2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
23 #include <linux/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
40 * Targeted preemption latency for CPU-bound tasks:
41 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
43 * NOTE: this latency value is not the same as the concept of
44 * 'timeslice length' - timeslices in CFS are of variable length
45 * and have no persistent notion like in traditional, time-slice
46 * based scheduling concepts.
48 * (to see the precise effective timeslice length of your workload,
49 * run vmstat and monitor the context-switches (cs) field)
51 unsigned int sysctl_sched_latency = 6000000ULL;
52 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
55 * The initial- and re-scaling of tunables is configurable
56 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
59 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
60 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
61 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
63 enum sched_tunable_scaling sysctl_sched_tunable_scaling
64 = SCHED_TUNABLESCALING_LOG;
67 * Minimal preemption granularity for CPU-bound tasks:
68 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
70 unsigned int sysctl_sched_min_granularity = 750000ULL;
71 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
74 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
76 static unsigned int sched_nr_latency = 8;
79 * After fork, child runs first. If set to 0 (default) then
80 * parent will (try to) run first.
82 unsigned int sysctl_sched_child_runs_first __read_mostly;
85 * SCHED_OTHER wake-up granularity.
86 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
88 * This option delays the preemption effects of decoupled workloads
89 * and reduces their over-scheduling. Synchronous workloads will still
90 * have immediate wakeup/sleep latencies.
92 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
93 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
95 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
98 * The exponential sliding window over which load is averaged for shares
102 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
104 #ifdef CONFIG_CFS_BANDWIDTH
106 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
107 * each time a cfs_rq requests quota.
109 * Note: in the case that the slice exceeds the runtime remaining (either due
110 * to consumption or the quota being specified to be smaller than the slice)
111 * we will always only issue the remaining available time.
113 * default: 5 msec, units: microseconds
115 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
118 static inline void update_load_add(struct load_weight *lw, unsigned long inc)
124 static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
130 static inline void update_load_set(struct load_weight *lw, unsigned long w)
137 * Increase the granularity value when there are more CPUs,
138 * because with more CPUs the 'effective latency' as visible
139 * to users decreases. But the relationship is not linear,
140 * so pick a second-best guess by going with the log2 of the
143 * This idea comes from the SD scheduler of Con Kolivas:
145 static unsigned int get_update_sysctl_factor(void)
147 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
150 switch (sysctl_sched_tunable_scaling) {
151 case SCHED_TUNABLESCALING_NONE:
154 case SCHED_TUNABLESCALING_LINEAR:
157 case SCHED_TUNABLESCALING_LOG:
159 factor = 1 + ilog2(cpus);
166 static void update_sysctl(void)
168 unsigned int factor = get_update_sysctl_factor();
170 #define SET_SYSCTL(name) \
171 (sysctl_##name = (factor) * normalized_sysctl_##name)
172 SET_SYSCTL(sched_min_granularity);
173 SET_SYSCTL(sched_latency);
174 SET_SYSCTL(sched_wakeup_granularity);
178 void sched_init_granularity(void)
183 #define WMULT_CONST (~0U)
184 #define WMULT_SHIFT 32
186 static void __update_inv_weight(struct load_weight *lw)
190 if (likely(lw->inv_weight))
193 w = scale_load_down(lw->weight);
195 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
197 else if (unlikely(!w))
198 lw->inv_weight = WMULT_CONST;
200 lw->inv_weight = WMULT_CONST / w;
204 * delta_exec * weight / lw.weight
206 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
208 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
209 * we're guaranteed shift stays positive because inv_weight is guaranteed to
210 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
212 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
213 * weight/lw.weight <= 1, and therefore our shift will also be positive.
215 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
217 u64 fact = scale_load_down(weight);
218 int shift = WMULT_SHIFT;
220 __update_inv_weight(lw);
222 if (unlikely(fact >> 32)) {
229 /* hint to use a 32x32->64 mul */
230 fact = (u64)(u32)fact * lw->inv_weight;
237 return mul_u64_u32_shr(delta_exec, fact, shift);
241 const struct sched_class fair_sched_class;
243 /**************************************************************
244 * CFS operations on generic schedulable entities:
247 #ifdef CONFIG_FAIR_GROUP_SCHED
249 /* cpu runqueue to which this cfs_rq is attached */
250 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
255 /* An entity is a task if it doesn't "own" a runqueue */
256 #define entity_is_task(se) (!se->my_q)
258 static inline struct task_struct *task_of(struct sched_entity *se)
260 #ifdef CONFIG_SCHED_DEBUG
261 WARN_ON_ONCE(!entity_is_task(se));
263 return container_of(se, struct task_struct, se);
266 /* Walk up scheduling entities hierarchy */
267 #define for_each_sched_entity(se) \
268 for (; se; se = se->parent)
270 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
275 /* runqueue on which this entity is (to be) queued */
276 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
281 /* runqueue "owned" by this group */
282 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
287 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
289 if (!cfs_rq->on_list) {
291 * Ensure we either appear before our parent (if already
292 * enqueued) or force our parent to appear after us when it is
293 * enqueued. The fact that we always enqueue bottom-up
294 * reduces this to two cases.
296 if (cfs_rq->tg->parent &&
297 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
298 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
299 &rq_of(cfs_rq)->leaf_cfs_rq_list);
301 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
302 &rq_of(cfs_rq)->leaf_cfs_rq_list);
309 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
311 if (cfs_rq->on_list) {
312 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
317 /* Iterate thr' all leaf cfs_rq's on a runqueue */
318 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
319 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
321 /* Do the two (enqueued) entities belong to the same group ? */
322 static inline struct cfs_rq *
323 is_same_group(struct sched_entity *se, struct sched_entity *pse)
325 if (se->cfs_rq == pse->cfs_rq)
331 static inline struct sched_entity *parent_entity(struct sched_entity *se)
337 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
339 int se_depth, pse_depth;
342 * preemption test can be made between sibling entities who are in the
343 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
344 * both tasks until we find their ancestors who are siblings of common
348 /* First walk up until both entities are at same depth */
349 se_depth = (*se)->depth;
350 pse_depth = (*pse)->depth;
352 while (se_depth > pse_depth) {
354 *se = parent_entity(*se);
357 while (pse_depth > se_depth) {
359 *pse = parent_entity(*pse);
362 while (!is_same_group(*se, *pse)) {
363 *se = parent_entity(*se);
364 *pse = parent_entity(*pse);
368 #else /* !CONFIG_FAIR_GROUP_SCHED */
370 static inline struct task_struct *task_of(struct sched_entity *se)
372 return container_of(se, struct task_struct, se);
375 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
377 return container_of(cfs_rq, struct rq, cfs);
380 #define entity_is_task(se) 1
382 #define for_each_sched_entity(se) \
383 for (; se; se = NULL)
385 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
387 return &task_rq(p)->cfs;
390 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
392 struct task_struct *p = task_of(se);
393 struct rq *rq = task_rq(p);
398 /* runqueue "owned" by this group */
399 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
404 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
408 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
412 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
413 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
415 static inline struct sched_entity *parent_entity(struct sched_entity *se)
421 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
425 #endif /* CONFIG_FAIR_GROUP_SCHED */
427 static __always_inline
428 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
430 /**************************************************************
431 * Scheduling class tree data structure manipulation methods:
434 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
436 s64 delta = (s64)(vruntime - max_vruntime);
438 max_vruntime = vruntime;
443 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
445 s64 delta = (s64)(vruntime - min_vruntime);
447 min_vruntime = vruntime;
452 static inline int entity_before(struct sched_entity *a,
453 struct sched_entity *b)
455 return (s64)(a->vruntime - b->vruntime) < 0;
458 static void update_min_vruntime(struct cfs_rq *cfs_rq)
460 u64 vruntime = cfs_rq->min_vruntime;
463 vruntime = cfs_rq->curr->vruntime;
465 if (cfs_rq->rb_leftmost) {
466 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
471 vruntime = se->vruntime;
473 vruntime = min_vruntime(vruntime, se->vruntime);
476 /* ensure we never gain time by being placed backwards. */
477 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
480 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
485 * Enqueue an entity into the rb-tree:
487 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
489 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
490 struct rb_node *parent = NULL;
491 struct sched_entity *entry;
495 * Find the right place in the rbtree:
499 entry = rb_entry(parent, struct sched_entity, run_node);
501 * We dont care about collisions. Nodes with
502 * the same key stay together.
504 if (entity_before(se, entry)) {
505 link = &parent->rb_left;
507 link = &parent->rb_right;
513 * Maintain a cache of leftmost tree entries (it is frequently
517 cfs_rq->rb_leftmost = &se->run_node;
519 rb_link_node(&se->run_node, parent, link);
520 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
523 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
525 if (cfs_rq->rb_leftmost == &se->run_node) {
526 struct rb_node *next_node;
528 next_node = rb_next(&se->run_node);
529 cfs_rq->rb_leftmost = next_node;
532 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
535 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
537 struct rb_node *left = cfs_rq->rb_leftmost;
542 return rb_entry(left, struct sched_entity, run_node);
545 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
547 struct rb_node *next = rb_next(&se->run_node);
552 return rb_entry(next, struct sched_entity, run_node);
555 #ifdef CONFIG_SCHED_DEBUG
556 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
558 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
563 return rb_entry(last, struct sched_entity, run_node);
566 /**************************************************************
567 * Scheduling class statistics methods:
570 int sched_proc_update_handler(struct ctl_table *table, int write,
571 void __user *buffer, size_t *lenp,
574 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
575 unsigned int factor = get_update_sysctl_factor();
580 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
581 sysctl_sched_min_granularity);
583 #define WRT_SYSCTL(name) \
584 (normalized_sysctl_##name = sysctl_##name / (factor))
585 WRT_SYSCTL(sched_min_granularity);
586 WRT_SYSCTL(sched_latency);
587 WRT_SYSCTL(sched_wakeup_granularity);
597 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
599 if (unlikely(se->load.weight != NICE_0_LOAD))
600 delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
606 * The idea is to set a period in which each task runs once.
608 * When there are too many tasks (sched_nr_latency) we have to stretch
609 * this period because otherwise the slices get too small.
611 * p = (nr <= nl) ? l : l*nr/nl
613 static u64 __sched_period(unsigned long nr_running)
615 if (unlikely(nr_running > sched_nr_latency))
616 return nr_running * sysctl_sched_min_granularity;
618 return sysctl_sched_latency;
622 * We calculate the wall-time slice from the period by taking a part
623 * proportional to the weight.
627 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
629 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
631 for_each_sched_entity(se) {
632 struct load_weight *load;
633 struct load_weight lw;
635 cfs_rq = cfs_rq_of(se);
636 load = &cfs_rq->load;
638 if (unlikely(!se->on_rq)) {
641 update_load_add(&lw, se->load.weight);
644 slice = __calc_delta(slice, se->load.weight, load);
650 * We calculate the vruntime slice of a to-be-inserted task.
654 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
656 return calc_delta_fair(sched_slice(cfs_rq, se), se);
660 static int select_idle_sibling(struct task_struct *p, int cpu);
661 static unsigned long task_h_load(struct task_struct *p);
664 * We choose a half-life close to 1 scheduling period.
665 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
666 * dependent on this value.
668 #define LOAD_AVG_PERIOD 32
669 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
670 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
672 /* Give new sched_entity start runnable values to heavy its load in infant time */
673 void init_entity_runnable_average(struct sched_entity *se)
675 struct sched_avg *sa = &se->avg;
677 sa->last_update_time = 0;
679 * sched_avg's period_contrib should be strictly less then 1024, so
680 * we give it 1023 to make sure it is almost a period (1024us), and
681 * will definitely be update (after enqueue).
683 sa->period_contrib = 1023;
684 sa->load_avg = scale_load_down(se->load.weight);
685 sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
686 sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
687 sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
688 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
691 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
692 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
694 void init_entity_runnable_average(struct sched_entity *se)
700 * Update the current task's runtime statistics.
702 static void update_curr(struct cfs_rq *cfs_rq)
704 struct sched_entity *curr = cfs_rq->curr;
705 u64 now = rq_clock_task(rq_of(cfs_rq));
711 delta_exec = now - curr->exec_start;
712 if (unlikely((s64)delta_exec <= 0))
715 curr->exec_start = now;
717 schedstat_set(curr->statistics.exec_max,
718 max(delta_exec, curr->statistics.exec_max));
720 curr->sum_exec_runtime += delta_exec;
721 schedstat_add(cfs_rq, exec_clock, delta_exec);
723 curr->vruntime += calc_delta_fair(delta_exec, curr);
724 update_min_vruntime(cfs_rq);
726 if (entity_is_task(curr)) {
727 struct task_struct *curtask = task_of(curr);
729 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
730 cpuacct_charge(curtask, delta_exec);
731 account_group_exec_runtime(curtask, delta_exec);
734 account_cfs_rq_runtime(cfs_rq, delta_exec);
737 static void update_curr_fair(struct rq *rq)
739 update_curr(cfs_rq_of(&rq->curr->se));
743 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
745 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
749 * Task is being enqueued - update stats:
751 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
754 * Are we enqueueing a waiting task? (for current tasks
755 * a dequeue/enqueue event is a NOP)
757 if (se != cfs_rq->curr)
758 update_stats_wait_start(cfs_rq, se);
762 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
764 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
765 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
766 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
767 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
768 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
769 #ifdef CONFIG_SCHEDSTATS
770 if (entity_is_task(se)) {
771 trace_sched_stat_wait(task_of(se),
772 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
775 schedstat_set(se->statistics.wait_start, 0);
779 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
782 * Mark the end of the wait period if dequeueing a
785 if (se != cfs_rq->curr)
786 update_stats_wait_end(cfs_rq, se);
790 * We are picking a new current task - update its stats:
793 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
796 * We are starting a new run period:
798 se->exec_start = rq_clock_task(rq_of(cfs_rq));
801 /**************************************************
802 * Scheduling class queueing methods:
805 #ifdef CONFIG_NUMA_BALANCING
807 * Approximate time to scan a full NUMA task in ms. The task scan period is
808 * calculated based on the tasks virtual memory size and
809 * numa_balancing_scan_size.
811 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
812 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
814 /* Portion of address space to scan in MB */
815 unsigned int sysctl_numa_balancing_scan_size = 256;
817 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
818 unsigned int sysctl_numa_balancing_scan_delay = 1000;
820 static unsigned int task_nr_scan_windows(struct task_struct *p)
822 unsigned long rss = 0;
823 unsigned long nr_scan_pages;
826 * Calculations based on RSS as non-present and empty pages are skipped
827 * by the PTE scanner and NUMA hinting faults should be trapped based
830 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
831 rss = get_mm_rss(p->mm);
835 rss = round_up(rss, nr_scan_pages);
836 return rss / nr_scan_pages;
839 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
840 #define MAX_SCAN_WINDOW 2560
842 static unsigned int task_scan_min(struct task_struct *p)
844 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
845 unsigned int scan, floor;
846 unsigned int windows = 1;
848 if (scan_size < MAX_SCAN_WINDOW)
849 windows = MAX_SCAN_WINDOW / scan_size;
850 floor = 1000 / windows;
852 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
853 return max_t(unsigned int, floor, scan);
856 static unsigned int task_scan_max(struct task_struct *p)
858 unsigned int smin = task_scan_min(p);
861 /* Watch for min being lower than max due to floor calculations */
862 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
863 return max(smin, smax);
866 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
868 rq->nr_numa_running += (p->numa_preferred_nid != -1);
869 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
872 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
874 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
875 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
881 spinlock_t lock; /* nr_tasks, tasks */
886 nodemask_t active_nodes;
887 unsigned long total_faults;
889 * Faults_cpu is used to decide whether memory should move
890 * towards the CPU. As a consequence, these stats are weighted
891 * more by CPU use than by memory faults.
893 unsigned long *faults_cpu;
894 unsigned long faults[0];
897 /* Shared or private faults. */
898 #define NR_NUMA_HINT_FAULT_TYPES 2
900 /* Memory and CPU locality */
901 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
903 /* Averaged statistics, and temporary buffers. */
904 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
906 pid_t task_numa_group_id(struct task_struct *p)
908 return p->numa_group ? p->numa_group->gid : 0;
912 * The averaged statistics, shared & private, memory & cpu,
913 * occupy the first half of the array. The second half of the
914 * array is for current counters, which are averaged into the
915 * first set by task_numa_placement.
917 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
919 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
922 static inline unsigned long task_faults(struct task_struct *p, int nid)
927 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
928 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
931 static inline unsigned long group_faults(struct task_struct *p, int nid)
936 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
937 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
940 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
942 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
943 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
946 /* Handle placement on systems where not all nodes are directly connected. */
947 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
948 int maxdist, bool task)
950 unsigned long score = 0;
954 * All nodes are directly connected, and the same distance
955 * from each other. No need for fancy placement algorithms.
957 if (sched_numa_topology_type == NUMA_DIRECT)
961 * This code is called for each node, introducing N^2 complexity,
962 * which should be ok given the number of nodes rarely exceeds 8.
964 for_each_online_node(node) {
965 unsigned long faults;
966 int dist = node_distance(nid, node);
969 * The furthest away nodes in the system are not interesting
970 * for placement; nid was already counted.
972 if (dist == sched_max_numa_distance || node == nid)
976 * On systems with a backplane NUMA topology, compare groups
977 * of nodes, and move tasks towards the group with the most
978 * memory accesses. When comparing two nodes at distance
979 * "hoplimit", only nodes closer by than "hoplimit" are part
980 * of each group. Skip other nodes.
982 if (sched_numa_topology_type == NUMA_BACKPLANE &&
986 /* Add up the faults from nearby nodes. */
988 faults = task_faults(p, node);
990 faults = group_faults(p, node);
993 * On systems with a glueless mesh NUMA topology, there are
994 * no fixed "groups of nodes". Instead, nodes that are not
995 * directly connected bounce traffic through intermediate
996 * nodes; a numa_group can occupy any set of nodes.
997 * The further away a node is, the less the faults count.
998 * This seems to result in good task placement.
1000 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1001 faults *= (sched_max_numa_distance - dist);
1002 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1012 * These return the fraction of accesses done by a particular task, or
1013 * task group, on a particular numa node. The group weight is given a
1014 * larger multiplier, in order to group tasks together that are almost
1015 * evenly spread out between numa nodes.
1017 static inline unsigned long task_weight(struct task_struct *p, int nid,
1020 unsigned long faults, total_faults;
1022 if (!p->numa_faults)
1025 total_faults = p->total_numa_faults;
1030 faults = task_faults(p, nid);
1031 faults += score_nearby_nodes(p, nid, dist, true);
1033 return 1000 * faults / total_faults;
1036 static inline unsigned long group_weight(struct task_struct *p, int nid,
1039 unsigned long faults, total_faults;
1044 total_faults = p->numa_group->total_faults;
1049 faults = group_faults(p, nid);
1050 faults += score_nearby_nodes(p, nid, dist, false);
1052 return 1000 * faults / total_faults;
1055 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1056 int src_nid, int dst_cpu)
1058 struct numa_group *ng = p->numa_group;
1059 int dst_nid = cpu_to_node(dst_cpu);
1060 int last_cpupid, this_cpupid;
1062 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1065 * Multi-stage node selection is used in conjunction with a periodic
1066 * migration fault to build a temporal task<->page relation. By using
1067 * a two-stage filter we remove short/unlikely relations.
1069 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1070 * a task's usage of a particular page (n_p) per total usage of this
1071 * page (n_t) (in a given time-span) to a probability.
1073 * Our periodic faults will sample this probability and getting the
1074 * same result twice in a row, given these samples are fully
1075 * independent, is then given by P(n)^2, provided our sample period
1076 * is sufficiently short compared to the usage pattern.
1078 * This quadric squishes small probabilities, making it less likely we
1079 * act on an unlikely task<->page relation.
1081 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1082 if (!cpupid_pid_unset(last_cpupid) &&
1083 cpupid_to_nid(last_cpupid) != dst_nid)
1086 /* Always allow migrate on private faults */
1087 if (cpupid_match_pid(p, last_cpupid))
1090 /* A shared fault, but p->numa_group has not been set up yet. */
1095 * Do not migrate if the destination is not a node that
1096 * is actively used by this numa group.
1098 if (!node_isset(dst_nid, ng->active_nodes))
1102 * Source is a node that is not actively used by this
1103 * numa group, while the destination is. Migrate.
1105 if (!node_isset(src_nid, ng->active_nodes))
1109 * Both source and destination are nodes in active
1110 * use by this numa group. Maximize memory bandwidth
1111 * by migrating from more heavily used groups, to less
1112 * heavily used ones, spreading the load around.
1113 * Use a 1/4 hysteresis to avoid spurious page movement.
1115 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1118 static unsigned long weighted_cpuload(const int cpu);
1119 static unsigned long source_load(int cpu, int type);
1120 static unsigned long target_load(int cpu, int type);
1121 static unsigned long capacity_of(int cpu);
1122 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1124 /* Cached statistics for all CPUs within a node */
1126 unsigned long nr_running;
1129 /* Total compute capacity of CPUs on a node */
1130 unsigned long compute_capacity;
1132 /* Approximate capacity in terms of runnable tasks on a node */
1133 unsigned long task_capacity;
1134 int has_free_capacity;
1138 * XXX borrowed from update_sg_lb_stats
1140 static void update_numa_stats(struct numa_stats *ns, int nid)
1142 int smt, cpu, cpus = 0;
1143 unsigned long capacity;
1145 memset(ns, 0, sizeof(*ns));
1146 for_each_cpu(cpu, cpumask_of_node(nid)) {
1147 struct rq *rq = cpu_rq(cpu);
1149 ns->nr_running += rq->nr_running;
1150 ns->load += weighted_cpuload(cpu);
1151 ns->compute_capacity += capacity_of(cpu);
1157 * If we raced with hotplug and there are no CPUs left in our mask
1158 * the @ns structure is NULL'ed and task_numa_compare() will
1159 * not find this node attractive.
1161 * We'll either bail at !has_free_capacity, or we'll detect a huge
1162 * imbalance and bail there.
1167 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1168 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1169 capacity = cpus / smt; /* cores */
1171 ns->task_capacity = min_t(unsigned, capacity,
1172 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1173 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1176 struct task_numa_env {
1177 struct task_struct *p;
1179 int src_cpu, src_nid;
1180 int dst_cpu, dst_nid;
1182 struct numa_stats src_stats, dst_stats;
1187 struct task_struct *best_task;
1192 static void task_numa_assign(struct task_numa_env *env,
1193 struct task_struct *p, long imp)
1196 put_task_struct(env->best_task);
1201 env->best_imp = imp;
1202 env->best_cpu = env->dst_cpu;
1205 static bool load_too_imbalanced(long src_load, long dst_load,
1206 struct task_numa_env *env)
1209 long orig_src_load, orig_dst_load;
1210 long src_capacity, dst_capacity;
1213 * The load is corrected for the CPU capacity available on each node.
1216 * ------------ vs ---------
1217 * src_capacity dst_capacity
1219 src_capacity = env->src_stats.compute_capacity;
1220 dst_capacity = env->dst_stats.compute_capacity;
1222 /* We care about the slope of the imbalance, not the direction. */
1223 if (dst_load < src_load)
1224 swap(dst_load, src_load);
1226 /* Is the difference below the threshold? */
1227 imb = dst_load * src_capacity * 100 -
1228 src_load * dst_capacity * env->imbalance_pct;
1233 * The imbalance is above the allowed threshold.
1234 * Compare it with the old imbalance.
1236 orig_src_load = env->src_stats.load;
1237 orig_dst_load = env->dst_stats.load;
1239 if (orig_dst_load < orig_src_load)
1240 swap(orig_dst_load, orig_src_load);
1242 old_imb = orig_dst_load * src_capacity * 100 -
1243 orig_src_load * dst_capacity * env->imbalance_pct;
1245 /* Would this change make things worse? */
1246 return (imb > old_imb);
1250 * This checks if the overall compute and NUMA accesses of the system would
1251 * be improved if the source tasks was migrated to the target dst_cpu taking
1252 * into account that it might be best if task running on the dst_cpu should
1253 * be exchanged with the source task
1255 static void task_numa_compare(struct task_numa_env *env,
1256 long taskimp, long groupimp)
1258 struct rq *src_rq = cpu_rq(env->src_cpu);
1259 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1260 struct task_struct *cur;
1261 long src_load, dst_load;
1263 long imp = env->p->numa_group ? groupimp : taskimp;
1265 int dist = env->dist;
1269 raw_spin_lock_irq(&dst_rq->lock);
1272 * No need to move the exiting task, and this ensures that ->curr
1273 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1274 * is safe under RCU read lock.
1275 * Note that rcu_read_lock() itself can't protect from the final
1276 * put_task_struct() after the last schedule().
1278 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1280 raw_spin_unlock_irq(&dst_rq->lock);
1283 * Because we have preemption enabled we can get migrated around and
1284 * end try selecting ourselves (current == env->p) as a swap candidate.
1290 * "imp" is the fault differential for the source task between the
1291 * source and destination node. Calculate the total differential for
1292 * the source task and potential destination task. The more negative
1293 * the value is, the more rmeote accesses that would be expected to
1294 * be incurred if the tasks were swapped.
1297 /* Skip this swap candidate if cannot move to the source cpu */
1298 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1302 * If dst and source tasks are in the same NUMA group, or not
1303 * in any group then look only at task weights.
1305 if (cur->numa_group == env->p->numa_group) {
1306 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1307 task_weight(cur, env->dst_nid, dist);
1309 * Add some hysteresis to prevent swapping the
1310 * tasks within a group over tiny differences.
1312 if (cur->numa_group)
1316 * Compare the group weights. If a task is all by
1317 * itself (not part of a group), use the task weight
1320 if (cur->numa_group)
1321 imp += group_weight(cur, env->src_nid, dist) -
1322 group_weight(cur, env->dst_nid, dist);
1324 imp += task_weight(cur, env->src_nid, dist) -
1325 task_weight(cur, env->dst_nid, dist);
1329 if (imp <= env->best_imp && moveimp <= env->best_imp)
1333 /* Is there capacity at our destination? */
1334 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1335 !env->dst_stats.has_free_capacity)
1341 /* Balance doesn't matter much if we're running a task per cpu */
1342 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1343 dst_rq->nr_running == 1)
1347 * In the overloaded case, try and keep the load balanced.
1350 load = task_h_load(env->p);
1351 dst_load = env->dst_stats.load + load;
1352 src_load = env->src_stats.load - load;
1354 if (moveimp > imp && moveimp > env->best_imp) {
1356 * If the improvement from just moving env->p direction is
1357 * better than swapping tasks around, check if a move is
1358 * possible. Store a slightly smaller score than moveimp,
1359 * so an actually idle CPU will win.
1361 if (!load_too_imbalanced(src_load, dst_load, env)) {
1368 if (imp <= env->best_imp)
1372 load = task_h_load(cur);
1377 if (load_too_imbalanced(src_load, dst_load, env))
1381 * One idle CPU per node is evaluated for a task numa move.
1382 * Call select_idle_sibling to maybe find a better one.
1385 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1388 task_numa_assign(env, cur, imp);
1393 static void task_numa_find_cpu(struct task_numa_env *env,
1394 long taskimp, long groupimp)
1398 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1399 /* Skip this CPU if the source task cannot migrate */
1400 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1404 task_numa_compare(env, taskimp, groupimp);
1408 /* Only move tasks to a NUMA node less busy than the current node. */
1409 static bool numa_has_capacity(struct task_numa_env *env)
1411 struct numa_stats *src = &env->src_stats;
1412 struct numa_stats *dst = &env->dst_stats;
1414 if (src->has_free_capacity && !dst->has_free_capacity)
1418 * Only consider a task move if the source has a higher load
1419 * than the destination, corrected for CPU capacity on each node.
1421 * src->load dst->load
1422 * --------------------- vs ---------------------
1423 * src->compute_capacity dst->compute_capacity
1425 if (src->load * dst->compute_capacity * env->imbalance_pct >
1427 dst->load * src->compute_capacity * 100)
1433 static int task_numa_migrate(struct task_struct *p)
1435 struct task_numa_env env = {
1438 .src_cpu = task_cpu(p),
1439 .src_nid = task_node(p),
1441 .imbalance_pct = 112,
1447 struct sched_domain *sd;
1448 unsigned long taskweight, groupweight;
1450 long taskimp, groupimp;
1453 * Pick the lowest SD_NUMA domain, as that would have the smallest
1454 * imbalance and would be the first to start moving tasks about.
1456 * And we want to avoid any moving of tasks about, as that would create
1457 * random movement of tasks -- counter the numa conditions we're trying
1461 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1463 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1467 * Cpusets can break the scheduler domain tree into smaller
1468 * balance domains, some of which do not cross NUMA boundaries.
1469 * Tasks that are "trapped" in such domains cannot be migrated
1470 * elsewhere, so there is no point in (re)trying.
1472 if (unlikely(!sd)) {
1473 p->numa_preferred_nid = task_node(p);
1477 env.dst_nid = p->numa_preferred_nid;
1478 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1479 taskweight = task_weight(p, env.src_nid, dist);
1480 groupweight = group_weight(p, env.src_nid, dist);
1481 update_numa_stats(&env.src_stats, env.src_nid);
1482 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1483 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1484 update_numa_stats(&env.dst_stats, env.dst_nid);
1486 /* Try to find a spot on the preferred nid. */
1487 if (numa_has_capacity(&env))
1488 task_numa_find_cpu(&env, taskimp, groupimp);
1491 * Look at other nodes in these cases:
1492 * - there is no space available on the preferred_nid
1493 * - the task is part of a numa_group that is interleaved across
1494 * multiple NUMA nodes; in order to better consolidate the group,
1495 * we need to check other locations.
1497 if (env.best_cpu == -1 || (p->numa_group &&
1498 nodes_weight(p->numa_group->active_nodes) > 1)) {
1499 for_each_online_node(nid) {
1500 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1503 dist = node_distance(env.src_nid, env.dst_nid);
1504 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1506 taskweight = task_weight(p, env.src_nid, dist);
1507 groupweight = group_weight(p, env.src_nid, dist);
1510 /* Only consider nodes where both task and groups benefit */
1511 taskimp = task_weight(p, nid, dist) - taskweight;
1512 groupimp = group_weight(p, nid, dist) - groupweight;
1513 if (taskimp < 0 && groupimp < 0)
1518 update_numa_stats(&env.dst_stats, env.dst_nid);
1519 if (numa_has_capacity(&env))
1520 task_numa_find_cpu(&env, taskimp, groupimp);
1525 * If the task is part of a workload that spans multiple NUMA nodes,
1526 * and is migrating into one of the workload's active nodes, remember
1527 * this node as the task's preferred numa node, so the workload can
1529 * A task that migrated to a second choice node will be better off
1530 * trying for a better one later. Do not set the preferred node here.
1532 if (p->numa_group) {
1533 if (env.best_cpu == -1)
1538 if (node_isset(nid, p->numa_group->active_nodes))
1539 sched_setnuma(p, env.dst_nid);
1542 /* No better CPU than the current one was found. */
1543 if (env.best_cpu == -1)
1547 * Reset the scan period if the task is being rescheduled on an
1548 * alternative node to recheck if the tasks is now properly placed.
1550 p->numa_scan_period = task_scan_min(p);
1552 if (env.best_task == NULL) {
1553 ret = migrate_task_to(p, env.best_cpu);
1555 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1559 ret = migrate_swap(p, env.best_task);
1561 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1562 put_task_struct(env.best_task);
1566 /* Attempt to migrate a task to a CPU on the preferred node. */
1567 static void numa_migrate_preferred(struct task_struct *p)
1569 unsigned long interval = HZ;
1571 /* This task has no NUMA fault statistics yet */
1572 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1575 /* Periodically retry migrating the task to the preferred node */
1576 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1577 p->numa_migrate_retry = jiffies + interval;
1579 /* Success if task is already running on preferred CPU */
1580 if (task_node(p) == p->numa_preferred_nid)
1583 /* Otherwise, try migrate to a CPU on the preferred node */
1584 task_numa_migrate(p);
1588 * Find the nodes on which the workload is actively running. We do this by
1589 * tracking the nodes from which NUMA hinting faults are triggered. This can
1590 * be different from the set of nodes where the workload's memory is currently
1593 * The bitmask is used to make smarter decisions on when to do NUMA page
1594 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1595 * are added when they cause over 6/16 of the maximum number of faults, but
1596 * only removed when they drop below 3/16.
1598 static void update_numa_active_node_mask(struct numa_group *numa_group)
1600 unsigned long faults, max_faults = 0;
1603 for_each_online_node(nid) {
1604 faults = group_faults_cpu(numa_group, nid);
1605 if (faults > max_faults)
1606 max_faults = faults;
1609 for_each_online_node(nid) {
1610 faults = group_faults_cpu(numa_group, nid);
1611 if (!node_isset(nid, numa_group->active_nodes)) {
1612 if (faults > max_faults * 6 / 16)
1613 node_set(nid, numa_group->active_nodes);
1614 } else if (faults < max_faults * 3 / 16)
1615 node_clear(nid, numa_group->active_nodes);
1620 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1621 * increments. The more local the fault statistics are, the higher the scan
1622 * period will be for the next scan window. If local/(local+remote) ratio is
1623 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1624 * the scan period will decrease. Aim for 70% local accesses.
1626 #define NUMA_PERIOD_SLOTS 10
1627 #define NUMA_PERIOD_THRESHOLD 7
1630 * Increase the scan period (slow down scanning) if the majority of
1631 * our memory is already on our local node, or if the majority of
1632 * the page accesses are shared with other processes.
1633 * Otherwise, decrease the scan period.
1635 static void update_task_scan_period(struct task_struct *p,
1636 unsigned long shared, unsigned long private)
1638 unsigned int period_slot;
1642 unsigned long remote = p->numa_faults_locality[0];
1643 unsigned long local = p->numa_faults_locality[1];
1646 * If there were no record hinting faults then either the task is
1647 * completely idle or all activity is areas that are not of interest
1648 * to automatic numa balancing. Related to that, if there were failed
1649 * migration then it implies we are migrating too quickly or the local
1650 * node is overloaded. In either case, scan slower
1652 if (local + shared == 0 || p->numa_faults_locality[2]) {
1653 p->numa_scan_period = min(p->numa_scan_period_max,
1654 p->numa_scan_period << 1);
1656 p->mm->numa_next_scan = jiffies +
1657 msecs_to_jiffies(p->numa_scan_period);
1663 * Prepare to scale scan period relative to the current period.
1664 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1665 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1666 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1668 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1669 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1670 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1671 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1674 diff = slot * period_slot;
1676 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1679 * Scale scan rate increases based on sharing. There is an
1680 * inverse relationship between the degree of sharing and
1681 * the adjustment made to the scanning period. Broadly
1682 * speaking the intent is that there is little point
1683 * scanning faster if shared accesses dominate as it may
1684 * simply bounce migrations uselessly
1686 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1687 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1690 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1691 task_scan_min(p), task_scan_max(p));
1692 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1696 * Get the fraction of time the task has been running since the last
1697 * NUMA placement cycle. The scheduler keeps similar statistics, but
1698 * decays those on a 32ms period, which is orders of magnitude off
1699 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1700 * stats only if the task is so new there are no NUMA statistics yet.
1702 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1704 u64 runtime, delta, now;
1705 /* Use the start of this time slice to avoid calculations. */
1706 now = p->se.exec_start;
1707 runtime = p->se.sum_exec_runtime;
1709 if (p->last_task_numa_placement) {
1710 delta = runtime - p->last_sum_exec_runtime;
1711 *period = now - p->last_task_numa_placement;
1713 delta = p->se.avg.load_sum / p->se.load.weight;
1714 *period = LOAD_AVG_MAX;
1717 p->last_sum_exec_runtime = runtime;
1718 p->last_task_numa_placement = now;
1724 * Determine the preferred nid for a task in a numa_group. This needs to
1725 * be done in a way that produces consistent results with group_weight,
1726 * otherwise workloads might not converge.
1728 static int preferred_group_nid(struct task_struct *p, int nid)
1733 /* Direct connections between all NUMA nodes. */
1734 if (sched_numa_topology_type == NUMA_DIRECT)
1738 * On a system with glueless mesh NUMA topology, group_weight
1739 * scores nodes according to the number of NUMA hinting faults on
1740 * both the node itself, and on nearby nodes.
1742 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1743 unsigned long score, max_score = 0;
1744 int node, max_node = nid;
1746 dist = sched_max_numa_distance;
1748 for_each_online_node(node) {
1749 score = group_weight(p, node, dist);
1750 if (score > max_score) {
1759 * Finding the preferred nid in a system with NUMA backplane
1760 * interconnect topology is more involved. The goal is to locate
1761 * tasks from numa_groups near each other in the system, and
1762 * untangle workloads from different sides of the system. This requires
1763 * searching down the hierarchy of node groups, recursively searching
1764 * inside the highest scoring group of nodes. The nodemask tricks
1765 * keep the complexity of the search down.
1767 nodes = node_online_map;
1768 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1769 unsigned long max_faults = 0;
1770 nodemask_t max_group = NODE_MASK_NONE;
1773 /* Are there nodes at this distance from each other? */
1774 if (!find_numa_distance(dist))
1777 for_each_node_mask(a, nodes) {
1778 unsigned long faults = 0;
1779 nodemask_t this_group;
1780 nodes_clear(this_group);
1782 /* Sum group's NUMA faults; includes a==b case. */
1783 for_each_node_mask(b, nodes) {
1784 if (node_distance(a, b) < dist) {
1785 faults += group_faults(p, b);
1786 node_set(b, this_group);
1787 node_clear(b, nodes);
1791 /* Remember the top group. */
1792 if (faults > max_faults) {
1793 max_faults = faults;
1794 max_group = this_group;
1796 * subtle: at the smallest distance there is
1797 * just one node left in each "group", the
1798 * winner is the preferred nid.
1803 /* Next round, evaluate the nodes within max_group. */
1811 static void task_numa_placement(struct task_struct *p)
1813 int seq, nid, max_nid = -1, max_group_nid = -1;
1814 unsigned long max_faults = 0, max_group_faults = 0;
1815 unsigned long fault_types[2] = { 0, 0 };
1816 unsigned long total_faults;
1817 u64 runtime, period;
1818 spinlock_t *group_lock = NULL;
1821 * The p->mm->numa_scan_seq field gets updated without
1822 * exclusive access. Use READ_ONCE() here to ensure
1823 * that the field is read in a single access:
1825 seq = READ_ONCE(p->mm->numa_scan_seq);
1826 if (p->numa_scan_seq == seq)
1828 p->numa_scan_seq = seq;
1829 p->numa_scan_period_max = task_scan_max(p);
1831 total_faults = p->numa_faults_locality[0] +
1832 p->numa_faults_locality[1];
1833 runtime = numa_get_avg_runtime(p, &period);
1835 /* If the task is part of a group prevent parallel updates to group stats */
1836 if (p->numa_group) {
1837 group_lock = &p->numa_group->lock;
1838 spin_lock_irq(group_lock);
1841 /* Find the node with the highest number of faults */
1842 for_each_online_node(nid) {
1843 /* Keep track of the offsets in numa_faults array */
1844 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1845 unsigned long faults = 0, group_faults = 0;
1848 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1849 long diff, f_diff, f_weight;
1851 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1852 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1853 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1854 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1856 /* Decay existing window, copy faults since last scan */
1857 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1858 fault_types[priv] += p->numa_faults[membuf_idx];
1859 p->numa_faults[membuf_idx] = 0;
1862 * Normalize the faults_from, so all tasks in a group
1863 * count according to CPU use, instead of by the raw
1864 * number of faults. Tasks with little runtime have
1865 * little over-all impact on throughput, and thus their
1866 * faults are less important.
1868 f_weight = div64_u64(runtime << 16, period + 1);
1869 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1871 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1872 p->numa_faults[cpubuf_idx] = 0;
1874 p->numa_faults[mem_idx] += diff;
1875 p->numa_faults[cpu_idx] += f_diff;
1876 faults += p->numa_faults[mem_idx];
1877 p->total_numa_faults += diff;
1878 if (p->numa_group) {
1880 * safe because we can only change our own group
1882 * mem_idx represents the offset for a given
1883 * nid and priv in a specific region because it
1884 * is at the beginning of the numa_faults array.
1886 p->numa_group->faults[mem_idx] += diff;
1887 p->numa_group->faults_cpu[mem_idx] += f_diff;
1888 p->numa_group->total_faults += diff;
1889 group_faults += p->numa_group->faults[mem_idx];
1893 if (faults > max_faults) {
1894 max_faults = faults;
1898 if (group_faults > max_group_faults) {
1899 max_group_faults = group_faults;
1900 max_group_nid = nid;
1904 update_task_scan_period(p, fault_types[0], fault_types[1]);
1906 if (p->numa_group) {
1907 update_numa_active_node_mask(p->numa_group);
1908 spin_unlock_irq(group_lock);
1909 max_nid = preferred_group_nid(p, max_group_nid);
1913 /* Set the new preferred node */
1914 if (max_nid != p->numa_preferred_nid)
1915 sched_setnuma(p, max_nid);
1917 if (task_node(p) != p->numa_preferred_nid)
1918 numa_migrate_preferred(p);
1922 static inline int get_numa_group(struct numa_group *grp)
1924 return atomic_inc_not_zero(&grp->refcount);
1927 static inline void put_numa_group(struct numa_group *grp)
1929 if (atomic_dec_and_test(&grp->refcount))
1930 kfree_rcu(grp, rcu);
1933 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1936 struct numa_group *grp, *my_grp;
1937 struct task_struct *tsk;
1939 int cpu = cpupid_to_cpu(cpupid);
1942 if (unlikely(!p->numa_group)) {
1943 unsigned int size = sizeof(struct numa_group) +
1944 4*nr_node_ids*sizeof(unsigned long);
1946 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1950 atomic_set(&grp->refcount, 1);
1951 spin_lock_init(&grp->lock);
1953 /* Second half of the array tracks nids where faults happen */
1954 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1957 node_set(task_node(current), grp->active_nodes);
1959 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1960 grp->faults[i] = p->numa_faults[i];
1962 grp->total_faults = p->total_numa_faults;
1965 rcu_assign_pointer(p->numa_group, grp);
1969 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1971 if (!cpupid_match_pid(tsk, cpupid))
1974 grp = rcu_dereference(tsk->numa_group);
1978 my_grp = p->numa_group;
1983 * Only join the other group if its bigger; if we're the bigger group,
1984 * the other task will join us.
1986 if (my_grp->nr_tasks > grp->nr_tasks)
1990 * Tie-break on the grp address.
1992 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1995 /* Always join threads in the same process. */
1996 if (tsk->mm == current->mm)
1999 /* Simple filter to avoid false positives due to PID collisions */
2000 if (flags & TNF_SHARED)
2003 /* Update priv based on whether false sharing was detected */
2006 if (join && !get_numa_group(grp))
2014 BUG_ON(irqs_disabled());
2015 double_lock_irq(&my_grp->lock, &grp->lock);
2017 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2018 my_grp->faults[i] -= p->numa_faults[i];
2019 grp->faults[i] += p->numa_faults[i];
2021 my_grp->total_faults -= p->total_numa_faults;
2022 grp->total_faults += p->total_numa_faults;
2027 spin_unlock(&my_grp->lock);
2028 spin_unlock_irq(&grp->lock);
2030 rcu_assign_pointer(p->numa_group, grp);
2032 put_numa_group(my_grp);
2040 void task_numa_free(struct task_struct *p)
2042 struct numa_group *grp = p->numa_group;
2043 void *numa_faults = p->numa_faults;
2044 unsigned long flags;
2048 spin_lock_irqsave(&grp->lock, flags);
2049 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2050 grp->faults[i] -= p->numa_faults[i];
2051 grp->total_faults -= p->total_numa_faults;
2054 spin_unlock_irqrestore(&grp->lock, flags);
2055 RCU_INIT_POINTER(p->numa_group, NULL);
2056 put_numa_group(grp);
2059 p->numa_faults = NULL;
2064 * Got a PROT_NONE fault for a page on @node.
2066 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2068 struct task_struct *p = current;
2069 bool migrated = flags & TNF_MIGRATED;
2070 int cpu_node = task_node(current);
2071 int local = !!(flags & TNF_FAULT_LOCAL);
2074 if (!static_branch_likely(&sched_numa_balancing))
2077 /* for example, ksmd faulting in a user's mm */
2081 /* Allocate buffer to track faults on a per-node basis */
2082 if (unlikely(!p->numa_faults)) {
2083 int size = sizeof(*p->numa_faults) *
2084 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2086 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2087 if (!p->numa_faults)
2090 p->total_numa_faults = 0;
2091 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2095 * First accesses are treated as private, otherwise consider accesses
2096 * to be private if the accessing pid has not changed
2098 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2101 priv = cpupid_match_pid(p, last_cpupid);
2102 if (!priv && !(flags & TNF_NO_GROUP))
2103 task_numa_group(p, last_cpupid, flags, &priv);
2107 * If a workload spans multiple NUMA nodes, a shared fault that
2108 * occurs wholly within the set of nodes that the workload is
2109 * actively using should be counted as local. This allows the
2110 * scan rate to slow down when a workload has settled down.
2112 if (!priv && !local && p->numa_group &&
2113 node_isset(cpu_node, p->numa_group->active_nodes) &&
2114 node_isset(mem_node, p->numa_group->active_nodes))
2117 task_numa_placement(p);
2120 * Retry task to preferred node migration periodically, in case it
2121 * case it previously failed, or the scheduler moved us.
2123 if (time_after(jiffies, p->numa_migrate_retry))
2124 numa_migrate_preferred(p);
2127 p->numa_pages_migrated += pages;
2128 if (flags & TNF_MIGRATE_FAIL)
2129 p->numa_faults_locality[2] += pages;
2131 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2132 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2133 p->numa_faults_locality[local] += pages;
2136 static void reset_ptenuma_scan(struct task_struct *p)
2139 * We only did a read acquisition of the mmap sem, so
2140 * p->mm->numa_scan_seq is written to without exclusive access
2141 * and the update is not guaranteed to be atomic. That's not
2142 * much of an issue though, since this is just used for
2143 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2144 * expensive, to avoid any form of compiler optimizations:
2146 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2147 p->mm->numa_scan_offset = 0;
2151 * The expensive part of numa migration is done from task_work context.
2152 * Triggered from task_tick_numa().
2154 void task_numa_work(struct callback_head *work)
2156 unsigned long migrate, next_scan, now = jiffies;
2157 struct task_struct *p = current;
2158 struct mm_struct *mm = p->mm;
2159 struct vm_area_struct *vma;
2160 unsigned long start, end;
2161 unsigned long nr_pte_updates = 0;
2162 long pages, virtpages;
2164 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2166 work->next = work; /* protect against double add */
2168 * Who cares about NUMA placement when they're dying.
2170 * NOTE: make sure not to dereference p->mm before this check,
2171 * exit_task_work() happens _after_ exit_mm() so we could be called
2172 * without p->mm even though we still had it when we enqueued this
2175 if (p->flags & PF_EXITING)
2178 if (!mm->numa_next_scan) {
2179 mm->numa_next_scan = now +
2180 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2184 * Enforce maximal scan/migration frequency..
2186 migrate = mm->numa_next_scan;
2187 if (time_before(now, migrate))
2190 if (p->numa_scan_period == 0) {
2191 p->numa_scan_period_max = task_scan_max(p);
2192 p->numa_scan_period = task_scan_min(p);
2195 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2196 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2200 * Delay this task enough that another task of this mm will likely win
2201 * the next time around.
2203 p->node_stamp += 2 * TICK_NSEC;
2205 start = mm->numa_scan_offset;
2206 pages = sysctl_numa_balancing_scan_size;
2207 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2208 virtpages = pages * 8; /* Scan up to this much virtual space */
2213 down_read(&mm->mmap_sem);
2214 vma = find_vma(mm, start);
2216 reset_ptenuma_scan(p);
2220 for (; vma; vma = vma->vm_next) {
2221 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2222 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2227 * Shared library pages mapped by multiple processes are not
2228 * migrated as it is expected they are cache replicated. Avoid
2229 * hinting faults in read-only file-backed mappings or the vdso
2230 * as migrating the pages will be of marginal benefit.
2233 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2237 * Skip inaccessible VMAs to avoid any confusion between
2238 * PROT_NONE and NUMA hinting ptes
2240 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2244 start = max(start, vma->vm_start);
2245 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2246 end = min(end, vma->vm_end);
2247 nr_pte_updates = change_prot_numa(vma, start, end);
2250 * Try to scan sysctl_numa_balancing_size worth of
2251 * hpages that have at least one present PTE that
2252 * is not already pte-numa. If the VMA contains
2253 * areas that are unused or already full of prot_numa
2254 * PTEs, scan up to virtpages, to skip through those
2258 pages -= (end - start) >> PAGE_SHIFT;
2259 virtpages -= (end - start) >> PAGE_SHIFT;
2262 if (pages <= 0 || virtpages <= 0)
2266 } while (end != vma->vm_end);
2271 * It is possible to reach the end of the VMA list but the last few
2272 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2273 * would find the !migratable VMA on the next scan but not reset the
2274 * scanner to the start so check it now.
2277 mm->numa_scan_offset = start;
2279 reset_ptenuma_scan(p);
2280 up_read(&mm->mmap_sem);
2284 * Drive the periodic memory faults..
2286 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2288 struct callback_head *work = &curr->numa_work;
2292 * We don't care about NUMA placement if we don't have memory.
2294 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2298 * Using runtime rather than walltime has the dual advantage that
2299 * we (mostly) drive the selection from busy threads and that the
2300 * task needs to have done some actual work before we bother with
2303 now = curr->se.sum_exec_runtime;
2304 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2306 if (now > curr->node_stamp + period) {
2307 if (!curr->node_stamp)
2308 curr->numa_scan_period = task_scan_min(curr);
2309 curr->node_stamp += period;
2311 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2312 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2313 task_work_add(curr, work, true);
2318 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2322 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2326 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2329 #endif /* CONFIG_NUMA_BALANCING */
2332 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2334 update_load_add(&cfs_rq->load, se->load.weight);
2335 if (!parent_entity(se))
2336 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2338 if (entity_is_task(se)) {
2339 struct rq *rq = rq_of(cfs_rq);
2341 account_numa_enqueue(rq, task_of(se));
2342 list_add(&se->group_node, &rq->cfs_tasks);
2345 cfs_rq->nr_running++;
2349 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2351 update_load_sub(&cfs_rq->load, se->load.weight);
2352 if (!parent_entity(se))
2353 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2354 if (entity_is_task(se)) {
2355 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2356 list_del_init(&se->group_node);
2358 cfs_rq->nr_running--;
2361 #ifdef CONFIG_FAIR_GROUP_SCHED
2363 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2368 * Use this CPU's real-time load instead of the last load contribution
2369 * as the updating of the contribution is delayed, and we will use the
2370 * the real-time load to calc the share. See update_tg_load_avg().
2372 tg_weight = atomic_long_read(&tg->load_avg);
2373 tg_weight -= cfs_rq->tg_load_avg_contrib;
2374 tg_weight += cfs_rq->load.weight;
2379 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2381 long tg_weight, load, shares;
2383 tg_weight = calc_tg_weight(tg, cfs_rq);
2384 load = cfs_rq->load.weight;
2386 shares = (tg->shares * load);
2388 shares /= tg_weight;
2390 if (shares < MIN_SHARES)
2391 shares = MIN_SHARES;
2392 if (shares > tg->shares)
2393 shares = tg->shares;
2397 # else /* CONFIG_SMP */
2398 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2402 # endif /* CONFIG_SMP */
2403 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2404 unsigned long weight)
2407 /* commit outstanding execution time */
2408 if (cfs_rq->curr == se)
2409 update_curr(cfs_rq);
2410 account_entity_dequeue(cfs_rq, se);
2413 update_load_set(&se->load, weight);
2416 account_entity_enqueue(cfs_rq, se);
2419 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2421 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2423 struct task_group *tg;
2424 struct sched_entity *se;
2428 se = tg->se[cpu_of(rq_of(cfs_rq))];
2429 if (!se || throttled_hierarchy(cfs_rq))
2432 if (likely(se->load.weight == tg->shares))
2435 shares = calc_cfs_shares(cfs_rq, tg);
2437 reweight_entity(cfs_rq_of(se), se, shares);
2439 #else /* CONFIG_FAIR_GROUP_SCHED */
2440 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2443 #endif /* CONFIG_FAIR_GROUP_SCHED */
2446 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2447 static const u32 runnable_avg_yN_inv[] = {
2448 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2449 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2450 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2451 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2452 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2453 0x85aac367, 0x82cd8698,
2457 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2458 * over-estimates when re-combining.
2460 static const u32 runnable_avg_yN_sum[] = {
2461 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2462 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2463 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2468 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2470 static __always_inline u64 decay_load(u64 val, u64 n)
2472 unsigned int local_n;
2476 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2479 /* after bounds checking we can collapse to 32-bit */
2483 * As y^PERIOD = 1/2, we can combine
2484 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2485 * With a look-up table which covers y^n (n<PERIOD)
2487 * To achieve constant time decay_load.
2489 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2490 val >>= local_n / LOAD_AVG_PERIOD;
2491 local_n %= LOAD_AVG_PERIOD;
2494 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2499 * For updates fully spanning n periods, the contribution to runnable
2500 * average will be: \Sum 1024*y^n
2502 * We can compute this reasonably efficiently by combining:
2503 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2505 static u32 __compute_runnable_contrib(u64 n)
2509 if (likely(n <= LOAD_AVG_PERIOD))
2510 return runnable_avg_yN_sum[n];
2511 else if (unlikely(n >= LOAD_AVG_MAX_N))
2512 return LOAD_AVG_MAX;
2514 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2516 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2517 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2519 n -= LOAD_AVG_PERIOD;
2520 } while (n > LOAD_AVG_PERIOD);
2522 contrib = decay_load(contrib, n);
2523 return contrib + runnable_avg_yN_sum[n];
2526 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2527 #error "load tracking assumes 2^10 as unit"
2530 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2533 * We can represent the historical contribution to runnable average as the
2534 * coefficients of a geometric series. To do this we sub-divide our runnable
2535 * history into segments of approximately 1ms (1024us); label the segment that
2536 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2538 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2540 * (now) (~1ms ago) (~2ms ago)
2542 * Let u_i denote the fraction of p_i that the entity was runnable.
2544 * We then designate the fractions u_i as our co-efficients, yielding the
2545 * following representation of historical load:
2546 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2548 * We choose y based on the with of a reasonably scheduling period, fixing:
2551 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2552 * approximately half as much as the contribution to load within the last ms
2555 * When a period "rolls over" and we have new u_0`, multiplying the previous
2556 * sum again by y is sufficient to update:
2557 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2558 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2560 static __always_inline int
2561 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2562 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2564 u64 delta, scaled_delta, periods;
2566 unsigned int delta_w, scaled_delta_w, decayed = 0;
2567 unsigned long scale_freq, scale_cpu;
2569 delta = now - sa->last_update_time;
2571 * This should only happen when time goes backwards, which it
2572 * unfortunately does during sched clock init when we swap over to TSC.
2574 if ((s64)delta < 0) {
2575 sa->last_update_time = now;
2580 * Use 1024ns as the unit of measurement since it's a reasonable
2581 * approximation of 1us and fast to compute.
2586 sa->last_update_time = now;
2588 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2589 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2590 trace_sched_contrib_scale_f(cpu, scale_freq, scale_cpu);
2592 /* delta_w is the amount already accumulated against our next period */
2593 delta_w = sa->period_contrib;
2594 if (delta + delta_w >= 1024) {
2597 /* how much left for next period will start over, we don't know yet */
2598 sa->period_contrib = 0;
2601 * Now that we know we're crossing a period boundary, figure
2602 * out how much from delta we need to complete the current
2603 * period and accrue it.
2605 delta_w = 1024 - delta_w;
2606 scaled_delta_w = cap_scale(delta_w, scale_freq);
2608 sa->load_sum += weight * scaled_delta_w;
2610 cfs_rq->runnable_load_sum +=
2611 weight * scaled_delta_w;
2615 sa->util_sum += scaled_delta_w * scale_cpu;
2619 /* Figure out how many additional periods this update spans */
2620 periods = delta / 1024;
2623 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2625 cfs_rq->runnable_load_sum =
2626 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2628 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2630 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2631 contrib = __compute_runnable_contrib(periods);
2632 contrib = cap_scale(contrib, scale_freq);
2634 sa->load_sum += weight * contrib;
2636 cfs_rq->runnable_load_sum += weight * contrib;
2639 sa->util_sum += contrib * scale_cpu;
2642 /* Remainder of delta accrued against u_0` */
2643 scaled_delta = cap_scale(delta, scale_freq);
2645 sa->load_sum += weight * scaled_delta;
2647 cfs_rq->runnable_load_sum += weight * scaled_delta;
2650 sa->util_sum += scaled_delta * scale_cpu;
2652 sa->period_contrib += delta;
2655 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2657 cfs_rq->runnable_load_avg =
2658 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2660 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2666 #ifdef CONFIG_FAIR_GROUP_SCHED
2668 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2669 * and effective_load (which is not done because it is too costly).
2671 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2673 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2675 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2676 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2677 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2681 #else /* CONFIG_FAIR_GROUP_SCHED */
2682 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2683 #endif /* CONFIG_FAIR_GROUP_SCHED */
2685 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2687 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2688 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2690 struct sched_avg *sa = &cfs_rq->avg;
2691 int decayed, removed = 0;
2693 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2694 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2695 sa->load_avg = max_t(long, sa->load_avg - r, 0);
2696 sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2700 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2701 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2702 sa->util_avg = max_t(long, sa->util_avg - r, 0);
2703 sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2706 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2707 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2709 #ifndef CONFIG_64BIT
2711 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2714 return decayed || removed;
2717 /* Update task and its cfs_rq load average */
2718 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2720 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2721 u64 now = cfs_rq_clock_task(cfs_rq);
2722 int cpu = cpu_of(rq_of(cfs_rq));
2725 * Track task load average for carrying it to new CPU after migrated, and
2726 * track group sched_entity load average for task_h_load calc in migration
2728 __update_load_avg(now, cpu, &se->avg,
2729 se->on_rq * scale_load_down(se->load.weight),
2730 cfs_rq->curr == se, NULL);
2732 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2733 update_tg_load_avg(cfs_rq, 0);
2735 if (entity_is_task(se))
2736 trace_sched_load_avg_task(task_of(se), &se->avg);
2739 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2741 if (!sched_feat(ATTACH_AGE_LOAD))
2745 * If we got migrated (either between CPUs or between cgroups) we'll
2746 * have aged the average right before clearing @last_update_time.
2748 if (se->avg.last_update_time) {
2749 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2750 &se->avg, 0, 0, NULL);
2753 * XXX: we could have just aged the entire load away if we've been
2754 * absent from the fair class for too long.
2759 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2760 cfs_rq->avg.load_avg += se->avg.load_avg;
2761 cfs_rq->avg.load_sum += se->avg.load_sum;
2762 cfs_rq->avg.util_avg += se->avg.util_avg;
2763 cfs_rq->avg.util_sum += se->avg.util_sum;
2766 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2768 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2769 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2770 cfs_rq->curr == se, NULL);
2772 cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
2773 cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
2774 cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
2775 cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
2778 /* Add the load generated by se into cfs_rq's load average */
2780 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2782 struct sched_avg *sa = &se->avg;
2783 u64 now = cfs_rq_clock_task(cfs_rq);
2784 int migrated, decayed;
2786 migrated = !sa->last_update_time;
2788 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2789 se->on_rq * scale_load_down(se->load.weight),
2790 cfs_rq->curr == se, NULL);
2793 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2795 cfs_rq->runnable_load_avg += sa->load_avg;
2796 cfs_rq->runnable_load_sum += sa->load_sum;
2799 attach_entity_load_avg(cfs_rq, se);
2801 if (decayed || migrated)
2802 update_tg_load_avg(cfs_rq, 0);
2805 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2807 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2809 update_load_avg(se, 1);
2811 cfs_rq->runnable_load_avg =
2812 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2813 cfs_rq->runnable_load_sum =
2814 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2817 #ifndef CONFIG_64BIT
2818 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2820 u64 last_update_time_copy;
2821 u64 last_update_time;
2824 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2826 last_update_time = cfs_rq->avg.last_update_time;
2827 } while (last_update_time != last_update_time_copy);
2829 return last_update_time;
2832 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2834 return cfs_rq->avg.last_update_time;
2839 * Task first catches up with cfs_rq, and then subtract
2840 * itself from the cfs_rq (task must be off the queue now).
2842 void remove_entity_load_avg(struct sched_entity *se)
2844 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2845 u64 last_update_time;
2848 * Newly created task or never used group entity should not be removed
2849 * from its (source) cfs_rq
2851 if (se->avg.last_update_time == 0)
2854 last_update_time = cfs_rq_last_update_time(cfs_rq);
2856 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2857 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2858 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2862 * Update the rq's load with the elapsed running time before entering
2863 * idle. if the last scheduled task is not a CFS task, idle_enter will
2864 * be the only way to update the runnable statistic.
2866 void idle_enter_fair(struct rq *this_rq)
2871 * Update the rq's load with the elapsed idle time before a task is
2872 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2873 * be the only way to update the runnable statistic.
2875 void idle_exit_fair(struct rq *this_rq)
2879 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2881 return cfs_rq->runnable_load_avg;
2884 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2886 return cfs_rq->avg.load_avg;
2889 static int idle_balance(struct rq *this_rq);
2891 #else /* CONFIG_SMP */
2893 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2895 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2897 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2898 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2901 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2903 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2905 static inline int idle_balance(struct rq *rq)
2910 #endif /* CONFIG_SMP */
2912 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2914 #ifdef CONFIG_SCHEDSTATS
2915 struct task_struct *tsk = NULL;
2917 if (entity_is_task(se))
2920 if (se->statistics.sleep_start) {
2921 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2926 if (unlikely(delta > se->statistics.sleep_max))
2927 se->statistics.sleep_max = delta;
2929 se->statistics.sleep_start = 0;
2930 se->statistics.sum_sleep_runtime += delta;
2933 account_scheduler_latency(tsk, delta >> 10, 1);
2934 trace_sched_stat_sleep(tsk, delta);
2937 if (se->statistics.block_start) {
2938 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2943 if (unlikely(delta > se->statistics.block_max))
2944 se->statistics.block_max = delta;
2946 se->statistics.block_start = 0;
2947 se->statistics.sum_sleep_runtime += delta;
2950 if (tsk->in_iowait) {
2951 se->statistics.iowait_sum += delta;
2952 se->statistics.iowait_count++;
2953 trace_sched_stat_iowait(tsk, delta);
2956 trace_sched_stat_blocked(tsk, delta);
2959 * Blocking time is in units of nanosecs, so shift by
2960 * 20 to get a milliseconds-range estimation of the
2961 * amount of time that the task spent sleeping:
2963 if (unlikely(prof_on == SLEEP_PROFILING)) {
2964 profile_hits(SLEEP_PROFILING,
2965 (void *)get_wchan(tsk),
2968 account_scheduler_latency(tsk, delta >> 10, 0);
2974 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2976 #ifdef CONFIG_SCHED_DEBUG
2977 s64 d = se->vruntime - cfs_rq->min_vruntime;
2982 if (d > 3*sysctl_sched_latency)
2983 schedstat_inc(cfs_rq, nr_spread_over);
2988 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
2990 u64 vruntime = cfs_rq->min_vruntime;
2993 * The 'current' period is already promised to the current tasks,
2994 * however the extra weight of the new task will slow them down a
2995 * little, place the new task so that it fits in the slot that
2996 * stays open at the end.
2998 if (initial && sched_feat(START_DEBIT))
2999 vruntime += sched_vslice(cfs_rq, se);
3001 /* sleeps up to a single latency don't count. */
3003 unsigned long thresh = sysctl_sched_latency;
3006 * Halve their sleep time's effect, to allow
3007 * for a gentler effect of sleepers:
3009 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3015 /* ensure we never gain time by being placed backwards. */
3016 se->vruntime = max_vruntime(se->vruntime, vruntime);
3019 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3022 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3025 * Update the normalized vruntime before updating min_vruntime
3026 * through calling update_curr().
3028 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3029 se->vruntime += cfs_rq->min_vruntime;
3032 * Update run-time statistics of the 'current'.
3034 update_curr(cfs_rq);
3035 enqueue_entity_load_avg(cfs_rq, se);
3036 account_entity_enqueue(cfs_rq, se);
3037 update_cfs_shares(cfs_rq);
3039 if (flags & ENQUEUE_WAKEUP) {
3040 place_entity(cfs_rq, se, 0);
3041 enqueue_sleeper(cfs_rq, se);
3044 update_stats_enqueue(cfs_rq, se);
3045 check_spread(cfs_rq, se);
3046 if (se != cfs_rq->curr)
3047 __enqueue_entity(cfs_rq, se);
3050 if (cfs_rq->nr_running == 1) {
3051 list_add_leaf_cfs_rq(cfs_rq);
3052 check_enqueue_throttle(cfs_rq);
3056 static void __clear_buddies_last(struct sched_entity *se)
3058 for_each_sched_entity(se) {
3059 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3060 if (cfs_rq->last != se)
3063 cfs_rq->last = NULL;
3067 static void __clear_buddies_next(struct sched_entity *se)
3069 for_each_sched_entity(se) {
3070 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3071 if (cfs_rq->next != se)
3074 cfs_rq->next = NULL;
3078 static void __clear_buddies_skip(struct sched_entity *se)
3080 for_each_sched_entity(se) {
3081 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3082 if (cfs_rq->skip != se)
3085 cfs_rq->skip = NULL;
3089 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3091 if (cfs_rq->last == se)
3092 __clear_buddies_last(se);
3094 if (cfs_rq->next == se)
3095 __clear_buddies_next(se);
3097 if (cfs_rq->skip == se)
3098 __clear_buddies_skip(se);
3101 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3104 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3107 * Update run-time statistics of the 'current'.
3109 update_curr(cfs_rq);
3110 dequeue_entity_load_avg(cfs_rq, se);
3112 update_stats_dequeue(cfs_rq, se);
3113 if (flags & DEQUEUE_SLEEP) {
3114 #ifdef CONFIG_SCHEDSTATS
3115 if (entity_is_task(se)) {
3116 struct task_struct *tsk = task_of(se);
3118 if (tsk->state & TASK_INTERRUPTIBLE)
3119 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3120 if (tsk->state & TASK_UNINTERRUPTIBLE)
3121 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3126 clear_buddies(cfs_rq, se);
3128 if (se != cfs_rq->curr)
3129 __dequeue_entity(cfs_rq, se);
3131 account_entity_dequeue(cfs_rq, se);
3134 * Normalize the entity after updating the min_vruntime because the
3135 * update can refer to the ->curr item and we need to reflect this
3136 * movement in our normalized position.
3138 if (!(flags & DEQUEUE_SLEEP))
3139 se->vruntime -= cfs_rq->min_vruntime;
3141 /* return excess runtime on last dequeue */
3142 return_cfs_rq_runtime(cfs_rq);
3144 update_min_vruntime(cfs_rq);
3145 update_cfs_shares(cfs_rq);
3149 * Preempt the current task with a newly woken task if needed:
3152 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3154 unsigned long ideal_runtime, delta_exec;
3155 struct sched_entity *se;
3158 ideal_runtime = sched_slice(cfs_rq, curr);
3159 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3160 if (delta_exec > ideal_runtime) {
3161 resched_curr(rq_of(cfs_rq));
3163 * The current task ran long enough, ensure it doesn't get
3164 * re-elected due to buddy favours.
3166 clear_buddies(cfs_rq, curr);
3171 * Ensure that a task that missed wakeup preemption by a
3172 * narrow margin doesn't have to wait for a full slice.
3173 * This also mitigates buddy induced latencies under load.
3175 if (delta_exec < sysctl_sched_min_granularity)
3178 se = __pick_first_entity(cfs_rq);
3179 delta = curr->vruntime - se->vruntime;
3184 if (delta > ideal_runtime)
3185 resched_curr(rq_of(cfs_rq));
3189 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3191 /* 'current' is not kept within the tree. */
3194 * Any task has to be enqueued before it get to execute on
3195 * a CPU. So account for the time it spent waiting on the
3198 update_stats_wait_end(cfs_rq, se);
3199 __dequeue_entity(cfs_rq, se);
3200 update_load_avg(se, 1);
3203 update_stats_curr_start(cfs_rq, se);
3205 #ifdef CONFIG_SCHEDSTATS
3207 * Track our maximum slice length, if the CPU's load is at
3208 * least twice that of our own weight (i.e. dont track it
3209 * when there are only lesser-weight tasks around):
3211 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3212 se->statistics.slice_max = max(se->statistics.slice_max,
3213 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3216 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3220 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3223 * Pick the next process, keeping these things in mind, in this order:
3224 * 1) keep things fair between processes/task groups
3225 * 2) pick the "next" process, since someone really wants that to run
3226 * 3) pick the "last" process, for cache locality
3227 * 4) do not run the "skip" process, if something else is available
3229 static struct sched_entity *
3230 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3232 struct sched_entity *left = __pick_first_entity(cfs_rq);
3233 struct sched_entity *se;
3236 * If curr is set we have to see if its left of the leftmost entity
3237 * still in the tree, provided there was anything in the tree at all.
3239 if (!left || (curr && entity_before(curr, left)))
3242 se = left; /* ideally we run the leftmost entity */
3245 * Avoid running the skip buddy, if running something else can
3246 * be done without getting too unfair.
3248 if (cfs_rq->skip == se) {
3249 struct sched_entity *second;
3252 second = __pick_first_entity(cfs_rq);
3254 second = __pick_next_entity(se);
3255 if (!second || (curr && entity_before(curr, second)))
3259 if (second && wakeup_preempt_entity(second, left) < 1)
3264 * Prefer last buddy, try to return the CPU to a preempted task.
3266 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3270 * Someone really wants this to run. If it's not unfair, run it.
3272 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3275 clear_buddies(cfs_rq, se);
3280 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3282 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3285 * If still on the runqueue then deactivate_task()
3286 * was not called and update_curr() has to be done:
3289 update_curr(cfs_rq);
3291 /* throttle cfs_rqs exceeding runtime */
3292 check_cfs_rq_runtime(cfs_rq);
3294 check_spread(cfs_rq, prev);
3296 update_stats_wait_start(cfs_rq, prev);
3297 /* Put 'current' back into the tree. */
3298 __enqueue_entity(cfs_rq, prev);
3299 /* in !on_rq case, update occurred at dequeue */
3300 update_load_avg(prev, 0);
3302 cfs_rq->curr = NULL;
3306 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3309 * Update run-time statistics of the 'current'.
3311 update_curr(cfs_rq);
3314 * Ensure that runnable average is periodically updated.
3316 update_load_avg(curr, 1);
3317 update_cfs_shares(cfs_rq);
3319 #ifdef CONFIG_SCHED_HRTICK
3321 * queued ticks are scheduled to match the slice, so don't bother
3322 * validating it and just reschedule.
3325 resched_curr(rq_of(cfs_rq));
3329 * don't let the period tick interfere with the hrtick preemption
3331 if (!sched_feat(DOUBLE_TICK) &&
3332 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3336 if (cfs_rq->nr_running > 1)
3337 check_preempt_tick(cfs_rq, curr);
3341 /**************************************************
3342 * CFS bandwidth control machinery
3345 #ifdef CONFIG_CFS_BANDWIDTH
3347 #ifdef HAVE_JUMP_LABEL
3348 static struct static_key __cfs_bandwidth_used;
3350 static inline bool cfs_bandwidth_used(void)
3352 return static_key_false(&__cfs_bandwidth_used);
3355 void cfs_bandwidth_usage_inc(void)
3357 static_key_slow_inc(&__cfs_bandwidth_used);
3360 void cfs_bandwidth_usage_dec(void)
3362 static_key_slow_dec(&__cfs_bandwidth_used);
3364 #else /* HAVE_JUMP_LABEL */
3365 static bool cfs_bandwidth_used(void)
3370 void cfs_bandwidth_usage_inc(void) {}
3371 void cfs_bandwidth_usage_dec(void) {}
3372 #endif /* HAVE_JUMP_LABEL */
3375 * default period for cfs group bandwidth.
3376 * default: 0.1s, units: nanoseconds
3378 static inline u64 default_cfs_period(void)
3380 return 100000000ULL;
3383 static inline u64 sched_cfs_bandwidth_slice(void)
3385 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3389 * Replenish runtime according to assigned quota and update expiration time.
3390 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3391 * additional synchronization around rq->lock.
3393 * requires cfs_b->lock
3395 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3399 if (cfs_b->quota == RUNTIME_INF)
3402 now = sched_clock_cpu(smp_processor_id());
3403 cfs_b->runtime = cfs_b->quota;
3404 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3407 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3409 return &tg->cfs_bandwidth;
3412 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3413 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3415 if (unlikely(cfs_rq->throttle_count))
3416 return cfs_rq->throttled_clock_task;
3418 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3421 /* returns 0 on failure to allocate runtime */
3422 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3424 struct task_group *tg = cfs_rq->tg;
3425 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3426 u64 amount = 0, min_amount, expires;
3428 /* note: this is a positive sum as runtime_remaining <= 0 */
3429 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3431 raw_spin_lock(&cfs_b->lock);
3432 if (cfs_b->quota == RUNTIME_INF)
3433 amount = min_amount;
3435 start_cfs_bandwidth(cfs_b);
3437 if (cfs_b->runtime > 0) {
3438 amount = min(cfs_b->runtime, min_amount);
3439 cfs_b->runtime -= amount;
3443 expires = cfs_b->runtime_expires;
3444 raw_spin_unlock(&cfs_b->lock);
3446 cfs_rq->runtime_remaining += amount;
3448 * we may have advanced our local expiration to account for allowed
3449 * spread between our sched_clock and the one on which runtime was
3452 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3453 cfs_rq->runtime_expires = expires;
3455 return cfs_rq->runtime_remaining > 0;
3459 * Note: This depends on the synchronization provided by sched_clock and the
3460 * fact that rq->clock snapshots this value.
3462 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3464 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3466 /* if the deadline is ahead of our clock, nothing to do */
3467 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3470 if (cfs_rq->runtime_remaining < 0)
3474 * If the local deadline has passed we have to consider the
3475 * possibility that our sched_clock is 'fast' and the global deadline
3476 * has not truly expired.
3478 * Fortunately we can check determine whether this the case by checking
3479 * whether the global deadline has advanced. It is valid to compare
3480 * cfs_b->runtime_expires without any locks since we only care about
3481 * exact equality, so a partial write will still work.
3484 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3485 /* extend local deadline, drift is bounded above by 2 ticks */
3486 cfs_rq->runtime_expires += TICK_NSEC;
3488 /* global deadline is ahead, expiration has passed */
3489 cfs_rq->runtime_remaining = 0;
3493 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3495 /* dock delta_exec before expiring quota (as it could span periods) */
3496 cfs_rq->runtime_remaining -= delta_exec;
3497 expire_cfs_rq_runtime(cfs_rq);
3499 if (likely(cfs_rq->runtime_remaining > 0))
3503 * if we're unable to extend our runtime we resched so that the active
3504 * hierarchy can be throttled
3506 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3507 resched_curr(rq_of(cfs_rq));
3510 static __always_inline
3511 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3513 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3516 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3519 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3521 return cfs_bandwidth_used() && cfs_rq->throttled;
3524 /* check whether cfs_rq, or any parent, is throttled */
3525 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3527 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3531 * Ensure that neither of the group entities corresponding to src_cpu or
3532 * dest_cpu are members of a throttled hierarchy when performing group
3533 * load-balance operations.
3535 static inline int throttled_lb_pair(struct task_group *tg,
3536 int src_cpu, int dest_cpu)
3538 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3540 src_cfs_rq = tg->cfs_rq[src_cpu];
3541 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3543 return throttled_hierarchy(src_cfs_rq) ||
3544 throttled_hierarchy(dest_cfs_rq);
3547 /* updated child weight may affect parent so we have to do this bottom up */
3548 static int tg_unthrottle_up(struct task_group *tg, void *data)
3550 struct rq *rq = data;
3551 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3553 cfs_rq->throttle_count--;
3555 if (!cfs_rq->throttle_count) {
3556 /* adjust cfs_rq_clock_task() */
3557 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3558 cfs_rq->throttled_clock_task;
3565 static int tg_throttle_down(struct task_group *tg, void *data)
3567 struct rq *rq = data;
3568 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3570 /* group is entering throttled state, stop time */
3571 if (!cfs_rq->throttle_count)
3572 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3573 cfs_rq->throttle_count++;
3578 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3580 struct rq *rq = rq_of(cfs_rq);
3581 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3582 struct sched_entity *se;
3583 long task_delta, dequeue = 1;
3586 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3588 /* freeze hierarchy runnable averages while throttled */
3590 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3593 task_delta = cfs_rq->h_nr_running;
3594 for_each_sched_entity(se) {
3595 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3596 /* throttled entity or throttle-on-deactivate */
3601 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3602 qcfs_rq->h_nr_running -= task_delta;
3604 if (qcfs_rq->load.weight)
3609 sub_nr_running(rq, task_delta);
3611 cfs_rq->throttled = 1;
3612 cfs_rq->throttled_clock = rq_clock(rq);
3613 raw_spin_lock(&cfs_b->lock);
3614 empty = list_empty(&cfs_b->throttled_cfs_rq);
3617 * Add to the _head_ of the list, so that an already-started
3618 * distribute_cfs_runtime will not see us
3620 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3623 * If we're the first throttled task, make sure the bandwidth
3627 start_cfs_bandwidth(cfs_b);
3629 raw_spin_unlock(&cfs_b->lock);
3632 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3634 struct rq *rq = rq_of(cfs_rq);
3635 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3636 struct sched_entity *se;
3640 se = cfs_rq->tg->se[cpu_of(rq)];
3642 cfs_rq->throttled = 0;
3644 update_rq_clock(rq);
3646 raw_spin_lock(&cfs_b->lock);
3647 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3648 list_del_rcu(&cfs_rq->throttled_list);
3649 raw_spin_unlock(&cfs_b->lock);
3651 /* update hierarchical throttle state */
3652 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3654 if (!cfs_rq->load.weight)
3657 task_delta = cfs_rq->h_nr_running;
3658 for_each_sched_entity(se) {
3662 cfs_rq = cfs_rq_of(se);
3664 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3665 cfs_rq->h_nr_running += task_delta;
3667 if (cfs_rq_throttled(cfs_rq))
3672 add_nr_running(rq, task_delta);
3674 /* determine whether we need to wake up potentially idle cpu */
3675 if (rq->curr == rq->idle && rq->cfs.nr_running)
3679 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3680 u64 remaining, u64 expires)
3682 struct cfs_rq *cfs_rq;
3684 u64 starting_runtime = remaining;
3687 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3689 struct rq *rq = rq_of(cfs_rq);
3691 raw_spin_lock(&rq->lock);
3692 if (!cfs_rq_throttled(cfs_rq))
3695 runtime = -cfs_rq->runtime_remaining + 1;
3696 if (runtime > remaining)
3697 runtime = remaining;
3698 remaining -= runtime;
3700 cfs_rq->runtime_remaining += runtime;
3701 cfs_rq->runtime_expires = expires;
3703 /* we check whether we're throttled above */
3704 if (cfs_rq->runtime_remaining > 0)
3705 unthrottle_cfs_rq(cfs_rq);
3708 raw_spin_unlock(&rq->lock);
3715 return starting_runtime - remaining;
3719 * Responsible for refilling a task_group's bandwidth and unthrottling its
3720 * cfs_rqs as appropriate. If there has been no activity within the last
3721 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3722 * used to track this state.
3724 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3726 u64 runtime, runtime_expires;
3729 /* no need to continue the timer with no bandwidth constraint */
3730 if (cfs_b->quota == RUNTIME_INF)
3731 goto out_deactivate;
3733 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3734 cfs_b->nr_periods += overrun;
3737 * idle depends on !throttled (for the case of a large deficit), and if
3738 * we're going inactive then everything else can be deferred
3740 if (cfs_b->idle && !throttled)
3741 goto out_deactivate;
3743 __refill_cfs_bandwidth_runtime(cfs_b);
3746 /* mark as potentially idle for the upcoming period */
3751 /* account preceding periods in which throttling occurred */
3752 cfs_b->nr_throttled += overrun;
3754 runtime_expires = cfs_b->runtime_expires;
3757 * This check is repeated as we are holding onto the new bandwidth while
3758 * we unthrottle. This can potentially race with an unthrottled group
3759 * trying to acquire new bandwidth from the global pool. This can result
3760 * in us over-using our runtime if it is all used during this loop, but
3761 * only by limited amounts in that extreme case.
3763 while (throttled && cfs_b->runtime > 0) {
3764 runtime = cfs_b->runtime;
3765 raw_spin_unlock(&cfs_b->lock);
3766 /* we can't nest cfs_b->lock while distributing bandwidth */
3767 runtime = distribute_cfs_runtime(cfs_b, runtime,
3769 raw_spin_lock(&cfs_b->lock);
3771 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3773 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3777 * While we are ensured activity in the period following an
3778 * unthrottle, this also covers the case in which the new bandwidth is
3779 * insufficient to cover the existing bandwidth deficit. (Forcing the
3780 * timer to remain active while there are any throttled entities.)
3790 /* a cfs_rq won't donate quota below this amount */
3791 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3792 /* minimum remaining period time to redistribute slack quota */
3793 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3794 /* how long we wait to gather additional slack before distributing */
3795 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3798 * Are we near the end of the current quota period?
3800 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3801 * hrtimer base being cleared by hrtimer_start. In the case of
3802 * migrate_hrtimers, base is never cleared, so we are fine.
3804 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3806 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3809 /* if the call-back is running a quota refresh is already occurring */
3810 if (hrtimer_callback_running(refresh_timer))
3813 /* is a quota refresh about to occur? */
3814 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3815 if (remaining < min_expire)
3821 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3823 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3825 /* if there's a quota refresh soon don't bother with slack */
3826 if (runtime_refresh_within(cfs_b, min_left))
3829 hrtimer_start(&cfs_b->slack_timer,
3830 ns_to_ktime(cfs_bandwidth_slack_period),
3834 /* we know any runtime found here is valid as update_curr() precedes return */
3835 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3837 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3838 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3840 if (slack_runtime <= 0)
3843 raw_spin_lock(&cfs_b->lock);
3844 if (cfs_b->quota != RUNTIME_INF &&
3845 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3846 cfs_b->runtime += slack_runtime;
3848 /* we are under rq->lock, defer unthrottling using a timer */
3849 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3850 !list_empty(&cfs_b->throttled_cfs_rq))
3851 start_cfs_slack_bandwidth(cfs_b);
3853 raw_spin_unlock(&cfs_b->lock);
3855 /* even if it's not valid for return we don't want to try again */
3856 cfs_rq->runtime_remaining -= slack_runtime;
3859 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3861 if (!cfs_bandwidth_used())
3864 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3867 __return_cfs_rq_runtime(cfs_rq);
3871 * This is done with a timer (instead of inline with bandwidth return) since
3872 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3874 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3876 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3879 /* confirm we're still not at a refresh boundary */
3880 raw_spin_lock(&cfs_b->lock);
3881 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3882 raw_spin_unlock(&cfs_b->lock);
3886 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3887 runtime = cfs_b->runtime;
3889 expires = cfs_b->runtime_expires;
3890 raw_spin_unlock(&cfs_b->lock);
3895 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3897 raw_spin_lock(&cfs_b->lock);
3898 if (expires == cfs_b->runtime_expires)
3899 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3900 raw_spin_unlock(&cfs_b->lock);
3904 * When a group wakes up we want to make sure that its quota is not already
3905 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3906 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3908 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3910 if (!cfs_bandwidth_used())
3913 /* an active group must be handled by the update_curr()->put() path */
3914 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3917 /* ensure the group is not already throttled */
3918 if (cfs_rq_throttled(cfs_rq))
3921 /* update runtime allocation */
3922 account_cfs_rq_runtime(cfs_rq, 0);
3923 if (cfs_rq->runtime_remaining <= 0)
3924 throttle_cfs_rq(cfs_rq);
3927 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3928 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3930 if (!cfs_bandwidth_used())
3933 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3937 * it's possible for a throttled entity to be forced into a running
3938 * state (e.g. set_curr_task), in this case we're finished.
3940 if (cfs_rq_throttled(cfs_rq))
3943 throttle_cfs_rq(cfs_rq);
3947 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3949 struct cfs_bandwidth *cfs_b =
3950 container_of(timer, struct cfs_bandwidth, slack_timer);
3952 do_sched_cfs_slack_timer(cfs_b);
3954 return HRTIMER_NORESTART;
3957 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3959 struct cfs_bandwidth *cfs_b =
3960 container_of(timer, struct cfs_bandwidth, period_timer);
3964 raw_spin_lock(&cfs_b->lock);
3966 overrun = hrtimer_forward_now(timer, cfs_b->period);
3970 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3973 cfs_b->period_active = 0;
3974 raw_spin_unlock(&cfs_b->lock);
3976 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3979 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3981 raw_spin_lock_init(&cfs_b->lock);
3983 cfs_b->quota = RUNTIME_INF;
3984 cfs_b->period = ns_to_ktime(default_cfs_period());
3986 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
3987 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3988 cfs_b->period_timer.function = sched_cfs_period_timer;
3989 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
3990 cfs_b->slack_timer.function = sched_cfs_slack_timer;
3993 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3995 cfs_rq->runtime_enabled = 0;
3996 INIT_LIST_HEAD(&cfs_rq->throttled_list);
3999 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4001 lockdep_assert_held(&cfs_b->lock);
4003 if (!cfs_b->period_active) {
4004 cfs_b->period_active = 1;
4005 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4006 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4010 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4012 /* init_cfs_bandwidth() was not called */
4013 if (!cfs_b->throttled_cfs_rq.next)
4016 hrtimer_cancel(&cfs_b->period_timer);
4017 hrtimer_cancel(&cfs_b->slack_timer);
4020 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4022 struct cfs_rq *cfs_rq;
4024 for_each_leaf_cfs_rq(rq, cfs_rq) {
4025 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4027 raw_spin_lock(&cfs_b->lock);
4028 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4029 raw_spin_unlock(&cfs_b->lock);
4033 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4035 struct cfs_rq *cfs_rq;
4037 for_each_leaf_cfs_rq(rq, cfs_rq) {
4038 if (!cfs_rq->runtime_enabled)
4042 * clock_task is not advancing so we just need to make sure
4043 * there's some valid quota amount
4045 cfs_rq->runtime_remaining = 1;
4047 * Offline rq is schedulable till cpu is completely disabled
4048 * in take_cpu_down(), so we prevent new cfs throttling here.
4050 cfs_rq->runtime_enabled = 0;
4052 if (cfs_rq_throttled(cfs_rq))
4053 unthrottle_cfs_rq(cfs_rq);
4057 #else /* CONFIG_CFS_BANDWIDTH */
4058 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4060 return rq_clock_task(rq_of(cfs_rq));
4063 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4064 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4065 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4066 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4068 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4073 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4078 static inline int throttled_lb_pair(struct task_group *tg,
4079 int src_cpu, int dest_cpu)
4084 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4086 #ifdef CONFIG_FAIR_GROUP_SCHED
4087 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4090 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4094 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4095 static inline void update_runtime_enabled(struct rq *rq) {}
4096 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4098 #endif /* CONFIG_CFS_BANDWIDTH */
4100 /**************************************************
4101 * CFS operations on tasks:
4104 #ifdef CONFIG_SCHED_HRTICK
4105 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4107 struct sched_entity *se = &p->se;
4108 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4110 WARN_ON(task_rq(p) != rq);
4112 if (cfs_rq->nr_running > 1) {
4113 u64 slice = sched_slice(cfs_rq, se);
4114 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4115 s64 delta = slice - ran;
4122 hrtick_start(rq, delta);
4127 * called from enqueue/dequeue and updates the hrtick when the
4128 * current task is from our class and nr_running is low enough
4131 static void hrtick_update(struct rq *rq)
4133 struct task_struct *curr = rq->curr;
4135 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4138 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4139 hrtick_start_fair(rq, curr);
4141 #else /* !CONFIG_SCHED_HRTICK */
4143 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4147 static inline void hrtick_update(struct rq *rq)
4152 static inline unsigned long boosted_cpu_util(int cpu);
4154 static void update_capacity_of(int cpu)
4156 unsigned long req_cap;
4161 /* Convert scale-invariant capacity to cpu. */
4162 req_cap = boosted_cpu_util(cpu);
4163 req_cap = req_cap * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
4164 set_cfs_cpu_capacity(cpu, true, req_cap);
4167 static bool cpu_overutilized(int cpu);
4170 * The enqueue_task method is called before nr_running is
4171 * increased. Here we update the fair scheduling stats and
4172 * then put the task into the rbtree:
4175 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4177 struct cfs_rq *cfs_rq;
4178 struct sched_entity *se = &p->se;
4179 int task_new = flags & ENQUEUE_WAKEUP_NEW;
4180 int task_wakeup = flags & ENQUEUE_WAKEUP;
4182 for_each_sched_entity(se) {
4185 cfs_rq = cfs_rq_of(se);
4186 enqueue_entity(cfs_rq, se, flags);
4189 * end evaluation on encountering a throttled cfs_rq
4191 * note: in the case of encountering a throttled cfs_rq we will
4192 * post the final h_nr_running increment below.
4194 if (cfs_rq_throttled(cfs_rq))
4196 cfs_rq->h_nr_running++;
4198 flags = ENQUEUE_WAKEUP;
4201 for_each_sched_entity(se) {
4202 cfs_rq = cfs_rq_of(se);
4203 cfs_rq->h_nr_running++;
4205 if (cfs_rq_throttled(cfs_rq))
4208 update_load_avg(se, 1);
4209 update_cfs_shares(cfs_rq);
4213 add_nr_running(rq, 1);
4214 if (!task_new && !rq->rd->overutilized &&
4215 cpu_overutilized(rq->cpu))
4216 rq->rd->overutilized = true;
4218 schedtune_enqueue_task(p, cpu_of(rq));
4221 * We want to potentially trigger a freq switch
4222 * request only for tasks that are waking up; this is
4223 * because we get here also during load balancing, but
4224 * in these cases it seems wise to trigger as single
4225 * request after load balancing is done.
4227 if (task_new || task_wakeup)
4228 update_capacity_of(cpu_of(rq));
4233 static void set_next_buddy(struct sched_entity *se);
4236 * The dequeue_task method is called before nr_running is
4237 * decreased. We remove the task from the rbtree and
4238 * update the fair scheduling stats:
4240 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4242 struct cfs_rq *cfs_rq;
4243 struct sched_entity *se = &p->se;
4244 int task_sleep = flags & DEQUEUE_SLEEP;
4246 for_each_sched_entity(se) {
4247 cfs_rq = cfs_rq_of(se);
4248 dequeue_entity(cfs_rq, se, flags);
4251 * end evaluation on encountering a throttled cfs_rq
4253 * note: in the case of encountering a throttled cfs_rq we will
4254 * post the final h_nr_running decrement below.
4256 if (cfs_rq_throttled(cfs_rq))
4258 cfs_rq->h_nr_running--;
4260 /* Don't dequeue parent if it has other entities besides us */
4261 if (cfs_rq->load.weight) {
4263 * Bias pick_next to pick a task from this cfs_rq, as
4264 * p is sleeping when it is within its sched_slice.
4266 if (task_sleep && parent_entity(se))
4267 set_next_buddy(parent_entity(se));
4269 /* avoid re-evaluating load for this entity */
4270 se = parent_entity(se);
4273 flags |= DEQUEUE_SLEEP;
4276 for_each_sched_entity(se) {
4277 cfs_rq = cfs_rq_of(se);
4278 cfs_rq->h_nr_running--;
4280 if (cfs_rq_throttled(cfs_rq))
4283 update_load_avg(se, 1);
4284 update_cfs_shares(cfs_rq);
4288 sub_nr_running(rq, 1);
4289 schedtune_dequeue_task(p, cpu_of(rq));
4292 * We want to potentially trigger a freq switch
4293 * request only for tasks that are going to sleep;
4294 * this is because we get here also during load
4295 * balancing, but in these cases it seems wise to
4296 * trigger as single request after load balancing is
4300 if (rq->cfs.nr_running)
4301 update_capacity_of(cpu_of(rq));
4302 else if (sched_freq())
4303 set_cfs_cpu_capacity(cpu_of(rq), false, 0);
4312 * per rq 'load' arrray crap; XXX kill this.
4316 * The exact cpuload at various idx values, calculated at every tick would be
4317 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4319 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4320 * on nth tick when cpu may be busy, then we have:
4321 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4322 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4324 * decay_load_missed() below does efficient calculation of
4325 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4326 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4328 * The calculation is approximated on a 128 point scale.
4329 * degrade_zero_ticks is the number of ticks after which load at any
4330 * particular idx is approximated to be zero.
4331 * degrade_factor is a precomputed table, a row for each load idx.
4332 * Each column corresponds to degradation factor for a power of two ticks,
4333 * based on 128 point scale.
4335 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4336 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4338 * With this power of 2 load factors, we can degrade the load n times
4339 * by looking at 1 bits in n and doing as many mult/shift instead of
4340 * n mult/shifts needed by the exact degradation.
4342 #define DEGRADE_SHIFT 7
4343 static const unsigned char
4344 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4345 static const unsigned char
4346 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4347 {0, 0, 0, 0, 0, 0, 0, 0},
4348 {64, 32, 8, 0, 0, 0, 0, 0},
4349 {96, 72, 40, 12, 1, 0, 0},
4350 {112, 98, 75, 43, 15, 1, 0},
4351 {120, 112, 98, 76, 45, 16, 2} };
4354 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4355 * would be when CPU is idle and so we just decay the old load without
4356 * adding any new load.
4358 static unsigned long
4359 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4363 if (!missed_updates)
4366 if (missed_updates >= degrade_zero_ticks[idx])
4370 return load >> missed_updates;
4372 while (missed_updates) {
4373 if (missed_updates % 2)
4374 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4376 missed_updates >>= 1;
4383 * Update rq->cpu_load[] statistics. This function is usually called every
4384 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4385 * every tick. We fix it up based on jiffies.
4387 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4388 unsigned long pending_updates)
4392 this_rq->nr_load_updates++;
4394 /* Update our load: */
4395 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4396 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4397 unsigned long old_load, new_load;
4399 /* scale is effectively 1 << i now, and >> i divides by scale */
4401 old_load = this_rq->cpu_load[i];
4402 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4403 new_load = this_load;
4405 * Round up the averaging division if load is increasing. This
4406 * prevents us from getting stuck on 9 if the load is 10, for
4409 if (new_load > old_load)
4410 new_load += scale - 1;
4412 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4415 sched_avg_update(this_rq);
4418 /* Used instead of source_load when we know the type == 0 */
4419 static unsigned long weighted_cpuload(const int cpu)
4421 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4424 #ifdef CONFIG_NO_HZ_COMMON
4426 * There is no sane way to deal with nohz on smp when using jiffies because the
4427 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4428 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4430 * Therefore we cannot use the delta approach from the regular tick since that
4431 * would seriously skew the load calculation. However we'll make do for those
4432 * updates happening while idle (nohz_idle_balance) or coming out of idle
4433 * (tick_nohz_idle_exit).
4435 * This means we might still be one tick off for nohz periods.
4439 * Called from nohz_idle_balance() to update the load ratings before doing the
4442 static void update_idle_cpu_load(struct rq *this_rq)
4444 unsigned long curr_jiffies = READ_ONCE(jiffies);
4445 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4446 unsigned long pending_updates;
4449 * bail if there's load or we're actually up-to-date.
4451 if (load || curr_jiffies == this_rq->last_load_update_tick)
4454 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4455 this_rq->last_load_update_tick = curr_jiffies;
4457 __update_cpu_load(this_rq, load, pending_updates);
4461 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4463 void update_cpu_load_nohz(void)
4465 struct rq *this_rq = this_rq();
4466 unsigned long curr_jiffies = READ_ONCE(jiffies);
4467 unsigned long pending_updates;
4469 if (curr_jiffies == this_rq->last_load_update_tick)
4472 raw_spin_lock(&this_rq->lock);
4473 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4474 if (pending_updates) {
4475 this_rq->last_load_update_tick = curr_jiffies;
4477 * We were idle, this means load 0, the current load might be
4478 * !0 due to remote wakeups and the sort.
4480 __update_cpu_load(this_rq, 0, pending_updates);
4482 raw_spin_unlock(&this_rq->lock);
4484 #endif /* CONFIG_NO_HZ */
4487 * Called from scheduler_tick()
4489 void update_cpu_load_active(struct rq *this_rq)
4491 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4493 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4495 this_rq->last_load_update_tick = jiffies;
4496 __update_cpu_load(this_rq, load, 1);
4500 * Return a low guess at the load of a migration-source cpu weighted
4501 * according to the scheduling class and "nice" value.
4503 * We want to under-estimate the load of migration sources, to
4504 * balance conservatively.
4506 static unsigned long source_load(int cpu, int type)
4508 struct rq *rq = cpu_rq(cpu);
4509 unsigned long total = weighted_cpuload(cpu);
4511 if (type == 0 || !sched_feat(LB_BIAS))
4514 return min(rq->cpu_load[type-1], total);
4518 * Return a high guess at the load of a migration-target cpu weighted
4519 * according to the scheduling class and "nice" value.
4521 static unsigned long target_load(int cpu, int type)
4523 struct rq *rq = cpu_rq(cpu);
4524 unsigned long total = weighted_cpuload(cpu);
4526 if (type == 0 || !sched_feat(LB_BIAS))
4529 return max(rq->cpu_load[type-1], total);
4533 static unsigned long cpu_avg_load_per_task(int cpu)
4535 struct rq *rq = cpu_rq(cpu);
4536 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4537 unsigned long load_avg = weighted_cpuload(cpu);
4540 return load_avg / nr_running;
4545 static void record_wakee(struct task_struct *p)
4548 * Rough decay (wiping) for cost saving, don't worry
4549 * about the boundary, really active task won't care
4552 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4553 current->wakee_flips >>= 1;
4554 current->wakee_flip_decay_ts = jiffies;
4557 if (current->last_wakee != p) {
4558 current->last_wakee = p;
4559 current->wakee_flips++;
4563 static void task_waking_fair(struct task_struct *p)
4565 struct sched_entity *se = &p->se;
4566 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4569 #ifndef CONFIG_64BIT
4570 u64 min_vruntime_copy;
4573 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4575 min_vruntime = cfs_rq->min_vruntime;
4576 } while (min_vruntime != min_vruntime_copy);
4578 min_vruntime = cfs_rq->min_vruntime;
4581 se->vruntime -= min_vruntime;
4585 #ifdef CONFIG_FAIR_GROUP_SCHED
4587 * effective_load() calculates the load change as seen from the root_task_group
4589 * Adding load to a group doesn't make a group heavier, but can cause movement
4590 * of group shares between cpus. Assuming the shares were perfectly aligned one
4591 * can calculate the shift in shares.
4593 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4594 * on this @cpu and results in a total addition (subtraction) of @wg to the
4595 * total group weight.
4597 * Given a runqueue weight distribution (rw_i) we can compute a shares
4598 * distribution (s_i) using:
4600 * s_i = rw_i / \Sum rw_j (1)
4602 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4603 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4604 * shares distribution (s_i):
4606 * rw_i = { 2, 4, 1, 0 }
4607 * s_i = { 2/7, 4/7, 1/7, 0 }
4609 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4610 * task used to run on and the CPU the waker is running on), we need to
4611 * compute the effect of waking a task on either CPU and, in case of a sync
4612 * wakeup, compute the effect of the current task going to sleep.
4614 * So for a change of @wl to the local @cpu with an overall group weight change
4615 * of @wl we can compute the new shares distribution (s'_i) using:
4617 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4619 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4620 * differences in waking a task to CPU 0. The additional task changes the
4621 * weight and shares distributions like:
4623 * rw'_i = { 3, 4, 1, 0 }
4624 * s'_i = { 3/8, 4/8, 1/8, 0 }
4626 * We can then compute the difference in effective weight by using:
4628 * dw_i = S * (s'_i - s_i) (3)
4630 * Where 'S' is the group weight as seen by its parent.
4632 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4633 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4634 * 4/7) times the weight of the group.
4636 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4638 struct sched_entity *se = tg->se[cpu];
4640 if (!tg->parent) /* the trivial, non-cgroup case */
4643 for_each_sched_entity(se) {
4649 * W = @wg + \Sum rw_j
4651 W = wg + calc_tg_weight(tg, se->my_q);
4656 w = cfs_rq_load_avg(se->my_q) + wl;
4659 * wl = S * s'_i; see (2)
4662 wl = (w * (long)tg->shares) / W;
4667 * Per the above, wl is the new se->load.weight value; since
4668 * those are clipped to [MIN_SHARES, ...) do so now. See
4669 * calc_cfs_shares().
4671 if (wl < MIN_SHARES)
4675 * wl = dw_i = S * (s'_i - s_i); see (3)
4677 wl -= se->avg.load_avg;
4680 * Recursively apply this logic to all parent groups to compute
4681 * the final effective load change on the root group. Since
4682 * only the @tg group gets extra weight, all parent groups can
4683 * only redistribute existing shares. @wl is the shift in shares
4684 * resulting from this level per the above.
4693 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4700 static inline bool energy_aware(void)
4702 return sched_feat(ENERGY_AWARE);
4706 struct sched_group *sg_top;
4707 struct sched_group *sg_cap;
4714 struct task_struct *task;
4729 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4730 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4731 * energy calculations. Using the scale-invariant util returned by
4732 * cpu_util() and approximating scale-invariant util by:
4734 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4736 * the normalized util can be found using the specific capacity.
4738 * capacity = capacity_orig * curr_freq/max_freq
4740 * norm_util = running_time/time ~ util/capacity
4742 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4744 int util = __cpu_util(cpu, delta);
4746 if (util >= capacity)
4747 return SCHED_CAPACITY_SCALE;
4749 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4752 static int calc_util_delta(struct energy_env *eenv, int cpu)
4754 if (cpu == eenv->src_cpu)
4755 return -eenv->util_delta;
4756 if (cpu == eenv->dst_cpu)
4757 return eenv->util_delta;
4762 unsigned long group_max_util(struct energy_env *eenv)
4765 unsigned long max_util = 0;
4767 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4768 delta = calc_util_delta(eenv, i);
4769 max_util = max(max_util, __cpu_util(i, delta));
4776 * group_norm_util() returns the approximated group util relative to it's
4777 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4778 * energy calculations. Since task executions may or may not overlap in time in
4779 * the group the true normalized util is between max(cpu_norm_util(i)) and
4780 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4781 * latter is used as the estimate as it leads to a more pessimistic energy
4782 * estimate (more busy).
4785 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4788 unsigned long util_sum = 0;
4789 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4791 for_each_cpu(i, sched_group_cpus(sg)) {
4792 delta = calc_util_delta(eenv, i);
4793 util_sum += __cpu_norm_util(i, capacity, delta);
4796 if (util_sum > SCHED_CAPACITY_SCALE)
4797 return SCHED_CAPACITY_SCALE;
4801 static int find_new_capacity(struct energy_env *eenv,
4802 const struct sched_group_energy const *sge)
4805 unsigned long util = group_max_util(eenv);
4807 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4808 if (sge->cap_states[idx].cap >= util)
4812 eenv->cap_idx = idx;
4817 static int group_idle_state(struct sched_group *sg)
4819 int i, state = INT_MAX;
4821 /* Find the shallowest idle state in the sched group. */
4822 for_each_cpu(i, sched_group_cpus(sg))
4823 state = min(state, idle_get_state_idx(cpu_rq(i)));
4825 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4832 * sched_group_energy(): Computes the absolute energy consumption of cpus
4833 * belonging to the sched_group including shared resources shared only by
4834 * members of the group. Iterates over all cpus in the hierarchy below the
4835 * sched_group starting from the bottom working it's way up before going to
4836 * the next cpu until all cpus are covered at all levels. The current
4837 * implementation is likely to gather the same util statistics multiple times.
4838 * This can probably be done in a faster but more complex way.
4839 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4841 static int sched_group_energy(struct energy_env *eenv)
4843 struct sched_domain *sd;
4844 int cpu, total_energy = 0;
4845 struct cpumask visit_cpus;
4846 struct sched_group *sg;
4848 WARN_ON(!eenv->sg_top->sge);
4850 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4852 while (!cpumask_empty(&visit_cpus)) {
4853 struct sched_group *sg_shared_cap = NULL;
4855 cpu = cpumask_first(&visit_cpus);
4858 * Is the group utilization affected by cpus outside this
4861 sd = rcu_dereference(per_cpu(sd_scs, cpu));
4865 * We most probably raced with hotplug; returning a
4866 * wrong energy estimation is better than entering an
4872 sg_shared_cap = sd->parent->groups;
4874 for_each_domain(cpu, sd) {
4877 /* Has this sched_domain already been visited? */
4878 if (sd->child && group_first_cpu(sg) != cpu)
4882 unsigned long group_util;
4883 int sg_busy_energy, sg_idle_energy;
4884 int cap_idx, idle_idx;
4886 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
4887 eenv->sg_cap = sg_shared_cap;
4891 cap_idx = find_new_capacity(eenv, sg->sge);
4893 if (sg->group_weight == 1) {
4894 /* Remove capacity of src CPU (before task move) */
4895 if (eenv->util_delta == 0 &&
4896 cpumask_test_cpu(eenv->src_cpu, sched_group_cpus(sg))) {
4897 eenv->cap.before = sg->sge->cap_states[cap_idx].cap;
4898 eenv->cap.delta -= eenv->cap.before;
4900 /* Add capacity of dst CPU (after task move) */
4901 if (eenv->util_delta != 0 &&
4902 cpumask_test_cpu(eenv->dst_cpu, sched_group_cpus(sg))) {
4903 eenv->cap.after = sg->sge->cap_states[cap_idx].cap;
4904 eenv->cap.delta += eenv->cap.after;
4908 idle_idx = group_idle_state(sg);
4909 group_util = group_norm_util(eenv, sg);
4910 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
4911 >> SCHED_CAPACITY_SHIFT;
4912 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
4913 * sg->sge->idle_states[idle_idx].power)
4914 >> SCHED_CAPACITY_SHIFT;
4916 total_energy += sg_busy_energy + sg_idle_energy;
4919 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
4921 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
4924 } while (sg = sg->next, sg != sd->groups);
4930 eenv->energy = total_energy;
4934 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
4936 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
4939 #ifdef CONFIG_SCHED_TUNE
4940 static int energy_diff_evaluate(struct energy_env *eenv)
4945 /* Return energy diff when boost margin is 0 */
4946 #ifdef CONFIG_CGROUP_SCHEDTUNE
4947 boost = schedtune_task_boost(eenv->task);
4949 boost = get_sysctl_sched_cfs_boost();
4952 return eenv->nrg.diff;
4954 /* Compute normalized energy diff */
4955 nrg_delta = schedtune_normalize_energy(eenv->nrg.diff);
4956 eenv->nrg.delta = nrg_delta;
4958 eenv->payoff = schedtune_accept_deltas(
4964 * When SchedTune is enabled, the energy_diff() function will return
4965 * the computed energy payoff value. Since the energy_diff() return
4966 * value is expected to be negative by its callers, this evaluation
4967 * function return a negative value each time the evaluation return a
4968 * positive payoff, which is the condition for the acceptance of
4969 * a scheduling decision
4971 return -eenv->payoff;
4973 #else /* CONFIG_SCHED_TUNE */
4974 #define energy_diff_evaluate(eenv) eenv->nrg.diff
4978 * energy_diff(): Estimate the energy impact of changing the utilization
4979 * distribution. eenv specifies the change: utilisation amount, source, and
4980 * destination cpu. Source or destination cpu may be -1 in which case the
4981 * utilization is removed from or added to the system (e.g. task wake-up). If
4982 * both are specified, the utilization is migrated.
4984 static int energy_diff(struct energy_env *eenv)
4986 struct sched_domain *sd;
4987 struct sched_group *sg;
4988 int sd_cpu = -1, energy_before = 0, energy_after = 0;
4990 struct energy_env eenv_before = {
4992 .src_cpu = eenv->src_cpu,
4993 .dst_cpu = eenv->dst_cpu,
4994 .nrg = { 0, 0, 0, 0},
4998 if (eenv->src_cpu == eenv->dst_cpu)
5001 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
5002 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
5005 return 0; /* Error */
5010 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
5011 eenv_before.sg_top = eenv->sg_top = sg;
5013 if (sched_group_energy(&eenv_before))
5014 return 0; /* Invalid result abort */
5015 energy_before += eenv_before.energy;
5017 /* Keep track of SRC cpu (before) capacity */
5018 eenv->cap.before = eenv_before.cap.before;
5019 eenv->cap.delta = eenv_before.cap.delta;
5021 if (sched_group_energy(eenv))
5022 return 0; /* Invalid result abort */
5023 energy_after += eenv->energy;
5025 } while (sg = sg->next, sg != sd->groups);
5027 eenv->nrg.before = energy_before;
5028 eenv->nrg.after = energy_after;
5029 eenv->nrg.diff = eenv->nrg.after - eenv->nrg.before;
5032 return energy_diff_evaluate(eenv);
5036 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5037 * A waker of many should wake a different task than the one last awakened
5038 * at a frequency roughly N times higher than one of its wakees. In order
5039 * to determine whether we should let the load spread vs consolodating to
5040 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
5041 * partner, and a factor of lls_size higher frequency in the other. With
5042 * both conditions met, we can be relatively sure that the relationship is
5043 * non-monogamous, with partner count exceeding socket size. Waker/wakee
5044 * being client/server, worker/dispatcher, interrupt source or whatever is
5045 * irrelevant, spread criteria is apparent partner count exceeds socket size.
5047 static int wake_wide(struct task_struct *p)
5049 unsigned int master = current->wakee_flips;
5050 unsigned int slave = p->wakee_flips;
5051 int factor = this_cpu_read(sd_llc_size);
5054 swap(master, slave);
5055 if (slave < factor || master < slave * factor)
5060 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5062 s64 this_load, load;
5063 s64 this_eff_load, prev_eff_load;
5064 int idx, this_cpu, prev_cpu;
5065 struct task_group *tg;
5066 unsigned long weight;
5070 this_cpu = smp_processor_id();
5071 prev_cpu = task_cpu(p);
5072 load = source_load(prev_cpu, idx);
5073 this_load = target_load(this_cpu, idx);
5076 * If sync wakeup then subtract the (maximum possible)
5077 * effect of the currently running task from the load
5078 * of the current CPU:
5081 tg = task_group(current);
5082 weight = current->se.avg.load_avg;
5084 this_load += effective_load(tg, this_cpu, -weight, -weight);
5085 load += effective_load(tg, prev_cpu, 0, -weight);
5089 weight = p->se.avg.load_avg;
5092 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5093 * due to the sync cause above having dropped this_load to 0, we'll
5094 * always have an imbalance, but there's really nothing you can do
5095 * about that, so that's good too.
5097 * Otherwise check if either cpus are near enough in load to allow this
5098 * task to be woken on this_cpu.
5100 this_eff_load = 100;
5101 this_eff_load *= capacity_of(prev_cpu);
5103 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5104 prev_eff_load *= capacity_of(this_cpu);
5106 if (this_load > 0) {
5107 this_eff_load *= this_load +
5108 effective_load(tg, this_cpu, weight, weight);
5110 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5113 balanced = this_eff_load <= prev_eff_load;
5115 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5120 schedstat_inc(sd, ttwu_move_affine);
5121 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5126 static inline unsigned long task_util(struct task_struct *p)
5128 return p->se.avg.util_avg;
5131 unsigned int capacity_margin = 1280; /* ~20% margin */
5133 static inline unsigned long boosted_task_util(struct task_struct *task);
5135 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5137 unsigned long capacity = capacity_of(cpu);
5139 util += boosted_task_util(p);
5141 return (capacity * 1024) > (util * capacity_margin);
5144 static inline bool task_fits_max(struct task_struct *p, int cpu)
5146 unsigned long capacity = capacity_of(cpu);
5147 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity.val;
5149 if (capacity == max_capacity)
5152 if (capacity * capacity_margin > max_capacity * 1024)
5155 return __task_fits(p, cpu, 0);
5158 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5160 return __task_fits(p, cpu, cpu_util(cpu));
5163 static bool cpu_overutilized(int cpu)
5165 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5168 #ifdef CONFIG_SCHED_TUNE
5170 static unsigned long
5171 schedtune_margin(unsigned long signal, unsigned long boost)
5173 unsigned long long margin = 0;
5176 * Signal proportional compensation (SPC)
5178 * The Boost (B) value is used to compute a Margin (M) which is
5179 * proportional to the complement of the original Signal (S):
5180 * M = B * (SCHED_LOAD_SCALE - S)
5181 * The obtained M could be used by the caller to "boost" S.
5183 margin = SCHED_LOAD_SCALE - signal;
5187 * Fast integer division by constant:
5188 * Constant : (C) = 100
5189 * Precision : 0.1% (P) = 0.1
5190 * Reference : C * 100 / P (R) = 100000
5193 * Shift bits : ceil(log(R,2)) (S) = 17
5194 * Mult const : round(2^S/C) (M) = 1311
5204 static inline unsigned int
5205 schedtune_cpu_margin(unsigned long util, int cpu)
5209 #ifdef CONFIG_CGROUP_SCHEDTUNE
5210 boost = schedtune_cpu_boost(cpu);
5212 boost = get_sysctl_sched_cfs_boost();
5217 return schedtune_margin(util, boost);
5220 static inline unsigned long
5221 schedtune_task_margin(struct task_struct *task)
5225 unsigned long margin;
5227 #ifdef CONFIG_CGROUP_SCHEDTUNE
5228 boost = schedtune_task_boost(task);
5230 boost = get_sysctl_sched_cfs_boost();
5235 util = task_util(task);
5236 margin = schedtune_margin(util, boost);
5241 #else /* CONFIG_SCHED_TUNE */
5243 static inline unsigned int
5244 schedtune_cpu_margin(unsigned long util, int cpu)
5249 static inline unsigned int
5250 schedtune_task_margin(struct task_struct *task)
5255 #endif /* CONFIG_SCHED_TUNE */
5257 static inline unsigned long
5258 boosted_cpu_util(int cpu)
5260 unsigned long util = cpu_util(cpu);
5261 unsigned long margin = schedtune_cpu_margin(util, cpu);
5263 return util + margin;
5266 static inline unsigned long
5267 boosted_task_util(struct task_struct *task)
5269 unsigned long util = task_util(task);
5270 unsigned long margin = schedtune_task_margin(task);
5272 return util + margin;
5276 * find_idlest_group finds and returns the least busy CPU group within the
5279 static struct sched_group *
5280 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5281 int this_cpu, int sd_flag)
5283 struct sched_group *idlest = NULL, *group = sd->groups;
5284 struct sched_group *fit_group = NULL, *spare_group = NULL;
5285 unsigned long min_load = ULONG_MAX, this_load = 0;
5286 unsigned long fit_capacity = ULONG_MAX;
5287 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5288 int load_idx = sd->forkexec_idx;
5289 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5291 if (sd_flag & SD_BALANCE_WAKE)
5292 load_idx = sd->wake_idx;
5295 unsigned long load, avg_load, spare_capacity;
5299 /* Skip over this group if it has no CPUs allowed */
5300 if (!cpumask_intersects(sched_group_cpus(group),
5301 tsk_cpus_allowed(p)))
5304 local_group = cpumask_test_cpu(this_cpu,
5305 sched_group_cpus(group));
5307 /* Tally up the load of all CPUs in the group */
5310 for_each_cpu(i, sched_group_cpus(group)) {
5311 /* Bias balancing toward cpus of our domain */
5313 load = source_load(i, load_idx);
5315 load = target_load(i, load_idx);
5320 * Look for most energy-efficient group that can fit
5321 * that can fit the task.
5323 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5324 fit_capacity = capacity_of(i);
5329 * Look for group which has most spare capacity on a
5332 spare_capacity = capacity_of(i) - cpu_util(i);
5333 if (spare_capacity > max_spare_capacity) {
5334 max_spare_capacity = spare_capacity;
5335 spare_group = group;
5339 /* Adjust by relative CPU capacity of the group */
5340 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5343 this_load = avg_load;
5344 } else if (avg_load < min_load) {
5345 min_load = avg_load;
5348 } while (group = group->next, group != sd->groups);
5356 if (!idlest || 100*this_load < imbalance*min_load)
5362 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5365 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5367 unsigned long load, min_load = ULONG_MAX;
5368 unsigned int min_exit_latency = UINT_MAX;
5369 u64 latest_idle_timestamp = 0;
5370 int least_loaded_cpu = this_cpu;
5371 int shallowest_idle_cpu = -1;
5374 /* Traverse only the allowed CPUs */
5375 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5376 if (task_fits_spare(p, i)) {
5377 struct rq *rq = cpu_rq(i);
5378 struct cpuidle_state *idle = idle_get_state(rq);
5379 if (idle && idle->exit_latency < min_exit_latency) {
5381 * We give priority to a CPU whose idle state
5382 * has the smallest exit latency irrespective
5383 * of any idle timestamp.
5385 min_exit_latency = idle->exit_latency;
5386 latest_idle_timestamp = rq->idle_stamp;
5387 shallowest_idle_cpu = i;
5388 } else if (idle_cpu(i) &&
5389 (!idle || idle->exit_latency == min_exit_latency) &&
5390 rq->idle_stamp > latest_idle_timestamp) {
5392 * If equal or no active idle state, then
5393 * the most recently idled CPU might have
5396 latest_idle_timestamp = rq->idle_stamp;
5397 shallowest_idle_cpu = i;
5398 } else if (shallowest_idle_cpu == -1) {
5400 * If we haven't found an idle CPU yet
5401 * pick a non-idle one that can fit the task as
5404 shallowest_idle_cpu = i;
5406 } else if (shallowest_idle_cpu == -1) {
5407 load = weighted_cpuload(i);
5408 if (load < min_load || (load == min_load && i == this_cpu)) {
5410 least_loaded_cpu = i;
5415 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5419 * Try and locate an idle CPU in the sched_domain.
5421 static int select_idle_sibling(struct task_struct *p, int target)
5423 struct sched_domain *sd;
5424 struct sched_group *sg;
5425 int i = task_cpu(p);
5427 if (idle_cpu(target))
5431 * If the prevous cpu is cache affine and idle, don't be stupid.
5433 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5437 * Otherwise, iterate the domains and find an elegible idle cpu.
5439 sd = rcu_dereference(per_cpu(sd_llc, target));
5440 for_each_lower_domain(sd) {
5443 if (!cpumask_intersects(sched_group_cpus(sg),
5444 tsk_cpus_allowed(p)))
5447 for_each_cpu(i, sched_group_cpus(sg)) {
5448 if (i == target || !idle_cpu(i))
5452 target = cpumask_first_and(sched_group_cpus(sg),
5453 tsk_cpus_allowed(p));
5457 } while (sg != sd->groups);
5463 static int energy_aware_wake_cpu(struct task_struct *p, int target)
5465 struct sched_domain *sd;
5466 struct sched_group *sg, *sg_target;
5467 int target_max_cap = INT_MAX;
5468 int target_cpu = task_cpu(p);
5471 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5480 * Find group with sufficient capacity. We only get here if no cpu is
5481 * overutilized. We may end up overutilizing a cpu by adding the task,
5482 * but that should not be any worse than select_idle_sibling().
5483 * load_balance() should sort it out later as we get above the tipping
5487 /* Assuming all cpus are the same in group */
5488 int max_cap_cpu = group_first_cpu(sg);
5491 * Assume smaller max capacity means more energy-efficient.
5492 * Ideally we should query the energy model for the right
5493 * answer but it easily ends up in an exhaustive search.
5495 if (capacity_of(max_cap_cpu) < target_max_cap &&
5496 task_fits_max(p, max_cap_cpu)) {
5498 target_max_cap = capacity_of(max_cap_cpu);
5500 } while (sg = sg->next, sg != sd->groups);
5502 /* Find cpu with sufficient capacity */
5503 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5505 * p's blocked utilization is still accounted for on prev_cpu
5506 * so prev_cpu will receive a negative bias due to the double
5507 * accounting. However, the blocked utilization may be zero.
5509 int new_util = cpu_util(i) + boosted_task_util(p);
5511 if (new_util > capacity_orig_of(i))
5514 if (new_util < capacity_curr_of(i)) {
5516 if (cpu_rq(i)->nr_running)
5520 /* cpu has capacity at higher OPP, keep it as fallback */
5521 if (target_cpu == task_cpu(p))
5525 if (target_cpu != task_cpu(p)) {
5526 struct energy_env eenv = {
5527 .util_delta = task_util(p),
5528 .src_cpu = task_cpu(p),
5529 .dst_cpu = target_cpu,
5533 /* Not enough spare capacity on previous cpu */
5534 if (cpu_overutilized(task_cpu(p)))
5537 if (energy_diff(&eenv) >= 0)
5545 * select_task_rq_fair: Select target runqueue for the waking task in domains
5546 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5547 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5549 * Balances load by selecting the idlest cpu in the idlest group, or under
5550 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5552 * Returns the target cpu number.
5554 * preempt must be disabled.
5557 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5559 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5560 int cpu = smp_processor_id();
5561 int new_cpu = prev_cpu;
5562 int want_affine = 0;
5563 int sync = wake_flags & WF_SYNC;
5565 if (sd_flag & SD_BALANCE_WAKE)
5566 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5567 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5571 for_each_domain(cpu, tmp) {
5572 if (!(tmp->flags & SD_LOAD_BALANCE))
5576 * If both cpu and prev_cpu are part of this domain,
5577 * cpu is a valid SD_WAKE_AFFINE target.
5579 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5580 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5585 if (tmp->flags & sd_flag)
5587 else if (!want_affine)
5592 sd = NULL; /* Prefer wake_affine over balance flags */
5593 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5598 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5599 new_cpu = energy_aware_wake_cpu(p, prev_cpu);
5600 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5601 new_cpu = select_idle_sibling(p, new_cpu);
5604 struct sched_group *group;
5607 if (!(sd->flags & sd_flag)) {
5612 group = find_idlest_group(sd, p, cpu, sd_flag);
5618 new_cpu = find_idlest_cpu(group, p, cpu);
5619 if (new_cpu == -1 || new_cpu == cpu) {
5620 /* Now try balancing at a lower domain level of cpu */
5625 /* Now try balancing at a lower domain level of new_cpu */
5627 weight = sd->span_weight;
5629 for_each_domain(cpu, tmp) {
5630 if (weight <= tmp->span_weight)
5632 if (tmp->flags & sd_flag)
5635 /* while loop will break here if sd == NULL */
5643 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5644 * cfs_rq_of(p) references at time of call are still valid and identify the
5645 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5646 * other assumptions, including the state of rq->lock, should be made.
5648 static void migrate_task_rq_fair(struct task_struct *p)
5651 * We are supposed to update the task to "current" time, then its up to date
5652 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5653 * what current time is, so simply throw away the out-of-date time. This
5654 * will result in the wakee task is less decayed, but giving the wakee more
5655 * load sounds not bad.
5657 remove_entity_load_avg(&p->se);
5659 /* Tell new CPU we are migrated */
5660 p->se.avg.last_update_time = 0;
5662 /* We have migrated, no longer consider this task hot */
5663 p->se.exec_start = 0;
5666 static void task_dead_fair(struct task_struct *p)
5668 remove_entity_load_avg(&p->se);
5670 #endif /* CONFIG_SMP */
5672 static unsigned long
5673 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5675 unsigned long gran = sysctl_sched_wakeup_granularity;
5678 * Since its curr running now, convert the gran from real-time
5679 * to virtual-time in his units.
5681 * By using 'se' instead of 'curr' we penalize light tasks, so
5682 * they get preempted easier. That is, if 'se' < 'curr' then
5683 * the resulting gran will be larger, therefore penalizing the
5684 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5685 * be smaller, again penalizing the lighter task.
5687 * This is especially important for buddies when the leftmost
5688 * task is higher priority than the buddy.
5690 return calc_delta_fair(gran, se);
5694 * Should 'se' preempt 'curr'.
5708 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5710 s64 gran, vdiff = curr->vruntime - se->vruntime;
5715 gran = wakeup_gran(curr, se);
5722 static void set_last_buddy(struct sched_entity *se)
5724 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5727 for_each_sched_entity(se)
5728 cfs_rq_of(se)->last = se;
5731 static void set_next_buddy(struct sched_entity *se)
5733 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5736 for_each_sched_entity(se)
5737 cfs_rq_of(se)->next = se;
5740 static void set_skip_buddy(struct sched_entity *se)
5742 for_each_sched_entity(se)
5743 cfs_rq_of(se)->skip = se;
5747 * Preempt the current task with a newly woken task if needed:
5749 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5751 struct task_struct *curr = rq->curr;
5752 struct sched_entity *se = &curr->se, *pse = &p->se;
5753 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5754 int scale = cfs_rq->nr_running >= sched_nr_latency;
5755 int next_buddy_marked = 0;
5757 if (unlikely(se == pse))
5761 * This is possible from callers such as attach_tasks(), in which we
5762 * unconditionally check_prempt_curr() after an enqueue (which may have
5763 * lead to a throttle). This both saves work and prevents false
5764 * next-buddy nomination below.
5766 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5769 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5770 set_next_buddy(pse);
5771 next_buddy_marked = 1;
5775 * We can come here with TIF_NEED_RESCHED already set from new task
5778 * Note: this also catches the edge-case of curr being in a throttled
5779 * group (e.g. via set_curr_task), since update_curr() (in the
5780 * enqueue of curr) will have resulted in resched being set. This
5781 * prevents us from potentially nominating it as a false LAST_BUDDY
5784 if (test_tsk_need_resched(curr))
5787 /* Idle tasks are by definition preempted by non-idle tasks. */
5788 if (unlikely(curr->policy == SCHED_IDLE) &&
5789 likely(p->policy != SCHED_IDLE))
5793 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5794 * is driven by the tick):
5796 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5799 find_matching_se(&se, &pse);
5800 update_curr(cfs_rq_of(se));
5802 if (wakeup_preempt_entity(se, pse) == 1) {
5804 * Bias pick_next to pick the sched entity that is
5805 * triggering this preemption.
5807 if (!next_buddy_marked)
5808 set_next_buddy(pse);
5817 * Only set the backward buddy when the current task is still
5818 * on the rq. This can happen when a wakeup gets interleaved
5819 * with schedule on the ->pre_schedule() or idle_balance()
5820 * point, either of which can * drop the rq lock.
5822 * Also, during early boot the idle thread is in the fair class,
5823 * for obvious reasons its a bad idea to schedule back to it.
5825 if (unlikely(!se->on_rq || curr == rq->idle))
5828 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5832 static struct task_struct *
5833 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5835 struct cfs_rq *cfs_rq = &rq->cfs;
5836 struct sched_entity *se;
5837 struct task_struct *p;
5841 #ifdef CONFIG_FAIR_GROUP_SCHED
5842 if (!cfs_rq->nr_running)
5845 if (prev->sched_class != &fair_sched_class)
5849 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5850 * likely that a next task is from the same cgroup as the current.
5852 * Therefore attempt to avoid putting and setting the entire cgroup
5853 * hierarchy, only change the part that actually changes.
5857 struct sched_entity *curr = cfs_rq->curr;
5860 * Since we got here without doing put_prev_entity() we also
5861 * have to consider cfs_rq->curr. If it is still a runnable
5862 * entity, update_curr() will update its vruntime, otherwise
5863 * forget we've ever seen it.
5867 update_curr(cfs_rq);
5872 * This call to check_cfs_rq_runtime() will do the
5873 * throttle and dequeue its entity in the parent(s).
5874 * Therefore the 'simple' nr_running test will indeed
5877 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5881 se = pick_next_entity(cfs_rq, curr);
5882 cfs_rq = group_cfs_rq(se);
5888 * Since we haven't yet done put_prev_entity and if the selected task
5889 * is a different task than we started out with, try and touch the
5890 * least amount of cfs_rqs.
5893 struct sched_entity *pse = &prev->se;
5895 while (!(cfs_rq = is_same_group(se, pse))) {
5896 int se_depth = se->depth;
5897 int pse_depth = pse->depth;
5899 if (se_depth <= pse_depth) {
5900 put_prev_entity(cfs_rq_of(pse), pse);
5901 pse = parent_entity(pse);
5903 if (se_depth >= pse_depth) {
5904 set_next_entity(cfs_rq_of(se), se);
5905 se = parent_entity(se);
5909 put_prev_entity(cfs_rq, pse);
5910 set_next_entity(cfs_rq, se);
5913 if (hrtick_enabled(rq))
5914 hrtick_start_fair(rq, p);
5916 rq->misfit_task = !task_fits_max(p, rq->cpu);
5923 if (!cfs_rq->nr_running)
5926 put_prev_task(rq, prev);
5929 se = pick_next_entity(cfs_rq, NULL);
5930 set_next_entity(cfs_rq, se);
5931 cfs_rq = group_cfs_rq(se);
5936 if (hrtick_enabled(rq))
5937 hrtick_start_fair(rq, p);
5939 rq->misfit_task = !task_fits_max(p, rq->cpu);
5944 rq->misfit_task = 0;
5946 * This is OK, because current is on_cpu, which avoids it being picked
5947 * for load-balance and preemption/IRQs are still disabled avoiding
5948 * further scheduler activity on it and we're being very careful to
5949 * re-start the picking loop.
5951 lockdep_unpin_lock(&rq->lock);
5952 new_tasks = idle_balance(rq);
5953 lockdep_pin_lock(&rq->lock);
5955 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5956 * possible for any higher priority task to appear. In that case we
5957 * must re-start the pick_next_entity() loop.
5969 * Account for a descheduled task:
5971 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5973 struct sched_entity *se = &prev->se;
5974 struct cfs_rq *cfs_rq;
5976 for_each_sched_entity(se) {
5977 cfs_rq = cfs_rq_of(se);
5978 put_prev_entity(cfs_rq, se);
5983 * sched_yield() is very simple
5985 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5987 static void yield_task_fair(struct rq *rq)
5989 struct task_struct *curr = rq->curr;
5990 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5991 struct sched_entity *se = &curr->se;
5994 * Are we the only task in the tree?
5996 if (unlikely(rq->nr_running == 1))
5999 clear_buddies(cfs_rq, se);
6001 if (curr->policy != SCHED_BATCH) {
6002 update_rq_clock(rq);
6004 * Update run-time statistics of the 'current'.
6006 update_curr(cfs_rq);
6008 * Tell update_rq_clock() that we've just updated,
6009 * so we don't do microscopic update in schedule()
6010 * and double the fastpath cost.
6012 rq_clock_skip_update(rq, true);
6018 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
6020 struct sched_entity *se = &p->se;
6022 /* throttled hierarchies are not runnable */
6023 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6026 /* Tell the scheduler that we'd really like pse to run next. */
6029 yield_task_fair(rq);
6035 /**************************************************
6036 * Fair scheduling class load-balancing methods.
6040 * The purpose of load-balancing is to achieve the same basic fairness the
6041 * per-cpu scheduler provides, namely provide a proportional amount of compute
6042 * time to each task. This is expressed in the following equation:
6044 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
6046 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
6047 * W_i,0 is defined as:
6049 * W_i,0 = \Sum_j w_i,j (2)
6051 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6052 * is derived from the nice value as per prio_to_weight[].
6054 * The weight average is an exponential decay average of the instantaneous
6057 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
6059 * C_i is the compute capacity of cpu i, typically it is the
6060 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
6061 * can also include other factors [XXX].
6063 * To achieve this balance we define a measure of imbalance which follows
6064 * directly from (1):
6066 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
6068 * We them move tasks around to minimize the imbalance. In the continuous
6069 * function space it is obvious this converges, in the discrete case we get
6070 * a few fun cases generally called infeasible weight scenarios.
6073 * - infeasible weights;
6074 * - local vs global optima in the discrete case. ]
6079 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6080 * for all i,j solution, we create a tree of cpus that follows the hardware
6081 * topology where each level pairs two lower groups (or better). This results
6082 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
6083 * tree to only the first of the previous level and we decrease the frequency
6084 * of load-balance at each level inv. proportional to the number of cpus in
6090 * \Sum { --- * --- * 2^i } = O(n) (5)
6092 * `- size of each group
6093 * | | `- number of cpus doing load-balance
6095 * `- sum over all levels
6097 * Coupled with a limit on how many tasks we can migrate every balance pass,
6098 * this makes (5) the runtime complexity of the balancer.
6100 * An important property here is that each CPU is still (indirectly) connected
6101 * to every other cpu in at most O(log n) steps:
6103 * The adjacency matrix of the resulting graph is given by:
6106 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
6109 * And you'll find that:
6111 * A^(log_2 n)_i,j != 0 for all i,j (7)
6113 * Showing there's indeed a path between every cpu in at most O(log n) steps.
6114 * The task movement gives a factor of O(m), giving a convergence complexity
6117 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
6122 * In order to avoid CPUs going idle while there's still work to do, new idle
6123 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6124 * tree itself instead of relying on other CPUs to bring it work.
6126 * This adds some complexity to both (5) and (8) but it reduces the total idle
6134 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6137 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6142 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6144 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6146 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6149 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6150 * rewrite all of this once again.]
6153 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6155 enum fbq_type { regular, remote, all };
6164 #define LBF_ALL_PINNED 0x01
6165 #define LBF_NEED_BREAK 0x02
6166 #define LBF_DST_PINNED 0x04
6167 #define LBF_SOME_PINNED 0x08
6170 struct sched_domain *sd;
6178 struct cpumask *dst_grpmask;
6180 enum cpu_idle_type idle;
6182 unsigned int src_grp_nr_running;
6183 /* The set of CPUs under consideration for load-balancing */
6184 struct cpumask *cpus;
6189 unsigned int loop_break;
6190 unsigned int loop_max;
6192 enum fbq_type fbq_type;
6193 enum group_type busiest_group_type;
6194 struct list_head tasks;
6198 * Is this task likely cache-hot:
6200 static int task_hot(struct task_struct *p, struct lb_env *env)
6204 lockdep_assert_held(&env->src_rq->lock);
6206 if (p->sched_class != &fair_sched_class)
6209 if (unlikely(p->policy == SCHED_IDLE))
6213 * Buddy candidates are cache hot:
6215 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6216 (&p->se == cfs_rq_of(&p->se)->next ||
6217 &p->se == cfs_rq_of(&p->se)->last))
6220 if (sysctl_sched_migration_cost == -1)
6222 if (sysctl_sched_migration_cost == 0)
6225 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6227 return delta < (s64)sysctl_sched_migration_cost;
6230 #ifdef CONFIG_NUMA_BALANCING
6232 * Returns 1, if task migration degrades locality
6233 * Returns 0, if task migration improves locality i.e migration preferred.
6234 * Returns -1, if task migration is not affected by locality.
6236 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6238 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6239 unsigned long src_faults, dst_faults;
6240 int src_nid, dst_nid;
6242 if (!static_branch_likely(&sched_numa_balancing))
6245 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6248 src_nid = cpu_to_node(env->src_cpu);
6249 dst_nid = cpu_to_node(env->dst_cpu);
6251 if (src_nid == dst_nid)
6254 /* Migrating away from the preferred node is always bad. */
6255 if (src_nid == p->numa_preferred_nid) {
6256 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6262 /* Encourage migration to the preferred node. */
6263 if (dst_nid == p->numa_preferred_nid)
6267 src_faults = group_faults(p, src_nid);
6268 dst_faults = group_faults(p, dst_nid);
6270 src_faults = task_faults(p, src_nid);
6271 dst_faults = task_faults(p, dst_nid);
6274 return dst_faults < src_faults;
6278 static inline int migrate_degrades_locality(struct task_struct *p,
6286 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6289 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6293 lockdep_assert_held(&env->src_rq->lock);
6296 * We do not migrate tasks that are:
6297 * 1) throttled_lb_pair, or
6298 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6299 * 3) running (obviously), or
6300 * 4) are cache-hot on their current CPU.
6302 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6305 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6308 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6310 env->flags |= LBF_SOME_PINNED;
6313 * Remember if this task can be migrated to any other cpu in
6314 * our sched_group. We may want to revisit it if we couldn't
6315 * meet load balance goals by pulling other tasks on src_cpu.
6317 * Also avoid computing new_dst_cpu if we have already computed
6318 * one in current iteration.
6320 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6323 /* Prevent to re-select dst_cpu via env's cpus */
6324 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6325 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6326 env->flags |= LBF_DST_PINNED;
6327 env->new_dst_cpu = cpu;
6335 /* Record that we found atleast one task that could run on dst_cpu */
6336 env->flags &= ~LBF_ALL_PINNED;
6338 if (task_running(env->src_rq, p)) {
6339 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6344 * Aggressive migration if:
6345 * 1) destination numa is preferred
6346 * 2) task is cache cold, or
6347 * 3) too many balance attempts have failed.
6349 tsk_cache_hot = migrate_degrades_locality(p, env);
6350 if (tsk_cache_hot == -1)
6351 tsk_cache_hot = task_hot(p, env);
6353 if (tsk_cache_hot <= 0 ||
6354 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6355 if (tsk_cache_hot == 1) {
6356 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6357 schedstat_inc(p, se.statistics.nr_forced_migrations);
6362 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6367 * detach_task() -- detach the task for the migration specified in env
6369 static void detach_task(struct task_struct *p, struct lb_env *env)
6371 lockdep_assert_held(&env->src_rq->lock);
6373 deactivate_task(env->src_rq, p, 0);
6374 p->on_rq = TASK_ON_RQ_MIGRATING;
6375 set_task_cpu(p, env->dst_cpu);
6379 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6380 * part of active balancing operations within "domain".
6382 * Returns a task if successful and NULL otherwise.
6384 static struct task_struct *detach_one_task(struct lb_env *env)
6386 struct task_struct *p, *n;
6388 lockdep_assert_held(&env->src_rq->lock);
6390 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6391 if (!can_migrate_task(p, env))
6394 detach_task(p, env);
6397 * Right now, this is only the second place where
6398 * lb_gained[env->idle] is updated (other is detach_tasks)
6399 * so we can safely collect stats here rather than
6400 * inside detach_tasks().
6402 schedstat_inc(env->sd, lb_gained[env->idle]);
6408 static const unsigned int sched_nr_migrate_break = 32;
6411 * detach_tasks() -- tries to detach up to imbalance weighted load from
6412 * busiest_rq, as part of a balancing operation within domain "sd".
6414 * Returns number of detached tasks if successful and 0 otherwise.
6416 static int detach_tasks(struct lb_env *env)
6418 struct list_head *tasks = &env->src_rq->cfs_tasks;
6419 struct task_struct *p;
6423 lockdep_assert_held(&env->src_rq->lock);
6425 if (env->imbalance <= 0)
6428 while (!list_empty(tasks)) {
6430 * We don't want to steal all, otherwise we may be treated likewise,
6431 * which could at worst lead to a livelock crash.
6433 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6436 p = list_first_entry(tasks, struct task_struct, se.group_node);
6439 /* We've more or less seen every task there is, call it quits */
6440 if (env->loop > env->loop_max)
6443 /* take a breather every nr_migrate tasks */
6444 if (env->loop > env->loop_break) {
6445 env->loop_break += sched_nr_migrate_break;
6446 env->flags |= LBF_NEED_BREAK;
6450 if (!can_migrate_task(p, env))
6453 load = task_h_load(p);
6455 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6458 if ((load / 2) > env->imbalance)
6461 detach_task(p, env);
6462 list_add(&p->se.group_node, &env->tasks);
6465 env->imbalance -= load;
6467 #ifdef CONFIG_PREEMPT
6469 * NEWIDLE balancing is a source of latency, so preemptible
6470 * kernels will stop after the first task is detached to minimize
6471 * the critical section.
6473 if (env->idle == CPU_NEWLY_IDLE)
6478 * We only want to steal up to the prescribed amount of
6481 if (env->imbalance <= 0)
6486 list_move_tail(&p->se.group_node, tasks);
6490 * Right now, this is one of only two places we collect this stat
6491 * so we can safely collect detach_one_task() stats here rather
6492 * than inside detach_one_task().
6494 schedstat_add(env->sd, lb_gained[env->idle], detached);
6500 * attach_task() -- attach the task detached by detach_task() to its new rq.
6502 static void attach_task(struct rq *rq, struct task_struct *p)
6504 lockdep_assert_held(&rq->lock);
6506 BUG_ON(task_rq(p) != rq);
6507 p->on_rq = TASK_ON_RQ_QUEUED;
6508 activate_task(rq, p, 0);
6509 check_preempt_curr(rq, p, 0);
6513 * attach_one_task() -- attaches the task returned from detach_one_task() to
6516 static void attach_one_task(struct rq *rq, struct task_struct *p)
6518 raw_spin_lock(&rq->lock);
6521 * We want to potentially raise target_cpu's OPP.
6523 update_capacity_of(cpu_of(rq));
6524 raw_spin_unlock(&rq->lock);
6528 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6531 static void attach_tasks(struct lb_env *env)
6533 struct list_head *tasks = &env->tasks;
6534 struct task_struct *p;
6536 raw_spin_lock(&env->dst_rq->lock);
6538 while (!list_empty(tasks)) {
6539 p = list_first_entry(tasks, struct task_struct, se.group_node);
6540 list_del_init(&p->se.group_node);
6542 attach_task(env->dst_rq, p);
6546 * We want to potentially raise env.dst_cpu's OPP.
6548 update_capacity_of(env->dst_cpu);
6550 raw_spin_unlock(&env->dst_rq->lock);
6553 #ifdef CONFIG_FAIR_GROUP_SCHED
6554 static void update_blocked_averages(int cpu)
6556 struct rq *rq = cpu_rq(cpu);
6557 struct cfs_rq *cfs_rq;
6558 unsigned long flags;
6560 raw_spin_lock_irqsave(&rq->lock, flags);
6561 update_rq_clock(rq);
6564 * Iterates the task_group tree in a bottom up fashion, see
6565 * list_add_leaf_cfs_rq() for details.
6567 for_each_leaf_cfs_rq(rq, cfs_rq) {
6568 /* throttled entities do not contribute to load */
6569 if (throttled_hierarchy(cfs_rq))
6572 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6573 update_tg_load_avg(cfs_rq, 0);
6575 raw_spin_unlock_irqrestore(&rq->lock, flags);
6579 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6580 * This needs to be done in a top-down fashion because the load of a child
6581 * group is a fraction of its parents load.
6583 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6585 struct rq *rq = rq_of(cfs_rq);
6586 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6587 unsigned long now = jiffies;
6590 if (cfs_rq->last_h_load_update == now)
6593 cfs_rq->h_load_next = NULL;
6594 for_each_sched_entity(se) {
6595 cfs_rq = cfs_rq_of(se);
6596 cfs_rq->h_load_next = se;
6597 if (cfs_rq->last_h_load_update == now)
6602 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6603 cfs_rq->last_h_load_update = now;
6606 while ((se = cfs_rq->h_load_next) != NULL) {
6607 load = cfs_rq->h_load;
6608 load = div64_ul(load * se->avg.load_avg,
6609 cfs_rq_load_avg(cfs_rq) + 1);
6610 cfs_rq = group_cfs_rq(se);
6611 cfs_rq->h_load = load;
6612 cfs_rq->last_h_load_update = now;
6616 static unsigned long task_h_load(struct task_struct *p)
6618 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6620 update_cfs_rq_h_load(cfs_rq);
6621 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6622 cfs_rq_load_avg(cfs_rq) + 1);
6625 static inline void update_blocked_averages(int cpu)
6627 struct rq *rq = cpu_rq(cpu);
6628 struct cfs_rq *cfs_rq = &rq->cfs;
6629 unsigned long flags;
6631 raw_spin_lock_irqsave(&rq->lock, flags);
6632 update_rq_clock(rq);
6633 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6634 raw_spin_unlock_irqrestore(&rq->lock, flags);
6637 static unsigned long task_h_load(struct task_struct *p)
6639 return p->se.avg.load_avg;
6643 /********** Helpers for find_busiest_group ************************/
6646 * sg_lb_stats - stats of a sched_group required for load_balancing
6648 struct sg_lb_stats {
6649 unsigned long avg_load; /*Avg load across the CPUs of the group */
6650 unsigned long group_load; /* Total load over the CPUs of the group */
6651 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6652 unsigned long load_per_task;
6653 unsigned long group_capacity;
6654 unsigned long group_util; /* Total utilization of the group */
6655 unsigned int sum_nr_running; /* Nr tasks running in the group */
6656 unsigned int idle_cpus;
6657 unsigned int group_weight;
6658 enum group_type group_type;
6659 int group_no_capacity;
6660 int group_misfit_task; /* A cpu has a task too big for its capacity */
6661 #ifdef CONFIG_NUMA_BALANCING
6662 unsigned int nr_numa_running;
6663 unsigned int nr_preferred_running;
6668 * sd_lb_stats - Structure to store the statistics of a sched_domain
6669 * during load balancing.
6671 struct sd_lb_stats {
6672 struct sched_group *busiest; /* Busiest group in this sd */
6673 struct sched_group *local; /* Local group in this sd */
6674 unsigned long total_load; /* Total load of all groups in sd */
6675 unsigned long total_capacity; /* Total capacity of all groups in sd */
6676 unsigned long avg_load; /* Average load across all groups in sd */
6678 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6679 struct sg_lb_stats local_stat; /* Statistics of the local group */
6682 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6685 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6686 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6687 * We must however clear busiest_stat::avg_load because
6688 * update_sd_pick_busiest() reads this before assignment.
6690 *sds = (struct sd_lb_stats){
6694 .total_capacity = 0UL,
6697 .sum_nr_running = 0,
6698 .group_type = group_other,
6704 * get_sd_load_idx - Obtain the load index for a given sched domain.
6705 * @sd: The sched_domain whose load_idx is to be obtained.
6706 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6708 * Return: The load index.
6710 static inline int get_sd_load_idx(struct sched_domain *sd,
6711 enum cpu_idle_type idle)
6717 load_idx = sd->busy_idx;
6720 case CPU_NEWLY_IDLE:
6721 load_idx = sd->newidle_idx;
6724 load_idx = sd->idle_idx;
6731 static unsigned long scale_rt_capacity(int cpu)
6733 struct rq *rq = cpu_rq(cpu);
6734 u64 total, used, age_stamp, avg;
6738 * Since we're reading these variables without serialization make sure
6739 * we read them once before doing sanity checks on them.
6741 age_stamp = READ_ONCE(rq->age_stamp);
6742 avg = READ_ONCE(rq->rt_avg);
6743 delta = __rq_clock_broken(rq) - age_stamp;
6745 if (unlikely(delta < 0))
6748 total = sched_avg_period() + delta;
6750 used = div_u64(avg, total);
6753 * deadline bandwidth is defined at system level so we must
6754 * weight this bandwidth with the max capacity of the system.
6755 * As a reminder, avg_bw is 20bits width and
6756 * scale_cpu_capacity is 10 bits width
6758 used += div_u64(rq->dl.avg_bw, arch_scale_cpu_capacity(NULL, cpu));
6760 if (likely(used < SCHED_CAPACITY_SCALE))
6761 return SCHED_CAPACITY_SCALE - used;
6766 void init_max_cpu_capacity(struct max_cpu_capacity *mcc)
6768 raw_spin_lock_init(&mcc->lock);
6773 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6775 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6776 struct sched_group *sdg = sd->groups;
6777 struct max_cpu_capacity *mcc;
6778 unsigned long max_capacity;
6780 unsigned long flags;
6782 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6784 mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
6786 raw_spin_lock_irqsave(&mcc->lock, flags);
6787 max_capacity = mcc->val;
6788 max_cap_cpu = mcc->cpu;
6790 if ((max_capacity > capacity && max_cap_cpu == cpu) ||
6791 (max_capacity < capacity)) {
6792 mcc->val = capacity;
6794 #ifdef CONFIG_SCHED_DEBUG
6795 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6796 pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity);
6800 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6802 skip_unlock: __attribute__ ((unused));
6803 capacity *= scale_rt_capacity(cpu);
6804 capacity >>= SCHED_CAPACITY_SHIFT;
6809 cpu_rq(cpu)->cpu_capacity = capacity;
6810 sdg->sgc->capacity = capacity;
6811 sdg->sgc->max_capacity = capacity;
6814 void update_group_capacity(struct sched_domain *sd, int cpu)
6816 struct sched_domain *child = sd->child;
6817 struct sched_group *group, *sdg = sd->groups;
6818 unsigned long capacity, max_capacity;
6819 unsigned long interval;
6821 interval = msecs_to_jiffies(sd->balance_interval);
6822 interval = clamp(interval, 1UL, max_load_balance_interval);
6823 sdg->sgc->next_update = jiffies + interval;
6826 update_cpu_capacity(sd, cpu);
6833 if (child->flags & SD_OVERLAP) {
6835 * SD_OVERLAP domains cannot assume that child groups
6836 * span the current group.
6839 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6840 struct sched_group_capacity *sgc;
6841 struct rq *rq = cpu_rq(cpu);
6844 * build_sched_domains() -> init_sched_groups_capacity()
6845 * gets here before we've attached the domains to the
6848 * Use capacity_of(), which is set irrespective of domains
6849 * in update_cpu_capacity().
6851 * This avoids capacity from being 0 and
6852 * causing divide-by-zero issues on boot.
6854 if (unlikely(!rq->sd)) {
6855 capacity += capacity_of(cpu);
6857 sgc = rq->sd->groups->sgc;
6858 capacity += sgc->capacity;
6861 max_capacity = max(capacity, max_capacity);
6865 * !SD_OVERLAP domains can assume that child groups
6866 * span the current group.
6869 group = child->groups;
6871 struct sched_group_capacity *sgc = group->sgc;
6873 capacity += sgc->capacity;
6874 max_capacity = max(sgc->max_capacity, max_capacity);
6875 group = group->next;
6876 } while (group != child->groups);
6879 sdg->sgc->capacity = capacity;
6880 sdg->sgc->max_capacity = max_capacity;
6884 * Check whether the capacity of the rq has been noticeably reduced by side
6885 * activity. The imbalance_pct is used for the threshold.
6886 * Return true is the capacity is reduced
6889 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6891 return ((rq->cpu_capacity * sd->imbalance_pct) <
6892 (rq->cpu_capacity_orig * 100));
6896 * Group imbalance indicates (and tries to solve) the problem where balancing
6897 * groups is inadequate due to tsk_cpus_allowed() constraints.
6899 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6900 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6903 * { 0 1 2 3 } { 4 5 6 7 }
6906 * If we were to balance group-wise we'd place two tasks in the first group and
6907 * two tasks in the second group. Clearly this is undesired as it will overload
6908 * cpu 3 and leave one of the cpus in the second group unused.
6910 * The current solution to this issue is detecting the skew in the first group
6911 * by noticing the lower domain failed to reach balance and had difficulty
6912 * moving tasks due to affinity constraints.
6914 * When this is so detected; this group becomes a candidate for busiest; see
6915 * update_sd_pick_busiest(). And calculate_imbalance() and
6916 * find_busiest_group() avoid some of the usual balance conditions to allow it
6917 * to create an effective group imbalance.
6919 * This is a somewhat tricky proposition since the next run might not find the
6920 * group imbalance and decide the groups need to be balanced again. A most
6921 * subtle and fragile situation.
6924 static inline int sg_imbalanced(struct sched_group *group)
6926 return group->sgc->imbalance;
6930 * group_has_capacity returns true if the group has spare capacity that could
6931 * be used by some tasks.
6932 * We consider that a group has spare capacity if the * number of task is
6933 * smaller than the number of CPUs or if the utilization is lower than the
6934 * available capacity for CFS tasks.
6935 * For the latter, we use a threshold to stabilize the state, to take into
6936 * account the variance of the tasks' load and to return true if the available
6937 * capacity in meaningful for the load balancer.
6938 * As an example, an available capacity of 1% can appear but it doesn't make
6939 * any benefit for the load balance.
6942 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6944 if (sgs->sum_nr_running < sgs->group_weight)
6947 if ((sgs->group_capacity * 100) >
6948 (sgs->group_util * env->sd->imbalance_pct))
6955 * group_is_overloaded returns true if the group has more tasks than it can
6957 * group_is_overloaded is not equals to !group_has_capacity because a group
6958 * with the exact right number of tasks, has no more spare capacity but is not
6959 * overloaded so both group_has_capacity and group_is_overloaded return
6963 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6965 if (sgs->sum_nr_running <= sgs->group_weight)
6968 if ((sgs->group_capacity * 100) <
6969 (sgs->group_util * env->sd->imbalance_pct))
6977 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
6978 * per-cpu capacity than sched_group ref.
6981 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
6983 return sg->sgc->max_capacity + capacity_margin - SCHED_LOAD_SCALE <
6984 ref->sgc->max_capacity;
6988 group_type group_classify(struct sched_group *group,
6989 struct sg_lb_stats *sgs)
6991 if (sgs->group_no_capacity)
6992 return group_overloaded;
6994 if (sg_imbalanced(group))
6995 return group_imbalanced;
6997 if (sgs->group_misfit_task)
6998 return group_misfit_task;
7004 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7005 * @env: The load balancing environment.
7006 * @group: sched_group whose statistics are to be updated.
7007 * @load_idx: Load index of sched_domain of this_cpu for load calc.
7008 * @local_group: Does group contain this_cpu.
7009 * @sgs: variable to hold the statistics for this group.
7010 * @overload: Indicate more than one runnable task for any CPU.
7011 * @overutilized: Indicate overutilization for any CPU.
7013 static inline void update_sg_lb_stats(struct lb_env *env,
7014 struct sched_group *group, int load_idx,
7015 int local_group, struct sg_lb_stats *sgs,
7016 bool *overload, bool *overutilized)
7021 memset(sgs, 0, sizeof(*sgs));
7023 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7024 struct rq *rq = cpu_rq(i);
7026 /* Bias balancing toward cpus of our domain */
7028 load = target_load(i, load_idx);
7030 load = source_load(i, load_idx);
7032 sgs->group_load += load;
7033 sgs->group_util += cpu_util(i);
7034 sgs->sum_nr_running += rq->cfs.h_nr_running;
7036 if (rq->nr_running > 1)
7039 #ifdef CONFIG_NUMA_BALANCING
7040 sgs->nr_numa_running += rq->nr_numa_running;
7041 sgs->nr_preferred_running += rq->nr_preferred_running;
7043 sgs->sum_weighted_load += weighted_cpuload(i);
7047 if (cpu_overutilized(i)) {
7048 *overutilized = true;
7049 if (!sgs->group_misfit_task && rq->misfit_task)
7050 sgs->group_misfit_task = capacity_of(i);
7054 /* Adjust by relative CPU capacity of the group */
7055 sgs->group_capacity = group->sgc->capacity;
7056 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7058 if (sgs->sum_nr_running)
7059 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7061 sgs->group_weight = group->group_weight;
7063 sgs->group_no_capacity = group_is_overloaded(env, sgs);
7064 sgs->group_type = group_classify(group, sgs);
7068 * update_sd_pick_busiest - return 1 on busiest group
7069 * @env: The load balancing environment.
7070 * @sds: sched_domain statistics
7071 * @sg: sched_group candidate to be checked for being the busiest
7072 * @sgs: sched_group statistics
7074 * Determine if @sg is a busier group than the previously selected
7077 * Return: %true if @sg is a busier group than the previously selected
7078 * busiest group. %false otherwise.
7080 static bool update_sd_pick_busiest(struct lb_env *env,
7081 struct sd_lb_stats *sds,
7082 struct sched_group *sg,
7083 struct sg_lb_stats *sgs)
7085 struct sg_lb_stats *busiest = &sds->busiest_stat;
7087 if (sgs->group_type > busiest->group_type)
7090 if (sgs->group_type < busiest->group_type)
7094 * Candidate sg doesn't face any serious load-balance problems
7095 * so don't pick it if the local sg is already filled up.
7097 if (sgs->group_type == group_other &&
7098 !group_has_capacity(env, &sds->local_stat))
7101 if (sgs->avg_load <= busiest->avg_load)
7105 * Candiate sg has no more than one task per cpu and has higher
7106 * per-cpu capacity. No reason to pull tasks to less capable cpus.
7108 if (sgs->sum_nr_running <= sgs->group_weight &&
7109 group_smaller_cpu_capacity(sds->local, sg))
7112 /* This is the busiest node in its class. */
7113 if (!(env->sd->flags & SD_ASYM_PACKING))
7117 * ASYM_PACKING needs to move all the work to the lowest
7118 * numbered CPUs in the group, therefore mark all groups
7119 * higher than ourself as busy.
7121 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
7125 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
7132 #ifdef CONFIG_NUMA_BALANCING
7133 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7135 if (sgs->sum_nr_running > sgs->nr_numa_running)
7137 if (sgs->sum_nr_running > sgs->nr_preferred_running)
7142 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7144 if (rq->nr_running > rq->nr_numa_running)
7146 if (rq->nr_running > rq->nr_preferred_running)
7151 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7156 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7160 #endif /* CONFIG_NUMA_BALANCING */
7163 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7164 * @env: The load balancing environment.
7165 * @sds: variable to hold the statistics for this sched_domain.
7167 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7169 struct sched_domain *child = env->sd->child;
7170 struct sched_group *sg = env->sd->groups;
7171 struct sg_lb_stats tmp_sgs;
7172 int load_idx, prefer_sibling = 0;
7173 bool overload = false, overutilized = false;
7175 if (child && child->flags & SD_PREFER_SIBLING)
7178 load_idx = get_sd_load_idx(env->sd, env->idle);
7181 struct sg_lb_stats *sgs = &tmp_sgs;
7184 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7187 sgs = &sds->local_stat;
7189 if (env->idle != CPU_NEWLY_IDLE ||
7190 time_after_eq(jiffies, sg->sgc->next_update))
7191 update_group_capacity(env->sd, env->dst_cpu);
7194 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7195 &overload, &overutilized);
7201 * In case the child domain prefers tasks go to siblings
7202 * first, lower the sg capacity so that we'll try
7203 * and move all the excess tasks away. We lower the capacity
7204 * of a group only if the local group has the capacity to fit
7205 * these excess tasks. The extra check prevents the case where
7206 * you always pull from the heaviest group when it is already
7207 * under-utilized (possible with a large weight task outweighs
7208 * the tasks on the system).
7210 if (prefer_sibling && sds->local &&
7211 group_has_capacity(env, &sds->local_stat) &&
7212 (sgs->sum_nr_running > 1)) {
7213 sgs->group_no_capacity = 1;
7214 sgs->group_type = group_classify(sg, sgs);
7218 * Ignore task groups with misfit tasks if local group has no
7219 * capacity or if per-cpu capacity isn't higher.
7221 if (sgs->group_type == group_misfit_task &&
7222 (!group_has_capacity(env, &sds->local_stat) ||
7223 !group_smaller_cpu_capacity(sg, sds->local)))
7224 sgs->group_type = group_other;
7226 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7228 sds->busiest_stat = *sgs;
7232 /* Now, start updating sd_lb_stats */
7233 sds->total_load += sgs->group_load;
7234 sds->total_capacity += sgs->group_capacity;
7237 } while (sg != env->sd->groups);
7239 if (env->sd->flags & SD_NUMA)
7240 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7242 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
7244 if (!env->sd->parent) {
7245 /* update overload indicator if we are at root domain */
7246 if (env->dst_rq->rd->overload != overload)
7247 env->dst_rq->rd->overload = overload;
7249 /* Update over-utilization (tipping point, U >= 0) indicator */
7250 if (env->dst_rq->rd->overutilized != overutilized)
7251 env->dst_rq->rd->overutilized = overutilized;
7253 if (!env->dst_rq->rd->overutilized && overutilized)
7254 env->dst_rq->rd->overutilized = true;
7259 * check_asym_packing - Check to see if the group is packed into the
7262 * This is primarily intended to used at the sibling level. Some
7263 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7264 * case of POWER7, it can move to lower SMT modes only when higher
7265 * threads are idle. When in lower SMT modes, the threads will
7266 * perform better since they share less core resources. Hence when we
7267 * have idle threads, we want them to be the higher ones.
7269 * This packing function is run on idle threads. It checks to see if
7270 * the busiest CPU in this domain (core in the P7 case) has a higher
7271 * CPU number than the packing function is being run on. Here we are
7272 * assuming lower CPU number will be equivalent to lower a SMT thread
7275 * Return: 1 when packing is required and a task should be moved to
7276 * this CPU. The amount of the imbalance is returned in *imbalance.
7278 * @env: The load balancing environment.
7279 * @sds: Statistics of the sched_domain which is to be packed
7281 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7285 if (!(env->sd->flags & SD_ASYM_PACKING))
7291 busiest_cpu = group_first_cpu(sds->busiest);
7292 if (env->dst_cpu > busiest_cpu)
7295 env->imbalance = DIV_ROUND_CLOSEST(
7296 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7297 SCHED_CAPACITY_SCALE);
7303 * fix_small_imbalance - Calculate the minor imbalance that exists
7304 * amongst the groups of a sched_domain, during
7306 * @env: The load balancing environment.
7307 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7310 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7312 unsigned long tmp, capa_now = 0, capa_move = 0;
7313 unsigned int imbn = 2;
7314 unsigned long scaled_busy_load_per_task;
7315 struct sg_lb_stats *local, *busiest;
7317 local = &sds->local_stat;
7318 busiest = &sds->busiest_stat;
7320 if (!local->sum_nr_running)
7321 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7322 else if (busiest->load_per_task > local->load_per_task)
7325 scaled_busy_load_per_task =
7326 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7327 busiest->group_capacity;
7329 if (busiest->avg_load + scaled_busy_load_per_task >=
7330 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7331 env->imbalance = busiest->load_per_task;
7336 * OK, we don't have enough imbalance to justify moving tasks,
7337 * however we may be able to increase total CPU capacity used by
7341 capa_now += busiest->group_capacity *
7342 min(busiest->load_per_task, busiest->avg_load);
7343 capa_now += local->group_capacity *
7344 min(local->load_per_task, local->avg_load);
7345 capa_now /= SCHED_CAPACITY_SCALE;
7347 /* Amount of load we'd subtract */
7348 if (busiest->avg_load > scaled_busy_load_per_task) {
7349 capa_move += busiest->group_capacity *
7350 min(busiest->load_per_task,
7351 busiest->avg_load - scaled_busy_load_per_task);
7354 /* Amount of load we'd add */
7355 if (busiest->avg_load * busiest->group_capacity <
7356 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7357 tmp = (busiest->avg_load * busiest->group_capacity) /
7358 local->group_capacity;
7360 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7361 local->group_capacity;
7363 capa_move += local->group_capacity *
7364 min(local->load_per_task, local->avg_load + tmp);
7365 capa_move /= SCHED_CAPACITY_SCALE;
7367 /* Move if we gain throughput */
7368 if (capa_move > capa_now)
7369 env->imbalance = busiest->load_per_task;
7373 * calculate_imbalance - Calculate the amount of imbalance present within the
7374 * groups of a given sched_domain during load balance.
7375 * @env: load balance environment
7376 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7378 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7380 unsigned long max_pull, load_above_capacity = ~0UL;
7381 struct sg_lb_stats *local, *busiest;
7383 local = &sds->local_stat;
7384 busiest = &sds->busiest_stat;
7386 if (busiest->group_type == group_imbalanced) {
7388 * In the group_imb case we cannot rely on group-wide averages
7389 * to ensure cpu-load equilibrium, look at wider averages. XXX
7391 busiest->load_per_task =
7392 min(busiest->load_per_task, sds->avg_load);
7396 * In the presence of smp nice balancing, certain scenarios can have
7397 * max load less than avg load(as we skip the groups at or below
7398 * its cpu_capacity, while calculating max_load..)
7400 if (busiest->avg_load <= sds->avg_load ||
7401 local->avg_load >= sds->avg_load) {
7402 /* Misfitting tasks should be migrated in any case */
7403 if (busiest->group_type == group_misfit_task) {
7404 env->imbalance = busiest->group_misfit_task;
7409 * Busiest group is overloaded, local is not, use the spare
7410 * cycles to maximize throughput
7412 if (busiest->group_type == group_overloaded &&
7413 local->group_type <= group_misfit_task) {
7414 env->imbalance = busiest->load_per_task;
7419 return fix_small_imbalance(env, sds);
7423 * If there aren't any idle cpus, avoid creating some.
7425 if (busiest->group_type == group_overloaded &&
7426 local->group_type == group_overloaded) {
7427 load_above_capacity = busiest->sum_nr_running *
7429 if (load_above_capacity > busiest->group_capacity)
7430 load_above_capacity -= busiest->group_capacity;
7432 load_above_capacity = ~0UL;
7436 * We're trying to get all the cpus to the average_load, so we don't
7437 * want to push ourselves above the average load, nor do we wish to
7438 * reduce the max loaded cpu below the average load. At the same time,
7439 * we also don't want to reduce the group load below the group capacity
7440 * (so that we can implement power-savings policies etc). Thus we look
7441 * for the minimum possible imbalance.
7443 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7445 /* How much load to actually move to equalise the imbalance */
7446 env->imbalance = min(
7447 max_pull * busiest->group_capacity,
7448 (sds->avg_load - local->avg_load) * local->group_capacity
7449 ) / SCHED_CAPACITY_SCALE;
7451 /* Boost imbalance to allow misfit task to be balanced. */
7452 if (busiest->group_type == group_misfit_task)
7453 env->imbalance = max_t(long, env->imbalance,
7454 busiest->group_misfit_task);
7457 * if *imbalance is less than the average load per runnable task
7458 * there is no guarantee that any tasks will be moved so we'll have
7459 * a think about bumping its value to force at least one task to be
7462 if (env->imbalance < busiest->load_per_task)
7463 return fix_small_imbalance(env, sds);
7466 /******* find_busiest_group() helpers end here *********************/
7469 * find_busiest_group - Returns the busiest group within the sched_domain
7470 * if there is an imbalance. If there isn't an imbalance, and
7471 * the user has opted for power-savings, it returns a group whose
7472 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7473 * such a group exists.
7475 * Also calculates the amount of weighted load which should be moved
7476 * to restore balance.
7478 * @env: The load balancing environment.
7480 * Return: - The busiest group if imbalance exists.
7481 * - If no imbalance and user has opted for power-savings balance,
7482 * return the least loaded group whose CPUs can be
7483 * put to idle by rebalancing its tasks onto our group.
7485 static struct sched_group *find_busiest_group(struct lb_env *env)
7487 struct sg_lb_stats *local, *busiest;
7488 struct sd_lb_stats sds;
7490 init_sd_lb_stats(&sds);
7493 * Compute the various statistics relavent for load balancing at
7496 update_sd_lb_stats(env, &sds);
7498 if (energy_aware() && !env->dst_rq->rd->overutilized)
7501 local = &sds.local_stat;
7502 busiest = &sds.busiest_stat;
7504 /* ASYM feature bypasses nice load balance check */
7505 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7506 check_asym_packing(env, &sds))
7509 /* There is no busy sibling group to pull tasks from */
7510 if (!sds.busiest || busiest->sum_nr_running == 0)
7513 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7514 / sds.total_capacity;
7517 * If the busiest group is imbalanced the below checks don't
7518 * work because they assume all things are equal, which typically
7519 * isn't true due to cpus_allowed constraints and the like.
7521 if (busiest->group_type == group_imbalanced)
7524 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7525 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7526 busiest->group_no_capacity)
7529 /* Misfitting tasks should be dealt with regardless of the avg load */
7530 if (busiest->group_type == group_misfit_task) {
7535 * If the local group is busier than the selected busiest group
7536 * don't try and pull any tasks.
7538 if (local->avg_load >= busiest->avg_load)
7542 * Don't pull any tasks if this group is already above the domain
7545 if (local->avg_load >= sds.avg_load)
7548 if (env->idle == CPU_IDLE) {
7550 * This cpu is idle. If the busiest group is not overloaded
7551 * and there is no imbalance between this and busiest group
7552 * wrt idle cpus, it is balanced. The imbalance becomes
7553 * significant if the diff is greater than 1 otherwise we
7554 * might end up to just move the imbalance on another group
7556 if ((busiest->group_type != group_overloaded) &&
7557 (local->idle_cpus <= (busiest->idle_cpus + 1)) &&
7558 !group_smaller_cpu_capacity(sds.busiest, sds.local))
7562 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7563 * imbalance_pct to be conservative.
7565 if (100 * busiest->avg_load <=
7566 env->sd->imbalance_pct * local->avg_load)
7571 env->busiest_group_type = busiest->group_type;
7572 /* Looks like there is an imbalance. Compute it */
7573 calculate_imbalance(env, &sds);
7582 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7584 static struct rq *find_busiest_queue(struct lb_env *env,
7585 struct sched_group *group)
7587 struct rq *busiest = NULL, *rq;
7588 unsigned long busiest_load = 0, busiest_capacity = 1;
7591 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7592 unsigned long capacity, wl;
7596 rt = fbq_classify_rq(rq);
7599 * We classify groups/runqueues into three groups:
7600 * - regular: there are !numa tasks
7601 * - remote: there are numa tasks that run on the 'wrong' node
7602 * - all: there is no distinction
7604 * In order to avoid migrating ideally placed numa tasks,
7605 * ignore those when there's better options.
7607 * If we ignore the actual busiest queue to migrate another
7608 * task, the next balance pass can still reduce the busiest
7609 * queue by moving tasks around inside the node.
7611 * If we cannot move enough load due to this classification
7612 * the next pass will adjust the group classification and
7613 * allow migration of more tasks.
7615 * Both cases only affect the total convergence complexity.
7617 if (rt > env->fbq_type)
7620 capacity = capacity_of(i);
7622 wl = weighted_cpuload(i);
7625 * When comparing with imbalance, use weighted_cpuload()
7626 * which is not scaled with the cpu capacity.
7629 if (rq->nr_running == 1 && wl > env->imbalance &&
7630 !check_cpu_capacity(rq, env->sd) &&
7631 env->busiest_group_type != group_misfit_task)
7635 * For the load comparisons with the other cpu's, consider
7636 * the weighted_cpuload() scaled with the cpu capacity, so
7637 * that the load can be moved away from the cpu that is
7638 * potentially running at a lower capacity.
7640 * Thus we're looking for max(wl_i / capacity_i), crosswise
7641 * multiplication to rid ourselves of the division works out
7642 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7643 * our previous maximum.
7645 if (wl * busiest_capacity > busiest_load * capacity) {
7647 busiest_capacity = capacity;
7656 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7657 * so long as it is large enough.
7659 #define MAX_PINNED_INTERVAL 512
7661 /* Working cpumask for load_balance and load_balance_newidle. */
7662 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7664 static int need_active_balance(struct lb_env *env)
7666 struct sched_domain *sd = env->sd;
7668 if (env->idle == CPU_NEWLY_IDLE) {
7671 * ASYM_PACKING needs to force migrate tasks from busy but
7672 * higher numbered CPUs in order to pack all tasks in the
7673 * lowest numbered CPUs.
7675 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7680 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7681 * It's worth migrating the task if the src_cpu's capacity is reduced
7682 * because of other sched_class or IRQs if more capacity stays
7683 * available on dst_cpu.
7685 if ((env->idle != CPU_NOT_IDLE) &&
7686 (env->src_rq->cfs.h_nr_running == 1)) {
7687 if ((check_cpu_capacity(env->src_rq, sd)) &&
7688 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7692 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7693 env->src_rq->cfs.h_nr_running == 1 &&
7694 cpu_overutilized(env->src_cpu) &&
7695 !cpu_overutilized(env->dst_cpu)) {
7699 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7702 static int active_load_balance_cpu_stop(void *data);
7704 static int should_we_balance(struct lb_env *env)
7706 struct sched_group *sg = env->sd->groups;
7707 struct cpumask *sg_cpus, *sg_mask;
7708 int cpu, balance_cpu = -1;
7711 * In the newly idle case, we will allow all the cpu's
7712 * to do the newly idle load balance.
7714 if (env->idle == CPU_NEWLY_IDLE)
7717 sg_cpus = sched_group_cpus(sg);
7718 sg_mask = sched_group_mask(sg);
7719 /* Try to find first idle cpu */
7720 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7721 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7728 if (balance_cpu == -1)
7729 balance_cpu = group_balance_cpu(sg);
7732 * First idle cpu or the first cpu(busiest) in this sched group
7733 * is eligible for doing load balancing at this and above domains.
7735 return balance_cpu == env->dst_cpu;
7739 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7740 * tasks if there is an imbalance.
7742 static int load_balance(int this_cpu, struct rq *this_rq,
7743 struct sched_domain *sd, enum cpu_idle_type idle,
7744 int *continue_balancing)
7746 int ld_moved, cur_ld_moved, active_balance = 0;
7747 struct sched_domain *sd_parent = sd->parent;
7748 struct sched_group *group;
7750 unsigned long flags;
7751 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7753 struct lb_env env = {
7755 .dst_cpu = this_cpu,
7757 .dst_grpmask = sched_group_cpus(sd->groups),
7759 .loop_break = sched_nr_migrate_break,
7762 .tasks = LIST_HEAD_INIT(env.tasks),
7766 * For NEWLY_IDLE load_balancing, we don't need to consider
7767 * other cpus in our group
7769 if (idle == CPU_NEWLY_IDLE)
7770 env.dst_grpmask = NULL;
7772 cpumask_copy(cpus, cpu_active_mask);
7774 schedstat_inc(sd, lb_count[idle]);
7777 if (!should_we_balance(&env)) {
7778 *continue_balancing = 0;
7782 group = find_busiest_group(&env);
7784 schedstat_inc(sd, lb_nobusyg[idle]);
7788 busiest = find_busiest_queue(&env, group);
7790 schedstat_inc(sd, lb_nobusyq[idle]);
7794 BUG_ON(busiest == env.dst_rq);
7796 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7798 env.src_cpu = busiest->cpu;
7799 env.src_rq = busiest;
7802 if (busiest->nr_running > 1) {
7804 * Attempt to move tasks. If find_busiest_group has found
7805 * an imbalance but busiest->nr_running <= 1, the group is
7806 * still unbalanced. ld_moved simply stays zero, so it is
7807 * correctly treated as an imbalance.
7809 env.flags |= LBF_ALL_PINNED;
7810 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7813 raw_spin_lock_irqsave(&busiest->lock, flags);
7816 * cur_ld_moved - load moved in current iteration
7817 * ld_moved - cumulative load moved across iterations
7819 cur_ld_moved = detach_tasks(&env);
7821 * We want to potentially lower env.src_cpu's OPP.
7824 update_capacity_of(env.src_cpu);
7827 * We've detached some tasks from busiest_rq. Every
7828 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7829 * unlock busiest->lock, and we are able to be sure
7830 * that nobody can manipulate the tasks in parallel.
7831 * See task_rq_lock() family for the details.
7834 raw_spin_unlock(&busiest->lock);
7838 ld_moved += cur_ld_moved;
7841 local_irq_restore(flags);
7843 if (env.flags & LBF_NEED_BREAK) {
7844 env.flags &= ~LBF_NEED_BREAK;
7849 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7850 * us and move them to an alternate dst_cpu in our sched_group
7851 * where they can run. The upper limit on how many times we
7852 * iterate on same src_cpu is dependent on number of cpus in our
7855 * This changes load balance semantics a bit on who can move
7856 * load to a given_cpu. In addition to the given_cpu itself
7857 * (or a ilb_cpu acting on its behalf where given_cpu is
7858 * nohz-idle), we now have balance_cpu in a position to move
7859 * load to given_cpu. In rare situations, this may cause
7860 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7861 * _independently_ and at _same_ time to move some load to
7862 * given_cpu) causing exceess load to be moved to given_cpu.
7863 * This however should not happen so much in practice and
7864 * moreover subsequent load balance cycles should correct the
7865 * excess load moved.
7867 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7869 /* Prevent to re-select dst_cpu via env's cpus */
7870 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7872 env.dst_rq = cpu_rq(env.new_dst_cpu);
7873 env.dst_cpu = env.new_dst_cpu;
7874 env.flags &= ~LBF_DST_PINNED;
7876 env.loop_break = sched_nr_migrate_break;
7879 * Go back to "more_balance" rather than "redo" since we
7880 * need to continue with same src_cpu.
7886 * We failed to reach balance because of affinity.
7889 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7891 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7892 *group_imbalance = 1;
7895 /* All tasks on this runqueue were pinned by CPU affinity */
7896 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7897 cpumask_clear_cpu(cpu_of(busiest), cpus);
7898 if (!cpumask_empty(cpus)) {
7900 env.loop_break = sched_nr_migrate_break;
7903 goto out_all_pinned;
7908 schedstat_inc(sd, lb_failed[idle]);
7910 * Increment the failure counter only on periodic balance.
7911 * We do not want newidle balance, which can be very
7912 * frequent, pollute the failure counter causing
7913 * excessive cache_hot migrations and active balances.
7915 if (idle != CPU_NEWLY_IDLE)
7916 if (env.src_grp_nr_running > 1)
7917 sd->nr_balance_failed++;
7919 if (need_active_balance(&env)) {
7920 raw_spin_lock_irqsave(&busiest->lock, flags);
7922 /* don't kick the active_load_balance_cpu_stop,
7923 * if the curr task on busiest cpu can't be
7926 if (!cpumask_test_cpu(this_cpu,
7927 tsk_cpus_allowed(busiest->curr))) {
7928 raw_spin_unlock_irqrestore(&busiest->lock,
7930 env.flags |= LBF_ALL_PINNED;
7931 goto out_one_pinned;
7935 * ->active_balance synchronizes accesses to
7936 * ->active_balance_work. Once set, it's cleared
7937 * only after active load balance is finished.
7939 if (!busiest->active_balance) {
7940 busiest->active_balance = 1;
7941 busiest->push_cpu = this_cpu;
7944 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7946 if (active_balance) {
7947 stop_one_cpu_nowait(cpu_of(busiest),
7948 active_load_balance_cpu_stop, busiest,
7949 &busiest->active_balance_work);
7953 * We've kicked active balancing, reset the failure
7956 sd->nr_balance_failed = sd->cache_nice_tries+1;
7959 sd->nr_balance_failed = 0;
7961 if (likely(!active_balance)) {
7962 /* We were unbalanced, so reset the balancing interval */
7963 sd->balance_interval = sd->min_interval;
7966 * If we've begun active balancing, start to back off. This
7967 * case may not be covered by the all_pinned logic if there
7968 * is only 1 task on the busy runqueue (because we don't call
7971 if (sd->balance_interval < sd->max_interval)
7972 sd->balance_interval *= 2;
7979 * We reach balance although we may have faced some affinity
7980 * constraints. Clear the imbalance flag if it was set.
7983 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7985 if (*group_imbalance)
7986 *group_imbalance = 0;
7991 * We reach balance because all tasks are pinned at this level so
7992 * we can't migrate them. Let the imbalance flag set so parent level
7993 * can try to migrate them.
7995 schedstat_inc(sd, lb_balanced[idle]);
7997 sd->nr_balance_failed = 0;
8000 /* tune up the balancing interval */
8001 if (((env.flags & LBF_ALL_PINNED) &&
8002 sd->balance_interval < MAX_PINNED_INTERVAL) ||
8003 (sd->balance_interval < sd->max_interval))
8004 sd->balance_interval *= 2;
8011 static inline unsigned long
8012 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
8014 unsigned long interval = sd->balance_interval;
8017 interval *= sd->busy_factor;
8019 /* scale ms to jiffies */
8020 interval = msecs_to_jiffies(interval);
8021 interval = clamp(interval, 1UL, max_load_balance_interval);
8027 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
8029 unsigned long interval, next;
8031 interval = get_sd_balance_interval(sd, cpu_busy);
8032 next = sd->last_balance + interval;
8034 if (time_after(*next_balance, next))
8035 *next_balance = next;
8039 * idle_balance is called by schedule() if this_cpu is about to become
8040 * idle. Attempts to pull tasks from other CPUs.
8042 static int idle_balance(struct rq *this_rq)
8044 unsigned long next_balance = jiffies + HZ;
8045 int this_cpu = this_rq->cpu;
8046 struct sched_domain *sd;
8047 int pulled_task = 0;
8050 idle_enter_fair(this_rq);
8053 * We must set idle_stamp _before_ calling idle_balance(), such that we
8054 * measure the duration of idle_balance() as idle time.
8056 this_rq->idle_stamp = rq_clock(this_rq);
8058 if (!energy_aware() &&
8059 (this_rq->avg_idle < sysctl_sched_migration_cost ||
8060 !this_rq->rd->overload)) {
8062 sd = rcu_dereference_check_sched_domain(this_rq->sd);
8064 update_next_balance(sd, 0, &next_balance);
8070 raw_spin_unlock(&this_rq->lock);
8072 update_blocked_averages(this_cpu);
8074 for_each_domain(this_cpu, sd) {
8075 int continue_balancing = 1;
8076 u64 t0, domain_cost;
8078 if (!(sd->flags & SD_LOAD_BALANCE))
8081 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8082 update_next_balance(sd, 0, &next_balance);
8086 if (sd->flags & SD_BALANCE_NEWIDLE) {
8087 t0 = sched_clock_cpu(this_cpu);
8089 pulled_task = load_balance(this_cpu, this_rq,
8091 &continue_balancing);
8093 domain_cost = sched_clock_cpu(this_cpu) - t0;
8094 if (domain_cost > sd->max_newidle_lb_cost)
8095 sd->max_newidle_lb_cost = domain_cost;
8097 curr_cost += domain_cost;
8100 update_next_balance(sd, 0, &next_balance);
8103 * Stop searching for tasks to pull if there are
8104 * now runnable tasks on this rq.
8106 if (pulled_task || this_rq->nr_running > 0)
8111 raw_spin_lock(&this_rq->lock);
8113 if (curr_cost > this_rq->max_idle_balance_cost)
8114 this_rq->max_idle_balance_cost = curr_cost;
8117 * While browsing the domains, we released the rq lock, a task could
8118 * have been enqueued in the meantime. Since we're not going idle,
8119 * pretend we pulled a task.
8121 if (this_rq->cfs.h_nr_running && !pulled_task)
8125 /* Move the next balance forward */
8126 if (time_after(this_rq->next_balance, next_balance))
8127 this_rq->next_balance = next_balance;
8129 /* Is there a task of a high priority class? */
8130 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8134 idle_exit_fair(this_rq);
8135 this_rq->idle_stamp = 0;
8142 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8143 * running tasks off the busiest CPU onto idle CPUs. It requires at
8144 * least 1 task to be running on each physical CPU where possible, and
8145 * avoids physical / logical imbalances.
8147 static int active_load_balance_cpu_stop(void *data)
8149 struct rq *busiest_rq = data;
8150 int busiest_cpu = cpu_of(busiest_rq);
8151 int target_cpu = busiest_rq->push_cpu;
8152 struct rq *target_rq = cpu_rq(target_cpu);
8153 struct sched_domain *sd;
8154 struct task_struct *p = NULL;
8156 raw_spin_lock_irq(&busiest_rq->lock);
8158 /* make sure the requested cpu hasn't gone down in the meantime */
8159 if (unlikely(busiest_cpu != smp_processor_id() ||
8160 !busiest_rq->active_balance))
8163 /* Is there any task to move? */
8164 if (busiest_rq->nr_running <= 1)
8168 * This condition is "impossible", if it occurs
8169 * we need to fix it. Originally reported by
8170 * Bjorn Helgaas on a 128-cpu setup.
8172 BUG_ON(busiest_rq == target_rq);
8174 /* Search for an sd spanning us and the target CPU. */
8176 for_each_domain(target_cpu, sd) {
8177 if ((sd->flags & SD_LOAD_BALANCE) &&
8178 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8183 struct lb_env env = {
8185 .dst_cpu = target_cpu,
8186 .dst_rq = target_rq,
8187 .src_cpu = busiest_rq->cpu,
8188 .src_rq = busiest_rq,
8192 schedstat_inc(sd, alb_count);
8194 p = detach_one_task(&env);
8196 schedstat_inc(sd, alb_pushed);
8198 * We want to potentially lower env.src_cpu's OPP.
8200 update_capacity_of(env.src_cpu);
8203 schedstat_inc(sd, alb_failed);
8207 busiest_rq->active_balance = 0;
8208 raw_spin_unlock(&busiest_rq->lock);
8211 attach_one_task(target_rq, p);
8218 static inline int on_null_domain(struct rq *rq)
8220 return unlikely(!rcu_dereference_sched(rq->sd));
8223 #ifdef CONFIG_NO_HZ_COMMON
8225 * idle load balancing details
8226 * - When one of the busy CPUs notice that there may be an idle rebalancing
8227 * needed, they will kick the idle load balancer, which then does idle
8228 * load balancing for all the idle CPUs.
8231 cpumask_var_t idle_cpus_mask;
8233 unsigned long next_balance; /* in jiffy units */
8234 } nohz ____cacheline_aligned;
8236 static inline int find_new_ilb(void)
8238 int ilb = cpumask_first(nohz.idle_cpus_mask);
8240 if (ilb < nr_cpu_ids && idle_cpu(ilb))
8247 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8248 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8249 * CPU (if there is one).
8251 static void nohz_balancer_kick(void)
8255 nohz.next_balance++;
8257 ilb_cpu = find_new_ilb();
8259 if (ilb_cpu >= nr_cpu_ids)
8262 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8265 * Use smp_send_reschedule() instead of resched_cpu().
8266 * This way we generate a sched IPI on the target cpu which
8267 * is idle. And the softirq performing nohz idle load balance
8268 * will be run before returning from the IPI.
8270 smp_send_reschedule(ilb_cpu);
8274 static inline void nohz_balance_exit_idle(int cpu)
8276 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8278 * Completely isolated CPUs don't ever set, so we must test.
8280 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8281 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8282 atomic_dec(&nohz.nr_cpus);
8284 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8288 static inline void set_cpu_sd_state_busy(void)
8290 struct sched_domain *sd;
8291 int cpu = smp_processor_id();
8294 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8296 if (!sd || !sd->nohz_idle)
8300 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
8305 void set_cpu_sd_state_idle(void)
8307 struct sched_domain *sd;
8308 int cpu = smp_processor_id();
8311 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8313 if (!sd || sd->nohz_idle)
8317 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8323 * This routine will record that the cpu is going idle with tick stopped.
8324 * This info will be used in performing idle load balancing in the future.
8326 void nohz_balance_enter_idle(int cpu)
8329 * If this cpu is going down, then nothing needs to be done.
8331 if (!cpu_active(cpu))
8334 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8338 * If we're a completely isolated CPU, we don't play.
8340 if (on_null_domain(cpu_rq(cpu)))
8343 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8344 atomic_inc(&nohz.nr_cpus);
8345 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8348 static int sched_ilb_notifier(struct notifier_block *nfb,
8349 unsigned long action, void *hcpu)
8351 switch (action & ~CPU_TASKS_FROZEN) {
8353 nohz_balance_exit_idle(smp_processor_id());
8361 static DEFINE_SPINLOCK(balancing);
8364 * Scale the max load_balance interval with the number of CPUs in the system.
8365 * This trades load-balance latency on larger machines for less cross talk.
8367 void update_max_interval(void)
8369 max_load_balance_interval = HZ*num_online_cpus()/10;
8373 * It checks each scheduling domain to see if it is due to be balanced,
8374 * and initiates a balancing operation if so.
8376 * Balancing parameters are set up in init_sched_domains.
8378 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8380 int continue_balancing = 1;
8382 unsigned long interval;
8383 struct sched_domain *sd;
8384 /* Earliest time when we have to do rebalance again */
8385 unsigned long next_balance = jiffies + 60*HZ;
8386 int update_next_balance = 0;
8387 int need_serialize, need_decay = 0;
8390 update_blocked_averages(cpu);
8393 for_each_domain(cpu, sd) {
8395 * Decay the newidle max times here because this is a regular
8396 * visit to all the domains. Decay ~1% per second.
8398 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8399 sd->max_newidle_lb_cost =
8400 (sd->max_newidle_lb_cost * 253) / 256;
8401 sd->next_decay_max_lb_cost = jiffies + HZ;
8404 max_cost += sd->max_newidle_lb_cost;
8406 if (!(sd->flags & SD_LOAD_BALANCE))
8410 * Stop the load balance at this level. There is another
8411 * CPU in our sched group which is doing load balancing more
8414 if (!continue_balancing) {
8420 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8422 need_serialize = sd->flags & SD_SERIALIZE;
8423 if (need_serialize) {
8424 if (!spin_trylock(&balancing))
8428 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8429 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8431 * The LBF_DST_PINNED logic could have changed
8432 * env->dst_cpu, so we can't know our idle
8433 * state even if we migrated tasks. Update it.
8435 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8437 sd->last_balance = jiffies;
8438 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8441 spin_unlock(&balancing);
8443 if (time_after(next_balance, sd->last_balance + interval)) {
8444 next_balance = sd->last_balance + interval;
8445 update_next_balance = 1;
8450 * Ensure the rq-wide value also decays but keep it at a
8451 * reasonable floor to avoid funnies with rq->avg_idle.
8453 rq->max_idle_balance_cost =
8454 max((u64)sysctl_sched_migration_cost, max_cost);
8459 * next_balance will be updated only when there is a need.
8460 * When the cpu is attached to null domain for ex, it will not be
8463 if (likely(update_next_balance)) {
8464 rq->next_balance = next_balance;
8466 #ifdef CONFIG_NO_HZ_COMMON
8468 * If this CPU has been elected to perform the nohz idle
8469 * balance. Other idle CPUs have already rebalanced with
8470 * nohz_idle_balance() and nohz.next_balance has been
8471 * updated accordingly. This CPU is now running the idle load
8472 * balance for itself and we need to update the
8473 * nohz.next_balance accordingly.
8475 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8476 nohz.next_balance = rq->next_balance;
8481 #ifdef CONFIG_NO_HZ_COMMON
8483 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8484 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8486 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8488 int this_cpu = this_rq->cpu;
8491 /* Earliest time when we have to do rebalance again */
8492 unsigned long next_balance = jiffies + 60*HZ;
8493 int update_next_balance = 0;
8495 if (idle != CPU_IDLE ||
8496 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8499 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8500 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8504 * If this cpu gets work to do, stop the load balancing
8505 * work being done for other cpus. Next load
8506 * balancing owner will pick it up.
8511 rq = cpu_rq(balance_cpu);
8514 * If time for next balance is due,
8517 if (time_after_eq(jiffies, rq->next_balance)) {
8518 raw_spin_lock_irq(&rq->lock);
8519 update_rq_clock(rq);
8520 update_idle_cpu_load(rq);
8521 raw_spin_unlock_irq(&rq->lock);
8522 rebalance_domains(rq, CPU_IDLE);
8525 if (time_after(next_balance, rq->next_balance)) {
8526 next_balance = rq->next_balance;
8527 update_next_balance = 1;
8532 * next_balance will be updated only when there is a need.
8533 * When the CPU is attached to null domain for ex, it will not be
8536 if (likely(update_next_balance))
8537 nohz.next_balance = next_balance;
8539 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8543 * Current heuristic for kicking the idle load balancer in the presence
8544 * of an idle cpu in the system.
8545 * - This rq has more than one task.
8546 * - This rq has at least one CFS task and the capacity of the CPU is
8547 * significantly reduced because of RT tasks or IRQs.
8548 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8549 * multiple busy cpu.
8550 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8551 * domain span are idle.
8553 static inline bool nohz_kick_needed(struct rq *rq)
8555 unsigned long now = jiffies;
8556 struct sched_domain *sd;
8557 struct sched_group_capacity *sgc;
8558 int nr_busy, cpu = rq->cpu;
8561 if (unlikely(rq->idle_balance))
8565 * We may be recently in ticked or tickless idle mode. At the first
8566 * busy tick after returning from idle, we will update the busy stats.
8568 set_cpu_sd_state_busy();
8569 nohz_balance_exit_idle(cpu);
8572 * None are in tickless mode and hence no need for NOHZ idle load
8575 if (likely(!atomic_read(&nohz.nr_cpus)))
8578 if (time_before(now, nohz.next_balance))
8581 if (rq->nr_running >= 2 &&
8582 (!energy_aware() || cpu_overutilized(cpu)))
8586 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8587 if (sd && !energy_aware()) {
8588 sgc = sd->groups->sgc;
8589 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8598 sd = rcu_dereference(rq->sd);
8600 if ((rq->cfs.h_nr_running >= 1) &&
8601 check_cpu_capacity(rq, sd)) {
8607 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8608 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8609 sched_domain_span(sd)) < cpu)) {
8619 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8623 * run_rebalance_domains is triggered when needed from the scheduler tick.
8624 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8626 static void run_rebalance_domains(struct softirq_action *h)
8628 struct rq *this_rq = this_rq();
8629 enum cpu_idle_type idle = this_rq->idle_balance ?
8630 CPU_IDLE : CPU_NOT_IDLE;
8633 * If this cpu has a pending nohz_balance_kick, then do the
8634 * balancing on behalf of the other idle cpus whose ticks are
8635 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8636 * give the idle cpus a chance to load balance. Else we may
8637 * load balance only within the local sched_domain hierarchy
8638 * and abort nohz_idle_balance altogether if we pull some load.
8640 nohz_idle_balance(this_rq, idle);
8641 rebalance_domains(this_rq, idle);
8645 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8647 void trigger_load_balance(struct rq *rq)
8649 /* Don't need to rebalance while attached to NULL domain */
8650 if (unlikely(on_null_domain(rq)))
8653 if (time_after_eq(jiffies, rq->next_balance))
8654 raise_softirq(SCHED_SOFTIRQ);
8655 #ifdef CONFIG_NO_HZ_COMMON
8656 if (nohz_kick_needed(rq))
8657 nohz_balancer_kick();
8661 static void rq_online_fair(struct rq *rq)
8665 update_runtime_enabled(rq);
8668 static void rq_offline_fair(struct rq *rq)
8672 /* Ensure any throttled groups are reachable by pick_next_task */
8673 unthrottle_offline_cfs_rqs(rq);
8676 #endif /* CONFIG_SMP */
8679 * scheduler tick hitting a task of our scheduling class:
8681 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8683 struct cfs_rq *cfs_rq;
8684 struct sched_entity *se = &curr->se;
8686 for_each_sched_entity(se) {
8687 cfs_rq = cfs_rq_of(se);
8688 entity_tick(cfs_rq, se, queued);
8691 if (static_branch_unlikely(&sched_numa_balancing))
8692 task_tick_numa(rq, curr);
8694 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr)))
8695 rq->rd->overutilized = true;
8697 rq->misfit_task = !task_fits_max(curr, rq->cpu);
8701 * called on fork with the child task as argument from the parent's context
8702 * - child not yet on the tasklist
8703 * - preemption disabled
8705 static void task_fork_fair(struct task_struct *p)
8707 struct cfs_rq *cfs_rq;
8708 struct sched_entity *se = &p->se, *curr;
8709 int this_cpu = smp_processor_id();
8710 struct rq *rq = this_rq();
8711 unsigned long flags;
8713 raw_spin_lock_irqsave(&rq->lock, flags);
8715 update_rq_clock(rq);
8717 cfs_rq = task_cfs_rq(current);
8718 curr = cfs_rq->curr;
8721 * Not only the cpu but also the task_group of the parent might have
8722 * been changed after parent->se.parent,cfs_rq were copied to
8723 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8724 * of child point to valid ones.
8727 __set_task_cpu(p, this_cpu);
8730 update_curr(cfs_rq);
8733 se->vruntime = curr->vruntime;
8734 place_entity(cfs_rq, se, 1);
8736 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8738 * Upon rescheduling, sched_class::put_prev_task() will place
8739 * 'current' within the tree based on its new key value.
8741 swap(curr->vruntime, se->vruntime);
8745 se->vruntime -= cfs_rq->min_vruntime;
8747 raw_spin_unlock_irqrestore(&rq->lock, flags);
8751 * Priority of the task has changed. Check to see if we preempt
8755 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8757 if (!task_on_rq_queued(p))
8761 * Reschedule if we are currently running on this runqueue and
8762 * our priority decreased, or if we are not currently running on
8763 * this runqueue and our priority is higher than the current's
8765 if (rq->curr == p) {
8766 if (p->prio > oldprio)
8769 check_preempt_curr(rq, p, 0);
8772 static inline bool vruntime_normalized(struct task_struct *p)
8774 struct sched_entity *se = &p->se;
8777 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8778 * the dequeue_entity(.flags=0) will already have normalized the
8785 * When !on_rq, vruntime of the task has usually NOT been normalized.
8786 * But there are some cases where it has already been normalized:
8788 * - A forked child which is waiting for being woken up by
8789 * wake_up_new_task().
8790 * - A task which has been woken up by try_to_wake_up() and
8791 * waiting for actually being woken up by sched_ttwu_pending().
8793 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8799 static void detach_task_cfs_rq(struct task_struct *p)
8801 struct sched_entity *se = &p->se;
8802 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8804 if (!vruntime_normalized(p)) {
8806 * Fix up our vruntime so that the current sleep doesn't
8807 * cause 'unlimited' sleep bonus.
8809 place_entity(cfs_rq, se, 0);
8810 se->vruntime -= cfs_rq->min_vruntime;
8813 /* Catch up with the cfs_rq and remove our load when we leave */
8814 detach_entity_load_avg(cfs_rq, se);
8817 static void attach_task_cfs_rq(struct task_struct *p)
8819 struct sched_entity *se = &p->se;
8820 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8822 #ifdef CONFIG_FAIR_GROUP_SCHED
8824 * Since the real-depth could have been changed (only FAIR
8825 * class maintain depth value), reset depth properly.
8827 se->depth = se->parent ? se->parent->depth + 1 : 0;
8830 /* Synchronize task with its cfs_rq */
8831 attach_entity_load_avg(cfs_rq, se);
8833 if (!vruntime_normalized(p))
8834 se->vruntime += cfs_rq->min_vruntime;
8837 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8839 detach_task_cfs_rq(p);
8842 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8844 attach_task_cfs_rq(p);
8846 if (task_on_rq_queued(p)) {
8848 * We were most likely switched from sched_rt, so
8849 * kick off the schedule if running, otherwise just see
8850 * if we can still preempt the current task.
8855 check_preempt_curr(rq, p, 0);
8859 /* Account for a task changing its policy or group.
8861 * This routine is mostly called to set cfs_rq->curr field when a task
8862 * migrates between groups/classes.
8864 static void set_curr_task_fair(struct rq *rq)
8866 struct sched_entity *se = &rq->curr->se;
8868 for_each_sched_entity(se) {
8869 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8871 set_next_entity(cfs_rq, se);
8872 /* ensure bandwidth has been allocated on our new cfs_rq */
8873 account_cfs_rq_runtime(cfs_rq, 0);
8877 void init_cfs_rq(struct cfs_rq *cfs_rq)
8879 cfs_rq->tasks_timeline = RB_ROOT;
8880 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8881 #ifndef CONFIG_64BIT
8882 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8885 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8886 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8890 #ifdef CONFIG_FAIR_GROUP_SCHED
8891 static void task_move_group_fair(struct task_struct *p)
8893 detach_task_cfs_rq(p);
8894 set_task_rq(p, task_cpu(p));
8897 /* Tell se's cfs_rq has been changed -- migrated */
8898 p->se.avg.last_update_time = 0;
8900 attach_task_cfs_rq(p);
8903 void free_fair_sched_group(struct task_group *tg)
8907 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8909 for_each_possible_cpu(i) {
8911 kfree(tg->cfs_rq[i]);
8914 remove_entity_load_avg(tg->se[i]);
8923 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8925 struct cfs_rq *cfs_rq;
8926 struct sched_entity *se;
8929 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8932 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8936 tg->shares = NICE_0_LOAD;
8938 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8940 for_each_possible_cpu(i) {
8941 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8942 GFP_KERNEL, cpu_to_node(i));
8946 se = kzalloc_node(sizeof(struct sched_entity),
8947 GFP_KERNEL, cpu_to_node(i));
8951 init_cfs_rq(cfs_rq);
8952 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8953 init_entity_runnable_average(se);
8964 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8966 struct rq *rq = cpu_rq(cpu);
8967 unsigned long flags;
8970 * Only empty task groups can be destroyed; so we can speculatively
8971 * check on_list without danger of it being re-added.
8973 if (!tg->cfs_rq[cpu]->on_list)
8976 raw_spin_lock_irqsave(&rq->lock, flags);
8977 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8978 raw_spin_unlock_irqrestore(&rq->lock, flags);
8981 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
8982 struct sched_entity *se, int cpu,
8983 struct sched_entity *parent)
8985 struct rq *rq = cpu_rq(cpu);
8989 init_cfs_rq_runtime(cfs_rq);
8991 tg->cfs_rq[cpu] = cfs_rq;
8994 /* se could be NULL for root_task_group */
8999 se->cfs_rq = &rq->cfs;
9002 se->cfs_rq = parent->my_q;
9003 se->depth = parent->depth + 1;
9007 /* guarantee group entities always have weight */
9008 update_load_set(&se->load, NICE_0_LOAD);
9009 se->parent = parent;
9012 static DEFINE_MUTEX(shares_mutex);
9014 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
9017 unsigned long flags;
9020 * We can't change the weight of the root cgroup.
9025 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
9027 mutex_lock(&shares_mutex);
9028 if (tg->shares == shares)
9031 tg->shares = shares;
9032 for_each_possible_cpu(i) {
9033 struct rq *rq = cpu_rq(i);
9034 struct sched_entity *se;
9037 /* Propagate contribution to hierarchy */
9038 raw_spin_lock_irqsave(&rq->lock, flags);
9040 /* Possible calls to update_curr() need rq clock */
9041 update_rq_clock(rq);
9042 for_each_sched_entity(se)
9043 update_cfs_shares(group_cfs_rq(se));
9044 raw_spin_unlock_irqrestore(&rq->lock, flags);
9048 mutex_unlock(&shares_mutex);
9051 #else /* CONFIG_FAIR_GROUP_SCHED */
9053 void free_fair_sched_group(struct task_group *tg) { }
9055 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9060 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
9062 #endif /* CONFIG_FAIR_GROUP_SCHED */
9065 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9067 struct sched_entity *se = &task->se;
9068 unsigned int rr_interval = 0;
9071 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
9074 if (rq->cfs.load.weight)
9075 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9081 * All the scheduling class methods:
9083 const struct sched_class fair_sched_class = {
9084 .next = &idle_sched_class,
9085 .enqueue_task = enqueue_task_fair,
9086 .dequeue_task = dequeue_task_fair,
9087 .yield_task = yield_task_fair,
9088 .yield_to_task = yield_to_task_fair,
9090 .check_preempt_curr = check_preempt_wakeup,
9092 .pick_next_task = pick_next_task_fair,
9093 .put_prev_task = put_prev_task_fair,
9096 .select_task_rq = select_task_rq_fair,
9097 .migrate_task_rq = migrate_task_rq_fair,
9099 .rq_online = rq_online_fair,
9100 .rq_offline = rq_offline_fair,
9102 .task_waking = task_waking_fair,
9103 .task_dead = task_dead_fair,
9104 .set_cpus_allowed = set_cpus_allowed_common,
9107 .set_curr_task = set_curr_task_fair,
9108 .task_tick = task_tick_fair,
9109 .task_fork = task_fork_fair,
9111 .prio_changed = prio_changed_fair,
9112 .switched_from = switched_from_fair,
9113 .switched_to = switched_to_fair,
9115 .get_rr_interval = get_rr_interval_fair,
9117 .update_curr = update_curr_fair,
9119 #ifdef CONFIG_FAIR_GROUP_SCHED
9120 .task_move_group = task_move_group_fair,
9124 #ifdef CONFIG_SCHED_DEBUG
9125 void print_cfs_stats(struct seq_file *m, int cpu)
9127 struct cfs_rq *cfs_rq;
9130 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
9131 print_cfs_rq(m, cpu, cfs_rq);
9135 #ifdef CONFIG_NUMA_BALANCING
9136 void show_numa_stats(struct task_struct *p, struct seq_file *m)
9139 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
9141 for_each_online_node(node) {
9142 if (p->numa_faults) {
9143 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
9144 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
9146 if (p->numa_group) {
9147 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
9148 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
9150 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
9153 #endif /* CONFIG_NUMA_BALANCING */
9154 #endif /* CONFIG_SCHED_DEBUG */
9156 __init void init_sched_fair_class(void)
9159 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9161 #ifdef CONFIG_NO_HZ_COMMON
9162 nohz.next_balance = jiffies;
9163 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9164 cpu_notifier(sched_ilb_notifier, 0);