle]);
7018 BUG_ON(busiest == env.dst_rq);
7020 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7022 env.src_cpu = busiest->cpu;
7023 env.src_rq = busiest;
7026 if (busiest->nr_running > 1) {
7028 * Attempt to move tasks. If find_busiest_group has found
7029 * an imbalance but busiest->nr_running <= 1, the group is
7030 * still unbalanced. ld_moved simply stays zero, so it is
7031 * correctly treated as an imbalance.
7033 env.flags |= LBF_ALL_PINNED;
7034 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7037 raw_spin_lock_irqsave(&busiest->lock, flags);
7040 * cur_ld_moved - load moved in current iteration
7041 * ld_moved - cumulative load moved across iterations
7043 cur_ld_moved = detach_tasks(&env);
7046 * We've detached some tasks from busiest_rq. Every
7047 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7048 * unlock busiest->lock, and we are able to be sure
7049 * that nobody can manipulate the tasks in parallel.
7050 * See task_rq_lock() family for the details.
7053 raw_spin_unlock(&busiest->lock);
7057 ld_moved += cur_ld_moved;
7060 local_irq_restore(flags);
7062 if (env.flags & LBF_NEED_BREAK) {
7063 env.flags &= ~LBF_NEED_BREAK;
7068 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7069 * us and move them to an alternate dst_cpu in our sched_group
7070 * where they can run. The upper limit on how many times we
7071 * iterate on same src_cpu is dependent on number of cpus in our
7074 * This changes load balance semantics a bit on who can move
7075 * load to a given_cpu. In addition to the given_cpu itself
7076 * (or a ilb_cpu acting on its behalf where given_cpu is
7077 * nohz-idle), we now have balance_cpu in a position to move
7078 * load to given_cpu. In rare situations, this may cause
7079 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7080 * _independently_ and at _same_ time to move some load to
7081 * given_cpu) causing exceess load to be moved to given_cpu.
7082 * This however should not happen so much in practice and
7083 * moreover subsequent load balance cycles should correct the
7084 * excess load moved.
7086 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7088 /* Prevent to re-select dst_cpu via env's cpus */
7089 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7091 env.dst_rq = cpu_rq(env.new_dst_cpu);
7092 env.dst_cpu = env.new_dst_cpu;
7093 env.flags &= ~LBF_DST_PINNED;
7095 env.loop_break = sched_nr_migrate_break;
7098 * Go back to "more_balance" rather than "redo" since we
7099 * need to continue with same src_cpu.
7105 * We failed to reach balance because of affinity.
7108 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7110 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7111 *group_imbalance = 1;
7114 /* All tasks on this runqueue were pinned by CPU affinity */
7115 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7116 cpumask_clear_cpu(cpu_of(busiest), cpus);
7117 if (!cpumask_empty(cpus)) {
7119 env.loop_break = sched_nr_migrate_break;
7122 goto out_all_pinned;
7127 schedstat_inc(sd, lb_failed[idle]);
7129 * Increment the failure counter only on periodic balance.
7130 * We do not want newidle balance, which can be very
7131 * frequent, pollute the failure counter causing
7132 * excessive cache_hot migrations and active balances.
7134 if (idle != CPU_NEWLY_IDLE)
7135 sd->nr_balance_failed++;
7137 if (need_active_balance(&env)) {
7138 raw_spin_lock_irqsave(&busiest->lock, flags);
7140 /* don't kick the active_load_balance_cpu_stop,
7141 * if the curr task on busiest cpu can't be
7144 if (!cpumask_test_cpu(this_cpu,
7145 tsk_cpus_allowed(busiest->curr))) {
7146 raw_spin_unlock_irqrestore(&busiest->lock,
7148 env.flags |= LBF_ALL_PINNED;
7149 goto out_one_pinned;
7153 * ->active_balance synchronizes accesses to
7154 * ->active_balance_work. Once set, it's cleared
7155 * only after active load balance is finished.
7157 if (!busiest->active_balance) {
7158 busiest->active_balance = 1;
7159 busiest->push_cpu = this_cpu;
7162 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7164 if (active_balance) {
7165 stop_one_cpu_nowait(cpu_of(busiest),
7166 active_load_balance_cpu_stop, busiest,
7167 &busiest->active_balance_work);
7171 * We've kicked active balancing, reset the failure
7174 sd->nr_balance_failed = sd->cache_nice_tries+1;
7177 sd->nr_balance_failed = 0;
7179 if (likely(!active_balance)) {
7180 /* We were unbalanced, so reset the balancing interval */
7181 sd->balance_interval = sd->min_interval;
7184 * If we've begun active balancing, start to back off. This
7185 * case may not be covered by the all_pinned logic if there
7186 * is only 1 task on the busy runqueue (because we don't call
7189 if (sd->balance_interval < sd->max_interval)
7190 sd->balance_interval *= 2;
7197 * We reach balance although we may have faced some affinity
7198 * constraints. Clear the imbalance flag if it was set.
7201 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7203 if (*group_imbalance)
7204 *group_imbalance = 0;
7209 * We reach balance because all tasks are pinned at this level so
7210 * we can't migrate them. Let the imbalance flag set so parent level
7211 * can try to migrate them.
7213 schedstat_inc(sd, lb_balanced[idle]);
7215 sd->nr_balance_failed = 0;
7218 /* tune up the balancing interval */
7219 if (((env.flags & LBF_ALL_PINNED) &&
7220 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7221 (sd->balance_interval < sd->max_interval))
7222 sd->balance_interval *= 2;
7229 static inline unsigned long
7230 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7232 unsigned long interval = sd->balance_interval;
7235 interval *= sd->busy_factor;
7237 /* scale ms to jiffies */
7238 interval = msecs_to_jiffies(interval);
7239 interval = clamp(interval, 1UL, max_load_balance_interval);
7245 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7247 unsigned long interval, next;
7249 interval = get_sd_balance_interval(sd, cpu_busy);
7250 next = sd->last_balance + interval;
7252 if (time_after(*next_balance, next))
7253 *next_balance = next;
7257 * idle_balance is called by schedule() if this_cpu is about to become
7258 * idle. Attempts to pull tasks from other CPUs.
7260 static int idle_balance(struct rq *this_rq)
7262 unsigned long next_balance = jiffies + HZ;
7263 int this_cpu = this_rq->cpu;
7264 struct sched_domain *sd;
7265 int pulled_task = 0;
7268 idle_enter_fair(this_rq);
7271 * We must set idle_stamp _before_ calling idle_balance(), such that we
7272 * measure the duration of idle_balance() as idle time.
7274 this_rq->idle_stamp = rq_clock(this_rq);
7276 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7277 !this_rq->rd->overload) {
7279 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7281 update_next_balance(sd, 0, &next_balance);
7287 raw_spin_unlock(&this_rq->lock);
7289 update_blocked_averages(this_cpu);
7291 for_each_domain(this_cpu, sd) {
7292 int continue_balancing = 1;
7293 u64 t0, domain_cost;
7295 if (!(sd->flags & SD_LOAD_BALANCE))
7298 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7299 update_next_balance(sd, 0, &next_balance);
7303 if (sd->flags & SD_BALANCE_NEWIDLE) {
7304 t0 = sched_clock_cpu(this_cpu);
7306 pulled_task = load_balance(this_cpu, this_rq,
7308 &continue_balancing);
7310 domain_cost = sched_clock_cpu(this_cpu) - t0;
7311 if (domain_cost > sd->max_newidle_lb_cost)
7312 sd->max_newidle_lb_cost = domain_cost;
7314 curr_cost += domain_cost;
7317 update_next_balance(sd, 0, &next_balance);
7320 * Stop searching for tasks to pull if there are
7321 * now runnable tasks on this rq.
7323 if (pulled_task || this_rq->nr_running > 0)
7328 raw_spin_lock(&this_rq->lock);
7330 if (curr_cost > this_rq->max_idle_balance_cost)
7331 this_rq->max_idle_balance_cost = curr_cost;
7334 * While browsing the domains, we released the rq lock, a task could
7335 * have been enqueued in the meantime. Since we're not going idle,
7336 * pretend we pulled a task.
7338 if (this_rq->cfs.h_nr_running && !pulled_task)
7342 /* Move the next balance forward */
7343 if (time_after(this_rq->next_balance, next_balance))
7344 this_rq->next_balance = next_balance;
7346 /* Is there a task of a high priority class? */
7347 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7351 idle_exit_fair(this_rq);
7352 this_rq->idle_stamp = 0;
7359 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7360 * running tasks off the busiest CPU onto idle CPUs. It requires at
7361 * least 1 task to be running on each physical CPU where possible, and
7362 * avoids physical / logical imbalances.
7364 static int active_load_balance_cpu_stop(void *data)
7366 struct rq *busiest_rq = data;
7367 int busiest_cpu = cpu_of(busiest_rq);
7368 int target_cpu = busiest_rq->push_cpu;
7369 struct rq *target_rq = cpu_rq(target_cpu);
7370 struct sched_domain *sd;
7371 struct task_struct *p = NULL;
7373 raw_spin_lock_irq(&busiest_rq->lock);
7375 /* make sure the requested cpu hasn't gone down in the meantime */
7376 if (unlikely(busiest_cpu != smp_processor_id() ||
7377 !busiest_rq->active_balance))
7380 /* Is there any task to move? */
7381 if (busiest_rq->nr_running <= 1)
7385 * This condition is "impossible", if it occurs
7386 * we need to fix it. Originally reported by
7387 * Bjorn Helgaas on a 128-cpu setup.
7389 BUG_ON(busiest_rq == target_rq);
7391 /* Search for an sd spanning us and the target CPU. */
7393 for_each_domain(target_cpu, sd) {
7394 if ((sd->flags & SD_LOAD_BALANCE) &&
7395 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7400 struct lb_env env = {
7402 .dst_cpu = target_cpu,
7403 .dst_rq = target_rq,
7404 .src_cpu = busiest_rq->cpu,
7405 .src_rq = busiest_rq,
7409 schedstat_inc(sd, alb_count);
7411 p = detach_one_task(&env);
7413 schedstat_inc(sd, alb_pushed);
7415 schedstat_inc(sd, alb_failed);
7419 busiest_rq->active_balance = 0;
7420 raw_spin_unlock(&busiest_rq->lock);
7423 attach_one_task(target_rq, p);
7430 static inline int on_null_domain(struct rq *rq)
7432 return unlikely(!rcu_dereference_sched(rq->sd));
7435 #ifdef CONFIG_NO_HZ_COMMON
7437 * idle load balancing details
7438 * - When one of the busy CPUs notice that there may be an idle rebalancing
7439 * needed, they will kick the idle load balancer, which then does idle
7440 * load balancing for all the idle CPUs.
7443 cpumask_var_t idle_cpus_mask;
7445 unsigned long next_balance; /* in jiffy units */
7446 } nohz ____cacheline_aligned;
7448 static inline int find_new_ilb(void)
7450 int ilb = cpumask_first(nohz.idle_cpus_mask);
7452 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7459 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7460 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7461 * CPU (if there is one).
7463 static void nohz_balancer_kick(void)
7467 nohz.next_balance++;
7469 ilb_cpu = find_new_ilb();
7471 if (ilb_cpu >= nr_cpu_ids)
7474 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7477 * Use smp_send_reschedule() instead of resched_cpu().
7478 * This way we generate a sched IPI on the target cpu which
7479 * is idle. And the softirq performing nohz idle load balance
7480 * will be run before returning from the IPI.
7482 smp_send_reschedule(ilb_cpu);
7486 static inline void nohz_balance_exit_idle(int cpu)
7488 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7490 * Completely isolated CPUs don't ever set, so we must test.
7492 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7493 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7494 atomic_dec(&nohz.nr_cpus);
7496 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7500 static inline void set_cpu_sd_state_busy(void)
7502 struct sched_domain *sd;
7503 int cpu = smp_processor_id();
7506 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7508 if (!sd || !sd->nohz_idle)
7512 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7517 void set_cpu_sd_state_idle(void)
7519 struct sched_domain *sd;
7520 int cpu = smp_processor_id();
7523 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7525 if (!sd || sd->nohz_idle)
7529 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7535 * This routine will record that the cpu is going idle with tick stopped.
7536 * This info will be used in performing idle load balancing in the future.
7538 void nohz_balance_enter_idle(int cpu)
7541 * If this cpu is going down, then nothing needs to be done.
7543 if (!cpu_active(cpu))
7546 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7550 * If we're a completely isolated CPU, we don't play.
7552 if (on_null_domain(cpu_rq(cpu)))
7555 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7556 atomic_inc(&nohz.nr_cpus);
7557 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7560 static int sched_ilb_notifier(struct notifier_block *nfb,
7561 unsigned long action, void *hcpu)
7563 switch (action & ~CPU_TASKS_FROZEN) {
7565 nohz_balance_exit_idle(smp_processor_id());
7573 static DEFINE_SPINLOCK(balancing);
7576 * Scale the max load_balance interval with the number of CPUs in the system.
7577 * This trades load-balance latency on larger machines for less cross talk.
7579 void update_max_interval(void)
7581 max_load_balance_interval = HZ*num_online_cpus()/10;
7585 * It checks each scheduling domain to see if it is due to be balanced,
7586 * and initiates a balancing operation if so.
7588 * Balancing parameters are set up in init_sched_domains.
7590 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7592 int continue_balancing = 1;
7594 unsigned long interval;
7595 struct sched_domain *sd;
7596 /* Earliest time when we have to do rebalance again */
7597 unsigned long next_balance = jiffies + 60*HZ;
7598 int update_next_balance = 0;
7599 int need_serialize, need_decay = 0;
7602 update_blocked_averages(cpu);
7605 for_each_domain(cpu, sd) {
7607 * Decay the newidle max times here because this is a regular
7608 * visit to all the domains. Decay ~1% per second.
7610 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7611 sd->max_newidle_lb_cost =
7612 (sd->max_newidle_lb_cost * 253) / 256;
7613 sd->next_decay_max_lb_cost = jiffies + HZ;
7616 max_cost += sd->max_newidle_lb_cost;
7618 if (!(sd->flags & SD_LOAD_BALANCE))
7622 * Stop the load balance at this level. There is another
7623 * CPU in our sched group which is doing load balancing more
7626 if (!continue_balancing) {
7632 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7634 need_serialize = sd->flags & SD_SERIALIZE;
7635 if (need_serialize) {
7636 if (!spin_trylock(&balancing))
7640 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7641 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7643 * The LBF_DST_PINNED logic could have changed
7644 * env->dst_cpu, so we can't know our idle
7645 * state even if we migrated tasks. Update it.
7647 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7649 sd->last_balance = jiffies;
7650 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7653 spin_unlock(&balancing);
7655 if (time_after(next_balance, sd->last_balance + interval)) {
7656 next_balance = sd->last_balance + interval;
7657 update_next_balance = 1;
7662 * Ensure the rq-wide value also decays but keep it at a
7663 * reasonable floor to avoid funnies with rq->avg_idle.
7665 rq->max_idle_balance_cost =
7666 max((u64)sysctl_sched_migration_cost, max_cost);
7671 * next_balance will be updated only when there is a need.
7672 * When the cpu is attached to null domain for ex, it will not be
7675 if (likely(update_next_balance)) {
7676 rq->next_balance = next_balance;
7678 #ifdef CONFIG_NO_HZ_COMMON
7680 * If this CPU has been elected to perform the nohz idle
7681 * balance. Other idle CPUs have already rebalanced with
7682 * nohz_idle_balance() and nohz.next_balance has been
7683 * updated accordingly. This CPU is now running the idle load
7684 * balance for itself and we need to update the
7685 * nohz.next_balance accordingly.
7687 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
7688 nohz.next_balance = rq->next_balance;
7693 #ifdef CONFIG_NO_HZ_COMMON
7695 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7696 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7698 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7700 int this_cpu = this_rq->cpu;
7703 /* Earliest time when we have to do rebalance again */
7704 unsigned long next_balance = jiffies + 60*HZ;
7705 int update_next_balance = 0;
7707 if (idle != CPU_IDLE ||
7708 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7711 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7712 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7716 * If this cpu gets work to do, stop the load balancing
7717 * work being done for other cpus. Next load
7718 * balancing owner will pick it up.
7723 rq = cpu_rq(balance_cpu);
7726 * If time for next balance is due,
7729 if (time_after_eq(jiffies, rq->next_balance)) {
7730 raw_spin_lock_irq(&rq->lock);
7731 update_rq_clock(rq);
7732 update_idle_cpu_load(rq);
7733 raw_spin_unlock_irq(&rq->lock);
7734 rebalance_domains(rq, CPU_IDLE);
7737 if (time_after(next_balance, rq->next_balance)) {
7738 next_balance = rq->next_balance;
7739 update_next_balance = 1;
7744 * next_balance will be updated only when there is a need.
7745 * When the CPU is attached to null domain for ex, it will not be
7748 if (likely(update_next_balance))
7749 nohz.next_balance = next_balance;
7751 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7755 * Current heuristic for kicking the idle load balancer in the presence
7756 * of an idle cpu in the system.
7757 * - This rq has more than one task.
7758 * - This rq has at least one CFS task and the capacity of the CPU is
7759 * significantly reduced because of RT tasks or IRQs.
7760 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
7761 * multiple busy cpu.
7762 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7763 * domain span are idle.
7765 static inline bool nohz_kick_needed(struct rq *rq)
7767 unsigned long now = jiffies;
7768 struct sched_domain *sd;
7769 struct sched_group_capacity *sgc;
7770 int nr_busy, cpu = rq->cpu;
7773 if (unlikely(rq->idle_balance))
7777 * We may be recently in ticked or tickless idle mode. At the first
7778 * busy tick after returning from idle, we will update the busy stats.
7780 set_cpu_sd_state_busy();
7781 nohz_balance_exit_idle(cpu);
7784 * None are in tickless mode and hence no need for NOHZ idle load
7787 if (likely(!atomic_read(&nohz.nr_cpus)))
7790 if (time_before(now, nohz.next_balance))
7793 if (rq->nr_running >= 2)
7797 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7799 sgc = sd->groups->sgc;
7800 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7809 sd = rcu_dereference(rq->sd);
7811 if ((rq->cfs.h_nr_running >= 1) &&
7812 check_cpu_capacity(rq, sd)) {
7818 sd = rcu_dereference(per_cpu(sd_asym, cpu));
7819 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7820 sched_domain_span(sd)) < cpu)) {
7830 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7834 * run_rebalance_domains is triggered when needed from the scheduler tick.
7835 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7837 static void run_rebalance_domains(struct softirq_action *h)
7839 struct rq *this_rq = this_rq();
7840 enum cpu_idle_type idle = this_rq->idle_balance ?
7841 CPU_IDLE : CPU_NOT_IDLE;
7844 * If this cpu has a pending nohz_balance_kick, then do the
7845 * balancing on behalf of the other idle cpus whose ticks are
7846 * stopped. Do nohz_idle_balance *before* rebalance_domains to
7847 * give the idle cpus a chance to load balance. Else we may
7848 * load balance only within the local sched_domain hierarchy
7849 * and abort nohz_idle_balance altogether if we pull some load.
7851 nohz_idle_balance(this_rq, idle);
7852 rebalance_domains(this_rq, idle);
7856 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7858 void trigger_load_balance(struct rq *rq)
7860 /* Don't need to rebalance while attached to NULL domain */
7861 if (unlikely(on_null_domain(rq)))
7864 if (time_after_eq(jiffies, rq->next_balance))
7865 raise_softirq(SCHED_SOFTIRQ);
7866 #ifdef CONFIG_NO_HZ_COMMON
7867 if (nohz_kick_needed(rq))
7868 nohz_balancer_kick();
7872 static void rq_online_fair(struct rq *rq)
7876 update_runtime_enabled(rq);
7879 static void rq_offline_fair(struct rq *rq)
7883 /* Ensure any throttled groups are reachable by pick_next_task */
7884 unthrottle_offline_cfs_rqs(rq);
7887 #endif /* CONFIG_SMP */
7890 * scheduler tick hitting a task of our scheduling class:
7892 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7894 struct cfs_rq *cfs_rq;
7895 struct sched_entity *se = &curr->se;
7897 for_each_sched_entity(se) {
7898 cfs_rq = cfs_rq_of(se);
7899 entity_tick(cfs_rq, se, queued);
7902 if (static_branch_unlikely(&sched_numa_balancing))
7903 task_tick_numa(rq, curr);
7907 * called on fork with the child task as argument from the parent's context
7908 * - child not yet on the tasklist
7909 * - preemption disabled
7911 static void task_fork_fair(struct task_struct *p)
7913 struct cfs_rq *cfs_rq;
7914 struct sched_entity *se = &p->se, *curr;
7915 int this_cpu = smp_processor_id();
7916 struct rq *rq = this_rq();
7917 unsigned long flags;
7919 raw_spin_lock_irqsave(&rq->lock, flags);
7921 update_rq_clock(rq);
7923 cfs_rq = task_cfs_rq(current);
7924 curr = cfs_rq->curr;
7927 * Not only the cpu but also the task_group of the parent might have
7928 * been changed after parent->se.parent,cfs_rq were copied to
7929 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7930 * of child point to valid ones.
7933 __set_task_cpu(p, this_cpu);
7936 update_curr(cfs_rq);
7939 se->vruntime = curr->vruntime;
7940 place_entity(cfs_rq, se, 1);
7942 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7944 * Upon rescheduling, sched_class::put_prev_task() will place
7945 * 'current' within the tree based on its new key value.
7947 swap(curr->vruntime, se->vruntime);
7951 se->vruntime -= cfs_rq->min_vruntime;
7953 raw_spin_unlock_irqrestore(&rq->lock, flags);
7957 * Priority of the task has changed. Check to see if we preempt
7961 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7963 if (!task_on_rq_queued(p))
7967 * Reschedule if we are currently running on this runqueue and
7968 * our priority decreased, or if we are not currently running on
7969 * this runqueue and our priority is higher than the current's
7971 if (rq->curr == p) {
7972 if (p->prio > oldprio)
7975 check_preempt_curr(rq, p, 0);
7978 static inline bool vruntime_normalized(struct task_struct *p)
7980 struct sched_entity *se = &p->se;
7983 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
7984 * the dequeue_entity(.flags=0) will already have normalized the
7991 * When !on_rq, vruntime of the task has usually NOT been normalized.
7992 * But there are some cases where it has already been normalized:
7994 * - A forked child which is waiting for being woken up by
7995 * wake_up_new_task().
7996 * - A task which has been woken up by try_to_wake_up() and
7997 * waiting for actually being woken up by sched_ttwu_pending().
7999 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8005 static void detach_task_cfs_rq(struct task_struct *p)
8007 struct sched_entity *se = &p->se;
8008 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8010 if (!vruntime_normalized(p)) {
8012 * Fix up our vruntime so that the current sleep doesn't
8013 * cause 'unlimited' sleep bonus.
8015 place_entity(cfs_rq, se, 0);
8016 se->vruntime -= cfs_rq->min_vruntime;
8019 /* Catch up with the cfs_rq and remove our load when we leave */
8020 detach_entity_load_avg(cfs_rq, se);
8023 static void attach_task_cfs_rq(struct task_struct *p)
8025 struct sched_entity *se = &p->se;
8026 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8028 #ifdef CONFIG_FAIR_GROUP_SCHED
8030 * Since the real-depth could have been changed (only FAIR
8031 * class maintain depth value), reset depth properly.
8033 se->depth = se->parent ? se->parent->depth + 1 : 0;
8036 /* Synchronize task with its cfs_rq */
8037 attach_entity_load_avg(cfs_rq, se);
8039 if (!vruntime_normalized(p))
8040 se->vruntime += cfs_rq->min_vruntime;
8043 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8045 detach_task_cfs_rq(p);
8048 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8050 attach_task_cfs_rq(p);
8052 if (task_on_rq_queued(p)) {
8054 * We were most likely switched from sched_rt, so
8055 * kick off the schedule if running, otherwise just see
8056 * if we can still preempt the current task.
8061 check_preempt_curr(rq, p, 0);
8065 /* Account for a task changing its policy or group.
8067 * This routine is mostly called to set cfs_rq->curr field when a task
8068 * migrates between groups/classes.
8070 static void set_curr_task_fair(struct rq *rq)
8072 struct sched_entity *se = &rq->curr->se;
8074 for_each_sched_entity(se) {
8075 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8077 set_next_entity(cfs_rq, se);
8078 /* ensure bandwidth has been allocated on our new cfs_rq */
8079 account_cfs_rq_runtime(cfs_rq, 0);
8083 void init_cfs_rq(struct cfs_rq *cfs_rq)
8085 cfs_rq->tasks_timeline = RB_ROOT;
8086 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8087 #ifndef CONFIG_64BIT
8088 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8091 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8092 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8096 #ifdef CONFIG_FAIR_GROUP_SCHED
8097 static void task_move_group_fair(struct task_struct *p)
8099 detach_task_cfs_rq(p);
8100 set_task_rq(p, task_cpu(p));
8103 /* Tell se's cfs_rq has been changed -- migrated */
8104 p->se.avg.last_update_time = 0;
8106 attach_task_cfs_rq(p);
8109 void free_fair_sched_group(struct task_group *tg)
8113 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8115 for_each_possible_cpu(i) {
8117 kfree(tg->cfs_rq[i]);
8120 remove_entity_load_avg(tg->se[i]);
8129 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8131 struct cfs_rq *cfs_rq;
8132 struct sched_entity *se;
8135 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8138 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8142 tg->shares = NICE_0_LOAD;
8144 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8146 for_each_possible_cpu(i) {
8147 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8148 GFP_KERNEL, cpu_to_node(i));
8152 se = kzalloc_node(sizeof(struct sched_entity),
8153 GFP_KERNEL, cpu_to_node(i));
8157 init_cfs_rq(cfs_rq);
8158 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8159 init_entity_runnable_average(se);
8170 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8172 struct rq *rq = cpu_rq(cpu);
8173 unsigned long flags;
8176 * Only empty task groups can be destroyed; so we can speculatively
8177 * check on_list without danger of it being re-added.
8179 if (!tg->cfs_rq[cpu]->on_list)
8182 raw_spin_lock_irqsave(&rq->lock, flags);
8183 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8184 raw_spin_unlock_irqrestore(&rq->lock, flags);
8187 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8188 struct sched_entity *se, int cpu,
8189 struct sched_entity *parent)
8191 struct rq *rq = cpu_rq(cpu);
8195 init_cfs_rq_runtime(cfs_rq);
8197 tg->cfs_rq[cpu] = cfs_rq;
8200 /* se could be NULL for root_task_group */
8205 se->cfs_rq = &rq->cfs;
8208 se->cfs_rq = parent->my_q;
8209 se->depth = parent->depth + 1;
8213 /* guarantee group entities always have weight */
8214 update_load_set(&se->load, NICE_0_LOAD);
8215 se->parent = parent;
8218 static DEFINE_MUTEX(shares_mutex);
8220 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8223 unsigned long flags;
8226 * We can't change the weight of the root cgroup.
8231 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8233 mutex_lock(&shares_mutex);
8234 if (tg->shares == shares)
8237 tg->shares = shares;
8238 for_each_possible_cpu(i) {
8239 struct rq *rq = cpu_rq(i);
8240 struct sched_entity *se;
8243 /* Propagate contribution to hierarchy */
8244 raw_spin_lock_irqsave(&rq->lock, flags);
8246 /* Possible calls to update_curr() need rq clock */
8247 update_rq_clock(rq);
8248 for_each_sched_entity(se)
8249 update_cfs_shares(group_cfs_rq(se));
8250 raw_spin_unlock_irqrestore(&rq->lock, flags);
8254 mutex_unlock(&shares_mutex);
8257 #else /* CONFIG_FAIR_GROUP_SCHED */
8259 void free_fair_sched_group(struct task_group *tg) { }
8261 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8266 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8268 #endif /* CONFIG_FAIR_GROUP_SCHED */
8271 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8273 struct sched_entity *se = &task->se;
8274 unsigned int rr_interval = 0;
8277 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8280 if (rq->cfs.load.weight)
8281 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8287 * All the scheduling class methods:
8289 const struct sched_class fair_sched_class = {
8290 .next = &idle_sched_class,
8291 .enqueue_task = enqueue_task_fair,
8292 .dequeue_task = dequeue_task_fair,
8293 .yield_task = yield_task_fair,
8294 .yield_to_task = yield_to_task_fair,
8296 .check_preempt_curr = check_preempt_wakeup,
8298 .pick_next_task = pick_next_task_fair,
8299 .put_prev_task = put_prev_task_fair,
8302 .select_task_rq = select_task_rq_fair,
8303 .migrate_task_rq = migrate_task_rq_fair,
8305 .rq_online = rq_online_fair,
8306 .rq_offline = rq_offline_fair,
8308 .task_waking = task_waking_fair,
8309 .task_dead = task_dead_fair,
8310 .set_cpus_allowed = set_cpus_allowed_common,
8313 .set_curr_task = set_curr_task_fair,
8314 .task_tick = task_tick_fair,
8315 .task_fork = task_fork_fair,
8317 .prio_changed = prio_changed_fair,
8318 .switched_from = switched_from_fair,
8319 .switched_to = switched_to_fair,
8321 .get_rr_interval = get_rr_interval_fair,
8323 .update_curr = update_curr_fair,
8325 #ifdef CONFIG_FAIR_GROUP_SCHED
8326 .task_move_group = task_move_group_fair,
8330 #ifdef CONFIG_SCHED_DEBUG
8331 void print_cfs_stats(struct seq_file *m, int cpu)
8333 struct cfs_rq *cfs_rq;
8336 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8337 print_cfs_rq(m, cpu, cfs_rq);
8341 #ifdef CONFIG_NUMA_BALANCING
8342 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8345 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8347 for_each_online_node(node) {
8348 if (p->numa_faults) {
8349 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8350 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8352 if (p->numa_group) {
8353 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8354 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8356 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8359 #endif /* CONFIG_NUMA_BALANCING */
8360 #endif /* CONFIG_SCHED_DEBUG */
8362 __init void init_sched_fair_class(void)
8365 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8367 #ifdef CONFIG_NO_HZ_COMMON
8368 nohz.next_balance = jiffies;
8369 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8370 cpu_notifier(sched_ilb_notifier, 0);