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);
2685 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2686 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2688 struct sched_avg *sa = &cfs_rq->avg;
2689 int decayed, removed = 0;
2691 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2692 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2693 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2694 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2698 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2699 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2700 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2701 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2704 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2705 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2707 #ifndef CONFIG_64BIT
2709 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2712 return decayed || removed;
2715 /* Update task and its cfs_rq load average */
2716 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2718 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2719 u64 now = cfs_rq_clock_task(cfs_rq);
2720 int cpu = cpu_of(rq_of(cfs_rq));
2723 * Track task load average for carrying it to new CPU after migrated, and
2724 * track group sched_entity load average for task_h_load calc in migration
2726 __update_load_avg(now, cpu, &se->avg,
2727 se->on_rq * scale_load_down(se->load.weight),
2728 cfs_rq->curr == se, NULL);
2730 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2731 update_tg_load_avg(cfs_rq, 0);
2734 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2736 if (!sched_feat(ATTACH_AGE_LOAD))
2740 * If we got migrated (either between CPUs or between cgroups) we'll
2741 * have aged the average right before clearing @last_update_time.
2743 if (se->avg.last_update_time) {
2744 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2745 &se->avg, 0, 0, NULL);
2748 * XXX: we could have just aged the entire load away if we've been
2749 * absent from the fair class for too long.
2754 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2755 cfs_rq->avg.load_avg += se->avg.load_avg;
2756 cfs_rq->avg.load_sum += se->avg.load_sum;
2757 cfs_rq->avg.util_avg += se->avg.util_avg;
2758 cfs_rq->avg.util_sum += se->avg.util_sum;
2761 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2763 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2764 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2765 cfs_rq->curr == se, NULL);
2767 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2768 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2769 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2770 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2773 /* Add the load generated by se into cfs_rq's load average */
2775 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2777 struct sched_avg *sa = &se->avg;
2778 u64 now = cfs_rq_clock_task(cfs_rq);
2779 int migrated, decayed;
2781 migrated = !sa->last_update_time;
2783 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2784 se->on_rq * scale_load_down(se->load.weight),
2785 cfs_rq->curr == se, NULL);
2788 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2790 cfs_rq->runnable_load_avg += sa->load_avg;
2791 cfs_rq->runnable_load_sum += sa->load_sum;
2794 attach_entity_load_avg(cfs_rq, se);
2796 if (decayed || migrated)
2797 update_tg_load_avg(cfs_rq, 0);
2800 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2802 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2804 update_load_avg(se, 1);
2806 cfs_rq->runnable_load_avg =
2807 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2808 cfs_rq->runnable_load_sum =
2809 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2813 * Task first catches up with cfs_rq, and then subtract
2814 * itself from the cfs_rq (task must be off the queue now).
2816 void remove_entity_load_avg(struct sched_entity *se)
2818 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2819 u64 last_update_time;
2821 #ifndef CONFIG_64BIT
2822 u64 last_update_time_copy;
2825 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2827 last_update_time = cfs_rq->avg.last_update_time;
2828 } while (last_update_time != last_update_time_copy);
2830 last_update_time = cfs_rq->avg.last_update_time;
2833 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2834 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2835 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2839 * Update the rq's load with the elapsed running time before entering
2840 * idle. if the last scheduled task is not a CFS task, idle_enter will
2841 * be the only way to update the runnable statistic.
2843 void idle_enter_fair(struct rq *this_rq)
2848 * Update the rq's load with the elapsed idle time before a task is
2849 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2850 * be the only way to update the runnable statistic.
2852 void idle_exit_fair(struct rq *this_rq)
2856 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2858 return cfs_rq->runnable_load_avg;
2861 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2863 return cfs_rq->avg.load_avg;
2866 static int idle_balance(struct rq *this_rq);
2868 #else /* CONFIG_SMP */
2870 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2872 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2874 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2875 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2878 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2880 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2882 static inline int idle_balance(struct rq *rq)
2887 #endif /* CONFIG_SMP */
2889 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2891 #ifdef CONFIG_SCHEDSTATS
2892 struct task_struct *tsk = NULL;
2894 if (entity_is_task(se))
2897 if (se->statistics.sleep_start) {
2898 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2903 if (unlikely(delta > se->statistics.sleep_max))
2904 se->statistics.sleep_max = delta;
2906 se->statistics.sleep_start = 0;
2907 se->statistics.sum_sleep_runtime += delta;
2910 account_scheduler_latency(tsk, delta >> 10, 1);
2911 trace_sched_stat_sleep(tsk, delta);
2914 if (se->statistics.block_start) {
2915 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2920 if (unlikely(delta > se->statistics.block_max))
2921 se->statistics.block_max = delta;
2923 se->statistics.block_start = 0;
2924 se->statistics.sum_sleep_runtime += delta;
2927 if (tsk->in_iowait) {
2928 se->statistics.iowait_sum += delta;
2929 se->statistics.iowait_count++;
2930 trace_sched_stat_iowait(tsk, delta);
2933 trace_sched_stat_blocked(tsk, delta);
2934 trace_sched_blocked_reason(tsk);
2937 * Blocking time is in units of nanosecs, so shift by
2938 * 20 to get a milliseconds-range estimation of the
2939 * amount of time that the task spent sleeping:
2941 if (unlikely(prof_on == SLEEP_PROFILING)) {
2942 profile_hits(SLEEP_PROFILING,
2943 (void *)get_wchan(tsk),
2946 account_scheduler_latency(tsk, delta >> 10, 0);
2952 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2954 #ifdef CONFIG_SCHED_DEBUG
2955 s64 d = se->vruntime - cfs_rq->min_vruntime;
2960 if (d > 3*sysctl_sched_latency)
2961 schedstat_inc(cfs_rq, nr_spread_over);
2966 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2968 u64 vruntime = cfs_rq->min_vruntime;
2971 * The 'current' period is already promised to the current tasks,
2972 * however the extra weight of the new task will slow them down a
2973 * little, place the new task so that it fits in the slot that
2974 * stays open at the end.
2976 if (initial && sched_feat(START_DEBIT))
2977 vruntime += sched_vslice(cfs_rq, se);
2979 /* sleeps up to a single latency don't count. */
2981 unsigned long thresh = sysctl_sched_latency;
2984 * Halve their sleep time's effect, to allow
2985 * for a gentler effect of sleepers:
2987 if (sched_feat(GENTLE_FAIR_SLEEPERS))
2993 /* ensure we never gain time by being placed backwards. */
2994 se->vruntime = max_vruntime(se->vruntime, vruntime);
2997 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3000 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3003 * Update the normalized vruntime before updating min_vruntime
3004 * through calling update_curr().
3006 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3007 se->vruntime += cfs_rq->min_vruntime;
3010 * Update run-time statistics of the 'current'.
3012 update_curr(cfs_rq);
3013 enqueue_entity_load_avg(cfs_rq, se);
3014 account_entity_enqueue(cfs_rq, se);
3015 update_cfs_shares(cfs_rq);
3017 if (flags & ENQUEUE_WAKEUP) {
3018 place_entity(cfs_rq, se, 0);
3019 enqueue_sleeper(cfs_rq, se);
3022 update_stats_enqueue(cfs_rq, se);
3023 check_spread(cfs_rq, se);
3024 if (se != cfs_rq->curr)
3025 __enqueue_entity(cfs_rq, se);
3028 if (cfs_rq->nr_running == 1) {
3029 list_add_leaf_cfs_rq(cfs_rq);
3030 check_enqueue_throttle(cfs_rq);
3034 static void __clear_buddies_last(struct sched_entity *se)
3036 for_each_sched_entity(se) {
3037 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3038 if (cfs_rq->last != se)
3041 cfs_rq->last = NULL;
3045 static void __clear_buddies_next(struct sched_entity *se)
3047 for_each_sched_entity(se) {
3048 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3049 if (cfs_rq->next != se)
3052 cfs_rq->next = NULL;
3056 static void __clear_buddies_skip(struct sched_entity *se)
3058 for_each_sched_entity(se) {
3059 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3060 if (cfs_rq->skip != se)
3063 cfs_rq->skip = NULL;
3067 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3069 if (cfs_rq->last == se)
3070 __clear_buddies_last(se);
3072 if (cfs_rq->next == se)
3073 __clear_buddies_next(se);
3075 if (cfs_rq->skip == se)
3076 __clear_buddies_skip(se);
3079 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3082 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3085 * Update run-time statistics of the 'current'.
3087 update_curr(cfs_rq);
3088 dequeue_entity_load_avg(cfs_rq, se);
3090 update_stats_dequeue(cfs_rq, se);
3091 if (flags & DEQUEUE_SLEEP) {
3092 #ifdef CONFIG_SCHEDSTATS
3093 if (entity_is_task(se)) {
3094 struct task_struct *tsk = task_of(se);
3096 if (tsk->state & TASK_INTERRUPTIBLE)
3097 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3098 if (tsk->state & TASK_UNINTERRUPTIBLE)
3099 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3104 clear_buddies(cfs_rq, se);
3106 if (se != cfs_rq->curr)
3107 __dequeue_entity(cfs_rq, se);
3109 account_entity_dequeue(cfs_rq, se);
3112 * Normalize the entity after updating the min_vruntime because the
3113 * update can refer to the ->curr item and we need to reflect this
3114 * movement in our normalized position.
3116 if (!(flags & DEQUEUE_SLEEP))
3117 se->vruntime -= cfs_rq->min_vruntime;
3119 /* return excess runtime on last dequeue */
3120 return_cfs_rq_runtime(cfs_rq);
3122 update_min_vruntime(cfs_rq);
3123 update_cfs_shares(cfs_rq);
3127 * Preempt the current task with a newly woken task if needed:
3130 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3132 unsigned long ideal_runtime, delta_exec;
3133 struct sched_entity *se;
3136 ideal_runtime = sched_slice(cfs_rq, curr);
3137 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3138 if (delta_exec > ideal_runtime) {
3139 resched_curr(rq_of(cfs_rq));
3141 * The current task ran long enough, ensure it doesn't get
3142 * re-elected due to buddy favours.
3144 clear_buddies(cfs_rq, curr);
3149 * Ensure that a task that missed wakeup preemption by a
3150 * narrow margin doesn't have to wait for a full slice.
3151 * This also mitigates buddy induced latencies under load.
3153 if (delta_exec < sysctl_sched_min_granularity)
3156 se = __pick_first_entity(cfs_rq);
3157 delta = curr->vruntime - se->vruntime;
3162 if (delta > ideal_runtime)
3163 resched_curr(rq_of(cfs_rq));
3167 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3169 /* 'current' is not kept within the tree. */
3172 * Any task has to be enqueued before it get to execute on
3173 * a CPU. So account for the time it spent waiting on the
3176 update_stats_wait_end(cfs_rq, se);
3177 __dequeue_entity(cfs_rq, se);
3178 update_load_avg(se, 1);
3181 update_stats_curr_start(cfs_rq, se);
3183 #ifdef CONFIG_SCHEDSTATS
3185 * Track our maximum slice length, if the CPU's load is at
3186 * least twice that of our own weight (i.e. dont track it
3187 * when there are only lesser-weight tasks around):
3189 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3190 se->statistics.slice_max = max(se->statistics.slice_max,
3191 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3194 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3198 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3201 * Pick the next process, keeping these things in mind, in this order:
3202 * 1) keep things fair between processes/task groups
3203 * 2) pick the "next" process, since someone really wants that to run
3204 * 3) pick the "last" process, for cache locality
3205 * 4) do not run the "skip" process, if something else is available
3207 static struct sched_entity *
3208 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3210 struct sched_entity *left = __pick_first_entity(cfs_rq);
3211 struct sched_entity *se;
3214 * If curr is set we have to see if its left of the leftmost entity
3215 * still in the tree, provided there was anything in the tree at all.
3217 if (!left || (curr && entity_before(curr, left)))
3220 se = left; /* ideally we run the leftmost entity */
3223 * Avoid running the skip buddy, if running something else can
3224 * be done without getting too unfair.
3226 if (cfs_rq->skip == se) {
3227 struct sched_entity *second;
3230 second = __pick_first_entity(cfs_rq);
3232 second = __pick_next_entity(se);
3233 if (!second || (curr && entity_before(curr, second)))
3237 if (second && wakeup_preempt_entity(second, left) < 1)
3242 * Prefer last buddy, try to return the CPU to a preempted task.
3244 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3248 * Someone really wants this to run. If it's not unfair, run it.
3250 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3253 clear_buddies(cfs_rq, se);
3258 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3260 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3263 * If still on the runqueue then deactivate_task()
3264 * was not called and update_curr() has to be done:
3267 update_curr(cfs_rq);
3269 /* throttle cfs_rqs exceeding runtime */
3270 check_cfs_rq_runtime(cfs_rq);
3272 check_spread(cfs_rq, prev);
3274 update_stats_wait_start(cfs_rq, prev);
3275 /* Put 'current' back into the tree. */
3276 __enqueue_entity(cfs_rq, prev);
3277 /* in !on_rq case, update occurred at dequeue */
3278 update_load_avg(prev, 0);
3280 cfs_rq->curr = NULL;
3284 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3287 * Update run-time statistics of the 'current'.
3289 update_curr(cfs_rq);
3292 * Ensure that runnable average is periodically updated.
3294 update_load_avg(curr, 1);
3295 update_cfs_shares(cfs_rq);
3297 #ifdef CONFIG_SCHED_HRTICK
3299 * queued ticks are scheduled to match the slice, so don't bother
3300 * validating it and just reschedule.
3303 resched_curr(rq_of(cfs_rq));
3307 * don't let the period tick interfere with the hrtick preemption
3309 if (!sched_feat(DOUBLE_TICK) &&
3310 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3314 if (cfs_rq->nr_running > 1)
3315 check_preempt_tick(cfs_rq, curr);
3319 /**************************************************
3320 * CFS bandwidth control machinery
3323 #ifdef CONFIG_CFS_BANDWIDTH
3325 #ifdef HAVE_JUMP_LABEL
3326 static struct static_key __cfs_bandwidth_used;
3328 static inline bool cfs_bandwidth_used(void)
3330 return static_key_false(&__cfs_bandwidth_used);
3333 void cfs_bandwidth_usage_inc(void)
3335 static_key_slow_inc(&__cfs_bandwidth_used);
3338 void cfs_bandwidth_usage_dec(void)
3340 static_key_slow_dec(&__cfs_bandwidth_used);
3342 #else /* HAVE_JUMP_LABEL */
3343 static bool cfs_bandwidth_used(void)
3348 void cfs_bandwidth_usage_inc(void) {}
3349 void cfs_bandwidth_usage_dec(void) {}
3350 #endif /* HAVE_JUMP_LABEL */
3353 * default period for cfs group bandwidth.
3354 * default: 0.1s, units: nanoseconds
3356 static inline u64 default_cfs_period(void)
3358 return 100000000ULL;
3361 static inline u64 sched_cfs_bandwidth_slice(void)
3363 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3367 * Replenish runtime according to assigned quota and update expiration time.
3368 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3369 * additional synchronization around rq->lock.
3371 * requires cfs_b->lock
3373 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3377 if (cfs_b->quota == RUNTIME_INF)
3380 now = sched_clock_cpu(smp_processor_id());
3381 cfs_b->runtime = cfs_b->quota;
3382 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3385 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3387 return &tg->cfs_bandwidth;
3390 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3391 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3393 if (unlikely(cfs_rq->throttle_count))
3394 return cfs_rq->throttled_clock_task;
3396 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3399 /* returns 0 on failure to allocate runtime */
3400 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3402 struct task_group *tg = cfs_rq->tg;
3403 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3404 u64 amount = 0, min_amount, expires;
3406 /* note: this is a positive sum as runtime_remaining <= 0 */
3407 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3409 raw_spin_lock(&cfs_b->lock);
3410 if (cfs_b->quota == RUNTIME_INF)
3411 amount = min_amount;
3413 start_cfs_bandwidth(cfs_b);
3415 if (cfs_b->runtime > 0) {
3416 amount = min(cfs_b->runtime, min_amount);
3417 cfs_b->runtime -= amount;
3421 expires = cfs_b->runtime_expires;
3422 raw_spin_unlock(&cfs_b->lock);
3424 cfs_rq->runtime_remaining += amount;
3426 * we may have advanced our local expiration to account for allowed
3427 * spread between our sched_clock and the one on which runtime was
3430 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3431 cfs_rq->runtime_expires = expires;
3433 return cfs_rq->runtime_remaining > 0;
3437 * Note: This depends on the synchronization provided by sched_clock and the
3438 * fact that rq->clock snapshots this value.
3440 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3442 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3444 /* if the deadline is ahead of our clock, nothing to do */
3445 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3448 if (cfs_rq->runtime_remaining < 0)
3452 * If the local deadline has passed we have to consider the
3453 * possibility that our sched_clock is 'fast' and the global deadline
3454 * has not truly expired.
3456 * Fortunately we can check determine whether this the case by checking
3457 * whether the global deadline has advanced. It is valid to compare
3458 * cfs_b->runtime_expires without any locks since we only care about
3459 * exact equality, so a partial write will still work.
3462 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3463 /* extend local deadline, drift is bounded above by 2 ticks */
3464 cfs_rq->runtime_expires += TICK_NSEC;
3466 /* global deadline is ahead, expiration has passed */
3467 cfs_rq->runtime_remaining = 0;
3471 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3473 /* dock delta_exec before expiring quota (as it could span periods) */
3474 cfs_rq->runtime_remaining -= delta_exec;
3475 expire_cfs_rq_runtime(cfs_rq);
3477 if (likely(cfs_rq->runtime_remaining > 0))
3481 * if we're unable to extend our runtime we resched so that the active
3482 * hierarchy can be throttled
3484 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3485 resched_curr(rq_of(cfs_rq));
3488 static __always_inline
3489 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3491 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3494 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3497 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3499 return cfs_bandwidth_used() && cfs_rq->throttled;
3502 /* check whether cfs_rq, or any parent, is throttled */
3503 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3505 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3509 * Ensure that neither of the group entities corresponding to src_cpu or
3510 * dest_cpu are members of a throttled hierarchy when performing group
3511 * load-balance operations.
3513 static inline int throttled_lb_pair(struct task_group *tg,
3514 int src_cpu, int dest_cpu)
3516 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3518 src_cfs_rq = tg->cfs_rq[src_cpu];
3519 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3521 return throttled_hierarchy(src_cfs_rq) ||
3522 throttled_hierarchy(dest_cfs_rq);
3525 /* updated child weight may affect parent so we have to do this bottom up */
3526 static int tg_unthrottle_up(struct task_group *tg, void *data)
3528 struct rq *rq = data;
3529 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3531 cfs_rq->throttle_count--;
3533 if (!cfs_rq->throttle_count) {
3534 /* adjust cfs_rq_clock_task() */
3535 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3536 cfs_rq->throttled_clock_task;
3543 static int tg_throttle_down(struct task_group *tg, void *data)
3545 struct rq *rq = data;
3546 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3548 /* group is entering throttled state, stop time */
3549 if (!cfs_rq->throttle_count)
3550 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3551 cfs_rq->throttle_count++;
3556 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3558 struct rq *rq = rq_of(cfs_rq);
3559 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3560 struct sched_entity *se;
3561 long task_delta, dequeue = 1;
3564 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3566 /* freeze hierarchy runnable averages while throttled */
3568 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3571 task_delta = cfs_rq->h_nr_running;
3572 for_each_sched_entity(se) {
3573 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3574 /* throttled entity or throttle-on-deactivate */
3579 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3580 qcfs_rq->h_nr_running -= task_delta;
3582 if (qcfs_rq->load.weight)
3587 sub_nr_running(rq, task_delta);
3589 cfs_rq->throttled = 1;
3590 cfs_rq->throttled_clock = rq_clock(rq);
3591 raw_spin_lock(&cfs_b->lock);
3592 empty = list_empty(&cfs_b->throttled_cfs_rq);
3595 * Add to the _head_ of the list, so that an already-started
3596 * distribute_cfs_runtime will not see us
3598 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3601 * If we're the first throttled task, make sure the bandwidth
3605 start_cfs_bandwidth(cfs_b);
3607 raw_spin_unlock(&cfs_b->lock);
3610 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3612 struct rq *rq = rq_of(cfs_rq);
3613 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3614 struct sched_entity *se;
3618 se = cfs_rq->tg->se[cpu_of(rq)];
3620 cfs_rq->throttled = 0;
3622 update_rq_clock(rq);
3624 raw_spin_lock(&cfs_b->lock);
3625 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3626 list_del_rcu(&cfs_rq->throttled_list);
3627 raw_spin_unlock(&cfs_b->lock);
3629 /* update hierarchical throttle state */
3630 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3632 if (!cfs_rq->load.weight)
3635 task_delta = cfs_rq->h_nr_running;
3636 for_each_sched_entity(se) {
3640 cfs_rq = cfs_rq_of(se);
3642 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3643 cfs_rq->h_nr_running += task_delta;
3645 if (cfs_rq_throttled(cfs_rq))
3650 add_nr_running(rq, task_delta);
3652 /* determine whether we need to wake up potentially idle cpu */
3653 if (rq->curr == rq->idle && rq->cfs.nr_running)
3657 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3658 u64 remaining, u64 expires)
3660 struct cfs_rq *cfs_rq;
3662 u64 starting_runtime = remaining;
3665 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3667 struct rq *rq = rq_of(cfs_rq);
3669 raw_spin_lock(&rq->lock);
3670 if (!cfs_rq_throttled(cfs_rq))
3673 runtime = -cfs_rq->runtime_remaining + 1;
3674 if (runtime > remaining)
3675 runtime = remaining;
3676 remaining -= runtime;
3678 cfs_rq->runtime_remaining += runtime;
3679 cfs_rq->runtime_expires = expires;
3681 /* we check whether we're throttled above */
3682 if (cfs_rq->runtime_remaining > 0)
3683 unthrottle_cfs_rq(cfs_rq);
3686 raw_spin_unlock(&rq->lock);
3693 return starting_runtime - remaining;
3697 * Responsible for refilling a task_group's bandwidth and unthrottling its
3698 * cfs_rqs as appropriate. If there has been no activity within the last
3699 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3700 * used to track this state.
3702 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3704 u64 runtime, runtime_expires;
3707 /* no need to continue the timer with no bandwidth constraint */
3708 if (cfs_b->quota == RUNTIME_INF)
3709 goto out_deactivate;
3711 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3712 cfs_b->nr_periods += overrun;
3715 * idle depends on !throttled (for the case of a large deficit), and if
3716 * we're going inactive then everything else can be deferred
3718 if (cfs_b->idle && !throttled)
3719 goto out_deactivate;
3721 __refill_cfs_bandwidth_runtime(cfs_b);
3724 /* mark as potentially idle for the upcoming period */
3729 /* account preceding periods in which throttling occurred */
3730 cfs_b->nr_throttled += overrun;
3732 runtime_expires = cfs_b->runtime_expires;
3735 * This check is repeated as we are holding onto the new bandwidth while
3736 * we unthrottle. This can potentially race with an unthrottled group
3737 * trying to acquire new bandwidth from the global pool. This can result
3738 * in us over-using our runtime if it is all used during this loop, but
3739 * only by limited amounts in that extreme case.
3741 while (throttled && cfs_b->runtime > 0) {
3742 runtime = cfs_b->runtime;
3743 raw_spin_unlock(&cfs_b->lock);
3744 /* we can't nest cfs_b->lock while distributing bandwidth */
3745 runtime = distribute_cfs_runtime(cfs_b, runtime,
3747 raw_spin_lock(&cfs_b->lock);
3749 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3751 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3755 * While we are ensured activity in the period following an
3756 * unthrottle, this also covers the case in which the new bandwidth is
3757 * insufficient to cover the existing bandwidth deficit. (Forcing the
3758 * timer to remain active while there are any throttled entities.)
3768 /* a cfs_rq won't donate quota below this amount */
3769 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3770 /* minimum remaining period time to redistribute slack quota */
3771 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3772 /* how long we wait to gather additional slack before distributing */
3773 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3776 * Are we near the end of the current quota period?
3778 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3779 * hrtimer base being cleared by hrtimer_start. In the case of
3780 * migrate_hrtimers, base is never cleared, so we are fine.
3782 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3784 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3787 /* if the call-back is running a quota refresh is already occurring */
3788 if (hrtimer_callback_running(refresh_timer))
3791 /* is a quota refresh about to occur? */
3792 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3793 if (remaining < min_expire)
3799 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3801 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3803 /* if there's a quota refresh soon don't bother with slack */
3804 if (runtime_refresh_within(cfs_b, min_left))
3807 hrtimer_start(&cfs_b->slack_timer,
3808 ns_to_ktime(cfs_bandwidth_slack_period),
3812 /* we know any runtime found here is valid as update_curr() precedes return */
3813 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3815 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3816 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3818 if (slack_runtime <= 0)
3821 raw_spin_lock(&cfs_b->lock);
3822 if (cfs_b->quota != RUNTIME_INF &&
3823 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3824 cfs_b->runtime += slack_runtime;
3826 /* we are under rq->lock, defer unthrottling using a timer */
3827 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3828 !list_empty(&cfs_b->throttled_cfs_rq))
3829 start_cfs_slack_bandwidth(cfs_b);
3831 raw_spin_unlock(&cfs_b->lock);
3833 /* even if it's not valid for return we don't want to try again */
3834 cfs_rq->runtime_remaining -= slack_runtime;
3837 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3839 if (!cfs_bandwidth_used())
3842 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3845 __return_cfs_rq_runtime(cfs_rq);
3849 * This is done with a timer (instead of inline with bandwidth return) since
3850 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3852 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3854 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3857 /* confirm we're still not at a refresh boundary */
3858 raw_spin_lock(&cfs_b->lock);
3859 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3860 raw_spin_unlock(&cfs_b->lock);
3864 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3865 runtime = cfs_b->runtime;
3867 expires = cfs_b->runtime_expires;
3868 raw_spin_unlock(&cfs_b->lock);
3873 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3875 raw_spin_lock(&cfs_b->lock);
3876 if (expires == cfs_b->runtime_expires)
3877 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3878 raw_spin_unlock(&cfs_b->lock);
3882 * When a group wakes up we want to make sure that its quota is not already
3883 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3884 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3886 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3888 if (!cfs_bandwidth_used())
3891 /* an active group must be handled by the update_curr()->put() path */
3892 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3895 /* ensure the group is not already throttled */
3896 if (cfs_rq_throttled(cfs_rq))
3899 /* update runtime allocation */
3900 account_cfs_rq_runtime(cfs_rq, 0);
3901 if (cfs_rq->runtime_remaining <= 0)
3902 throttle_cfs_rq(cfs_rq);
3905 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3906 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3908 if (!cfs_bandwidth_used())
3911 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3915 * it's possible for a throttled entity to be forced into a running
3916 * state (e.g. set_curr_task), in this case we're finished.
3918 if (cfs_rq_throttled(cfs_rq))
3921 throttle_cfs_rq(cfs_rq);
3925 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3927 struct cfs_bandwidth *cfs_b =
3928 container_of(timer, struct cfs_bandwidth, slack_timer);
3930 do_sched_cfs_slack_timer(cfs_b);
3932 return HRTIMER_NORESTART;
3935 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3937 struct cfs_bandwidth *cfs_b =
3938 container_of(timer, struct cfs_bandwidth, period_timer);
3942 raw_spin_lock(&cfs_b->lock);
3944 overrun = hrtimer_forward_now(timer, cfs_b->period);
3948 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3951 cfs_b->period_active = 0;
3952 raw_spin_unlock(&cfs_b->lock);
3954 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3957 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3959 raw_spin_lock_init(&cfs_b->lock);
3961 cfs_b->quota = RUNTIME_INF;
3962 cfs_b->period = ns_to_ktime(default_cfs_period());
3964 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3965 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3966 cfs_b->period_timer.function = sched_cfs_period_timer;
3967 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3968 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3971 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3973 cfs_rq->runtime_enabled = 0;
3974 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3977 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3979 lockdep_assert_held(&cfs_b->lock);
3981 if (!cfs_b->period_active) {
3982 cfs_b->period_active = 1;
3983 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
3984 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
3988 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3990 /* init_cfs_bandwidth() was not called */
3991 if (!cfs_b->throttled_cfs_rq.next)
3994 hrtimer_cancel(&cfs_b->period_timer);
3995 hrtimer_cancel(&cfs_b->slack_timer);
3998 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4000 struct cfs_rq *cfs_rq;
4002 for_each_leaf_cfs_rq(rq, cfs_rq) {
4003 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4005 raw_spin_lock(&cfs_b->lock);
4006 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4007 raw_spin_unlock(&cfs_b->lock);
4011 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4013 struct cfs_rq *cfs_rq;
4015 for_each_leaf_cfs_rq(rq, cfs_rq) {
4016 if (!cfs_rq->runtime_enabled)
4020 * clock_task is not advancing so we just need to make sure
4021 * there's some valid quota amount
4023 cfs_rq->runtime_remaining = 1;
4025 * Offline rq is schedulable till cpu is completely disabled
4026 * in take_cpu_down(), so we prevent new cfs throttling here.
4028 cfs_rq->runtime_enabled = 0;
4030 if (cfs_rq_throttled(cfs_rq))
4031 unthrottle_cfs_rq(cfs_rq);
4035 #else /* CONFIG_CFS_BANDWIDTH */
4036 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4038 return rq_clock_task(rq_of(cfs_rq));
4041 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4042 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4043 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4044 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4046 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4051 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4056 static inline int throttled_lb_pair(struct task_group *tg,
4057 int src_cpu, int dest_cpu)
4062 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4064 #ifdef CONFIG_FAIR_GROUP_SCHED
4065 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4068 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4072 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4073 static inline void update_runtime_enabled(struct rq *rq) {}
4074 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4076 #endif /* CONFIG_CFS_BANDWIDTH */
4078 /**************************************************
4079 * CFS operations on tasks:
4082 #ifdef CONFIG_SCHED_HRTICK
4083 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4085 struct sched_entity *se = &p->se;
4086 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4088 WARN_ON(task_rq(p) != rq);
4090 if (cfs_rq->nr_running > 1) {
4091 u64 slice = sched_slice(cfs_rq, se);
4092 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4093 s64 delta = slice - ran;
4100 hrtick_start(rq, delta);
4105 * called from enqueue/dequeue and updates the hrtick when the
4106 * current task is from our class and nr_running is low enough
4109 static void hrtick_update(struct rq *rq)
4111 struct task_struct *curr = rq->curr;
4113 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4116 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4117 hrtick_start_fair(rq, curr);
4119 #else /* !CONFIG_SCHED_HRTICK */
4121 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4125 static inline void hrtick_update(struct rq *rq)
4131 * The enqueue_task method is called before nr_running is
4132 * increased. Here we update the fair scheduling stats and
4133 * then put the task into the rbtree:
4136 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4138 struct cfs_rq *cfs_rq;
4139 struct sched_entity *se = &p->se;
4141 for_each_sched_entity(se) {
4144 cfs_rq = cfs_rq_of(se);
4145 enqueue_entity(cfs_rq, se, flags);
4148 * end evaluation on encountering a throttled cfs_rq
4150 * note: in the case of encountering a throttled cfs_rq we will
4151 * post the final h_nr_running increment below.
4153 if (cfs_rq_throttled(cfs_rq))
4155 cfs_rq->h_nr_running++;
4157 flags = ENQUEUE_WAKEUP;
4160 for_each_sched_entity(se) {
4161 cfs_rq = cfs_rq_of(se);
4162 cfs_rq->h_nr_running++;
4164 if (cfs_rq_throttled(cfs_rq))
4167 update_load_avg(se, 1);
4168 update_cfs_shares(cfs_rq);
4172 add_nr_running(rq, 1);
4177 static void set_next_buddy(struct sched_entity *se);
4180 * The dequeue_task method is called before nr_running is
4181 * decreased. We remove the task from the rbtree and
4182 * update the fair scheduling stats:
4184 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4186 struct cfs_rq *cfs_rq;
4187 struct sched_entity *se = &p->se;
4188 int task_sleep = flags & DEQUEUE_SLEEP;
4190 for_each_sched_entity(se) {
4191 cfs_rq = cfs_rq_of(se);
4192 dequeue_entity(cfs_rq, se, flags);
4195 * end evaluation on encountering a throttled cfs_rq
4197 * note: in the case of encountering a throttled cfs_rq we will
4198 * post the final h_nr_running decrement below.
4200 if (cfs_rq_throttled(cfs_rq))
4202 cfs_rq->h_nr_running--;
4204 /* Don't dequeue parent if it has other entities besides us */
4205 if (cfs_rq->load.weight) {
4207 * Bias pick_next to pick a task from this cfs_rq, as
4208 * p is sleeping when it is within its sched_slice.
4210 if (task_sleep && parent_entity(se))
4211 set_next_buddy(parent_entity(se));
4213 /* avoid re-evaluating load for this entity */
4214 se = parent_entity(se);
4217 flags |= DEQUEUE_SLEEP;
4220 for_each_sched_entity(se) {
4221 cfs_rq = cfs_rq_of(se);
4222 cfs_rq->h_nr_running--;
4224 if (cfs_rq_throttled(cfs_rq))
4227 update_load_avg(se, 1);
4228 update_cfs_shares(cfs_rq);
4232 sub_nr_running(rq, 1);
4240 * per rq 'load' arrray crap; XXX kill this.
4244 * The exact cpuload at various idx values, calculated at every tick would be
4245 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4247 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4248 * on nth tick when cpu may be busy, then we have:
4249 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4250 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4252 * decay_load_missed() below does efficient calculation of
4253 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4254 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4256 * The calculation is approximated on a 128 point scale.
4257 * degrade_zero_ticks is the number of ticks after which load at any
4258 * particular idx is approximated to be zero.
4259 * degrade_factor is a precomputed table, a row for each load idx.
4260 * Each column corresponds to degradation factor for a power of two ticks,
4261 * based on 128 point scale.
4263 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4264 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4266 * With this power of 2 load factors, we can degrade the load n times
4267 * by looking at 1 bits in n and doing as many mult/shift instead of
4268 * n mult/shifts needed by the exact degradation.
4270 #define DEGRADE_SHIFT 7
4271 static const unsigned char
4272 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4273 static const unsigned char
4274 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4275 {0, 0, 0, 0, 0, 0, 0, 0},
4276 {64, 32, 8, 0, 0, 0, 0, 0},
4277 {96, 72, 40, 12, 1, 0, 0},
4278 {112, 98, 75, 43, 15, 1, 0},
4279 {120, 112, 98, 76, 45, 16, 2} };
4282 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4283 * would be when CPU is idle and so we just decay the old load without
4284 * adding any new load.
4286 static unsigned long
4287 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4291 if (!missed_updates)
4294 if (missed_updates >= degrade_zero_ticks[idx])
4298 return load >> missed_updates;
4300 while (missed_updates) {
4301 if (missed_updates % 2)
4302 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4304 missed_updates >>= 1;
4311 * Update rq->cpu_load[] statistics. This function is usually called every
4312 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4313 * every tick. We fix it up based on jiffies.
4315 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4316 unsigned long pending_updates)
4320 this_rq->nr_load_updates++;
4322 /* Update our load: */
4323 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4324 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4325 unsigned long old_load, new_load;
4327 /* scale is effectively 1 << i now, and >> i divides by scale */
4329 old_load = this_rq->cpu_load[i];
4330 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4331 new_load = this_load;
4333 * Round up the averaging division if load is increasing. This
4334 * prevents us from getting stuck on 9 if the load is 10, for
4337 if (new_load > old_load)
4338 new_load += scale - 1;
4340 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4343 sched_avg_update(this_rq);
4346 /* Used instead of source_load when we know the type == 0 */
4347 static unsigned long weighted_cpuload(const int cpu)
4349 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4352 #ifdef CONFIG_NO_HZ_COMMON
4354 * There is no sane way to deal with nohz on smp when using jiffies because the
4355 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4356 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4358 * Therefore we cannot use the delta approach from the regular tick since that
4359 * would seriously skew the load calculation. However we'll make do for those
4360 * updates happening while idle (nohz_idle_balance) or coming out of idle
4361 * (tick_nohz_idle_exit).
4363 * This means we might still be one tick off for nohz periods.
4367 * Called from nohz_idle_balance() to update the load ratings before doing the
4370 static void update_idle_cpu_load(struct rq *this_rq)
4372 unsigned long curr_jiffies = READ_ONCE(jiffies);
4373 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4374 unsigned long pending_updates;
4377 * bail if there's load or we're actually up-to-date.
4379 if (load || curr_jiffies == this_rq->last_load_update_tick)
4382 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4383 this_rq->last_load_update_tick = curr_jiffies;
4385 __update_cpu_load(this_rq, load, pending_updates);
4389 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4391 void update_cpu_load_nohz(void)
4393 struct rq *this_rq = this_rq();
4394 unsigned long curr_jiffies = READ_ONCE(jiffies);
4395 unsigned long pending_updates;
4397 if (curr_jiffies == this_rq->last_load_update_tick)
4400 raw_spin_lock(&this_rq->lock);
4401 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4402 if (pending_updates) {
4403 this_rq->last_load_update_tick = curr_jiffies;
4405 * We were idle, this means load 0, the current load might be
4406 * !0 due to remote wakeups and the sort.
4408 __update_cpu_load(this_rq, 0, pending_updates);
4410 raw_spin_unlock(&this_rq->lock);
4412 #endif /* CONFIG_NO_HZ */
4415 * Called from scheduler_tick()
4417 void update_cpu_load_active(struct rq *this_rq)
4419 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4421 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4423 this_rq->last_load_update_tick = jiffies;
4424 __update_cpu_load(this_rq, load, 1);
4428 * Return a low guess at the load of a migration-source cpu weighted
4429 * according to the scheduling class and "nice" value.
4431 * We want to under-estimate the load of migration sources, to
4432 * balance conservatively.
4434 static unsigned long source_load(int cpu, int type)
4436 struct rq *rq = cpu_rq(cpu);
4437 unsigned long total = weighted_cpuload(cpu);
4439 if (type == 0 || !sched_feat(LB_BIAS))
4442 return min(rq->cpu_load[type-1], total);
4446 * Return a high guess at the load of a migration-target cpu weighted
4447 * according to the scheduling class and "nice" value.
4449 static unsigned long target_load(int cpu, int type)
4451 struct rq *rq = cpu_rq(cpu);
4452 unsigned long total = weighted_cpuload(cpu);
4454 if (type == 0 || !sched_feat(LB_BIAS))
4457 return max(rq->cpu_load[type-1], total);
4460 static unsigned long capacity_of(int cpu)
4462 return cpu_rq(cpu)->cpu_capacity;
4465 static unsigned long capacity_orig_of(int cpu)
4467 return cpu_rq(cpu)->cpu_capacity_orig;
4470 static unsigned long cpu_avg_load_per_task(int cpu)
4472 struct rq *rq = cpu_rq(cpu);
4473 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4474 unsigned long load_avg = weighted_cpuload(cpu);
4477 return load_avg / nr_running;
4482 static void record_wakee(struct task_struct *p)
4485 * Rough decay (wiping) for cost saving, don't worry
4486 * about the boundary, really active task won't care
4489 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4490 current->wakee_flips >>= 1;
4491 current->wakee_flip_decay_ts = jiffies;
4494 if (current->last_wakee != p) {
4495 current->last_wakee = p;
4496 current->wakee_flips++;
4500 static void task_waking_fair(struct task_struct *p)
4502 struct sched_entity *se = &p->se;
4503 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4506 #ifndef CONFIG_64BIT
4507 u64 min_vruntime_copy;
4510 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4512 min_vruntime = cfs_rq->min_vruntime;
4513 } while (min_vruntime != min_vruntime_copy);
4515 min_vruntime = cfs_rq->min_vruntime;
4518 se->vruntime -= min_vruntime;
4522 #ifdef CONFIG_FAIR_GROUP_SCHED
4524 * effective_load() calculates the load change as seen from the root_task_group
4526 * Adding load to a group doesn't make a group heavier, but can cause movement
4527 * of group shares between cpus. Assuming the shares were perfectly aligned one
4528 * can calculate the shift in shares.
4530 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4531 * on this @cpu and results in a total addition (subtraction) of @wg to the
4532 * total group weight.
4534 * Given a runqueue weight distribution (rw_i) we can compute a shares
4535 * distribution (s_i) using:
4537 * s_i = rw_i / \Sum rw_j (1)
4539 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4540 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4541 * shares distribution (s_i):
4543 * rw_i = { 2, 4, 1, 0 }
4544 * s_i = { 2/7, 4/7, 1/7, 0 }
4546 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4547 * task used to run on and the CPU the waker is running on), we need to
4548 * compute the effect of waking a task on either CPU and, in case of a sync
4549 * wakeup, compute the effect of the current task going to sleep.
4551 * So for a change of @wl to the local @cpu with an overall group weight change
4552 * of @wl we can compute the new shares distribution (s'_i) using:
4554 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4556 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4557 * differences in waking a task to CPU 0. The additional task changes the
4558 * weight and shares distributions like:
4560 * rw'_i = { 3, 4, 1, 0 }
4561 * s'_i = { 3/8, 4/8, 1/8, 0 }
4563 * We can then compute the difference in effective weight by using:
4565 * dw_i = S * (s'_i - s_i) (3)
4567 * Where 'S' is the group weight as seen by its parent.
4569 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4570 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4571 * 4/7) times the weight of the group.
4573 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4575 struct sched_entity *se = tg->se[cpu];
4577 if (!tg->parent) /* the trivial, non-cgroup case */
4580 for_each_sched_entity(se) {
4586 * W = @wg + \Sum rw_j
4588 W = wg + calc_tg_weight(tg, se->my_q);
4593 w = cfs_rq_load_avg(se->my_q) + wl;
4596 * wl = S * s'_i; see (2)
4599 wl = (w * (long)tg->shares) / W;
4604 * Per the above, wl is the new se->load.weight value; since
4605 * those are clipped to [MIN_SHARES, ...) do so now. See
4606 * calc_cfs_shares().
4608 if (wl < MIN_SHARES)
4612 * wl = dw_i = S * (s'_i - s_i); see (3)
4614 wl -= se->avg.load_avg;
4617 * Recursively apply this logic to all parent groups to compute
4618 * the final effective load change on the root group. Since
4619 * only the @tg group gets extra weight, all parent groups can
4620 * only redistribute existing shares. @wl is the shift in shares
4621 * resulting from this level per the above.
4630 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4638 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4639 * A waker of many should wake a different task than the one last awakened
4640 * at a frequency roughly N times higher than one of its wakees. In order
4641 * to determine whether we should let the load spread vs consolodating to
4642 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4643 * partner, and a factor of lls_size higher frequency in the other. With
4644 * both conditions met, we can be relatively sure that the relationship is
4645 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4646 * being client/server, worker/dispatcher, interrupt source or whatever is
4647 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4649 static int wake_wide(struct task_struct *p)
4651 unsigned int master = current->wakee_flips;
4652 unsigned int slave = p->wakee_flips;
4653 int factor = this_cpu_read(sd_llc_size);
4656 swap(master, slave);
4657 if (slave < factor || master < slave * factor)
4662 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4664 s64 this_load, load;
4665 s64 this_eff_load, prev_eff_load;
4666 int idx, this_cpu, prev_cpu;
4667 struct task_group *tg;
4668 unsigned long weight;
4672 this_cpu = smp_processor_id();
4673 prev_cpu = task_cpu(p);
4674 load = source_load(prev_cpu, idx);
4675 this_load = target_load(this_cpu, idx);
4678 * If sync wakeup then subtract the (maximum possible)
4679 * effect of the currently running task from the load
4680 * of the current CPU:
4683 tg = task_group(current);
4684 weight = current->se.avg.load_avg;
4686 this_load += effective_load(tg, this_cpu, -weight, -weight);
4687 load += effective_load(tg, prev_cpu, 0, -weight);
4691 weight = p->se.avg.load_avg;
4694 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4695 * due to the sync cause above having dropped this_load to 0, we'll
4696 * always have an imbalance, but there's really nothing you can do
4697 * about that, so that's good too.
4699 * Otherwise check if either cpus are near enough in load to allow this
4700 * task to be woken on this_cpu.
4702 this_eff_load = 100;
4703 this_eff_load *= capacity_of(prev_cpu);
4705 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
4706 prev_eff_load *= capacity_of(this_cpu);
4708 if (this_load > 0) {
4709 this_eff_load *= this_load +
4710 effective_load(tg, this_cpu, weight, weight);
4712 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4715 balanced = this_eff_load <= prev_eff_load;
4717 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4722 schedstat_inc(sd, ttwu_move_affine);
4723 schedstat_inc(p, se.statistics.nr_wakeups_affine);
4729 * find_idlest_group finds and returns the least busy CPU group within the
4732 static struct sched_group *
4733 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4734 int this_cpu, int sd_flag)
4736 struct sched_group *idlest = NULL, *group = sd->groups;
4737 unsigned long min_load = ULONG_MAX, this_load = 0;
4738 int load_idx = sd->forkexec_idx;
4739 int imbalance = 100 + (sd->imbalance_pct-100)/2;
4741 if (sd_flag & SD_BALANCE_WAKE)
4742 load_idx = sd->wake_idx;
4745 unsigned long load, avg_load;
4749 /* Skip over this group if it has no CPUs allowed */
4750 if (!cpumask_intersects(sched_group_cpus(group),
4751 tsk_cpus_allowed(p)))
4754 local_group = cpumask_test_cpu(this_cpu,
4755 sched_group_cpus(group));
4757 /* Tally up the load of all CPUs in the group */
4760 for_each_cpu(i, sched_group_cpus(group)) {
4761 /* Bias balancing toward cpus of our domain */
4763 load = source_load(i, load_idx);
4765 load = target_load(i, load_idx);
4770 /* Adjust by relative CPU capacity of the group */
4771 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4774 this_load = avg_load;
4775 } else if (avg_load < min_load) {
4776 min_load = avg_load;
4779 } while (group = group->next, group != sd->groups);
4781 if (!idlest || 100*this_load < imbalance*min_load)
4787 * find_idlest_cpu - find the idlest cpu among the cpus in group.
4790 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
4792 unsigned long load, min_load = ULONG_MAX;
4793 unsigned int min_exit_latency = UINT_MAX;
4794 u64 latest_idle_timestamp = 0;
4795 int least_loaded_cpu = this_cpu;
4796 int shallowest_idle_cpu = -1;
4799 /* Traverse only the allowed CPUs */
4800 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4802 struct rq *rq = cpu_rq(i);
4803 struct cpuidle_state *idle = idle_get_state(rq);
4804 if (idle && idle->exit_latency < min_exit_latency) {
4806 * We give priority to a CPU whose idle state
4807 * has the smallest exit latency irrespective
4808 * of any idle timestamp.
4810 min_exit_latency = idle->exit_latency;
4811 latest_idle_timestamp = rq->idle_stamp;
4812 shallowest_idle_cpu = i;
4813 } else if ((!idle || idle->exit_latency == min_exit_latency) &&
4814 rq->idle_stamp > latest_idle_timestamp) {
4816 * If equal or no active idle state, then
4817 * the most recently idled CPU might have
4820 latest_idle_timestamp = rq->idle_stamp;
4821 shallowest_idle_cpu = i;
4823 } else if (shallowest_idle_cpu == -1) {
4824 load = weighted_cpuload(i);
4825 if (load < min_load || (load == min_load && i == this_cpu)) {
4827 least_loaded_cpu = i;
4832 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4836 * Try and locate an idle CPU in the sched_domain.
4838 static int select_idle_sibling(struct task_struct *p, int target)
4840 struct sched_domain *sd;
4841 struct sched_group *sg;
4842 int i = task_cpu(p);
4844 if (idle_cpu(target))
4848 * If the prevous cpu is cache affine and idle, don't be stupid.
4850 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
4854 * Otherwise, iterate the domains and find an elegible idle cpu.
4856 sd = rcu_dereference(per_cpu(sd_llc, target));
4857 for_each_lower_domain(sd) {
4860 if (!cpumask_intersects(sched_group_cpus(sg),
4861 tsk_cpus_allowed(p)))
4864 for_each_cpu(i, sched_group_cpus(sg)) {
4865 if (i == target || !idle_cpu(i))
4869 target = cpumask_first_and(sched_group_cpus(sg),
4870 tsk_cpus_allowed(p));
4874 } while (sg != sd->groups);
4881 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4882 * tasks. The unit of the return value must be the one of capacity so we can
4883 * compare the utilization with the capacity of the CPU that is available for
4884 * CFS task (ie cpu_capacity).
4886 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
4887 * recent utilization of currently non-runnable tasks on a CPU. It represents
4888 * the amount of utilization of a CPU in the range [0..capacity_orig] where
4889 * capacity_orig is the cpu_capacity available at the highest frequency
4890 * (arch_scale_freq_capacity()).
4891 * The utilization of a CPU converges towards a sum equal to or less than the
4892 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
4893 * the running time on this CPU scaled by capacity_curr.
4895 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
4896 * higher than capacity_orig because of unfortunate rounding in
4897 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
4898 * the average stabilizes with the new running time. We need to check that the
4899 * utilization stays within the range of [0..capacity_orig] and cap it if
4900 * necessary. Without utilization capping, a group could be seen as overloaded
4901 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
4902 * available capacity. We allow utilization to overshoot capacity_curr (but not
4903 * capacity_orig) as it useful for predicting the capacity required after task
4904 * migrations (scheduler-driven DVFS).
4906 static int cpu_util(int cpu)
4908 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
4909 unsigned long capacity = capacity_orig_of(cpu);
4911 return (util >= capacity) ? capacity : util;
4915 * select_task_rq_fair: Select target runqueue for the waking task in domains
4916 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
4917 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
4919 * Balances load by selecting the idlest cpu in the idlest group, or under
4920 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
4922 * Returns the target cpu number.
4924 * preempt must be disabled.
4927 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4929 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4930 int cpu = smp_processor_id();
4931 int new_cpu = prev_cpu;
4932 int want_affine = 0;
4933 int sync = wake_flags & WF_SYNC;
4935 if (sd_flag & SD_BALANCE_WAKE)
4936 want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4939 for_each_domain(cpu, tmp) {
4940 if (!(tmp->flags & SD_LOAD_BALANCE))
4944 * If both cpu and prev_cpu are part of this domain,
4945 * cpu is a valid SD_WAKE_AFFINE target.
4947 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
4948 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
4953 if (tmp->flags & sd_flag)
4955 else if (!want_affine)
4960 sd = NULL; /* Prefer wake_affine over balance flags */
4961 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4966 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
4967 new_cpu = select_idle_sibling(p, new_cpu);
4970 struct sched_group *group;
4973 if (!(sd->flags & sd_flag)) {
4978 group = find_idlest_group(sd, p, cpu, sd_flag);
4984 new_cpu = find_idlest_cpu(group, p, cpu);
4985 if (new_cpu == -1 || new_cpu == cpu) {
4986 /* Now try balancing at a lower domain level of cpu */
4991 /* Now try balancing at a lower domain level of new_cpu */
4993 weight = sd->span_weight;
4995 for_each_domain(cpu, tmp) {
4996 if (weight <= tmp->span_weight)
4998 if (tmp->flags & sd_flag)
5001 /* while loop will break here if sd == NULL */
5009 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5010 * cfs_rq_of(p) references at time of call are still valid and identify the
5011 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5012 * other assumptions, including the state of rq->lock, should be made.
5014 static void migrate_task_rq_fair(struct task_struct *p)
5017 * We are supposed to update the task to "current" time, then its up to date
5018 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5019 * what current time is, so simply throw away the out-of-date time. This
5020 * will result in the wakee task is less decayed, but giving the wakee more
5021 * load sounds not bad.
5023 remove_entity_load_avg(&p->se);
5025 /* Tell new CPU we are migrated */
5026 p->se.avg.last_update_time = 0;
5028 /* We have migrated, no longer consider this task hot */
5029 p->se.exec_start = 0;
5032 static void task_dead_fair(struct task_struct *p)
5034 remove_entity_load_avg(&p->se);
5036 #endif /* CONFIG_SMP */
5038 static unsigned long
5039 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5041 unsigned long gran = sysctl_sched_wakeup_granularity;
5044 * Since its curr running now, convert the gran from real-time
5045 * to virtual-time in his units.
5047 * By using 'se' instead of 'curr' we penalize light tasks, so
5048 * they get preempted easier. That is, if 'se' < 'curr' then
5049 * the resulting gran will be larger, therefore penalizing the
5050 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5051 * be smaller, again penalizing the lighter task.
5053 * This is especially important for buddies when the leftmost
5054 * task is higher priority than the buddy.
5056 return calc_delta_fair(gran, se);
5060 * Should 'se' preempt 'curr'.
5074 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5076 s64 gran, vdiff = curr->vruntime - se->vruntime;
5081 gran = wakeup_gran(curr, se);
5088 static void set_last_buddy(struct sched_entity *se)
5090 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5093 for_each_sched_entity(se)
5094 cfs_rq_of(se)->last = se;
5097 static void set_next_buddy(struct sched_entity *se)
5099 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5102 for_each_sched_entity(se)
5103 cfs_rq_of(se)->next = se;
5106 static void set_skip_buddy(struct sched_entity *se)
5108 for_each_sched_entity(se)
5109 cfs_rq_of(se)->skip = se;
5113 * Preempt the current task with a newly woken task if needed:
5115 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5117 struct task_struct *curr = rq->curr;
5118 struct sched_entity *se = &curr->se, *pse = &p->se;
5119 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5120 int scale = cfs_rq->nr_running >= sched_nr_latency;
5121 int next_buddy_marked = 0;
5123 if (unlikely(se == pse))
5127 * This is possible from callers such as attach_tasks(), in which we
5128 * unconditionally check_prempt_curr() after an enqueue (which may have
5129 * lead to a throttle). This both saves work and prevents false
5130 * next-buddy nomination below.
5132 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5135 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5136 set_next_buddy(pse);
5137 next_buddy_marked = 1;
5141 * We can come here with TIF_NEED_RESCHED already set from new task
5144 * Note: this also catches the edge-case of curr being in a throttled
5145 * group (e.g. via set_curr_task), since update_curr() (in the
5146 * enqueue of curr) will have resulted in resched being set. This
5147 * prevents us from potentially nominating it as a false LAST_BUDDY
5150 if (test_tsk_need_resched(curr))
5153 /* Idle tasks are by definition preempted by non-idle tasks. */
5154 if (unlikely(curr->policy == SCHED_IDLE) &&
5155 likely(p->policy != SCHED_IDLE))
5159 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5160 * is driven by the tick):
5162 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5165 find_matching_se(&se, &pse);
5166 update_curr(cfs_rq_of(se));
5168 if (wakeup_preempt_entity(se, pse) == 1) {
5170 * Bias pick_next to pick the sched entity that is
5171 * triggering this preemption.
5173 if (!next_buddy_marked)
5174 set_next_buddy(pse);
5183 * Only set the backward buddy when the current task is still
5184 * on the rq. This can happen when a wakeup gets interleaved
5185 * with schedule on the ->pre_schedule() or idle_balance()
5186 * point, either of which can * drop the rq lock.
5188 * Also, during early boot the idle thread is in the fair class,
5189 * for obvious reasons its a bad idea to schedule back to it.
5191 if (unlikely(!se->on_rq || curr == rq->idle))
5194 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5198 static struct task_struct *
5199 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5201 struct cfs_rq *cfs_rq = &rq->cfs;
5202 struct sched_entity *se;
5203 struct task_struct *p;
5207 #ifdef CONFIG_FAIR_GROUP_SCHED
5208 if (!cfs_rq->nr_running)
5211 if (prev->sched_class != &fair_sched_class)
5215 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5216 * likely that a next task is from the same cgroup as the current.
5218 * Therefore attempt to avoid putting and setting the entire cgroup
5219 * hierarchy, only change the part that actually changes.
5223 struct sched_entity *curr = cfs_rq->curr;
5226 * Since we got here without doing put_prev_entity() we also
5227 * have to consider cfs_rq->curr. If it is still a runnable
5228 * entity, update_curr() will update its vruntime, otherwise
5229 * forget we've ever seen it.
5233 update_curr(cfs_rq);
5238 * This call to check_cfs_rq_runtime() will do the
5239 * throttle and dequeue its entity in the parent(s).
5240 * Therefore the 'simple' nr_running test will indeed
5243 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5247 se = pick_next_entity(cfs_rq, curr);
5248 cfs_rq = group_cfs_rq(se);
5254 * Since we haven't yet done put_prev_entity and if the selected task
5255 * is a different task than we started out with, try and touch the
5256 * least amount of cfs_rqs.
5259 struct sched_entity *pse = &prev->se;
5261 while (!(cfs_rq = is_same_group(se, pse))) {
5262 int se_depth = se->depth;
5263 int pse_depth = pse->depth;
5265 if (se_depth <= pse_depth) {
5266 put_prev_entity(cfs_rq_of(pse), pse);
5267 pse = parent_entity(pse);
5269 if (se_depth >= pse_depth) {
5270 set_next_entity(cfs_rq_of(se), se);
5271 se = parent_entity(se);
5275 put_prev_entity(cfs_rq, pse);
5276 set_next_entity(cfs_rq, se);
5279 if (hrtick_enabled(rq))
5280 hrtick_start_fair(rq, p);
5287 if (!cfs_rq->nr_running)
5290 put_prev_task(rq, prev);
5293 se = pick_next_entity(cfs_rq, NULL);
5294 set_next_entity(cfs_rq, se);
5295 cfs_rq = group_cfs_rq(se);
5300 if (hrtick_enabled(rq))
5301 hrtick_start_fair(rq, p);
5307 * This is OK, because current is on_cpu, which avoids it being picked
5308 * for load-balance and preemption/IRQs are still disabled avoiding
5309 * further scheduler activity on it and we're being very careful to
5310 * re-start the picking loop.
5312 lockdep_unpin_lock(&rq->lock);
5313 new_tasks = idle_balance(rq);
5314 lockdep_pin_lock(&rq->lock);
5316 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5317 * possible for any higher priority task to appear. In that case we
5318 * must re-start the pick_next_entity() loop.
5330 * Account for a descheduled task:
5332 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5334 struct sched_entity *se = &prev->se;
5335 struct cfs_rq *cfs_rq;
5337 for_each_sched_entity(se) {
5338 cfs_rq = cfs_rq_of(se);
5339 put_prev_entity(cfs_rq, se);
5344 * sched_yield() is very simple
5346 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5348 static void yield_task_fair(struct rq *rq)
5350 struct task_struct *curr = rq->curr;
5351 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5352 struct sched_entity *se = &curr->se;
5355 * Are we the only task in the tree?
5357 if (unlikely(rq->nr_running == 1))
5360 clear_buddies(cfs_rq, se);
5362 if (curr->policy != SCHED_BATCH) {
5363 update_rq_clock(rq);
5365 * Update run-time statistics of the 'current'.
5367 update_curr(cfs_rq);
5369 * Tell update_rq_clock() that we've just updated,
5370 * so we don't do microscopic update in schedule()
5371 * and double the fastpath cost.
5373 rq_clock_skip_update(rq, true);
5379 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
5381 struct sched_entity *se = &p->se;
5383 /* throttled hierarchies are not runnable */
5384 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5387 /* Tell the scheduler that we'd really like pse to run next. */
5390 yield_task_fair(rq);
5396 /**************************************************
5397 * Fair scheduling class load-balancing methods.
5401 * The purpose of load-balancing is to achieve the same basic fairness the
5402 * per-cpu scheduler provides, namely provide a proportional amount of compute
5403 * time to each task. This is expressed in the following equation:
5405 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5407 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5408 * W_i,0 is defined as:
5410 * W_i,0 = \Sum_j w_i,j (2)
5412 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5413 * is derived from the nice value as per prio_to_weight[].
5415 * The weight average is an exponential decay average of the instantaneous
5418 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5420 * C_i is the compute capacity of cpu i, typically it is the
5421 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5422 * can also include other factors [XXX].
5424 * To achieve this balance we define a measure of imbalance which follows
5425 * directly from (1):
5427 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5429 * We them move tasks around to minimize the imbalance. In the continuous
5430 * function space it is obvious this converges, in the discrete case we get
5431 * a few fun cases generally called infeasible weight scenarios.
5434 * - infeasible weights;
5435 * - local vs global optima in the discrete case. ]
5440 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5441 * for all i,j solution, we create a tree of cpus that follows the hardware
5442 * topology where each level pairs two lower groups (or better). This results
5443 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5444 * tree to only the first of the previous level and we decrease the frequency
5445 * of load-balance at each level inv. proportional to the number of cpus in
5451 * \Sum { --- * --- * 2^i } = O(n) (5)
5453 * `- size of each group
5454 * | | `- number of cpus doing load-balance
5456 * `- sum over all levels
5458 * Coupled with a limit on how many tasks we can migrate every balance pass,
5459 * this makes (5) the runtime complexity of the balancer.
5461 * An important property here is that each CPU is still (indirectly) connected
5462 * to every other cpu in at most O(log n) steps:
5464 * The adjacency matrix of the resulting graph is given by:
5467 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5470 * And you'll find that:
5472 * A^(log_2 n)_i,j != 0 for all i,j (7)
5474 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5475 * The task movement gives a factor of O(m), giving a convergence complexity
5478 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5483 * In order to avoid CPUs going idle while there's still work to do, new idle
5484 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5485 * tree itself instead of relying on other CPUs to bring it work.
5487 * This adds some complexity to both (5) and (8) but it reduces the total idle
5495 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5498 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5503 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5505 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5507 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5510 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5511 * rewrite all of this once again.]
5514 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
5516 enum fbq_type { regular, remote, all };
5518 #define LBF_ALL_PINNED 0x01
5519 #define LBF_NEED_BREAK 0x02
5520 #define LBF_DST_PINNED 0x04
5521 #define LBF_SOME_PINNED 0x08
5524 struct sched_domain *sd;
5532 struct cpumask *dst_grpmask;
5534 enum cpu_idle_type idle;
5536 /* The set of CPUs under consideration for load-balancing */
5537 struct cpumask *cpus;
5542 unsigned int loop_break;
5543 unsigned int loop_max;
5545 enum fbq_type fbq_type;
5546 struct list_head tasks;
5550 * Is this task likely cache-hot:
5552 static int task_hot(struct task_struct *p, struct lb_env *env)
5556 lockdep_assert_held(&env->src_rq->lock);
5558 if (p->sched_class != &fair_sched_class)
5561 if (unlikely(p->policy == SCHED_IDLE))
5565 * Buddy candidates are cache hot:
5567 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5568 (&p->se == cfs_rq_of(&p->se)->next ||
5569 &p->se == cfs_rq_of(&p->se)->last))
5572 if (sysctl_sched_migration_cost == -1)
5574 if (sysctl_sched_migration_cost == 0)
5577 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5579 return delta < (s64)sysctl_sched_migration_cost;
5582 #ifdef CONFIG_NUMA_BALANCING
5584 * Returns 1, if task migration degrades locality
5585 * Returns 0, if task migration improves locality i.e migration preferred.
5586 * Returns -1, if task migration is not affected by locality.
5588 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5590 struct numa_group *numa_group = rcu_dereference(p->numa_group);
5591 unsigned long src_faults, dst_faults;
5592 int src_nid, dst_nid;
5594 if (!static_branch_likely(&sched_numa_balancing))
5597 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5600 src_nid = cpu_to_node(env->src_cpu);
5601 dst_nid = cpu_to_node(env->dst_cpu);
5603 if (src_nid == dst_nid)
5606 /* Migrating away from the preferred node is always bad. */
5607 if (src_nid == p->numa_preferred_nid) {
5608 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
5614 /* Encourage migration to the preferred node. */
5615 if (dst_nid == p->numa_preferred_nid)
5619 src_faults = group_faults(p, src_nid);
5620 dst_faults = group_faults(p, dst_nid);
5622 src_faults = task_faults(p, src_nid);
5623 dst_faults = task_faults(p, dst_nid);
5626 return dst_faults < src_faults;
5630 static inline int migrate_degrades_locality(struct task_struct *p,
5638 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5641 int can_migrate_task(struct task_struct *p, struct lb_env *env)
5645 lockdep_assert_held(&env->src_rq->lock);
5648 * We do not migrate tasks that are:
5649 * 1) throttled_lb_pair, or
5650 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5651 * 3) running (obviously), or
5652 * 4) are cache-hot on their current CPU.
5654 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
5657 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5660 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5662 env->flags |= LBF_SOME_PINNED;
5665 * Remember if this task can be migrated to any other cpu in
5666 * our sched_group. We may want to revisit it if we couldn't
5667 * meet load balance goals by pulling other tasks on src_cpu.
5669 * Also avoid computing new_dst_cpu if we have already computed
5670 * one in current iteration.
5672 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5675 /* Prevent to re-select dst_cpu via env's cpus */
5676 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
5677 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5678 env->flags |= LBF_DST_PINNED;
5679 env->new_dst_cpu = cpu;
5687 /* Record that we found atleast one task that could run on dst_cpu */
5688 env->flags &= ~LBF_ALL_PINNED;
5690 if (task_running(env->src_rq, p)) {
5691 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5696 * Aggressive migration if:
5697 * 1) destination numa is preferred
5698 * 2) task is cache cold, or
5699 * 3) too many balance attempts have failed.
5701 tsk_cache_hot = migrate_degrades_locality(p, env);
5702 if (tsk_cache_hot == -1)
5703 tsk_cache_hot = task_hot(p, env);
5705 if (tsk_cache_hot <= 0 ||
5706 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5707 if (tsk_cache_hot == 1) {
5708 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5709 schedstat_inc(p, se.statistics.nr_forced_migrations);
5714 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
5719 * detach_task() -- detach the task for the migration specified in env
5721 static void detach_task(struct task_struct *p, struct lb_env *env)
5723 lockdep_assert_held(&env->src_rq->lock);
5725 deactivate_task(env->src_rq, p, 0);
5726 p->on_rq = TASK_ON_RQ_MIGRATING;
5727 set_task_cpu(p, env->dst_cpu);
5731 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5732 * part of active balancing operations within "domain".
5734 * Returns a task if successful and NULL otherwise.
5736 static struct task_struct *detach_one_task(struct lb_env *env)
5738 struct task_struct *p, *n;
5740 lockdep_assert_held(&env->src_rq->lock);
5742 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
5743 if (!can_migrate_task(p, env))
5746 detach_task(p, env);
5749 * Right now, this is only the second place where
5750 * lb_gained[env->idle] is updated (other is detach_tasks)
5751 * so we can safely collect stats here rather than
5752 * inside detach_tasks().
5754 schedstat_inc(env->sd, lb_gained[env->idle]);
5760 static const unsigned int sched_nr_migrate_break = 32;
5763 * detach_tasks() -- tries to detach up to imbalance weighted load from
5764 * busiest_rq, as part of a balancing operation within domain "sd".
5766 * Returns number of detached tasks if successful and 0 otherwise.
5768 static int detach_tasks(struct lb_env *env)
5770 struct list_head *tasks = &env->src_rq->cfs_tasks;
5771 struct task_struct *p;
5775 lockdep_assert_held(&env->src_rq->lock);
5777 if (env->imbalance <= 0)
5780 while (!list_empty(tasks)) {
5782 * We don't want to steal all, otherwise we may be treated likewise,
5783 * which could at worst lead to a livelock crash.
5785 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
5788 p = list_first_entry(tasks, struct task_struct, se.group_node);
5791 /* We've more or less seen every task there is, call it quits */
5792 if (env->loop > env->loop_max)
5795 /* take a breather every nr_migrate tasks */
5796 if (env->loop > env->loop_break) {
5797 env->loop_break += sched_nr_migrate_break;
5798 env->flags |= LBF_NEED_BREAK;
5802 if (!can_migrate_task(p, env))
5805 load = task_h_load(p);
5807 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5810 if ((load / 2) > env->imbalance)
5813 detach_task(p, env);
5814 list_add(&p->se.group_node, &env->tasks);
5817 env->imbalance -= load;
5819 #ifdef CONFIG_PREEMPT
5821 * NEWIDLE balancing is a source of latency, so preemptible
5822 * kernels will stop after the first task is detached to minimize
5823 * the critical section.
5825 if (env->idle == CPU_NEWLY_IDLE)
5830 * We only want to steal up to the prescribed amount of
5833 if (env->imbalance <= 0)
5838 list_move_tail(&p->se.group_node, tasks);
5842 * Right now, this is one of only two places we collect this stat
5843 * so we can safely collect detach_one_task() stats here rather
5844 * than inside detach_one_task().
5846 schedstat_add(env->sd, lb_gained[env->idle], detached);
5852 * attach_task() -- attach the task detached by detach_task() to its new rq.
5854 static void attach_task(struct rq *rq, struct task_struct *p)
5856 lockdep_assert_held(&rq->lock);
5858 BUG_ON(task_rq(p) != rq);
5859 p->on_rq = TASK_ON_RQ_QUEUED;
5860 activate_task(rq, p, 0);
5861 check_preempt_curr(rq, p, 0);
5865 * attach_one_task() -- attaches the task returned from detach_one_task() to
5868 static void attach_one_task(struct rq *rq, struct task_struct *p)
5870 raw_spin_lock(&rq->lock);
5872 raw_spin_unlock(&rq->lock);
5876 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
5879 static void attach_tasks(struct lb_env *env)
5881 struct list_head *tasks = &env->tasks;
5882 struct task_struct *p;
5884 raw_spin_lock(&env->dst_rq->lock);
5886 while (!list_empty(tasks)) {
5887 p = list_first_entry(tasks, struct task_struct, se.group_node);
5888 list_del_init(&p->se.group_node);
5890 attach_task(env->dst_rq, p);
5893 raw_spin_unlock(&env->dst_rq->lock);
5896 #ifdef CONFIG_FAIR_GROUP_SCHED
5897 static void update_blocked_averages(int cpu)
5899 struct rq *rq = cpu_rq(cpu);
5900 struct cfs_rq *cfs_rq;
5901 unsigned long flags;
5903 raw_spin_lock_irqsave(&rq->lock, flags);
5904 update_rq_clock(rq);
5907 * Iterates the task_group tree in a bottom up fashion, see
5908 * list_add_leaf_cfs_rq() for details.
5910 for_each_leaf_cfs_rq(rq, cfs_rq) {
5911 /* throttled entities do not contribute to load */
5912 if (throttled_hierarchy(cfs_rq))
5915 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
5916 update_tg_load_avg(cfs_rq, 0);
5918 raw_spin_unlock_irqrestore(&rq->lock, flags);
5922 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5923 * This needs to be done in a top-down fashion because the load of a child
5924 * group is a fraction of its parents load.
5926 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5928 struct rq *rq = rq_of(cfs_rq);
5929 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5930 unsigned long now = jiffies;
5933 if (cfs_rq->last_h_load_update == now)
5936 cfs_rq->h_load_next = NULL;
5937 for_each_sched_entity(se) {
5938 cfs_rq = cfs_rq_of(se);
5939 cfs_rq->h_load_next = se;
5940 if (cfs_rq->last_h_load_update == now)
5945 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5946 cfs_rq->last_h_load_update = now;
5949 while ((se = cfs_rq->h_load_next) != NULL) {
5950 load = cfs_rq->h_load;
5951 load = div64_ul(load * se->avg.load_avg,
5952 cfs_rq_load_avg(cfs_rq) + 1);
5953 cfs_rq = group_cfs_rq(se);
5954 cfs_rq->h_load = load;
5955 cfs_rq->last_h_load_update = now;
5959 static unsigned long task_h_load(struct task_struct *p)
5961 struct cfs_rq *cfs_rq = task_cfs_rq(p);
5963 update_cfs_rq_h_load(cfs_rq);
5964 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
5965 cfs_rq_load_avg(cfs_rq) + 1);
5968 static inline void update_blocked_averages(int cpu)
5970 struct rq *rq = cpu_rq(cpu);
5971 struct cfs_rq *cfs_rq = &rq->cfs;
5972 unsigned long flags;
5974 raw_spin_lock_irqsave(&rq->lock, flags);
5975 update_rq_clock(rq);
5976 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
5977 raw_spin_unlock_irqrestore(&rq->lock, flags);
5980 static unsigned long task_h_load(struct task_struct *p)
5982 return p->se.avg.load_avg;
5986 /********** Helpers for find_busiest_group ************************/
5995 * sg_lb_stats - stats of a sched_group required for load_balancing
5997 struct sg_lb_stats {
5998 unsigned long avg_load; /*Avg load across the CPUs of the group */
5999 unsigned long group_load; /* Total load over the CPUs of the group */
6000 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6001 unsigned long load_per_task;
6002 unsigned long group_capacity;
6003 unsigned long group_util; /* Total utilization of the group */
6004 unsigned int sum_nr_running; /* Nr tasks running in the group */
6005 unsigned int idle_cpus;
6006 unsigned int group_weight;
6007 enum group_type group_type;
6008 int group_no_capacity;
6009 #ifdef CONFIG_NUMA_BALANCING
6010 unsigned int nr_numa_running;
6011 unsigned int nr_preferred_running;
6016 * sd_lb_stats - Structure to store the statistics of a sched_domain
6017 * during load balancing.
6019 struct sd_lb_stats {
6020 struct sched_group *busiest; /* Busiest group in this sd */
6021 struct sched_group *local; /* Local group in this sd */
6022 unsigned long total_load; /* Total load of all groups in sd */
6023 unsigned long total_capacity; /* Total capacity of all groups in sd */
6024 unsigned long avg_load; /* Average load across all groups in sd */
6026 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6027 struct sg_lb_stats local_stat; /* Statistics of the local group */
6030 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6033 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6034 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6035 * We must however clear busiest_stat::avg_load because
6036 * update_sd_pick_busiest() reads this before assignment.
6038 *sds = (struct sd_lb_stats){
6042 .total_capacity = 0UL,
6045 .sum_nr_running = 0,
6046 .group_type = group_other,
6052 * get_sd_load_idx - Obtain the load index for a given sched domain.
6053 * @sd: The sched_domain whose load_idx is to be obtained.
6054 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6056 * Return: The load index.
6058 static inline int get_sd_load_idx(struct sched_domain *sd,
6059 enum cpu_idle_type idle)
6065 load_idx = sd->busy_idx;
6068 case CPU_NEWLY_IDLE:
6069 load_idx = sd->newidle_idx;
6072 load_idx = sd->idle_idx;
6079 static unsigned long scale_rt_capacity(int cpu)
6081 struct rq *rq = cpu_rq(cpu);
6082 u64 total, used, age_stamp, avg;
6086 * Since we're reading these variables without serialization make sure
6087 * we read them once before doing sanity checks on them.
6089 age_stamp = READ_ONCE(rq->age_stamp);
6090 avg = READ_ONCE(rq->rt_avg);
6091 delta = __rq_clock_broken(rq) - age_stamp;
6093 if (unlikely(delta < 0))
6096 total = sched_avg_period() + delta;
6098 used = div_u64(avg, total);
6100 if (likely(used < SCHED_CAPACITY_SCALE))
6101 return SCHED_CAPACITY_SCALE - used;
6106 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6108 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6109 struct sched_group *sdg = sd->groups;
6111 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6113 capacity *= scale_rt_capacity(cpu);
6114 capacity >>= SCHED_CAPACITY_SHIFT;
6119 cpu_rq(cpu)->cpu_capacity = capacity;
6120 sdg->sgc->capacity = capacity;
6123 void update_group_capacity(struct sched_domain *sd, int cpu)
6125 struct sched_domain *child = sd->child;
6126 struct sched_group *group, *sdg = sd->groups;
6127 unsigned long capacity;
6128 unsigned long interval;
6130 interval = msecs_to_jiffies(sd->balance_interval);
6131 interval = clamp(interval, 1UL, max_load_balance_interval);
6132 sdg->sgc->next_update = jiffies + interval;
6135 update_cpu_capacity(sd, cpu);
6141 if (child->flags & SD_OVERLAP) {
6143 * SD_OVERLAP domains cannot assume that child groups
6144 * span the current group.
6147 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6148 struct sched_group_capacity *sgc;
6149 struct rq *rq = cpu_rq(cpu);
6152 * build_sched_domains() -> init_sched_groups_capacity()
6153 * gets here before we've attached the domains to the
6156 * Use capacity_of(), which is set irrespective of domains
6157 * in update_cpu_capacity().
6159 * This avoids capacity from being 0 and
6160 * causing divide-by-zero issues on boot.
6162 if (unlikely(!rq->sd)) {
6163 capacity += capacity_of(cpu);
6167 sgc = rq->sd->groups->sgc;
6168 capacity += sgc->capacity;
6172 * !SD_OVERLAP domains can assume that child groups
6173 * span the current group.
6176 group = child->groups;
6178 capacity += group->sgc->capacity;
6179 group = group->next;
6180 } while (group != child->groups);
6183 sdg->sgc->capacity = capacity;
6187 * Check whether the capacity of the rq has been noticeably reduced by side
6188 * activity. The imbalance_pct is used for the threshold.
6189 * Return true is the capacity is reduced
6192 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6194 return ((rq->cpu_capacity * sd->imbalance_pct) <
6195 (rq->cpu_capacity_orig * 100));
6199 * Group imbalance indicates (and tries to solve) the problem where balancing
6200 * groups is inadequate due to tsk_cpus_allowed() constraints.
6202 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6203 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6206 * { 0 1 2 3 } { 4 5 6 7 }
6209 * If we were to balance group-wise we'd place two tasks in the first group and
6210 * two tasks in the second group. Clearly this is undesired as it will overload
6211 * cpu 3 and leave one of the cpus in the second group unused.
6213 * The current solution to this issue is detecting the skew in the first group
6214 * by noticing the lower domain failed to reach balance and had difficulty
6215 * moving tasks due to affinity constraints.
6217 * When this is so detected; this group becomes a candidate for busiest; see
6218 * update_sd_pick_busiest(). And calculate_imbalance() and
6219 * find_busiest_group() avoid some of the usual balance conditions to allow it
6220 * to create an effective group imbalance.
6222 * This is a somewhat tricky proposition since the next run might not find the
6223 * group imbalance and decide the groups need to be balanced again. A most
6224 * subtle and fragile situation.
6227 static inline int sg_imbalanced(struct sched_group *group)
6229 return group->sgc->imbalance;
6233 * group_has_capacity returns true if the group has spare capacity that could
6234 * be used by some tasks.
6235 * We consider that a group has spare capacity if the * number of task is
6236 * smaller than the number of CPUs or if the utilization is lower than the
6237 * available capacity for CFS tasks.
6238 * For the latter, we use a threshold to stabilize the state, to take into
6239 * account the variance of the tasks' load and to return true if the available
6240 * capacity in meaningful for the load balancer.
6241 * As an example, an available capacity of 1% can appear but it doesn't make
6242 * any benefit for the load balance.
6245 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6247 if (sgs->sum_nr_running < sgs->group_weight)
6250 if ((sgs->group_capacity * 100) >
6251 (sgs->group_util * env->sd->imbalance_pct))
6258 * group_is_overloaded returns true if the group has more tasks than it can
6260 * group_is_overloaded is not equals to !group_has_capacity because a group
6261 * with the exact right number of tasks, has no more spare capacity but is not
6262 * overloaded so both group_has_capacity and group_is_overloaded return
6266 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6268 if (sgs->sum_nr_running <= sgs->group_weight)
6271 if ((sgs->group_capacity * 100) <
6272 (sgs->group_util * env->sd->imbalance_pct))
6279 group_type group_classify(struct sched_group *group,
6280 struct sg_lb_stats *sgs)
6282 if (sgs->group_no_capacity)
6283 return group_overloaded;
6285 if (sg_imbalanced(group))
6286 return group_imbalanced;
6292 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6293 * @env: The load balancing environment.
6294 * @group: sched_group whose statistics are to be updated.
6295 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6296 * @local_group: Does group contain this_cpu.
6297 * @sgs: variable to hold the statistics for this group.
6298 * @overload: Indicate more than one runnable task for any CPU.
6300 static inline void update_sg_lb_stats(struct lb_env *env,
6301 struct sched_group *group, int load_idx,
6302 int local_group, struct sg_lb_stats *sgs,
6308 memset(sgs, 0, sizeof(*sgs));
6310 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6311 struct rq *rq = cpu_rq(i);
6313 /* Bias balancing toward cpus of our domain */
6315 load = target_load(i, load_idx);
6317 load = source_load(i, load_idx);
6319 sgs->group_load += load;
6320 sgs->group_util += cpu_util(i);
6321 sgs->sum_nr_running += rq->cfs.h_nr_running;
6323 if (rq->nr_running > 1)
6326 #ifdef CONFIG_NUMA_BALANCING
6327 sgs->nr_numa_running += rq->nr_numa_running;
6328 sgs->nr_preferred_running += rq->nr_preferred_running;
6330 sgs->sum_weighted_load += weighted_cpuload(i);
6335 /* Adjust by relative CPU capacity of the group */
6336 sgs->group_capacity = group->sgc->capacity;
6337 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6339 if (sgs->sum_nr_running)
6340 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6342 sgs->group_weight = group->group_weight;
6344 sgs->group_no_capacity = group_is_overloaded(env, sgs);
6345 sgs->group_type = group_classify(group, sgs);
6349 * update_sd_pick_busiest - return 1 on busiest group
6350 * @env: The load balancing environment.
6351 * @sds: sched_domain statistics
6352 * @sg: sched_group candidate to be checked for being the busiest
6353 * @sgs: sched_group statistics
6355 * Determine if @sg is a busier group than the previously selected
6358 * Return: %true if @sg is a busier group than the previously selected
6359 * busiest group. %false otherwise.
6361 static bool update_sd_pick_busiest(struct lb_env *env,
6362 struct sd_lb_stats *sds,
6363 struct sched_group *sg,
6364 struct sg_lb_stats *sgs)
6366 struct sg_lb_stats *busiest = &sds->busiest_stat;
6368 if (sgs->group_type > busiest->group_type)
6371 if (sgs->group_type < busiest->group_type)
6374 if (sgs->avg_load <= busiest->avg_load)
6377 /* This is the busiest node in its class. */
6378 if (!(env->sd->flags & SD_ASYM_PACKING))
6382 * ASYM_PACKING needs to move all the work to the lowest
6383 * numbered CPUs in the group, therefore mark all groups
6384 * higher than ourself as busy.
6386 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6390 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
6397 #ifdef CONFIG_NUMA_BALANCING
6398 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6400 if (sgs->sum_nr_running > sgs->nr_numa_running)
6402 if (sgs->sum_nr_running > sgs->nr_preferred_running)
6407 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6409 if (rq->nr_running > rq->nr_numa_running)
6411 if (rq->nr_running > rq->nr_preferred_running)
6416 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
6421 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
6425 #endif /* CONFIG_NUMA_BALANCING */
6428 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6429 * @env: The load balancing environment.
6430 * @sds: variable to hold the statistics for this sched_domain.
6432 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6434 struct sched_domain *child = env->sd->child;
6435 struct sched_group *sg = env->sd->groups;
6436 struct sg_lb_stats tmp_sgs;
6437 int load_idx, prefer_sibling = 0;
6438 bool overload = false;
6440 if (child && child->flags & SD_PREFER_SIBLING)
6443 load_idx = get_sd_load_idx(env->sd, env->idle);
6446 struct sg_lb_stats *sgs = &tmp_sgs;
6449 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
6452 sgs = &sds->local_stat;
6454 if (env->idle != CPU_NEWLY_IDLE ||
6455 time_after_eq(jiffies, sg->sgc->next_update))
6456 update_group_capacity(env->sd, env->dst_cpu);
6459 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
6466 * In case the child domain prefers tasks go to siblings
6467 * first, lower the sg capacity so that we'll try
6468 * and move all the excess tasks away. We lower the capacity
6469 * of a group only if the local group has the capacity to fit
6470 * these excess tasks. The extra check prevents the case where
6471 * you always pull from the heaviest group when it is already
6472 * under-utilized (possible with a large weight task outweighs
6473 * the tasks on the system).
6475 if (prefer_sibling && sds->local &&
6476 group_has_capacity(env, &sds->local_stat) &&
6477 (sgs->sum_nr_running > 1)) {
6478 sgs->group_no_capacity = 1;
6479 sgs->group_type = group_classify(sg, sgs);
6482 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6484 sds->busiest_stat = *sgs;
6488 /* Now, start updating sd_lb_stats */
6489 sds->total_load += sgs->group_load;
6490 sds->total_capacity += sgs->group_capacity;
6493 } while (sg != env->sd->groups);
6495 if (env->sd->flags & SD_NUMA)
6496 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6498 if (!env->sd->parent) {
6499 /* update overload indicator if we are at root domain */
6500 if (env->dst_rq->rd->overload != overload)
6501 env->dst_rq->rd->overload = overload;
6507 * check_asym_packing - Check to see if the group is packed into the
6510 * This is primarily intended to used at the sibling level. Some
6511 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6512 * case of POWER7, it can move to lower SMT modes only when higher
6513 * threads are idle. When in lower SMT modes, the threads will
6514 * perform better since they share less core resources. Hence when we
6515 * have idle threads, we want them to be the higher ones.
6517 * This packing function is run on idle threads. It checks to see if
6518 * the busiest CPU in this domain (core in the P7 case) has a higher
6519 * CPU number than the packing function is being run on. Here we are
6520 * assuming lower CPU number will be equivalent to lower a SMT thread
6523 * Return: 1 when packing is required and a task should be moved to
6524 * this CPU. The amount of the imbalance is returned in *imbalance.
6526 * @env: The load balancing environment.
6527 * @sds: Statistics of the sched_domain which is to be packed
6529 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6533 if (!(env->sd->flags & SD_ASYM_PACKING))
6539 busiest_cpu = group_first_cpu(sds->busiest);
6540 if (env->dst_cpu > busiest_cpu)
6543 env->imbalance = DIV_ROUND_CLOSEST(
6544 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6545 SCHED_CAPACITY_SCALE);
6551 * fix_small_imbalance - Calculate the minor imbalance that exists
6552 * amongst the groups of a sched_domain, during
6554 * @env: The load balancing environment.
6555 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6558 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6560 unsigned long tmp, capa_now = 0, capa_move = 0;
6561 unsigned int imbn = 2;
6562 unsigned long scaled_busy_load_per_task;
6563 struct sg_lb_stats *local, *busiest;
6565 local = &sds->local_stat;
6566 busiest = &sds->busiest_stat;
6568 if (!local->sum_nr_running)
6569 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
6570 else if (busiest->load_per_task > local->load_per_task)
6573 scaled_busy_load_per_task =
6574 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6575 busiest->group_capacity;
6577 if (busiest->avg_load + scaled_busy_load_per_task >=
6578 local->avg_load + (scaled_busy_load_per_task * imbn)) {
6579 env->imbalance = busiest->load_per_task;
6584 * OK, we don't have enough imbalance to justify moving tasks,
6585 * however we may be able to increase total CPU capacity used by
6589 capa_now += busiest->group_capacity *
6590 min(busiest->load_per_task, busiest->avg_load);
6591 capa_now += local->group_capacity *
6592 min(local->load_per_task, local->avg_load);
6593 capa_now /= SCHED_CAPACITY_SCALE;
6595 /* Amount of load we'd subtract */
6596 if (busiest->avg_load > scaled_busy_load_per_task) {
6597 capa_move += busiest->group_capacity *
6598 min(busiest->load_per_task,
6599 busiest->avg_load - scaled_busy_load_per_task);
6602 /* Amount of load we'd add */
6603 if (busiest->avg_load * busiest->group_capacity <
6604 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6605 tmp = (busiest->avg_load * busiest->group_capacity) /
6606 local->group_capacity;
6608 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6609 local->group_capacity;
6611 capa_move += local->group_capacity *
6612 min(local->load_per_task, local->avg_load + tmp);
6613 capa_move /= SCHED_CAPACITY_SCALE;
6615 /* Move if we gain throughput */
6616 if (capa_move > capa_now)
6617 env->imbalance = busiest->load_per_task;
6621 * calculate_imbalance - Calculate the amount of imbalance present within the
6622 * groups of a given sched_domain during load balance.
6623 * @env: load balance environment
6624 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6626 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6628 unsigned long max_pull, load_above_capacity = ~0UL;
6629 struct sg_lb_stats *local, *busiest;
6631 local = &sds->local_stat;
6632 busiest = &sds->busiest_stat;
6634 if (busiest->group_type == group_imbalanced) {
6636 * In the group_imb case we cannot rely on group-wide averages
6637 * to ensure cpu-load equilibrium, look at wider averages. XXX
6639 busiest->load_per_task =
6640 min(busiest->load_per_task, sds->avg_load);
6644 * In the presence of smp nice balancing, certain scenarios can have
6645 * max load less than avg load(as we skip the groups at or below
6646 * its cpu_capacity, while calculating max_load..)
6648 if (busiest->avg_load <= sds->avg_load ||
6649 local->avg_load >= sds->avg_load) {
6651 return fix_small_imbalance(env, sds);
6655 * If there aren't any idle cpus, avoid creating some.
6657 if (busiest->group_type == group_overloaded &&
6658 local->group_type == group_overloaded) {
6659 load_above_capacity = busiest->sum_nr_running *
6661 if (load_above_capacity > busiest->group_capacity)
6662 load_above_capacity -= busiest->group_capacity;
6664 load_above_capacity = ~0UL;
6668 * We're trying to get all the cpus to the average_load, so we don't
6669 * want to push ourselves above the average load, nor do we wish to
6670 * reduce the max loaded cpu below the average load. At the same time,
6671 * we also don't want to reduce the group load below the group capacity
6672 * (so that we can implement power-savings policies etc). Thus we look
6673 * for the minimum possible imbalance.
6675 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6677 /* How much load to actually move to equalise the imbalance */
6678 env->imbalance = min(
6679 max_pull * busiest->group_capacity,
6680 (sds->avg_load - local->avg_load) * local->group_capacity
6681 ) / SCHED_CAPACITY_SCALE;
6684 * if *imbalance is less than the average load per runnable task
6685 * there is no guarantee that any tasks will be moved so we'll have
6686 * a think about bumping its value to force at least one task to be
6689 if (env->imbalance < busiest->load_per_task)
6690 return fix_small_imbalance(env, sds);
6693 /******* find_busiest_group() helpers end here *********************/
6696 * find_busiest_group - Returns the busiest group within the sched_domain
6697 * if there is an imbalance. If there isn't an imbalance, and
6698 * the user has opted for power-savings, it returns a group whose
6699 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
6700 * such a group exists.
6702 * Also calculates the amount of weighted load which should be moved
6703 * to restore balance.
6705 * @env: The load balancing environment.
6707 * Return: - The busiest group if imbalance exists.
6708 * - If no imbalance and user has opted for power-savings balance,
6709 * return the least loaded group whose CPUs can be
6710 * put to idle by rebalancing its tasks onto our group.
6712 static struct sched_group *find_busiest_group(struct lb_env *env)
6714 struct sg_lb_stats *local, *busiest;
6715 struct sd_lb_stats sds;
6717 init_sd_lb_stats(&sds);
6720 * Compute the various statistics relavent for load balancing at
6723 update_sd_lb_stats(env, &sds);
6724 local = &sds.local_stat;
6725 busiest = &sds.busiest_stat;
6727 /* ASYM feature bypasses nice load balance check */
6728 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
6729 check_asym_packing(env, &sds))
6732 /* There is no busy sibling group to pull tasks from */
6733 if (!sds.busiest || busiest->sum_nr_running == 0)
6736 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
6737 / sds.total_capacity;
6740 * If the busiest group is imbalanced the below checks don't
6741 * work because they assume all things are equal, which typically
6742 * isn't true due to cpus_allowed constraints and the like.
6744 if (busiest->group_type == group_imbalanced)
6747 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6748 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
6749 busiest->group_no_capacity)
6753 * If the local group is busier than the selected busiest group
6754 * don't try and pull any tasks.
6756 if (local->avg_load >= busiest->avg_load)
6760 * Don't pull any tasks if this group is already above the domain
6763 if (local->avg_load >= sds.avg_load)
6766 if (env->idle == CPU_IDLE) {
6768 * This cpu is idle. If the busiest group is not overloaded
6769 * and there is no imbalance between this and busiest group
6770 * wrt idle cpus, it is balanced. The imbalance becomes
6771 * significant if the diff is greater than 1 otherwise we
6772 * might end up to just move the imbalance on another group
6774 if ((busiest->group_type != group_overloaded) &&
6775 (local->idle_cpus <= (busiest->idle_cpus + 1)))
6779 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
6780 * imbalance_pct to be conservative.
6782 if (100 * busiest->avg_load <=
6783 env->sd->imbalance_pct * local->avg_load)
6788 /* Looks like there is an imbalance. Compute it */
6789 calculate_imbalance(env, &sds);
6798 * find_busiest_queue - find the busiest runqueue among the cpus in group.
6800 static struct rq *find_busiest_queue(struct lb_env *env,
6801 struct sched_group *group)
6803 struct rq *busiest = NULL, *rq;
6804 unsigned long busiest_load = 0, busiest_capacity = 1;
6807 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6808 unsigned long capacity, wl;
6812 rt = fbq_classify_rq(rq);
6815 * We classify groups/runqueues into three groups:
6816 * - regular: there are !numa tasks
6817 * - remote: there are numa tasks that run on the 'wrong' node
6818 * - all: there is no distinction
6820 * In order to avoid migrating ideally placed numa tasks,
6821 * ignore those when there's better options.
6823 * If we ignore the actual busiest queue to migrate another
6824 * task, the next balance pass can still reduce the busiest
6825 * queue by moving tasks around inside the node.
6827 * If we cannot move enough load due to this classification
6828 * the next pass will adjust the group classification and
6829 * allow migration of more tasks.
6831 * Both cases only affect the total convergence complexity.
6833 if (rt > env->fbq_type)
6836 capacity = capacity_of(i);
6838 wl = weighted_cpuload(i);
6841 * When comparing with imbalance, use weighted_cpuload()
6842 * which is not scaled with the cpu capacity.
6845 if (rq->nr_running == 1 && wl > env->imbalance &&
6846 !check_cpu_capacity(rq, env->sd))
6850 * For the load comparisons with the other cpu's, consider
6851 * the weighted_cpuload() scaled with the cpu capacity, so
6852 * that the load can be moved away from the cpu that is
6853 * potentially running at a lower capacity.
6855 * Thus we're looking for max(wl_i / capacity_i), crosswise
6856 * multiplication to rid ourselves of the division works out
6857 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
6858 * our previous maximum.
6860 if (wl * busiest_capacity > busiest_load * capacity) {
6862 busiest_capacity = capacity;
6871 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
6872 * so long as it is large enough.
6874 #define MAX_PINNED_INTERVAL 512
6876 /* Working cpumask for load_balance and load_balance_newidle. */
6877 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6879 static int need_active_balance(struct lb_env *env)
6881 struct sched_domain *sd = env->sd;
6883 if (env->idle == CPU_NEWLY_IDLE) {
6886 * ASYM_PACKING needs to force migrate tasks from busy but
6887 * higher numbered CPUs in order to pack all tasks in the
6888 * lowest numbered CPUs.
6890 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6895 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
6896 * It's worth migrating the task if the src_cpu's capacity is reduced
6897 * because of other sched_class or IRQs if more capacity stays
6898 * available on dst_cpu.
6900 if ((env->idle != CPU_NOT_IDLE) &&
6901 (env->src_rq->cfs.h_nr_running == 1)) {
6902 if ((check_cpu_capacity(env->src_rq, sd)) &&
6903 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
6907 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
6910 static int active_load_balance_cpu_stop(void *data);
6912 static int should_we_balance(struct lb_env *env)
6914 struct sched_group *sg = env->sd->groups;
6915 struct cpumask *sg_cpus, *sg_mask;
6916 int cpu, balance_cpu = -1;
6919 * In the newly idle case, we will allow all the cpu's
6920 * to do the newly idle load balance.
6922 if (env->idle == CPU_NEWLY_IDLE)
6925 sg_cpus = sched_group_cpus(sg);
6926 sg_mask = sched_group_mask(sg);
6927 /* Try to find first idle cpu */
6928 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
6929 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
6936 if (balance_cpu == -1)
6937 balance_cpu = group_balance_cpu(sg);
6940 * First idle cpu or the first cpu(busiest) in this sched group
6941 * is eligible for doing load balancing at this and above domains.
6943 return balance_cpu == env->dst_cpu;
6947 * Check this_cpu to ensure it is balanced within domain. Attempt to move
6948 * tasks if there is an imbalance.
6950 static int load_balance(int this_cpu, struct rq *this_rq,
6951 struct sched_domain *sd, enum cpu_idle_type idle,
6952 int *continue_balancing)
6954 int ld_moved, cur_ld_moved, active_balance = 0;
6955 struct sched_domain *sd_parent = sd->parent;
6956 struct sched_group *group;
6958 unsigned long flags;
6959 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6961 struct lb_env env = {
6963 .dst_cpu = this_cpu,
6965 .dst_grpmask = sched_group_cpus(sd->groups),
6967 .loop_break = sched_nr_migrate_break,
6970 .tasks = LIST_HEAD_INIT(env.tasks),
6974 * For NEWLY_IDLE load_balancing, we don't need to consider
6975 * other cpus in our group
6977 if (idle == CPU_NEWLY_IDLE)
6978 env.dst_grpmask = NULL;
6980 cpumask_copy(cpus, cpu_active_mask);
6982 schedstat_inc(sd, lb_count[idle]);
6985 if (!should_we_balance(&env)) {
6986 *continue_balancing = 0;
6990 group = find_busiest_group(&env);
6992 schedstat_inc(sd, lb_nobusyg[idle]);
6996 busiest = find_busiest_queue(&env, group);
6998 schedstat_inc(sd, lb_nobusyq[idle]);
7002 BUG_ON(busiest == env.dst_rq);
7004 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7006 env.src_cpu = busiest->cpu;
7007 env.src_rq = busiest;
7010 if (busiest->nr_running > 1) {
7012 * Attempt to move tasks. If find_busiest_group has found
7013 * an imbalance but busiest->nr_running <= 1, the group is
7014 * still unbalanced. ld_moved simply stays zero, so it is
7015 * correctly treated as an imbalance.
7017 env.flags |= LBF_ALL_PINNED;
7018 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7021 raw_spin_lock_irqsave(&busiest->lock, flags);
7024 * cur_ld_moved - load moved in current iteration
7025 * ld_moved - cumulative load moved across iterations
7027 cur_ld_moved = detach_tasks(&env);
7030 * We've detached some tasks from busiest_rq. Every
7031 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7032 * unlock busiest->lock, and we are able to be sure
7033 * that nobody can manipulate the tasks in parallel.
7034 * See task_rq_lock() family for the details.
7037 raw_spin_unlock(&busiest->lock);
7041 ld_moved += cur_ld_moved;
7044 local_irq_restore(flags);
7046 if (env.flags & LBF_NEED_BREAK) {
7047 env.flags &= ~LBF_NEED_BREAK;
7052 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7053 * us and move them to an alternate dst_cpu in our sched_group
7054 * where they can run. The upper limit on how many times we
7055 * iterate on same src_cpu is dependent on number of cpus in our
7058 * This changes load balance semantics a bit on who can move
7059 * load to a given_cpu. In addition to the given_cpu itself
7060 * (or a ilb_cpu acting on its behalf where given_cpu is
7061 * nohz-idle), we now have balance_cpu in a position to move
7062 * load to given_cpu. In rare situations, this may cause
7063 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7064 * _independently_ and at _same_ time to move some load to
7065 * given_cpu) causing exceess load to be moved to given_cpu.
7066 * This however should not happen so much in practice and
7067 * moreover subsequent load balance cycles should correct the
7068 * excess load moved.
7070 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7072 /* Prevent to re-select dst_cpu via env's cpus */
7073 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7075 env.dst_rq = cpu_rq(env.new_dst_cpu);
7076 env.dst_cpu = env.new_dst_cpu;
7077 env.flags &= ~LBF_DST_PINNED;
7079 env.loop_break = sched_nr_migrate_break;
7082 * Go back to "more_balance" rather than "redo" since we
7083 * need to continue with same src_cpu.
7089 * We failed to reach balance because of affinity.
7092 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7094 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7095 *group_imbalance = 1;
7098 /* All tasks on this runqueue were pinned by CPU affinity */
7099 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7100 cpumask_clear_cpu(cpu_of(busiest), cpus);
7101 if (!cpumask_empty(cpus)) {
7103 env.loop_break = sched_nr_migrate_break;
7106 goto out_all_pinned;
7111 schedstat_inc(sd, lb_failed[idle]);
7113 * Increment the failure counter only on periodic balance.
7114 * We do not want newidle balance, which can be very
7115 * frequent, pollute the failure counter causing
7116 * excessive cache_hot migrations and active balances.
7118 if (idle != CPU_NEWLY_IDLE)
7119 sd->nr_balance_failed++;
7121 if (need_active_balance(&env)) {
7122 raw_spin_lock_irqsave(&busiest->lock, flags);
7124 /* don't kick the active_load_balance_cpu_stop,
7125 * if the curr task on busiest cpu can't be
7128 if (!cpumask_test_cpu(this_cpu,
7129 tsk_cpus_allowed(busiest->curr))) {
7130 raw_spin_unlock_irqrestore(&busiest->lock,
7132 env.flags |= LBF_ALL_PINNED;
7133 goto out_one_pinned;
7137 * ->active_balance synchronizes accesses to
7138 * ->active_balance_work. Once set, it's cleared
7139 * only after active load balance is finished.
7141 if (!busiest->active_balance) {
7142 busiest->active_balance = 1;
7143 busiest->push_cpu = this_cpu;
7146 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7148 if (active_balance) {
7149 stop_one_cpu_nowait(cpu_of(busiest),
7150 active_load_balance_cpu_stop, busiest,
7151 &busiest->active_balance_work);
7155 * We've kicked active balancing, reset the failure
7158 sd->nr_balance_failed = sd->cache_nice_tries+1;
7161 sd->nr_balance_failed = 0;
7163 if (likely(!active_balance)) {
7164 /* We were unbalanced, so reset the balancing interval */
7165 sd->balance_interval = sd->min_interval;
7168 * If we've begun active balancing, start to back off. This
7169 * case may not be covered by the all_pinned logic if there
7170 * is only 1 task on the busy runqueue (because we don't call
7173 if (sd->balance_interval < sd->max_interval)
7174 sd->balance_interval *= 2;
7181 * We reach balance although we may have faced some affinity
7182 * constraints. Clear the imbalance flag if it was set.
7185 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7187 if (*group_imbalance)
7188 *group_imbalance = 0;
7193 * We reach balance because all tasks are pinned at this level so
7194 * we can't migrate them. Let the imbalance flag set so parent level
7195 * can try to migrate them.
7197 schedstat_inc(sd, lb_balanced[idle]);
7199 sd->nr_balance_failed = 0;
7202 /* tune up the balancing interval */
7203 if (((env.flags & LBF_ALL_PINNED) &&
7204 sd->balance_interval < MAX_PINNED_INTERVAL) ||
7205 (sd->balance_interval < sd->max_interval))
7206 sd->balance_interval *= 2;
7213 static inline unsigned long
7214 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
7216 unsigned long interval = sd->balance_interval;
7219 interval *= sd->busy_factor;
7221 /* scale ms to jiffies */
7222 interval = msecs_to_jiffies(interval);
7223 interval = clamp(interval, 1UL, max_load_balance_interval);
7229 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
7231 unsigned long interval, next;
7233 interval = get_sd_balance_interval(sd, cpu_busy);
7234 next = sd->last_balance + interval;
7236 if (time_after(*next_balance, next))
7237 *next_balance = next;
7241 * idle_balance is called by schedule() if this_cpu is about to become
7242 * idle. Attempts to pull tasks from other CPUs.
7244 static int idle_balance(struct rq *this_rq)
7246 unsigned long next_balance = jiffies + HZ;
7247 int this_cpu = this_rq->cpu;
7248 struct sched_domain *sd;
7249 int pulled_task = 0;
7252 idle_enter_fair(this_rq);
7255 * We must set idle_stamp _before_ calling idle_balance(), such that we
7256 * measure the duration of idle_balance() as idle time.
7258 this_rq->idle_stamp = rq_clock(this_rq);
7260 if (this_rq->avg_idle < sysctl_sched_migration_cost ||
7261 !this_rq->rd->overload) {
7263 sd = rcu_dereference_check_sched_domain(this_rq->sd);
7265 update_next_balance(sd, 0, &next_balance);
7271 raw_spin_unlock(&this_rq->lock);
7273 update_blocked_averages(this_cpu);
7275 for_each_domain(this_cpu, sd) {
7276 int continue_balancing = 1;
7277 u64 t0, domain_cost;
7279 if (!(sd->flags & SD_LOAD_BALANCE))
7282 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7283 update_next_balance(sd, 0, &next_balance);
7287 if (sd->flags & SD_BALANCE_NEWIDLE) {
7288 t0 = sched_clock_cpu(this_cpu);
7290 pulled_task = load_balance(this_cpu, this_rq,
7292 &continue_balancing);
7294 domain_cost = sched_clock_cpu(this_cpu) - t0;
7295 if (domain_cost > sd->max_newidle_lb_cost)
7296 sd->max_newidle_lb_cost = domain_cost;
7298 curr_cost += domain_cost;
7301 update_next_balance(sd, 0, &next_balance);
7304 * Stop searching for tasks to pull if there are
7305 * now runnable tasks on this rq.
7307 if (pulled_task || this_rq->nr_running > 0)
7312 raw_spin_lock(&this_rq->lock);
7314 if (curr_cost > this_rq->max_idle_balance_cost)
7315 this_rq->max_idle_balance_cost = curr_cost;
7318 * While browsing the domains, we released the rq lock, a task could
7319 * have been enqueued in the meantime. Since we're not going idle,
7320 * pretend we pulled a task.
7322 if (this_rq->cfs.h_nr_running && !pulled_task)
7326 /* Move the next balance forward */
7327 if (time_after(this_rq->next_balance, next_balance))
7328 this_rq->next_balance = next_balance;
7330 /* Is there a task of a high priority class? */
7331 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7335 idle_exit_fair(this_rq);
7336 this_rq->idle_stamp = 0;
7343 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7344 * running tasks off the busiest CPU onto idle CPUs. It requires at
7345 * least 1 task to be running on each physical CPU where possible, and
7346 * avoids physical / logical imbalances.
7348 static int active_load_balance_cpu_stop(void *data)
7350 struct rq *busiest_rq = data;
7351 int busiest_cpu = cpu_of(busiest_rq);
7352 int target_cpu = busiest_rq->push_cpu;
7353 struct rq *target_rq = cpu_rq(target_cpu);
7354 struct sched_domain *sd;
7355 struct task_struct *p = NULL;
7357 raw_spin_lock_irq(&busiest_rq->lock);
7359 /* make sure the requested cpu hasn't gone down in the meantime */
7360 if (unlikely(busiest_cpu != smp_processor_id() ||
7361 !busiest_rq->active_balance))
7364 /* Is there any task to move? */
7365 if (busiest_rq->nr_running <= 1)
7369 * This condition is "impossible", if it occurs
7370 * we need to fix it. Originally reported by
7371 * Bjorn Helgaas on a 128-cpu setup.
7373 BUG_ON(busiest_rq == target_rq);
7375 /* Search for an sd spanning us and the target CPU. */
7377 for_each_domain(target_cpu, sd) {
7378 if ((sd->flags & SD_LOAD_BALANCE) &&
7379 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
7384 struct lb_env env = {
7386 .dst_cpu = target_cpu,
7387 .dst_rq = target_rq,
7388 .src_cpu = busiest_rq->cpu,
7389 .src_rq = busiest_rq,
7393 schedstat_inc(sd, alb_count);
7395 p = detach_one_task(&env);
7397 schedstat_inc(sd, alb_pushed);
7399 schedstat_inc(sd, alb_failed);
7403 busiest_rq->active_balance = 0;
7404 raw_spin_unlock(&busiest_rq->lock);
7407 attach_one_task(target_rq, p);
7414 static inline int on_null_domain(struct rq *rq)
7416 return unlikely(!rcu_dereference_sched(rq->sd));
7419 #ifdef CONFIG_NO_HZ_COMMON
7421 * idle load balancing details
7422 * - When one of the busy CPUs notice that there may be an idle rebalancing
7423 * needed, they will kick the idle load balancer, which then does idle
7424 * load balancing for all the idle CPUs.
7427 cpumask_var_t idle_cpus_mask;
7429 unsigned long next_balance; /* in jiffy units */
7430 } nohz ____cacheline_aligned;
7432 static inline int find_new_ilb(void)
7434 int ilb = cpumask_first(nohz.idle_cpus_mask);
7436 if (ilb < nr_cpu_ids && idle_cpu(ilb))
7443 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7444 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7445 * CPU (if there is one).
7447 static void nohz_balancer_kick(void)
7451 nohz.next_balance++;
7453 ilb_cpu = find_new_ilb();
7455 if (ilb_cpu >= nr_cpu_ids)
7458 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7461 * Use smp_send_reschedule() instead of resched_cpu().
7462 * This way we generate a sched IPI on the target cpu which
7463 * is idle. And the softirq performing nohz idle load balance
7464 * will be run before returning from the IPI.
7466 smp_send_reschedule(ilb_cpu);
7470 static inline void nohz_balance_exit_idle(int cpu)
7472 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7474 * Completely isolated CPUs don't ever set, so we must test.
7476 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
7477 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
7478 atomic_dec(&nohz.nr_cpus);
7480 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7484 static inline void set_cpu_sd_state_busy(void)
7486 struct sched_domain *sd;
7487 int cpu = smp_processor_id();
7490 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7492 if (!sd || !sd->nohz_idle)
7496 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
7501 void set_cpu_sd_state_idle(void)
7503 struct sched_domain *sd;
7504 int cpu = smp_processor_id();
7507 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7509 if (!sd || sd->nohz_idle)
7513 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
7519 * This routine will record that the cpu is going idle with tick stopped.
7520 * This info will be used in performing idle load balancing in the future.
7522 void nohz_balance_enter_idle(int cpu)
7525 * If this cpu is going down, then nothing needs to be done.
7527 if (!cpu_active(cpu))
7530 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
7534 * If we're a completely isolated CPU, we don't play.
7536 if (on_null_domain(cpu_rq(cpu)))
7539 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
7540 atomic_inc(&nohz.nr_cpus);
7541 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7544 static int sched_ilb_notifier(struct notifier_block *nfb,
7545 unsigned long action, void *hcpu)
7547 switch (action & ~CPU_TASKS_FROZEN) {
7549 nohz_balance_exit_idle(smp_processor_id());
7557 static DEFINE_SPINLOCK(balancing);
7560 * Scale the max load_balance interval with the number of CPUs in the system.
7561 * This trades load-balance latency on larger machines for less cross talk.
7563 void update_max_interval(void)
7565 max_load_balance_interval = HZ*num_online_cpus()/10;
7569 * It checks each scheduling domain to see if it is due to be balanced,
7570 * and initiates a balancing operation if so.
7572 * Balancing parameters are set up in init_sched_domains.
7574 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7576 int continue_balancing = 1;
7578 unsigned long interval;
7579 struct sched_domain *sd;
7580 /* Earliest time when we have to do rebalance again */
7581 unsigned long next_balance = jiffies + 60*HZ;
7582 int update_next_balance = 0;
7583 int need_serialize, need_decay = 0;
7586 update_blocked_averages(cpu);
7589 for_each_domain(cpu, sd) {
7591 * Decay the newidle max times here because this is a regular
7592 * visit to all the domains. Decay ~1% per second.
7594 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
7595 sd->max_newidle_lb_cost =
7596 (sd->max_newidle_lb_cost * 253) / 256;
7597 sd->next_decay_max_lb_cost = jiffies + HZ;
7600 max_cost += sd->max_newidle_lb_cost;
7602 if (!(sd->flags & SD_LOAD_BALANCE))
7606 * Stop the load balance at this level. There is another
7607 * CPU in our sched group which is doing load balancing more
7610 if (!continue_balancing) {
7616 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7618 need_serialize = sd->flags & SD_SERIALIZE;
7619 if (need_serialize) {
7620 if (!spin_trylock(&balancing))
7624 if (time_after_eq(jiffies, sd->last_balance + interval)) {
7625 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7627 * The LBF_DST_PINNED logic could have changed
7628 * env->dst_cpu, so we can't know our idle
7629 * state even if we migrated tasks. Update it.
7631 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7633 sd->last_balance = jiffies;
7634 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7637 spin_unlock(&balancing);
7639 if (time_after(next_balance, sd->last_balance + interval)) {
7640 next_balance = sd->last_balance + interval;
7641 update_next_balance = 1;
7646 * Ensure the rq-wide value also decays but keep it at a
7647 * reasonable floor to avoid funnies with rq->avg_idle.
7649 rq->max_idle_balance_cost =
7650 max((u64)sysctl_sched_migration_cost, max_cost);
7655 * next_balance will be updated only when there is a need.
7656 * When the cpu is attached to null domain for ex, it will not be
7659 if (likely(update_next_balance)) {
7660 rq->next_balance = next_balance;
7662 #ifdef CONFIG_NO_HZ_COMMON
7664 * If this CPU has been elected to perform the nohz idle
7665 * balance. Other idle CPUs have already rebalanced with
7666 * nohz_idle_balance() and nohz.next_balance has been
7667 * updated accordingly. This CPU is now running the idle load
7668 * balance for itself and we need to update the
7669 * nohz.next_balance accordingly.
7671 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
7672 nohz.next_balance = rq->next_balance;
7677 #ifdef CONFIG_NO_HZ_COMMON
7679 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7680 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7682 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7684 int this_cpu = this_rq->cpu;
7687 /* Earliest time when we have to do rebalance again */
7688 unsigned long next_balance = jiffies + 60*HZ;
7689 int update_next_balance = 0;
7691 if (idle != CPU_IDLE ||
7692 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
7695 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7696 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7700 * If this cpu gets work to do, stop the load balancing
7701 * work being done for other cpus. Next load
7702 * balancing owner will pick it up.
7707 rq = cpu_rq(balance_cpu);
7710 * If time for next balance is due,
7713 if (time_after_eq(jiffies, rq->next_balance)) {
7714 raw_spin_lock_irq(&rq->lock);
7715 update_rq_clock(rq);
7716 update_idle_cpu_load(rq);
7717 raw_spin_unlock_irq(&rq->lock);
7718 rebalance_domains(rq, CPU_IDLE);
7721 if (time_after(next_balance, rq->next_balance)) {
7722 next_balance = rq->next_balance;
7723 update_next_balance = 1;
7728 * next_balance will be updated only when there is a need.
7729 * When the CPU is attached to null domain for ex, it will not be
7732 if (likely(update_next_balance))
7733 nohz.next_balance = next_balance;
7735 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7739 * Current heuristic for kicking the idle load balancer in the presence
7740 * of an idle cpu in the system.
7741 * - This rq has more than one task.
7742 * - This rq has at least one CFS task and the capacity of the CPU is
7743 * significantly reduced because of RT tasks or IRQs.
7744 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
7745 * multiple busy cpu.
7746 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
7747 * domain span are idle.
7749 static inline bool nohz_kick_needed(struct rq *rq)
7751 unsigned long now = jiffies;
7752 struct sched_domain *sd;
7753 struct sched_group_capacity *sgc;
7754 int nr_busy, cpu = rq->cpu;
7757 if (unlikely(rq->idle_balance))
7761 * We may be recently in ticked or tickless idle mode. At the first
7762 * busy tick after returning from idle, we will update the busy stats.
7764 set_cpu_sd_state_busy();
7765 nohz_balance_exit_idle(cpu);
7768 * None are in tickless mode and hence no need for NOHZ idle load
7771 if (likely(!atomic_read(&nohz.nr_cpus)))
7774 if (time_before(now, nohz.next_balance))
7777 if (rq->nr_running >= 2)
7781 sd = rcu_dereference(per_cpu(sd_busy, cpu));
7783 sgc = sd->groups->sgc;
7784 nr_busy = atomic_read(&sgc->nr_busy_cpus);
7793 sd = rcu_dereference(rq->sd);
7795 if ((rq->cfs.h_nr_running >= 1) &&
7796 check_cpu_capacity(rq, sd)) {
7802 sd = rcu_dereference(per_cpu(sd_asym, cpu));
7803 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7804 sched_domain_span(sd)) < cpu)) {
7814 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7818 * run_rebalance_domains is triggered when needed from the scheduler tick.
7819 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
7821 static void run_rebalance_domains(struct softirq_action *h)
7823 struct rq *this_rq = this_rq();
7824 enum cpu_idle_type idle = this_rq->idle_balance ?
7825 CPU_IDLE : CPU_NOT_IDLE;
7828 * If this cpu has a pending nohz_balance_kick, then do the
7829 * balancing on behalf of the other idle cpus whose ticks are
7830 * stopped. Do nohz_idle_balance *before* rebalance_domains to
7831 * give the idle cpus a chance to load balance. Else we may
7832 * load balance only within the local sched_domain hierarchy
7833 * and abort nohz_idle_balance altogether if we pull some load.
7835 nohz_idle_balance(this_rq, idle);
7836 rebalance_domains(this_rq, idle);
7840 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
7842 void trigger_load_balance(struct rq *rq)
7844 /* Don't need to rebalance while attached to NULL domain */
7845 if (unlikely(on_null_domain(rq)))
7848 if (time_after_eq(jiffies, rq->next_balance))
7849 raise_softirq(SCHED_SOFTIRQ);
7850 #ifdef CONFIG_NO_HZ_COMMON
7851 if (nohz_kick_needed(rq))
7852 nohz_balancer_kick();
7856 static void rq_online_fair(struct rq *rq)
7860 update_runtime_enabled(rq);
7863 static void rq_offline_fair(struct rq *rq)
7867 /* Ensure any throttled groups are reachable by pick_next_task */
7868 unthrottle_offline_cfs_rqs(rq);
7871 #endif /* CONFIG_SMP */
7874 * scheduler tick hitting a task of our scheduling class:
7876 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7878 struct cfs_rq *cfs_rq;
7879 struct sched_entity *se = &curr->se;
7881 for_each_sched_entity(se) {
7882 cfs_rq = cfs_rq_of(se);
7883 entity_tick(cfs_rq, se, queued);
7886 if (static_branch_unlikely(&sched_numa_balancing))
7887 task_tick_numa(rq, curr);
7891 * called on fork with the child task as argument from the parent's context
7892 * - child not yet on the tasklist
7893 * - preemption disabled
7895 static void task_fork_fair(struct task_struct *p)
7897 struct cfs_rq *cfs_rq;
7898 struct sched_entity *se = &p->se, *curr;
7899 int this_cpu = smp_processor_id();
7900 struct rq *rq = this_rq();
7901 unsigned long flags;
7903 raw_spin_lock_irqsave(&rq->lock, flags);
7905 update_rq_clock(rq);
7907 cfs_rq = task_cfs_rq(current);
7908 curr = cfs_rq->curr;
7911 * Not only the cpu but also the task_group of the parent might have
7912 * been changed after parent->se.parent,cfs_rq were copied to
7913 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
7914 * of child point to valid ones.
7917 __set_task_cpu(p, this_cpu);
7920 update_curr(cfs_rq);
7923 se->vruntime = curr->vruntime;
7924 place_entity(cfs_rq, se, 1);
7926 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
7928 * Upon rescheduling, sched_class::put_prev_task() will place
7929 * 'current' within the tree based on its new key value.
7931 swap(curr->vruntime, se->vruntime);
7935 se->vruntime -= cfs_rq->min_vruntime;
7937 raw_spin_unlock_irqrestore(&rq->lock, flags);
7941 * Priority of the task has changed. Check to see if we preempt
7945 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7947 if (!task_on_rq_queued(p))
7951 * Reschedule if we are currently running on this runqueue and
7952 * our priority decreased, or if we are not currently running on
7953 * this runqueue and our priority is higher than the current's
7955 if (rq->curr == p) {
7956 if (p->prio > oldprio)
7959 check_preempt_curr(rq, p, 0);
7962 static inline bool vruntime_normalized(struct task_struct *p)
7964 struct sched_entity *se = &p->se;
7967 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
7968 * the dequeue_entity(.flags=0) will already have normalized the
7975 * When !on_rq, vruntime of the task has usually NOT been normalized.
7976 * But there are some cases where it has already been normalized:
7978 * - A forked child which is waiting for being woken up by
7979 * wake_up_new_task().
7980 * - A task which has been woken up by try_to_wake_up() and
7981 * waiting for actually being woken up by sched_ttwu_pending().
7983 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
7989 static void detach_task_cfs_rq(struct task_struct *p)
7991 struct sched_entity *se = &p->se;
7992 struct cfs_rq *cfs_rq = cfs_rq_of(se);
7994 if (!vruntime_normalized(p)) {
7996 * Fix up our vruntime so that the current sleep doesn't
7997 * cause 'unlimited' sleep bonus.
7999 place_entity(cfs_rq, se, 0);
8000 se->vruntime -= cfs_rq->min_vruntime;
8003 /* Catch up with the cfs_rq and remove our load when we leave */
8004 detach_entity_load_avg(cfs_rq, se);
8007 static void attach_task_cfs_rq(struct task_struct *p)
8009 struct sched_entity *se = &p->se;
8010 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8012 #ifdef CONFIG_FAIR_GROUP_SCHED
8014 * Since the real-depth could have been changed (only FAIR
8015 * class maintain depth value), reset depth properly.
8017 se->depth = se->parent ? se->parent->depth + 1 : 0;
8020 /* Synchronize task with its cfs_rq */
8021 attach_entity_load_avg(cfs_rq, se);
8023 if (!vruntime_normalized(p))
8024 se->vruntime += cfs_rq->min_vruntime;
8027 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8029 detach_task_cfs_rq(p);
8032 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8034 attach_task_cfs_rq(p);
8036 if (task_on_rq_queued(p)) {
8038 * We were most likely switched from sched_rt, so
8039 * kick off the schedule if running, otherwise just see
8040 * if we can still preempt the current task.
8045 check_preempt_curr(rq, p, 0);
8049 /* Account for a task changing its policy or group.
8051 * This routine is mostly called to set cfs_rq->curr field when a task
8052 * migrates between groups/classes.
8054 static void set_curr_task_fair(struct rq *rq)
8056 struct sched_entity *se = &rq->curr->se;
8058 for_each_sched_entity(se) {
8059 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8061 set_next_entity(cfs_rq, se);
8062 /* ensure bandwidth has been allocated on our new cfs_rq */
8063 account_cfs_rq_runtime(cfs_rq, 0);
8067 void init_cfs_rq(struct cfs_rq *cfs_rq)
8069 cfs_rq->tasks_timeline = RB_ROOT;
8070 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8071 #ifndef CONFIG_64BIT
8072 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8075 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8076 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8080 #ifdef CONFIG_FAIR_GROUP_SCHED
8081 static void task_move_group_fair(struct task_struct *p)
8083 detach_task_cfs_rq(p);
8084 set_task_rq(p, task_cpu(p));
8087 /* Tell se's cfs_rq has been changed -- migrated */
8088 p->se.avg.last_update_time = 0;
8090 attach_task_cfs_rq(p);
8093 void free_fair_sched_group(struct task_group *tg)
8097 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8099 for_each_possible_cpu(i) {
8101 kfree(tg->cfs_rq[i]);
8104 remove_entity_load_avg(tg->se[i]);
8113 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8115 struct cfs_rq *cfs_rq;
8116 struct sched_entity *se;
8119 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8122 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8126 tg->shares = NICE_0_LOAD;
8128 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8130 for_each_possible_cpu(i) {
8131 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8132 GFP_KERNEL, cpu_to_node(i));
8136 se = kzalloc_node(sizeof(struct sched_entity),
8137 GFP_KERNEL, cpu_to_node(i));
8141 init_cfs_rq(cfs_rq);
8142 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8143 init_entity_runnable_average(se);
8154 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8156 struct rq *rq = cpu_rq(cpu);
8157 unsigned long flags;
8160 * Only empty task groups can be destroyed; so we can speculatively
8161 * check on_list without danger of it being re-added.
8163 if (!tg->cfs_rq[cpu]->on_list)
8166 raw_spin_lock_irqsave(&rq->lock, flags);
8167 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8168 raw_spin_unlock_irqrestore(&rq->lock, flags);
8171 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8172 struct sched_entity *se, int cpu,
8173 struct sched_entity *parent)
8175 struct rq *rq = cpu_rq(cpu);
8179 init_cfs_rq_runtime(cfs_rq);
8181 tg->cfs_rq[cpu] = cfs_rq;
8184 /* se could be NULL for root_task_group */
8189 se->cfs_rq = &rq->cfs;
8192 se->cfs_rq = parent->my_q;
8193 se->depth = parent->depth + 1;
8197 /* guarantee group entities always have weight */
8198 update_load_set(&se->load, NICE_0_LOAD);
8199 se->parent = parent;
8202 static DEFINE_MUTEX(shares_mutex);
8204 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
8207 unsigned long flags;
8210 * We can't change the weight of the root cgroup.
8215 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
8217 mutex_lock(&shares_mutex);
8218 if (tg->shares == shares)
8221 tg->shares = shares;
8222 for_each_possible_cpu(i) {
8223 struct rq *rq = cpu_rq(i);
8224 struct sched_entity *se;
8227 /* Propagate contribution to hierarchy */
8228 raw_spin_lock_irqsave(&rq->lock, flags);
8230 /* Possible calls to update_curr() need rq clock */
8231 update_rq_clock(rq);
8232 for_each_sched_entity(se)
8233 update_cfs_shares(group_cfs_rq(se));
8234 raw_spin_unlock_irqrestore(&rq->lock, flags);
8238 mutex_unlock(&shares_mutex);
8241 #else /* CONFIG_FAIR_GROUP_SCHED */
8243 void free_fair_sched_group(struct task_group *tg) { }
8245 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8250 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
8252 #endif /* CONFIG_FAIR_GROUP_SCHED */
8255 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8257 struct sched_entity *se = &task->se;
8258 unsigned int rr_interval = 0;
8261 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8264 if (rq->cfs.load.weight)
8265 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8271 * All the scheduling class methods:
8273 const struct sched_class fair_sched_class = {
8274 .next = &idle_sched_class,
8275 .enqueue_task = enqueue_task_fair,
8276 .dequeue_task = dequeue_task_fair,
8277 .yield_task = yield_task_fair,
8278 .yield_to_task = yield_to_task_fair,
8280 .check_preempt_curr = check_preempt_wakeup,
8282 .pick_next_task = pick_next_task_fair,
8283 .put_prev_task = put_prev_task_fair,
8286 .select_task_rq = select_task_rq_fair,
8287 .migrate_task_rq = migrate_task_rq_fair,
8289 .rq_online = rq_online_fair,
8290 .rq_offline = rq_offline_fair,
8292 .task_waking = task_waking_fair,
8293 .task_dead = task_dead_fair,
8294 .set_cpus_allowed = set_cpus_allowed_common,
8297 .set_curr_task = set_curr_task_fair,
8298 .task_tick = task_tick_fair,
8299 .task_fork = task_fork_fair,
8301 .prio_changed = prio_changed_fair,
8302 .switched_from = switched_from_fair,
8303 .switched_to = switched_to_fair,
8305 .get_rr_interval = get_rr_interval_fair,
8307 .update_curr = update_curr_fair,
8309 #ifdef CONFIG_FAIR_GROUP_SCHED
8310 .task_move_group = task_move_group_fair,
8314 #ifdef CONFIG_SCHED_DEBUG
8315 void print_cfs_stats(struct seq_file *m, int cpu)
8317 struct cfs_rq *cfs_rq;
8320 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8321 print_cfs_rq(m, cpu, cfs_rq);
8325 #ifdef CONFIG_NUMA_BALANCING
8326 void show_numa_stats(struct task_struct *p, struct seq_file *m)
8329 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
8331 for_each_online_node(node) {
8332 if (p->numa_faults) {
8333 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
8334 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
8336 if (p->numa_group) {
8337 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
8338 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
8340 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
8343 #endif /* CONFIG_NUMA_BALANCING */
8344 #endif /* CONFIG_SCHED_DEBUG */
8346 __init void init_sched_fair_class(void)
8349 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
8351 #ifdef CONFIG_NO_HZ_COMMON
8352 nohz.next_balance = jiffies;
8353 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8354 cpu_notifier(sched_ilb_notifier, 0);