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>
33 #include <linux/module.h>
35 #include <trace/events/sched.h>
42 * Targeted preemption latency for CPU-bound tasks:
43 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
45 * NOTE: this latency value is not the same as the concept of
46 * 'timeslice length' - timeslices in CFS are of variable length
47 * and have no persistent notion like in traditional, time-slice
48 * based scheduling concepts.
50 * (to see the precise effective timeslice length of your workload,
51 * run vmstat and monitor the context-switches (cs) field)
53 unsigned int sysctl_sched_latency = 6000000ULL;
54 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
56 unsigned int sysctl_sched_is_big_little = 0;
57 unsigned int sysctl_sched_sync_hint_enable = 1;
58 unsigned int sysctl_sched_initial_task_util = 0;
59 unsigned int sysctl_sched_cstate_aware = 1;
61 #ifdef CONFIG_SCHED_WALT
62 unsigned int sysctl_sched_use_walt_cpu_util = 1;
63 unsigned int sysctl_sched_use_walt_task_util = 1;
64 __read_mostly unsigned int sysctl_sched_walt_cpu_high_irqload =
68 * The initial- and re-scaling of tunables is configurable
69 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
72 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
73 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
74 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
76 enum sched_tunable_scaling sysctl_sched_tunable_scaling
77 = SCHED_TUNABLESCALING_LOG;
80 * Minimal preemption granularity for CPU-bound tasks:
81 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
83 unsigned int sysctl_sched_min_granularity = 750000ULL;
84 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
87 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
89 static unsigned int sched_nr_latency = 8;
92 * After fork, child runs first. If set to 0 (default) then
93 * parent will (try to) run first.
95 unsigned int sysctl_sched_child_runs_first __read_mostly;
98 * SCHED_OTHER wake-up granularity.
99 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
101 * This option delays the preemption effects of decoupled workloads
102 * and reduces their over-scheduling. Synchronous workloads will still
103 * have immediate wakeup/sleep latencies.
105 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
106 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
108 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
111 * The exponential sliding window over which load is averaged for shares
115 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
117 #ifdef CONFIG_CFS_BANDWIDTH
119 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
120 * each time a cfs_rq requests quota.
122 * Note: in the case that the slice exceeds the runtime remaining (either due
123 * to consumption or the quota being specified to be smaller than the slice)
124 * we will always only issue the remaining available time.
126 * default: 5 msec, units: microseconds
128 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
131 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
137 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
143 static inline void update_load_set(struct load_weight *lw, unsigned long w)
150 * Increase the granularity value when there are more CPUs,
151 * because with more CPUs the 'effective latency' as visible
152 * to users decreases. But the relationship is not linear,
153 * so pick a second-best guess by going with the log2 of the
156 * This idea comes from the SD scheduler of Con Kolivas:
158 static unsigned int get_update_sysctl_factor(void)
160 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
163 switch (sysctl_sched_tunable_scaling) {
164 case SCHED_TUNABLESCALING_NONE:
167 case SCHED_TUNABLESCALING_LINEAR:
170 case SCHED_TUNABLESCALING_LOG:
172 factor = 1 + ilog2(cpus);
179 static void update_sysctl(void)
181 unsigned int factor = get_update_sysctl_factor();
183 #define SET_SYSCTL(name) \
184 (sysctl_##name = (factor) * normalized_sysctl_##name)
185 SET_SYSCTL(sched_min_granularity);
186 SET_SYSCTL(sched_latency);
187 SET_SYSCTL(sched_wakeup_granularity);
191 void sched_init_granularity(void)
196 #define WMULT_CONST (~0U)
197 #define WMULT_SHIFT 32
199 static void __update_inv_weight(struct load_weight *lw)
203 if (likely(lw->inv_weight))
206 w = scale_load_down(lw->weight);
208 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
210 else if (unlikely(!w))
211 lw->inv_weight = WMULT_CONST;
213 lw->inv_weight = WMULT_CONST / w;
217 * delta_exec * weight / lw.weight
219 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
221 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
222 * we're guaranteed shift stays positive because inv_weight is guaranteed to
223 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
225 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
226 * weight/lw.weight <= 1, and therefore our shift will also be positive.
228 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
230 u64 fact = scale_load_down(weight);
231 int shift = WMULT_SHIFT;
233 __update_inv_weight(lw);
235 if (unlikely(fact >> 32)) {
242 /* hint to use a 32x32->64 mul */
243 fact = (u64)(u32)fact * lw->inv_weight;
250 return mul_u64_u32_shr(delta_exec, fact, shift);
254 const struct sched_class fair_sched_class;
256 /**************************************************************
257 * CFS operations on generic schedulable entities:
260 #ifdef CONFIG_FAIR_GROUP_SCHED
262 /* cpu runqueue to which this cfs_rq is attached */
263 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
268 /* An entity is a task if it doesn't "own" a runqueue */
269 #define entity_is_task(se) (!se->my_q)
271 static inline struct task_struct *task_of(struct sched_entity *se)
273 #ifdef CONFIG_SCHED_DEBUG
274 WARN_ON_ONCE(!entity_is_task(se));
276 return container_of(se, struct task_struct, se);
279 /* Walk up scheduling entities hierarchy */
280 #define for_each_sched_entity(se) \
281 for (; se; se = se->parent)
283 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
288 /* runqueue on which this entity is (to be) queued */
289 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
294 /* runqueue "owned" by this group */
295 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
300 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
302 if (!cfs_rq->on_list) {
304 * Ensure we either appear before our parent (if already
305 * enqueued) or force our parent to appear after us when it is
306 * enqueued. The fact that we always enqueue bottom-up
307 * reduces this to two cases.
309 if (cfs_rq->tg->parent &&
310 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
311 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
312 &rq_of(cfs_rq)->leaf_cfs_rq_list);
314 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
315 &rq_of(cfs_rq)->leaf_cfs_rq_list);
322 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
324 if (cfs_rq->on_list) {
325 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
330 /* Iterate thr' all leaf cfs_rq's on a runqueue */
331 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
332 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
334 /* Do the two (enqueued) entities belong to the same group ? */
335 static inline struct cfs_rq *
336 is_same_group(struct sched_entity *se, struct sched_entity *pse)
338 if (se->cfs_rq == pse->cfs_rq)
344 static inline struct sched_entity *parent_entity(struct sched_entity *se)
350 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
352 int se_depth, pse_depth;
355 * preemption test can be made between sibling entities who are in the
356 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
357 * both tasks until we find their ancestors who are siblings of common
361 /* First walk up until both entities are at same depth */
362 se_depth = (*se)->depth;
363 pse_depth = (*pse)->depth;
365 while (se_depth > pse_depth) {
367 *se = parent_entity(*se);
370 while (pse_depth > se_depth) {
372 *pse = parent_entity(*pse);
375 while (!is_same_group(*se, *pse)) {
376 *se = parent_entity(*se);
377 *pse = parent_entity(*pse);
381 #else /* !CONFIG_FAIR_GROUP_SCHED */
383 static inline struct task_struct *task_of(struct sched_entity *se)
385 return container_of(se, struct task_struct, se);
388 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
390 return container_of(cfs_rq, struct rq, cfs);
393 #define entity_is_task(se) 1
395 #define for_each_sched_entity(se) \
396 for (; se; se = NULL)
398 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
400 return &task_rq(p)->cfs;
403 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
405 struct task_struct *p = task_of(se);
406 struct rq *rq = task_rq(p);
411 /* runqueue "owned" by this group */
412 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
417 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
421 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
425 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
426 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
428 static inline struct sched_entity *parent_entity(struct sched_entity *se)
434 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
438 #endif /* CONFIG_FAIR_GROUP_SCHED */
440 static __always_inline
441 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
443 /**************************************************************
444 * Scheduling class tree data structure manipulation methods:
447 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
449 s64 delta = (s64)(vruntime - max_vruntime);
451 max_vruntime = vruntime;
456 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
458 s64 delta = (s64)(vruntime - min_vruntime);
460 min_vruntime = vruntime;
465 static inline int entity_before(struct sched_entity *a,
466 struct sched_entity *b)
468 return (s64)(a->vruntime - b->vruntime) < 0;
471 static void update_min_vruntime(struct cfs_rq *cfs_rq)
473 u64 vruntime = cfs_rq->min_vruntime;
476 vruntime = cfs_rq->curr->vruntime;
478 if (cfs_rq->rb_leftmost) {
479 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
484 vruntime = se->vruntime;
486 vruntime = min_vruntime(vruntime, se->vruntime);
489 /* ensure we never gain time by being placed backwards. */
490 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
493 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
498 * Enqueue an entity into the rb-tree:
500 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
502 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
503 struct rb_node *parent = NULL;
504 struct sched_entity *entry;
508 * Find the right place in the rbtree:
512 entry = rb_entry(parent, struct sched_entity, run_node);
514 * We dont care about collisions. Nodes with
515 * the same key stay together.
517 if (entity_before(se, entry)) {
518 link = &parent->rb_left;
520 link = &parent->rb_right;
526 * Maintain a cache of leftmost tree entries (it is frequently
530 cfs_rq->rb_leftmost = &se->run_node;
532 rb_link_node(&se->run_node, parent, link);
533 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
536 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
538 if (cfs_rq->rb_leftmost == &se->run_node) {
539 struct rb_node *next_node;
541 next_node = rb_next(&se->run_node);
542 cfs_rq->rb_leftmost = next_node;
545 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
548 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
550 struct rb_node *left = cfs_rq->rb_leftmost;
555 return rb_entry(left, struct sched_entity, run_node);
558 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
560 struct rb_node *next = rb_next(&se->run_node);
565 return rb_entry(next, struct sched_entity, run_node);
568 #ifdef CONFIG_SCHED_DEBUG
569 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
571 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
576 return rb_entry(last, struct sched_entity, run_node);
579 /**************************************************************
580 * Scheduling class statistics methods:
583 int sched_proc_update_handler(struct ctl_table *table, int write,
584 void __user *buffer, size_t *lenp,
587 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
588 unsigned int factor = get_update_sysctl_factor();
593 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
594 sysctl_sched_min_granularity);
596 #define WRT_SYSCTL(name) \
597 (normalized_sysctl_##name = sysctl_##name / (factor))
598 WRT_SYSCTL(sched_min_granularity);
599 WRT_SYSCTL(sched_latency);
600 WRT_SYSCTL(sched_wakeup_granularity);
610 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
612 if (unlikely(se->load.weight != NICE_0_LOAD))
613 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
619 * The idea is to set a period in which each task runs once.
621 * When there are too many tasks (sched_nr_latency) we have to stretch
622 * this period because otherwise the slices get too small.
624 * p = (nr <= nl) ? l : l*nr/nl
626 static u64 __sched_period(unsigned long nr_running)
628 if (unlikely(nr_running > sched_nr_latency))
629 return nr_running * sysctl_sched_min_granularity;
631 return sysctl_sched_latency;
635 * We calculate the wall-time slice from the period by taking a part
636 * proportional to the weight.
640 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
642 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
644 for_each_sched_entity(se) {
645 struct load_weight *load;
646 struct load_weight lw;
648 cfs_rq = cfs_rq_of(se);
649 load = &cfs_rq->load;
651 if (unlikely(!se->on_rq)) {
654 update_load_add(&lw, se->load.weight);
657 slice = __calc_delta(slice, se->load.weight, load);
663 * We calculate the vruntime slice of a to-be-inserted task.
667 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
669 return calc_delta_fair(sched_slice(cfs_rq, se), se);
673 static int select_idle_sibling(struct task_struct *p, int cpu);
674 static unsigned long task_h_load(struct task_struct *p);
677 * We choose a half-life close to 1 scheduling period.
678 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
679 * dependent on this value.
681 #define LOAD_AVG_PERIOD 32
682 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
683 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
685 /* Give new sched_entity start runnable values to heavy its load in infant time */
686 void init_entity_runnable_average(struct sched_entity *se)
688 struct sched_avg *sa = &se->avg;
690 sa->last_update_time = 0;
692 * sched_avg's period_contrib should be strictly less then 1024, so
693 * we give it 1023 to make sure it is almost a period (1024us), and
694 * will definitely be update (after enqueue).
696 sa->period_contrib = 1023;
697 sa->load_avg = scale_load_down(se->load.weight);
698 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
699 sa->util_avg = sched_freq() ?
700 sysctl_sched_initial_task_util :
701 scale_load_down(SCHED_LOAD_SCALE);
702 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
703 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
707 void init_entity_runnable_average(struct sched_entity *se)
713 * Update the current task's runtime statistics.
715 static void update_curr(struct cfs_rq *cfs_rq)
717 struct sched_entity *curr = cfs_rq->curr;
718 u64 now = rq_clock_task(rq_of(cfs_rq));
724 delta_exec = now - curr->exec_start;
725 if (unlikely((s64)delta_exec <= 0))
728 curr->exec_start = now;
730 schedstat_set(curr->statistics.exec_max,
731 max(delta_exec, curr->statistics.exec_max));
733 curr->sum_exec_runtime += delta_exec;
734 schedstat_add(cfs_rq, exec_clock, delta_exec);
736 curr->vruntime += calc_delta_fair(delta_exec, curr);
737 update_min_vruntime(cfs_rq);
739 if (entity_is_task(curr)) {
740 struct task_struct *curtask = task_of(curr);
742 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
743 cpuacct_charge(curtask, delta_exec);
744 account_group_exec_runtime(curtask, delta_exec);
747 account_cfs_rq_runtime(cfs_rq, delta_exec);
750 static void update_curr_fair(struct rq *rq)
752 update_curr(cfs_rq_of(&rq->curr->se));
756 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
758 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
762 * Task is being enqueued - update stats:
764 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
767 * Are we enqueueing a waiting task? (for current tasks
768 * a dequeue/enqueue event is a NOP)
770 if (se != cfs_rq->curr)
771 update_stats_wait_start(cfs_rq, se);
775 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
777 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
778 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
779 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
780 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
781 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
782 #ifdef CONFIG_SCHEDSTATS
783 if (entity_is_task(se)) {
784 trace_sched_stat_wait(task_of(se),
785 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
788 schedstat_set(se->statistics.wait_start, 0);
792 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
795 * Mark the end of the wait period if dequeueing a
798 if (se != cfs_rq->curr)
799 update_stats_wait_end(cfs_rq, se);
803 * We are picking a new current task - update its stats:
806 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
809 * We are starting a new run period:
811 se->exec_start = rq_clock_task(rq_of(cfs_rq));
814 /**************************************************
815 * Scheduling class queueing methods:
818 #ifdef CONFIG_NUMA_BALANCING
820 * Approximate time to scan a full NUMA task in ms. The task scan period is
821 * calculated based on the tasks virtual memory size and
822 * numa_balancing_scan_size.
824 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
825 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
827 /* Portion of address space to scan in MB */
828 unsigned int sysctl_numa_balancing_scan_size = 256;
830 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
831 unsigned int sysctl_numa_balancing_scan_delay = 1000;
833 static unsigned int task_nr_scan_windows(struct task_struct *p)
835 unsigned long rss = 0;
836 unsigned long nr_scan_pages;
839 * Calculations based on RSS as non-present and empty pages are skipped
840 * by the PTE scanner and NUMA hinting faults should be trapped based
843 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
844 rss = get_mm_rss(p->mm);
848 rss = round_up(rss, nr_scan_pages);
849 return rss / nr_scan_pages;
852 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
853 #define MAX_SCAN_WINDOW 2560
855 static unsigned int task_scan_min(struct task_struct *p)
857 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
858 unsigned int scan, floor;
859 unsigned int windows = 1;
861 if (scan_size < MAX_SCAN_WINDOW)
862 windows = MAX_SCAN_WINDOW / scan_size;
863 floor = 1000 / windows;
865 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
866 return max_t(unsigned int, floor, scan);
869 static unsigned int task_scan_max(struct task_struct *p)
871 unsigned int smin = task_scan_min(p);
874 /* Watch for min being lower than max due to floor calculations */
875 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
876 return max(smin, smax);
879 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
881 rq->nr_numa_running += (p->numa_preferred_nid != -1);
882 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
885 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
887 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
888 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
894 spinlock_t lock; /* nr_tasks, tasks */
899 nodemask_t active_nodes;
900 unsigned long total_faults;
902 * Faults_cpu is used to decide whether memory should move
903 * towards the CPU. As a consequence, these stats are weighted
904 * more by CPU use than by memory faults.
906 unsigned long *faults_cpu;
907 unsigned long faults[0];
910 /* Shared or private faults. */
911 #define NR_NUMA_HINT_FAULT_TYPES 2
913 /* Memory and CPU locality */
914 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
916 /* Averaged statistics, and temporary buffers. */
917 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
919 pid_t task_numa_group_id(struct task_struct *p)
921 return p->numa_group ? p->numa_group->gid : 0;
925 * The averaged statistics, shared & private, memory & cpu,
926 * occupy the first half of the array. The second half of the
927 * array is for current counters, which are averaged into the
928 * first set by task_numa_placement.
930 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
932 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
935 static inline unsigned long task_faults(struct task_struct *p, int nid)
940 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
941 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
944 static inline unsigned long group_faults(struct task_struct *p, int nid)
949 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
950 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
953 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
955 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
956 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
959 /* Handle placement on systems where not all nodes are directly connected. */
960 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
961 int maxdist, bool task)
963 unsigned long score = 0;
967 * All nodes are directly connected, and the same distance
968 * from each other. No need for fancy placement algorithms.
970 if (sched_numa_topology_type == NUMA_DIRECT)
974 * This code is called for each node, introducing N^2 complexity,
975 * which should be ok given the number of nodes rarely exceeds 8.
977 for_each_online_node(node) {
978 unsigned long faults;
979 int dist = node_distance(nid, node);
982 * The furthest away nodes in the system are not interesting
983 * for placement; nid was already counted.
985 if (dist == sched_max_numa_distance || node == nid)
989 * On systems with a backplane NUMA topology, compare groups
990 * of nodes, and move tasks towards the group with the most
991 * memory accesses. When comparing two nodes at distance
992 * "hoplimit", only nodes closer by than "hoplimit" are part
993 * of each group. Skip other nodes.
995 if (sched_numa_topology_type == NUMA_BACKPLANE &&
999 /* Add up the faults from nearby nodes. */
1001 faults = task_faults(p, node);
1003 faults = group_faults(p, node);
1006 * On systems with a glueless mesh NUMA topology, there are
1007 * no fixed "groups of nodes". Instead, nodes that are not
1008 * directly connected bounce traffic through intermediate
1009 * nodes; a numa_group can occupy any set of nodes.
1010 * The further away a node is, the less the faults count.
1011 * This seems to result in good task placement.
1013 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1014 faults *= (sched_max_numa_distance - dist);
1015 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1025 * These return the fraction of accesses done by a particular task, or
1026 * task group, on a particular numa node. The group weight is given a
1027 * larger multiplier, in order to group tasks together that are almost
1028 * evenly spread out between numa nodes.
1030 static inline unsigned long task_weight(struct task_struct *p, int nid,
1033 unsigned long faults, total_faults;
1035 if (!p->numa_faults)
1038 total_faults = p->total_numa_faults;
1043 faults = task_faults(p, nid);
1044 faults += score_nearby_nodes(p, nid, dist, true);
1046 return 1000 * faults / total_faults;
1049 static inline unsigned long group_weight(struct task_struct *p, int nid,
1052 unsigned long faults, total_faults;
1057 total_faults = p->numa_group->total_faults;
1062 faults = group_faults(p, nid);
1063 faults += score_nearby_nodes(p, nid, dist, false);
1065 return 1000 * faults / total_faults;
1068 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1069 int src_nid, int dst_cpu)
1071 struct numa_group *ng = p->numa_group;
1072 int dst_nid = cpu_to_node(dst_cpu);
1073 int last_cpupid, this_cpupid;
1075 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1078 * Multi-stage node selection is used in conjunction with a periodic
1079 * migration fault to build a temporal task<->page relation. By using
1080 * a two-stage filter we remove short/unlikely relations.
1082 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1083 * a task's usage of a particular page (n_p) per total usage of this
1084 * page (n_t) (in a given time-span) to a probability.
1086 * Our periodic faults will sample this probability and getting the
1087 * same result twice in a row, given these samples are fully
1088 * independent, is then given by P(n)^2, provided our sample period
1089 * is sufficiently short compared to the usage pattern.
1091 * This quadric squishes small probabilities, making it less likely we
1092 * act on an unlikely task<->page relation.
1094 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1095 if (!cpupid_pid_unset(last_cpupid) &&
1096 cpupid_to_nid(last_cpupid) != dst_nid)
1099 /* Always allow migrate on private faults */
1100 if (cpupid_match_pid(p, last_cpupid))
1103 /* A shared fault, but p->numa_group has not been set up yet. */
1108 * Do not migrate if the destination is not a node that
1109 * is actively used by this numa group.
1111 if (!node_isset(dst_nid, ng->active_nodes))
1115 * Source is a node that is not actively used by this
1116 * numa group, while the destination is. Migrate.
1118 if (!node_isset(src_nid, ng->active_nodes))
1122 * Both source and destination are nodes in active
1123 * use by this numa group. Maximize memory bandwidth
1124 * by migrating from more heavily used groups, to less
1125 * heavily used ones, spreading the load around.
1126 * Use a 1/4 hysteresis to avoid spurious page movement.
1128 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1131 static unsigned long weighted_cpuload(const int cpu);
1132 static unsigned long source_load(int cpu, int type);
1133 static unsigned long target_load(int cpu, int type);
1134 static unsigned long capacity_of(int cpu);
1135 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1137 /* Cached statistics for all CPUs within a node */
1139 unsigned long nr_running;
1142 /* Total compute capacity of CPUs on a node */
1143 unsigned long compute_capacity;
1145 /* Approximate capacity in terms of runnable tasks on a node */
1146 unsigned long task_capacity;
1147 int has_free_capacity;
1151 * XXX borrowed from update_sg_lb_stats
1153 static void update_numa_stats(struct numa_stats *ns, int nid)
1155 int smt, cpu, cpus = 0;
1156 unsigned long capacity;
1158 memset(ns, 0, sizeof(*ns));
1159 for_each_cpu(cpu, cpumask_of_node(nid)) {
1160 struct rq *rq = cpu_rq(cpu);
1162 ns->nr_running += rq->nr_running;
1163 ns->load += weighted_cpuload(cpu);
1164 ns->compute_capacity += capacity_of(cpu);
1170 * If we raced with hotplug and there are no CPUs left in our mask
1171 * the @ns structure is NULL'ed and task_numa_compare() will
1172 * not find this node attractive.
1174 * We'll either bail at !has_free_capacity, or we'll detect a huge
1175 * imbalance and bail there.
1180 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1181 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1182 capacity = cpus / smt; /* cores */
1184 ns->task_capacity = min_t(unsigned, capacity,
1185 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1186 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1189 struct task_numa_env {
1190 struct task_struct *p;
1192 int src_cpu, src_nid;
1193 int dst_cpu, dst_nid;
1195 struct numa_stats src_stats, dst_stats;
1200 struct task_struct *best_task;
1205 static void task_numa_assign(struct task_numa_env *env,
1206 struct task_struct *p, long imp)
1209 put_task_struct(env->best_task);
1212 env->best_imp = imp;
1213 env->best_cpu = env->dst_cpu;
1216 static bool load_too_imbalanced(long src_load, long dst_load,
1217 struct task_numa_env *env)
1220 long orig_src_load, orig_dst_load;
1221 long src_capacity, dst_capacity;
1224 * The load is corrected for the CPU capacity available on each node.
1227 * ------------ vs ---------
1228 * src_capacity dst_capacity
1230 src_capacity = env->src_stats.compute_capacity;
1231 dst_capacity = env->dst_stats.compute_capacity;
1233 /* We care about the slope of the imbalance, not the direction. */
1234 if (dst_load < src_load)
1235 swap(dst_load, src_load);
1237 /* Is the difference below the threshold? */
1238 imb = dst_load * src_capacity * 100 -
1239 src_load * dst_capacity * env->imbalance_pct;
1244 * The imbalance is above the allowed threshold.
1245 * Compare it with the old imbalance.
1247 orig_src_load = env->src_stats.load;
1248 orig_dst_load = env->dst_stats.load;
1250 if (orig_dst_load < orig_src_load)
1251 swap(orig_dst_load, orig_src_load);
1253 old_imb = orig_dst_load * src_capacity * 100 -
1254 orig_src_load * dst_capacity * env->imbalance_pct;
1256 /* Would this change make things worse? */
1257 return (imb > old_imb);
1261 * This checks if the overall compute and NUMA accesses of the system would
1262 * be improved if the source tasks was migrated to the target dst_cpu taking
1263 * into account that it might be best if task running on the dst_cpu should
1264 * be exchanged with the source task
1266 static void task_numa_compare(struct task_numa_env *env,
1267 long taskimp, long groupimp)
1269 struct rq *src_rq = cpu_rq(env->src_cpu);
1270 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1271 struct task_struct *cur;
1272 long src_load, dst_load;
1274 long imp = env->p->numa_group ? groupimp : taskimp;
1276 int dist = env->dist;
1277 bool assigned = false;
1281 raw_spin_lock_irq(&dst_rq->lock);
1284 * No need to move the exiting task or idle task.
1286 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1290 * The task_struct must be protected here to protect the
1291 * p->numa_faults access in the task_weight since the
1292 * numa_faults could already be freed in the following path:
1293 * finish_task_switch()
1294 * --> put_task_struct()
1295 * --> __put_task_struct()
1296 * --> task_numa_free()
1298 get_task_struct(cur);
1301 raw_spin_unlock_irq(&dst_rq->lock);
1304 * Because we have preemption enabled we can get migrated around and
1305 * end try selecting ourselves (current == env->p) as a swap candidate.
1311 * "imp" is the fault differential for the source task between the
1312 * source and destination node. Calculate the total differential for
1313 * the source task and potential destination task. The more negative
1314 * the value is, the more rmeote accesses that would be expected to
1315 * be incurred if the tasks were swapped.
1318 /* Skip this swap candidate if cannot move to the source cpu */
1319 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1323 * If dst and source tasks are in the same NUMA group, or not
1324 * in any group then look only at task weights.
1326 if (cur->numa_group == env->p->numa_group) {
1327 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1328 task_weight(cur, env->dst_nid, dist);
1330 * Add some hysteresis to prevent swapping the
1331 * tasks within a group over tiny differences.
1333 if (cur->numa_group)
1337 * Compare the group weights. If a task is all by
1338 * itself (not part of a group), use the task weight
1341 if (cur->numa_group)
1342 imp += group_weight(cur, env->src_nid, dist) -
1343 group_weight(cur, env->dst_nid, dist);
1345 imp += task_weight(cur, env->src_nid, dist) -
1346 task_weight(cur, env->dst_nid, dist);
1350 if (imp <= env->best_imp && moveimp <= env->best_imp)
1354 /* Is there capacity at our destination? */
1355 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1356 !env->dst_stats.has_free_capacity)
1362 /* Balance doesn't matter much if we're running a task per cpu */
1363 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1364 dst_rq->nr_running == 1)
1368 * In the overloaded case, try and keep the load balanced.
1371 load = task_h_load(env->p);
1372 dst_load = env->dst_stats.load + load;
1373 src_load = env->src_stats.load - load;
1375 if (moveimp > imp && moveimp > env->best_imp) {
1377 * If the improvement from just moving env->p direction is
1378 * better than swapping tasks around, check if a move is
1379 * possible. Store a slightly smaller score than moveimp,
1380 * so an actually idle CPU will win.
1382 if (!load_too_imbalanced(src_load, dst_load, env)) {
1384 put_task_struct(cur);
1390 if (imp <= env->best_imp)
1394 load = task_h_load(cur);
1399 if (load_too_imbalanced(src_load, dst_load, env))
1403 * One idle CPU per node is evaluated for a task numa move.
1404 * Call select_idle_sibling to maybe find a better one.
1407 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1411 task_numa_assign(env, cur, imp);
1415 * The dst_rq->curr isn't assigned. The protection for task_struct is
1418 if (cur && !assigned)
1419 put_task_struct(cur);
1422 static void task_numa_find_cpu(struct task_numa_env *env,
1423 long taskimp, long groupimp)
1427 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1428 /* Skip this CPU if the source task cannot migrate */
1429 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1433 task_numa_compare(env, taskimp, groupimp);
1437 /* Only move tasks to a NUMA node less busy than the current node. */
1438 static bool numa_has_capacity(struct task_numa_env *env)
1440 struct numa_stats *src = &env->src_stats;
1441 struct numa_stats *dst = &env->dst_stats;
1443 if (src->has_free_capacity && !dst->has_free_capacity)
1447 * Only consider a task move if the source has a higher load
1448 * than the destination, corrected for CPU capacity on each node.
1450 * src->load dst->load
1451 * --------------------- vs ---------------------
1452 * src->compute_capacity dst->compute_capacity
1454 if (src->load * dst->compute_capacity * env->imbalance_pct >
1456 dst->load * src->compute_capacity * 100)
1462 static int task_numa_migrate(struct task_struct *p)
1464 struct task_numa_env env = {
1467 .src_cpu = task_cpu(p),
1468 .src_nid = task_node(p),
1470 .imbalance_pct = 112,
1476 struct sched_domain *sd;
1477 unsigned long taskweight, groupweight;
1479 long taskimp, groupimp;
1482 * Pick the lowest SD_NUMA domain, as that would have the smallest
1483 * imbalance and would be the first to start moving tasks about.
1485 * And we want to avoid any moving of tasks about, as that would create
1486 * random movement of tasks -- counter the numa conditions we're trying
1490 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1492 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1496 * Cpusets can break the scheduler domain tree into smaller
1497 * balance domains, some of which do not cross NUMA boundaries.
1498 * Tasks that are "trapped" in such domains cannot be migrated
1499 * elsewhere, so there is no point in (re)trying.
1501 if (unlikely(!sd)) {
1502 p->numa_preferred_nid = task_node(p);
1506 env.dst_nid = p->numa_preferred_nid;
1507 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1508 taskweight = task_weight(p, env.src_nid, dist);
1509 groupweight = group_weight(p, env.src_nid, dist);
1510 update_numa_stats(&env.src_stats, env.src_nid);
1511 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1512 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1513 update_numa_stats(&env.dst_stats, env.dst_nid);
1515 /* Try to find a spot on the preferred nid. */
1516 if (numa_has_capacity(&env))
1517 task_numa_find_cpu(&env, taskimp, groupimp);
1520 * Look at other nodes in these cases:
1521 * - there is no space available on the preferred_nid
1522 * - the task is part of a numa_group that is interleaved across
1523 * multiple NUMA nodes; in order to better consolidate the group,
1524 * we need to check other locations.
1526 if (env.best_cpu == -1 || (p->numa_group &&
1527 nodes_weight(p->numa_group->active_nodes) > 1)) {
1528 for_each_online_node(nid) {
1529 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1532 dist = node_distance(env.src_nid, env.dst_nid);
1533 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1535 taskweight = task_weight(p, env.src_nid, dist);
1536 groupweight = group_weight(p, env.src_nid, dist);
1539 /* Only consider nodes where both task and groups benefit */
1540 taskimp = task_weight(p, nid, dist) - taskweight;
1541 groupimp = group_weight(p, nid, dist) - groupweight;
1542 if (taskimp < 0 && groupimp < 0)
1547 update_numa_stats(&env.dst_stats, env.dst_nid);
1548 if (numa_has_capacity(&env))
1549 task_numa_find_cpu(&env, taskimp, groupimp);
1554 * If the task is part of a workload that spans multiple NUMA nodes,
1555 * and is migrating into one of the workload's active nodes, remember
1556 * this node as the task's preferred numa node, so the workload can
1558 * A task that migrated to a second choice node will be better off
1559 * trying for a better one later. Do not set the preferred node here.
1561 if (p->numa_group) {
1562 if (env.best_cpu == -1)
1567 if (node_isset(nid, p->numa_group->active_nodes))
1568 sched_setnuma(p, env.dst_nid);
1571 /* No better CPU than the current one was found. */
1572 if (env.best_cpu == -1)
1576 * Reset the scan period if the task is being rescheduled on an
1577 * alternative node to recheck if the tasks is now properly placed.
1579 p->numa_scan_period = task_scan_min(p);
1581 if (env.best_task == NULL) {
1582 ret = migrate_task_to(p, env.best_cpu);
1584 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1588 ret = migrate_swap(p, env.best_task);
1590 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1591 put_task_struct(env.best_task);
1595 /* Attempt to migrate a task to a CPU on the preferred node. */
1596 static void numa_migrate_preferred(struct task_struct *p)
1598 unsigned long interval = HZ;
1600 /* This task has no NUMA fault statistics yet */
1601 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1604 /* Periodically retry migrating the task to the preferred node */
1605 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1606 p->numa_migrate_retry = jiffies + interval;
1608 /* Success if task is already running on preferred CPU */
1609 if (task_node(p) == p->numa_preferred_nid)
1612 /* Otherwise, try migrate to a CPU on the preferred node */
1613 task_numa_migrate(p);
1617 * Find the nodes on which the workload is actively running. We do this by
1618 * tracking the nodes from which NUMA hinting faults are triggered. This can
1619 * be different from the set of nodes where the workload's memory is currently
1622 * The bitmask is used to make smarter decisions on when to do NUMA page
1623 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1624 * are added when they cause over 6/16 of the maximum number of faults, but
1625 * only removed when they drop below 3/16.
1627 static void update_numa_active_node_mask(struct numa_group *numa_group)
1629 unsigned long faults, max_faults = 0;
1632 for_each_online_node(nid) {
1633 faults = group_faults_cpu(numa_group, nid);
1634 if (faults > max_faults)
1635 max_faults = faults;
1638 for_each_online_node(nid) {
1639 faults = group_faults_cpu(numa_group, nid);
1640 if (!node_isset(nid, numa_group->active_nodes)) {
1641 if (faults > max_faults * 6 / 16)
1642 node_set(nid, numa_group->active_nodes);
1643 } else if (faults < max_faults * 3 / 16)
1644 node_clear(nid, numa_group->active_nodes);
1649 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1650 * increments. The more local the fault statistics are, the higher the scan
1651 * period will be for the next scan window. If local/(local+remote) ratio is
1652 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1653 * the scan period will decrease. Aim for 70% local accesses.
1655 #define NUMA_PERIOD_SLOTS 10
1656 #define NUMA_PERIOD_THRESHOLD 7
1659 * Increase the scan period (slow down scanning) if the majority of
1660 * our memory is already on our local node, or if the majority of
1661 * the page accesses are shared with other processes.
1662 * Otherwise, decrease the scan period.
1664 static void update_task_scan_period(struct task_struct *p,
1665 unsigned long shared, unsigned long private)
1667 unsigned int period_slot;
1671 unsigned long remote = p->numa_faults_locality[0];
1672 unsigned long local = p->numa_faults_locality[1];
1675 * If there were no record hinting faults then either the task is
1676 * completely idle or all activity is areas that are not of interest
1677 * to automatic numa balancing. Related to that, if there were failed
1678 * migration then it implies we are migrating too quickly or the local
1679 * node is overloaded. In either case, scan slower
1681 if (local + shared == 0 || p->numa_faults_locality[2]) {
1682 p->numa_scan_period = min(p->numa_scan_period_max,
1683 p->numa_scan_period << 1);
1685 p->mm->numa_next_scan = jiffies +
1686 msecs_to_jiffies(p->numa_scan_period);
1692 * Prepare to scale scan period relative to the current period.
1693 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1694 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1695 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1697 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1698 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1699 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1700 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1703 diff = slot * period_slot;
1705 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1708 * Scale scan rate increases based on sharing. There is an
1709 * inverse relationship between the degree of sharing and
1710 * the adjustment made to the scanning period. Broadly
1711 * speaking the intent is that there is little point
1712 * scanning faster if shared accesses dominate as it may
1713 * simply bounce migrations uselessly
1715 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1716 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1719 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1720 task_scan_min(p), task_scan_max(p));
1721 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1725 * Get the fraction of time the task has been running since the last
1726 * NUMA placement cycle. The scheduler keeps similar statistics, but
1727 * decays those on a 32ms period, which is orders of magnitude off
1728 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1729 * stats only if the task is so new there are no NUMA statistics yet.
1731 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1733 u64 runtime, delta, now;
1734 /* Use the start of this time slice to avoid calculations. */
1735 now = p->se.exec_start;
1736 runtime = p->se.sum_exec_runtime;
1738 if (p->last_task_numa_placement) {
1739 delta = runtime - p->last_sum_exec_runtime;
1740 *period = now - p->last_task_numa_placement;
1742 delta = p->se.avg.load_sum / p->se.load.weight;
1743 *period = LOAD_AVG_MAX;
1746 p->last_sum_exec_runtime = runtime;
1747 p->last_task_numa_placement = now;
1753 * Determine the preferred nid for a task in a numa_group. This needs to
1754 * be done in a way that produces consistent results with group_weight,
1755 * otherwise workloads might not converge.
1757 static int preferred_group_nid(struct task_struct *p, int nid)
1762 /* Direct connections between all NUMA nodes. */
1763 if (sched_numa_topology_type == NUMA_DIRECT)
1767 * On a system with glueless mesh NUMA topology, group_weight
1768 * scores nodes according to the number of NUMA hinting faults on
1769 * both the node itself, and on nearby nodes.
1771 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1772 unsigned long score, max_score = 0;
1773 int node, max_node = nid;
1775 dist = sched_max_numa_distance;
1777 for_each_online_node(node) {
1778 score = group_weight(p, node, dist);
1779 if (score > max_score) {
1788 * Finding the preferred nid in a system with NUMA backplane
1789 * interconnect topology is more involved. The goal is to locate
1790 * tasks from numa_groups near each other in the system, and
1791 * untangle workloads from different sides of the system. This requires
1792 * searching down the hierarchy of node groups, recursively searching
1793 * inside the highest scoring group of nodes. The nodemask tricks
1794 * keep the complexity of the search down.
1796 nodes = node_online_map;
1797 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1798 unsigned long max_faults = 0;
1799 nodemask_t max_group = NODE_MASK_NONE;
1802 /* Are there nodes at this distance from each other? */
1803 if (!find_numa_distance(dist))
1806 for_each_node_mask(a, nodes) {
1807 unsigned long faults = 0;
1808 nodemask_t this_group;
1809 nodes_clear(this_group);
1811 /* Sum group's NUMA faults; includes a==b case. */
1812 for_each_node_mask(b, nodes) {
1813 if (node_distance(a, b) < dist) {
1814 faults += group_faults(p, b);
1815 node_set(b, this_group);
1816 node_clear(b, nodes);
1820 /* Remember the top group. */
1821 if (faults > max_faults) {
1822 max_faults = faults;
1823 max_group = this_group;
1825 * subtle: at the smallest distance there is
1826 * just one node left in each "group", the
1827 * winner is the preferred nid.
1832 /* Next round, evaluate the nodes within max_group. */
1840 static void task_numa_placement(struct task_struct *p)
1842 int seq, nid, max_nid = -1, max_group_nid = -1;
1843 unsigned long max_faults = 0, max_group_faults = 0;
1844 unsigned long fault_types[2] = { 0, 0 };
1845 unsigned long total_faults;
1846 u64 runtime, period;
1847 spinlock_t *group_lock = NULL;
1850 * The p->mm->numa_scan_seq field gets updated without
1851 * exclusive access. Use READ_ONCE() here to ensure
1852 * that the field is read in a single access:
1854 seq = READ_ONCE(p->mm->numa_scan_seq);
1855 if (p->numa_scan_seq == seq)
1857 p->numa_scan_seq = seq;
1858 p->numa_scan_period_max = task_scan_max(p);
1860 total_faults = p->numa_faults_locality[0] +
1861 p->numa_faults_locality[1];
1862 runtime = numa_get_avg_runtime(p, &period);
1864 /* If the task is part of a group prevent parallel updates to group stats */
1865 if (p->numa_group) {
1866 group_lock = &p->numa_group->lock;
1867 spin_lock_irq(group_lock);
1870 /* Find the node with the highest number of faults */
1871 for_each_online_node(nid) {
1872 /* Keep track of the offsets in numa_faults array */
1873 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1874 unsigned long faults = 0, group_faults = 0;
1877 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1878 long diff, f_diff, f_weight;
1880 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1881 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1882 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1883 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1885 /* Decay existing window, copy faults since last scan */
1886 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1887 fault_types[priv] += p->numa_faults[membuf_idx];
1888 p->numa_faults[membuf_idx] = 0;
1891 * Normalize the faults_from, so all tasks in a group
1892 * count according to CPU use, instead of by the raw
1893 * number of faults. Tasks with little runtime have
1894 * little over-all impact on throughput, and thus their
1895 * faults are less important.
1897 f_weight = div64_u64(runtime << 16, period + 1);
1898 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1900 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1901 p->numa_faults[cpubuf_idx] = 0;
1903 p->numa_faults[mem_idx] += diff;
1904 p->numa_faults[cpu_idx] += f_diff;
1905 faults += p->numa_faults[mem_idx];
1906 p->total_numa_faults += diff;
1907 if (p->numa_group) {
1909 * safe because we can only change our own group
1911 * mem_idx represents the offset for a given
1912 * nid and priv in a specific region because it
1913 * is at the beginning of the numa_faults array.
1915 p->numa_group->faults[mem_idx] += diff;
1916 p->numa_group->faults_cpu[mem_idx] += f_diff;
1917 p->numa_group->total_faults += diff;
1918 group_faults += p->numa_group->faults[mem_idx];
1922 if (faults > max_faults) {
1923 max_faults = faults;
1927 if (group_faults > max_group_faults) {
1928 max_group_faults = group_faults;
1929 max_group_nid = nid;
1933 update_task_scan_period(p, fault_types[0], fault_types[1]);
1935 if (p->numa_group) {
1936 update_numa_active_node_mask(p->numa_group);
1937 spin_unlock_irq(group_lock);
1938 max_nid = preferred_group_nid(p, max_group_nid);
1942 /* Set the new preferred node */
1943 if (max_nid != p->numa_preferred_nid)
1944 sched_setnuma(p, max_nid);
1946 if (task_node(p) != p->numa_preferred_nid)
1947 numa_migrate_preferred(p);
1951 static inline int get_numa_group(struct numa_group *grp)
1953 return atomic_inc_not_zero(&grp->refcount);
1956 static inline void put_numa_group(struct numa_group *grp)
1958 if (atomic_dec_and_test(&grp->refcount))
1959 kfree_rcu(grp, rcu);
1962 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1965 struct numa_group *grp, *my_grp;
1966 struct task_struct *tsk;
1968 int cpu = cpupid_to_cpu(cpupid);
1971 if (unlikely(!p->numa_group)) {
1972 unsigned int size = sizeof(struct numa_group) +
1973 4*nr_node_ids*sizeof(unsigned long);
1975 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1979 atomic_set(&grp->refcount, 1);
1980 spin_lock_init(&grp->lock);
1982 /* Second half of the array tracks nids where faults happen */
1983 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1986 node_set(task_node(current), grp->active_nodes);
1988 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1989 grp->faults[i] = p->numa_faults[i];
1991 grp->total_faults = p->total_numa_faults;
1994 rcu_assign_pointer(p->numa_group, grp);
1998 tsk = READ_ONCE(cpu_rq(cpu)->curr);
2000 if (!cpupid_match_pid(tsk, cpupid))
2003 grp = rcu_dereference(tsk->numa_group);
2007 my_grp = p->numa_group;
2012 * Only join the other group if its bigger; if we're the bigger group,
2013 * the other task will join us.
2015 if (my_grp->nr_tasks > grp->nr_tasks)
2019 * Tie-break on the grp address.
2021 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2024 /* Always join threads in the same process. */
2025 if (tsk->mm == current->mm)
2028 /* Simple filter to avoid false positives due to PID collisions */
2029 if (flags & TNF_SHARED)
2032 /* Update priv based on whether false sharing was detected */
2035 if (join && !get_numa_group(grp))
2043 BUG_ON(irqs_disabled());
2044 double_lock_irq(&my_grp->lock, &grp->lock);
2046 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2047 my_grp->faults[i] -= p->numa_faults[i];
2048 grp->faults[i] += p->numa_faults[i];
2050 my_grp->total_faults -= p->total_numa_faults;
2051 grp->total_faults += p->total_numa_faults;
2056 spin_unlock(&my_grp->lock);
2057 spin_unlock_irq(&grp->lock);
2059 rcu_assign_pointer(p->numa_group, grp);
2061 put_numa_group(my_grp);
2069 void task_numa_free(struct task_struct *p)
2071 struct numa_group *grp = p->numa_group;
2072 void *numa_faults = p->numa_faults;
2073 unsigned long flags;
2077 spin_lock_irqsave(&grp->lock, flags);
2078 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2079 grp->faults[i] -= p->numa_faults[i];
2080 grp->total_faults -= p->total_numa_faults;
2083 spin_unlock_irqrestore(&grp->lock, flags);
2084 RCU_INIT_POINTER(p->numa_group, NULL);
2085 put_numa_group(grp);
2088 p->numa_faults = NULL;
2093 * Got a PROT_NONE fault for a page on @node.
2095 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2097 struct task_struct *p = current;
2098 bool migrated = flags & TNF_MIGRATED;
2099 int cpu_node = task_node(current);
2100 int local = !!(flags & TNF_FAULT_LOCAL);
2103 if (!static_branch_likely(&sched_numa_balancing))
2106 /* for example, ksmd faulting in a user's mm */
2110 /* Allocate buffer to track faults on a per-node basis */
2111 if (unlikely(!p->numa_faults)) {
2112 int size = sizeof(*p->numa_faults) *
2113 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2115 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2116 if (!p->numa_faults)
2119 p->total_numa_faults = 0;
2120 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2124 * First accesses are treated as private, otherwise consider accesses
2125 * to be private if the accessing pid has not changed
2127 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2130 priv = cpupid_match_pid(p, last_cpupid);
2131 if (!priv && !(flags & TNF_NO_GROUP))
2132 task_numa_group(p, last_cpupid, flags, &priv);
2136 * If a workload spans multiple NUMA nodes, a shared fault that
2137 * occurs wholly within the set of nodes that the workload is
2138 * actively using should be counted as local. This allows the
2139 * scan rate to slow down when a workload has settled down.
2141 if (!priv && !local && p->numa_group &&
2142 node_isset(cpu_node, p->numa_group->active_nodes) &&
2143 node_isset(mem_node, p->numa_group->active_nodes))
2146 task_numa_placement(p);
2149 * Retry task to preferred node migration periodically, in case it
2150 * case it previously failed, or the scheduler moved us.
2152 if (time_after(jiffies, p->numa_migrate_retry))
2153 numa_migrate_preferred(p);
2156 p->numa_pages_migrated += pages;
2157 if (flags & TNF_MIGRATE_FAIL)
2158 p->numa_faults_locality[2] += pages;
2160 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2161 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2162 p->numa_faults_locality[local] += pages;
2165 static void reset_ptenuma_scan(struct task_struct *p)
2168 * We only did a read acquisition of the mmap sem, so
2169 * p->mm->numa_scan_seq is written to without exclusive access
2170 * and the update is not guaranteed to be atomic. That's not
2171 * much of an issue though, since this is just used for
2172 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2173 * expensive, to avoid any form of compiler optimizations:
2175 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2176 p->mm->numa_scan_offset = 0;
2180 * The expensive part of numa migration is done from task_work context.
2181 * Triggered from task_tick_numa().
2183 void task_numa_work(struct callback_head *work)
2185 unsigned long migrate, next_scan, now = jiffies;
2186 struct task_struct *p = current;
2187 struct mm_struct *mm = p->mm;
2188 struct vm_area_struct *vma;
2189 unsigned long start, end;
2190 unsigned long nr_pte_updates = 0;
2191 long pages, virtpages;
2193 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2195 work->next = work; /* protect against double add */
2197 * Who cares about NUMA placement when they're dying.
2199 * NOTE: make sure not to dereference p->mm before this check,
2200 * exit_task_work() happens _after_ exit_mm() so we could be called
2201 * without p->mm even though we still had it when we enqueued this
2204 if (p->flags & PF_EXITING)
2207 if (!mm->numa_next_scan) {
2208 mm->numa_next_scan = now +
2209 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2213 * Enforce maximal scan/migration frequency..
2215 migrate = mm->numa_next_scan;
2216 if (time_before(now, migrate))
2219 if (p->numa_scan_period == 0) {
2220 p->numa_scan_period_max = task_scan_max(p);
2221 p->numa_scan_period = task_scan_min(p);
2224 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2225 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2229 * Delay this task enough that another task of this mm will likely win
2230 * the next time around.
2232 p->node_stamp += 2 * TICK_NSEC;
2234 start = mm->numa_scan_offset;
2235 pages = sysctl_numa_balancing_scan_size;
2236 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2237 virtpages = pages * 8; /* Scan up to this much virtual space */
2242 down_read(&mm->mmap_sem);
2243 vma = find_vma(mm, start);
2245 reset_ptenuma_scan(p);
2249 for (; vma; vma = vma->vm_next) {
2250 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2251 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2256 * Shared library pages mapped by multiple processes are not
2257 * migrated as it is expected they are cache replicated. Avoid
2258 * hinting faults in read-only file-backed mappings or the vdso
2259 * as migrating the pages will be of marginal benefit.
2262 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2266 * Skip inaccessible VMAs to avoid any confusion between
2267 * PROT_NONE and NUMA hinting ptes
2269 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2273 start = max(start, vma->vm_start);
2274 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2275 end = min(end, vma->vm_end);
2276 nr_pte_updates = change_prot_numa(vma, start, end);
2279 * Try to scan sysctl_numa_balancing_size worth of
2280 * hpages that have at least one present PTE that
2281 * is not already pte-numa. If the VMA contains
2282 * areas that are unused or already full of prot_numa
2283 * PTEs, scan up to virtpages, to skip through those
2287 pages -= (end - start) >> PAGE_SHIFT;
2288 virtpages -= (end - start) >> PAGE_SHIFT;
2291 if (pages <= 0 || virtpages <= 0)
2295 } while (end != vma->vm_end);
2300 * It is possible to reach the end of the VMA list but the last few
2301 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2302 * would find the !migratable VMA on the next scan but not reset the
2303 * scanner to the start so check it now.
2306 mm->numa_scan_offset = start;
2308 reset_ptenuma_scan(p);
2309 up_read(&mm->mmap_sem);
2313 * Drive the periodic memory faults..
2315 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2317 struct callback_head *work = &curr->numa_work;
2321 * We don't care about NUMA placement if we don't have memory.
2323 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2327 * Using runtime rather than walltime has the dual advantage that
2328 * we (mostly) drive the selection from busy threads and that the
2329 * task needs to have done some actual work before we bother with
2332 now = curr->se.sum_exec_runtime;
2333 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2335 if (now > curr->node_stamp + period) {
2336 if (!curr->node_stamp)
2337 curr->numa_scan_period = task_scan_min(curr);
2338 curr->node_stamp += period;
2340 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2341 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2342 task_work_add(curr, work, true);
2347 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2351 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2355 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2358 #endif /* CONFIG_NUMA_BALANCING */
2361 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2363 update_load_add(&cfs_rq->load, se->load.weight);
2364 if (!parent_entity(se))
2365 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2367 if (entity_is_task(se)) {
2368 struct rq *rq = rq_of(cfs_rq);
2370 account_numa_enqueue(rq, task_of(se));
2371 list_add(&se->group_node, &rq->cfs_tasks);
2374 cfs_rq->nr_running++;
2378 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2380 update_load_sub(&cfs_rq->load, se->load.weight);
2381 if (!parent_entity(se))
2382 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2383 if (entity_is_task(se)) {
2384 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2385 list_del_init(&se->group_node);
2387 cfs_rq->nr_running--;
2390 #ifdef CONFIG_FAIR_GROUP_SCHED
2392 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2397 * Use this CPU's real-time load instead of the last load contribution
2398 * as the updating of the contribution is delayed, and we will use the
2399 * the real-time load to calc the share. See update_tg_load_avg().
2401 tg_weight = atomic_long_read(&tg->load_avg);
2402 tg_weight -= cfs_rq->tg_load_avg_contrib;
2403 tg_weight += cfs_rq->load.weight;
2408 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2410 long tg_weight, load, shares;
2412 tg_weight = calc_tg_weight(tg, cfs_rq);
2413 load = cfs_rq->load.weight;
2415 shares = (tg->shares * load);
2417 shares /= tg_weight;
2419 if (shares < MIN_SHARES)
2420 shares = MIN_SHARES;
2421 if (shares > tg->shares)
2422 shares = tg->shares;
2426 # else /* CONFIG_SMP */
2427 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2431 # endif /* CONFIG_SMP */
2432 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2433 unsigned long weight)
2436 /* commit outstanding execution time */
2437 if (cfs_rq->curr == se)
2438 update_curr(cfs_rq);
2439 account_entity_dequeue(cfs_rq, se);
2442 update_load_set(&se->load, weight);
2445 account_entity_enqueue(cfs_rq, se);
2448 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2450 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2452 struct task_group *tg;
2453 struct sched_entity *se;
2457 se = tg->se[cpu_of(rq_of(cfs_rq))];
2458 if (!se || throttled_hierarchy(cfs_rq))
2461 if (likely(se->load.weight == tg->shares))
2464 shares = calc_cfs_shares(cfs_rq, tg);
2466 reweight_entity(cfs_rq_of(se), se, shares);
2468 #else /* CONFIG_FAIR_GROUP_SCHED */
2469 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2472 #endif /* CONFIG_FAIR_GROUP_SCHED */
2475 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2476 static const u32 runnable_avg_yN_inv[] = {
2477 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2478 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2479 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2480 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2481 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2482 0x85aac367, 0x82cd8698,
2486 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2487 * over-estimates when re-combining.
2489 static const u32 runnable_avg_yN_sum[] = {
2490 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2491 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2492 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2497 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2499 static __always_inline u64 decay_load(u64 val, u64 n)
2501 unsigned int local_n;
2505 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2508 /* after bounds checking we can collapse to 32-bit */
2512 * As y^PERIOD = 1/2, we can combine
2513 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2514 * With a look-up table which covers y^n (n<PERIOD)
2516 * To achieve constant time decay_load.
2518 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2519 val >>= local_n / LOAD_AVG_PERIOD;
2520 local_n %= LOAD_AVG_PERIOD;
2523 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2528 * For updates fully spanning n periods, the contribution to runnable
2529 * average will be: \Sum 1024*y^n
2531 * We can compute this reasonably efficiently by combining:
2532 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2534 static u32 __compute_runnable_contrib(u64 n)
2538 if (likely(n <= LOAD_AVG_PERIOD))
2539 return runnable_avg_yN_sum[n];
2540 else if (unlikely(n >= LOAD_AVG_MAX_N))
2541 return LOAD_AVG_MAX;
2543 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2545 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2546 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2548 n -= LOAD_AVG_PERIOD;
2549 } while (n > LOAD_AVG_PERIOD);
2551 contrib = decay_load(contrib, n);
2552 return contrib + runnable_avg_yN_sum[n];
2555 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2556 #error "load tracking assumes 2^10 as unit"
2559 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2562 * We can represent the historical contribution to runnable average as the
2563 * coefficients of a geometric series. To do this we sub-divide our runnable
2564 * history into segments of approximately 1ms (1024us); label the segment that
2565 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2567 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2569 * (now) (~1ms ago) (~2ms ago)
2571 * Let u_i denote the fraction of p_i that the entity was runnable.
2573 * We then designate the fractions u_i as our co-efficients, yielding the
2574 * following representation of historical load:
2575 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2577 * We choose y based on the with of a reasonably scheduling period, fixing:
2580 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2581 * approximately half as much as the contribution to load within the last ms
2584 * When a period "rolls over" and we have new u_0`, multiplying the previous
2585 * sum again by y is sufficient to update:
2586 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2587 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2589 static __always_inline int
2590 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2591 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2593 u64 delta, scaled_delta, periods;
2595 unsigned int delta_w, scaled_delta_w, decayed = 0;
2596 unsigned long scale_freq, scale_cpu;
2598 delta = now - sa->last_update_time;
2600 * This should only happen when time goes backwards, which it
2601 * unfortunately does during sched clock init when we swap over to TSC.
2603 if ((s64)delta < 0) {
2604 sa->last_update_time = now;
2609 * Use 1024ns as the unit of measurement since it's a reasonable
2610 * approximation of 1us and fast to compute.
2615 sa->last_update_time = now;
2617 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2618 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2619 trace_sched_contrib_scale_f(cpu, scale_freq, scale_cpu);
2621 /* delta_w is the amount already accumulated against our next period */
2622 delta_w = sa->period_contrib;
2623 if (delta + delta_w >= 1024) {
2626 /* how much left for next period will start over, we don't know yet */
2627 sa->period_contrib = 0;
2630 * Now that we know we're crossing a period boundary, figure
2631 * out how much from delta we need to complete the current
2632 * period and accrue it.
2634 delta_w = 1024 - delta_w;
2635 scaled_delta_w = cap_scale(delta_w, scale_freq);
2637 sa->load_sum += weight * scaled_delta_w;
2639 cfs_rq->runnable_load_sum +=
2640 weight * scaled_delta_w;
2644 sa->util_sum += scaled_delta_w * scale_cpu;
2648 /* Figure out how many additional periods this update spans */
2649 periods = delta / 1024;
2652 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2654 cfs_rq->runnable_load_sum =
2655 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2657 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2659 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2660 contrib = __compute_runnable_contrib(periods);
2661 contrib = cap_scale(contrib, scale_freq);
2663 sa->load_sum += weight * contrib;
2665 cfs_rq->runnable_load_sum += weight * contrib;
2668 sa->util_sum += contrib * scale_cpu;
2671 /* Remainder of delta accrued against u_0` */
2672 scaled_delta = cap_scale(delta, scale_freq);
2674 sa->load_sum += weight * scaled_delta;
2676 cfs_rq->runnable_load_sum += weight * scaled_delta;
2679 sa->util_sum += scaled_delta * scale_cpu;
2681 sa->period_contrib += delta;
2684 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2686 cfs_rq->runnable_load_avg =
2687 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2689 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2695 #ifdef CONFIG_FAIR_GROUP_SCHED
2697 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2698 * and effective_load (which is not done because it is too costly).
2700 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2702 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2704 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2705 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2706 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2710 #else /* CONFIG_FAIR_GROUP_SCHED */
2711 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2712 #endif /* CONFIG_FAIR_GROUP_SCHED */
2714 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2717 * Unsigned subtract and clamp on underflow.
2719 * Explicitly do a load-store to ensure the intermediate value never hits
2720 * memory. This allows lockless observations without ever seeing the negative
2723 #define sub_positive(_ptr, _val) do { \
2724 typeof(_ptr) ptr = (_ptr); \
2725 typeof(*ptr) val = (_val); \
2726 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2730 WRITE_ONCE(*ptr, res); \
2733 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2734 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2736 struct sched_avg *sa = &cfs_rq->avg;
2737 int decayed, removed = 0;
2739 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2740 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2741 sub_positive(&sa->load_avg, r);
2742 sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
2746 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2747 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2748 sub_positive(&sa->util_avg, r);
2749 sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
2752 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2753 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2755 #ifndef CONFIG_64BIT
2757 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2760 /* Trace CPU load, unless cfs_rq belongs to a non-root task_group */
2761 if (cfs_rq == &rq_of(cfs_rq)->cfs)
2762 trace_sched_load_avg_cpu(cpu_of(rq_of(cfs_rq)), cfs_rq);
2764 return decayed || removed;
2767 /* Update task and its cfs_rq load average */
2768 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2770 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2771 u64 now = cfs_rq_clock_task(cfs_rq);
2772 int cpu = cpu_of(rq_of(cfs_rq));
2775 * Track task load average for carrying it to new CPU after migrated, and
2776 * track group sched_entity load average for task_h_load calc in migration
2778 __update_load_avg(now, cpu, &se->avg,
2779 se->on_rq * scale_load_down(se->load.weight),
2780 cfs_rq->curr == se, NULL);
2782 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2783 update_tg_load_avg(cfs_rq, 0);
2785 if (entity_is_task(se))
2786 trace_sched_load_avg_task(task_of(se), &se->avg);
2789 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2791 if (!sched_feat(ATTACH_AGE_LOAD))
2795 * If we got migrated (either between CPUs or between cgroups) we'll
2796 * have aged the average right before clearing @last_update_time.
2798 if (se->avg.last_update_time) {
2799 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2800 &se->avg, 0, 0, NULL);
2803 * XXX: we could have just aged the entire load away if we've been
2804 * absent from the fair class for too long.
2809 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2810 cfs_rq->avg.load_avg += se->avg.load_avg;
2811 cfs_rq->avg.load_sum += se->avg.load_sum;
2812 cfs_rq->avg.util_avg += se->avg.util_avg;
2813 cfs_rq->avg.util_sum += se->avg.util_sum;
2816 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2818 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2819 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2820 cfs_rq->curr == se, NULL);
2822 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
2823 sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
2824 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
2825 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
2828 /* Add the load generated by se into cfs_rq's load average */
2830 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2832 struct sched_avg *sa = &se->avg;
2833 u64 now = cfs_rq_clock_task(cfs_rq);
2834 int migrated, decayed;
2836 migrated = !sa->last_update_time;
2838 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2839 se->on_rq * scale_load_down(se->load.weight),
2840 cfs_rq->curr == se, NULL);
2843 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2845 cfs_rq->runnable_load_avg += sa->load_avg;
2846 cfs_rq->runnable_load_sum += sa->load_sum;
2849 attach_entity_load_avg(cfs_rq, se);
2851 if (decayed || migrated)
2852 update_tg_load_avg(cfs_rq, 0);
2855 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2857 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2859 update_load_avg(se, 1);
2861 cfs_rq->runnable_load_avg =
2862 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2863 cfs_rq->runnable_load_sum =
2864 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2867 #ifndef CONFIG_64BIT
2868 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2870 u64 last_update_time_copy;
2871 u64 last_update_time;
2874 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2876 last_update_time = cfs_rq->avg.last_update_time;
2877 } while (last_update_time != last_update_time_copy);
2879 return last_update_time;
2882 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2884 return cfs_rq->avg.last_update_time;
2889 * Task first catches up with cfs_rq, and then subtract
2890 * itself from the cfs_rq (task must be off the queue now).
2892 void remove_entity_load_avg(struct sched_entity *se)
2894 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2895 u64 last_update_time;
2898 * Newly created task or never used group entity should not be removed
2899 * from its (source) cfs_rq
2901 if (se->avg.last_update_time == 0)
2904 last_update_time = cfs_rq_last_update_time(cfs_rq);
2906 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2907 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2908 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2912 * Update the rq's load with the elapsed running time before entering
2913 * idle. if the last scheduled task is not a CFS task, idle_enter will
2914 * be the only way to update the runnable statistic.
2916 void idle_enter_fair(struct rq *this_rq)
2921 * Update the rq's load with the elapsed idle time before a task is
2922 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2923 * be the only way to update the runnable statistic.
2925 void idle_exit_fair(struct rq *this_rq)
2929 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2931 return cfs_rq->runnable_load_avg;
2934 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2936 return cfs_rq->avg.load_avg;
2939 static int idle_balance(struct rq *this_rq);
2941 #else /* CONFIG_SMP */
2943 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2945 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2947 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2948 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2951 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2953 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2955 static inline int idle_balance(struct rq *rq)
2960 #endif /* CONFIG_SMP */
2962 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2964 #ifdef CONFIG_SCHEDSTATS
2965 struct task_struct *tsk = NULL;
2967 if (entity_is_task(se))
2970 if (se->statistics.sleep_start) {
2971 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2976 if (unlikely(delta > se->statistics.sleep_max))
2977 se->statistics.sleep_max = delta;
2979 se->statistics.sleep_start = 0;
2980 se->statistics.sum_sleep_runtime += delta;
2983 account_scheduler_latency(tsk, delta >> 10, 1);
2984 trace_sched_stat_sleep(tsk, delta);
2987 if (se->statistics.block_start) {
2988 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2993 if (unlikely(delta > se->statistics.block_max))
2994 se->statistics.block_max = delta;
2996 se->statistics.block_start = 0;
2997 se->statistics.sum_sleep_runtime += delta;
3000 if (tsk->in_iowait) {
3001 se->statistics.iowait_sum += delta;
3002 se->statistics.iowait_count++;
3003 trace_sched_stat_iowait(tsk, delta);
3006 trace_sched_stat_blocked(tsk, delta);
3007 trace_sched_blocked_reason(tsk);
3010 * Blocking time is in units of nanosecs, so shift by
3011 * 20 to get a milliseconds-range estimation of the
3012 * amount of time that the task spent sleeping:
3014 if (unlikely(prof_on == SLEEP_PROFILING)) {
3015 profile_hits(SLEEP_PROFILING,
3016 (void *)get_wchan(tsk),
3019 account_scheduler_latency(tsk, delta >> 10, 0);
3025 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
3027 #ifdef CONFIG_SCHED_DEBUG
3028 s64 d = se->vruntime - cfs_rq->min_vruntime;
3033 if (d > 3*sysctl_sched_latency)
3034 schedstat_inc(cfs_rq, nr_spread_over);
3039 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3041 u64 vruntime = cfs_rq->min_vruntime;
3044 * The 'current' period is already promised to the current tasks,
3045 * however the extra weight of the new task will slow them down a
3046 * little, place the new task so that it fits in the slot that
3047 * stays open at the end.
3049 if (initial && sched_feat(START_DEBIT))
3050 vruntime += sched_vslice(cfs_rq, se);
3052 /* sleeps up to a single latency don't count. */
3054 unsigned long thresh = sysctl_sched_latency;
3057 * Halve their sleep time's effect, to allow
3058 * for a gentler effect of sleepers:
3060 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3066 /* ensure we never gain time by being placed backwards. */
3067 se->vruntime = max_vruntime(se->vruntime, vruntime);
3070 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3073 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3076 * Update the normalized vruntime before updating min_vruntime
3077 * through calling update_curr().
3079 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3080 se->vruntime += cfs_rq->min_vruntime;
3083 * Update run-time statistics of the 'current'.
3085 update_curr(cfs_rq);
3086 enqueue_entity_load_avg(cfs_rq, se);
3087 account_entity_enqueue(cfs_rq, se);
3088 update_cfs_shares(cfs_rq);
3090 if (flags & ENQUEUE_WAKEUP) {
3091 place_entity(cfs_rq, se, 0);
3092 enqueue_sleeper(cfs_rq, se);
3095 update_stats_enqueue(cfs_rq, se);
3096 check_spread(cfs_rq, se);
3097 if (se != cfs_rq->curr)
3098 __enqueue_entity(cfs_rq, se);
3101 if (cfs_rq->nr_running == 1) {
3102 list_add_leaf_cfs_rq(cfs_rq);
3103 check_enqueue_throttle(cfs_rq);
3107 static void __clear_buddies_last(struct sched_entity *se)
3109 for_each_sched_entity(se) {
3110 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3111 if (cfs_rq->last != se)
3114 cfs_rq->last = NULL;
3118 static void __clear_buddies_next(struct sched_entity *se)
3120 for_each_sched_entity(se) {
3121 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3122 if (cfs_rq->next != se)
3125 cfs_rq->next = NULL;
3129 static void __clear_buddies_skip(struct sched_entity *se)
3131 for_each_sched_entity(se) {
3132 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3133 if (cfs_rq->skip != se)
3136 cfs_rq->skip = NULL;
3140 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3142 if (cfs_rq->last == se)
3143 __clear_buddies_last(se);
3145 if (cfs_rq->next == se)
3146 __clear_buddies_next(se);
3148 if (cfs_rq->skip == se)
3149 __clear_buddies_skip(se);
3152 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3155 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3158 * Update run-time statistics of the 'current'.
3160 update_curr(cfs_rq);
3161 dequeue_entity_load_avg(cfs_rq, se);
3163 update_stats_dequeue(cfs_rq, se);
3164 if (flags & DEQUEUE_SLEEP) {
3165 #ifdef CONFIG_SCHEDSTATS
3166 if (entity_is_task(se)) {
3167 struct task_struct *tsk = task_of(se);
3169 if (tsk->state & TASK_INTERRUPTIBLE)
3170 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3171 if (tsk->state & TASK_UNINTERRUPTIBLE)
3172 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3177 clear_buddies(cfs_rq, se);
3179 if (se != cfs_rq->curr)
3180 __dequeue_entity(cfs_rq, se);
3182 account_entity_dequeue(cfs_rq, se);
3185 * Normalize the entity after updating the min_vruntime because the
3186 * update can refer to the ->curr item and we need to reflect this
3187 * movement in our normalized position.
3189 if (!(flags & DEQUEUE_SLEEP))
3190 se->vruntime -= cfs_rq->min_vruntime;
3192 /* return excess runtime on last dequeue */
3193 return_cfs_rq_runtime(cfs_rq);
3195 update_min_vruntime(cfs_rq);
3196 update_cfs_shares(cfs_rq);
3200 * Preempt the current task with a newly woken task if needed:
3203 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3205 unsigned long ideal_runtime, delta_exec;
3206 struct sched_entity *se;
3209 ideal_runtime = sched_slice(cfs_rq, curr);
3210 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3211 if (delta_exec > ideal_runtime) {
3212 resched_curr(rq_of(cfs_rq));
3214 * The current task ran long enough, ensure it doesn't get
3215 * re-elected due to buddy favours.
3217 clear_buddies(cfs_rq, curr);
3222 * Ensure that a task that missed wakeup preemption by a
3223 * narrow margin doesn't have to wait for a full slice.
3224 * This also mitigates buddy induced latencies under load.
3226 if (delta_exec < sysctl_sched_min_granularity)
3229 se = __pick_first_entity(cfs_rq);
3230 delta = curr->vruntime - se->vruntime;
3235 if (delta > ideal_runtime)
3236 resched_curr(rq_of(cfs_rq));
3240 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3242 /* 'current' is not kept within the tree. */
3245 * Any task has to be enqueued before it get to execute on
3246 * a CPU. So account for the time it spent waiting on the
3249 update_stats_wait_end(cfs_rq, se);
3250 __dequeue_entity(cfs_rq, se);
3251 update_load_avg(se, 1);
3254 update_stats_curr_start(cfs_rq, se);
3256 #ifdef CONFIG_SCHEDSTATS
3258 * Track our maximum slice length, if the CPU's load is at
3259 * least twice that of our own weight (i.e. dont track it
3260 * when there are only lesser-weight tasks around):
3262 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3263 se->statistics.slice_max = max(se->statistics.slice_max,
3264 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3267 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3271 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3274 * Pick the next process, keeping these things in mind, in this order:
3275 * 1) keep things fair between processes/task groups
3276 * 2) pick the "next" process, since someone really wants that to run
3277 * 3) pick the "last" process, for cache locality
3278 * 4) do not run the "skip" process, if something else is available
3280 static struct sched_entity *
3281 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3283 struct sched_entity *left = __pick_first_entity(cfs_rq);
3284 struct sched_entity *se;
3287 * If curr is set we have to see if its left of the leftmost entity
3288 * still in the tree, provided there was anything in the tree at all.
3290 if (!left || (curr && entity_before(curr, left)))
3293 se = left; /* ideally we run the leftmost entity */
3296 * Avoid running the skip buddy, if running something else can
3297 * be done without getting too unfair.
3299 if (cfs_rq->skip == se) {
3300 struct sched_entity *second;
3303 second = __pick_first_entity(cfs_rq);
3305 second = __pick_next_entity(se);
3306 if (!second || (curr && entity_before(curr, second)))
3310 if (second && wakeup_preempt_entity(second, left) < 1)
3315 * Prefer last buddy, try to return the CPU to a preempted task.
3317 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3321 * Someone really wants this to run. If it's not unfair, run it.
3323 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3326 clear_buddies(cfs_rq, se);
3331 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3333 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3336 * If still on the runqueue then deactivate_task()
3337 * was not called and update_curr() has to be done:
3340 update_curr(cfs_rq);
3342 /* throttle cfs_rqs exceeding runtime */
3343 check_cfs_rq_runtime(cfs_rq);
3345 check_spread(cfs_rq, prev);
3347 update_stats_wait_start(cfs_rq, prev);
3348 /* Put 'current' back into the tree. */
3349 __enqueue_entity(cfs_rq, prev);
3350 /* in !on_rq case, update occurred at dequeue */
3351 update_load_avg(prev, 0);
3353 cfs_rq->curr = NULL;
3357 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3360 * Update run-time statistics of the 'current'.
3362 update_curr(cfs_rq);
3365 * Ensure that runnable average is periodically updated.
3367 update_load_avg(curr, 1);
3368 update_cfs_shares(cfs_rq);
3370 #ifdef CONFIG_SCHED_HRTICK
3372 * queued ticks are scheduled to match the slice, so don't bother
3373 * validating it and just reschedule.
3376 resched_curr(rq_of(cfs_rq));
3380 * don't let the period tick interfere with the hrtick preemption
3382 if (!sched_feat(DOUBLE_TICK) &&
3383 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3387 if (cfs_rq->nr_running > 1)
3388 check_preempt_tick(cfs_rq, curr);
3392 /**************************************************
3393 * CFS bandwidth control machinery
3396 #ifdef CONFIG_CFS_BANDWIDTH
3398 #ifdef HAVE_JUMP_LABEL
3399 static struct static_key __cfs_bandwidth_used;
3401 static inline bool cfs_bandwidth_used(void)
3403 return static_key_false(&__cfs_bandwidth_used);
3406 void cfs_bandwidth_usage_inc(void)
3408 static_key_slow_inc(&__cfs_bandwidth_used);
3411 void cfs_bandwidth_usage_dec(void)
3413 static_key_slow_dec(&__cfs_bandwidth_used);
3415 #else /* HAVE_JUMP_LABEL */
3416 static bool cfs_bandwidth_used(void)
3421 void cfs_bandwidth_usage_inc(void) {}
3422 void cfs_bandwidth_usage_dec(void) {}
3423 #endif /* HAVE_JUMP_LABEL */
3426 * default period for cfs group bandwidth.
3427 * default: 0.1s, units: nanoseconds
3429 static inline u64 default_cfs_period(void)
3431 return 100000000ULL;
3434 static inline u64 sched_cfs_bandwidth_slice(void)
3436 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3440 * Replenish runtime according to assigned quota and update expiration time.
3441 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3442 * additional synchronization around rq->lock.
3444 * requires cfs_b->lock
3446 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3450 if (cfs_b->quota == RUNTIME_INF)
3453 now = sched_clock_cpu(smp_processor_id());
3454 cfs_b->runtime = cfs_b->quota;
3455 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3458 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3460 return &tg->cfs_bandwidth;
3463 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3464 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3466 if (unlikely(cfs_rq->throttle_count))
3467 return cfs_rq->throttled_clock_task;
3469 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3472 /* returns 0 on failure to allocate runtime */
3473 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3475 struct task_group *tg = cfs_rq->tg;
3476 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3477 u64 amount = 0, min_amount, expires;
3479 /* note: this is a positive sum as runtime_remaining <= 0 */
3480 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3482 raw_spin_lock(&cfs_b->lock);
3483 if (cfs_b->quota == RUNTIME_INF)
3484 amount = min_amount;
3486 start_cfs_bandwidth(cfs_b);
3488 if (cfs_b->runtime > 0) {
3489 amount = min(cfs_b->runtime, min_amount);
3490 cfs_b->runtime -= amount;
3494 expires = cfs_b->runtime_expires;
3495 raw_spin_unlock(&cfs_b->lock);
3497 cfs_rq->runtime_remaining += amount;
3499 * we may have advanced our local expiration to account for allowed
3500 * spread between our sched_clock and the one on which runtime was
3503 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3504 cfs_rq->runtime_expires = expires;
3506 return cfs_rq->runtime_remaining > 0;
3510 * Note: This depends on the synchronization provided by sched_clock and the
3511 * fact that rq->clock snapshots this value.
3513 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3515 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3517 /* if the deadline is ahead of our clock, nothing to do */
3518 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3521 if (cfs_rq->runtime_remaining < 0)
3525 * If the local deadline has passed we have to consider the
3526 * possibility that our sched_clock is 'fast' and the global deadline
3527 * has not truly expired.
3529 * Fortunately we can check determine whether this the case by checking
3530 * whether the global deadline has advanced. It is valid to compare
3531 * cfs_b->runtime_expires without any locks since we only care about
3532 * exact equality, so a partial write will still work.
3535 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3536 /* extend local deadline, drift is bounded above by 2 ticks */
3537 cfs_rq->runtime_expires += TICK_NSEC;
3539 /* global deadline is ahead, expiration has passed */
3540 cfs_rq->runtime_remaining = 0;
3544 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3546 /* dock delta_exec before expiring quota (as it could span periods) */
3547 cfs_rq->runtime_remaining -= delta_exec;
3548 expire_cfs_rq_runtime(cfs_rq);
3550 if (likely(cfs_rq->runtime_remaining > 0))
3554 * if we're unable to extend our runtime we resched so that the active
3555 * hierarchy can be throttled
3557 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3558 resched_curr(rq_of(cfs_rq));
3561 static __always_inline
3562 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3564 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3567 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3570 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3572 return cfs_bandwidth_used() && cfs_rq->throttled;
3575 /* check whether cfs_rq, or any parent, is throttled */
3576 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3578 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3582 * Ensure that neither of the group entities corresponding to src_cpu or
3583 * dest_cpu are members of a throttled hierarchy when performing group
3584 * load-balance operations.
3586 static inline int throttled_lb_pair(struct task_group *tg,
3587 int src_cpu, int dest_cpu)
3589 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3591 src_cfs_rq = tg->cfs_rq[src_cpu];
3592 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3594 return throttled_hierarchy(src_cfs_rq) ||
3595 throttled_hierarchy(dest_cfs_rq);
3598 /* updated child weight may affect parent so we have to do this bottom up */
3599 static int tg_unthrottle_up(struct task_group *tg, void *data)
3601 struct rq *rq = data;
3602 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3604 cfs_rq->throttle_count--;
3606 if (!cfs_rq->throttle_count) {
3607 /* adjust cfs_rq_clock_task() */
3608 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3609 cfs_rq->throttled_clock_task;
3616 static int tg_throttle_down(struct task_group *tg, void *data)
3618 struct rq *rq = data;
3619 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3621 /* group is entering throttled state, stop time */
3622 if (!cfs_rq->throttle_count)
3623 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3624 cfs_rq->throttle_count++;
3629 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3631 struct rq *rq = rq_of(cfs_rq);
3632 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3633 struct sched_entity *se;
3634 long task_delta, dequeue = 1;
3637 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3639 /* freeze hierarchy runnable averages while throttled */
3641 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3644 task_delta = cfs_rq->h_nr_running;
3645 for_each_sched_entity(se) {
3646 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3647 /* throttled entity or throttle-on-deactivate */
3652 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3653 qcfs_rq->h_nr_running -= task_delta;
3655 if (qcfs_rq->load.weight)
3660 sub_nr_running(rq, task_delta);
3662 cfs_rq->throttled = 1;
3663 cfs_rq->throttled_clock = rq_clock(rq);
3664 raw_spin_lock(&cfs_b->lock);
3665 empty = list_empty(&cfs_b->throttled_cfs_rq);
3668 * Add to the _head_ of the list, so that an already-started
3669 * distribute_cfs_runtime will not see us
3671 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3674 * If we're the first throttled task, make sure the bandwidth
3678 start_cfs_bandwidth(cfs_b);
3680 raw_spin_unlock(&cfs_b->lock);
3683 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3685 struct rq *rq = rq_of(cfs_rq);
3686 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3687 struct sched_entity *se;
3691 se = cfs_rq->tg->se[cpu_of(rq)];
3693 cfs_rq->throttled = 0;
3695 update_rq_clock(rq);
3697 raw_spin_lock(&cfs_b->lock);
3698 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3699 list_del_rcu(&cfs_rq->throttled_list);
3700 raw_spin_unlock(&cfs_b->lock);
3702 /* update hierarchical throttle state */
3703 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3705 if (!cfs_rq->load.weight)
3708 task_delta = cfs_rq->h_nr_running;
3709 for_each_sched_entity(se) {
3713 cfs_rq = cfs_rq_of(se);
3715 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3716 cfs_rq->h_nr_running += task_delta;
3718 if (cfs_rq_throttled(cfs_rq))
3723 add_nr_running(rq, task_delta);
3725 /* determine whether we need to wake up potentially idle cpu */
3726 if (rq->curr == rq->idle && rq->cfs.nr_running)
3730 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3731 u64 remaining, u64 expires)
3733 struct cfs_rq *cfs_rq;
3735 u64 starting_runtime = remaining;
3738 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3740 struct rq *rq = rq_of(cfs_rq);
3742 raw_spin_lock(&rq->lock);
3743 if (!cfs_rq_throttled(cfs_rq))
3746 runtime = -cfs_rq->runtime_remaining + 1;
3747 if (runtime > remaining)
3748 runtime = remaining;
3749 remaining -= runtime;
3751 cfs_rq->runtime_remaining += runtime;
3752 cfs_rq->runtime_expires = expires;
3754 /* we check whether we're throttled above */
3755 if (cfs_rq->runtime_remaining > 0)
3756 unthrottle_cfs_rq(cfs_rq);
3759 raw_spin_unlock(&rq->lock);
3766 return starting_runtime - remaining;
3770 * Responsible for refilling a task_group's bandwidth and unthrottling its
3771 * cfs_rqs as appropriate. If there has been no activity within the last
3772 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3773 * used to track this state.
3775 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3777 u64 runtime, runtime_expires;
3780 /* no need to continue the timer with no bandwidth constraint */
3781 if (cfs_b->quota == RUNTIME_INF)
3782 goto out_deactivate;
3784 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3785 cfs_b->nr_periods += overrun;
3788 * idle depends on !throttled (for the case of a large deficit), and if
3789 * we're going inactive then everything else can be deferred
3791 if (cfs_b->idle && !throttled)
3792 goto out_deactivate;
3794 __refill_cfs_bandwidth_runtime(cfs_b);
3797 /* mark as potentially idle for the upcoming period */
3802 /* account preceding periods in which throttling occurred */
3803 cfs_b->nr_throttled += overrun;
3805 runtime_expires = cfs_b->runtime_expires;
3808 * This check is repeated as we are holding onto the new bandwidth while
3809 * we unthrottle. This can potentially race with an unthrottled group
3810 * trying to acquire new bandwidth from the global pool. This can result
3811 * in us over-using our runtime if it is all used during this loop, but
3812 * only by limited amounts in that extreme case.
3814 while (throttled && cfs_b->runtime > 0) {
3815 runtime = cfs_b->runtime;
3816 raw_spin_unlock(&cfs_b->lock);
3817 /* we can't nest cfs_b->lock while distributing bandwidth */
3818 runtime = distribute_cfs_runtime(cfs_b, runtime,
3820 raw_spin_lock(&cfs_b->lock);
3822 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3824 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3828 * While we are ensured activity in the period following an
3829 * unthrottle, this also covers the case in which the new bandwidth is
3830 * insufficient to cover the existing bandwidth deficit. (Forcing the
3831 * timer to remain active while there are any throttled entities.)
3841 /* a cfs_rq won't donate quota below this amount */
3842 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3843 /* minimum remaining period time to redistribute slack quota */
3844 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3845 /* how long we wait to gather additional slack before distributing */
3846 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3849 * Are we near the end of the current quota period?
3851 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3852 * hrtimer base being cleared by hrtimer_start. In the case of
3853 * migrate_hrtimers, base is never cleared, so we are fine.
3855 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3857 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3860 /* if the call-back is running a quota refresh is already occurring */
3861 if (hrtimer_callback_running(refresh_timer))
3864 /* is a quota refresh about to occur? */
3865 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3866 if (remaining < min_expire)
3872 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3874 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3876 /* if there's a quota refresh soon don't bother with slack */
3877 if (runtime_refresh_within(cfs_b, min_left))
3880 hrtimer_start(&cfs_b->slack_timer,
3881 ns_to_ktime(cfs_bandwidth_slack_period),
3885 /* we know any runtime found here is valid as update_curr() precedes return */
3886 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3888 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3889 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3891 if (slack_runtime <= 0)
3894 raw_spin_lock(&cfs_b->lock);
3895 if (cfs_b->quota != RUNTIME_INF &&
3896 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3897 cfs_b->runtime += slack_runtime;
3899 /* we are under rq->lock, defer unthrottling using a timer */
3900 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3901 !list_empty(&cfs_b->throttled_cfs_rq))
3902 start_cfs_slack_bandwidth(cfs_b);
3904 raw_spin_unlock(&cfs_b->lock);
3906 /* even if it's not valid for return we don't want to try again */
3907 cfs_rq->runtime_remaining -= slack_runtime;
3910 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3912 if (!cfs_bandwidth_used())
3915 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3918 __return_cfs_rq_runtime(cfs_rq);
3922 * This is done with a timer (instead of inline with bandwidth return) since
3923 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3925 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3927 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3930 /* confirm we're still not at a refresh boundary */
3931 raw_spin_lock(&cfs_b->lock);
3932 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3933 raw_spin_unlock(&cfs_b->lock);
3937 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3938 runtime = cfs_b->runtime;
3940 expires = cfs_b->runtime_expires;
3941 raw_spin_unlock(&cfs_b->lock);
3946 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3948 raw_spin_lock(&cfs_b->lock);
3949 if (expires == cfs_b->runtime_expires)
3950 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3951 raw_spin_unlock(&cfs_b->lock);
3955 * When a group wakes up we want to make sure that its quota is not already
3956 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3957 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3959 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3961 if (!cfs_bandwidth_used())
3964 /* Synchronize hierarchical throttle counter: */
3965 if (unlikely(!cfs_rq->throttle_uptodate)) {
3966 struct rq *rq = rq_of(cfs_rq);
3967 struct cfs_rq *pcfs_rq;
3968 struct task_group *tg;
3970 cfs_rq->throttle_uptodate = 1;
3972 /* Get closest up-to-date node, because leaves go first: */
3973 for (tg = cfs_rq->tg->parent; tg; tg = tg->parent) {
3974 pcfs_rq = tg->cfs_rq[cpu_of(rq)];
3975 if (pcfs_rq->throttle_uptodate)
3979 cfs_rq->throttle_count = pcfs_rq->throttle_count;
3980 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3984 /* an active group must be handled by the update_curr()->put() path */
3985 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3988 /* ensure the group is not already throttled */
3989 if (cfs_rq_throttled(cfs_rq))
3992 /* update runtime allocation */
3993 account_cfs_rq_runtime(cfs_rq, 0);
3994 if (cfs_rq->runtime_remaining <= 0)
3995 throttle_cfs_rq(cfs_rq);
3998 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3999 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4001 if (!cfs_bandwidth_used())
4004 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4008 * it's possible for a throttled entity to be forced into a running
4009 * state (e.g. set_curr_task), in this case we're finished.
4011 if (cfs_rq_throttled(cfs_rq))
4014 throttle_cfs_rq(cfs_rq);
4018 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
4020 struct cfs_bandwidth *cfs_b =
4021 container_of(timer, struct cfs_bandwidth, slack_timer);
4023 do_sched_cfs_slack_timer(cfs_b);
4025 return HRTIMER_NORESTART;
4028 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
4030 struct cfs_bandwidth *cfs_b =
4031 container_of(timer, struct cfs_bandwidth, period_timer);
4035 raw_spin_lock(&cfs_b->lock);
4037 overrun = hrtimer_forward_now(timer, cfs_b->period);
4041 idle = do_sched_cfs_period_timer(cfs_b, overrun);
4044 cfs_b->period_active = 0;
4045 raw_spin_unlock(&cfs_b->lock);
4047 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
4050 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4052 raw_spin_lock_init(&cfs_b->lock);
4054 cfs_b->quota = RUNTIME_INF;
4055 cfs_b->period = ns_to_ktime(default_cfs_period());
4057 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4058 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4059 cfs_b->period_timer.function = sched_cfs_period_timer;
4060 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4061 cfs_b->slack_timer.function = sched_cfs_slack_timer;
4064 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4066 cfs_rq->runtime_enabled = 0;
4067 INIT_LIST_HEAD(&cfs_rq->throttled_list);
4070 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4072 lockdep_assert_held(&cfs_b->lock);
4074 if (!cfs_b->period_active) {
4075 cfs_b->period_active = 1;
4076 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4077 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4081 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4083 /* init_cfs_bandwidth() was not called */
4084 if (!cfs_b->throttled_cfs_rq.next)
4087 hrtimer_cancel(&cfs_b->period_timer);
4088 hrtimer_cancel(&cfs_b->slack_timer);
4091 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4093 struct cfs_rq *cfs_rq;
4095 for_each_leaf_cfs_rq(rq, cfs_rq) {
4096 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4098 raw_spin_lock(&cfs_b->lock);
4099 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4100 raw_spin_unlock(&cfs_b->lock);
4104 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4106 struct cfs_rq *cfs_rq;
4108 for_each_leaf_cfs_rq(rq, cfs_rq) {
4109 if (!cfs_rq->runtime_enabled)
4113 * clock_task is not advancing so we just need to make sure
4114 * there's some valid quota amount
4116 cfs_rq->runtime_remaining = 1;
4118 * Offline rq is schedulable till cpu is completely disabled
4119 * in take_cpu_down(), so we prevent new cfs throttling here.
4121 cfs_rq->runtime_enabled = 0;
4123 if (cfs_rq_throttled(cfs_rq))
4124 unthrottle_cfs_rq(cfs_rq);
4128 #else /* CONFIG_CFS_BANDWIDTH */
4129 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4131 return rq_clock_task(rq_of(cfs_rq));
4134 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4135 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4136 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4137 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4139 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4144 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4149 static inline int throttled_lb_pair(struct task_group *tg,
4150 int src_cpu, int dest_cpu)
4155 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4157 #ifdef CONFIG_FAIR_GROUP_SCHED
4158 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4161 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4165 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4166 static inline void update_runtime_enabled(struct rq *rq) {}
4167 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4169 #endif /* CONFIG_CFS_BANDWIDTH */
4171 /**************************************************
4172 * CFS operations on tasks:
4175 #ifdef CONFIG_SCHED_HRTICK
4176 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4178 struct sched_entity *se = &p->se;
4179 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4181 WARN_ON(task_rq(p) != rq);
4183 if (cfs_rq->nr_running > 1) {
4184 u64 slice = sched_slice(cfs_rq, se);
4185 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4186 s64 delta = slice - ran;
4193 hrtick_start(rq, delta);
4198 * called from enqueue/dequeue and updates the hrtick when the
4199 * current task is from our class and nr_running is low enough
4202 static void hrtick_update(struct rq *rq)
4204 struct task_struct *curr = rq->curr;
4206 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4209 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4210 hrtick_start_fair(rq, curr);
4212 #else /* !CONFIG_SCHED_HRTICK */
4214 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4218 static inline void hrtick_update(struct rq *rq)
4224 static bool cpu_overutilized(int cpu);
4225 static inline unsigned long boosted_cpu_util(int cpu);
4227 #define boosted_cpu_util(cpu) cpu_util(cpu)
4231 static void update_capacity_of(int cpu)
4233 unsigned long req_cap;
4238 /* Convert scale-invariant capacity to cpu. */
4239 req_cap = boosted_cpu_util(cpu);
4240 req_cap = req_cap * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
4241 set_cfs_cpu_capacity(cpu, true, req_cap);
4246 * The enqueue_task method is called before nr_running is
4247 * increased. Here we update the fair scheduling stats and
4248 * then put the task into the rbtree:
4251 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4253 struct cfs_rq *cfs_rq;
4254 struct sched_entity *se = &p->se;
4256 int task_new = flags & ENQUEUE_WAKEUP_NEW;
4257 int task_wakeup = flags & ENQUEUE_WAKEUP;
4260 for_each_sched_entity(se) {
4263 cfs_rq = cfs_rq_of(se);
4264 enqueue_entity(cfs_rq, se, flags);
4267 * end evaluation on encountering a throttled cfs_rq
4269 * note: in the case of encountering a throttled cfs_rq we will
4270 * post the final h_nr_running increment below.
4272 if (cfs_rq_throttled(cfs_rq))
4274 cfs_rq->h_nr_running++;
4275 walt_inc_cfs_cumulative_runnable_avg(cfs_rq, p);
4277 flags = ENQUEUE_WAKEUP;
4280 for_each_sched_entity(se) {
4281 cfs_rq = cfs_rq_of(se);
4282 cfs_rq->h_nr_running++;
4283 walt_inc_cfs_cumulative_runnable_avg(cfs_rq, p);
4285 if (cfs_rq_throttled(cfs_rq))
4288 update_load_avg(se, 1);
4289 update_cfs_shares(cfs_rq);
4293 add_nr_running(rq, 1);
4298 * Update SchedTune accounting.
4300 * We do it before updating the CPU capacity to ensure the
4301 * boost value of the current task is accounted for in the
4302 * selection of the OPP.
4304 * We do it also in the case where we enqueue a throttled task;
4305 * we could argue that a throttled task should not boost a CPU,
4307 * a) properly implementing CPU boosting considering throttled
4308 * tasks will increase a lot the complexity of the solution
4309 * b) it's not easy to quantify the benefits introduced by
4310 * such a more complex solution.
4311 * Thus, for the time being we go for the simple solution and boost
4312 * also for throttled RQs.
4314 schedtune_enqueue_task(p, cpu_of(rq));
4317 walt_inc_cumulative_runnable_avg(rq, p);
4318 if (!task_new && !rq->rd->overutilized &&
4319 cpu_overutilized(rq->cpu)) {
4320 rq->rd->overutilized = true;
4321 trace_sched_overutilized(true);
4325 * We want to potentially trigger a freq switch
4326 * request only for tasks that are waking up; this is
4327 * because we get here also during load balancing, but
4328 * in these cases it seems wise to trigger as single
4329 * request after load balancing is done.
4331 if (task_new || task_wakeup)
4332 update_capacity_of(cpu_of(rq));
4335 #endif /* CONFIG_SMP */
4339 static void set_next_buddy(struct sched_entity *se);
4342 * The dequeue_task method is called before nr_running is
4343 * decreased. We remove the task from the rbtree and
4344 * update the fair scheduling stats:
4346 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4348 struct cfs_rq *cfs_rq;
4349 struct sched_entity *se = &p->se;
4350 int task_sleep = flags & DEQUEUE_SLEEP;
4352 for_each_sched_entity(se) {
4353 cfs_rq = cfs_rq_of(se);
4354 dequeue_entity(cfs_rq, se, flags);
4357 * end evaluation on encountering a throttled cfs_rq
4359 * note: in the case of encountering a throttled cfs_rq we will
4360 * post the final h_nr_running decrement below.
4362 if (cfs_rq_throttled(cfs_rq))
4364 cfs_rq->h_nr_running--;
4365 walt_dec_cfs_cumulative_runnable_avg(cfs_rq, p);
4367 /* Don't dequeue parent if it has other entities besides us */
4368 if (cfs_rq->load.weight) {
4369 /* Avoid re-evaluating load for this entity: */
4370 se = parent_entity(se);
4372 * Bias pick_next to pick a task from this cfs_rq, as
4373 * p is sleeping when it is within its sched_slice.
4375 if (task_sleep && se && !throttled_hierarchy(cfs_rq))
4379 flags |= DEQUEUE_SLEEP;
4382 for_each_sched_entity(se) {
4383 cfs_rq = cfs_rq_of(se);
4384 cfs_rq->h_nr_running--;
4385 walt_dec_cfs_cumulative_runnable_avg(cfs_rq, p);
4387 if (cfs_rq_throttled(cfs_rq))
4390 update_load_avg(se, 1);
4391 update_cfs_shares(cfs_rq);
4395 sub_nr_running(rq, 1);
4400 * Update SchedTune accounting
4402 * We do it before updating the CPU capacity to ensure the
4403 * boost value of the current task is accounted for in the
4404 * selection of the OPP.
4406 schedtune_dequeue_task(p, cpu_of(rq));
4409 walt_dec_cumulative_runnable_avg(rq, p);
4412 * We want to potentially trigger a freq switch
4413 * request only for tasks that are going to sleep;
4414 * this is because we get here also during load
4415 * balancing, but in these cases it seems wise to
4416 * trigger as single request after load balancing is
4420 if (rq->cfs.nr_running)
4421 update_capacity_of(cpu_of(rq));
4422 else if (sched_freq())
4423 set_cfs_cpu_capacity(cpu_of(rq), false, 0);
4427 #endif /* CONFIG_SMP */
4435 * per rq 'load' arrray crap; XXX kill this.
4439 * The exact cpuload at various idx values, calculated at every tick would be
4440 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4442 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4443 * on nth tick when cpu may be busy, then we have:
4444 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4445 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4447 * decay_load_missed() below does efficient calculation of
4448 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4449 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4451 * The calculation is approximated on a 128 point scale.
4452 * degrade_zero_ticks is the number of ticks after which load at any
4453 * particular idx is approximated to be zero.
4454 * degrade_factor is a precomputed table, a row for each load idx.
4455 * Each column corresponds to degradation factor for a power of two ticks,
4456 * based on 128 point scale.
4458 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4459 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4461 * With this power of 2 load factors, we can degrade the load n times
4462 * by looking at 1 bits in n and doing as many mult/shift instead of
4463 * n mult/shifts needed by the exact degradation.
4465 #define DEGRADE_SHIFT 7
4466 static const unsigned char
4467 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4468 static const unsigned char
4469 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4470 {0, 0, 0, 0, 0, 0, 0, 0},
4471 {64, 32, 8, 0, 0, 0, 0, 0},
4472 {96, 72, 40, 12, 1, 0, 0},
4473 {112, 98, 75, 43, 15, 1, 0},
4474 {120, 112, 98, 76, 45, 16, 2} };
4477 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4478 * would be when CPU is idle and so we just decay the old load without
4479 * adding any new load.
4481 static unsigned long
4482 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4486 if (!missed_updates)
4489 if (missed_updates >= degrade_zero_ticks[idx])
4493 return load >> missed_updates;
4495 while (missed_updates) {
4496 if (missed_updates % 2)
4497 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4499 missed_updates >>= 1;
4506 * Update rq->cpu_load[] statistics. This function is usually called every
4507 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4508 * every tick. We fix it up based on jiffies.
4510 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4511 unsigned long pending_updates)
4515 this_rq->nr_load_updates++;
4517 /* Update our load: */
4518 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4519 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4520 unsigned long old_load, new_load;
4522 /* scale is effectively 1 << i now, and >> i divides by scale */
4524 old_load = this_rq->cpu_load[i];
4525 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4526 new_load = this_load;
4528 * Round up the averaging division if load is increasing. This
4529 * prevents us from getting stuck on 9 if the load is 10, for
4532 if (new_load > old_load)
4533 new_load += scale - 1;
4535 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4538 sched_avg_update(this_rq);
4541 /* Used instead of source_load when we know the type == 0 */
4542 static unsigned long weighted_cpuload(const int cpu)
4544 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4547 #ifdef CONFIG_NO_HZ_COMMON
4549 * There is no sane way to deal with nohz on smp when using jiffies because the
4550 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4551 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4553 * Therefore we cannot use the delta approach from the regular tick since that
4554 * would seriously skew the load calculation. However we'll make do for those
4555 * updates happening while idle (nohz_idle_balance) or coming out of idle
4556 * (tick_nohz_idle_exit).
4558 * This means we might still be one tick off for nohz periods.
4562 * Called from nohz_idle_balance() to update the load ratings before doing the
4565 static void update_idle_cpu_load(struct rq *this_rq)
4567 unsigned long curr_jiffies = READ_ONCE(jiffies);
4568 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4569 unsigned long pending_updates;
4572 * bail if there's load or we're actually up-to-date.
4574 if (load || curr_jiffies == this_rq->last_load_update_tick)
4577 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4578 this_rq->last_load_update_tick = curr_jiffies;
4580 __update_cpu_load(this_rq, load, pending_updates);
4584 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4586 void update_cpu_load_nohz(void)
4588 struct rq *this_rq = this_rq();
4589 unsigned long curr_jiffies = READ_ONCE(jiffies);
4590 unsigned long pending_updates;
4592 if (curr_jiffies == this_rq->last_load_update_tick)
4595 raw_spin_lock(&this_rq->lock);
4596 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4597 if (pending_updates) {
4598 this_rq->last_load_update_tick = curr_jiffies;
4600 * We were idle, this means load 0, the current load might be
4601 * !0 due to remote wakeups and the sort.
4603 __update_cpu_load(this_rq, 0, pending_updates);
4605 raw_spin_unlock(&this_rq->lock);
4607 #endif /* CONFIG_NO_HZ */
4610 * Called from scheduler_tick()
4612 void update_cpu_load_active(struct rq *this_rq)
4614 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4616 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4618 this_rq->last_load_update_tick = jiffies;
4619 __update_cpu_load(this_rq, load, 1);
4623 * Return a low guess at the load of a migration-source cpu weighted
4624 * according to the scheduling class and "nice" value.
4626 * We want to under-estimate the load of migration sources, to
4627 * balance conservatively.
4629 static unsigned long source_load(int cpu, int type)
4631 struct rq *rq = cpu_rq(cpu);
4632 unsigned long total = weighted_cpuload(cpu);
4634 if (type == 0 || !sched_feat(LB_BIAS))
4637 return min(rq->cpu_load[type-1], total);
4641 * Return a high guess at the load of a migration-target cpu weighted
4642 * according to the scheduling class and "nice" value.
4644 static unsigned long target_load(int cpu, int type)
4646 struct rq *rq = cpu_rq(cpu);
4647 unsigned long total = weighted_cpuload(cpu);
4649 if (type == 0 || !sched_feat(LB_BIAS))
4652 return max(rq->cpu_load[type-1], total);
4656 static unsigned long cpu_avg_load_per_task(int cpu)
4658 struct rq *rq = cpu_rq(cpu);
4659 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4660 unsigned long load_avg = weighted_cpuload(cpu);
4663 return load_avg / nr_running;
4668 static void record_wakee(struct task_struct *p)
4671 * Rough decay (wiping) for cost saving, don't worry
4672 * about the boundary, really active task won't care
4675 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4676 current->wakee_flips >>= 1;
4677 current->wakee_flip_decay_ts = jiffies;
4680 if (current->last_wakee != p) {
4681 current->last_wakee = p;
4682 current->wakee_flips++;
4686 static void task_waking_fair(struct task_struct *p)
4688 struct sched_entity *se = &p->se;
4689 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4692 #ifndef CONFIG_64BIT
4693 u64 min_vruntime_copy;
4696 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4698 min_vruntime = cfs_rq->min_vruntime;
4699 } while (min_vruntime != min_vruntime_copy);
4701 min_vruntime = cfs_rq->min_vruntime;
4704 se->vruntime -= min_vruntime;
4708 #ifdef CONFIG_FAIR_GROUP_SCHED
4710 * effective_load() calculates the load change as seen from the root_task_group
4712 * Adding load to a group doesn't make a group heavier, but can cause movement
4713 * of group shares between cpus. Assuming the shares were perfectly aligned one
4714 * can calculate the shift in shares.
4716 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4717 * on this @cpu and results in a total addition (subtraction) of @wg to the
4718 * total group weight.
4720 * Given a runqueue weight distribution (rw_i) we can compute a shares
4721 * distribution (s_i) using:
4723 * s_i = rw_i / \Sum rw_j (1)
4725 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4726 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4727 * shares distribution (s_i):
4729 * rw_i = { 2, 4, 1, 0 }
4730 * s_i = { 2/7, 4/7, 1/7, 0 }
4732 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4733 * task used to run on and the CPU the waker is running on), we need to
4734 * compute the effect of waking a task on either CPU and, in case of a sync
4735 * wakeup, compute the effect of the current task going to sleep.
4737 * So for a change of @wl to the local @cpu with an overall group weight change
4738 * of @wl we can compute the new shares distribution (s'_i) using:
4740 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4742 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4743 * differences in waking a task to CPU 0. The additional task changes the
4744 * weight and shares distributions like:
4746 * rw'_i = { 3, 4, 1, 0 }
4747 * s'_i = { 3/8, 4/8, 1/8, 0 }
4749 * We can then compute the difference in effective weight by using:
4751 * dw_i = S * (s'_i - s_i) (3)
4753 * Where 'S' is the group weight as seen by its parent.
4755 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4756 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4757 * 4/7) times the weight of the group.
4759 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4761 struct sched_entity *se = tg->se[cpu];
4763 if (!tg->parent) /* the trivial, non-cgroup case */
4766 for_each_sched_entity(se) {
4767 struct cfs_rq *cfs_rq = se->my_q;
4768 long W, w = cfs_rq_load_avg(cfs_rq);
4773 * W = @wg + \Sum rw_j
4775 W = wg + atomic_long_read(&tg->load_avg);
4777 /* Ensure \Sum rw_j >= rw_i */
4778 W -= cfs_rq->tg_load_avg_contrib;
4787 * wl = S * s'_i; see (2)
4790 wl = (w * (long)tg->shares) / W;
4795 * Per the above, wl is the new se->load.weight value; since
4796 * those are clipped to [MIN_SHARES, ...) do so now. See
4797 * calc_cfs_shares().
4799 if (wl < MIN_SHARES)
4803 * wl = dw_i = S * (s'_i - s_i); see (3)
4805 wl -= se->avg.load_avg;
4808 * Recursively apply this logic to all parent groups to compute
4809 * the final effective load change on the root group. Since
4810 * only the @tg group gets extra weight, all parent groups can
4811 * only redistribute existing shares. @wl is the shift in shares
4812 * resulting from this level per the above.
4821 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4829 * Returns the current capacity of cpu after applying both
4830 * cpu and freq scaling.
4832 unsigned long capacity_curr_of(int cpu)
4834 return cpu_rq(cpu)->cpu_capacity_orig *
4835 arch_scale_freq_capacity(NULL, cpu)
4836 >> SCHED_CAPACITY_SHIFT;
4839 static inline bool energy_aware(void)
4841 return sched_feat(ENERGY_AWARE);
4845 struct sched_group *sg_top;
4846 struct sched_group *sg_cap;
4853 struct task_struct *task;
4868 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4869 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4870 * energy calculations. Using the scale-invariant util returned by
4871 * cpu_util() and approximating scale-invariant util by:
4873 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4875 * the normalized util can be found using the specific capacity.
4877 * capacity = capacity_orig * curr_freq/max_freq
4879 * norm_util = running_time/time ~ util/capacity
4881 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4883 int util = __cpu_util(cpu, delta);
4885 if (util >= capacity)
4886 return SCHED_CAPACITY_SCALE;
4888 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4891 static int calc_util_delta(struct energy_env *eenv, int cpu)
4893 if (cpu == eenv->src_cpu)
4894 return -eenv->util_delta;
4895 if (cpu == eenv->dst_cpu)
4896 return eenv->util_delta;
4901 unsigned long group_max_util(struct energy_env *eenv)
4904 unsigned long max_util = 0;
4906 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4907 delta = calc_util_delta(eenv, i);
4908 max_util = max(max_util, __cpu_util(i, delta));
4915 * group_norm_util() returns the approximated group util relative to it's
4916 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4917 * energy calculations. Since task executions may or may not overlap in time in
4918 * the group the true normalized util is between max(cpu_norm_util(i)) and
4919 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4920 * latter is used as the estimate as it leads to a more pessimistic energy
4921 * estimate (more busy).
4924 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4927 unsigned long util_sum = 0;
4928 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4930 for_each_cpu(i, sched_group_cpus(sg)) {
4931 delta = calc_util_delta(eenv, i);
4932 util_sum += __cpu_norm_util(i, capacity, delta);
4935 if (util_sum > SCHED_CAPACITY_SCALE)
4936 return SCHED_CAPACITY_SCALE;
4940 static int find_new_capacity(struct energy_env *eenv,
4941 const struct sched_group_energy * const sge)
4944 unsigned long util = group_max_util(eenv);
4946 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4947 if (sge->cap_states[idx].cap >= util)
4951 eenv->cap_idx = idx;
4956 static int group_idle_state(struct sched_group *sg)
4958 int i, state = INT_MAX;
4960 /* Find the shallowest idle state in the sched group. */
4961 for_each_cpu(i, sched_group_cpus(sg))
4962 state = min(state, idle_get_state_idx(cpu_rq(i)));
4964 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4971 * sched_group_energy(): Computes the absolute energy consumption of cpus
4972 * belonging to the sched_group including shared resources shared only by
4973 * members of the group. Iterates over all cpus in the hierarchy below the
4974 * sched_group starting from the bottom working it's way up before going to
4975 * the next cpu until all cpus are covered at all levels. The current
4976 * implementation is likely to gather the same util statistics multiple times.
4977 * This can probably be done in a faster but more complex way.
4978 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4980 static int sched_group_energy(struct energy_env *eenv)
4982 struct sched_domain *sd;
4983 int cpu, total_energy = 0;
4984 struct cpumask visit_cpus;
4985 struct sched_group *sg;
4987 WARN_ON(!eenv->sg_top->sge);
4989 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4991 while (!cpumask_empty(&visit_cpus)) {
4992 struct sched_group *sg_shared_cap = NULL;
4994 cpu = cpumask_first(&visit_cpus);
4997 * Is the group utilization affected by cpus outside this
5000 sd = rcu_dereference(per_cpu(sd_scs, cpu));
5004 * We most probably raced with hotplug; returning a
5005 * wrong energy estimation is better than entering an
5011 sg_shared_cap = sd->parent->groups;
5013 for_each_domain(cpu, sd) {
5016 /* Has this sched_domain already been visited? */
5017 if (sd->child && group_first_cpu(sg) != cpu)
5021 unsigned long group_util;
5022 int sg_busy_energy, sg_idle_energy;
5023 int cap_idx, idle_idx;
5025 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
5026 eenv->sg_cap = sg_shared_cap;
5030 cap_idx = find_new_capacity(eenv, sg->sge);
5032 if (sg->group_weight == 1) {
5033 /* Remove capacity of src CPU (before task move) */
5034 if (eenv->util_delta == 0 &&
5035 cpumask_test_cpu(eenv->src_cpu, sched_group_cpus(sg))) {
5036 eenv->cap.before = sg->sge->cap_states[cap_idx].cap;
5037 eenv->cap.delta -= eenv->cap.before;
5039 /* Add capacity of dst CPU (after task move) */
5040 if (eenv->util_delta != 0 &&
5041 cpumask_test_cpu(eenv->dst_cpu, sched_group_cpus(sg))) {
5042 eenv->cap.after = sg->sge->cap_states[cap_idx].cap;
5043 eenv->cap.delta += eenv->cap.after;
5047 idle_idx = group_idle_state(sg);
5048 group_util = group_norm_util(eenv, sg);
5049 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
5050 >> SCHED_CAPACITY_SHIFT;
5051 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
5052 * sg->sge->idle_states[idle_idx].power)
5053 >> SCHED_CAPACITY_SHIFT;
5055 total_energy += sg_busy_energy + sg_idle_energy;
5058 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
5060 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
5063 } while (sg = sg->next, sg != sd->groups);
5066 cpumask_clear_cpu(cpu, &visit_cpus);
5070 eenv->energy = total_energy;
5074 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
5076 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
5080 * energy_diff(): Estimate the energy impact of changing the utilization
5081 * distribution. eenv specifies the change: utilisation amount, source, and
5082 * destination cpu. Source or destination cpu may be -1 in which case the
5083 * utilization is removed from or added to the system (e.g. task wake-up). If
5084 * both are specified, the utilization is migrated.
5086 static inline int __energy_diff(struct energy_env *eenv)
5088 struct sched_domain *sd;
5089 struct sched_group *sg;
5090 int sd_cpu = -1, energy_before = 0, energy_after = 0;
5092 struct energy_env eenv_before = {
5094 .src_cpu = eenv->src_cpu,
5095 .dst_cpu = eenv->dst_cpu,
5096 .nrg = { 0, 0, 0, 0},
5100 if (eenv->src_cpu == eenv->dst_cpu)
5103 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
5104 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
5107 return 0; /* Error */
5112 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
5113 eenv_before.sg_top = eenv->sg_top = sg;
5115 if (sched_group_energy(&eenv_before))
5116 return 0; /* Invalid result abort */
5117 energy_before += eenv_before.energy;
5119 /* Keep track of SRC cpu (before) capacity */
5120 eenv->cap.before = eenv_before.cap.before;
5121 eenv->cap.delta = eenv_before.cap.delta;
5123 if (sched_group_energy(eenv))
5124 return 0; /* Invalid result abort */
5125 energy_after += eenv->energy;
5127 } while (sg = sg->next, sg != sd->groups);
5129 eenv->nrg.before = energy_before;
5130 eenv->nrg.after = energy_after;
5131 eenv->nrg.diff = eenv->nrg.after - eenv->nrg.before;
5134 trace_sched_energy_diff(eenv->task,
5135 eenv->src_cpu, eenv->dst_cpu, eenv->util_delta,
5136 eenv->nrg.before, eenv->nrg.after, eenv->nrg.diff,
5137 eenv->cap.before, eenv->cap.after, eenv->cap.delta,
5138 eenv->nrg.delta, eenv->payoff);
5140 return eenv->nrg.diff;
5143 #ifdef CONFIG_SCHED_TUNE
5145 struct target_nrg schedtune_target_nrg;
5148 * System energy normalization
5149 * Returns the normalized value, in the range [0..SCHED_LOAD_SCALE],
5150 * corresponding to the specified energy variation.
5153 normalize_energy(int energy_diff)
5156 #ifdef CONFIG_SCHED_DEBUG
5159 /* Check for boundaries */
5160 max_delta = schedtune_target_nrg.max_power;
5161 max_delta -= schedtune_target_nrg.min_power;
5162 WARN_ON(abs(energy_diff) >= max_delta);
5165 /* Do scaling using positive numbers to increase the range */
5166 normalized_nrg = (energy_diff < 0) ? -energy_diff : energy_diff;
5168 /* Scale by energy magnitude */
5169 normalized_nrg <<= SCHED_LOAD_SHIFT;
5171 /* Normalize on max energy for target platform */
5172 normalized_nrg = reciprocal_divide(
5173 normalized_nrg, schedtune_target_nrg.rdiv);
5175 return (energy_diff < 0) ? -normalized_nrg : normalized_nrg;
5179 energy_diff(struct energy_env *eenv)
5181 int boost = schedtune_task_boost(eenv->task);
5184 /* Conpute "absolute" energy diff */
5185 __energy_diff(eenv);
5187 /* Return energy diff when boost margin is 0 */
5189 return eenv->nrg.diff;
5191 /* Compute normalized energy diff */
5192 nrg_delta = normalize_energy(eenv->nrg.diff);
5193 eenv->nrg.delta = nrg_delta;
5195 eenv->payoff = schedtune_accept_deltas(
5201 * When SchedTune is enabled, the energy_diff() function will return
5202 * the computed energy payoff value. Since the energy_diff() return
5203 * value is expected to be negative by its callers, this evaluation
5204 * function return a negative value each time the evaluation return a
5205 * positive payoff, which is the condition for the acceptance of
5206 * a scheduling decision
5208 return -eenv->payoff;
5210 #else /* CONFIG_SCHED_TUNE */
5211 #define energy_diff(eenv) __energy_diff(eenv)
5215 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5216 * A waker of many should wake a different task than the one last awakened
5217 * at a frequency roughly N times higher than one of its wakees. In order
5218 * to determine whether we should let the load spread vs consolodating to
5219 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
5220 * partner, and a factor of lls_size higher frequency in the other. With
5221 * both conditions met, we can be relatively sure that the relationship is
5222 * non-monogamous, with partner count exceeding socket size. Waker/wakee
5223 * being client/server, worker/dispatcher, interrupt source or whatever is
5224 * irrelevant, spread criteria is apparent partner count exceeds socket size.
5226 static int wake_wide(struct task_struct *p)
5228 unsigned int master = current->wakee_flips;
5229 unsigned int slave = p->wakee_flips;
5230 int factor = this_cpu_read(sd_llc_size);
5233 swap(master, slave);
5234 if (slave < factor || master < slave * factor)
5239 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5241 s64 this_load, load;
5242 s64 this_eff_load, prev_eff_load;
5243 int idx, this_cpu, prev_cpu;
5244 struct task_group *tg;
5245 unsigned long weight;
5249 this_cpu = smp_processor_id();
5250 prev_cpu = task_cpu(p);
5251 load = source_load(prev_cpu, idx);
5252 this_load = target_load(this_cpu, idx);
5255 * If sync wakeup then subtract the (maximum possible)
5256 * effect of the currently running task from the load
5257 * of the current CPU:
5260 tg = task_group(current);
5261 weight = current->se.avg.load_avg;
5263 this_load += effective_load(tg, this_cpu, -weight, -weight);
5264 load += effective_load(tg, prev_cpu, 0, -weight);
5268 weight = p->se.avg.load_avg;
5271 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5272 * due to the sync cause above having dropped this_load to 0, we'll
5273 * always have an imbalance, but there's really nothing you can do
5274 * about that, so that's good too.
5276 * Otherwise check if either cpus are near enough in load to allow this
5277 * task to be woken on this_cpu.
5279 this_eff_load = 100;
5280 this_eff_load *= capacity_of(prev_cpu);
5282 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5283 prev_eff_load *= capacity_of(this_cpu);
5285 if (this_load > 0) {
5286 this_eff_load *= this_load +
5287 effective_load(tg, this_cpu, weight, weight);
5289 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5292 balanced = this_eff_load <= prev_eff_load;
5294 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5299 schedstat_inc(sd, ttwu_move_affine);
5300 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5305 static inline unsigned long task_util(struct task_struct *p)
5307 #ifdef CONFIG_SCHED_WALT
5308 if (!walt_disabled && sysctl_sched_use_walt_task_util) {
5309 unsigned long demand = p->ravg.demand;
5310 return (demand << 10) / walt_ravg_window;
5313 return p->se.avg.util_avg;
5316 unsigned int capacity_margin = 1280; /* ~20% margin */
5318 static inline unsigned long boosted_task_util(struct task_struct *task);
5320 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5322 unsigned long capacity = capacity_of(cpu);
5324 util += boosted_task_util(p);
5326 return (capacity * 1024) > (util * capacity_margin);
5329 static inline bool task_fits_max(struct task_struct *p, int cpu)
5331 unsigned long capacity = capacity_of(cpu);
5332 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity.val;
5334 if (capacity == max_capacity)
5337 if (capacity * capacity_margin > max_capacity * 1024)
5340 return __task_fits(p, cpu, 0);
5343 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5345 return __task_fits(p, cpu, cpu_util(cpu));
5348 static bool cpu_overutilized(int cpu)
5350 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5353 #ifdef CONFIG_SCHED_TUNE
5356 schedtune_margin(unsigned long signal, long boost)
5358 long long margin = 0;
5361 * Signal proportional compensation (SPC)
5363 * The Boost (B) value is used to compute a Margin (M) which is
5364 * proportional to the complement of the original Signal (S):
5365 * M = B * (SCHED_LOAD_SCALE - S), if B is positive
5366 * M = B * S, if B is negative
5367 * The obtained M could be used by the caller to "boost" S.
5370 margin = SCHED_LOAD_SCALE - signal;
5373 margin = -signal * boost;
5375 * Fast integer division by constant:
5376 * Constant : (C) = 100
5377 * Precision : 0.1% (P) = 0.1
5378 * Reference : C * 100 / P (R) = 100000
5381 * Shift bits : ceil(log(R,2)) (S) = 17
5382 * Mult const : round(2^S/C) (M) = 1311
5395 schedtune_cpu_margin(unsigned long util, int cpu)
5397 int boost = schedtune_cpu_boost(cpu);
5402 return schedtune_margin(util, boost);
5406 schedtune_task_margin(struct task_struct *task)
5408 int boost = schedtune_task_boost(task);
5415 util = task_util(task);
5416 margin = schedtune_margin(util, boost);
5421 #else /* CONFIG_SCHED_TUNE */
5424 schedtune_cpu_margin(unsigned long util, int cpu)
5430 schedtune_task_margin(struct task_struct *task)
5435 #endif /* CONFIG_SCHED_TUNE */
5437 static inline unsigned long
5438 boosted_cpu_util(int cpu)
5440 unsigned long util = cpu_util(cpu);
5441 long margin = schedtune_cpu_margin(util, cpu);
5443 trace_sched_boost_cpu(cpu, util, margin);
5445 return util + margin;
5448 static inline unsigned long
5449 boosted_task_util(struct task_struct *task)
5451 unsigned long util = task_util(task);
5452 long margin = schedtune_task_margin(task);
5454 trace_sched_boost_task(task, util, margin);
5456 return util + margin;
5460 * find_idlest_group finds and returns the least busy CPU group within the
5463 static struct sched_group *
5464 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5465 int this_cpu, int sd_flag)
5467 struct sched_group *idlest = NULL, *group = sd->groups;
5468 struct sched_group *fit_group = NULL, *spare_group = NULL;
5469 unsigned long min_load = ULONG_MAX, this_load = 0;
5470 unsigned long fit_capacity = ULONG_MAX;
5471 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5472 int load_idx = sd->forkexec_idx;
5473 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5475 if (sd_flag & SD_BALANCE_WAKE)
5476 load_idx = sd->wake_idx;
5479 unsigned long load, avg_load, spare_capacity;
5483 /* Skip over this group if it has no CPUs allowed */
5484 if (!cpumask_intersects(sched_group_cpus(group),
5485 tsk_cpus_allowed(p)))
5488 local_group = cpumask_test_cpu(this_cpu,
5489 sched_group_cpus(group));
5491 /* Tally up the load of all CPUs in the group */
5494 for_each_cpu(i, sched_group_cpus(group)) {
5495 /* Bias balancing toward cpus of our domain */
5497 load = source_load(i, load_idx);
5499 load = target_load(i, load_idx);
5504 * Look for most energy-efficient group that can fit
5505 * that can fit the task.
5507 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5508 fit_capacity = capacity_of(i);
5513 * Look for group which has most spare capacity on a
5516 spare_capacity = capacity_of(i) - cpu_util(i);
5517 if (spare_capacity > max_spare_capacity) {
5518 max_spare_capacity = spare_capacity;
5519 spare_group = group;
5523 /* Adjust by relative CPU capacity of the group */
5524 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5527 this_load = avg_load;
5528 } else if (avg_load < min_load) {
5529 min_load = avg_load;
5532 } while (group = group->next, group != sd->groups);
5540 if (!idlest || 100*this_load < imbalance*min_load)
5546 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5549 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5551 unsigned long load, min_load = ULONG_MAX;
5552 unsigned int min_exit_latency = UINT_MAX;
5553 u64 latest_idle_timestamp = 0;
5554 int least_loaded_cpu = this_cpu;
5555 int shallowest_idle_cpu = -1;
5558 /* Traverse only the allowed CPUs */
5559 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5560 if (task_fits_spare(p, i)) {
5561 struct rq *rq = cpu_rq(i);
5562 struct cpuidle_state *idle = idle_get_state(rq);
5563 if (idle && idle->exit_latency < min_exit_latency) {
5565 * We give priority to a CPU whose idle state
5566 * has the smallest exit latency irrespective
5567 * of any idle timestamp.
5569 min_exit_latency = idle->exit_latency;
5570 latest_idle_timestamp = rq->idle_stamp;
5571 shallowest_idle_cpu = i;
5572 } else if (idle_cpu(i) &&
5573 (!idle || idle->exit_latency == min_exit_latency) &&
5574 rq->idle_stamp > latest_idle_timestamp) {
5576 * If equal or no active idle state, then
5577 * the most recently idled CPU might have
5580 latest_idle_timestamp = rq->idle_stamp;
5581 shallowest_idle_cpu = i;
5582 } else if (shallowest_idle_cpu == -1) {
5584 * If we haven't found an idle CPU yet
5585 * pick a non-idle one that can fit the task as
5588 shallowest_idle_cpu = i;
5590 } else if (shallowest_idle_cpu == -1) {
5591 load = weighted_cpuload(i);
5592 if (load < min_load || (load == min_load && i == this_cpu)) {
5594 least_loaded_cpu = i;
5599 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5603 * Try and locate an idle CPU in the sched_domain.
5605 static int select_idle_sibling(struct task_struct *p, int target)
5607 struct sched_domain *sd;
5608 struct sched_group *sg;
5609 int i = task_cpu(p);
5611 int best_idle_cstate = -1;
5612 int best_idle_capacity = INT_MAX;
5614 if (!sysctl_sched_cstate_aware) {
5615 if (idle_cpu(target))
5619 * If the prevous cpu is cache affine and idle, don't be stupid.
5621 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5626 * Otherwise, iterate the domains and find an elegible idle cpu.
5628 sd = rcu_dereference(per_cpu(sd_llc, target));
5629 for_each_lower_domain(sd) {
5632 if (!cpumask_intersects(sched_group_cpus(sg),
5633 tsk_cpus_allowed(p)))
5636 if (sysctl_sched_cstate_aware) {
5637 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg)) {
5638 struct rq *rq = cpu_rq(i);
5639 int idle_idx = idle_get_state_idx(rq);
5640 unsigned long new_usage = boosted_task_util(p);
5641 unsigned long capacity_orig = capacity_orig_of(i);
5642 if (new_usage > capacity_orig || !idle_cpu(i))
5645 if (i == target && new_usage <= capacity_curr_of(target))
5648 if (best_idle < 0 || (idle_idx < best_idle_cstate && capacity_orig <= best_idle_capacity)) {
5650 best_idle_cstate = idle_idx;
5651 best_idle_capacity = capacity_orig;
5655 for_each_cpu(i, sched_group_cpus(sg)) {
5656 if (i == target || !idle_cpu(i))
5660 target = cpumask_first_and(sched_group_cpus(sg),
5661 tsk_cpus_allowed(p));
5666 } while (sg != sd->groups);
5675 static inline int find_best_target(struct task_struct *p, bool boosted, bool prefer_idle)
5678 int target_cpu = -1;
5679 int target_util = 0;
5680 int backup_capacity = 0;
5681 int best_idle_cpu = -1;
5682 int best_idle_cstate = INT_MAX;
5683 int backup_cpu = -1;
5684 unsigned long task_util_boosted, new_util;
5686 task_util_boosted = boosted_task_util(p);
5687 for (iter_cpu = 0; iter_cpu < NR_CPUS; iter_cpu++) {
5693 * Iterate from higher cpus for boosted tasks.
5695 int i = boosted ? NR_CPUS-iter_cpu-1 : iter_cpu;
5697 if (!cpu_online(i) || !cpumask_test_cpu(i, tsk_cpus_allowed(p)))
5701 * p's blocked utilization is still accounted for on prev_cpu
5702 * so prev_cpu will receive a negative bias due to the double
5703 * accounting. However, the blocked utilization may be zero.
5705 new_util = cpu_util(i) + task_util_boosted;
5708 * Ensure minimum capacity to grant the required boost.
5709 * The target CPU can be already at a capacity level higher
5710 * than the one required to boost the task.
5712 if (new_util > capacity_orig_of(i))
5715 #ifdef CONFIG_SCHED_WALT
5716 if (walt_cpu_high_irqload(i))
5720 * Unconditionally favoring tasks that prefer idle cpus to
5723 if (idle_cpu(i) && prefer_idle) {
5724 if (best_idle_cpu < 0)
5729 cur_capacity = capacity_curr_of(i);
5731 idle_idx = idle_get_state_idx(rq);
5733 if (new_util < cur_capacity) {
5734 if (cpu_rq(i)->nr_running) {
5736 /* Find a target cpu with highest
5739 if (target_util == 0 ||
5740 target_util < new_util) {
5742 target_util = new_util;
5745 /* Find a target cpu with lowest
5748 if (target_util == 0 ||
5749 target_util > new_util) {
5751 target_util = new_util;
5754 } else if (!prefer_idle) {
5755 if (best_idle_cpu < 0 ||
5756 (sysctl_sched_cstate_aware &&
5757 best_idle_cstate > idle_idx)) {
5758 best_idle_cstate = idle_idx;
5762 } else if (backup_capacity == 0 ||
5763 backup_capacity > cur_capacity) {
5764 // Find a backup cpu with least capacity.
5765 backup_capacity = cur_capacity;
5770 if (prefer_idle && best_idle_cpu >= 0)
5771 target_cpu = best_idle_cpu;
5772 else if (target_cpu < 0)
5773 target_cpu = best_idle_cpu >= 0 ? best_idle_cpu : backup_cpu;
5778 static int energy_aware_wake_cpu(struct task_struct *p, int target, int sync)
5780 struct sched_domain *sd;
5781 struct sched_group *sg, *sg_target;
5782 int target_max_cap = INT_MAX;
5783 int target_cpu = task_cpu(p);
5784 unsigned long task_util_boosted, new_util;
5787 if (sysctl_sched_sync_hint_enable && sync) {
5788 int cpu = smp_processor_id();
5789 cpumask_t search_cpus;
5790 cpumask_and(&search_cpus, tsk_cpus_allowed(p), cpu_online_mask);
5791 if (cpumask_test_cpu(cpu, &search_cpus))
5795 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5803 if (sysctl_sched_is_big_little) {
5806 * Find group with sufficient capacity. We only get here if no cpu is
5807 * overutilized. We may end up overutilizing a cpu by adding the task,
5808 * but that should not be any worse than select_idle_sibling().
5809 * load_balance() should sort it out later as we get above the tipping
5813 /* Assuming all cpus are the same in group */
5814 int max_cap_cpu = group_first_cpu(sg);
5817 * Assume smaller max capacity means more energy-efficient.
5818 * Ideally we should query the energy model for the right
5819 * answer but it easily ends up in an exhaustive search.
5821 if (capacity_of(max_cap_cpu) < target_max_cap &&
5822 task_fits_max(p, max_cap_cpu)) {
5824 target_max_cap = capacity_of(max_cap_cpu);
5826 } while (sg = sg->next, sg != sd->groups);
5828 task_util_boosted = boosted_task_util(p);
5829 /* Find cpu with sufficient capacity */
5830 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5832 * p's blocked utilization is still accounted for on prev_cpu
5833 * so prev_cpu will receive a negative bias due to the double
5834 * accounting. However, the blocked utilization may be zero.
5836 new_util = cpu_util(i) + task_util_boosted;
5839 * Ensure minimum capacity to grant the required boost.
5840 * The target CPU can be already at a capacity level higher
5841 * than the one required to boost the task.
5843 if (new_util > capacity_orig_of(i))
5846 if (new_util < capacity_curr_of(i)) {
5848 if (cpu_rq(i)->nr_running)
5852 /* cpu has capacity at higher OPP, keep it as fallback */
5853 if (target_cpu == task_cpu(p))
5858 * Find a cpu with sufficient capacity
5860 #ifdef CONFIG_CGROUP_SCHEDTUNE
5861 bool boosted = schedtune_task_boost(p) > 0;
5862 bool prefer_idle = schedtune_prefer_idle(p) > 0;
5865 bool prefer_idle = 0;
5867 int tmp_target = find_best_target(p, boosted, prefer_idle);
5868 if (tmp_target >= 0) {
5869 target_cpu = tmp_target;
5870 if ((boosted || prefer_idle) && idle_cpu(target_cpu))
5875 if (target_cpu != task_cpu(p)) {
5876 struct energy_env eenv = {
5877 .util_delta = task_util(p),
5878 .src_cpu = task_cpu(p),
5879 .dst_cpu = target_cpu,
5883 /* Not enough spare capacity on previous cpu */
5884 if (cpu_overutilized(task_cpu(p)))
5887 if (energy_diff(&eenv) >= 0)
5895 * select_task_rq_fair: Select target runqueue for the waking task in domains
5896 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5897 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5899 * Balances load by selecting the idlest cpu in the idlest group, or under
5900 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5902 * Returns the target cpu number.
5904 * preempt must be disabled.
5907 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5909 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5910 int cpu = smp_processor_id();
5911 int new_cpu = prev_cpu;
5912 int want_affine = 0;
5913 int sync = wake_flags & WF_SYNC;
5915 if (sd_flag & SD_BALANCE_WAKE)
5916 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5917 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5921 for_each_domain(cpu, tmp) {
5922 if (!(tmp->flags & SD_LOAD_BALANCE))
5926 * If both cpu and prev_cpu are part of this domain,
5927 * cpu is a valid SD_WAKE_AFFINE target.
5929 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5930 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5935 if (tmp->flags & sd_flag)
5937 else if (!want_affine)
5942 sd = NULL; /* Prefer wake_affine over balance flags */
5943 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5948 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5949 new_cpu = energy_aware_wake_cpu(p, prev_cpu, sync);
5950 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5951 new_cpu = select_idle_sibling(p, new_cpu);
5954 struct sched_group *group;
5957 if (!(sd->flags & sd_flag)) {
5962 group = find_idlest_group(sd, p, cpu, sd_flag);
5968 new_cpu = find_idlest_cpu(group, p, cpu);
5969 if (new_cpu == -1 || new_cpu == cpu) {
5970 /* Now try balancing at a lower domain level of cpu */
5975 /* Now try balancing at a lower domain level of new_cpu */
5977 weight = sd->span_weight;
5979 for_each_domain(cpu, tmp) {
5980 if (weight <= tmp->span_weight)
5982 if (tmp->flags & sd_flag)
5985 /* while loop will break here if sd == NULL */
5993 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5994 * cfs_rq_of(p) references at time of call are still valid and identify the
5995 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5996 * other assumptions, including the state of rq->lock, should be made.
5998 static void migrate_task_rq_fair(struct task_struct *p)
6001 * We are supposed to update the task to "current" time, then its up to date
6002 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
6003 * what current time is, so simply throw away the out-of-date time. This
6004 * will result in the wakee task is less decayed, but giving the wakee more
6005 * load sounds not bad.
6007 remove_entity_load_avg(&p->se);
6009 /* Tell new CPU we are migrated */
6010 p->se.avg.last_update_time = 0;
6012 /* We have migrated, no longer consider this task hot */
6013 p->se.exec_start = 0;
6016 static void task_dead_fair(struct task_struct *p)
6018 remove_entity_load_avg(&p->se);
6021 #define task_fits_max(p, cpu) true
6022 #endif /* CONFIG_SMP */
6024 static unsigned long
6025 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
6027 unsigned long gran = sysctl_sched_wakeup_granularity;
6030 * Since its curr running now, convert the gran from real-time
6031 * to virtual-time in his units.
6033 * By using 'se' instead of 'curr' we penalize light tasks, so
6034 * they get preempted easier. That is, if 'se' < 'curr' then
6035 * the resulting gran will be larger, therefore penalizing the
6036 * lighter, if otoh 'se' > 'curr' then the resulting gran will
6037 * be smaller, again penalizing the lighter task.
6039 * This is especially important for buddies when the leftmost
6040 * task is higher priority than the buddy.
6042 return calc_delta_fair(gran, se);
6046 * Should 'se' preempt 'curr'.
6060 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
6062 s64 gran, vdiff = curr->vruntime - se->vruntime;
6067 gran = wakeup_gran(curr, se);
6074 static void set_last_buddy(struct sched_entity *se)
6076 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
6079 for_each_sched_entity(se)
6080 cfs_rq_of(se)->last = se;
6083 static void set_next_buddy(struct sched_entity *se)
6085 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
6088 for_each_sched_entity(se)
6089 cfs_rq_of(se)->next = se;
6092 static void set_skip_buddy(struct sched_entity *se)
6094 for_each_sched_entity(se)
6095 cfs_rq_of(se)->skip = se;
6099 * Preempt the current task with a newly woken task if needed:
6101 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6103 struct task_struct *curr = rq->curr;
6104 struct sched_entity *se = &curr->se, *pse = &p->se;
6105 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6106 int scale = cfs_rq->nr_running >= sched_nr_latency;
6107 int next_buddy_marked = 0;
6109 if (unlikely(se == pse))
6113 * This is possible from callers such as attach_tasks(), in which we
6114 * unconditionally check_prempt_curr() after an enqueue (which may have
6115 * lead to a throttle). This both saves work and prevents false
6116 * next-buddy nomination below.
6118 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
6121 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
6122 set_next_buddy(pse);
6123 next_buddy_marked = 1;
6127 * We can come here with TIF_NEED_RESCHED already set from new task
6130 * Note: this also catches the edge-case of curr being in a throttled
6131 * group (e.g. via set_curr_task), since update_curr() (in the
6132 * enqueue of curr) will have resulted in resched being set. This
6133 * prevents us from potentially nominating it as a false LAST_BUDDY
6136 if (test_tsk_need_resched(curr))
6139 /* Idle tasks are by definition preempted by non-idle tasks. */
6140 if (unlikely(curr->policy == SCHED_IDLE) &&
6141 likely(p->policy != SCHED_IDLE))
6145 * Batch and idle tasks do not preempt non-idle tasks (their preemption
6146 * is driven by the tick):
6148 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6151 find_matching_se(&se, &pse);
6152 update_curr(cfs_rq_of(se));
6154 if (wakeup_preempt_entity(se, pse) == 1) {
6156 * Bias pick_next to pick the sched entity that is
6157 * triggering this preemption.
6159 if (!next_buddy_marked)
6160 set_next_buddy(pse);
6169 * Only set the backward buddy when the current task is still
6170 * on the rq. This can happen when a wakeup gets interleaved
6171 * with schedule on the ->pre_schedule() or idle_balance()
6172 * point, either of which can * drop the rq lock.
6174 * Also, during early boot the idle thread is in the fair class,
6175 * for obvious reasons its a bad idea to schedule back to it.
6177 if (unlikely(!se->on_rq || curr == rq->idle))
6180 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
6184 static struct task_struct *
6185 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
6187 struct cfs_rq *cfs_rq = &rq->cfs;
6188 struct sched_entity *se;
6189 struct task_struct *p;
6193 #ifdef CONFIG_FAIR_GROUP_SCHED
6194 if (!cfs_rq->nr_running)
6197 if (prev->sched_class != &fair_sched_class)
6201 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
6202 * likely that a next task is from the same cgroup as the current.
6204 * Therefore attempt to avoid putting and setting the entire cgroup
6205 * hierarchy, only change the part that actually changes.
6209 struct sched_entity *curr = cfs_rq->curr;
6212 * Since we got here without doing put_prev_entity() we also
6213 * have to consider cfs_rq->curr. If it is still a runnable
6214 * entity, update_curr() will update its vruntime, otherwise
6215 * forget we've ever seen it.
6219 update_curr(cfs_rq);
6224 * This call to check_cfs_rq_runtime() will do the
6225 * throttle and dequeue its entity in the parent(s).
6226 * Therefore the 'simple' nr_running test will indeed
6229 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
6233 se = pick_next_entity(cfs_rq, curr);
6234 cfs_rq = group_cfs_rq(se);
6240 * Since we haven't yet done put_prev_entity and if the selected task
6241 * is a different task than we started out with, try and touch the
6242 * least amount of cfs_rqs.
6245 struct sched_entity *pse = &prev->se;
6247 while (!(cfs_rq = is_same_group(se, pse))) {
6248 int se_depth = se->depth;
6249 int pse_depth = pse->depth;
6251 if (se_depth <= pse_depth) {
6252 put_prev_entity(cfs_rq_of(pse), pse);
6253 pse = parent_entity(pse);
6255 if (se_depth >= pse_depth) {
6256 set_next_entity(cfs_rq_of(se), se);
6257 se = parent_entity(se);
6261 put_prev_entity(cfs_rq, pse);
6262 set_next_entity(cfs_rq, se);
6265 if (hrtick_enabled(rq))
6266 hrtick_start_fair(rq, p);
6268 rq->misfit_task = !task_fits_max(p, rq->cpu);
6275 if (!cfs_rq->nr_running)
6278 put_prev_task(rq, prev);
6281 se = pick_next_entity(cfs_rq, NULL);
6282 set_next_entity(cfs_rq, se);
6283 cfs_rq = group_cfs_rq(se);
6288 if (hrtick_enabled(rq))
6289 hrtick_start_fair(rq, p);
6291 rq->misfit_task = !task_fits_max(p, rq->cpu);
6296 rq->misfit_task = 0;
6298 * This is OK, because current is on_cpu, which avoids it being picked
6299 * for load-balance and preemption/IRQs are still disabled avoiding
6300 * further scheduler activity on it and we're being very careful to
6301 * re-start the picking loop.
6303 lockdep_unpin_lock(&rq->lock);
6304 new_tasks = idle_balance(rq);
6305 lockdep_pin_lock(&rq->lock);
6307 * Because idle_balance() releases (and re-acquires) rq->lock, it is
6308 * possible for any higher priority task to appear. In that case we
6309 * must re-start the pick_next_entity() loop.
6321 * Account for a descheduled task:
6323 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6325 struct sched_entity *se = &prev->se;
6326 struct cfs_rq *cfs_rq;
6328 for_each_sched_entity(se) {
6329 cfs_rq = cfs_rq_of(se);
6330 put_prev_entity(cfs_rq, se);
6335 * sched_yield() is very simple
6337 * The magic of dealing with the ->skip buddy is in pick_next_entity.
6339 static void yield_task_fair(struct rq *rq)
6341 struct task_struct *curr = rq->curr;
6342 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6343 struct sched_entity *se = &curr->se;
6346 * Are we the only task in the tree?
6348 if (unlikely(rq->nr_running == 1))
6351 clear_buddies(cfs_rq, se);
6353 if (curr->policy != SCHED_BATCH) {
6354 update_rq_clock(rq);
6356 * Update run-time statistics of the 'current'.
6358 update_curr(cfs_rq);
6360 * Tell update_rq_clock() that we've just updated,
6361 * so we don't do microscopic update in schedule()
6362 * and double the fastpath cost.
6364 rq_clock_skip_update(rq, true);
6370 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
6372 struct sched_entity *se = &p->se;
6374 /* throttled hierarchies are not runnable */
6375 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6378 /* Tell the scheduler that we'd really like pse to run next. */
6381 yield_task_fair(rq);
6387 /**************************************************
6388 * Fair scheduling class load-balancing methods.
6392 * The purpose of load-balancing is to achieve the same basic fairness the
6393 * per-cpu scheduler provides, namely provide a proportional amount of compute
6394 * time to each task. This is expressed in the following equation:
6396 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
6398 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
6399 * W_i,0 is defined as:
6401 * W_i,0 = \Sum_j w_i,j (2)
6403 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6404 * is derived from the nice value as per prio_to_weight[].
6406 * The weight average is an exponential decay average of the instantaneous
6409 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
6411 * C_i is the compute capacity of cpu i, typically it is the
6412 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
6413 * can also include other factors [XXX].
6415 * To achieve this balance we define a measure of imbalance which follows
6416 * directly from (1):
6418 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
6420 * We them move tasks around to minimize the imbalance. In the continuous
6421 * function space it is obvious this converges, in the discrete case we get
6422 * a few fun cases generally called infeasible weight scenarios.
6425 * - infeasible weights;
6426 * - local vs global optima in the discrete case. ]
6431 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6432 * for all i,j solution, we create a tree of cpus that follows the hardware
6433 * topology where each level pairs two lower groups (or better). This results
6434 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
6435 * tree to only the first of the previous level and we decrease the frequency
6436 * of load-balance at each level inv. proportional to the number of cpus in
6442 * \Sum { --- * --- * 2^i } = O(n) (5)
6444 * `- size of each group
6445 * | | `- number of cpus doing load-balance
6447 * `- sum over all levels
6449 * Coupled with a limit on how many tasks we can migrate every balance pass,
6450 * this makes (5) the runtime complexity of the balancer.
6452 * An important property here is that each CPU is still (indirectly) connected
6453 * to every other cpu in at most O(log n) steps:
6455 * The adjacency matrix of the resulting graph is given by:
6458 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
6461 * And you'll find that:
6463 * A^(log_2 n)_i,j != 0 for all i,j (7)
6465 * Showing there's indeed a path between every cpu in at most O(log n) steps.
6466 * The task movement gives a factor of O(m), giving a convergence complexity
6469 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
6474 * In order to avoid CPUs going idle while there's still work to do, new idle
6475 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6476 * tree itself instead of relying on other CPUs to bring it work.
6478 * This adds some complexity to both (5) and (8) but it reduces the total idle
6486 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6489 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6494 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6496 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6498 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6501 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6502 * rewrite all of this once again.]
6505 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6507 enum fbq_type { regular, remote, all };
6516 #define LBF_ALL_PINNED 0x01
6517 #define LBF_NEED_BREAK 0x02
6518 #define LBF_DST_PINNED 0x04
6519 #define LBF_SOME_PINNED 0x08
6522 struct sched_domain *sd;
6530 struct cpumask *dst_grpmask;
6532 enum cpu_idle_type idle;
6534 unsigned int src_grp_nr_running;
6535 /* The set of CPUs under consideration for load-balancing */
6536 struct cpumask *cpus;
6541 unsigned int loop_break;
6542 unsigned int loop_max;
6544 enum fbq_type fbq_type;
6545 enum group_type busiest_group_type;
6546 struct list_head tasks;
6550 * Is this task likely cache-hot:
6552 static int task_hot(struct task_struct *p, struct lb_env *env)
6556 lockdep_assert_held(&env->src_rq->lock);
6558 if (p->sched_class != &fair_sched_class)
6561 if (unlikely(p->policy == SCHED_IDLE))
6565 * Buddy candidates are cache hot:
6567 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6568 (&p->se == cfs_rq_of(&p->se)->next ||
6569 &p->se == cfs_rq_of(&p->se)->last))
6572 if (sysctl_sched_migration_cost == -1)
6574 if (sysctl_sched_migration_cost == 0)
6577 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6579 return delta < (s64)sysctl_sched_migration_cost;
6582 #ifdef CONFIG_NUMA_BALANCING
6584 * Returns 1, if task migration degrades locality
6585 * Returns 0, if task migration improves locality i.e migration preferred.
6586 * Returns -1, if task migration is not affected by locality.
6588 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6590 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6591 unsigned long src_faults, dst_faults;
6592 int src_nid, dst_nid;
6594 if (!static_branch_likely(&sched_numa_balancing))
6597 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6600 src_nid = cpu_to_node(env->src_cpu);
6601 dst_nid = cpu_to_node(env->dst_cpu);
6603 if (src_nid == dst_nid)
6606 /* Migrating away from the preferred node is always bad. */
6607 if (src_nid == p->numa_preferred_nid) {
6608 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6614 /* Encourage migration to the preferred node. */
6615 if (dst_nid == p->numa_preferred_nid)
6619 src_faults = group_faults(p, src_nid);
6620 dst_faults = group_faults(p, dst_nid);
6622 src_faults = task_faults(p, src_nid);
6623 dst_faults = task_faults(p, dst_nid);
6626 return dst_faults < src_faults;
6630 static inline int migrate_degrades_locality(struct task_struct *p,
6638 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6641 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6645 lockdep_assert_held(&env->src_rq->lock);
6648 * We do not migrate tasks that are:
6649 * 1) throttled_lb_pair, or
6650 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6651 * 3) running (obviously), or
6652 * 4) are cache-hot on their current CPU.
6654 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6657 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6660 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6662 env->flags |= LBF_SOME_PINNED;
6665 * Remember if this task can be migrated to any other cpu in
6666 * our sched_group. We may want to revisit it if we couldn't
6667 * meet load balance goals by pulling other tasks on src_cpu.
6669 * Also avoid computing new_dst_cpu if we have already computed
6670 * one in current iteration.
6672 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6675 /* Prevent to re-select dst_cpu via env's cpus */
6676 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6677 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6678 env->flags |= LBF_DST_PINNED;
6679 env->new_dst_cpu = cpu;
6687 /* Record that we found atleast one task that could run on dst_cpu */
6688 env->flags &= ~LBF_ALL_PINNED;
6690 if (task_running(env->src_rq, p)) {
6691 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6696 * Aggressive migration if:
6697 * 1) destination numa is preferred
6698 * 2) task is cache cold, or
6699 * 3) too many balance attempts have failed.
6701 tsk_cache_hot = migrate_degrades_locality(p, env);
6702 if (tsk_cache_hot == -1)
6703 tsk_cache_hot = task_hot(p, env);
6705 if (tsk_cache_hot <= 0 ||
6706 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6707 if (tsk_cache_hot == 1) {
6708 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6709 schedstat_inc(p, se.statistics.nr_forced_migrations);
6714 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6719 * detach_task() -- detach the task for the migration specified in env
6721 static void detach_task(struct task_struct *p, struct lb_env *env)
6723 lockdep_assert_held(&env->src_rq->lock);
6725 deactivate_task(env->src_rq, p, 0);
6726 p->on_rq = TASK_ON_RQ_MIGRATING;
6727 double_lock_balance(env->src_rq, env->dst_rq);
6728 set_task_cpu(p, env->dst_cpu);
6729 double_unlock_balance(env->src_rq, env->dst_rq);
6733 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6734 * part of active balancing operations within "domain".
6736 * Returns a task if successful and NULL otherwise.
6738 static struct task_struct *detach_one_task(struct lb_env *env)
6740 struct task_struct *p, *n;
6742 lockdep_assert_held(&env->src_rq->lock);
6744 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6745 if (!can_migrate_task(p, env))
6748 detach_task(p, env);
6751 * Right now, this is only the second place where
6752 * lb_gained[env->idle] is updated (other is detach_tasks)
6753 * so we can safely collect stats here rather than
6754 * inside detach_tasks().
6756 schedstat_inc(env->sd, lb_gained[env->idle]);
6762 static const unsigned int sched_nr_migrate_break = 32;
6765 * detach_tasks() -- tries to detach up to imbalance weighted load from
6766 * busiest_rq, as part of a balancing operation within domain "sd".
6768 * Returns number of detached tasks if successful and 0 otherwise.
6770 static int detach_tasks(struct lb_env *env)
6772 struct list_head *tasks = &env->src_rq->cfs_tasks;
6773 struct task_struct *p;
6777 lockdep_assert_held(&env->src_rq->lock);
6779 if (env->imbalance <= 0)
6782 while (!list_empty(tasks)) {
6784 * We don't want to steal all, otherwise we may be treated likewise,
6785 * which could at worst lead to a livelock crash.
6787 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6790 p = list_first_entry(tasks, struct task_struct, se.group_node);
6793 /* We've more or less seen every task there is, call it quits */
6794 if (env->loop > env->loop_max)
6797 /* take a breather every nr_migrate tasks */
6798 if (env->loop > env->loop_break) {
6799 env->loop_break += sched_nr_migrate_break;
6800 env->flags |= LBF_NEED_BREAK;
6804 if (!can_migrate_task(p, env))
6807 load = task_h_load(p);
6809 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6812 if ((load / 2) > env->imbalance)
6815 detach_task(p, env);
6816 list_add(&p->se.group_node, &env->tasks);
6819 env->imbalance -= load;
6821 #ifdef CONFIG_PREEMPT
6823 * NEWIDLE balancing is a source of latency, so preemptible
6824 * kernels will stop after the first task is detached to minimize
6825 * the critical section.
6827 if (env->idle == CPU_NEWLY_IDLE)
6832 * We only want to steal up to the prescribed amount of
6835 if (env->imbalance <= 0)
6840 list_move_tail(&p->se.group_node, tasks);
6844 * Right now, this is one of only two places we collect this stat
6845 * so we can safely collect detach_one_task() stats here rather
6846 * than inside detach_one_task().
6848 schedstat_add(env->sd, lb_gained[env->idle], detached);
6854 * attach_task() -- attach the task detached by detach_task() to its new rq.
6856 static void attach_task(struct rq *rq, struct task_struct *p)
6858 lockdep_assert_held(&rq->lock);
6860 BUG_ON(task_rq(p) != rq);
6861 p->on_rq = TASK_ON_RQ_QUEUED;
6862 activate_task(rq, p, 0);
6863 check_preempt_curr(rq, p, 0);
6867 * attach_one_task() -- attaches the task returned from detach_one_task() to
6870 static void attach_one_task(struct rq *rq, struct task_struct *p)
6872 raw_spin_lock(&rq->lock);
6875 * We want to potentially raise target_cpu's OPP.
6877 update_capacity_of(cpu_of(rq));
6878 raw_spin_unlock(&rq->lock);
6882 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6885 static void attach_tasks(struct lb_env *env)
6887 struct list_head *tasks = &env->tasks;
6888 struct task_struct *p;
6890 raw_spin_lock(&env->dst_rq->lock);
6892 while (!list_empty(tasks)) {
6893 p = list_first_entry(tasks, struct task_struct, se.group_node);
6894 list_del_init(&p->se.group_node);
6896 attach_task(env->dst_rq, p);
6900 * We want to potentially raise env.dst_cpu's OPP.
6902 update_capacity_of(env->dst_cpu);
6904 raw_spin_unlock(&env->dst_rq->lock);
6907 #ifdef CONFIG_FAIR_GROUP_SCHED
6908 static void update_blocked_averages(int cpu)
6910 struct rq *rq = cpu_rq(cpu);
6911 struct cfs_rq *cfs_rq;
6912 unsigned long flags;
6914 raw_spin_lock_irqsave(&rq->lock, flags);
6915 update_rq_clock(rq);
6918 * Iterates the task_group tree in a bottom up fashion, see
6919 * list_add_leaf_cfs_rq() for details.
6921 for_each_leaf_cfs_rq(rq, cfs_rq) {
6922 /* throttled entities do not contribute to load */
6923 if (throttled_hierarchy(cfs_rq))
6926 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6927 update_tg_load_avg(cfs_rq, 0);
6929 raw_spin_unlock_irqrestore(&rq->lock, flags);
6933 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6934 * This needs to be done in a top-down fashion because the load of a child
6935 * group is a fraction of its parents load.
6937 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6939 struct rq *rq = rq_of(cfs_rq);
6940 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6941 unsigned long now = jiffies;
6944 if (cfs_rq->last_h_load_update == now)
6947 cfs_rq->h_load_next = NULL;
6948 for_each_sched_entity(se) {
6949 cfs_rq = cfs_rq_of(se);
6950 cfs_rq->h_load_next = se;
6951 if (cfs_rq->last_h_load_update == now)
6956 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6957 cfs_rq->last_h_load_update = now;
6960 while ((se = cfs_rq->h_load_next) != NULL) {
6961 load = cfs_rq->h_load;
6962 load = div64_ul(load * se->avg.load_avg,
6963 cfs_rq_load_avg(cfs_rq) + 1);
6964 cfs_rq = group_cfs_rq(se);
6965 cfs_rq->h_load = load;
6966 cfs_rq->last_h_load_update = now;
6970 static unsigned long task_h_load(struct task_struct *p)
6972 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6974 update_cfs_rq_h_load(cfs_rq);
6975 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6976 cfs_rq_load_avg(cfs_rq) + 1);
6979 static inline void update_blocked_averages(int cpu)
6981 struct rq *rq = cpu_rq(cpu);
6982 struct cfs_rq *cfs_rq = &rq->cfs;
6983 unsigned long flags;
6985 raw_spin_lock_irqsave(&rq->lock, flags);
6986 update_rq_clock(rq);
6987 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6988 raw_spin_unlock_irqrestore(&rq->lock, flags);
6991 static unsigned long task_h_load(struct task_struct *p)
6993 return p->se.avg.load_avg;
6997 /********** Helpers for find_busiest_group ************************/
7000 * sg_lb_stats - stats of a sched_group required for load_balancing
7002 struct sg_lb_stats {
7003 unsigned long avg_load; /*Avg load across the CPUs of the group */
7004 unsigned long group_load; /* Total load over the CPUs of the group */
7005 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
7006 unsigned long load_per_task;
7007 unsigned long group_capacity;
7008 unsigned long group_util; /* Total utilization of the group */
7009 unsigned int sum_nr_running; /* Nr tasks running in the group */
7010 unsigned int idle_cpus;
7011 unsigned int group_weight;
7012 enum group_type group_type;
7013 int group_no_capacity;
7014 int group_misfit_task; /* A cpu has a task too big for its capacity */
7015 #ifdef CONFIG_NUMA_BALANCING
7016 unsigned int nr_numa_running;
7017 unsigned int nr_preferred_running;
7022 * sd_lb_stats - Structure to store the statistics of a sched_domain
7023 * during load balancing.
7025 struct sd_lb_stats {
7026 struct sched_group *busiest; /* Busiest group in this sd */
7027 struct sched_group *local; /* Local group in this sd */
7028 unsigned long total_load; /* Total load of all groups in sd */
7029 unsigned long total_capacity; /* Total capacity of all groups in sd */
7030 unsigned long avg_load; /* Average load across all groups in sd */
7032 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7033 struct sg_lb_stats local_stat; /* Statistics of the local group */
7036 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
7039 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
7040 * local_stat because update_sg_lb_stats() does a full clear/assignment.
7041 * We must however clear busiest_stat::avg_load because
7042 * update_sd_pick_busiest() reads this before assignment.
7044 *sds = (struct sd_lb_stats){
7048 .total_capacity = 0UL,
7051 .sum_nr_running = 0,
7052 .group_type = group_other,
7058 * get_sd_load_idx - Obtain the load index for a given sched domain.
7059 * @sd: The sched_domain whose load_idx is to be obtained.
7060 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7062 * Return: The load index.
7064 static inline int get_sd_load_idx(struct sched_domain *sd,
7065 enum cpu_idle_type idle)
7071 load_idx = sd->busy_idx;
7074 case CPU_NEWLY_IDLE:
7075 load_idx = sd->newidle_idx;
7078 load_idx = sd->idle_idx;
7085 static unsigned long scale_rt_capacity(int cpu)
7087 struct rq *rq = cpu_rq(cpu);
7088 u64 total, used, age_stamp, avg;
7092 * Since we're reading these variables without serialization make sure
7093 * we read them once before doing sanity checks on them.
7095 age_stamp = READ_ONCE(rq->age_stamp);
7096 avg = READ_ONCE(rq->rt_avg);
7097 delta = __rq_clock_broken(rq) - age_stamp;
7099 if (unlikely(delta < 0))
7102 total = sched_avg_period() + delta;
7104 used = div_u64(avg, total);
7107 * deadline bandwidth is defined at system level so we must
7108 * weight this bandwidth with the max capacity of the system.
7109 * As a reminder, avg_bw is 20bits width and
7110 * scale_cpu_capacity is 10 bits width
7112 used += div_u64(rq->dl.avg_bw, arch_scale_cpu_capacity(NULL, cpu));
7114 if (likely(used < SCHED_CAPACITY_SCALE))
7115 return SCHED_CAPACITY_SCALE - used;
7120 void init_max_cpu_capacity(struct max_cpu_capacity *mcc)
7122 raw_spin_lock_init(&mcc->lock);
7127 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7129 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7130 struct sched_group *sdg = sd->groups;
7131 struct max_cpu_capacity *mcc;
7132 unsigned long max_capacity;
7134 unsigned long flags;
7136 cpu_rq(cpu)->cpu_capacity_orig = capacity;
7138 mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
7140 raw_spin_lock_irqsave(&mcc->lock, flags);
7141 max_capacity = mcc->val;
7142 max_cap_cpu = mcc->cpu;
7144 if ((max_capacity > capacity && max_cap_cpu == cpu) ||
7145 (max_capacity < capacity)) {
7146 mcc->val = capacity;
7148 #ifdef CONFIG_SCHED_DEBUG
7149 raw_spin_unlock_irqrestore(&mcc->lock, flags);
7150 printk_deferred(KERN_INFO "CPU%d: update max cpu_capacity %lu\n",
7155 raw_spin_unlock_irqrestore(&mcc->lock, flags);
7157 skip_unlock: __attribute__ ((unused));
7158 capacity *= scale_rt_capacity(cpu);
7159 capacity >>= SCHED_CAPACITY_SHIFT;
7164 cpu_rq(cpu)->cpu_capacity = capacity;
7165 sdg->sgc->capacity = capacity;
7166 sdg->sgc->max_capacity = capacity;
7169 void update_group_capacity(struct sched_domain *sd, int cpu)
7171 struct sched_domain *child = sd->child;
7172 struct sched_group *group, *sdg = sd->groups;
7173 unsigned long capacity, max_capacity;
7174 unsigned long interval;
7176 interval = msecs_to_jiffies(sd->balance_interval);
7177 interval = clamp(interval, 1UL, max_load_balance_interval);
7178 sdg->sgc->next_update = jiffies + interval;
7181 update_cpu_capacity(sd, cpu);
7188 if (child->flags & SD_OVERLAP) {
7190 * SD_OVERLAP domains cannot assume that child groups
7191 * span the current group.
7194 for_each_cpu(cpu, sched_group_cpus(sdg)) {
7195 struct sched_group_capacity *sgc;
7196 struct rq *rq = cpu_rq(cpu);
7199 * build_sched_domains() -> init_sched_groups_capacity()
7200 * gets here before we've attached the domains to the
7203 * Use capacity_of(), which is set irrespective of domains
7204 * in update_cpu_capacity().
7206 * This avoids capacity from being 0 and
7207 * causing divide-by-zero issues on boot.
7209 if (unlikely(!rq->sd)) {
7210 capacity += capacity_of(cpu);
7212 sgc = rq->sd->groups->sgc;
7213 capacity += sgc->capacity;
7216 max_capacity = max(capacity, max_capacity);
7220 * !SD_OVERLAP domains can assume that child groups
7221 * span the current group.
7224 group = child->groups;
7226 struct sched_group_capacity *sgc = group->sgc;
7228 capacity += sgc->capacity;
7229 max_capacity = max(sgc->max_capacity, max_capacity);
7230 group = group->next;
7231 } while (group != child->groups);
7234 sdg->sgc->capacity = capacity;
7235 sdg->sgc->max_capacity = max_capacity;
7239 * Check whether the capacity of the rq has been noticeably reduced by side
7240 * activity. The imbalance_pct is used for the threshold.
7241 * Return true is the capacity is reduced
7244 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7246 return ((rq->cpu_capacity * sd->imbalance_pct) <
7247 (rq->cpu_capacity_orig * 100));
7251 * Group imbalance indicates (and tries to solve) the problem where balancing
7252 * groups is inadequate due to tsk_cpus_allowed() constraints.
7254 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
7255 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
7258 * { 0 1 2 3 } { 4 5 6 7 }
7261 * If we were to balance group-wise we'd place two tasks in the first group and
7262 * two tasks in the second group. Clearly this is undesired as it will overload
7263 * cpu 3 and leave one of the cpus in the second group unused.
7265 * The current solution to this issue is detecting the skew in the first group
7266 * by noticing the lower domain failed to reach balance and had difficulty
7267 * moving tasks due to affinity constraints.
7269 * When this is so detected; this group becomes a candidate for busiest; see
7270 * update_sd_pick_busiest(). And calculate_imbalance() and
7271 * find_busiest_group() avoid some of the usual balance conditions to allow it
7272 * to create an effective group imbalance.
7274 * This is a somewhat tricky proposition since the next run might not find the
7275 * group imbalance and decide the groups need to be balanced again. A most
7276 * subtle and fragile situation.
7279 static inline int sg_imbalanced(struct sched_group *group)
7281 return group->sgc->imbalance;
7285 * group_has_capacity returns true if the group has spare capacity that could
7286 * be used by some tasks.
7287 * We consider that a group has spare capacity if the * number of task is
7288 * smaller than the number of CPUs or if the utilization is lower than the
7289 * available capacity for CFS tasks.
7290 * For the latter, we use a threshold to stabilize the state, to take into
7291 * account the variance of the tasks' load and to return true if the available
7292 * capacity in meaningful for the load balancer.
7293 * As an example, an available capacity of 1% can appear but it doesn't make
7294 * any benefit for the load balance.
7297 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7299 if (sgs->sum_nr_running < sgs->group_weight)
7302 if ((sgs->group_capacity * 100) >
7303 (sgs->group_util * env->sd->imbalance_pct))
7310 * group_is_overloaded returns true if the group has more tasks than it can
7312 * group_is_overloaded is not equals to !group_has_capacity because a group
7313 * with the exact right number of tasks, has no more spare capacity but is not
7314 * overloaded so both group_has_capacity and group_is_overloaded return
7318 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
7320 if (sgs->sum_nr_running <= sgs->group_weight)
7323 if ((sgs->group_capacity * 100) <
7324 (sgs->group_util * env->sd->imbalance_pct))
7332 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
7333 * per-cpu capacity than sched_group ref.
7336 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
7338 return sg->sgc->max_capacity + capacity_margin - SCHED_LOAD_SCALE <
7339 ref->sgc->max_capacity;
7343 group_type group_classify(struct sched_group *group,
7344 struct sg_lb_stats *sgs)
7346 if (sgs->group_no_capacity)
7347 return group_overloaded;
7349 if (sg_imbalanced(group))
7350 return group_imbalanced;
7352 if (sgs->group_misfit_task)
7353 return group_misfit_task;
7359 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7360 * @env: The load balancing environment.
7361 * @group: sched_group whose statistics are to be updated.
7362 * @load_idx: Load index of sched_domain of this_cpu for load calc.
7363 * @local_group: Does group contain this_cpu.
7364 * @sgs: variable to hold the statistics for this group.
7365 * @overload: Indicate more than one runnable task for any CPU.
7366 * @overutilized: Indicate overutilization for any CPU.
7368 static inline void update_sg_lb_stats(struct lb_env *env,
7369 struct sched_group *group, int load_idx,
7370 int local_group, struct sg_lb_stats *sgs,
7371 bool *overload, bool *overutilized)
7376 memset(sgs, 0, sizeof(*sgs));
7378 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7379 struct rq *rq = cpu_rq(i);
7381 /* Bias balancing toward cpus of our domain */
7383 load = target_load(i, load_idx);
7385 load = source_load(i, load_idx);
7387 sgs->group_load += load;
7388 sgs->group_util += cpu_util(i);
7389 sgs->sum_nr_running += rq->cfs.h_nr_running;
7391 nr_running = rq->nr_running;
7395 #ifdef CONFIG_NUMA_BALANCING
7396 sgs->nr_numa_running += rq->nr_numa_running;
7397 sgs->nr_preferred_running += rq->nr_preferred_running;
7399 sgs->sum_weighted_load += weighted_cpuload(i);
7401 * No need to call idle_cpu() if nr_running is not 0
7403 if (!nr_running && idle_cpu(i))
7406 if (cpu_overutilized(i)) {
7407 *overutilized = true;
7408 if (!sgs->group_misfit_task && rq->misfit_task)
7409 sgs->group_misfit_task = capacity_of(i);
7413 /* Adjust by relative CPU capacity of the group */
7414 sgs->group_capacity = group->sgc->capacity;
7415 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7417 if (sgs->sum_nr_running)
7418 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7420 sgs->group_weight = group->group_weight;
7422 sgs->group_no_capacity = group_is_overloaded(env, sgs);
7423 sgs->group_type = group_classify(group, sgs);
7427 * update_sd_pick_busiest - return 1 on busiest group
7428 * @env: The load balancing environment.
7429 * @sds: sched_domain statistics
7430 * @sg: sched_group candidate to be checked for being the busiest
7431 * @sgs: sched_group statistics
7433 * Determine if @sg is a busier group than the previously selected
7436 * Return: %true if @sg is a busier group than the previously selected
7437 * busiest group. %false otherwise.
7439 static bool update_sd_pick_busiest(struct lb_env *env,
7440 struct sd_lb_stats *sds,
7441 struct sched_group *sg,
7442 struct sg_lb_stats *sgs)
7444 struct sg_lb_stats *busiest = &sds->busiest_stat;
7446 if (sgs->group_type > busiest->group_type)
7449 if (sgs->group_type < busiest->group_type)
7453 * Candidate sg doesn't face any serious load-balance problems
7454 * so don't pick it if the local sg is already filled up.
7456 if (sgs->group_type == group_other &&
7457 !group_has_capacity(env, &sds->local_stat))
7460 if (sgs->avg_load <= busiest->avg_load)
7464 * Candiate sg has no more than one task per cpu and has higher
7465 * per-cpu capacity. No reason to pull tasks to less capable cpus.
7467 if (sgs->sum_nr_running <= sgs->group_weight &&
7468 group_smaller_cpu_capacity(sds->local, sg))
7471 /* This is the busiest node in its class. */
7472 if (!(env->sd->flags & SD_ASYM_PACKING))
7476 * ASYM_PACKING needs to move all the work to the lowest
7477 * numbered CPUs in the group, therefore mark all groups
7478 * higher than ourself as busy.
7480 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
7484 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
7491 #ifdef CONFIG_NUMA_BALANCING
7492 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7494 if (sgs->sum_nr_running > sgs->nr_numa_running)
7496 if (sgs->sum_nr_running > sgs->nr_preferred_running)
7501 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7503 if (rq->nr_running > rq->nr_numa_running)
7505 if (rq->nr_running > rq->nr_preferred_running)
7510 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7515 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7519 #endif /* CONFIG_NUMA_BALANCING */
7522 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7523 * @env: The load balancing environment.
7524 * @sds: variable to hold the statistics for this sched_domain.
7526 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7528 struct sched_domain *child = env->sd->child;
7529 struct sched_group *sg = env->sd->groups;
7530 struct sg_lb_stats tmp_sgs;
7531 int load_idx, prefer_sibling = 0;
7532 bool overload = false, overutilized = false;
7534 if (child && child->flags & SD_PREFER_SIBLING)
7537 load_idx = get_sd_load_idx(env->sd, env->idle);
7540 struct sg_lb_stats *sgs = &tmp_sgs;
7543 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7546 sgs = &sds->local_stat;
7548 if (env->idle != CPU_NEWLY_IDLE ||
7549 time_after_eq(jiffies, sg->sgc->next_update))
7550 update_group_capacity(env->sd, env->dst_cpu);
7553 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7554 &overload, &overutilized);
7560 * In case the child domain prefers tasks go to siblings
7561 * first, lower the sg capacity so that we'll try
7562 * and move all the excess tasks away. We lower the capacity
7563 * of a group only if the local group has the capacity to fit
7564 * these excess tasks. The extra check prevents the case where
7565 * you always pull from the heaviest group when it is already
7566 * under-utilized (possible with a large weight task outweighs
7567 * the tasks on the system).
7569 if (prefer_sibling && sds->local &&
7570 group_has_capacity(env, &sds->local_stat) &&
7571 (sgs->sum_nr_running > 1)) {
7572 sgs->group_no_capacity = 1;
7573 sgs->group_type = group_classify(sg, sgs);
7577 * Ignore task groups with misfit tasks if local group has no
7578 * capacity or if per-cpu capacity isn't higher.
7580 if (sgs->group_type == group_misfit_task &&
7581 (!group_has_capacity(env, &sds->local_stat) ||
7582 !group_smaller_cpu_capacity(sg, sds->local)))
7583 sgs->group_type = group_other;
7585 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7587 sds->busiest_stat = *sgs;
7591 /* Now, start updating sd_lb_stats */
7592 sds->total_load += sgs->group_load;
7593 sds->total_capacity += sgs->group_capacity;
7596 } while (sg != env->sd->groups);
7598 if (env->sd->flags & SD_NUMA)
7599 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7601 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
7603 if (!env->sd->parent) {
7604 /* update overload indicator if we are at root domain */
7605 if (env->dst_rq->rd->overload != overload)
7606 env->dst_rq->rd->overload = overload;
7608 /* Update over-utilization (tipping point, U >= 0) indicator */
7609 if (env->dst_rq->rd->overutilized != overutilized) {
7610 env->dst_rq->rd->overutilized = overutilized;
7611 trace_sched_overutilized(overutilized);
7614 if (!env->dst_rq->rd->overutilized && overutilized) {
7615 env->dst_rq->rd->overutilized = true;
7616 trace_sched_overutilized(true);
7623 * check_asym_packing - Check to see if the group is packed into the
7626 * This is primarily intended to used at the sibling level. Some
7627 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7628 * case of POWER7, it can move to lower SMT modes only when higher
7629 * threads are idle. When in lower SMT modes, the threads will
7630 * perform better since they share less core resources. Hence when we
7631 * have idle threads, we want them to be the higher ones.
7633 * This packing function is run on idle threads. It checks to see if
7634 * the busiest CPU in this domain (core in the P7 case) has a higher
7635 * CPU number than the packing function is being run on. Here we are
7636 * assuming lower CPU number will be equivalent to lower a SMT thread
7639 * Return: 1 when packing is required and a task should be moved to
7640 * this CPU. The amount of the imbalance is returned in *imbalance.
7642 * @env: The load balancing environment.
7643 * @sds: Statistics of the sched_domain which is to be packed
7645 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7649 if (!(env->sd->flags & SD_ASYM_PACKING))
7655 busiest_cpu = group_first_cpu(sds->busiest);
7656 if (env->dst_cpu > busiest_cpu)
7659 env->imbalance = DIV_ROUND_CLOSEST(
7660 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7661 SCHED_CAPACITY_SCALE);
7667 * fix_small_imbalance - Calculate the minor imbalance that exists
7668 * amongst the groups of a sched_domain, during
7670 * @env: The load balancing environment.
7671 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7674 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7676 unsigned long tmp, capa_now = 0, capa_move = 0;
7677 unsigned int imbn = 2;
7678 unsigned long scaled_busy_load_per_task;
7679 struct sg_lb_stats *local, *busiest;
7681 local = &sds->local_stat;
7682 busiest = &sds->busiest_stat;
7684 if (!local->sum_nr_running)
7685 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7686 else if (busiest->load_per_task > local->load_per_task)
7689 scaled_busy_load_per_task =
7690 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7691 busiest->group_capacity;
7693 if (busiest->avg_load + scaled_busy_load_per_task >=
7694 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7695 env->imbalance = busiest->load_per_task;
7700 * OK, we don't have enough imbalance to justify moving tasks,
7701 * however we may be able to increase total CPU capacity used by
7705 capa_now += busiest->group_capacity *
7706 min(busiest->load_per_task, busiest->avg_load);
7707 capa_now += local->group_capacity *
7708 min(local->load_per_task, local->avg_load);
7709 capa_now /= SCHED_CAPACITY_SCALE;
7711 /* Amount of load we'd subtract */
7712 if (busiest->avg_load > scaled_busy_load_per_task) {
7713 capa_move += busiest->group_capacity *
7714 min(busiest->load_per_task,
7715 busiest->avg_load - scaled_busy_load_per_task);
7718 /* Amount of load we'd add */
7719 if (busiest->avg_load * busiest->group_capacity <
7720 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7721 tmp = (busiest->avg_load * busiest->group_capacity) /
7722 local->group_capacity;
7724 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7725 local->group_capacity;
7727 capa_move += local->group_capacity *
7728 min(local->load_per_task, local->avg_load + tmp);
7729 capa_move /= SCHED_CAPACITY_SCALE;
7731 /* Move if we gain throughput */
7732 if (capa_move > capa_now)
7733 env->imbalance = busiest->load_per_task;
7737 * calculate_imbalance - Calculate the amount of imbalance present within the
7738 * groups of a given sched_domain during load balance.
7739 * @env: load balance environment
7740 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7742 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7744 unsigned long max_pull, load_above_capacity = ~0UL;
7745 struct sg_lb_stats *local, *busiest;
7747 local = &sds->local_stat;
7748 busiest = &sds->busiest_stat;
7750 if (busiest->group_type == group_imbalanced) {
7752 * In the group_imb case we cannot rely on group-wide averages
7753 * to ensure cpu-load equilibrium, look at wider averages. XXX
7755 busiest->load_per_task =
7756 min(busiest->load_per_task, sds->avg_load);
7760 * In the presence of smp nice balancing, certain scenarios can have
7761 * max load less than avg load(as we skip the groups at or below
7762 * its cpu_capacity, while calculating max_load..)
7764 if (busiest->avg_load <= sds->avg_load ||
7765 local->avg_load >= sds->avg_load) {
7766 /* Misfitting tasks should be migrated in any case */
7767 if (busiest->group_type == group_misfit_task) {
7768 env->imbalance = busiest->group_misfit_task;
7773 * Busiest group is overloaded, local is not, use the spare
7774 * cycles to maximize throughput
7776 if (busiest->group_type == group_overloaded &&
7777 local->group_type <= group_misfit_task) {
7778 env->imbalance = busiest->load_per_task;
7783 return fix_small_imbalance(env, sds);
7787 * If there aren't any idle cpus, avoid creating some.
7789 if (busiest->group_type == group_overloaded &&
7790 local->group_type == group_overloaded) {
7791 load_above_capacity = busiest->sum_nr_running *
7793 if (load_above_capacity > busiest->group_capacity)
7794 load_above_capacity -= busiest->group_capacity;
7796 load_above_capacity = ~0UL;
7800 * We're trying to get all the cpus to the average_load, so we don't
7801 * want to push ourselves above the average load, nor do we wish to
7802 * reduce the max loaded cpu below the average load. At the same time,
7803 * we also don't want to reduce the group load below the group capacity
7804 * (so that we can implement power-savings policies etc). Thus we look
7805 * for the minimum possible imbalance.
7807 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7809 /* How much load to actually move to equalise the imbalance */
7810 env->imbalance = min(
7811 max_pull * busiest->group_capacity,
7812 (sds->avg_load - local->avg_load) * local->group_capacity
7813 ) / SCHED_CAPACITY_SCALE;
7815 /* Boost imbalance to allow misfit task to be balanced. */
7816 if (busiest->group_type == group_misfit_task)
7817 env->imbalance = max_t(long, env->imbalance,
7818 busiest->group_misfit_task);
7821 * if *imbalance is less than the average load per runnable task
7822 * there is no guarantee that any tasks will be moved so we'll have
7823 * a think about bumping its value to force at least one task to be
7826 if (env->imbalance < busiest->load_per_task)
7827 return fix_small_imbalance(env, sds);
7830 /******* find_busiest_group() helpers end here *********************/
7833 * find_busiest_group - Returns the busiest group within the sched_domain
7834 * if there is an imbalance. If there isn't an imbalance, and
7835 * the user has opted for power-savings, it returns a group whose
7836 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7837 * such a group exists.
7839 * Also calculates the amount of weighted load which should be moved
7840 * to restore balance.
7842 * @env: The load balancing environment.
7844 * Return: - The busiest group if imbalance exists.
7845 * - If no imbalance and user has opted for power-savings balance,
7846 * return the least loaded group whose CPUs can be
7847 * put to idle by rebalancing its tasks onto our group.
7849 static struct sched_group *find_busiest_group(struct lb_env *env)
7851 struct sg_lb_stats *local, *busiest;
7852 struct sd_lb_stats sds;
7854 init_sd_lb_stats(&sds);
7857 * Compute the various statistics relavent for load balancing at
7860 update_sd_lb_stats(env, &sds);
7862 if (energy_aware() && !env->dst_rq->rd->overutilized)
7865 local = &sds.local_stat;
7866 busiest = &sds.busiest_stat;
7868 /* ASYM feature bypasses nice load balance check */
7869 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7870 check_asym_packing(env, &sds))
7873 /* There is no busy sibling group to pull tasks from */
7874 if (!sds.busiest || busiest->sum_nr_running == 0)
7877 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7878 / sds.total_capacity;
7881 * If the busiest group is imbalanced the below checks don't
7882 * work because they assume all things are equal, which typically
7883 * isn't true due to cpus_allowed constraints and the like.
7885 if (busiest->group_type == group_imbalanced)
7888 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7889 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7890 busiest->group_no_capacity)
7893 /* Misfitting tasks should be dealt with regardless of the avg load */
7894 if (busiest->group_type == group_misfit_task) {
7899 * If the local group is busier than the selected busiest group
7900 * don't try and pull any tasks.
7902 if (local->avg_load >= busiest->avg_load)
7906 * Don't pull any tasks if this group is already above the domain
7909 if (local->avg_load >= sds.avg_load)
7912 if (env->idle == CPU_IDLE) {
7914 * This cpu is idle. If the busiest group is not overloaded
7915 * and there is no imbalance between this and busiest group
7916 * wrt idle cpus, it is balanced. The imbalance becomes
7917 * significant if the diff is greater than 1 otherwise we
7918 * might end up to just move the imbalance on another group
7920 if ((busiest->group_type != group_overloaded) &&
7921 (local->idle_cpus <= (busiest->idle_cpus + 1)) &&
7922 !group_smaller_cpu_capacity(sds.busiest, sds.local))
7926 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7927 * imbalance_pct to be conservative.
7929 if (100 * busiest->avg_load <=
7930 env->sd->imbalance_pct * local->avg_load)
7935 env->busiest_group_type = busiest->group_type;
7936 /* Looks like there is an imbalance. Compute it */
7937 calculate_imbalance(env, &sds);
7946 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7948 static struct rq *find_busiest_queue(struct lb_env *env,
7949 struct sched_group *group)
7951 struct rq *busiest = NULL, *rq;
7952 unsigned long busiest_load = 0, busiest_capacity = 1;
7955 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7956 unsigned long capacity, wl;
7960 rt = fbq_classify_rq(rq);
7963 * We classify groups/runqueues into three groups:
7964 * - regular: there are !numa tasks
7965 * - remote: there are numa tasks that run on the 'wrong' node
7966 * - all: there is no distinction
7968 * In order to avoid migrating ideally placed numa tasks,
7969 * ignore those when there's better options.
7971 * If we ignore the actual busiest queue to migrate another
7972 * task, the next balance pass can still reduce the busiest
7973 * queue by moving tasks around inside the node.
7975 * If we cannot move enough load due to this classification
7976 * the next pass will adjust the group classification and
7977 * allow migration of more tasks.
7979 * Both cases only affect the total convergence complexity.
7981 if (rt > env->fbq_type)
7984 capacity = capacity_of(i);
7986 wl = weighted_cpuload(i);
7989 * When comparing with imbalance, use weighted_cpuload()
7990 * which is not scaled with the cpu capacity.
7993 if (rq->nr_running == 1 && wl > env->imbalance &&
7994 !check_cpu_capacity(rq, env->sd) &&
7995 env->busiest_group_type != group_misfit_task)
7999 * For the load comparisons with the other cpu's, consider
8000 * the weighted_cpuload() scaled with the cpu capacity, so
8001 * that the load can be moved away from the cpu that is
8002 * potentially running at a lower capacity.
8004 * Thus we're looking for max(wl_i / capacity_i), crosswise
8005 * multiplication to rid ourselves of the division works out
8006 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
8007 * our previous maximum.
8009 if (wl * busiest_capacity > busiest_load * capacity) {
8011 busiest_capacity = capacity;
8020 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
8021 * so long as it is large enough.
8023 #define MAX_PINNED_INTERVAL 512
8025 /* Working cpumask for load_balance and load_balance_newidle. */
8026 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
8028 static int need_active_balance(struct lb_env *env)
8030 struct sched_domain *sd = env->sd;
8032 if (env->idle == CPU_NEWLY_IDLE) {
8035 * ASYM_PACKING needs to force migrate tasks from busy but
8036 * higher numbered CPUs in order to pack all tasks in the
8037 * lowest numbered CPUs.
8039 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
8044 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
8045 * It's worth migrating the task if the src_cpu's capacity is reduced
8046 * because of other sched_class or IRQs if more capacity stays
8047 * available on dst_cpu.
8049 if ((env->idle != CPU_NOT_IDLE) &&
8050 (env->src_rq->cfs.h_nr_running == 1)) {
8051 if ((check_cpu_capacity(env->src_rq, sd)) &&
8052 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
8056 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
8057 env->src_rq->cfs.h_nr_running == 1 &&
8058 cpu_overutilized(env->src_cpu) &&
8059 !cpu_overutilized(env->dst_cpu)) {
8063 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
8066 static int active_load_balance_cpu_stop(void *data);
8068 static int should_we_balance(struct lb_env *env)
8070 struct sched_group *sg = env->sd->groups;
8071 struct cpumask *sg_cpus, *sg_mask;
8072 int cpu, balance_cpu = -1;
8075 * In the newly idle case, we will allow all the cpu's
8076 * to do the newly idle load balance.
8078 if (env->idle == CPU_NEWLY_IDLE)
8081 sg_cpus = sched_group_cpus(sg);
8082 sg_mask = sched_group_mask(sg);
8083 /* Try to find first idle cpu */
8084 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
8085 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
8092 if (balance_cpu == -1)
8093 balance_cpu = group_balance_cpu(sg);
8096 * First idle cpu or the first cpu(busiest) in this sched group
8097 * is eligible for doing load balancing at this and above domains.
8099 return balance_cpu == env->dst_cpu;
8103 * Check this_cpu to ensure it is balanced within domain. Attempt to move
8104 * tasks if there is an imbalance.
8106 static int load_balance(int this_cpu, struct rq *this_rq,
8107 struct sched_domain *sd, enum cpu_idle_type idle,
8108 int *continue_balancing)
8110 int ld_moved, cur_ld_moved, active_balance = 0;
8111 struct sched_domain *sd_parent = sd->parent;
8112 struct sched_group *group;
8114 unsigned long flags;
8115 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8117 struct lb_env env = {
8119 .dst_cpu = this_cpu,
8121 .dst_grpmask = sched_group_cpus(sd->groups),
8123 .loop_break = sched_nr_migrate_break,
8126 .tasks = LIST_HEAD_INIT(env.tasks),
8130 * For NEWLY_IDLE load_balancing, we don't need to consider
8131 * other cpus in our group
8133 if (idle == CPU_NEWLY_IDLE)
8134 env.dst_grpmask = NULL;
8136 cpumask_copy(cpus, cpu_active_mask);
8138 schedstat_inc(sd, lb_count[idle]);
8141 if (!should_we_balance(&env)) {
8142 *continue_balancing = 0;
8146 group = find_busiest_group(&env);
8148 schedstat_inc(sd, lb_nobusyg[idle]);
8152 busiest = find_busiest_queue(&env, group);
8154 schedstat_inc(sd, lb_nobusyq[idle]);
8158 BUG_ON(busiest == env.dst_rq);
8160 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
8162 env.src_cpu = busiest->cpu;
8163 env.src_rq = busiest;
8166 if (busiest->nr_running > 1) {
8168 * Attempt to move tasks. If find_busiest_group has found
8169 * an imbalance but busiest->nr_running <= 1, the group is
8170 * still unbalanced. ld_moved simply stays zero, so it is
8171 * correctly treated as an imbalance.
8173 env.flags |= LBF_ALL_PINNED;
8174 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
8177 raw_spin_lock_irqsave(&busiest->lock, flags);
8180 * cur_ld_moved - load moved in current iteration
8181 * ld_moved - cumulative load moved across iterations
8183 cur_ld_moved = detach_tasks(&env);
8185 * We want to potentially lower env.src_cpu's OPP.
8188 update_capacity_of(env.src_cpu);
8191 * We've detached some tasks from busiest_rq. Every
8192 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
8193 * unlock busiest->lock, and we are able to be sure
8194 * that nobody can manipulate the tasks in parallel.
8195 * See task_rq_lock() family for the details.
8198 raw_spin_unlock(&busiest->lock);
8202 ld_moved += cur_ld_moved;
8205 local_irq_restore(flags);
8207 if (env.flags & LBF_NEED_BREAK) {
8208 env.flags &= ~LBF_NEED_BREAK;
8213 * Revisit (affine) tasks on src_cpu that couldn't be moved to
8214 * us and move them to an alternate dst_cpu in our sched_group
8215 * where they can run. The upper limit on how many times we
8216 * iterate on same src_cpu is dependent on number of cpus in our
8219 * This changes load balance semantics a bit on who can move
8220 * load to a given_cpu. In addition to the given_cpu itself
8221 * (or a ilb_cpu acting on its behalf where given_cpu is
8222 * nohz-idle), we now have balance_cpu in a position to move
8223 * load to given_cpu. In rare situations, this may cause
8224 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
8225 * _independently_ and at _same_ time to move some load to
8226 * given_cpu) causing exceess load to be moved to given_cpu.
8227 * This however should not happen so much in practice and
8228 * moreover subsequent load balance cycles should correct the
8229 * excess load moved.
8231 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8233 /* Prevent to re-select dst_cpu via env's cpus */
8234 cpumask_clear_cpu(env.dst_cpu, env.cpus);
8236 env.dst_rq = cpu_rq(env.new_dst_cpu);
8237 env.dst_cpu = env.new_dst_cpu;
8238 env.flags &= ~LBF_DST_PINNED;
8240 env.loop_break = sched_nr_migrate_break;
8243 * Go back to "more_balance" rather than "redo" since we
8244 * need to continue with same src_cpu.
8250 * We failed to reach balance because of affinity.
8253 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8255 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8256 *group_imbalance = 1;
8259 /* All tasks on this runqueue were pinned by CPU affinity */
8260 if (unlikely(env.flags & LBF_ALL_PINNED)) {
8261 cpumask_clear_cpu(cpu_of(busiest), cpus);
8262 if (!cpumask_empty(cpus)) {
8264 env.loop_break = sched_nr_migrate_break;
8267 goto out_all_pinned;
8272 schedstat_inc(sd, lb_failed[idle]);
8274 * Increment the failure counter only on periodic balance.
8275 * We do not want newidle balance, which can be very
8276 * frequent, pollute the failure counter causing
8277 * excessive cache_hot migrations and active balances.
8279 if (idle != CPU_NEWLY_IDLE)
8280 if (env.src_grp_nr_running > 1)
8281 sd->nr_balance_failed++;
8283 if (need_active_balance(&env)) {
8284 raw_spin_lock_irqsave(&busiest->lock, flags);
8286 /* don't kick the active_load_balance_cpu_stop,
8287 * if the curr task on busiest cpu can't be
8290 if (!cpumask_test_cpu(this_cpu,
8291 tsk_cpus_allowed(busiest->curr))) {
8292 raw_spin_unlock_irqrestore(&busiest->lock,
8294 env.flags |= LBF_ALL_PINNED;
8295 goto out_one_pinned;
8299 * ->active_balance synchronizes accesses to
8300 * ->active_balance_work. Once set, it's cleared
8301 * only after active load balance is finished.
8303 if (!busiest->active_balance) {
8304 busiest->active_balance = 1;
8305 busiest->push_cpu = this_cpu;
8308 raw_spin_unlock_irqrestore(&busiest->lock, flags);
8310 if (active_balance) {
8311 stop_one_cpu_nowait(cpu_of(busiest),
8312 active_load_balance_cpu_stop, busiest,
8313 &busiest->active_balance_work);
8317 * We've kicked active balancing, reset the failure
8320 sd->nr_balance_failed = sd->cache_nice_tries+1;
8323 sd->nr_balance_failed = 0;
8325 if (likely(!active_balance)) {
8326 /* We were unbalanced, so reset the balancing interval */
8327 sd->balance_interval = sd->min_interval;
8330 * If we've begun active balancing, start to back off. This
8331 * case may not be covered by the all_pinned logic if there
8332 * is only 1 task on the busy runqueue (because we don't call
8335 if (sd->balance_interval < sd->max_interval)
8336 sd->balance_interval *= 2;
8343 * We reach balance although we may have faced some affinity
8344 * constraints. Clear the imbalance flag if it was set.
8347 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8349 if (*group_imbalance)
8350 *group_imbalance = 0;
8355 * We reach balance because all tasks are pinned at this level so
8356 * we can't migrate them. Let the imbalance flag set so parent level
8357 * can try to migrate them.
8359 schedstat_inc(sd, lb_balanced[idle]);
8361 sd->nr_balance_failed = 0;
8364 /* tune up the balancing interval */
8365 if (((env.flags & LBF_ALL_PINNED) &&
8366 sd->balance_interval < MAX_PINNED_INTERVAL) ||
8367 (sd->balance_interval < sd->max_interval))
8368 sd->balance_interval *= 2;
8375 static inline unsigned long
8376 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
8378 unsigned long interval = sd->balance_interval;
8381 interval *= sd->busy_factor;
8383 /* scale ms to jiffies */
8384 interval = msecs_to_jiffies(interval);
8385 interval = clamp(interval, 1UL, max_load_balance_interval);
8391 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
8393 unsigned long interval, next;
8395 interval = get_sd_balance_interval(sd, cpu_busy);
8396 next = sd->last_balance + interval;
8398 if (time_after(*next_balance, next))
8399 *next_balance = next;
8403 * idle_balance is called by schedule() if this_cpu is about to become
8404 * idle. Attempts to pull tasks from other CPUs.
8406 static int idle_balance(struct rq *this_rq)
8408 unsigned long next_balance = jiffies + HZ;
8409 int this_cpu = this_rq->cpu;
8410 struct sched_domain *sd;
8411 int pulled_task = 0;
8413 long removed_util=0;
8415 idle_enter_fair(this_rq);
8418 * We must set idle_stamp _before_ calling idle_balance(), such that we
8419 * measure the duration of idle_balance() as idle time.
8421 this_rq->idle_stamp = rq_clock(this_rq);
8423 if (!energy_aware() &&
8424 (this_rq->avg_idle < sysctl_sched_migration_cost ||
8425 !this_rq->rd->overload)) {
8427 sd = rcu_dereference_check_sched_domain(this_rq->sd);
8429 update_next_balance(sd, 0, &next_balance);
8435 raw_spin_unlock(&this_rq->lock);
8438 * If removed_util_avg is !0 we most probably migrated some task away
8439 * from this_cpu. In this case we might be willing to trigger an OPP
8440 * update, but we want to do so if we don't find anybody else to pull
8441 * here (we will trigger an OPP update with the pulled task's enqueue
8444 * Record removed_util before calling update_blocked_averages, and use
8445 * it below (before returning) to see if an OPP update is required.
8447 removed_util = atomic_long_read(&(this_rq->cfs).removed_util_avg);
8448 update_blocked_averages(this_cpu);
8450 for_each_domain(this_cpu, sd) {
8451 int continue_balancing = 1;
8452 u64 t0, domain_cost;
8454 if (!(sd->flags & SD_LOAD_BALANCE))
8457 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8458 update_next_balance(sd, 0, &next_balance);
8462 if (sd->flags & SD_BALANCE_NEWIDLE) {
8463 t0 = sched_clock_cpu(this_cpu);
8465 pulled_task = load_balance(this_cpu, this_rq,
8467 &continue_balancing);
8469 domain_cost = sched_clock_cpu(this_cpu) - t0;
8470 if (domain_cost > sd->max_newidle_lb_cost)
8471 sd->max_newidle_lb_cost = domain_cost;
8473 curr_cost += domain_cost;
8476 update_next_balance(sd, 0, &next_balance);
8479 * Stop searching for tasks to pull if there are
8480 * now runnable tasks on this rq.
8482 if (pulled_task || this_rq->nr_running > 0)
8487 raw_spin_lock(&this_rq->lock);
8489 if (curr_cost > this_rq->max_idle_balance_cost)
8490 this_rq->max_idle_balance_cost = curr_cost;
8493 * While browsing the domains, we released the rq lock, a task could
8494 * have been enqueued in the meantime. Since we're not going idle,
8495 * pretend we pulled a task.
8497 if (this_rq->cfs.h_nr_running && !pulled_task)
8501 /* Move the next balance forward */
8502 if (time_after(this_rq->next_balance, next_balance))
8503 this_rq->next_balance = next_balance;
8505 /* Is there a task of a high priority class? */
8506 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8510 idle_exit_fair(this_rq);
8511 this_rq->idle_stamp = 0;
8512 } else if (removed_util) {
8514 * No task pulled and someone has been migrated away.
8515 * Good case to trigger an OPP update.
8517 update_capacity_of(this_cpu);
8524 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8525 * running tasks off the busiest CPU onto idle CPUs. It requires at
8526 * least 1 task to be running on each physical CPU where possible, and
8527 * avoids physical / logical imbalances.
8529 static int active_load_balance_cpu_stop(void *data)
8531 struct rq *busiest_rq = data;
8532 int busiest_cpu = cpu_of(busiest_rq);
8533 int target_cpu = busiest_rq->push_cpu;
8534 struct rq *target_rq = cpu_rq(target_cpu);
8535 struct sched_domain *sd;
8536 struct task_struct *p = NULL;
8538 raw_spin_lock_irq(&busiest_rq->lock);
8540 /* make sure the requested cpu hasn't gone down in the meantime */
8541 if (unlikely(busiest_cpu != smp_processor_id() ||
8542 !busiest_rq->active_balance))
8545 /* Is there any task to move? */
8546 if (busiest_rq->nr_running <= 1)
8550 * This condition is "impossible", if it occurs
8551 * we need to fix it. Originally reported by
8552 * Bjorn Helgaas on a 128-cpu setup.
8554 BUG_ON(busiest_rq == target_rq);
8556 /* Search for an sd spanning us and the target CPU. */
8558 for_each_domain(target_cpu, sd) {
8559 if ((sd->flags & SD_LOAD_BALANCE) &&
8560 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8565 struct lb_env env = {
8567 .dst_cpu = target_cpu,
8568 .dst_rq = target_rq,
8569 .src_cpu = busiest_rq->cpu,
8570 .src_rq = busiest_rq,
8574 schedstat_inc(sd, alb_count);
8576 p = detach_one_task(&env);
8578 schedstat_inc(sd, alb_pushed);
8580 * We want to potentially lower env.src_cpu's OPP.
8582 update_capacity_of(env.src_cpu);
8585 schedstat_inc(sd, alb_failed);
8589 busiest_rq->active_balance = 0;
8590 raw_spin_unlock(&busiest_rq->lock);
8593 attach_one_task(target_rq, p);
8600 static inline int on_null_domain(struct rq *rq)
8602 return unlikely(!rcu_dereference_sched(rq->sd));
8605 #ifdef CONFIG_NO_HZ_COMMON
8607 * idle load balancing details
8608 * - When one of the busy CPUs notice that there may be an idle rebalancing
8609 * needed, they will kick the idle load balancer, which then does idle
8610 * load balancing for all the idle CPUs.
8613 cpumask_var_t idle_cpus_mask;
8615 unsigned long next_balance; /* in jiffy units */
8616 } nohz ____cacheline_aligned;
8618 static inline int find_new_ilb(void)
8620 int ilb = cpumask_first(nohz.idle_cpus_mask);
8622 if (ilb < nr_cpu_ids && idle_cpu(ilb))
8629 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8630 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8631 * CPU (if there is one).
8633 static void nohz_balancer_kick(void)
8637 nohz.next_balance++;
8639 ilb_cpu = find_new_ilb();
8641 if (ilb_cpu >= nr_cpu_ids)
8644 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8647 * Use smp_send_reschedule() instead of resched_cpu().
8648 * This way we generate a sched IPI on the target cpu which
8649 * is idle. And the softirq performing nohz idle load balance
8650 * will be run before returning from the IPI.
8652 smp_send_reschedule(ilb_cpu);
8656 static inline void nohz_balance_exit_idle(int cpu)
8658 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8660 * Completely isolated CPUs don't ever set, so we must test.
8662 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8663 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8664 atomic_dec(&nohz.nr_cpus);
8666 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8670 static inline void set_cpu_sd_state_busy(void)
8672 struct sched_domain *sd;
8673 int cpu = smp_processor_id();
8676 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8678 if (!sd || !sd->nohz_idle)
8682 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
8687 void set_cpu_sd_state_idle(void)
8689 struct sched_domain *sd;
8690 int cpu = smp_processor_id();
8693 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8695 if (!sd || sd->nohz_idle)
8699 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8705 * This routine will record that the cpu is going idle with tick stopped.
8706 * This info will be used in performing idle load balancing in the future.
8708 void nohz_balance_enter_idle(int cpu)
8711 * If this cpu is going down, then nothing needs to be done.
8713 if (!cpu_active(cpu))
8716 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8720 * If we're a completely isolated CPU, we don't play.
8722 if (on_null_domain(cpu_rq(cpu)))
8725 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8726 atomic_inc(&nohz.nr_cpus);
8727 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8730 static int sched_ilb_notifier(struct notifier_block *nfb,
8731 unsigned long action, void *hcpu)
8733 switch (action & ~CPU_TASKS_FROZEN) {
8735 nohz_balance_exit_idle(smp_processor_id());
8743 static DEFINE_SPINLOCK(balancing);
8746 * Scale the max load_balance interval with the number of CPUs in the system.
8747 * This trades load-balance latency on larger machines for less cross talk.
8749 void update_max_interval(void)
8751 max_load_balance_interval = HZ*num_online_cpus()/10;
8755 * It checks each scheduling domain to see if it is due to be balanced,
8756 * and initiates a balancing operation if so.
8758 * Balancing parameters are set up in init_sched_domains.
8760 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8762 int continue_balancing = 1;
8764 unsigned long interval;
8765 struct sched_domain *sd;
8766 /* Earliest time when we have to do rebalance again */
8767 unsigned long next_balance = jiffies + 60*HZ;
8768 int update_next_balance = 0;
8769 int need_serialize, need_decay = 0;
8772 update_blocked_averages(cpu);
8775 for_each_domain(cpu, sd) {
8777 * Decay the newidle max times here because this is a regular
8778 * visit to all the domains. Decay ~1% per second.
8780 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8781 sd->max_newidle_lb_cost =
8782 (sd->max_newidle_lb_cost * 253) / 256;
8783 sd->next_decay_max_lb_cost = jiffies + HZ;
8786 max_cost += sd->max_newidle_lb_cost;
8788 if (!(sd->flags & SD_LOAD_BALANCE))
8792 * Stop the load balance at this level. There is another
8793 * CPU in our sched group which is doing load balancing more
8796 if (!continue_balancing) {
8802 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8804 need_serialize = sd->flags & SD_SERIALIZE;
8805 if (need_serialize) {
8806 if (!spin_trylock(&balancing))
8810 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8811 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8813 * The LBF_DST_PINNED logic could have changed
8814 * env->dst_cpu, so we can't know our idle
8815 * state even if we migrated tasks. Update it.
8817 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8819 sd->last_balance = jiffies;
8820 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8823 spin_unlock(&balancing);
8825 if (time_after(next_balance, sd->last_balance + interval)) {
8826 next_balance = sd->last_balance + interval;
8827 update_next_balance = 1;
8832 * Ensure the rq-wide value also decays but keep it at a
8833 * reasonable floor to avoid funnies with rq->avg_idle.
8835 rq->max_idle_balance_cost =
8836 max((u64)sysctl_sched_migration_cost, max_cost);
8841 * next_balance will be updated only when there is a need.
8842 * When the cpu is attached to null domain for ex, it will not be
8845 if (likely(update_next_balance)) {
8846 rq->next_balance = next_balance;
8848 #ifdef CONFIG_NO_HZ_COMMON
8850 * If this CPU has been elected to perform the nohz idle
8851 * balance. Other idle CPUs have already rebalanced with
8852 * nohz_idle_balance() and nohz.next_balance has been
8853 * updated accordingly. This CPU is now running the idle load
8854 * balance for itself and we need to update the
8855 * nohz.next_balance accordingly.
8857 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8858 nohz.next_balance = rq->next_balance;
8863 #ifdef CONFIG_NO_HZ_COMMON
8865 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8866 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8868 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8870 int this_cpu = this_rq->cpu;
8873 /* Earliest time when we have to do rebalance again */
8874 unsigned long next_balance = jiffies + 60*HZ;
8875 int update_next_balance = 0;
8877 if (idle != CPU_IDLE ||
8878 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8881 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8882 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8886 * If this cpu gets work to do, stop the load balancing
8887 * work being done for other cpus. Next load
8888 * balancing owner will pick it up.
8893 rq = cpu_rq(balance_cpu);
8896 * If time for next balance is due,
8899 if (time_after_eq(jiffies, rq->next_balance)) {
8900 raw_spin_lock_irq(&rq->lock);
8901 update_rq_clock(rq);
8902 update_idle_cpu_load(rq);
8903 raw_spin_unlock_irq(&rq->lock);
8904 rebalance_domains(rq, CPU_IDLE);
8907 if (time_after(next_balance, rq->next_balance)) {
8908 next_balance = rq->next_balance;
8909 update_next_balance = 1;
8914 * next_balance will be updated only when there is a need.
8915 * When the CPU is attached to null domain for ex, it will not be
8918 if (likely(update_next_balance))
8919 nohz.next_balance = next_balance;
8921 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8925 * Current heuristic for kicking the idle load balancer in the presence
8926 * of an idle cpu in the system.
8927 * - This rq has more than one task.
8928 * - This rq has at least one CFS task and the capacity of the CPU is
8929 * significantly reduced because of RT tasks or IRQs.
8930 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8931 * multiple busy cpu.
8932 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8933 * domain span are idle.
8935 static inline bool nohz_kick_needed(struct rq *rq)
8937 unsigned long now = jiffies;
8938 struct sched_domain *sd;
8939 struct sched_group_capacity *sgc;
8940 int nr_busy, cpu = rq->cpu;
8943 if (unlikely(rq->idle_balance))
8947 * We may be recently in ticked or tickless idle mode. At the first
8948 * busy tick after returning from idle, we will update the busy stats.
8950 set_cpu_sd_state_busy();
8951 nohz_balance_exit_idle(cpu);
8954 * None are in tickless mode and hence no need for NOHZ idle load
8957 if (likely(!atomic_read(&nohz.nr_cpus)))
8960 if (time_before(now, nohz.next_balance))
8963 if (rq->nr_running >= 2 &&
8964 (!energy_aware() || cpu_overutilized(cpu)))
8968 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8969 if (sd && !energy_aware()) {
8970 sgc = sd->groups->sgc;
8971 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8980 sd = rcu_dereference(rq->sd);
8982 if ((rq->cfs.h_nr_running >= 1) &&
8983 check_cpu_capacity(rq, sd)) {
8989 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8990 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8991 sched_domain_span(sd)) < cpu)) {
9001 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
9005 * run_rebalance_domains is triggered when needed from the scheduler tick.
9006 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
9008 static void run_rebalance_domains(struct softirq_action *h)
9010 struct rq *this_rq = this_rq();
9011 enum cpu_idle_type idle = this_rq->idle_balance ?
9012 CPU_IDLE : CPU_NOT_IDLE;
9015 * If this cpu has a pending nohz_balance_kick, then do the
9016 * balancing on behalf of the other idle cpus whose ticks are
9017 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9018 * give the idle cpus a chance to load balance. Else we may
9019 * load balance only within the local sched_domain hierarchy
9020 * and abort nohz_idle_balance altogether if we pull some load.
9022 nohz_idle_balance(this_rq, idle);
9023 rebalance_domains(this_rq, idle);
9027 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
9029 void trigger_load_balance(struct rq *rq)
9031 /* Don't need to rebalance while attached to NULL domain */
9032 if (unlikely(on_null_domain(rq)))
9035 if (time_after_eq(jiffies, rq->next_balance))
9036 raise_softirq(SCHED_SOFTIRQ);
9037 #ifdef CONFIG_NO_HZ_COMMON
9038 if (nohz_kick_needed(rq))
9039 nohz_balancer_kick();
9043 static void rq_online_fair(struct rq *rq)
9047 update_runtime_enabled(rq);
9050 static void rq_offline_fair(struct rq *rq)
9054 /* Ensure any throttled groups are reachable by pick_next_task */
9055 unthrottle_offline_cfs_rqs(rq);
9058 #endif /* CONFIG_SMP */
9061 * scheduler tick hitting a task of our scheduling class:
9063 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9065 struct cfs_rq *cfs_rq;
9066 struct sched_entity *se = &curr->se;
9068 for_each_sched_entity(se) {
9069 cfs_rq = cfs_rq_of(se);
9070 entity_tick(cfs_rq, se, queued);
9073 if (static_branch_unlikely(&sched_numa_balancing))
9074 task_tick_numa(rq, curr);
9077 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr))) {
9078 rq->rd->overutilized = true;
9079 trace_sched_overutilized(true);
9082 rq->misfit_task = !task_fits_max(curr, rq->cpu);
9088 * called on fork with the child task as argument from the parent's context
9089 * - child not yet on the tasklist
9090 * - preemption disabled
9092 static void task_fork_fair(struct task_struct *p)
9094 struct cfs_rq *cfs_rq;
9095 struct sched_entity *se = &p->se, *curr;
9096 int this_cpu = smp_processor_id();
9097 struct rq *rq = this_rq();
9098 unsigned long flags;
9100 raw_spin_lock_irqsave(&rq->lock, flags);
9102 update_rq_clock(rq);
9104 cfs_rq = task_cfs_rq(current);
9105 curr = cfs_rq->curr;
9108 * Not only the cpu but also the task_group of the parent might have
9109 * been changed after parent->se.parent,cfs_rq were copied to
9110 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
9111 * of child point to valid ones.
9114 __set_task_cpu(p, this_cpu);
9117 update_curr(cfs_rq);
9120 se->vruntime = curr->vruntime;
9121 place_entity(cfs_rq, se, 1);
9123 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
9125 * Upon rescheduling, sched_class::put_prev_task() will place
9126 * 'current' within the tree based on its new key value.
9128 swap(curr->vruntime, se->vruntime);
9132 se->vruntime -= cfs_rq->min_vruntime;
9134 raw_spin_unlock_irqrestore(&rq->lock, flags);
9138 * Priority of the task has changed. Check to see if we preempt
9142 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9144 if (!task_on_rq_queued(p))
9148 * Reschedule if we are currently running on this runqueue and
9149 * our priority decreased, or if we are not currently running on
9150 * this runqueue and our priority is higher than the current's
9152 if (rq->curr == p) {
9153 if (p->prio > oldprio)
9156 check_preempt_curr(rq, p, 0);
9159 static inline bool vruntime_normalized(struct task_struct *p)
9161 struct sched_entity *se = &p->se;
9164 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
9165 * the dequeue_entity(.flags=0) will already have normalized the
9172 * When !on_rq, vruntime of the task has usually NOT been normalized.
9173 * But there are some cases where it has already been normalized:
9175 * - A forked child which is waiting for being woken up by
9176 * wake_up_new_task().
9177 * - A task which has been woken up by try_to_wake_up() and
9178 * waiting for actually being woken up by sched_ttwu_pending().
9180 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
9186 static void detach_task_cfs_rq(struct task_struct *p)
9188 struct sched_entity *se = &p->se;
9189 struct cfs_rq *cfs_rq = cfs_rq_of(se);
9191 if (!vruntime_normalized(p)) {
9193 * Fix up our vruntime so that the current sleep doesn't
9194 * cause 'unlimited' sleep bonus.
9196 place_entity(cfs_rq, se, 0);
9197 se->vruntime -= cfs_rq->min_vruntime;
9200 /* Catch up with the cfs_rq and remove our load when we leave */
9201 detach_entity_load_avg(cfs_rq, se);
9204 static void attach_task_cfs_rq(struct task_struct *p)
9206 struct sched_entity *se = &p->se;
9207 struct cfs_rq *cfs_rq = cfs_rq_of(se);
9209 #ifdef CONFIG_FAIR_GROUP_SCHED
9211 * Since the real-depth could have been changed (only FAIR
9212 * class maintain depth value), reset depth properly.
9214 se->depth = se->parent ? se->parent->depth + 1 : 0;
9217 /* Synchronize task with its cfs_rq */
9218 attach_entity_load_avg(cfs_rq, se);
9220 if (!vruntime_normalized(p))
9221 se->vruntime += cfs_rq->min_vruntime;
9224 static void switched_from_fair(struct rq *rq, struct task_struct *p)
9226 detach_task_cfs_rq(p);
9229 static void switched_to_fair(struct rq *rq, struct task_struct *p)
9231 attach_task_cfs_rq(p);
9233 if (task_on_rq_queued(p)) {
9235 * We were most likely switched from sched_rt, so
9236 * kick off the schedule if running, otherwise just see
9237 * if we can still preempt the current task.
9242 check_preempt_curr(rq, p, 0);
9246 /* Account for a task changing its policy or group.
9248 * This routine is mostly called to set cfs_rq->curr field when a task
9249 * migrates between groups/classes.
9251 static void set_curr_task_fair(struct rq *rq)
9253 struct sched_entity *se = &rq->curr->se;
9255 for_each_sched_entity(se) {
9256 struct cfs_rq *cfs_rq = cfs_rq_of(se);
9258 set_next_entity(cfs_rq, se);
9259 /* ensure bandwidth has been allocated on our new cfs_rq */
9260 account_cfs_rq_runtime(cfs_rq, 0);
9264 void init_cfs_rq(struct cfs_rq *cfs_rq)
9266 cfs_rq->tasks_timeline = RB_ROOT;
9267 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
9268 #ifndef CONFIG_64BIT
9269 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
9272 atomic_long_set(&cfs_rq->removed_load_avg, 0);
9273 atomic_long_set(&cfs_rq->removed_util_avg, 0);
9277 #ifdef CONFIG_FAIR_GROUP_SCHED
9278 static void task_move_group_fair(struct task_struct *p)
9280 detach_task_cfs_rq(p);
9281 set_task_rq(p, task_cpu(p));
9284 /* Tell se's cfs_rq has been changed -- migrated */
9285 p->se.avg.last_update_time = 0;
9287 attach_task_cfs_rq(p);
9290 void free_fair_sched_group(struct task_group *tg)
9294 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
9296 for_each_possible_cpu(i) {
9298 kfree(tg->cfs_rq[i]);
9301 remove_entity_load_avg(tg->se[i]);
9310 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9312 struct cfs_rq *cfs_rq;
9313 struct sched_entity *se;
9316 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
9319 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
9323 tg->shares = NICE_0_LOAD;
9325 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
9327 for_each_possible_cpu(i) {
9328 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
9329 GFP_KERNEL, cpu_to_node(i));
9333 se = kzalloc_node(sizeof(struct sched_entity),
9334 GFP_KERNEL, cpu_to_node(i));
9338 init_cfs_rq(cfs_rq);
9339 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
9340 init_entity_runnable_average(se);
9351 void unregister_fair_sched_group(struct task_group *tg, int cpu)
9353 struct rq *rq = cpu_rq(cpu);
9354 unsigned long flags;
9357 * Only empty task groups can be destroyed; so we can speculatively
9358 * check on_list without danger of it being re-added.
9360 if (!tg->cfs_rq[cpu]->on_list)
9363 raw_spin_lock_irqsave(&rq->lock, flags);
9364 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
9365 raw_spin_unlock_irqrestore(&rq->lock, flags);
9368 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
9369 struct sched_entity *se, int cpu,
9370 struct sched_entity *parent)
9372 struct rq *rq = cpu_rq(cpu);
9376 init_cfs_rq_runtime(cfs_rq);
9378 tg->cfs_rq[cpu] = cfs_rq;
9381 /* se could be NULL for root_task_group */
9386 se->cfs_rq = &rq->cfs;
9389 se->cfs_rq = parent->my_q;
9390 se->depth = parent->depth + 1;
9394 /* guarantee group entities always have weight */
9395 update_load_set(&se->load, NICE_0_LOAD);
9396 se->parent = parent;
9399 static DEFINE_MUTEX(shares_mutex);
9401 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
9404 unsigned long flags;
9407 * We can't change the weight of the root cgroup.
9412 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
9414 mutex_lock(&shares_mutex);
9415 if (tg->shares == shares)
9418 tg->shares = shares;
9419 for_each_possible_cpu(i) {
9420 struct rq *rq = cpu_rq(i);
9421 struct sched_entity *se;
9424 /* Propagate contribution to hierarchy */
9425 raw_spin_lock_irqsave(&rq->lock, flags);
9427 /* Possible calls to update_curr() need rq clock */
9428 update_rq_clock(rq);
9429 for_each_sched_entity(se)
9430 update_cfs_shares(group_cfs_rq(se));
9431 raw_spin_unlock_irqrestore(&rq->lock, flags);
9435 mutex_unlock(&shares_mutex);
9438 #else /* CONFIG_FAIR_GROUP_SCHED */
9440 void free_fair_sched_group(struct task_group *tg) { }
9442 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9447 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
9449 #endif /* CONFIG_FAIR_GROUP_SCHED */
9452 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9454 struct sched_entity *se = &task->se;
9455 unsigned int rr_interval = 0;
9458 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
9461 if (rq->cfs.load.weight)
9462 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9468 * All the scheduling class methods:
9470 const struct sched_class fair_sched_class = {
9471 .next = &idle_sched_class,
9472 .enqueue_task = enqueue_task_fair,
9473 .dequeue_task = dequeue_task_fair,
9474 .yield_task = yield_task_fair,
9475 .yield_to_task = yield_to_task_fair,
9477 .check_preempt_curr = check_preempt_wakeup,
9479 .pick_next_task = pick_next_task_fair,
9480 .put_prev_task = put_prev_task_fair,
9483 .select_task_rq = select_task_rq_fair,
9484 .migrate_task_rq = migrate_task_rq_fair,
9486 .rq_online = rq_online_fair,
9487 .rq_offline = rq_offline_fair,
9489 .task_waking = task_waking_fair,
9490 .task_dead = task_dead_fair,
9491 .set_cpus_allowed = set_cpus_allowed_common,
9494 .set_curr_task = set_curr_task_fair,
9495 .task_tick = task_tick_fair,
9496 .task_fork = task_fork_fair,
9498 .prio_changed = prio_changed_fair,
9499 .switched_from = switched_from_fair,
9500 .switched_to = switched_to_fair,
9502 .get_rr_interval = get_rr_interval_fair,
9504 .update_curr = update_curr_fair,
9506 #ifdef CONFIG_FAIR_GROUP_SCHED
9507 .task_move_group = task_move_group_fair,
9511 #ifdef CONFIG_SCHED_DEBUG
9512 void print_cfs_stats(struct seq_file *m, int cpu)
9514 struct cfs_rq *cfs_rq;
9517 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
9518 print_cfs_rq(m, cpu, cfs_rq);
9522 #ifdef CONFIG_NUMA_BALANCING
9523 void show_numa_stats(struct task_struct *p, struct seq_file *m)
9526 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
9528 for_each_online_node(node) {
9529 if (p->numa_faults) {
9530 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
9531 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
9533 if (p->numa_group) {
9534 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
9535 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
9537 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
9540 #endif /* CONFIG_NUMA_BALANCING */
9541 #endif /* CONFIG_SCHED_DEBUG */
9543 __init void init_sched_fair_class(void)
9546 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9548 #ifdef CONFIG_NO_HZ_COMMON
9549 nohz.next_balance = jiffies;
9550 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9551 cpu_notifier(sched_ilb_notifier, 0);