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 */
692 void init_entity_runnable_average(struct sched_entity *se)
698 * Update the current task's runtime statistics.
700 static void update_curr(struct cfs_rq *cfs_rq)
702 struct sched_entity *curr = cfs_rq->curr;
703 u64 now = rq_clock_task(rq_of(cfs_rq));
709 delta_exec = now - curr->exec_start;
710 if (unlikely((s64)delta_exec <= 0))
713 curr->exec_start = now;
715 schedstat_set(curr->statistics.exec_max,
716 max(delta_exec, curr->statistics.exec_max));
718 curr->sum_exec_runtime += delta_exec;
719 schedstat_add(cfs_rq, exec_clock, delta_exec);
721 curr->vruntime += calc_delta_fair(delta_exec, curr);
722 update_min_vruntime(cfs_rq);
724 if (entity_is_task(curr)) {
725 struct task_struct *curtask = task_of(curr);
727 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
728 cpuacct_charge(curtask, delta_exec);
729 account_group_exec_runtime(curtask, delta_exec);
732 account_cfs_rq_runtime(cfs_rq, delta_exec);
735 static void update_curr_fair(struct rq *rq)
737 update_curr(cfs_rq_of(&rq->curr->se));
741 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
743 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
747 * Task is being enqueued - update stats:
749 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
752 * Are we enqueueing a waiting task? (for current tasks
753 * a dequeue/enqueue event is a NOP)
755 if (se != cfs_rq->curr)
756 update_stats_wait_start(cfs_rq, se);
760 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
762 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
763 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
764 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
765 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
766 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
767 #ifdef CONFIG_SCHEDSTATS
768 if (entity_is_task(se)) {
769 trace_sched_stat_wait(task_of(se),
770 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
773 schedstat_set(se->statistics.wait_start, 0);
777 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
780 * Mark the end of the wait period if dequeueing a
783 if (se != cfs_rq->curr)
784 update_stats_wait_end(cfs_rq, se);
788 * We are picking a new current task - update its stats:
791 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
794 * We are starting a new run period:
796 se->exec_start = rq_clock_task(rq_of(cfs_rq));
799 /**************************************************
800 * Scheduling class queueing methods:
803 #ifdef CONFIG_NUMA_BALANCING
805 * Approximate time to scan a full NUMA task in ms. The task scan period is
806 * calculated based on the tasks virtual memory size and
807 * numa_balancing_scan_size.
809 unsigned int sysctl_numa_balancing_scan_period_min = 1000;
810 unsigned int sysctl_numa_balancing_scan_period_max = 60000;
812 /* Portion of address space to scan in MB */
813 unsigned int sysctl_numa_balancing_scan_size = 256;
815 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
816 unsigned int sysctl_numa_balancing_scan_delay = 1000;
818 static unsigned int task_nr_scan_windows(struct task_struct *p)
820 unsigned long rss = 0;
821 unsigned long nr_scan_pages;
824 * Calculations based on RSS as non-present and empty pages are skipped
825 * by the PTE scanner and NUMA hinting faults should be trapped based
828 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
829 rss = get_mm_rss(p->mm);
833 rss = round_up(rss, nr_scan_pages);
834 return rss / nr_scan_pages;
837 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
838 #define MAX_SCAN_WINDOW 2560
840 static unsigned int task_scan_min(struct task_struct *p)
842 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
843 unsigned int scan, floor;
844 unsigned int windows = 1;
846 if (scan_size < MAX_SCAN_WINDOW)
847 windows = MAX_SCAN_WINDOW / scan_size;
848 floor = 1000 / windows;
850 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
851 return max_t(unsigned int, floor, scan);
854 static unsigned int task_scan_max(struct task_struct *p)
856 unsigned int smin = task_scan_min(p);
859 /* Watch for min being lower than max due to floor calculations */
860 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
861 return max(smin, smax);
864 static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
866 rq->nr_numa_running += (p->numa_preferred_nid != -1);
867 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
870 static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
872 rq->nr_numa_running -= (p->numa_preferred_nid != -1);
873 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
879 spinlock_t lock; /* nr_tasks, tasks */
884 nodemask_t active_nodes;
885 unsigned long total_faults;
887 * Faults_cpu is used to decide whether memory should move
888 * towards the CPU. As a consequence, these stats are weighted
889 * more by CPU use than by memory faults.
891 unsigned long *faults_cpu;
892 unsigned long faults[0];
895 /* Shared or private faults. */
896 #define NR_NUMA_HINT_FAULT_TYPES 2
898 /* Memory and CPU locality */
899 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
901 /* Averaged statistics, and temporary buffers. */
902 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
904 pid_t task_numa_group_id(struct task_struct *p)
906 return p->numa_group ? p->numa_group->gid : 0;
910 * The averaged statistics, shared & private, memory & cpu,
911 * occupy the first half of the array. The second half of the
912 * array is for current counters, which are averaged into the
913 * first set by task_numa_placement.
915 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
917 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
920 static inline unsigned long task_faults(struct task_struct *p, int nid)
925 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
926 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
929 static inline unsigned long group_faults(struct task_struct *p, int nid)
934 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
935 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
938 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
940 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
941 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
944 /* Handle placement on systems where not all nodes are directly connected. */
945 static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
946 int maxdist, bool task)
948 unsigned long score = 0;
952 * All nodes are directly connected, and the same distance
953 * from each other. No need for fancy placement algorithms.
955 if (sched_numa_topology_type == NUMA_DIRECT)
959 * This code is called for each node, introducing N^2 complexity,
960 * which should be ok given the number of nodes rarely exceeds 8.
962 for_each_online_node(node) {
963 unsigned long faults;
964 int dist = node_distance(nid, node);
967 * The furthest away nodes in the system are not interesting
968 * for placement; nid was already counted.
970 if (dist == sched_max_numa_distance || node == nid)
974 * On systems with a backplane NUMA topology, compare groups
975 * of nodes, and move tasks towards the group with the most
976 * memory accesses. When comparing two nodes at distance
977 * "hoplimit", only nodes closer by than "hoplimit" are part
978 * of each group. Skip other nodes.
980 if (sched_numa_topology_type == NUMA_BACKPLANE &&
984 /* Add up the faults from nearby nodes. */
986 faults = task_faults(p, node);
988 faults = group_faults(p, node);
991 * On systems with a glueless mesh NUMA topology, there are
992 * no fixed "groups of nodes". Instead, nodes that are not
993 * directly connected bounce traffic through intermediate
994 * nodes; a numa_group can occupy any set of nodes.
995 * The further away a node is, the less the faults count.
996 * This seems to result in good task placement.
998 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
999 faults *= (sched_max_numa_distance - dist);
1000 faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
1010 * These return the fraction of accesses done by a particular task, or
1011 * task group, on a particular numa node. The group weight is given a
1012 * larger multiplier, in order to group tasks together that are almost
1013 * evenly spread out between numa nodes.
1015 static inline unsigned long task_weight(struct task_struct *p, int nid,
1018 unsigned long faults, total_faults;
1020 if (!p->numa_faults)
1023 total_faults = p->total_numa_faults;
1028 faults = task_faults(p, nid);
1029 faults += score_nearby_nodes(p, nid, dist, true);
1031 return 1000 * faults / total_faults;
1034 static inline unsigned long group_weight(struct task_struct *p, int nid,
1037 unsigned long faults, total_faults;
1042 total_faults = p->numa_group->total_faults;
1047 faults = group_faults(p, nid);
1048 faults += score_nearby_nodes(p, nid, dist, false);
1050 return 1000 * faults / total_faults;
1053 bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
1054 int src_nid, int dst_cpu)
1056 struct numa_group *ng = p->numa_group;
1057 int dst_nid = cpu_to_node(dst_cpu);
1058 int last_cpupid, this_cpupid;
1060 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1063 * Multi-stage node selection is used in conjunction with a periodic
1064 * migration fault to build a temporal task<->page relation. By using
1065 * a two-stage filter we remove short/unlikely relations.
1067 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1068 * a task's usage of a particular page (n_p) per total usage of this
1069 * page (n_t) (in a given time-span) to a probability.
1071 * Our periodic faults will sample this probability and getting the
1072 * same result twice in a row, given these samples are fully
1073 * independent, is then given by P(n)^2, provided our sample period
1074 * is sufficiently short compared to the usage pattern.
1076 * This quadric squishes small probabilities, making it less likely we
1077 * act on an unlikely task<->page relation.
1079 last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
1080 if (!cpupid_pid_unset(last_cpupid) &&
1081 cpupid_to_nid(last_cpupid) != dst_nid)
1084 /* Always allow migrate on private faults */
1085 if (cpupid_match_pid(p, last_cpupid))
1088 /* A shared fault, but p->numa_group has not been set up yet. */
1093 * Do not migrate if the destination is not a node that
1094 * is actively used by this numa group.
1096 if (!node_isset(dst_nid, ng->active_nodes))
1100 * Source is a node that is not actively used by this
1101 * numa group, while the destination is. Migrate.
1103 if (!node_isset(src_nid, ng->active_nodes))
1107 * Both source and destination are nodes in active
1108 * use by this numa group. Maximize memory bandwidth
1109 * by migrating from more heavily used groups, to less
1110 * heavily used ones, spreading the load around.
1111 * Use a 1/4 hysteresis to avoid spurious page movement.
1113 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
1116 static unsigned long weighted_cpuload(const int cpu);
1117 static unsigned long source_load(int cpu, int type);
1118 static unsigned long target_load(int cpu, int type);
1119 static unsigned long capacity_of(int cpu);
1120 static long effective_load(struct task_group *tg, int cpu, long wl, long wg);
1122 /* Cached statistics for all CPUs within a node */
1124 unsigned long nr_running;
1127 /* Total compute capacity of CPUs on a node */
1128 unsigned long compute_capacity;
1130 /* Approximate capacity in terms of runnable tasks on a node */
1131 unsigned long task_capacity;
1132 int has_free_capacity;
1136 * XXX borrowed from update_sg_lb_stats
1138 static void update_numa_stats(struct numa_stats *ns, int nid)
1140 int smt, cpu, cpus = 0;
1141 unsigned long capacity;
1143 memset(ns, 0, sizeof(*ns));
1144 for_each_cpu(cpu, cpumask_of_node(nid)) {
1145 struct rq *rq = cpu_rq(cpu);
1147 ns->nr_running += rq->nr_running;
1148 ns->load += weighted_cpuload(cpu);
1149 ns->compute_capacity += capacity_of(cpu);
1155 * If we raced with hotplug and there are no CPUs left in our mask
1156 * the @ns structure is NULL'ed and task_numa_compare() will
1157 * not find this node attractive.
1159 * We'll either bail at !has_free_capacity, or we'll detect a huge
1160 * imbalance and bail there.
1165 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1166 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
1167 capacity = cpus / smt; /* cores */
1169 ns->task_capacity = min_t(unsigned, capacity,
1170 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1171 ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1174 struct task_numa_env {
1175 struct task_struct *p;
1177 int src_cpu, src_nid;
1178 int dst_cpu, dst_nid;
1180 struct numa_stats src_stats, dst_stats;
1185 struct task_struct *best_task;
1190 static void task_numa_assign(struct task_numa_env *env,
1191 struct task_struct *p, long imp)
1194 put_task_struct(env->best_task);
1199 env->best_imp = imp;
1200 env->best_cpu = env->dst_cpu;
1203 static bool load_too_imbalanced(long src_load, long dst_load,
1204 struct task_numa_env *env)
1207 long orig_src_load, orig_dst_load;
1208 long src_capacity, dst_capacity;
1211 * The load is corrected for the CPU capacity available on each node.
1214 * ------------ vs ---------
1215 * src_capacity dst_capacity
1217 src_capacity = env->src_stats.compute_capacity;
1218 dst_capacity = env->dst_stats.compute_capacity;
1220 /* We care about the slope of the imbalance, not the direction. */
1221 if (dst_load < src_load)
1222 swap(dst_load, src_load);
1224 /* Is the difference below the threshold? */
1225 imb = dst_load * src_capacity * 100 -
1226 src_load * dst_capacity * env->imbalance_pct;
1231 * The imbalance is above the allowed threshold.
1232 * Compare it with the old imbalance.
1234 orig_src_load = env->src_stats.load;
1235 orig_dst_load = env->dst_stats.load;
1237 if (orig_dst_load < orig_src_load)
1238 swap(orig_dst_load, orig_src_load);
1240 old_imb = orig_dst_load * src_capacity * 100 -
1241 orig_src_load * dst_capacity * env->imbalance_pct;
1243 /* Would this change make things worse? */
1244 return (imb > old_imb);
1248 * This checks if the overall compute and NUMA accesses of the system would
1249 * be improved if the source tasks was migrated to the target dst_cpu taking
1250 * into account that it might be best if task running on the dst_cpu should
1251 * be exchanged with the source task
1253 static void task_numa_compare(struct task_numa_env *env,
1254 long taskimp, long groupimp)
1256 struct rq *src_rq = cpu_rq(env->src_cpu);
1257 struct rq *dst_rq = cpu_rq(env->dst_cpu);
1258 struct task_struct *cur;
1259 long src_load, dst_load;
1261 long imp = env->p->numa_group ? groupimp : taskimp;
1263 int dist = env->dist;
1267 raw_spin_lock_irq(&dst_rq->lock);
1270 * No need to move the exiting task, and this ensures that ->curr
1271 * wasn't reaped and thus get_task_struct() in task_numa_assign()
1272 * is safe under RCU read lock.
1273 * Note that rcu_read_lock() itself can't protect from the final
1274 * put_task_struct() after the last schedule().
1276 if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1278 raw_spin_unlock_irq(&dst_rq->lock);
1281 * Because we have preemption enabled we can get migrated around and
1282 * end try selecting ourselves (current == env->p) as a swap candidate.
1288 * "imp" is the fault differential for the source task between the
1289 * source and destination node. Calculate the total differential for
1290 * the source task and potential destination task. The more negative
1291 * the value is, the more rmeote accesses that would be expected to
1292 * be incurred if the tasks were swapped.
1295 /* Skip this swap candidate if cannot move to the source cpu */
1296 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
1300 * If dst and source tasks are in the same NUMA group, or not
1301 * in any group then look only at task weights.
1303 if (cur->numa_group == env->p->numa_group) {
1304 imp = taskimp + task_weight(cur, env->src_nid, dist) -
1305 task_weight(cur, env->dst_nid, dist);
1307 * Add some hysteresis to prevent swapping the
1308 * tasks within a group over tiny differences.
1310 if (cur->numa_group)
1314 * Compare the group weights. If a task is all by
1315 * itself (not part of a group), use the task weight
1318 if (cur->numa_group)
1319 imp += group_weight(cur, env->src_nid, dist) -
1320 group_weight(cur, env->dst_nid, dist);
1322 imp += task_weight(cur, env->src_nid, dist) -
1323 task_weight(cur, env->dst_nid, dist);
1327 if (imp <= env->best_imp && moveimp <= env->best_imp)
1331 /* Is there capacity at our destination? */
1332 if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1333 !env->dst_stats.has_free_capacity)
1339 /* Balance doesn't matter much if we're running a task per cpu */
1340 if (imp > env->best_imp && src_rq->nr_running == 1 &&
1341 dst_rq->nr_running == 1)
1345 * In the overloaded case, try and keep the load balanced.
1348 load = task_h_load(env->p);
1349 dst_load = env->dst_stats.load + load;
1350 src_load = env->src_stats.load - load;
1352 if (moveimp > imp && moveimp > env->best_imp) {
1354 * If the improvement from just moving env->p direction is
1355 * better than swapping tasks around, check if a move is
1356 * possible. Store a slightly smaller score than moveimp,
1357 * so an actually idle CPU will win.
1359 if (!load_too_imbalanced(src_load, dst_load, env)) {
1366 if (imp <= env->best_imp)
1370 load = task_h_load(cur);
1375 if (load_too_imbalanced(src_load, dst_load, env))
1379 * One idle CPU per node is evaluated for a task numa move.
1380 * Call select_idle_sibling to maybe find a better one.
1383 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);
1386 task_numa_assign(env, cur, imp);
1391 static void task_numa_find_cpu(struct task_numa_env *env,
1392 long taskimp, long groupimp)
1396 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
1397 /* Skip this CPU if the source task cannot migrate */
1398 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
1402 task_numa_compare(env, taskimp, groupimp);
1406 /* Only move tasks to a NUMA node less busy than the current node. */
1407 static bool numa_has_capacity(struct task_numa_env *env)
1409 struct numa_stats *src = &env->src_stats;
1410 struct numa_stats *dst = &env->dst_stats;
1412 if (src->has_free_capacity && !dst->has_free_capacity)
1416 * Only consider a task move if the source has a higher load
1417 * than the destination, corrected for CPU capacity on each node.
1419 * src->load dst->load
1420 * --------------------- vs ---------------------
1421 * src->compute_capacity dst->compute_capacity
1423 if (src->load * dst->compute_capacity * env->imbalance_pct >
1425 dst->load * src->compute_capacity * 100)
1431 static int task_numa_migrate(struct task_struct *p)
1433 struct task_numa_env env = {
1436 .src_cpu = task_cpu(p),
1437 .src_nid = task_node(p),
1439 .imbalance_pct = 112,
1445 struct sched_domain *sd;
1446 unsigned long taskweight, groupweight;
1448 long taskimp, groupimp;
1451 * Pick the lowest SD_NUMA domain, as that would have the smallest
1452 * imbalance and would be the first to start moving tasks about.
1454 * And we want to avoid any moving of tasks about, as that would create
1455 * random movement of tasks -- counter the numa conditions we're trying
1459 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1461 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1465 * Cpusets can break the scheduler domain tree into smaller
1466 * balance domains, some of which do not cross NUMA boundaries.
1467 * Tasks that are "trapped" in such domains cannot be migrated
1468 * elsewhere, so there is no point in (re)trying.
1470 if (unlikely(!sd)) {
1471 p->numa_preferred_nid = task_node(p);
1475 env.dst_nid = p->numa_preferred_nid;
1476 dist = env.dist = node_distance(env.src_nid, env.dst_nid);
1477 taskweight = task_weight(p, env.src_nid, dist);
1478 groupweight = group_weight(p, env.src_nid, dist);
1479 update_numa_stats(&env.src_stats, env.src_nid);
1480 taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
1481 groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1482 update_numa_stats(&env.dst_stats, env.dst_nid);
1484 /* Try to find a spot on the preferred nid. */
1485 if (numa_has_capacity(&env))
1486 task_numa_find_cpu(&env, taskimp, groupimp);
1489 * Look at other nodes in these cases:
1490 * - there is no space available on the preferred_nid
1491 * - the task is part of a numa_group that is interleaved across
1492 * multiple NUMA nodes; in order to better consolidate the group,
1493 * we need to check other locations.
1495 if (env.best_cpu == -1 || (p->numa_group &&
1496 nodes_weight(p->numa_group->active_nodes) > 1)) {
1497 for_each_online_node(nid) {
1498 if (nid == env.src_nid || nid == p->numa_preferred_nid)
1501 dist = node_distance(env.src_nid, env.dst_nid);
1502 if (sched_numa_topology_type == NUMA_BACKPLANE &&
1504 taskweight = task_weight(p, env.src_nid, dist);
1505 groupweight = group_weight(p, env.src_nid, dist);
1508 /* Only consider nodes where both task and groups benefit */
1509 taskimp = task_weight(p, nid, dist) - taskweight;
1510 groupimp = group_weight(p, nid, dist) - groupweight;
1511 if (taskimp < 0 && groupimp < 0)
1516 update_numa_stats(&env.dst_stats, env.dst_nid);
1517 if (numa_has_capacity(&env))
1518 task_numa_find_cpu(&env, taskimp, groupimp);
1523 * If the task is part of a workload that spans multiple NUMA nodes,
1524 * and is migrating into one of the workload's active nodes, remember
1525 * this node as the task's preferred numa node, so the workload can
1527 * A task that migrated to a second choice node will be better off
1528 * trying for a better one later. Do not set the preferred node here.
1530 if (p->numa_group) {
1531 if (env.best_cpu == -1)
1536 if (node_isset(nid, p->numa_group->active_nodes))
1537 sched_setnuma(p, env.dst_nid);
1540 /* No better CPU than the current one was found. */
1541 if (env.best_cpu == -1)
1545 * Reset the scan period if the task is being rescheduled on an
1546 * alternative node to recheck if the tasks is now properly placed.
1548 p->numa_scan_period = task_scan_min(p);
1550 if (env.best_task == NULL) {
1551 ret = migrate_task_to(p, env.best_cpu);
1553 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1557 ret = migrate_swap(p, env.best_task);
1559 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1560 put_task_struct(env.best_task);
1564 /* Attempt to migrate a task to a CPU on the preferred node. */
1565 static void numa_migrate_preferred(struct task_struct *p)
1567 unsigned long interval = HZ;
1569 /* This task has no NUMA fault statistics yet */
1570 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1573 /* Periodically retry migrating the task to the preferred node */
1574 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1575 p->numa_migrate_retry = jiffies + interval;
1577 /* Success if task is already running on preferred CPU */
1578 if (task_node(p) == p->numa_preferred_nid)
1581 /* Otherwise, try migrate to a CPU on the preferred node */
1582 task_numa_migrate(p);
1586 * Find the nodes on which the workload is actively running. We do this by
1587 * tracking the nodes from which NUMA hinting faults are triggered. This can
1588 * be different from the set of nodes where the workload's memory is currently
1591 * The bitmask is used to make smarter decisions on when to do NUMA page
1592 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
1593 * are added when they cause over 6/16 of the maximum number of faults, but
1594 * only removed when they drop below 3/16.
1596 static void update_numa_active_node_mask(struct numa_group *numa_group)
1598 unsigned long faults, max_faults = 0;
1601 for_each_online_node(nid) {
1602 faults = group_faults_cpu(numa_group, nid);
1603 if (faults > max_faults)
1604 max_faults = faults;
1607 for_each_online_node(nid) {
1608 faults = group_faults_cpu(numa_group, nid);
1609 if (!node_isset(nid, numa_group->active_nodes)) {
1610 if (faults > max_faults * 6 / 16)
1611 node_set(nid, numa_group->active_nodes);
1612 } else if (faults < max_faults * 3 / 16)
1613 node_clear(nid, numa_group->active_nodes);
1618 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1619 * increments. The more local the fault statistics are, the higher the scan
1620 * period will be for the next scan window. If local/(local+remote) ratio is
1621 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1622 * the scan period will decrease. Aim for 70% local accesses.
1624 #define NUMA_PERIOD_SLOTS 10
1625 #define NUMA_PERIOD_THRESHOLD 7
1628 * Increase the scan period (slow down scanning) if the majority of
1629 * our memory is already on our local node, or if the majority of
1630 * the page accesses are shared with other processes.
1631 * Otherwise, decrease the scan period.
1633 static void update_task_scan_period(struct task_struct *p,
1634 unsigned long shared, unsigned long private)
1636 unsigned int period_slot;
1640 unsigned long remote = p->numa_faults_locality[0];
1641 unsigned long local = p->numa_faults_locality[1];
1644 * If there were no record hinting faults then either the task is
1645 * completely idle or all activity is areas that are not of interest
1646 * to automatic numa balancing. Related to that, if there were failed
1647 * migration then it implies we are migrating too quickly or the local
1648 * node is overloaded. In either case, scan slower
1650 if (local + shared == 0 || p->numa_faults_locality[2]) {
1651 p->numa_scan_period = min(p->numa_scan_period_max,
1652 p->numa_scan_period << 1);
1654 p->mm->numa_next_scan = jiffies +
1655 msecs_to_jiffies(p->numa_scan_period);
1661 * Prepare to scale scan period relative to the current period.
1662 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1663 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1664 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1666 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
1667 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
1668 if (ratio >= NUMA_PERIOD_THRESHOLD) {
1669 int slot = ratio - NUMA_PERIOD_THRESHOLD;
1672 diff = slot * period_slot;
1674 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1677 * Scale scan rate increases based on sharing. There is an
1678 * inverse relationship between the degree of sharing and
1679 * the adjustment made to the scanning period. Broadly
1680 * speaking the intent is that there is little point
1681 * scanning faster if shared accesses dominate as it may
1682 * simply bounce migrations uselessly
1684 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1685 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
1688 p->numa_scan_period = clamp(p->numa_scan_period + diff,
1689 task_scan_min(p), task_scan_max(p));
1690 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1694 * Get the fraction of time the task has been running since the last
1695 * NUMA placement cycle. The scheduler keeps similar statistics, but
1696 * decays those on a 32ms period, which is orders of magnitude off
1697 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1698 * stats only if the task is so new there are no NUMA statistics yet.
1700 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
1702 u64 runtime, delta, now;
1703 /* Use the start of this time slice to avoid calculations. */
1704 now = p->se.exec_start;
1705 runtime = p->se.sum_exec_runtime;
1707 if (p->last_task_numa_placement) {
1708 delta = runtime - p->last_sum_exec_runtime;
1709 *period = now - p->last_task_numa_placement;
1711 delta = p->se.avg.load_sum / p->se.load.weight;
1712 *period = LOAD_AVG_MAX;
1715 p->last_sum_exec_runtime = runtime;
1716 p->last_task_numa_placement = now;
1722 * Determine the preferred nid for a task in a numa_group. This needs to
1723 * be done in a way that produces consistent results with group_weight,
1724 * otherwise workloads might not converge.
1726 static int preferred_group_nid(struct task_struct *p, int nid)
1731 /* Direct connections between all NUMA nodes. */
1732 if (sched_numa_topology_type == NUMA_DIRECT)
1736 * On a system with glueless mesh NUMA topology, group_weight
1737 * scores nodes according to the number of NUMA hinting faults on
1738 * both the node itself, and on nearby nodes.
1740 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
1741 unsigned long score, max_score = 0;
1742 int node, max_node = nid;
1744 dist = sched_max_numa_distance;
1746 for_each_online_node(node) {
1747 score = group_weight(p, node, dist);
1748 if (score > max_score) {
1757 * Finding the preferred nid in a system with NUMA backplane
1758 * interconnect topology is more involved. The goal is to locate
1759 * tasks from numa_groups near each other in the system, and
1760 * untangle workloads from different sides of the system. This requires
1761 * searching down the hierarchy of node groups, recursively searching
1762 * inside the highest scoring group of nodes. The nodemask tricks
1763 * keep the complexity of the search down.
1765 nodes = node_online_map;
1766 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
1767 unsigned long max_faults = 0;
1768 nodemask_t max_group = NODE_MASK_NONE;
1771 /* Are there nodes at this distance from each other? */
1772 if (!find_numa_distance(dist))
1775 for_each_node_mask(a, nodes) {
1776 unsigned long faults = 0;
1777 nodemask_t this_group;
1778 nodes_clear(this_group);
1780 /* Sum group's NUMA faults; includes a==b case. */
1781 for_each_node_mask(b, nodes) {
1782 if (node_distance(a, b) < dist) {
1783 faults += group_faults(p, b);
1784 node_set(b, this_group);
1785 node_clear(b, nodes);
1789 /* Remember the top group. */
1790 if (faults > max_faults) {
1791 max_faults = faults;
1792 max_group = this_group;
1794 * subtle: at the smallest distance there is
1795 * just one node left in each "group", the
1796 * winner is the preferred nid.
1801 /* Next round, evaluate the nodes within max_group. */
1809 static void task_numa_placement(struct task_struct *p)
1811 int seq, nid, max_nid = -1, max_group_nid = -1;
1812 unsigned long max_faults = 0, max_group_faults = 0;
1813 unsigned long fault_types[2] = { 0, 0 };
1814 unsigned long total_faults;
1815 u64 runtime, period;
1816 spinlock_t *group_lock = NULL;
1819 * The p->mm->numa_scan_seq field gets updated without
1820 * exclusive access. Use READ_ONCE() here to ensure
1821 * that the field is read in a single access:
1823 seq = READ_ONCE(p->mm->numa_scan_seq);
1824 if (p->numa_scan_seq == seq)
1826 p->numa_scan_seq = seq;
1827 p->numa_scan_period_max = task_scan_max(p);
1829 total_faults = p->numa_faults_locality[0] +
1830 p->numa_faults_locality[1];
1831 runtime = numa_get_avg_runtime(p, &period);
1833 /* If the task is part of a group prevent parallel updates to group stats */
1834 if (p->numa_group) {
1835 group_lock = &p->numa_group->lock;
1836 spin_lock_irq(group_lock);
1839 /* Find the node with the highest number of faults */
1840 for_each_online_node(nid) {
1841 /* Keep track of the offsets in numa_faults array */
1842 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1843 unsigned long faults = 0, group_faults = 0;
1846 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1847 long diff, f_diff, f_weight;
1849 mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
1850 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
1851 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
1852 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1854 /* Decay existing window, copy faults since last scan */
1855 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
1856 fault_types[priv] += p->numa_faults[membuf_idx];
1857 p->numa_faults[membuf_idx] = 0;
1860 * Normalize the faults_from, so all tasks in a group
1861 * count according to CPU use, instead of by the raw
1862 * number of faults. Tasks with little runtime have
1863 * little over-all impact on throughput, and thus their
1864 * faults are less important.
1866 f_weight = div64_u64(runtime << 16, period + 1);
1867 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1869 f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
1870 p->numa_faults[cpubuf_idx] = 0;
1872 p->numa_faults[mem_idx] += diff;
1873 p->numa_faults[cpu_idx] += f_diff;
1874 faults += p->numa_faults[mem_idx];
1875 p->total_numa_faults += diff;
1876 if (p->numa_group) {
1878 * safe because we can only change our own group
1880 * mem_idx represents the offset for a given
1881 * nid and priv in a specific region because it
1882 * is at the beginning of the numa_faults array.
1884 p->numa_group->faults[mem_idx] += diff;
1885 p->numa_group->faults_cpu[mem_idx] += f_diff;
1886 p->numa_group->total_faults += diff;
1887 group_faults += p->numa_group->faults[mem_idx];
1891 if (faults > max_faults) {
1892 max_faults = faults;
1896 if (group_faults > max_group_faults) {
1897 max_group_faults = group_faults;
1898 max_group_nid = nid;
1902 update_task_scan_period(p, fault_types[0], fault_types[1]);
1904 if (p->numa_group) {
1905 update_numa_active_node_mask(p->numa_group);
1906 spin_unlock_irq(group_lock);
1907 max_nid = preferred_group_nid(p, max_group_nid);
1911 /* Set the new preferred node */
1912 if (max_nid != p->numa_preferred_nid)
1913 sched_setnuma(p, max_nid);
1915 if (task_node(p) != p->numa_preferred_nid)
1916 numa_migrate_preferred(p);
1920 static inline int get_numa_group(struct numa_group *grp)
1922 return atomic_inc_not_zero(&grp->refcount);
1925 static inline void put_numa_group(struct numa_group *grp)
1927 if (atomic_dec_and_test(&grp->refcount))
1928 kfree_rcu(grp, rcu);
1931 static void task_numa_group(struct task_struct *p, int cpupid, int flags,
1934 struct numa_group *grp, *my_grp;
1935 struct task_struct *tsk;
1937 int cpu = cpupid_to_cpu(cpupid);
1940 if (unlikely(!p->numa_group)) {
1941 unsigned int size = sizeof(struct numa_group) +
1942 4*nr_node_ids*sizeof(unsigned long);
1944 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
1948 atomic_set(&grp->refcount, 1);
1949 spin_lock_init(&grp->lock);
1951 /* Second half of the array tracks nids where faults happen */
1952 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
1955 node_set(task_node(current), grp->active_nodes);
1957 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1958 grp->faults[i] = p->numa_faults[i];
1960 grp->total_faults = p->total_numa_faults;
1963 rcu_assign_pointer(p->numa_group, grp);
1967 tsk = READ_ONCE(cpu_rq(cpu)->curr);
1969 if (!cpupid_match_pid(tsk, cpupid))
1972 grp = rcu_dereference(tsk->numa_group);
1976 my_grp = p->numa_group;
1981 * Only join the other group if its bigger; if we're the bigger group,
1982 * the other task will join us.
1984 if (my_grp->nr_tasks > grp->nr_tasks)
1988 * Tie-break on the grp address.
1990 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1993 /* Always join threads in the same process. */
1994 if (tsk->mm == current->mm)
1997 /* Simple filter to avoid false positives due to PID collisions */
1998 if (flags & TNF_SHARED)
2001 /* Update priv based on whether false sharing was detected */
2004 if (join && !get_numa_group(grp))
2012 BUG_ON(irqs_disabled());
2013 double_lock_irq(&my_grp->lock, &grp->lock);
2015 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2016 my_grp->faults[i] -= p->numa_faults[i];
2017 grp->faults[i] += p->numa_faults[i];
2019 my_grp->total_faults -= p->total_numa_faults;
2020 grp->total_faults += p->total_numa_faults;
2025 spin_unlock(&my_grp->lock);
2026 spin_unlock_irq(&grp->lock);
2028 rcu_assign_pointer(p->numa_group, grp);
2030 put_numa_group(my_grp);
2038 void task_numa_free(struct task_struct *p)
2040 struct numa_group *grp = p->numa_group;
2041 void *numa_faults = p->numa_faults;
2042 unsigned long flags;
2046 spin_lock_irqsave(&grp->lock, flags);
2047 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2048 grp->faults[i] -= p->numa_faults[i];
2049 grp->total_faults -= p->total_numa_faults;
2052 spin_unlock_irqrestore(&grp->lock, flags);
2053 RCU_INIT_POINTER(p->numa_group, NULL);
2054 put_numa_group(grp);
2057 p->numa_faults = NULL;
2062 * Got a PROT_NONE fault for a page on @node.
2064 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2066 struct task_struct *p = current;
2067 bool migrated = flags & TNF_MIGRATED;
2068 int cpu_node = task_node(current);
2069 int local = !!(flags & TNF_FAULT_LOCAL);
2072 if (!static_branch_likely(&sched_numa_balancing))
2075 /* for example, ksmd faulting in a user's mm */
2079 /* Allocate buffer to track faults on a per-node basis */
2080 if (unlikely(!p->numa_faults)) {
2081 int size = sizeof(*p->numa_faults) *
2082 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2084 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
2085 if (!p->numa_faults)
2088 p->total_numa_faults = 0;
2089 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2093 * First accesses are treated as private, otherwise consider accesses
2094 * to be private if the accessing pid has not changed
2096 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
2099 priv = cpupid_match_pid(p, last_cpupid);
2100 if (!priv && !(flags & TNF_NO_GROUP))
2101 task_numa_group(p, last_cpupid, flags, &priv);
2105 * If a workload spans multiple NUMA nodes, a shared fault that
2106 * occurs wholly within the set of nodes that the workload is
2107 * actively using should be counted as local. This allows the
2108 * scan rate to slow down when a workload has settled down.
2110 if (!priv && !local && p->numa_group &&
2111 node_isset(cpu_node, p->numa_group->active_nodes) &&
2112 node_isset(mem_node, p->numa_group->active_nodes))
2115 task_numa_placement(p);
2118 * Retry task to preferred node migration periodically, in case it
2119 * case it previously failed, or the scheduler moved us.
2121 if (time_after(jiffies, p->numa_migrate_retry))
2122 numa_migrate_preferred(p);
2125 p->numa_pages_migrated += pages;
2126 if (flags & TNF_MIGRATE_FAIL)
2127 p->numa_faults_locality[2] += pages;
2129 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
2130 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2131 p->numa_faults_locality[local] += pages;
2134 static void reset_ptenuma_scan(struct task_struct *p)
2137 * We only did a read acquisition of the mmap sem, so
2138 * p->mm->numa_scan_seq is written to without exclusive access
2139 * and the update is not guaranteed to be atomic. That's not
2140 * much of an issue though, since this is just used for
2141 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2142 * expensive, to avoid any form of compiler optimizations:
2144 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2145 p->mm->numa_scan_offset = 0;
2149 * The expensive part of numa migration is done from task_work context.
2150 * Triggered from task_tick_numa().
2152 void task_numa_work(struct callback_head *work)
2154 unsigned long migrate, next_scan, now = jiffies;
2155 struct task_struct *p = current;
2156 struct mm_struct *mm = p->mm;
2157 struct vm_area_struct *vma;
2158 unsigned long start, end;
2159 unsigned long nr_pte_updates = 0;
2160 long pages, virtpages;
2162 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
2164 work->next = work; /* protect against double add */
2166 * Who cares about NUMA placement when they're dying.
2168 * NOTE: make sure not to dereference p->mm before this check,
2169 * exit_task_work() happens _after_ exit_mm() so we could be called
2170 * without p->mm even though we still had it when we enqueued this
2173 if (p->flags & PF_EXITING)
2176 if (!mm->numa_next_scan) {
2177 mm->numa_next_scan = now +
2178 msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2182 * Enforce maximal scan/migration frequency..
2184 migrate = mm->numa_next_scan;
2185 if (time_before(now, migrate))
2188 if (p->numa_scan_period == 0) {
2189 p->numa_scan_period_max = task_scan_max(p);
2190 p->numa_scan_period = task_scan_min(p);
2193 next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2194 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
2198 * Delay this task enough that another task of this mm will likely win
2199 * the next time around.
2201 p->node_stamp += 2 * TICK_NSEC;
2203 start = mm->numa_scan_offset;
2204 pages = sysctl_numa_balancing_scan_size;
2205 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2206 virtpages = pages * 8; /* Scan up to this much virtual space */
2211 down_read(&mm->mmap_sem);
2212 vma = find_vma(mm, start);
2214 reset_ptenuma_scan(p);
2218 for (; vma; vma = vma->vm_next) {
2219 if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2220 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2225 * Shared library pages mapped by multiple processes are not
2226 * migrated as it is expected they are cache replicated. Avoid
2227 * hinting faults in read-only file-backed mappings or the vdso
2228 * as migrating the pages will be of marginal benefit.
2231 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
2235 * Skip inaccessible VMAs to avoid any confusion between
2236 * PROT_NONE and NUMA hinting ptes
2238 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
2242 start = max(start, vma->vm_start);
2243 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
2244 end = min(end, vma->vm_end);
2245 nr_pte_updates = change_prot_numa(vma, start, end);
2248 * Try to scan sysctl_numa_balancing_size worth of
2249 * hpages that have at least one present PTE that
2250 * is not already pte-numa. If the VMA contains
2251 * areas that are unused or already full of prot_numa
2252 * PTEs, scan up to virtpages, to skip through those
2256 pages -= (end - start) >> PAGE_SHIFT;
2257 virtpages -= (end - start) >> PAGE_SHIFT;
2260 if (pages <= 0 || virtpages <= 0)
2264 } while (end != vma->vm_end);
2269 * It is possible to reach the end of the VMA list but the last few
2270 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2271 * would find the !migratable VMA on the next scan but not reset the
2272 * scanner to the start so check it now.
2275 mm->numa_scan_offset = start;
2277 reset_ptenuma_scan(p);
2278 up_read(&mm->mmap_sem);
2282 * Drive the periodic memory faults..
2284 void task_tick_numa(struct rq *rq, struct task_struct *curr)
2286 struct callback_head *work = &curr->numa_work;
2290 * We don't care about NUMA placement if we don't have memory.
2292 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
2296 * Using runtime rather than walltime has the dual advantage that
2297 * we (mostly) drive the selection from busy threads and that the
2298 * task needs to have done some actual work before we bother with
2301 now = curr->se.sum_exec_runtime;
2302 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
2304 if (now > curr->node_stamp + period) {
2305 if (!curr->node_stamp)
2306 curr->numa_scan_period = task_scan_min(curr);
2307 curr->node_stamp += period;
2309 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
2310 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
2311 task_work_add(curr, work, true);
2316 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
2320 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
2324 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
2327 #endif /* CONFIG_NUMA_BALANCING */
2330 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2332 update_load_add(&cfs_rq->load, se->load.weight);
2333 if (!parent_entity(se))
2334 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2336 if (entity_is_task(se)) {
2337 struct rq *rq = rq_of(cfs_rq);
2339 account_numa_enqueue(rq, task_of(se));
2340 list_add(&se->group_node, &rq->cfs_tasks);
2343 cfs_rq->nr_running++;
2347 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
2349 update_load_sub(&cfs_rq->load, se->load.weight);
2350 if (!parent_entity(se))
2351 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2352 if (entity_is_task(se)) {
2353 account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2354 list_del_init(&se->group_node);
2356 cfs_rq->nr_running--;
2359 #ifdef CONFIG_FAIR_GROUP_SCHED
2361 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
2366 * Use this CPU's real-time load instead of the last load contribution
2367 * as the updating of the contribution is delayed, and we will use the
2368 * the real-time load to calc the share. See update_tg_load_avg().
2370 tg_weight = atomic_long_read(&tg->load_avg);
2371 tg_weight -= cfs_rq->tg_load_avg_contrib;
2372 tg_weight += cfs_rq->load.weight;
2377 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2379 long tg_weight, load, shares;
2381 tg_weight = calc_tg_weight(tg, cfs_rq);
2382 load = cfs_rq->load.weight;
2384 shares = (tg->shares * load);
2386 shares /= tg_weight;
2388 if (shares < MIN_SHARES)
2389 shares = MIN_SHARES;
2390 if (shares > tg->shares)
2391 shares = tg->shares;
2395 # else /* CONFIG_SMP */
2396 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2400 # endif /* CONFIG_SMP */
2401 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2402 unsigned long weight)
2405 /* commit outstanding execution time */
2406 if (cfs_rq->curr == se)
2407 update_curr(cfs_rq);
2408 account_entity_dequeue(cfs_rq, se);
2411 update_load_set(&se->load, weight);
2414 account_entity_enqueue(cfs_rq, se);
2417 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
2419 static void update_cfs_shares(struct cfs_rq *cfs_rq)
2421 struct task_group *tg;
2422 struct sched_entity *se;
2426 se = tg->se[cpu_of(rq_of(cfs_rq))];
2427 if (!se || throttled_hierarchy(cfs_rq))
2430 if (likely(se->load.weight == tg->shares))
2433 shares = calc_cfs_shares(cfs_rq, tg);
2435 reweight_entity(cfs_rq_of(se), se, shares);
2437 #else /* CONFIG_FAIR_GROUP_SCHED */
2438 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
2441 #endif /* CONFIG_FAIR_GROUP_SCHED */
2444 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2445 static const u32 runnable_avg_yN_inv[] = {
2446 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2447 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2448 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2449 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2450 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2451 0x85aac367, 0x82cd8698,
2455 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2456 * over-estimates when re-combining.
2458 static const u32 runnable_avg_yN_sum[] = {
2459 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2460 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2461 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2466 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2468 static __always_inline u64 decay_load(u64 val, u64 n)
2470 unsigned int local_n;
2474 else if (unlikely(n > LOAD_AVG_PERIOD * 63))
2477 /* after bounds checking we can collapse to 32-bit */
2481 * As y^PERIOD = 1/2, we can combine
2482 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2483 * With a look-up table which covers y^n (n<PERIOD)
2485 * To achieve constant time decay_load.
2487 if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
2488 val >>= local_n / LOAD_AVG_PERIOD;
2489 local_n %= LOAD_AVG_PERIOD;
2492 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
2497 * For updates fully spanning n periods, the contribution to runnable
2498 * average will be: \Sum 1024*y^n
2500 * We can compute this reasonably efficiently by combining:
2501 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2503 static u32 __compute_runnable_contrib(u64 n)
2507 if (likely(n <= LOAD_AVG_PERIOD))
2508 return runnable_avg_yN_sum[n];
2509 else if (unlikely(n >= LOAD_AVG_MAX_N))
2510 return LOAD_AVG_MAX;
2512 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2514 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2515 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];
2517 n -= LOAD_AVG_PERIOD;
2518 } while (n > LOAD_AVG_PERIOD);
2520 contrib = decay_load(contrib, n);
2521 return contrib + runnable_avg_yN_sum[n];
2524 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2525 #error "load tracking assumes 2^10 as unit"
2528 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2531 * We can represent the historical contribution to runnable average as the
2532 * coefficients of a geometric series. To do this we sub-divide our runnable
2533 * history into segments of approximately 1ms (1024us); label the segment that
2534 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2536 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2538 * (now) (~1ms ago) (~2ms ago)
2540 * Let u_i denote the fraction of p_i that the entity was runnable.
2542 * We then designate the fractions u_i as our co-efficients, yielding the
2543 * following representation of historical load:
2544 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2546 * We choose y based on the with of a reasonably scheduling period, fixing:
2549 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2550 * approximately half as much as the contribution to load within the last ms
2553 * When a period "rolls over" and we have new u_0`, multiplying the previous
2554 * sum again by y is sufficient to update:
2555 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2556 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2558 static __always_inline int
2559 __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2560 unsigned long weight, int running, struct cfs_rq *cfs_rq)
2562 u64 delta, scaled_delta, periods;
2564 unsigned int delta_w, scaled_delta_w, decayed = 0;
2565 unsigned long scale_freq, scale_cpu;
2567 delta = now - sa->last_update_time;
2569 * This should only happen when time goes backwards, which it
2570 * unfortunately does during sched clock init when we swap over to TSC.
2572 if ((s64)delta < 0) {
2573 sa->last_update_time = now;
2578 * Use 1024ns as the unit of measurement since it's a reasonable
2579 * approximation of 1us and fast to compute.
2584 sa->last_update_time = now;
2586 scale_freq = arch_scale_freq_capacity(NULL, cpu);
2587 scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
2588 trace_sched_contrib_scale_f(cpu, scale_freq, scale_cpu);
2590 /* delta_w is the amount already accumulated against our next period */
2591 delta_w = sa->period_contrib;
2592 if (delta + delta_w >= 1024) {
2595 /* how much left for next period will start over, we don't know yet */
2596 sa->period_contrib = 0;
2599 * Now that we know we're crossing a period boundary, figure
2600 * out how much from delta we need to complete the current
2601 * period and accrue it.
2603 delta_w = 1024 - delta_w;
2604 scaled_delta_w = cap_scale(delta_w, scale_freq);
2606 sa->load_sum += weight * scaled_delta_w;
2608 cfs_rq->runnable_load_sum +=
2609 weight * scaled_delta_w;
2613 sa->util_sum += scaled_delta_w * scale_cpu;
2617 /* Figure out how many additional periods this update spans */
2618 periods = delta / 1024;
2621 sa->load_sum = decay_load(sa->load_sum, periods + 1);
2623 cfs_rq->runnable_load_sum =
2624 decay_load(cfs_rq->runnable_load_sum, periods + 1);
2626 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2628 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2629 contrib = __compute_runnable_contrib(periods);
2630 contrib = cap_scale(contrib, scale_freq);
2632 sa->load_sum += weight * contrib;
2634 cfs_rq->runnable_load_sum += weight * contrib;
2637 sa->util_sum += contrib * scale_cpu;
2640 /* Remainder of delta accrued against u_0` */
2641 scaled_delta = cap_scale(delta, scale_freq);
2643 sa->load_sum += weight * scaled_delta;
2645 cfs_rq->runnable_load_sum += weight * scaled_delta;
2648 sa->util_sum += scaled_delta * scale_cpu;
2650 sa->period_contrib += delta;
2653 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2655 cfs_rq->runnable_load_avg =
2656 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
2658 sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2664 #ifdef CONFIG_FAIR_GROUP_SCHED
2666 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2667 * and effective_load (which is not done because it is too costly).
2669 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2671 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2673 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
2674 atomic_long_add(delta, &cfs_rq->tg->load_avg);
2675 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2679 #else /* CONFIG_FAIR_GROUP_SCHED */
2680 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2681 #endif /* CONFIG_FAIR_GROUP_SCHED */
2683 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2686 * Unsigned subtract and clamp on underflow.
2688 * Explicitly do a load-store to ensure the intermediate value never hits
2689 * memory. This allows lockless observations without ever seeing the negative
2692 #define sub_positive(_ptr, _val) do { \
2693 typeof(_ptr) ptr = (_ptr); \
2694 typeof(*ptr) val = (_val); \
2695 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2699 WRITE_ONCE(*ptr, res); \
2702 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2703 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2705 struct sched_avg *sa = &cfs_rq->avg;
2706 int decayed, removed = 0;
2708 if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2709 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2710 sub_positive(&sa->load_avg, r);
2711 sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
2715 if (atomic_long_read(&cfs_rq->removed_util_avg)) {
2716 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2717 sub_positive(&sa->util_avg, r);
2718 sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
2721 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2722 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2724 #ifndef CONFIG_64BIT
2726 cfs_rq->load_last_update_time_copy = sa->last_update_time;
2729 return decayed || removed;
2732 /* Update task and its cfs_rq load average */
2733 static inline void update_load_avg(struct sched_entity *se, int update_tg)
2735 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2736 u64 now = cfs_rq_clock_task(cfs_rq);
2737 int cpu = cpu_of(rq_of(cfs_rq));
2740 * Track task load average for carrying it to new CPU after migrated, and
2741 * track group sched_entity load average for task_h_load calc in migration
2743 __update_load_avg(now, cpu, &se->avg,
2744 se->on_rq * scale_load_down(se->load.weight),
2745 cfs_rq->curr == se, NULL);
2747 if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
2748 update_tg_load_avg(cfs_rq, 0);
2750 if (entity_is_task(se))
2751 trace_sched_load_avg_task(task_of(se), &se->avg);
2754 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2756 if (!sched_feat(ATTACH_AGE_LOAD))
2760 * If we got migrated (either between CPUs or between cgroups) we'll
2761 * have aged the average right before clearing @last_update_time.
2763 if (se->avg.last_update_time) {
2764 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2765 &se->avg, 0, 0, NULL);
2768 * XXX: we could have just aged the entire load away if we've been
2769 * absent from the fair class for too long.
2774 se->avg.last_update_time = cfs_rq->avg.last_update_time;
2775 cfs_rq->avg.load_avg += se->avg.load_avg;
2776 cfs_rq->avg.load_sum += se->avg.load_sum;
2777 cfs_rq->avg.util_avg += se->avg.util_avg;
2778 cfs_rq->avg.util_sum += se->avg.util_sum;
2781 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2783 __update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
2784 &se->avg, se->on_rq * scale_load_down(se->load.weight),
2785 cfs_rq->curr == se, NULL);
2787 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
2788 sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
2789 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
2790 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
2793 /* Add the load generated by se into cfs_rq's load average */
2795 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2797 struct sched_avg *sa = &se->avg;
2798 u64 now = cfs_rq_clock_task(cfs_rq);
2799 int migrated, decayed;
2801 migrated = !sa->last_update_time;
2803 __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2804 se->on_rq * scale_load_down(se->load.weight),
2805 cfs_rq->curr == se, NULL);
2808 decayed = update_cfs_rq_load_avg(now, cfs_rq);
2810 cfs_rq->runnable_load_avg += sa->load_avg;
2811 cfs_rq->runnable_load_sum += sa->load_sum;
2814 attach_entity_load_avg(cfs_rq, se);
2816 if (decayed || migrated)
2817 update_tg_load_avg(cfs_rq, 0);
2820 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
2822 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2824 update_load_avg(se, 1);
2826 cfs_rq->runnable_load_avg =
2827 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
2828 cfs_rq->runnable_load_sum =
2829 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2832 #ifndef CONFIG_64BIT
2833 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2835 u64 last_update_time_copy;
2836 u64 last_update_time;
2839 last_update_time_copy = cfs_rq->load_last_update_time_copy;
2841 last_update_time = cfs_rq->avg.last_update_time;
2842 } while (last_update_time != last_update_time_copy);
2844 return last_update_time;
2847 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
2849 return cfs_rq->avg.last_update_time;
2854 * Task first catches up with cfs_rq, and then subtract
2855 * itself from the cfs_rq (task must be off the queue now).
2857 void remove_entity_load_avg(struct sched_entity *se)
2859 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2860 u64 last_update_time;
2863 * Newly created task or never used group entity should not be removed
2864 * from its (source) cfs_rq
2866 if (se->avg.last_update_time == 0)
2869 last_update_time = cfs_rq_last_update_time(cfs_rq);
2871 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2872 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
2873 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2877 * Update the rq's load with the elapsed running time before entering
2878 * idle. if the last scheduled task is not a CFS task, idle_enter will
2879 * be the only way to update the runnable statistic.
2881 void idle_enter_fair(struct rq *this_rq)
2886 * Update the rq's load with the elapsed idle time before a task is
2887 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
2888 * be the only way to update the runnable statistic.
2890 void idle_exit_fair(struct rq *this_rq)
2894 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
2896 return cfs_rq->runnable_load_avg;
2899 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
2901 return cfs_rq->avg.load_avg;
2904 static int idle_balance(struct rq *this_rq);
2906 #else /* CONFIG_SMP */
2908 static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
2910 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2912 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2913 static inline void remove_entity_load_avg(struct sched_entity *se) {}
2916 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2918 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2920 static inline int idle_balance(struct rq *rq)
2925 #endif /* CONFIG_SMP */
2927 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2929 #ifdef CONFIG_SCHEDSTATS
2930 struct task_struct *tsk = NULL;
2932 if (entity_is_task(se))
2935 if (se->statistics.sleep_start) {
2936 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2941 if (unlikely(delta > se->statistics.sleep_max))
2942 se->statistics.sleep_max = delta;
2944 se->statistics.sleep_start = 0;
2945 se->statistics.sum_sleep_runtime += delta;
2948 account_scheduler_latency(tsk, delta >> 10, 1);
2949 trace_sched_stat_sleep(tsk, delta);
2952 if (se->statistics.block_start) {
2953 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2958 if (unlikely(delta > se->statistics.block_max))
2959 se->statistics.block_max = delta;
2961 se->statistics.block_start = 0;
2962 se->statistics.sum_sleep_runtime += delta;
2965 if (tsk->in_iowait) {
2966 se->statistics.iowait_sum += delta;
2967 se->statistics.iowait_count++;
2968 trace_sched_stat_iowait(tsk, delta);
2971 trace_sched_stat_blocked(tsk, delta);
2972 trace_sched_blocked_reason(tsk);
2975 * Blocking time is in units of nanosecs, so shift by
2976 * 20 to get a milliseconds-range estimation of the
2977 * amount of time that the task spent sleeping:
2979 if (unlikely(prof_on == SLEEP_PROFILING)) {
2980 profile_hits(SLEEP_PROFILING,
2981 (void *)get_wchan(tsk),
2984 account_scheduler_latency(tsk, delta >> 10, 0);
2990 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
2992 #ifdef CONFIG_SCHED_DEBUG
2993 s64 d = se->vruntime - cfs_rq->min_vruntime;
2998 if (d > 3*sysctl_sched_latency)
2999 schedstat_inc(cfs_rq, nr_spread_over);
3004 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
3006 u64 vruntime = cfs_rq->min_vruntime;
3009 * The 'current' period is already promised to the current tasks,
3010 * however the extra weight of the new task will slow them down a
3011 * little, place the new task so that it fits in the slot that
3012 * stays open at the end.
3014 if (initial && sched_feat(START_DEBIT))
3015 vruntime += sched_vslice(cfs_rq, se);
3017 /* sleeps up to a single latency don't count. */
3019 unsigned long thresh = sysctl_sched_latency;
3022 * Halve their sleep time's effect, to allow
3023 * for a gentler effect of sleepers:
3025 if (sched_feat(GENTLE_FAIR_SLEEPERS))
3031 /* ensure we never gain time by being placed backwards. */
3032 se->vruntime = max_vruntime(se->vruntime, vruntime);
3035 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
3038 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3041 * Update the normalized vruntime before updating min_vruntime
3042 * through calling update_curr().
3044 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3045 se->vruntime += cfs_rq->min_vruntime;
3048 * Update run-time statistics of the 'current'.
3050 update_curr(cfs_rq);
3051 enqueue_entity_load_avg(cfs_rq, se);
3052 account_entity_enqueue(cfs_rq, se);
3053 update_cfs_shares(cfs_rq);
3055 if (flags & ENQUEUE_WAKEUP) {
3056 place_entity(cfs_rq, se, 0);
3057 enqueue_sleeper(cfs_rq, se);
3060 update_stats_enqueue(cfs_rq, se);
3061 check_spread(cfs_rq, se);
3062 if (se != cfs_rq->curr)
3063 __enqueue_entity(cfs_rq, se);
3066 if (cfs_rq->nr_running == 1) {
3067 list_add_leaf_cfs_rq(cfs_rq);
3068 check_enqueue_throttle(cfs_rq);
3072 static void __clear_buddies_last(struct sched_entity *se)
3074 for_each_sched_entity(se) {
3075 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3076 if (cfs_rq->last != se)
3079 cfs_rq->last = NULL;
3083 static void __clear_buddies_next(struct sched_entity *se)
3085 for_each_sched_entity(se) {
3086 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3087 if (cfs_rq->next != se)
3090 cfs_rq->next = NULL;
3094 static void __clear_buddies_skip(struct sched_entity *se)
3096 for_each_sched_entity(se) {
3097 struct cfs_rq *cfs_rq = cfs_rq_of(se);
3098 if (cfs_rq->skip != se)
3101 cfs_rq->skip = NULL;
3105 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
3107 if (cfs_rq->last == se)
3108 __clear_buddies_last(se);
3110 if (cfs_rq->next == se)
3111 __clear_buddies_next(se);
3113 if (cfs_rq->skip == se)
3114 __clear_buddies_skip(se);
3117 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3120 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3123 * Update run-time statistics of the 'current'.
3125 update_curr(cfs_rq);
3126 dequeue_entity_load_avg(cfs_rq, se);
3128 update_stats_dequeue(cfs_rq, se);
3129 if (flags & DEQUEUE_SLEEP) {
3130 #ifdef CONFIG_SCHEDSTATS
3131 if (entity_is_task(se)) {
3132 struct task_struct *tsk = task_of(se);
3134 if (tsk->state & TASK_INTERRUPTIBLE)
3135 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3136 if (tsk->state & TASK_UNINTERRUPTIBLE)
3137 se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3142 clear_buddies(cfs_rq, se);
3144 if (se != cfs_rq->curr)
3145 __dequeue_entity(cfs_rq, se);
3147 account_entity_dequeue(cfs_rq, se);
3150 * Normalize the entity after updating the min_vruntime because the
3151 * update can refer to the ->curr item and we need to reflect this
3152 * movement in our normalized position.
3154 if (!(flags & DEQUEUE_SLEEP))
3155 se->vruntime -= cfs_rq->min_vruntime;
3157 /* return excess runtime on last dequeue */
3158 return_cfs_rq_runtime(cfs_rq);
3160 update_min_vruntime(cfs_rq);
3161 update_cfs_shares(cfs_rq);
3165 * Preempt the current task with a newly woken task if needed:
3168 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3170 unsigned long ideal_runtime, delta_exec;
3171 struct sched_entity *se;
3174 ideal_runtime = sched_slice(cfs_rq, curr);
3175 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3176 if (delta_exec > ideal_runtime) {
3177 resched_curr(rq_of(cfs_rq));
3179 * The current task ran long enough, ensure it doesn't get
3180 * re-elected due to buddy favours.
3182 clear_buddies(cfs_rq, curr);
3187 * Ensure that a task that missed wakeup preemption by a
3188 * narrow margin doesn't have to wait for a full slice.
3189 * This also mitigates buddy induced latencies under load.
3191 if (delta_exec < sysctl_sched_min_granularity)
3194 se = __pick_first_entity(cfs_rq);
3195 delta = curr->vruntime - se->vruntime;
3200 if (delta > ideal_runtime)
3201 resched_curr(rq_of(cfs_rq));
3205 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3207 /* 'current' is not kept within the tree. */
3210 * Any task has to be enqueued before it get to execute on
3211 * a CPU. So account for the time it spent waiting on the
3214 update_stats_wait_end(cfs_rq, se);
3215 __dequeue_entity(cfs_rq, se);
3216 update_load_avg(se, 1);
3219 update_stats_curr_start(cfs_rq, se);
3221 #ifdef CONFIG_SCHEDSTATS
3223 * Track our maximum slice length, if the CPU's load is at
3224 * least twice that of our own weight (i.e. dont track it
3225 * when there are only lesser-weight tasks around):
3227 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3228 se->statistics.slice_max = max(se->statistics.slice_max,
3229 se->sum_exec_runtime - se->prev_sum_exec_runtime);
3232 se->prev_sum_exec_runtime = se->sum_exec_runtime;
3236 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
3239 * Pick the next process, keeping these things in mind, in this order:
3240 * 1) keep things fair between processes/task groups
3241 * 2) pick the "next" process, since someone really wants that to run
3242 * 3) pick the "last" process, for cache locality
3243 * 4) do not run the "skip" process, if something else is available
3245 static struct sched_entity *
3246 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3248 struct sched_entity *left = __pick_first_entity(cfs_rq);
3249 struct sched_entity *se;
3252 * If curr is set we have to see if its left of the leftmost entity
3253 * still in the tree, provided there was anything in the tree at all.
3255 if (!left || (curr && entity_before(curr, left)))
3258 se = left; /* ideally we run the leftmost entity */
3261 * Avoid running the skip buddy, if running something else can
3262 * be done without getting too unfair.
3264 if (cfs_rq->skip == se) {
3265 struct sched_entity *second;
3268 second = __pick_first_entity(cfs_rq);
3270 second = __pick_next_entity(se);
3271 if (!second || (curr && entity_before(curr, second)))
3275 if (second && wakeup_preempt_entity(second, left) < 1)
3280 * Prefer last buddy, try to return the CPU to a preempted task.
3282 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
3286 * Someone really wants this to run. If it's not unfair, run it.
3288 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
3291 clear_buddies(cfs_rq, se);
3296 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3298 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3301 * If still on the runqueue then deactivate_task()
3302 * was not called and update_curr() has to be done:
3305 update_curr(cfs_rq);
3307 /* throttle cfs_rqs exceeding runtime */
3308 check_cfs_rq_runtime(cfs_rq);
3310 check_spread(cfs_rq, prev);
3312 update_stats_wait_start(cfs_rq, prev);
3313 /* Put 'current' back into the tree. */
3314 __enqueue_entity(cfs_rq, prev);
3315 /* in !on_rq case, update occurred at dequeue */
3316 update_load_avg(prev, 0);
3318 cfs_rq->curr = NULL;
3322 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3325 * Update run-time statistics of the 'current'.
3327 update_curr(cfs_rq);
3330 * Ensure that runnable average is periodically updated.
3332 update_load_avg(curr, 1);
3333 update_cfs_shares(cfs_rq);
3335 #ifdef CONFIG_SCHED_HRTICK
3337 * queued ticks are scheduled to match the slice, so don't bother
3338 * validating it and just reschedule.
3341 resched_curr(rq_of(cfs_rq));
3345 * don't let the period tick interfere with the hrtick preemption
3347 if (!sched_feat(DOUBLE_TICK) &&
3348 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
3352 if (cfs_rq->nr_running > 1)
3353 check_preempt_tick(cfs_rq, curr);
3357 /**************************************************
3358 * CFS bandwidth control machinery
3361 #ifdef CONFIG_CFS_BANDWIDTH
3363 #ifdef HAVE_JUMP_LABEL
3364 static struct static_key __cfs_bandwidth_used;
3366 static inline bool cfs_bandwidth_used(void)
3368 return static_key_false(&__cfs_bandwidth_used);
3371 void cfs_bandwidth_usage_inc(void)
3373 static_key_slow_inc(&__cfs_bandwidth_used);
3376 void cfs_bandwidth_usage_dec(void)
3378 static_key_slow_dec(&__cfs_bandwidth_used);
3380 #else /* HAVE_JUMP_LABEL */
3381 static bool cfs_bandwidth_used(void)
3386 void cfs_bandwidth_usage_inc(void) {}
3387 void cfs_bandwidth_usage_dec(void) {}
3388 #endif /* HAVE_JUMP_LABEL */
3391 * default period for cfs group bandwidth.
3392 * default: 0.1s, units: nanoseconds
3394 static inline u64 default_cfs_period(void)
3396 return 100000000ULL;
3399 static inline u64 sched_cfs_bandwidth_slice(void)
3401 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
3405 * Replenish runtime according to assigned quota and update expiration time.
3406 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3407 * additional synchronization around rq->lock.
3409 * requires cfs_b->lock
3411 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
3415 if (cfs_b->quota == RUNTIME_INF)
3418 now = sched_clock_cpu(smp_processor_id());
3419 cfs_b->runtime = cfs_b->quota;
3420 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
3423 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
3425 return &tg->cfs_bandwidth;
3428 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3429 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
3431 if (unlikely(cfs_rq->throttle_count))
3432 return cfs_rq->throttled_clock_task;
3434 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3437 /* returns 0 on failure to allocate runtime */
3438 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3440 struct task_group *tg = cfs_rq->tg;
3441 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
3442 u64 amount = 0, min_amount, expires;
3444 /* note: this is a positive sum as runtime_remaining <= 0 */
3445 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
3447 raw_spin_lock(&cfs_b->lock);
3448 if (cfs_b->quota == RUNTIME_INF)
3449 amount = min_amount;
3451 start_cfs_bandwidth(cfs_b);
3453 if (cfs_b->runtime > 0) {
3454 amount = min(cfs_b->runtime, min_amount);
3455 cfs_b->runtime -= amount;
3459 expires = cfs_b->runtime_expires;
3460 raw_spin_unlock(&cfs_b->lock);
3462 cfs_rq->runtime_remaining += amount;
3464 * we may have advanced our local expiration to account for allowed
3465 * spread between our sched_clock and the one on which runtime was
3468 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
3469 cfs_rq->runtime_expires = expires;
3471 return cfs_rq->runtime_remaining > 0;
3475 * Note: This depends on the synchronization provided by sched_clock and the
3476 * fact that rq->clock snapshots this value.
3478 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3480 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3482 /* if the deadline is ahead of our clock, nothing to do */
3483 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3486 if (cfs_rq->runtime_remaining < 0)
3490 * If the local deadline has passed we have to consider the
3491 * possibility that our sched_clock is 'fast' and the global deadline
3492 * has not truly expired.
3494 * Fortunately we can check determine whether this the case by checking
3495 * whether the global deadline has advanced. It is valid to compare
3496 * cfs_b->runtime_expires without any locks since we only care about
3497 * exact equality, so a partial write will still work.
3500 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
3501 /* extend local deadline, drift is bounded above by 2 ticks */
3502 cfs_rq->runtime_expires += TICK_NSEC;
3504 /* global deadline is ahead, expiration has passed */
3505 cfs_rq->runtime_remaining = 0;
3509 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3511 /* dock delta_exec before expiring quota (as it could span periods) */
3512 cfs_rq->runtime_remaining -= delta_exec;
3513 expire_cfs_rq_runtime(cfs_rq);
3515 if (likely(cfs_rq->runtime_remaining > 0))
3519 * if we're unable to extend our runtime we resched so that the active
3520 * hierarchy can be throttled
3522 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
3523 resched_curr(rq_of(cfs_rq));
3526 static __always_inline
3527 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3529 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3532 __account_cfs_rq_runtime(cfs_rq, delta_exec);
3535 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
3537 return cfs_bandwidth_used() && cfs_rq->throttled;
3540 /* check whether cfs_rq, or any parent, is throttled */
3541 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
3543 return cfs_bandwidth_used() && cfs_rq->throttle_count;
3547 * Ensure that neither of the group entities corresponding to src_cpu or
3548 * dest_cpu are members of a throttled hierarchy when performing group
3549 * load-balance operations.
3551 static inline int throttled_lb_pair(struct task_group *tg,
3552 int src_cpu, int dest_cpu)
3554 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
3556 src_cfs_rq = tg->cfs_rq[src_cpu];
3557 dest_cfs_rq = tg->cfs_rq[dest_cpu];
3559 return throttled_hierarchy(src_cfs_rq) ||
3560 throttled_hierarchy(dest_cfs_rq);
3563 /* updated child weight may affect parent so we have to do this bottom up */
3564 static int tg_unthrottle_up(struct task_group *tg, void *data)
3566 struct rq *rq = data;
3567 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3569 cfs_rq->throttle_count--;
3571 if (!cfs_rq->throttle_count) {
3572 /* adjust cfs_rq_clock_task() */
3573 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3574 cfs_rq->throttled_clock_task;
3581 static int tg_throttle_down(struct task_group *tg, void *data)
3583 struct rq *rq = data;
3584 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
3586 /* group is entering throttled state, stop time */
3587 if (!cfs_rq->throttle_count)
3588 cfs_rq->throttled_clock_task = rq_clock_task(rq);
3589 cfs_rq->throttle_count++;
3594 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3596 struct rq *rq = rq_of(cfs_rq);
3597 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3598 struct sched_entity *se;
3599 long task_delta, dequeue = 1;
3602 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
3604 /* freeze hierarchy runnable averages while throttled */
3606 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
3609 task_delta = cfs_rq->h_nr_running;
3610 for_each_sched_entity(se) {
3611 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
3612 /* throttled entity or throttle-on-deactivate */
3617 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
3618 qcfs_rq->h_nr_running -= task_delta;
3620 if (qcfs_rq->load.weight)
3625 sub_nr_running(rq, task_delta);
3627 cfs_rq->throttled = 1;
3628 cfs_rq->throttled_clock = rq_clock(rq);
3629 raw_spin_lock(&cfs_b->lock);
3630 empty = list_empty(&cfs_b->throttled_cfs_rq);
3633 * Add to the _head_ of the list, so that an already-started
3634 * distribute_cfs_runtime will not see us
3636 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3639 * If we're the first throttled task, make sure the bandwidth
3643 start_cfs_bandwidth(cfs_b);
3645 raw_spin_unlock(&cfs_b->lock);
3648 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3650 struct rq *rq = rq_of(cfs_rq);
3651 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3652 struct sched_entity *se;
3656 se = cfs_rq->tg->se[cpu_of(rq)];
3658 cfs_rq->throttled = 0;
3660 update_rq_clock(rq);
3662 raw_spin_lock(&cfs_b->lock);
3663 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3664 list_del_rcu(&cfs_rq->throttled_list);
3665 raw_spin_unlock(&cfs_b->lock);
3667 /* update hierarchical throttle state */
3668 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
3670 if (!cfs_rq->load.weight)
3673 task_delta = cfs_rq->h_nr_running;
3674 for_each_sched_entity(se) {
3678 cfs_rq = cfs_rq_of(se);
3680 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
3681 cfs_rq->h_nr_running += task_delta;
3683 if (cfs_rq_throttled(cfs_rq))
3688 add_nr_running(rq, task_delta);
3690 /* determine whether we need to wake up potentially idle cpu */
3691 if (rq->curr == rq->idle && rq->cfs.nr_running)
3695 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
3696 u64 remaining, u64 expires)
3698 struct cfs_rq *cfs_rq;
3700 u64 starting_runtime = remaining;
3703 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
3705 struct rq *rq = rq_of(cfs_rq);
3707 raw_spin_lock(&rq->lock);
3708 if (!cfs_rq_throttled(cfs_rq))
3711 runtime = -cfs_rq->runtime_remaining + 1;
3712 if (runtime > remaining)
3713 runtime = remaining;
3714 remaining -= runtime;
3716 cfs_rq->runtime_remaining += runtime;
3717 cfs_rq->runtime_expires = expires;
3719 /* we check whether we're throttled above */
3720 if (cfs_rq->runtime_remaining > 0)
3721 unthrottle_cfs_rq(cfs_rq);
3724 raw_spin_unlock(&rq->lock);
3731 return starting_runtime - remaining;
3735 * Responsible for refilling a task_group's bandwidth and unthrottling its
3736 * cfs_rqs as appropriate. If there has been no activity within the last
3737 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3738 * used to track this state.
3740 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
3742 u64 runtime, runtime_expires;
3745 /* no need to continue the timer with no bandwidth constraint */
3746 if (cfs_b->quota == RUNTIME_INF)
3747 goto out_deactivate;
3749 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3750 cfs_b->nr_periods += overrun;
3753 * idle depends on !throttled (for the case of a large deficit), and if
3754 * we're going inactive then everything else can be deferred
3756 if (cfs_b->idle && !throttled)
3757 goto out_deactivate;
3759 __refill_cfs_bandwidth_runtime(cfs_b);
3762 /* mark as potentially idle for the upcoming period */
3767 /* account preceding periods in which throttling occurred */
3768 cfs_b->nr_throttled += overrun;
3770 runtime_expires = cfs_b->runtime_expires;
3773 * This check is repeated as we are holding onto the new bandwidth while
3774 * we unthrottle. This can potentially race with an unthrottled group
3775 * trying to acquire new bandwidth from the global pool. This can result
3776 * in us over-using our runtime if it is all used during this loop, but
3777 * only by limited amounts in that extreme case.
3779 while (throttled && cfs_b->runtime > 0) {
3780 runtime = cfs_b->runtime;
3781 raw_spin_unlock(&cfs_b->lock);
3782 /* we can't nest cfs_b->lock while distributing bandwidth */
3783 runtime = distribute_cfs_runtime(cfs_b, runtime,
3785 raw_spin_lock(&cfs_b->lock);
3787 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3789 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3793 * While we are ensured activity in the period following an
3794 * unthrottle, this also covers the case in which the new bandwidth is
3795 * insufficient to cover the existing bandwidth deficit. (Forcing the
3796 * timer to remain active while there are any throttled entities.)
3806 /* a cfs_rq won't donate quota below this amount */
3807 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
3808 /* minimum remaining period time to redistribute slack quota */
3809 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
3810 /* how long we wait to gather additional slack before distributing */
3811 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
3814 * Are we near the end of the current quota period?
3816 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3817 * hrtimer base being cleared by hrtimer_start. In the case of
3818 * migrate_hrtimers, base is never cleared, so we are fine.
3820 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
3822 struct hrtimer *refresh_timer = &cfs_b->period_timer;
3825 /* if the call-back is running a quota refresh is already occurring */
3826 if (hrtimer_callback_running(refresh_timer))
3829 /* is a quota refresh about to occur? */
3830 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
3831 if (remaining < min_expire)
3837 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
3839 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
3841 /* if there's a quota refresh soon don't bother with slack */
3842 if (runtime_refresh_within(cfs_b, min_left))
3845 hrtimer_start(&cfs_b->slack_timer,
3846 ns_to_ktime(cfs_bandwidth_slack_period),
3850 /* we know any runtime found here is valid as update_curr() precedes return */
3851 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3853 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
3854 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
3856 if (slack_runtime <= 0)
3859 raw_spin_lock(&cfs_b->lock);
3860 if (cfs_b->quota != RUNTIME_INF &&
3861 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
3862 cfs_b->runtime += slack_runtime;
3864 /* we are under rq->lock, defer unthrottling using a timer */
3865 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
3866 !list_empty(&cfs_b->throttled_cfs_rq))
3867 start_cfs_slack_bandwidth(cfs_b);
3869 raw_spin_unlock(&cfs_b->lock);
3871 /* even if it's not valid for return we don't want to try again */
3872 cfs_rq->runtime_remaining -= slack_runtime;
3875 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3877 if (!cfs_bandwidth_used())
3880 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3883 __return_cfs_rq_runtime(cfs_rq);
3887 * This is done with a timer (instead of inline with bandwidth return) since
3888 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
3890 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
3892 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
3895 /* confirm we're still not at a refresh boundary */
3896 raw_spin_lock(&cfs_b->lock);
3897 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
3898 raw_spin_unlock(&cfs_b->lock);
3902 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3903 runtime = cfs_b->runtime;
3905 expires = cfs_b->runtime_expires;
3906 raw_spin_unlock(&cfs_b->lock);
3911 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
3913 raw_spin_lock(&cfs_b->lock);
3914 if (expires == cfs_b->runtime_expires)
3915 cfs_b->runtime -= min(runtime, cfs_b->runtime);
3916 raw_spin_unlock(&cfs_b->lock);
3920 * When a group wakes up we want to make sure that its quota is not already
3921 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
3922 * runtime as update_curr() throttling can not not trigger until it's on-rq.
3924 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
3926 if (!cfs_bandwidth_used())
3929 /* an active group must be handled by the update_curr()->put() path */
3930 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
3933 /* ensure the group is not already throttled */
3934 if (cfs_rq_throttled(cfs_rq))
3937 /* update runtime allocation */
3938 account_cfs_rq_runtime(cfs_rq, 0);
3939 if (cfs_rq->runtime_remaining <= 0)
3940 throttle_cfs_rq(cfs_rq);
3943 /* conditionally throttle active cfs_rq's from put_prev_entity() */
3944 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3946 if (!cfs_bandwidth_used())
3949 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3953 * it's possible for a throttled entity to be forced into a running
3954 * state (e.g. set_curr_task), in this case we're finished.
3956 if (cfs_rq_throttled(cfs_rq))
3959 throttle_cfs_rq(cfs_rq);
3963 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
3965 struct cfs_bandwidth *cfs_b =
3966 container_of(timer, struct cfs_bandwidth, slack_timer);
3968 do_sched_cfs_slack_timer(cfs_b);
3970 return HRTIMER_NORESTART;
3973 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
3975 struct cfs_bandwidth *cfs_b =
3976 container_of(timer, struct cfs_bandwidth, period_timer);
3980 raw_spin_lock(&cfs_b->lock);
3982 overrun = hrtimer_forward_now(timer, cfs_b->period);
3986 idle = do_sched_cfs_period_timer(cfs_b, overrun);
3989 cfs_b->period_active = 0;
3990 raw_spin_unlock(&cfs_b->lock);
3992 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
3995 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3997 raw_spin_lock_init(&cfs_b->lock);
3999 cfs_b->quota = RUNTIME_INF;
4000 cfs_b->period = ns_to_ktime(default_cfs_period());
4002 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
4003 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4004 cfs_b->period_timer.function = sched_cfs_period_timer;
4005 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
4006 cfs_b->slack_timer.function = sched_cfs_slack_timer;
4009 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4011 cfs_rq->runtime_enabled = 0;
4012 INIT_LIST_HEAD(&cfs_rq->throttled_list);
4015 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4017 lockdep_assert_held(&cfs_b->lock);
4019 if (!cfs_b->period_active) {
4020 cfs_b->period_active = 1;
4021 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4022 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4026 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4028 /* init_cfs_bandwidth() was not called */
4029 if (!cfs_b->throttled_cfs_rq.next)
4032 hrtimer_cancel(&cfs_b->period_timer);
4033 hrtimer_cancel(&cfs_b->slack_timer);
4036 static void __maybe_unused update_runtime_enabled(struct rq *rq)
4038 struct cfs_rq *cfs_rq;
4040 for_each_leaf_cfs_rq(rq, cfs_rq) {
4041 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;
4043 raw_spin_lock(&cfs_b->lock);
4044 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
4045 raw_spin_unlock(&cfs_b->lock);
4049 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4051 struct cfs_rq *cfs_rq;
4053 for_each_leaf_cfs_rq(rq, cfs_rq) {
4054 if (!cfs_rq->runtime_enabled)
4058 * clock_task is not advancing so we just need to make sure
4059 * there's some valid quota amount
4061 cfs_rq->runtime_remaining = 1;
4063 * Offline rq is schedulable till cpu is completely disabled
4064 * in take_cpu_down(), so we prevent new cfs throttling here.
4066 cfs_rq->runtime_enabled = 0;
4068 if (cfs_rq_throttled(cfs_rq))
4069 unthrottle_cfs_rq(cfs_rq);
4073 #else /* CONFIG_CFS_BANDWIDTH */
4074 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
4076 return rq_clock_task(rq_of(cfs_rq));
4079 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4080 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4081 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4082 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4084 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
4089 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
4094 static inline int throttled_lb_pair(struct task_group *tg,
4095 int src_cpu, int dest_cpu)
4100 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4102 #ifdef CONFIG_FAIR_GROUP_SCHED
4103 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4106 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
4110 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
4111 static inline void update_runtime_enabled(struct rq *rq) {}
4112 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4114 #endif /* CONFIG_CFS_BANDWIDTH */
4116 /**************************************************
4117 * CFS operations on tasks:
4120 #ifdef CONFIG_SCHED_HRTICK
4121 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
4123 struct sched_entity *se = &p->se;
4124 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4126 WARN_ON(task_rq(p) != rq);
4128 if (cfs_rq->nr_running > 1) {
4129 u64 slice = sched_slice(cfs_rq, se);
4130 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
4131 s64 delta = slice - ran;
4138 hrtick_start(rq, delta);
4143 * called from enqueue/dequeue and updates the hrtick when the
4144 * current task is from our class and nr_running is low enough
4147 static void hrtick_update(struct rq *rq)
4149 struct task_struct *curr = rq->curr;
4151 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4154 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
4155 hrtick_start_fair(rq, curr);
4157 #else /* !CONFIG_SCHED_HRTICK */
4159 hrtick_start_fair(struct rq *rq, struct task_struct *p)
4163 static inline void hrtick_update(struct rq *rq)
4168 static inline unsigned long boosted_cpu_util(int cpu);
4170 static void update_capacity_of(int cpu)
4172 unsigned long req_cap;
4177 /* Convert scale-invariant capacity to cpu. */
4178 req_cap = boosted_cpu_util(cpu);
4179 req_cap = req_cap * SCHED_CAPACITY_SCALE / capacity_orig_of(cpu);
4180 set_cfs_cpu_capacity(cpu, true, req_cap);
4183 static bool cpu_overutilized(int cpu);
4186 * The enqueue_task method is called before nr_running is
4187 * increased. Here we update the fair scheduling stats and
4188 * then put the task into the rbtree:
4191 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4193 struct cfs_rq *cfs_rq;
4194 struct sched_entity *se = &p->se;
4195 int task_new = flags & ENQUEUE_WAKEUP_NEW;
4196 int task_wakeup = flags & ENQUEUE_WAKEUP;
4198 for_each_sched_entity(se) {
4201 cfs_rq = cfs_rq_of(se);
4202 enqueue_entity(cfs_rq, se, flags);
4205 * end evaluation on encountering a throttled cfs_rq
4207 * note: in the case of encountering a throttled cfs_rq we will
4208 * post the final h_nr_running increment below.
4210 if (cfs_rq_throttled(cfs_rq))
4212 cfs_rq->h_nr_running++;
4214 flags = ENQUEUE_WAKEUP;
4217 for_each_sched_entity(se) {
4218 cfs_rq = cfs_rq_of(se);
4219 cfs_rq->h_nr_running++;
4221 if (cfs_rq_throttled(cfs_rq))
4224 update_load_avg(se, 1);
4225 update_cfs_shares(cfs_rq);
4229 add_nr_running(rq, 1);
4230 if (!task_new && !rq->rd->overutilized &&
4231 cpu_overutilized(rq->cpu))
4232 rq->rd->overutilized = true;
4234 schedtune_enqueue_task(p, cpu_of(rq));
4237 * We want to potentially trigger a freq switch
4238 * request only for tasks that are waking up; this is
4239 * because we get here also during load balancing, but
4240 * in these cases it seems wise to trigger as single
4241 * request after load balancing is done.
4243 if (task_new || task_wakeup)
4244 update_capacity_of(cpu_of(rq));
4249 static void set_next_buddy(struct sched_entity *se);
4252 * The dequeue_task method is called before nr_running is
4253 * decreased. We remove the task from the rbtree and
4254 * update the fair scheduling stats:
4256 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4258 struct cfs_rq *cfs_rq;
4259 struct sched_entity *se = &p->se;
4260 int task_sleep = flags & DEQUEUE_SLEEP;
4262 for_each_sched_entity(se) {
4263 cfs_rq = cfs_rq_of(se);
4264 dequeue_entity(cfs_rq, se, flags);
4267 * end evaluation on encountering a throttled cfs_rq
4269 * note: in the case of encountering a throttled cfs_rq we will
4270 * post the final h_nr_running decrement below.
4272 if (cfs_rq_throttled(cfs_rq))
4274 cfs_rq->h_nr_running--;
4276 /* Don't dequeue parent if it has other entities besides us */
4277 if (cfs_rq->load.weight) {
4279 * Bias pick_next to pick a task from this cfs_rq, as
4280 * p is sleeping when it is within its sched_slice.
4282 if (task_sleep && parent_entity(se))
4283 set_next_buddy(parent_entity(se));
4285 /* avoid re-evaluating load for this entity */
4286 se = parent_entity(se);
4289 flags |= DEQUEUE_SLEEP;
4292 for_each_sched_entity(se) {
4293 cfs_rq = cfs_rq_of(se);
4294 cfs_rq->h_nr_running--;
4296 if (cfs_rq_throttled(cfs_rq))
4299 update_load_avg(se, 1);
4300 update_cfs_shares(cfs_rq);
4304 sub_nr_running(rq, 1);
4305 schedtune_dequeue_task(p, cpu_of(rq));
4308 * We want to potentially trigger a freq switch
4309 * request only for tasks that are going to sleep;
4310 * this is because we get here also during load
4311 * balancing, but in these cases it seems wise to
4312 * trigger as single request after load balancing is
4316 if (rq->cfs.nr_running)
4317 update_capacity_of(cpu_of(rq));
4318 else if (sched_freq())
4319 set_cfs_cpu_capacity(cpu_of(rq), false, 0);
4328 * per rq 'load' arrray crap; XXX kill this.
4332 * The exact cpuload at various idx values, calculated at every tick would be
4333 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
4335 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
4336 * on nth tick when cpu may be busy, then we have:
4337 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4338 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
4340 * decay_load_missed() below does efficient calculation of
4341 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
4342 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
4344 * The calculation is approximated on a 128 point scale.
4345 * degrade_zero_ticks is the number of ticks after which load at any
4346 * particular idx is approximated to be zero.
4347 * degrade_factor is a precomputed table, a row for each load idx.
4348 * Each column corresponds to degradation factor for a power of two ticks,
4349 * based on 128 point scale.
4351 * row 2, col 3 (=12) says that the degradation at load idx 2 after
4352 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
4354 * With this power of 2 load factors, we can degrade the load n times
4355 * by looking at 1 bits in n and doing as many mult/shift instead of
4356 * n mult/shifts needed by the exact degradation.
4358 #define DEGRADE_SHIFT 7
4359 static const unsigned char
4360 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
4361 static const unsigned char
4362 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
4363 {0, 0, 0, 0, 0, 0, 0, 0},
4364 {64, 32, 8, 0, 0, 0, 0, 0},
4365 {96, 72, 40, 12, 1, 0, 0},
4366 {112, 98, 75, 43, 15, 1, 0},
4367 {120, 112, 98, 76, 45, 16, 2} };
4370 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4371 * would be when CPU is idle and so we just decay the old load without
4372 * adding any new load.
4374 static unsigned long
4375 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
4379 if (!missed_updates)
4382 if (missed_updates >= degrade_zero_ticks[idx])
4386 return load >> missed_updates;
4388 while (missed_updates) {
4389 if (missed_updates % 2)
4390 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
4392 missed_updates >>= 1;
4399 * Update rq->cpu_load[] statistics. This function is usually called every
4400 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
4401 * every tick. We fix it up based on jiffies.
4403 static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4404 unsigned long pending_updates)
4408 this_rq->nr_load_updates++;
4410 /* Update our load: */
4411 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
4412 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
4413 unsigned long old_load, new_load;
4415 /* scale is effectively 1 << i now, and >> i divides by scale */
4417 old_load = this_rq->cpu_load[i];
4418 old_load = decay_load_missed(old_load, pending_updates - 1, i);
4419 new_load = this_load;
4421 * Round up the averaging division if load is increasing. This
4422 * prevents us from getting stuck on 9 if the load is 10, for
4425 if (new_load > old_load)
4426 new_load += scale - 1;
4428 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
4431 sched_avg_update(this_rq);
4434 /* Used instead of source_load when we know the type == 0 */
4435 static unsigned long weighted_cpuload(const int cpu)
4437 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
4440 #ifdef CONFIG_NO_HZ_COMMON
4442 * There is no sane way to deal with nohz on smp when using jiffies because the
4443 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4444 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4446 * Therefore we cannot use the delta approach from the regular tick since that
4447 * would seriously skew the load calculation. However we'll make do for those
4448 * updates happening while idle (nohz_idle_balance) or coming out of idle
4449 * (tick_nohz_idle_exit).
4451 * This means we might still be one tick off for nohz periods.
4455 * Called from nohz_idle_balance() to update the load ratings before doing the
4458 static void update_idle_cpu_load(struct rq *this_rq)
4460 unsigned long curr_jiffies = READ_ONCE(jiffies);
4461 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4462 unsigned long pending_updates;
4465 * bail if there's load or we're actually up-to-date.
4467 if (load || curr_jiffies == this_rq->last_load_update_tick)
4470 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4471 this_rq->last_load_update_tick = curr_jiffies;
4473 __update_cpu_load(this_rq, load, pending_updates);
4477 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4479 void update_cpu_load_nohz(void)
4481 struct rq *this_rq = this_rq();
4482 unsigned long curr_jiffies = READ_ONCE(jiffies);
4483 unsigned long pending_updates;
4485 if (curr_jiffies == this_rq->last_load_update_tick)
4488 raw_spin_lock(&this_rq->lock);
4489 pending_updates = curr_jiffies - this_rq->last_load_update_tick;
4490 if (pending_updates) {
4491 this_rq->last_load_update_tick = curr_jiffies;
4493 * We were idle, this means load 0, the current load might be
4494 * !0 due to remote wakeups and the sort.
4496 __update_cpu_load(this_rq, 0, pending_updates);
4498 raw_spin_unlock(&this_rq->lock);
4500 #endif /* CONFIG_NO_HZ */
4503 * Called from scheduler_tick()
4505 void update_cpu_load_active(struct rq *this_rq)
4507 unsigned long load = weighted_cpuload(cpu_of(this_rq));
4509 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
4511 this_rq->last_load_update_tick = jiffies;
4512 __update_cpu_load(this_rq, load, 1);
4516 * Return a low guess at the load of a migration-source cpu weighted
4517 * according to the scheduling class and "nice" value.
4519 * We want to under-estimate the load of migration sources, to
4520 * balance conservatively.
4522 static unsigned long source_load(int cpu, int type)
4524 struct rq *rq = cpu_rq(cpu);
4525 unsigned long total = weighted_cpuload(cpu);
4527 if (type == 0 || !sched_feat(LB_BIAS))
4530 return min(rq->cpu_load[type-1], total);
4534 * Return a high guess at the load of a migration-target cpu weighted
4535 * according to the scheduling class and "nice" value.
4537 static unsigned long target_load(int cpu, int type)
4539 struct rq *rq = cpu_rq(cpu);
4540 unsigned long total = weighted_cpuload(cpu);
4542 if (type == 0 || !sched_feat(LB_BIAS))
4545 return max(rq->cpu_load[type-1], total);
4549 static unsigned long cpu_avg_load_per_task(int cpu)
4551 struct rq *rq = cpu_rq(cpu);
4552 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4553 unsigned long load_avg = weighted_cpuload(cpu);
4556 return load_avg / nr_running;
4561 static void record_wakee(struct task_struct *p)
4564 * Rough decay (wiping) for cost saving, don't worry
4565 * about the boundary, really active task won't care
4568 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4569 current->wakee_flips >>= 1;
4570 current->wakee_flip_decay_ts = jiffies;
4573 if (current->last_wakee != p) {
4574 current->last_wakee = p;
4575 current->wakee_flips++;
4579 static void task_waking_fair(struct task_struct *p)
4581 struct sched_entity *se = &p->se;
4582 struct cfs_rq *cfs_rq = cfs_rq_of(se);
4585 #ifndef CONFIG_64BIT
4586 u64 min_vruntime_copy;
4589 min_vruntime_copy = cfs_rq->min_vruntime_copy;
4591 min_vruntime = cfs_rq->min_vruntime;
4592 } while (min_vruntime != min_vruntime_copy);
4594 min_vruntime = cfs_rq->min_vruntime;
4597 se->vruntime -= min_vruntime;
4601 #ifdef CONFIG_FAIR_GROUP_SCHED
4603 * effective_load() calculates the load change as seen from the root_task_group
4605 * Adding load to a group doesn't make a group heavier, but can cause movement
4606 * of group shares between cpus. Assuming the shares were perfectly aligned one
4607 * can calculate the shift in shares.
4609 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4610 * on this @cpu and results in a total addition (subtraction) of @wg to the
4611 * total group weight.
4613 * Given a runqueue weight distribution (rw_i) we can compute a shares
4614 * distribution (s_i) using:
4616 * s_i = rw_i / \Sum rw_j (1)
4618 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4619 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4620 * shares distribution (s_i):
4622 * rw_i = { 2, 4, 1, 0 }
4623 * s_i = { 2/7, 4/7, 1/7, 0 }
4625 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4626 * task used to run on and the CPU the waker is running on), we need to
4627 * compute the effect of waking a task on either CPU and, in case of a sync
4628 * wakeup, compute the effect of the current task going to sleep.
4630 * So for a change of @wl to the local @cpu with an overall group weight change
4631 * of @wl we can compute the new shares distribution (s'_i) using:
4633 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4635 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4636 * differences in waking a task to CPU 0. The additional task changes the
4637 * weight and shares distributions like:
4639 * rw'_i = { 3, 4, 1, 0 }
4640 * s'_i = { 3/8, 4/8, 1/8, 0 }
4642 * We can then compute the difference in effective weight by using:
4644 * dw_i = S * (s'_i - s_i) (3)
4646 * Where 'S' is the group weight as seen by its parent.
4648 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4649 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4650 * 4/7) times the weight of the group.
4652 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4654 struct sched_entity *se = tg->se[cpu];
4656 if (!tg->parent) /* the trivial, non-cgroup case */
4659 for_each_sched_entity(se) {
4660 struct cfs_rq *cfs_rq = se->my_q;
4661 long W, w = cfs_rq_load_avg(cfs_rq);
4666 * W = @wg + \Sum rw_j
4668 W = wg + atomic_long_read(&tg->load_avg);
4670 /* Ensure \Sum rw_j >= rw_i */
4671 W -= cfs_rq->tg_load_avg_contrib;
4680 * wl = S * s'_i; see (2)
4683 wl = (w * (long)tg->shares) / W;
4688 * Per the above, wl is the new se->load.weight value; since
4689 * those are clipped to [MIN_SHARES, ...) do so now. See
4690 * calc_cfs_shares().
4692 if (wl < MIN_SHARES)
4696 * wl = dw_i = S * (s'_i - s_i); see (3)
4698 wl -= se->avg.load_avg;
4701 * Recursively apply this logic to all parent groups to compute
4702 * the final effective load change on the root group. Since
4703 * only the @tg group gets extra weight, all parent groups can
4704 * only redistribute existing shares. @wl is the shift in shares
4705 * resulting from this level per the above.
4714 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4721 static inline bool energy_aware(void)
4723 return sched_feat(ENERGY_AWARE);
4727 struct sched_group *sg_top;
4728 struct sched_group *sg_cap;
4735 struct task_struct *task;
4750 * __cpu_norm_util() returns the cpu util relative to a specific capacity,
4751 * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for
4752 * energy calculations. Using the scale-invariant util returned by
4753 * cpu_util() and approximating scale-invariant util by:
4755 * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time
4757 * the normalized util can be found using the specific capacity.
4759 * capacity = capacity_orig * curr_freq/max_freq
4761 * norm_util = running_time/time ~ util/capacity
4763 static unsigned long __cpu_norm_util(int cpu, unsigned long capacity, int delta)
4765 int util = __cpu_util(cpu, delta);
4767 if (util >= capacity)
4768 return SCHED_CAPACITY_SCALE;
4770 return (util << SCHED_CAPACITY_SHIFT)/capacity;
4773 static int calc_util_delta(struct energy_env *eenv, int cpu)
4775 if (cpu == eenv->src_cpu)
4776 return -eenv->util_delta;
4777 if (cpu == eenv->dst_cpu)
4778 return eenv->util_delta;
4783 unsigned long group_max_util(struct energy_env *eenv)
4786 unsigned long max_util = 0;
4788 for_each_cpu(i, sched_group_cpus(eenv->sg_cap)) {
4789 delta = calc_util_delta(eenv, i);
4790 max_util = max(max_util, __cpu_util(i, delta));
4797 * group_norm_util() returns the approximated group util relative to it's
4798 * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in
4799 * energy calculations. Since task executions may or may not overlap in time in
4800 * the group the true normalized util is between max(cpu_norm_util(i)) and
4801 * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The
4802 * latter is used as the estimate as it leads to a more pessimistic energy
4803 * estimate (more busy).
4806 long group_norm_util(struct energy_env *eenv, struct sched_group *sg)
4809 unsigned long util_sum = 0;
4810 unsigned long capacity = sg->sge->cap_states[eenv->cap_idx].cap;
4812 for_each_cpu(i, sched_group_cpus(sg)) {
4813 delta = calc_util_delta(eenv, i);
4814 util_sum += __cpu_norm_util(i, capacity, delta);
4817 if (util_sum > SCHED_CAPACITY_SCALE)
4818 return SCHED_CAPACITY_SCALE;
4822 static int find_new_capacity(struct energy_env *eenv,
4823 const struct sched_group_energy const *sge)
4826 unsigned long util = group_max_util(eenv);
4828 for (idx = 0; idx < sge->nr_cap_states; idx++) {
4829 if (sge->cap_states[idx].cap >= util)
4833 eenv->cap_idx = idx;
4838 static int group_idle_state(struct sched_group *sg)
4840 int i, state = INT_MAX;
4842 /* Find the shallowest idle state in the sched group. */
4843 for_each_cpu(i, sched_group_cpus(sg))
4844 state = min(state, idle_get_state_idx(cpu_rq(i)));
4846 /* Take non-cpuidle idling into account (active idle/arch_cpu_idle()) */
4853 * sched_group_energy(): Computes the absolute energy consumption of cpus
4854 * belonging to the sched_group including shared resources shared only by
4855 * members of the group. Iterates over all cpus in the hierarchy below the
4856 * sched_group starting from the bottom working it's way up before going to
4857 * the next cpu until all cpus are covered at all levels. The current
4858 * implementation is likely to gather the same util statistics multiple times.
4859 * This can probably be done in a faster but more complex way.
4860 * Note: sched_group_energy() may fail when racing with sched_domain updates.
4862 static int sched_group_energy(struct energy_env *eenv)
4864 struct sched_domain *sd;
4865 int cpu, total_energy = 0;
4866 struct cpumask visit_cpus;
4867 struct sched_group *sg;
4869 WARN_ON(!eenv->sg_top->sge);
4871 cpumask_copy(&visit_cpus, sched_group_cpus(eenv->sg_top));
4873 while (!cpumask_empty(&visit_cpus)) {
4874 struct sched_group *sg_shared_cap = NULL;
4876 cpu = cpumask_first(&visit_cpus);
4879 * Is the group utilization affected by cpus outside this
4882 sd = rcu_dereference(per_cpu(sd_scs, cpu));
4886 * We most probably raced with hotplug; returning a
4887 * wrong energy estimation is better than entering an
4893 sg_shared_cap = sd->parent->groups;
4895 for_each_domain(cpu, sd) {
4898 /* Has this sched_domain already been visited? */
4899 if (sd->child && group_first_cpu(sg) != cpu)
4903 unsigned long group_util;
4904 int sg_busy_energy, sg_idle_energy;
4905 int cap_idx, idle_idx;
4907 if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight)
4908 eenv->sg_cap = sg_shared_cap;
4912 cap_idx = find_new_capacity(eenv, sg->sge);
4914 if (sg->group_weight == 1) {
4915 /* Remove capacity of src CPU (before task move) */
4916 if (eenv->util_delta == 0 &&
4917 cpumask_test_cpu(eenv->src_cpu, sched_group_cpus(sg))) {
4918 eenv->cap.before = sg->sge->cap_states[cap_idx].cap;
4919 eenv->cap.delta -= eenv->cap.before;
4921 /* Add capacity of dst CPU (after task move) */
4922 if (eenv->util_delta != 0 &&
4923 cpumask_test_cpu(eenv->dst_cpu, sched_group_cpus(sg))) {
4924 eenv->cap.after = sg->sge->cap_states[cap_idx].cap;
4925 eenv->cap.delta += eenv->cap.after;
4929 idle_idx = group_idle_state(sg);
4930 group_util = group_norm_util(eenv, sg);
4931 sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power)
4932 >> SCHED_CAPACITY_SHIFT;
4933 sg_idle_energy = ((SCHED_LOAD_SCALE-group_util)
4934 * sg->sge->idle_states[idle_idx].power)
4935 >> SCHED_CAPACITY_SHIFT;
4937 total_energy += sg_busy_energy + sg_idle_energy;
4940 cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg));
4942 if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(eenv->sg_top)))
4945 } while (sg = sg->next, sg != sd->groups);
4951 eenv->energy = total_energy;
4955 static inline bool cpu_in_sg(struct sched_group *sg, int cpu)
4957 return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));
4960 #ifdef CONFIG_SCHED_TUNE
4961 static int energy_diff_evaluate(struct energy_env *eenv)
4966 /* Return energy diff when boost margin is 0 */
4967 #ifdef CONFIG_CGROUP_SCHEDTUNE
4968 boost = schedtune_task_boost(eenv->task);
4970 boost = get_sysctl_sched_cfs_boost();
4973 return eenv->nrg.diff;
4975 /* Compute normalized energy diff */
4976 nrg_delta = schedtune_normalize_energy(eenv->nrg.diff);
4977 eenv->nrg.delta = nrg_delta;
4979 eenv->payoff = schedtune_accept_deltas(
4985 * When SchedTune is enabled, the energy_diff() function will return
4986 * the computed energy payoff value. Since the energy_diff() return
4987 * value is expected to be negative by its callers, this evaluation
4988 * function return a negative value each time the evaluation return a
4989 * positive payoff, which is the condition for the acceptance of
4990 * a scheduling decision
4992 return -eenv->payoff;
4994 #else /* CONFIG_SCHED_TUNE */
4995 #define energy_diff_evaluate(eenv) eenv->nrg.diff
4999 * energy_diff(): Estimate the energy impact of changing the utilization
5000 * distribution. eenv specifies the change: utilisation amount, source, and
5001 * destination cpu. Source or destination cpu may be -1 in which case the
5002 * utilization is removed from or added to the system (e.g. task wake-up). If
5003 * both are specified, the utilization is migrated.
5005 static int energy_diff(struct energy_env *eenv)
5007 struct sched_domain *sd;
5008 struct sched_group *sg;
5009 int sd_cpu = -1, energy_before = 0, energy_after = 0;
5011 struct energy_env eenv_before = {
5013 .src_cpu = eenv->src_cpu,
5014 .dst_cpu = eenv->dst_cpu,
5015 .nrg = { 0, 0, 0, 0},
5019 if (eenv->src_cpu == eenv->dst_cpu)
5022 sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;
5023 sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));
5026 return 0; /* Error */
5031 if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {
5032 eenv_before.sg_top = eenv->sg_top = sg;
5034 if (sched_group_energy(&eenv_before))
5035 return 0; /* Invalid result abort */
5036 energy_before += eenv_before.energy;
5038 /* Keep track of SRC cpu (before) capacity */
5039 eenv->cap.before = eenv_before.cap.before;
5040 eenv->cap.delta = eenv_before.cap.delta;
5042 if (sched_group_energy(eenv))
5043 return 0; /* Invalid result abort */
5044 energy_after += eenv->energy;
5046 } while (sg = sg->next, sg != sd->groups);
5048 eenv->nrg.before = energy_before;
5049 eenv->nrg.after = energy_after;
5050 eenv->nrg.diff = eenv->nrg.after - eenv->nrg.before;
5053 return energy_diff_evaluate(eenv);
5057 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5058 * A waker of many should wake a different task than the one last awakened
5059 * at a frequency roughly N times higher than one of its wakees. In order
5060 * to determine whether we should let the load spread vs consolodating to
5061 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
5062 * partner, and a factor of lls_size higher frequency in the other. With
5063 * both conditions met, we can be relatively sure that the relationship is
5064 * non-monogamous, with partner count exceeding socket size. Waker/wakee
5065 * being client/server, worker/dispatcher, interrupt source or whatever is
5066 * irrelevant, spread criteria is apparent partner count exceeds socket size.
5068 static int wake_wide(struct task_struct *p)
5070 unsigned int master = current->wakee_flips;
5071 unsigned int slave = p->wakee_flips;
5072 int factor = this_cpu_read(sd_llc_size);
5075 swap(master, slave);
5076 if (slave < factor || master < slave * factor)
5081 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
5083 s64 this_load, load;
5084 s64 this_eff_load, prev_eff_load;
5085 int idx, this_cpu, prev_cpu;
5086 struct task_group *tg;
5087 unsigned long weight;
5091 this_cpu = smp_processor_id();
5092 prev_cpu = task_cpu(p);
5093 load = source_load(prev_cpu, idx);
5094 this_load = target_load(this_cpu, idx);
5097 * If sync wakeup then subtract the (maximum possible)
5098 * effect of the currently running task from the load
5099 * of the current CPU:
5102 tg = task_group(current);
5103 weight = current->se.avg.load_avg;
5105 this_load += effective_load(tg, this_cpu, -weight, -weight);
5106 load += effective_load(tg, prev_cpu, 0, -weight);
5110 weight = p->se.avg.load_avg;
5113 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5114 * due to the sync cause above having dropped this_load to 0, we'll
5115 * always have an imbalance, but there's really nothing you can do
5116 * about that, so that's good too.
5118 * Otherwise check if either cpus are near enough in load to allow this
5119 * task to be woken on this_cpu.
5121 this_eff_load = 100;
5122 this_eff_load *= capacity_of(prev_cpu);
5124 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
5125 prev_eff_load *= capacity_of(this_cpu);
5127 if (this_load > 0) {
5128 this_eff_load *= this_load +
5129 effective_load(tg, this_cpu, weight, weight);
5131 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5134 balanced = this_eff_load <= prev_eff_load;
5136 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5141 schedstat_inc(sd, ttwu_move_affine);
5142 schedstat_inc(p, se.statistics.nr_wakeups_affine);
5147 static inline unsigned long task_util(struct task_struct *p)
5149 return p->se.avg.util_avg;
5152 unsigned int capacity_margin = 1280; /* ~20% margin */
5154 static inline unsigned long boosted_task_util(struct task_struct *task);
5156 static inline bool __task_fits(struct task_struct *p, int cpu, int util)
5158 unsigned long capacity = capacity_of(cpu);
5160 util += boosted_task_util(p);
5162 return (capacity * 1024) > (util * capacity_margin);
5165 static inline bool task_fits_max(struct task_struct *p, int cpu)
5167 unsigned long capacity = capacity_of(cpu);
5168 unsigned long max_capacity = cpu_rq(cpu)->rd->max_cpu_capacity.val;
5170 if (capacity == max_capacity)
5173 if (capacity * capacity_margin > max_capacity * 1024)
5176 return __task_fits(p, cpu, 0);
5179 static inline bool task_fits_spare(struct task_struct *p, int cpu)
5181 return __task_fits(p, cpu, cpu_util(cpu));
5184 static bool cpu_overutilized(int cpu)
5186 return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
5189 #ifdef CONFIG_SCHED_TUNE
5191 static unsigned long
5192 schedtune_margin(unsigned long signal, unsigned long boost)
5194 unsigned long long margin = 0;
5197 * Signal proportional compensation (SPC)
5199 * The Boost (B) value is used to compute a Margin (M) which is
5200 * proportional to the complement of the original Signal (S):
5201 * M = B * (SCHED_LOAD_SCALE - S)
5202 * The obtained M could be used by the caller to "boost" S.
5204 margin = SCHED_LOAD_SCALE - signal;
5208 * Fast integer division by constant:
5209 * Constant : (C) = 100
5210 * Precision : 0.1% (P) = 0.1
5211 * Reference : C * 100 / P (R) = 100000
5214 * Shift bits : ceil(log(R,2)) (S) = 17
5215 * Mult const : round(2^S/C) (M) = 1311
5225 static inline unsigned int
5226 schedtune_cpu_margin(unsigned long util, int cpu)
5230 #ifdef CONFIG_CGROUP_SCHEDTUNE
5231 boost = schedtune_cpu_boost(cpu);
5233 boost = get_sysctl_sched_cfs_boost();
5238 return schedtune_margin(util, boost);
5241 static inline unsigned long
5242 schedtune_task_margin(struct task_struct *task)
5246 unsigned long margin;
5248 #ifdef CONFIG_CGROUP_SCHEDTUNE
5249 boost = schedtune_task_boost(task);
5251 boost = get_sysctl_sched_cfs_boost();
5256 util = task_util(task);
5257 margin = schedtune_margin(util, boost);
5262 #else /* CONFIG_SCHED_TUNE */
5264 static inline unsigned int
5265 schedtune_cpu_margin(unsigned long util, int cpu)
5270 static inline unsigned int
5271 schedtune_task_margin(struct task_struct *task)
5276 #endif /* CONFIG_SCHED_TUNE */
5278 static inline unsigned long
5279 boosted_cpu_util(int cpu)
5281 unsigned long util = cpu_util(cpu);
5282 unsigned long margin = schedtune_cpu_margin(util, cpu);
5284 return util + margin;
5287 static inline unsigned long
5288 boosted_task_util(struct task_struct *task)
5290 unsigned long util = task_util(task);
5291 unsigned long margin = schedtune_task_margin(task);
5293 return util + margin;
5297 * find_idlest_group finds and returns the least busy CPU group within the
5300 static struct sched_group *
5301 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5302 int this_cpu, int sd_flag)
5304 struct sched_group *idlest = NULL, *group = sd->groups;
5305 struct sched_group *fit_group = NULL, *spare_group = NULL;
5306 unsigned long min_load = ULONG_MAX, this_load = 0;
5307 unsigned long fit_capacity = ULONG_MAX;
5308 unsigned long max_spare_capacity = capacity_margin - SCHED_LOAD_SCALE;
5309 int load_idx = sd->forkexec_idx;
5310 int imbalance = 100 + (sd->imbalance_pct-100)/2;
5312 if (sd_flag & SD_BALANCE_WAKE)
5313 load_idx = sd->wake_idx;
5316 unsigned long load, avg_load, spare_capacity;
5320 /* Skip over this group if it has no CPUs allowed */
5321 if (!cpumask_intersects(sched_group_cpus(group),
5322 tsk_cpus_allowed(p)))
5325 local_group = cpumask_test_cpu(this_cpu,
5326 sched_group_cpus(group));
5328 /* Tally up the load of all CPUs in the group */
5331 for_each_cpu(i, sched_group_cpus(group)) {
5332 /* Bias balancing toward cpus of our domain */
5334 load = source_load(i, load_idx);
5336 load = target_load(i, load_idx);
5341 * Look for most energy-efficient group that can fit
5342 * that can fit the task.
5344 if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
5345 fit_capacity = capacity_of(i);
5350 * Look for group which has most spare capacity on a
5353 spare_capacity = capacity_of(i) - cpu_util(i);
5354 if (spare_capacity > max_spare_capacity) {
5355 max_spare_capacity = spare_capacity;
5356 spare_group = group;
5360 /* Adjust by relative CPU capacity of the group */
5361 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5364 this_load = avg_load;
5365 } else if (avg_load < min_load) {
5366 min_load = avg_load;
5369 } while (group = group->next, group != sd->groups);
5377 if (!idlest || 100*this_load < imbalance*min_load)
5383 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5386 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5388 unsigned long load, min_load = ULONG_MAX;
5389 unsigned int min_exit_latency = UINT_MAX;
5390 u64 latest_idle_timestamp = 0;
5391 int least_loaded_cpu = this_cpu;
5392 int shallowest_idle_cpu = -1;
5395 /* Traverse only the allowed CPUs */
5396 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5397 if (task_fits_spare(p, i)) {
5398 struct rq *rq = cpu_rq(i);
5399 struct cpuidle_state *idle = idle_get_state(rq);
5400 if (idle && idle->exit_latency < min_exit_latency) {
5402 * We give priority to a CPU whose idle state
5403 * has the smallest exit latency irrespective
5404 * of any idle timestamp.
5406 min_exit_latency = idle->exit_latency;
5407 latest_idle_timestamp = rq->idle_stamp;
5408 shallowest_idle_cpu = i;
5409 } else if (idle_cpu(i) &&
5410 (!idle || idle->exit_latency == min_exit_latency) &&
5411 rq->idle_stamp > latest_idle_timestamp) {
5413 * If equal or no active idle state, then
5414 * the most recently idled CPU might have
5417 latest_idle_timestamp = rq->idle_stamp;
5418 shallowest_idle_cpu = i;
5419 } else if (shallowest_idle_cpu == -1) {
5421 * If we haven't found an idle CPU yet
5422 * pick a non-idle one that can fit the task as
5425 shallowest_idle_cpu = i;
5427 } else if (shallowest_idle_cpu == -1) {
5428 load = weighted_cpuload(i);
5429 if (load < min_load || (load == min_load && i == this_cpu)) {
5431 least_loaded_cpu = i;
5436 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5440 * Try and locate an idle CPU in the sched_domain.
5442 static int select_idle_sibling(struct task_struct *p, int target)
5444 struct sched_domain *sd;
5445 struct sched_group *sg;
5446 int i = task_cpu(p);
5448 if (idle_cpu(target))
5452 * If the prevous cpu is cache affine and idle, don't be stupid.
5454 if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
5458 * Otherwise, iterate the domains and find an elegible idle cpu.
5460 sd = rcu_dereference(per_cpu(sd_llc, target));
5461 for_each_lower_domain(sd) {
5464 if (!cpumask_intersects(sched_group_cpus(sg),
5465 tsk_cpus_allowed(p)))
5468 for_each_cpu(i, sched_group_cpus(sg)) {
5469 if (i == target || !idle_cpu(i))
5473 target = cpumask_first_and(sched_group_cpus(sg),
5474 tsk_cpus_allowed(p));
5478 } while (sg != sd->groups);
5484 static int energy_aware_wake_cpu(struct task_struct *p, int target)
5486 struct sched_domain *sd;
5487 struct sched_group *sg, *sg_target;
5488 int target_max_cap = INT_MAX;
5489 int target_cpu = task_cpu(p);
5492 sd = rcu_dereference(per_cpu(sd_ea, task_cpu(p)));
5501 * Find group with sufficient capacity. We only get here if no cpu is
5502 * overutilized. We may end up overutilizing a cpu by adding the task,
5503 * but that should not be any worse than select_idle_sibling().
5504 * load_balance() should sort it out later as we get above the tipping
5508 /* Assuming all cpus are the same in group */
5509 int max_cap_cpu = group_first_cpu(sg);
5512 * Assume smaller max capacity means more energy-efficient.
5513 * Ideally we should query the energy model for the right
5514 * answer but it easily ends up in an exhaustive search.
5516 if (capacity_of(max_cap_cpu) < target_max_cap &&
5517 task_fits_max(p, max_cap_cpu)) {
5519 target_max_cap = capacity_of(max_cap_cpu);
5521 } while (sg = sg->next, sg != sd->groups);
5523 /* Find cpu with sufficient capacity */
5524 for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg_target)) {
5526 * p's blocked utilization is still accounted for on prev_cpu
5527 * so prev_cpu will receive a negative bias due to the double
5528 * accounting. However, the blocked utilization may be zero.
5530 int new_util = cpu_util(i) + boosted_task_util(p);
5532 if (new_util > capacity_orig_of(i))
5535 if (new_util < capacity_curr_of(i)) {
5537 if (cpu_rq(i)->nr_running)
5541 /* cpu has capacity at higher OPP, keep it as fallback */
5542 if (target_cpu == task_cpu(p))
5546 if (target_cpu != task_cpu(p)) {
5547 struct energy_env eenv = {
5548 .util_delta = task_util(p),
5549 .src_cpu = task_cpu(p),
5550 .dst_cpu = target_cpu,
5554 /* Not enough spare capacity on previous cpu */
5555 if (cpu_overutilized(task_cpu(p)))
5558 if (energy_diff(&eenv) >= 0)
5566 * select_task_rq_fair: Select target runqueue for the waking task in domains
5567 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5568 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5570 * Balances load by selecting the idlest cpu in the idlest group, or under
5571 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5573 * Returns the target cpu number.
5575 * preempt must be disabled.
5578 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5580 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5581 int cpu = smp_processor_id();
5582 int new_cpu = prev_cpu;
5583 int want_affine = 0;
5584 int sync = wake_flags & WF_SYNC;
5586 if (sd_flag & SD_BALANCE_WAKE)
5587 want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
5588 cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
5592 for_each_domain(cpu, tmp) {
5593 if (!(tmp->flags & SD_LOAD_BALANCE))
5597 * If both cpu and prev_cpu are part of this domain,
5598 * cpu is a valid SD_WAKE_AFFINE target.
5600 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
5601 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
5606 if (tmp->flags & sd_flag)
5608 else if (!want_affine)
5613 sd = NULL; /* Prefer wake_affine over balance flags */
5614 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
5619 if (energy_aware() && !cpu_rq(cpu)->rd->overutilized)
5620 new_cpu = energy_aware_wake_cpu(p, prev_cpu);
5621 else if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5622 new_cpu = select_idle_sibling(p, new_cpu);
5625 struct sched_group *group;
5628 if (!(sd->flags & sd_flag)) {
5633 group = find_idlest_group(sd, p, cpu, sd_flag);
5639 new_cpu = find_idlest_cpu(group, p, cpu);
5640 if (new_cpu == -1 || new_cpu == cpu) {
5641 /* Now try balancing at a lower domain level of cpu */
5646 /* Now try balancing at a lower domain level of new_cpu */
5648 weight = sd->span_weight;
5650 for_each_domain(cpu, tmp) {
5651 if (weight <= tmp->span_weight)
5653 if (tmp->flags & sd_flag)
5656 /* while loop will break here if sd == NULL */
5664 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5665 * cfs_rq_of(p) references at time of call are still valid and identify the
5666 * previous cpu. However, the caller only guarantees p->pi_lock is held; no
5667 * other assumptions, including the state of rq->lock, should be made.
5669 static void migrate_task_rq_fair(struct task_struct *p)
5672 * We are supposed to update the task to "current" time, then its up to date
5673 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5674 * what current time is, so simply throw away the out-of-date time. This
5675 * will result in the wakee task is less decayed, but giving the wakee more
5676 * load sounds not bad.
5678 remove_entity_load_avg(&p->se);
5680 /* Tell new CPU we are migrated */
5681 p->se.avg.last_update_time = 0;
5683 /* We have migrated, no longer consider this task hot */
5684 p->se.exec_start = 0;
5687 static void task_dead_fair(struct task_struct *p)
5689 remove_entity_load_avg(&p->se);
5691 #endif /* CONFIG_SMP */
5693 static unsigned long
5694 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5696 unsigned long gran = sysctl_sched_wakeup_granularity;
5699 * Since its curr running now, convert the gran from real-time
5700 * to virtual-time in his units.
5702 * By using 'se' instead of 'curr' we penalize light tasks, so
5703 * they get preempted easier. That is, if 'se' < 'curr' then
5704 * the resulting gran will be larger, therefore penalizing the
5705 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5706 * be smaller, again penalizing the lighter task.
5708 * This is especially important for buddies when the leftmost
5709 * task is higher priority than the buddy.
5711 return calc_delta_fair(gran, se);
5715 * Should 'se' preempt 'curr'.
5729 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
5731 s64 gran, vdiff = curr->vruntime - se->vruntime;
5736 gran = wakeup_gran(curr, se);
5743 static void set_last_buddy(struct sched_entity *se)
5745 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5748 for_each_sched_entity(se)
5749 cfs_rq_of(se)->last = se;
5752 static void set_next_buddy(struct sched_entity *se)
5754 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
5757 for_each_sched_entity(se)
5758 cfs_rq_of(se)->next = se;
5761 static void set_skip_buddy(struct sched_entity *se)
5763 for_each_sched_entity(se)
5764 cfs_rq_of(se)->skip = se;
5768 * Preempt the current task with a newly woken task if needed:
5770 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5772 struct task_struct *curr = rq->curr;
5773 struct sched_entity *se = &curr->se, *pse = &p->se;
5774 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5775 int scale = cfs_rq->nr_running >= sched_nr_latency;
5776 int next_buddy_marked = 0;
5778 if (unlikely(se == pse))
5782 * This is possible from callers such as attach_tasks(), in which we
5783 * unconditionally check_prempt_curr() after an enqueue (which may have
5784 * lead to a throttle). This both saves work and prevents false
5785 * next-buddy nomination below.
5787 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
5790 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
5791 set_next_buddy(pse);
5792 next_buddy_marked = 1;
5796 * We can come here with TIF_NEED_RESCHED already set from new task
5799 * Note: this also catches the edge-case of curr being in a throttled
5800 * group (e.g. via set_curr_task), since update_curr() (in the
5801 * enqueue of curr) will have resulted in resched being set. This
5802 * prevents us from potentially nominating it as a false LAST_BUDDY
5805 if (test_tsk_need_resched(curr))
5808 /* Idle tasks are by definition preempted by non-idle tasks. */
5809 if (unlikely(curr->policy == SCHED_IDLE) &&
5810 likely(p->policy != SCHED_IDLE))
5814 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5815 * is driven by the tick):
5817 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5820 find_matching_se(&se, &pse);
5821 update_curr(cfs_rq_of(se));
5823 if (wakeup_preempt_entity(se, pse) == 1) {
5825 * Bias pick_next to pick the sched entity that is
5826 * triggering this preemption.
5828 if (!next_buddy_marked)
5829 set_next_buddy(pse);
5838 * Only set the backward buddy when the current task is still
5839 * on the rq. This can happen when a wakeup gets interleaved
5840 * with schedule on the ->pre_schedule() or idle_balance()
5841 * point, either of which can * drop the rq lock.
5843 * Also, during early boot the idle thread is in the fair class,
5844 * for obvious reasons its a bad idea to schedule back to it.
5846 if (unlikely(!se->on_rq || curr == rq->idle))
5849 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
5853 static struct task_struct *
5854 pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5856 struct cfs_rq *cfs_rq = &rq->cfs;
5857 struct sched_entity *se;
5858 struct task_struct *p;
5862 #ifdef CONFIG_FAIR_GROUP_SCHED
5863 if (!cfs_rq->nr_running)
5866 if (prev->sched_class != &fair_sched_class)
5870 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5871 * likely that a next task is from the same cgroup as the current.
5873 * Therefore attempt to avoid putting and setting the entire cgroup
5874 * hierarchy, only change the part that actually changes.
5878 struct sched_entity *curr = cfs_rq->curr;
5881 * Since we got here without doing put_prev_entity() we also
5882 * have to consider cfs_rq->curr. If it is still a runnable
5883 * entity, update_curr() will update its vruntime, otherwise
5884 * forget we've ever seen it.
5888 update_curr(cfs_rq);
5893 * This call to check_cfs_rq_runtime() will do the
5894 * throttle and dequeue its entity in the parent(s).
5895 * Therefore the 'simple' nr_running test will indeed
5898 if (unlikely(check_cfs_rq_runtime(cfs_rq)))
5902 se = pick_next_entity(cfs_rq, curr);
5903 cfs_rq = group_cfs_rq(se);
5909 * Since we haven't yet done put_prev_entity and if the selected task
5910 * is a different task than we started out with, try and touch the
5911 * least amount of cfs_rqs.
5914 struct sched_entity *pse = &prev->se;
5916 while (!(cfs_rq = is_same_group(se, pse))) {
5917 int se_depth = se->depth;
5918 int pse_depth = pse->depth;
5920 if (se_depth <= pse_depth) {
5921 put_prev_entity(cfs_rq_of(pse), pse);
5922 pse = parent_entity(pse);
5924 if (se_depth >= pse_depth) {
5925 set_next_entity(cfs_rq_of(se), se);
5926 se = parent_entity(se);
5930 put_prev_entity(cfs_rq, pse);
5931 set_next_entity(cfs_rq, se);
5934 if (hrtick_enabled(rq))
5935 hrtick_start_fair(rq, p);
5937 rq->misfit_task = !task_fits_max(p, rq->cpu);
5944 if (!cfs_rq->nr_running)
5947 put_prev_task(rq, prev);
5950 se = pick_next_entity(cfs_rq, NULL);
5951 set_next_entity(cfs_rq, se);
5952 cfs_rq = group_cfs_rq(se);
5957 if (hrtick_enabled(rq))
5958 hrtick_start_fair(rq, p);
5960 rq->misfit_task = !task_fits_max(p, rq->cpu);
5965 rq->misfit_task = 0;
5967 * This is OK, because current is on_cpu, which avoids it being picked
5968 * for load-balance and preemption/IRQs are still disabled avoiding
5969 * further scheduler activity on it and we're being very careful to
5970 * re-start the picking loop.
5972 lockdep_unpin_lock(&rq->lock);
5973 new_tasks = idle_balance(rq);
5974 lockdep_pin_lock(&rq->lock);
5976 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5977 * possible for any higher priority task to appear. In that case we
5978 * must re-start the pick_next_entity() loop.
5990 * Account for a descheduled task:
5992 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5994 struct sched_entity *se = &prev->se;
5995 struct cfs_rq *cfs_rq;
5997 for_each_sched_entity(se) {
5998 cfs_rq = cfs_rq_of(se);
5999 put_prev_entity(cfs_rq, se);
6004 * sched_yield() is very simple
6006 * The magic of dealing with the ->skip buddy is in pick_next_entity.
6008 static void yield_task_fair(struct rq *rq)
6010 struct task_struct *curr = rq->curr;
6011 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6012 struct sched_entity *se = &curr->se;
6015 * Are we the only task in the tree?
6017 if (unlikely(rq->nr_running == 1))
6020 clear_buddies(cfs_rq, se);
6022 if (curr->policy != SCHED_BATCH) {
6023 update_rq_clock(rq);
6025 * Update run-time statistics of the 'current'.
6027 update_curr(cfs_rq);
6029 * Tell update_rq_clock() that we've just updated,
6030 * so we don't do microscopic update in schedule()
6031 * and double the fastpath cost.
6033 rq_clock_skip_update(rq, true);
6039 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
6041 struct sched_entity *se = &p->se;
6043 /* throttled hierarchies are not runnable */
6044 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6047 /* Tell the scheduler that we'd really like pse to run next. */
6050 yield_task_fair(rq);
6056 /**************************************************
6057 * Fair scheduling class load-balancing methods.
6061 * The purpose of load-balancing is to achieve the same basic fairness the
6062 * per-cpu scheduler provides, namely provide a proportional amount of compute
6063 * time to each task. This is expressed in the following equation:
6065 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
6067 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
6068 * W_i,0 is defined as:
6070 * W_i,0 = \Sum_j w_i,j (2)
6072 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
6073 * is derived from the nice value as per prio_to_weight[].
6075 * The weight average is an exponential decay average of the instantaneous
6078 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
6080 * C_i is the compute capacity of cpu i, typically it is the
6081 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
6082 * can also include other factors [XXX].
6084 * To achieve this balance we define a measure of imbalance which follows
6085 * directly from (1):
6087 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
6089 * We them move tasks around to minimize the imbalance. In the continuous
6090 * function space it is obvious this converges, in the discrete case we get
6091 * a few fun cases generally called infeasible weight scenarios.
6094 * - infeasible weights;
6095 * - local vs global optima in the discrete case. ]
6100 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6101 * for all i,j solution, we create a tree of cpus that follows the hardware
6102 * topology where each level pairs two lower groups (or better). This results
6103 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
6104 * tree to only the first of the previous level and we decrease the frequency
6105 * of load-balance at each level inv. proportional to the number of cpus in
6111 * \Sum { --- * --- * 2^i } = O(n) (5)
6113 * `- size of each group
6114 * | | `- number of cpus doing load-balance
6116 * `- sum over all levels
6118 * Coupled with a limit on how many tasks we can migrate every balance pass,
6119 * this makes (5) the runtime complexity of the balancer.
6121 * An important property here is that each CPU is still (indirectly) connected
6122 * to every other cpu in at most O(log n) steps:
6124 * The adjacency matrix of the resulting graph is given by:
6127 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
6130 * And you'll find that:
6132 * A^(log_2 n)_i,j != 0 for all i,j (7)
6134 * Showing there's indeed a path between every cpu in at most O(log n) steps.
6135 * The task movement gives a factor of O(m), giving a convergence complexity
6138 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
6143 * In order to avoid CPUs going idle while there's still work to do, new idle
6144 * balancing is more aggressive and has the newly idle cpu iterate up the domain
6145 * tree itself instead of relying on other CPUs to bring it work.
6147 * This adds some complexity to both (5) and (8) but it reduces the total idle
6155 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6158 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6163 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6165 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6167 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6170 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6171 * rewrite all of this once again.]
6174 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
6176 enum fbq_type { regular, remote, all };
6185 #define LBF_ALL_PINNED 0x01
6186 #define LBF_NEED_BREAK 0x02
6187 #define LBF_DST_PINNED 0x04
6188 #define LBF_SOME_PINNED 0x08
6191 struct sched_domain *sd;
6199 struct cpumask *dst_grpmask;
6201 enum cpu_idle_type idle;
6203 unsigned int src_grp_nr_running;
6204 /* The set of CPUs under consideration for load-balancing */
6205 struct cpumask *cpus;
6210 unsigned int loop_break;
6211 unsigned int loop_max;
6213 enum fbq_type fbq_type;
6214 enum group_type busiest_group_type;
6215 struct list_head tasks;
6219 * Is this task likely cache-hot:
6221 static int task_hot(struct task_struct *p, struct lb_env *env)
6225 lockdep_assert_held(&env->src_rq->lock);
6227 if (p->sched_class != &fair_sched_class)
6230 if (unlikely(p->policy == SCHED_IDLE))
6234 * Buddy candidates are cache hot:
6236 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6237 (&p->se == cfs_rq_of(&p->se)->next ||
6238 &p->se == cfs_rq_of(&p->se)->last))
6241 if (sysctl_sched_migration_cost == -1)
6243 if (sysctl_sched_migration_cost == 0)
6246 delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6248 return delta < (s64)sysctl_sched_migration_cost;
6251 #ifdef CONFIG_NUMA_BALANCING
6253 * Returns 1, if task migration degrades locality
6254 * Returns 0, if task migration improves locality i.e migration preferred.
6255 * Returns -1, if task migration is not affected by locality.
6257 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6259 struct numa_group *numa_group = rcu_dereference(p->numa_group);
6260 unsigned long src_faults, dst_faults;
6261 int src_nid, dst_nid;
6263 if (!static_branch_likely(&sched_numa_balancing))
6266 if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6269 src_nid = cpu_to_node(env->src_cpu);
6270 dst_nid = cpu_to_node(env->dst_cpu);
6272 if (src_nid == dst_nid)
6275 /* Migrating away from the preferred node is always bad. */
6276 if (src_nid == p->numa_preferred_nid) {
6277 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
6283 /* Encourage migration to the preferred node. */
6284 if (dst_nid == p->numa_preferred_nid)
6288 src_faults = group_faults(p, src_nid);
6289 dst_faults = group_faults(p, dst_nid);
6291 src_faults = task_faults(p, src_nid);
6292 dst_faults = task_faults(p, dst_nid);
6295 return dst_faults < src_faults;
6299 static inline int migrate_degrades_locality(struct task_struct *p,
6307 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6310 int can_migrate_task(struct task_struct *p, struct lb_env *env)
6314 lockdep_assert_held(&env->src_rq->lock);
6317 * We do not migrate tasks that are:
6318 * 1) throttled_lb_pair, or
6319 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6320 * 3) running (obviously), or
6321 * 4) are cache-hot on their current CPU.
6323 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
6326 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6329 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6331 env->flags |= LBF_SOME_PINNED;
6334 * Remember if this task can be migrated to any other cpu in
6335 * our sched_group. We may want to revisit it if we couldn't
6336 * meet load balance goals by pulling other tasks on src_cpu.
6338 * Also avoid computing new_dst_cpu if we have already computed
6339 * one in current iteration.
6341 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6344 /* Prevent to re-select dst_cpu via env's cpus */
6345 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6346 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
6347 env->flags |= LBF_DST_PINNED;
6348 env->new_dst_cpu = cpu;
6356 /* Record that we found atleast one task that could run on dst_cpu */
6357 env->flags &= ~LBF_ALL_PINNED;
6359 if (task_running(env->src_rq, p)) {
6360 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6365 * Aggressive migration if:
6366 * 1) destination numa is preferred
6367 * 2) task is cache cold, or
6368 * 3) too many balance attempts have failed.
6370 tsk_cache_hot = migrate_degrades_locality(p, env);
6371 if (tsk_cache_hot == -1)
6372 tsk_cache_hot = task_hot(p, env);
6374 if (tsk_cache_hot <= 0 ||
6375 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6376 if (tsk_cache_hot == 1) {
6377 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
6378 schedstat_inc(p, se.statistics.nr_forced_migrations);
6383 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
6388 * detach_task() -- detach the task for the migration specified in env
6390 static void detach_task(struct task_struct *p, struct lb_env *env)
6392 lockdep_assert_held(&env->src_rq->lock);
6394 deactivate_task(env->src_rq, p, 0);
6395 p->on_rq = TASK_ON_RQ_MIGRATING;
6396 set_task_cpu(p, env->dst_cpu);
6400 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6401 * part of active balancing operations within "domain".
6403 * Returns a task if successful and NULL otherwise.
6405 static struct task_struct *detach_one_task(struct lb_env *env)
6407 struct task_struct *p, *n;
6409 lockdep_assert_held(&env->src_rq->lock);
6411 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
6412 if (!can_migrate_task(p, env))
6415 detach_task(p, env);
6418 * Right now, this is only the second place where
6419 * lb_gained[env->idle] is updated (other is detach_tasks)
6420 * so we can safely collect stats here rather than
6421 * inside detach_tasks().
6423 schedstat_inc(env->sd, lb_gained[env->idle]);
6429 static const unsigned int sched_nr_migrate_break = 32;
6432 * detach_tasks() -- tries to detach up to imbalance weighted load from
6433 * busiest_rq, as part of a balancing operation within domain "sd".
6435 * Returns number of detached tasks if successful and 0 otherwise.
6437 static int detach_tasks(struct lb_env *env)
6439 struct list_head *tasks = &env->src_rq->cfs_tasks;
6440 struct task_struct *p;
6444 lockdep_assert_held(&env->src_rq->lock);
6446 if (env->imbalance <= 0)
6449 while (!list_empty(tasks)) {
6451 * We don't want to steal all, otherwise we may be treated likewise,
6452 * which could at worst lead to a livelock crash.
6454 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
6457 p = list_first_entry(tasks, struct task_struct, se.group_node);
6460 /* We've more or less seen every task there is, call it quits */
6461 if (env->loop > env->loop_max)
6464 /* take a breather every nr_migrate tasks */
6465 if (env->loop > env->loop_break) {
6466 env->loop_break += sched_nr_migrate_break;
6467 env->flags |= LBF_NEED_BREAK;
6471 if (!can_migrate_task(p, env))
6474 load = task_h_load(p);
6476 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6479 if ((load / 2) > env->imbalance)
6482 detach_task(p, env);
6483 list_add(&p->se.group_node, &env->tasks);
6486 env->imbalance -= load;
6488 #ifdef CONFIG_PREEMPT
6490 * NEWIDLE balancing is a source of latency, so preemptible
6491 * kernels will stop after the first task is detached to minimize
6492 * the critical section.
6494 if (env->idle == CPU_NEWLY_IDLE)
6499 * We only want to steal up to the prescribed amount of
6502 if (env->imbalance <= 0)
6507 list_move_tail(&p->se.group_node, tasks);
6511 * Right now, this is one of only two places we collect this stat
6512 * so we can safely collect detach_one_task() stats here rather
6513 * than inside detach_one_task().
6515 schedstat_add(env->sd, lb_gained[env->idle], detached);
6521 * attach_task() -- attach the task detached by detach_task() to its new rq.
6523 static void attach_task(struct rq *rq, struct task_struct *p)
6525 lockdep_assert_held(&rq->lock);
6527 BUG_ON(task_rq(p) != rq);
6528 p->on_rq = TASK_ON_RQ_QUEUED;
6529 activate_task(rq, p, 0);
6530 check_preempt_curr(rq, p, 0);
6534 * attach_one_task() -- attaches the task returned from detach_one_task() to
6537 static void attach_one_task(struct rq *rq, struct task_struct *p)
6539 raw_spin_lock(&rq->lock);
6542 * We want to potentially raise target_cpu's OPP.
6544 update_capacity_of(cpu_of(rq));
6545 raw_spin_unlock(&rq->lock);
6549 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6552 static void attach_tasks(struct lb_env *env)
6554 struct list_head *tasks = &env->tasks;
6555 struct task_struct *p;
6557 raw_spin_lock(&env->dst_rq->lock);
6559 while (!list_empty(tasks)) {
6560 p = list_first_entry(tasks, struct task_struct, se.group_node);
6561 list_del_init(&p->se.group_node);
6563 attach_task(env->dst_rq, p);
6567 * We want to potentially raise env.dst_cpu's OPP.
6569 update_capacity_of(env->dst_cpu);
6571 raw_spin_unlock(&env->dst_rq->lock);
6574 #ifdef CONFIG_FAIR_GROUP_SCHED
6575 static void update_blocked_averages(int cpu)
6577 struct rq *rq = cpu_rq(cpu);
6578 struct cfs_rq *cfs_rq;
6579 unsigned long flags;
6581 raw_spin_lock_irqsave(&rq->lock, flags);
6582 update_rq_clock(rq);
6585 * Iterates the task_group tree in a bottom up fashion, see
6586 * list_add_leaf_cfs_rq() for details.
6588 for_each_leaf_cfs_rq(rq, cfs_rq) {
6589 /* throttled entities do not contribute to load */
6590 if (throttled_hierarchy(cfs_rq))
6593 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
6594 update_tg_load_avg(cfs_rq, 0);
6596 raw_spin_unlock_irqrestore(&rq->lock, flags);
6600 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6601 * This needs to be done in a top-down fashion because the load of a child
6602 * group is a fraction of its parents load.
6604 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6606 struct rq *rq = rq_of(cfs_rq);
6607 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6608 unsigned long now = jiffies;
6611 if (cfs_rq->last_h_load_update == now)
6614 cfs_rq->h_load_next = NULL;
6615 for_each_sched_entity(se) {
6616 cfs_rq = cfs_rq_of(se);
6617 cfs_rq->h_load_next = se;
6618 if (cfs_rq->last_h_load_update == now)
6623 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6624 cfs_rq->last_h_load_update = now;
6627 while ((se = cfs_rq->h_load_next) != NULL) {
6628 load = cfs_rq->h_load;
6629 load = div64_ul(load * se->avg.load_avg,
6630 cfs_rq_load_avg(cfs_rq) + 1);
6631 cfs_rq = group_cfs_rq(se);
6632 cfs_rq->h_load = load;
6633 cfs_rq->last_h_load_update = now;
6637 static unsigned long task_h_load(struct task_struct *p)
6639 struct cfs_rq *cfs_rq = task_cfs_rq(p);
6641 update_cfs_rq_h_load(cfs_rq);
6642 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6643 cfs_rq_load_avg(cfs_rq) + 1);
6646 static inline void update_blocked_averages(int cpu)
6648 struct rq *rq = cpu_rq(cpu);
6649 struct cfs_rq *cfs_rq = &rq->cfs;
6650 unsigned long flags;
6652 raw_spin_lock_irqsave(&rq->lock, flags);
6653 update_rq_clock(rq);
6654 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
6655 raw_spin_unlock_irqrestore(&rq->lock, flags);
6658 static unsigned long task_h_load(struct task_struct *p)
6660 return p->se.avg.load_avg;
6664 /********** Helpers for find_busiest_group ************************/
6667 * sg_lb_stats - stats of a sched_group required for load_balancing
6669 struct sg_lb_stats {
6670 unsigned long avg_load; /*Avg load across the CPUs of the group */
6671 unsigned long group_load; /* Total load over the CPUs of the group */
6672 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
6673 unsigned long load_per_task;
6674 unsigned long group_capacity;
6675 unsigned long group_util; /* Total utilization of the group */
6676 unsigned int sum_nr_running; /* Nr tasks running in the group */
6677 unsigned int idle_cpus;
6678 unsigned int group_weight;
6679 enum group_type group_type;
6680 int group_no_capacity;
6681 int group_misfit_task; /* A cpu has a task too big for its capacity */
6682 #ifdef CONFIG_NUMA_BALANCING
6683 unsigned int nr_numa_running;
6684 unsigned int nr_preferred_running;
6689 * sd_lb_stats - Structure to store the statistics of a sched_domain
6690 * during load balancing.
6692 struct sd_lb_stats {
6693 struct sched_group *busiest; /* Busiest group in this sd */
6694 struct sched_group *local; /* Local group in this sd */
6695 unsigned long total_load; /* Total load of all groups in sd */
6696 unsigned long total_capacity; /* Total capacity of all groups in sd */
6697 unsigned long avg_load; /* Average load across all groups in sd */
6699 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6700 struct sg_lb_stats local_stat; /* Statistics of the local group */
6703 static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
6706 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6707 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6708 * We must however clear busiest_stat::avg_load because
6709 * update_sd_pick_busiest() reads this before assignment.
6711 *sds = (struct sd_lb_stats){
6715 .total_capacity = 0UL,
6718 .sum_nr_running = 0,
6719 .group_type = group_other,
6725 * get_sd_load_idx - Obtain the load index for a given sched domain.
6726 * @sd: The sched_domain whose load_idx is to be obtained.
6727 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6729 * Return: The load index.
6731 static inline int get_sd_load_idx(struct sched_domain *sd,
6732 enum cpu_idle_type idle)
6738 load_idx = sd->busy_idx;
6741 case CPU_NEWLY_IDLE:
6742 load_idx = sd->newidle_idx;
6745 load_idx = sd->idle_idx;
6752 static unsigned long scale_rt_capacity(int cpu)
6754 struct rq *rq = cpu_rq(cpu);
6755 u64 total, used, age_stamp, avg;
6759 * Since we're reading these variables without serialization make sure
6760 * we read them once before doing sanity checks on them.
6762 age_stamp = READ_ONCE(rq->age_stamp);
6763 avg = READ_ONCE(rq->rt_avg);
6764 delta = __rq_clock_broken(rq) - age_stamp;
6766 if (unlikely(delta < 0))
6769 total = sched_avg_period() + delta;
6771 used = div_u64(avg, total);
6774 * deadline bandwidth is defined at system level so we must
6775 * weight this bandwidth with the max capacity of the system.
6776 * As a reminder, avg_bw is 20bits width and
6777 * scale_cpu_capacity is 10 bits width
6779 used += div_u64(rq->dl.avg_bw, arch_scale_cpu_capacity(NULL, cpu));
6781 if (likely(used < SCHED_CAPACITY_SCALE))
6782 return SCHED_CAPACITY_SCALE - used;
6787 void init_max_cpu_capacity(struct max_cpu_capacity *mcc)
6789 raw_spin_lock_init(&mcc->lock);
6794 static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6796 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6797 struct sched_group *sdg = sd->groups;
6798 struct max_cpu_capacity *mcc;
6799 unsigned long max_capacity;
6801 unsigned long flags;
6803 cpu_rq(cpu)->cpu_capacity_orig = capacity;
6805 mcc = &cpu_rq(cpu)->rd->max_cpu_capacity;
6807 raw_spin_lock_irqsave(&mcc->lock, flags);
6808 max_capacity = mcc->val;
6809 max_cap_cpu = mcc->cpu;
6811 if ((max_capacity > capacity && max_cap_cpu == cpu) ||
6812 (max_capacity < capacity)) {
6813 mcc->val = capacity;
6815 #ifdef CONFIG_SCHED_DEBUG
6816 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6817 pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity);
6821 raw_spin_unlock_irqrestore(&mcc->lock, flags);
6823 skip_unlock: __attribute__ ((unused));
6824 capacity *= scale_rt_capacity(cpu);
6825 capacity >>= SCHED_CAPACITY_SHIFT;
6830 cpu_rq(cpu)->cpu_capacity = capacity;
6831 sdg->sgc->capacity = capacity;
6832 sdg->sgc->max_capacity = capacity;
6835 void update_group_capacity(struct sched_domain *sd, int cpu)
6837 struct sched_domain *child = sd->child;
6838 struct sched_group *group, *sdg = sd->groups;
6839 unsigned long capacity, max_capacity;
6840 unsigned long interval;
6842 interval = msecs_to_jiffies(sd->balance_interval);
6843 interval = clamp(interval, 1UL, max_load_balance_interval);
6844 sdg->sgc->next_update = jiffies + interval;
6847 update_cpu_capacity(sd, cpu);
6854 if (child->flags & SD_OVERLAP) {
6856 * SD_OVERLAP domains cannot assume that child groups
6857 * span the current group.
6860 for_each_cpu(cpu, sched_group_cpus(sdg)) {
6861 struct sched_group_capacity *sgc;
6862 struct rq *rq = cpu_rq(cpu);
6865 * build_sched_domains() -> init_sched_groups_capacity()
6866 * gets here before we've attached the domains to the
6869 * Use capacity_of(), which is set irrespective of domains
6870 * in update_cpu_capacity().
6872 * This avoids capacity from being 0 and
6873 * causing divide-by-zero issues on boot.
6875 if (unlikely(!rq->sd)) {
6876 capacity += capacity_of(cpu);
6878 sgc = rq->sd->groups->sgc;
6879 capacity += sgc->capacity;
6882 max_capacity = max(capacity, max_capacity);
6886 * !SD_OVERLAP domains can assume that child groups
6887 * span the current group.
6890 group = child->groups;
6892 struct sched_group_capacity *sgc = group->sgc;
6894 capacity += sgc->capacity;
6895 max_capacity = max(sgc->max_capacity, max_capacity);
6896 group = group->next;
6897 } while (group != child->groups);
6900 sdg->sgc->capacity = capacity;
6901 sdg->sgc->max_capacity = max_capacity;
6905 * Check whether the capacity of the rq has been noticeably reduced by side
6906 * activity. The imbalance_pct is used for the threshold.
6907 * Return true is the capacity is reduced
6910 check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6912 return ((rq->cpu_capacity * sd->imbalance_pct) <
6913 (rq->cpu_capacity_orig * 100));
6917 * Group imbalance indicates (and tries to solve) the problem where balancing
6918 * groups is inadequate due to tsk_cpus_allowed() constraints.
6920 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6921 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6924 * { 0 1 2 3 } { 4 5 6 7 }
6927 * If we were to balance group-wise we'd place two tasks in the first group and
6928 * two tasks in the second group. Clearly this is undesired as it will overload
6929 * cpu 3 and leave one of the cpus in the second group unused.
6931 * The current solution to this issue is detecting the skew in the first group
6932 * by noticing the lower domain failed to reach balance and had difficulty
6933 * moving tasks due to affinity constraints.
6935 * When this is so detected; this group becomes a candidate for busiest; see
6936 * update_sd_pick_busiest(). And calculate_imbalance() and
6937 * find_busiest_group() avoid some of the usual balance conditions to allow it
6938 * to create an effective group imbalance.
6940 * This is a somewhat tricky proposition since the next run might not find the
6941 * group imbalance and decide the groups need to be balanced again. A most
6942 * subtle and fragile situation.
6945 static inline int sg_imbalanced(struct sched_group *group)
6947 return group->sgc->imbalance;
6951 * group_has_capacity returns true if the group has spare capacity that could
6952 * be used by some tasks.
6953 * We consider that a group has spare capacity if the * number of task is
6954 * smaller than the number of CPUs or if the utilization is lower than the
6955 * available capacity for CFS tasks.
6956 * For the latter, we use a threshold to stabilize the state, to take into
6957 * account the variance of the tasks' load and to return true if the available
6958 * capacity in meaningful for the load balancer.
6959 * As an example, an available capacity of 1% can appear but it doesn't make
6960 * any benefit for the load balance.
6963 group_has_capacity(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))
6976 * group_is_overloaded returns true if the group has more tasks than it can
6978 * group_is_overloaded is not equals to !group_has_capacity because a group
6979 * with the exact right number of tasks, has no more spare capacity but is not
6980 * overloaded so both group_has_capacity and group_is_overloaded return
6984 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
6986 if (sgs->sum_nr_running <= sgs->group_weight)
6989 if ((sgs->group_capacity * 100) <
6990 (sgs->group_util * env->sd->imbalance_pct))
6998 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
6999 * per-cpu capacity than sched_group ref.
7002 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
7004 return sg->sgc->max_capacity + capacity_margin - SCHED_LOAD_SCALE <
7005 ref->sgc->max_capacity;
7009 group_type group_classify(struct sched_group *group,
7010 struct sg_lb_stats *sgs)
7012 if (sgs->group_no_capacity)
7013 return group_overloaded;
7015 if (sg_imbalanced(group))
7016 return group_imbalanced;
7018 if (sgs->group_misfit_task)
7019 return group_misfit_task;
7025 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7026 * @env: The load balancing environment.
7027 * @group: sched_group whose statistics are to be updated.
7028 * @load_idx: Load index of sched_domain of this_cpu for load calc.
7029 * @local_group: Does group contain this_cpu.
7030 * @sgs: variable to hold the statistics for this group.
7031 * @overload: Indicate more than one runnable task for any CPU.
7032 * @overutilized: Indicate overutilization for any CPU.
7034 static inline void update_sg_lb_stats(struct lb_env *env,
7035 struct sched_group *group, int load_idx,
7036 int local_group, struct sg_lb_stats *sgs,
7037 bool *overload, bool *overutilized)
7042 memset(sgs, 0, sizeof(*sgs));
7044 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7045 struct rq *rq = cpu_rq(i);
7047 /* Bias balancing toward cpus of our domain */
7049 load = target_load(i, load_idx);
7051 load = source_load(i, load_idx);
7053 sgs->group_load += load;
7054 sgs->group_util += cpu_util(i);
7055 sgs->sum_nr_running += rq->cfs.h_nr_running;
7057 if (rq->nr_running > 1)
7060 #ifdef CONFIG_NUMA_BALANCING
7061 sgs->nr_numa_running += rq->nr_numa_running;
7062 sgs->nr_preferred_running += rq->nr_preferred_running;
7064 sgs->sum_weighted_load += weighted_cpuload(i);
7068 if (cpu_overutilized(i)) {
7069 *overutilized = true;
7070 if (!sgs->group_misfit_task && rq->misfit_task)
7071 sgs->group_misfit_task = capacity_of(i);
7075 /* Adjust by relative CPU capacity of the group */
7076 sgs->group_capacity = group->sgc->capacity;
7077 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7079 if (sgs->sum_nr_running)
7080 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7082 sgs->group_weight = group->group_weight;
7084 sgs->group_no_capacity = group_is_overloaded(env, sgs);
7085 sgs->group_type = group_classify(group, sgs);
7089 * update_sd_pick_busiest - return 1 on busiest group
7090 * @env: The load balancing environment.
7091 * @sds: sched_domain statistics
7092 * @sg: sched_group candidate to be checked for being the busiest
7093 * @sgs: sched_group statistics
7095 * Determine if @sg is a busier group than the previously selected
7098 * Return: %true if @sg is a busier group than the previously selected
7099 * busiest group. %false otherwise.
7101 static bool update_sd_pick_busiest(struct lb_env *env,
7102 struct sd_lb_stats *sds,
7103 struct sched_group *sg,
7104 struct sg_lb_stats *sgs)
7106 struct sg_lb_stats *busiest = &sds->busiest_stat;
7108 if (sgs->group_type > busiest->group_type)
7111 if (sgs->group_type < busiest->group_type)
7115 * Candidate sg doesn't face any serious load-balance problems
7116 * so don't pick it if the local sg is already filled up.
7118 if (sgs->group_type == group_other &&
7119 !group_has_capacity(env, &sds->local_stat))
7122 if (sgs->avg_load <= busiest->avg_load)
7126 * Candiate sg has no more than one task per cpu and has higher
7127 * per-cpu capacity. No reason to pull tasks to less capable cpus.
7129 if (sgs->sum_nr_running <= sgs->group_weight &&
7130 group_smaller_cpu_capacity(sds->local, sg))
7133 /* This is the busiest node in its class. */
7134 if (!(env->sd->flags & SD_ASYM_PACKING))
7138 * ASYM_PACKING needs to move all the work to the lowest
7139 * numbered CPUs in the group, therefore mark all groups
7140 * higher than ourself as busy.
7142 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
7146 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
7153 #ifdef CONFIG_NUMA_BALANCING
7154 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7156 if (sgs->sum_nr_running > sgs->nr_numa_running)
7158 if (sgs->sum_nr_running > sgs->nr_preferred_running)
7163 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7165 if (rq->nr_running > rq->nr_numa_running)
7167 if (rq->nr_running > rq->nr_preferred_running)
7172 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
7177 static inline enum fbq_type fbq_classify_rq(struct rq *rq)
7181 #endif /* CONFIG_NUMA_BALANCING */
7184 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7185 * @env: The load balancing environment.
7186 * @sds: variable to hold the statistics for this sched_domain.
7188 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7190 struct sched_domain *child = env->sd->child;
7191 struct sched_group *sg = env->sd->groups;
7192 struct sg_lb_stats tmp_sgs;
7193 int load_idx, prefer_sibling = 0;
7194 bool overload = false, overutilized = false;
7196 if (child && child->flags & SD_PREFER_SIBLING)
7199 load_idx = get_sd_load_idx(env->sd, env->idle);
7202 struct sg_lb_stats *sgs = &tmp_sgs;
7205 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
7208 sgs = &sds->local_stat;
7210 if (env->idle != CPU_NEWLY_IDLE ||
7211 time_after_eq(jiffies, sg->sgc->next_update))
7212 update_group_capacity(env->sd, env->dst_cpu);
7215 update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
7216 &overload, &overutilized);
7222 * In case the child domain prefers tasks go to siblings
7223 * first, lower the sg capacity so that we'll try
7224 * and move all the excess tasks away. We lower the capacity
7225 * of a group only if the local group has the capacity to fit
7226 * these excess tasks. The extra check prevents the case where
7227 * you always pull from the heaviest group when it is already
7228 * under-utilized (possible with a large weight task outweighs
7229 * the tasks on the system).
7231 if (prefer_sibling && sds->local &&
7232 group_has_capacity(env, &sds->local_stat) &&
7233 (sgs->sum_nr_running > 1)) {
7234 sgs->group_no_capacity = 1;
7235 sgs->group_type = group_classify(sg, sgs);
7239 * Ignore task groups with misfit tasks if local group has no
7240 * capacity or if per-cpu capacity isn't higher.
7242 if (sgs->group_type == group_misfit_task &&
7243 (!group_has_capacity(env, &sds->local_stat) ||
7244 !group_smaller_cpu_capacity(sg, sds->local)))
7245 sgs->group_type = group_other;
7247 if (update_sd_pick_busiest(env, sds, sg, sgs)) {
7249 sds->busiest_stat = *sgs;
7253 /* Now, start updating sd_lb_stats */
7254 sds->total_load += sgs->group_load;
7255 sds->total_capacity += sgs->group_capacity;
7258 } while (sg != env->sd->groups);
7260 if (env->sd->flags & SD_NUMA)
7261 env->fbq_type = fbq_classify_group(&sds->busiest_stat);
7263 env->src_grp_nr_running = sds->busiest_stat.sum_nr_running;
7265 if (!env->sd->parent) {
7266 /* update overload indicator if we are at root domain */
7267 if (env->dst_rq->rd->overload != overload)
7268 env->dst_rq->rd->overload = overload;
7270 /* Update over-utilization (tipping point, U >= 0) indicator */
7271 if (env->dst_rq->rd->overutilized != overutilized)
7272 env->dst_rq->rd->overutilized = overutilized;
7274 if (!env->dst_rq->rd->overutilized && overutilized)
7275 env->dst_rq->rd->overutilized = true;
7280 * check_asym_packing - Check to see if the group is packed into the
7283 * This is primarily intended to used at the sibling level. Some
7284 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7285 * case of POWER7, it can move to lower SMT modes only when higher
7286 * threads are idle. When in lower SMT modes, the threads will
7287 * perform better since they share less core resources. Hence when we
7288 * have idle threads, we want them to be the higher ones.
7290 * This packing function is run on idle threads. It checks to see if
7291 * the busiest CPU in this domain (core in the P7 case) has a higher
7292 * CPU number than the packing function is being run on. Here we are
7293 * assuming lower CPU number will be equivalent to lower a SMT thread
7296 * Return: 1 when packing is required and a task should be moved to
7297 * this CPU. The amount of the imbalance is returned in *imbalance.
7299 * @env: The load balancing environment.
7300 * @sds: Statistics of the sched_domain which is to be packed
7302 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7306 if (!(env->sd->flags & SD_ASYM_PACKING))
7312 busiest_cpu = group_first_cpu(sds->busiest);
7313 if (env->dst_cpu > busiest_cpu)
7316 env->imbalance = DIV_ROUND_CLOSEST(
7317 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7318 SCHED_CAPACITY_SCALE);
7324 * fix_small_imbalance - Calculate the minor imbalance that exists
7325 * amongst the groups of a sched_domain, during
7327 * @env: The load balancing environment.
7328 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7331 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7333 unsigned long tmp, capa_now = 0, capa_move = 0;
7334 unsigned int imbn = 2;
7335 unsigned long scaled_busy_load_per_task;
7336 struct sg_lb_stats *local, *busiest;
7338 local = &sds->local_stat;
7339 busiest = &sds->busiest_stat;
7341 if (!local->sum_nr_running)
7342 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
7343 else if (busiest->load_per_task > local->load_per_task)
7346 scaled_busy_load_per_task =
7347 (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7348 busiest->group_capacity;
7350 if (busiest->avg_load + scaled_busy_load_per_task >=
7351 local->avg_load + (scaled_busy_load_per_task * imbn)) {
7352 env->imbalance = busiest->load_per_task;
7357 * OK, we don't have enough imbalance to justify moving tasks,
7358 * however we may be able to increase total CPU capacity used by
7362 capa_now += busiest->group_capacity *
7363 min(busiest->load_per_task, busiest->avg_load);
7364 capa_now += local->group_capacity *
7365 min(local->load_per_task, local->avg_load);
7366 capa_now /= SCHED_CAPACITY_SCALE;
7368 /* Amount of load we'd subtract */
7369 if (busiest->avg_load > scaled_busy_load_per_task) {
7370 capa_move += busiest->group_capacity *
7371 min(busiest->load_per_task,
7372 busiest->avg_load - scaled_busy_load_per_task);
7375 /* Amount of load we'd add */
7376 if (busiest->avg_load * busiest->group_capacity <
7377 busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7378 tmp = (busiest->avg_load * busiest->group_capacity) /
7379 local->group_capacity;
7381 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7382 local->group_capacity;
7384 capa_move += local->group_capacity *
7385 min(local->load_per_task, local->avg_load + tmp);
7386 capa_move /= SCHED_CAPACITY_SCALE;
7388 /* Move if we gain throughput */
7389 if (capa_move > capa_now)
7390 env->imbalance = busiest->load_per_task;
7394 * calculate_imbalance - Calculate the amount of imbalance present within the
7395 * groups of a given sched_domain during load balance.
7396 * @env: load balance environment
7397 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7399 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7401 unsigned long max_pull, load_above_capacity = ~0UL;
7402 struct sg_lb_stats *local, *busiest;
7404 local = &sds->local_stat;
7405 busiest = &sds->busiest_stat;
7407 if (busiest->group_type == group_imbalanced) {
7409 * In the group_imb case we cannot rely on group-wide averages
7410 * to ensure cpu-load equilibrium, look at wider averages. XXX
7412 busiest->load_per_task =
7413 min(busiest->load_per_task, sds->avg_load);
7417 * In the presence of smp nice balancing, certain scenarios can have
7418 * max load less than avg load(as we skip the groups at or below
7419 * its cpu_capacity, while calculating max_load..)
7421 if (busiest->avg_load <= sds->avg_load ||
7422 local->avg_load >= sds->avg_load) {
7423 /* Misfitting tasks should be migrated in any case */
7424 if (busiest->group_type == group_misfit_task) {
7425 env->imbalance = busiest->group_misfit_task;
7430 * Busiest group is overloaded, local is not, use the spare
7431 * cycles to maximize throughput
7433 if (busiest->group_type == group_overloaded &&
7434 local->group_type <= group_misfit_task) {
7435 env->imbalance = busiest->load_per_task;
7440 return fix_small_imbalance(env, sds);
7444 * If there aren't any idle cpus, avoid creating some.
7446 if (busiest->group_type == group_overloaded &&
7447 local->group_type == group_overloaded) {
7448 load_above_capacity = busiest->sum_nr_running *
7450 if (load_above_capacity > busiest->group_capacity)
7451 load_above_capacity -= busiest->group_capacity;
7453 load_above_capacity = ~0UL;
7457 * We're trying to get all the cpus to the average_load, so we don't
7458 * want to push ourselves above the average load, nor do we wish to
7459 * reduce the max loaded cpu below the average load. At the same time,
7460 * we also don't want to reduce the group load below the group capacity
7461 * (so that we can implement power-savings policies etc). Thus we look
7462 * for the minimum possible imbalance.
7464 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7466 /* How much load to actually move to equalise the imbalance */
7467 env->imbalance = min(
7468 max_pull * busiest->group_capacity,
7469 (sds->avg_load - local->avg_load) * local->group_capacity
7470 ) / SCHED_CAPACITY_SCALE;
7472 /* Boost imbalance to allow misfit task to be balanced. */
7473 if (busiest->group_type == group_misfit_task)
7474 env->imbalance = max_t(long, env->imbalance,
7475 busiest->group_misfit_task);
7478 * if *imbalance is less than the average load per runnable task
7479 * there is no guarantee that any tasks will be moved so we'll have
7480 * a think about bumping its value to force at least one task to be
7483 if (env->imbalance < busiest->load_per_task)
7484 return fix_small_imbalance(env, sds);
7487 /******* find_busiest_group() helpers end here *********************/
7490 * find_busiest_group - Returns the busiest group within the sched_domain
7491 * if there is an imbalance. If there isn't an imbalance, and
7492 * the user has opted for power-savings, it returns a group whose
7493 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7494 * such a group exists.
7496 * Also calculates the amount of weighted load which should be moved
7497 * to restore balance.
7499 * @env: The load balancing environment.
7501 * Return: - The busiest group if imbalance exists.
7502 * - If no imbalance and user has opted for power-savings balance,
7503 * return the least loaded group whose CPUs can be
7504 * put to idle by rebalancing its tasks onto our group.
7506 static struct sched_group *find_busiest_group(struct lb_env *env)
7508 struct sg_lb_stats *local, *busiest;
7509 struct sd_lb_stats sds;
7511 init_sd_lb_stats(&sds);
7514 * Compute the various statistics relavent for load balancing at
7517 update_sd_lb_stats(env, &sds);
7519 if (energy_aware() && !env->dst_rq->rd->overutilized)
7522 local = &sds.local_stat;
7523 busiest = &sds.busiest_stat;
7525 /* ASYM feature bypasses nice load balance check */
7526 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
7527 check_asym_packing(env, &sds))
7530 /* There is no busy sibling group to pull tasks from */
7531 if (!sds.busiest || busiest->sum_nr_running == 0)
7534 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
7535 / sds.total_capacity;
7538 * If the busiest group is imbalanced the below checks don't
7539 * work because they assume all things are equal, which typically
7540 * isn't true due to cpus_allowed constraints and the like.
7542 if (busiest->group_type == group_imbalanced)
7545 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7546 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
7547 busiest->group_no_capacity)
7550 /* Misfitting tasks should be dealt with regardless of the avg load */
7551 if (busiest->group_type == group_misfit_task) {
7556 * If the local group is busier than the selected busiest group
7557 * don't try and pull any tasks.
7559 if (local->avg_load >= busiest->avg_load)
7563 * Don't pull any tasks if this group is already above the domain
7566 if (local->avg_load >= sds.avg_load)
7569 if (env->idle == CPU_IDLE) {
7571 * This cpu is idle. If the busiest group is not overloaded
7572 * and there is no imbalance between this and busiest group
7573 * wrt idle cpus, it is balanced. The imbalance becomes
7574 * significant if the diff is greater than 1 otherwise we
7575 * might end up to just move the imbalance on another group
7577 if ((busiest->group_type != group_overloaded) &&
7578 (local->idle_cpus <= (busiest->idle_cpus + 1)) &&
7579 !group_smaller_cpu_capacity(sds.busiest, sds.local))
7583 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7584 * imbalance_pct to be conservative.
7586 if (100 * busiest->avg_load <=
7587 env->sd->imbalance_pct * local->avg_load)
7592 env->busiest_group_type = busiest->group_type;
7593 /* Looks like there is an imbalance. Compute it */
7594 calculate_imbalance(env, &sds);
7603 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7605 static struct rq *find_busiest_queue(struct lb_env *env,
7606 struct sched_group *group)
7608 struct rq *busiest = NULL, *rq;
7609 unsigned long busiest_load = 0, busiest_capacity = 1;
7612 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7613 unsigned long capacity, wl;
7617 rt = fbq_classify_rq(rq);
7620 * We classify groups/runqueues into three groups:
7621 * - regular: there are !numa tasks
7622 * - remote: there are numa tasks that run on the 'wrong' node
7623 * - all: there is no distinction
7625 * In order to avoid migrating ideally placed numa tasks,
7626 * ignore those when there's better options.
7628 * If we ignore the actual busiest queue to migrate another
7629 * task, the next balance pass can still reduce the busiest
7630 * queue by moving tasks around inside the node.
7632 * If we cannot move enough load due to this classification
7633 * the next pass will adjust the group classification and
7634 * allow migration of more tasks.
7636 * Both cases only affect the total convergence complexity.
7638 if (rt > env->fbq_type)
7641 capacity = capacity_of(i);
7643 wl = weighted_cpuload(i);
7646 * When comparing with imbalance, use weighted_cpuload()
7647 * which is not scaled with the cpu capacity.
7650 if (rq->nr_running == 1 && wl > env->imbalance &&
7651 !check_cpu_capacity(rq, env->sd) &&
7652 env->busiest_group_type != group_misfit_task)
7656 * For the load comparisons with the other cpu's, consider
7657 * the weighted_cpuload() scaled with the cpu capacity, so
7658 * that the load can be moved away from the cpu that is
7659 * potentially running at a lower capacity.
7661 * Thus we're looking for max(wl_i / capacity_i), crosswise
7662 * multiplication to rid ourselves of the division works out
7663 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7664 * our previous maximum.
7666 if (wl * busiest_capacity > busiest_load * capacity) {
7668 busiest_capacity = capacity;
7677 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7678 * so long as it is large enough.
7680 #define MAX_PINNED_INTERVAL 512
7682 /* Working cpumask for load_balance and load_balance_newidle. */
7683 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7685 static int need_active_balance(struct lb_env *env)
7687 struct sched_domain *sd = env->sd;
7689 if (env->idle == CPU_NEWLY_IDLE) {
7692 * ASYM_PACKING needs to force migrate tasks from busy but
7693 * higher numbered CPUs in order to pack all tasks in the
7694 * lowest numbered CPUs.
7696 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7701 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7702 * It's worth migrating the task if the src_cpu's capacity is reduced
7703 * because of other sched_class or IRQs if more capacity stays
7704 * available on dst_cpu.
7706 if ((env->idle != CPU_NOT_IDLE) &&
7707 (env->src_rq->cfs.h_nr_running == 1)) {
7708 if ((check_cpu_capacity(env->src_rq, sd)) &&
7709 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
7713 if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
7714 env->src_rq->cfs.h_nr_running == 1 &&
7715 cpu_overutilized(env->src_cpu) &&
7716 !cpu_overutilized(env->dst_cpu)) {
7720 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
7723 static int active_load_balance_cpu_stop(void *data);
7725 static int should_we_balance(struct lb_env *env)
7727 struct sched_group *sg = env->sd->groups;
7728 struct cpumask *sg_cpus, *sg_mask;
7729 int cpu, balance_cpu = -1;
7732 * In the newly idle case, we will allow all the cpu's
7733 * to do the newly idle load balance.
7735 if (env->idle == CPU_NEWLY_IDLE)
7738 sg_cpus = sched_group_cpus(sg);
7739 sg_mask = sched_group_mask(sg);
7740 /* Try to find first idle cpu */
7741 for_each_cpu_and(cpu, sg_cpus, env->cpus) {
7742 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
7749 if (balance_cpu == -1)
7750 balance_cpu = group_balance_cpu(sg);
7753 * First idle cpu or the first cpu(busiest) in this sched group
7754 * is eligible for doing load balancing at this and above domains.
7756 return balance_cpu == env->dst_cpu;
7760 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7761 * tasks if there is an imbalance.
7763 static int load_balance(int this_cpu, struct rq *this_rq,
7764 struct sched_domain *sd, enum cpu_idle_type idle,
7765 int *continue_balancing)
7767 int ld_moved, cur_ld_moved, active_balance = 0;
7768 struct sched_domain *sd_parent = sd->parent;
7769 struct sched_group *group;
7771 unsigned long flags;
7772 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7774 struct lb_env env = {
7776 .dst_cpu = this_cpu,
7778 .dst_grpmask = sched_group_cpus(sd->groups),
7780 .loop_break = sched_nr_migrate_break,
7783 .tasks = LIST_HEAD_INIT(env.tasks),
7787 * For NEWLY_IDLE load_balancing, we don't need to consider
7788 * other cpus in our group
7790 if (idle == CPU_NEWLY_IDLE)
7791 env.dst_grpmask = NULL;
7793 cpumask_copy(cpus, cpu_active_mask);
7795 schedstat_inc(sd, lb_count[idle]);
7798 if (!should_we_balance(&env)) {
7799 *continue_balancing = 0;
7803 group = find_busiest_group(&env);
7805 schedstat_inc(sd, lb_nobusyg[idle]);
7809 busiest = find_busiest_queue(&env, group);
7811 schedstat_inc(sd, lb_nobusyq[idle]);
7815 BUG_ON(busiest == env.dst_rq);
7817 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7819 env.src_cpu = busiest->cpu;
7820 env.src_rq = busiest;
7823 if (busiest->nr_running > 1) {
7825 * Attempt to move tasks. If find_busiest_group has found
7826 * an imbalance but busiest->nr_running <= 1, the group is
7827 * still unbalanced. ld_moved simply stays zero, so it is
7828 * correctly treated as an imbalance.
7830 env.flags |= LBF_ALL_PINNED;
7831 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
7834 raw_spin_lock_irqsave(&busiest->lock, flags);
7837 * cur_ld_moved - load moved in current iteration
7838 * ld_moved - cumulative load moved across iterations
7840 cur_ld_moved = detach_tasks(&env);
7842 * We want to potentially lower env.src_cpu's OPP.
7845 update_capacity_of(env.src_cpu);
7848 * We've detached some tasks from busiest_rq. Every
7849 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7850 * unlock busiest->lock, and we are able to be sure
7851 * that nobody can manipulate the tasks in parallel.
7852 * See task_rq_lock() family for the details.
7855 raw_spin_unlock(&busiest->lock);
7859 ld_moved += cur_ld_moved;
7862 local_irq_restore(flags);
7864 if (env.flags & LBF_NEED_BREAK) {
7865 env.flags &= ~LBF_NEED_BREAK;
7870 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7871 * us and move them to an alternate dst_cpu in our sched_group
7872 * where they can run. The upper limit on how many times we
7873 * iterate on same src_cpu is dependent on number of cpus in our
7876 * This changes load balance semantics a bit on who can move
7877 * load to a given_cpu. In addition to the given_cpu itself
7878 * (or a ilb_cpu acting on its behalf where given_cpu is
7879 * nohz-idle), we now have balance_cpu in a position to move
7880 * load to given_cpu. In rare situations, this may cause
7881 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7882 * _independently_ and at _same_ time to move some load to
7883 * given_cpu) causing exceess load to be moved to given_cpu.
7884 * This however should not happen so much in practice and
7885 * moreover subsequent load balance cycles should correct the
7886 * excess load moved.
7888 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7890 /* Prevent to re-select dst_cpu via env's cpus */
7891 cpumask_clear_cpu(env.dst_cpu, env.cpus);
7893 env.dst_rq = cpu_rq(env.new_dst_cpu);
7894 env.dst_cpu = env.new_dst_cpu;
7895 env.flags &= ~LBF_DST_PINNED;
7897 env.loop_break = sched_nr_migrate_break;
7900 * Go back to "more_balance" rather than "redo" since we
7901 * need to continue with same src_cpu.
7907 * We failed to reach balance because of affinity.
7910 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7912 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7913 *group_imbalance = 1;
7916 /* All tasks on this runqueue were pinned by CPU affinity */
7917 if (unlikely(env.flags & LBF_ALL_PINNED)) {
7918 cpumask_clear_cpu(cpu_of(busiest), cpus);
7919 if (!cpumask_empty(cpus)) {
7921 env.loop_break = sched_nr_migrate_break;
7924 goto out_all_pinned;
7929 schedstat_inc(sd, lb_failed[idle]);
7931 * Increment the failure counter only on periodic balance.
7932 * We do not want newidle balance, which can be very
7933 * frequent, pollute the failure counter causing
7934 * excessive cache_hot migrations and active balances.
7936 if (idle != CPU_NEWLY_IDLE)
7937 if (env.src_grp_nr_running > 1)
7938 sd->nr_balance_failed++;
7940 if (need_active_balance(&env)) {
7941 raw_spin_lock_irqsave(&busiest->lock, flags);
7943 /* don't kick the active_load_balance_cpu_stop,
7944 * if the curr task on busiest cpu can't be
7947 if (!cpumask_test_cpu(this_cpu,
7948 tsk_cpus_allowed(busiest->curr))) {
7949 raw_spin_unlock_irqrestore(&busiest->lock,
7951 env.flags |= LBF_ALL_PINNED;
7952 goto out_one_pinned;
7956 * ->active_balance synchronizes accesses to
7957 * ->active_balance_work. Once set, it's cleared
7958 * only after active load balance is finished.
7960 if (!busiest->active_balance) {
7961 busiest->active_balance = 1;
7962 busiest->push_cpu = this_cpu;
7965 raw_spin_unlock_irqrestore(&busiest->lock, flags);
7967 if (active_balance) {
7968 stop_one_cpu_nowait(cpu_of(busiest),
7969 active_load_balance_cpu_stop, busiest,
7970 &busiest->active_balance_work);
7974 * We've kicked active balancing, reset the failure
7977 sd->nr_balance_failed = sd->cache_nice_tries+1;
7980 sd->nr_balance_failed = 0;
7982 if (likely(!active_balance)) {
7983 /* We were unbalanced, so reset the balancing interval */
7984 sd->balance_interval = sd->min_interval;
7987 * If we've begun active balancing, start to back off. This
7988 * case may not be covered by the all_pinned logic if there
7989 * is only 1 task on the busy runqueue (because we don't call
7992 if (sd->balance_interval < sd->max_interval)
7993 sd->balance_interval *= 2;
8000 * We reach balance although we may have faced some affinity
8001 * constraints. Clear the imbalance flag if it was set.
8004 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8006 if (*group_imbalance)
8007 *group_imbalance = 0;
8012 * We reach balance because all tasks are pinned at this level so
8013 * we can't migrate them. Let the imbalance flag set so parent level
8014 * can try to migrate them.
8016 schedstat_inc(sd, lb_balanced[idle]);
8018 sd->nr_balance_failed = 0;
8021 /* tune up the balancing interval */
8022 if (((env.flags & LBF_ALL_PINNED) &&
8023 sd->balance_interval < MAX_PINNED_INTERVAL) ||
8024 (sd->balance_interval < sd->max_interval))
8025 sd->balance_interval *= 2;
8032 static inline unsigned long
8033 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
8035 unsigned long interval = sd->balance_interval;
8038 interval *= sd->busy_factor;
8040 /* scale ms to jiffies */
8041 interval = msecs_to_jiffies(interval);
8042 interval = clamp(interval, 1UL, max_load_balance_interval);
8048 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
8050 unsigned long interval, next;
8052 interval = get_sd_balance_interval(sd, cpu_busy);
8053 next = sd->last_balance + interval;
8055 if (time_after(*next_balance, next))
8056 *next_balance = next;
8060 * idle_balance is called by schedule() if this_cpu is about to become
8061 * idle. Attempts to pull tasks from other CPUs.
8063 static int idle_balance(struct rq *this_rq)
8065 unsigned long next_balance = jiffies + HZ;
8066 int this_cpu = this_rq->cpu;
8067 struct sched_domain *sd;
8068 int pulled_task = 0;
8071 idle_enter_fair(this_rq);
8074 * We must set idle_stamp _before_ calling idle_balance(), such that we
8075 * measure the duration of idle_balance() as idle time.
8077 this_rq->idle_stamp = rq_clock(this_rq);
8079 if (!energy_aware() &&
8080 (this_rq->avg_idle < sysctl_sched_migration_cost ||
8081 !this_rq->rd->overload)) {
8083 sd = rcu_dereference_check_sched_domain(this_rq->sd);
8085 update_next_balance(sd, 0, &next_balance);
8091 raw_spin_unlock(&this_rq->lock);
8093 update_blocked_averages(this_cpu);
8095 for_each_domain(this_cpu, sd) {
8096 int continue_balancing = 1;
8097 u64 t0, domain_cost;
8099 if (!(sd->flags & SD_LOAD_BALANCE))
8102 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8103 update_next_balance(sd, 0, &next_balance);
8107 if (sd->flags & SD_BALANCE_NEWIDLE) {
8108 t0 = sched_clock_cpu(this_cpu);
8110 pulled_task = load_balance(this_cpu, this_rq,
8112 &continue_balancing);
8114 domain_cost = sched_clock_cpu(this_cpu) - t0;
8115 if (domain_cost > sd->max_newidle_lb_cost)
8116 sd->max_newidle_lb_cost = domain_cost;
8118 curr_cost += domain_cost;
8121 update_next_balance(sd, 0, &next_balance);
8124 * Stop searching for tasks to pull if there are
8125 * now runnable tasks on this rq.
8127 if (pulled_task || this_rq->nr_running > 0)
8132 raw_spin_lock(&this_rq->lock);
8134 if (curr_cost > this_rq->max_idle_balance_cost)
8135 this_rq->max_idle_balance_cost = curr_cost;
8138 * While browsing the domains, we released the rq lock, a task could
8139 * have been enqueued in the meantime. Since we're not going idle,
8140 * pretend we pulled a task.
8142 if (this_rq->cfs.h_nr_running && !pulled_task)
8146 /* Move the next balance forward */
8147 if (time_after(this_rq->next_balance, next_balance))
8148 this_rq->next_balance = next_balance;
8150 /* Is there a task of a high priority class? */
8151 if (this_rq->nr_running != this_rq->cfs.h_nr_running)
8155 idle_exit_fair(this_rq);
8156 this_rq->idle_stamp = 0;
8163 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
8164 * running tasks off the busiest CPU onto idle CPUs. It requires at
8165 * least 1 task to be running on each physical CPU where possible, and
8166 * avoids physical / logical imbalances.
8168 static int active_load_balance_cpu_stop(void *data)
8170 struct rq *busiest_rq = data;
8171 int busiest_cpu = cpu_of(busiest_rq);
8172 int target_cpu = busiest_rq->push_cpu;
8173 struct rq *target_rq = cpu_rq(target_cpu);
8174 struct sched_domain *sd;
8175 struct task_struct *p = NULL;
8177 raw_spin_lock_irq(&busiest_rq->lock);
8179 /* make sure the requested cpu hasn't gone down in the meantime */
8180 if (unlikely(busiest_cpu != smp_processor_id() ||
8181 !busiest_rq->active_balance))
8184 /* Is there any task to move? */
8185 if (busiest_rq->nr_running <= 1)
8189 * This condition is "impossible", if it occurs
8190 * we need to fix it. Originally reported by
8191 * Bjorn Helgaas on a 128-cpu setup.
8193 BUG_ON(busiest_rq == target_rq);
8195 /* Search for an sd spanning us and the target CPU. */
8197 for_each_domain(target_cpu, sd) {
8198 if ((sd->flags & SD_LOAD_BALANCE) &&
8199 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
8204 struct lb_env env = {
8206 .dst_cpu = target_cpu,
8207 .dst_rq = target_rq,
8208 .src_cpu = busiest_rq->cpu,
8209 .src_rq = busiest_rq,
8213 schedstat_inc(sd, alb_count);
8215 p = detach_one_task(&env);
8217 schedstat_inc(sd, alb_pushed);
8219 * We want to potentially lower env.src_cpu's OPP.
8221 update_capacity_of(env.src_cpu);
8224 schedstat_inc(sd, alb_failed);
8228 busiest_rq->active_balance = 0;
8229 raw_spin_unlock(&busiest_rq->lock);
8232 attach_one_task(target_rq, p);
8239 static inline int on_null_domain(struct rq *rq)
8241 return unlikely(!rcu_dereference_sched(rq->sd));
8244 #ifdef CONFIG_NO_HZ_COMMON
8246 * idle load balancing details
8247 * - When one of the busy CPUs notice that there may be an idle rebalancing
8248 * needed, they will kick the idle load balancer, which then does idle
8249 * load balancing for all the idle CPUs.
8252 cpumask_var_t idle_cpus_mask;
8254 unsigned long next_balance; /* in jiffy units */
8255 } nohz ____cacheline_aligned;
8257 static inline int find_new_ilb(void)
8259 int ilb = cpumask_first(nohz.idle_cpus_mask);
8261 if (ilb < nr_cpu_ids && idle_cpu(ilb))
8268 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
8269 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
8270 * CPU (if there is one).
8272 static void nohz_balancer_kick(void)
8276 nohz.next_balance++;
8278 ilb_cpu = find_new_ilb();
8280 if (ilb_cpu >= nr_cpu_ids)
8283 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
8286 * Use smp_send_reschedule() instead of resched_cpu().
8287 * This way we generate a sched IPI on the target cpu which
8288 * is idle. And the softirq performing nohz idle load balance
8289 * will be run before returning from the IPI.
8291 smp_send_reschedule(ilb_cpu);
8295 static inline void nohz_balance_exit_idle(int cpu)
8297 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
8299 * Completely isolated CPUs don't ever set, so we must test.
8301 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
8302 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
8303 atomic_dec(&nohz.nr_cpus);
8305 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8309 static inline void set_cpu_sd_state_busy(void)
8311 struct sched_domain *sd;
8312 int cpu = smp_processor_id();
8315 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8317 if (!sd || !sd->nohz_idle)
8321 atomic_inc(&sd->groups->sgc->nr_busy_cpus);
8326 void set_cpu_sd_state_idle(void)
8328 struct sched_domain *sd;
8329 int cpu = smp_processor_id();
8332 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8334 if (!sd || sd->nohz_idle)
8338 atomic_dec(&sd->groups->sgc->nr_busy_cpus);
8344 * This routine will record that the cpu is going idle with tick stopped.
8345 * This info will be used in performing idle load balancing in the future.
8347 void nohz_balance_enter_idle(int cpu)
8350 * If this cpu is going down, then nothing needs to be done.
8352 if (!cpu_active(cpu))
8355 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
8359 * If we're a completely isolated CPU, we don't play.
8361 if (on_null_domain(cpu_rq(cpu)))
8364 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
8365 atomic_inc(&nohz.nr_cpus);
8366 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8369 static int sched_ilb_notifier(struct notifier_block *nfb,
8370 unsigned long action, void *hcpu)
8372 switch (action & ~CPU_TASKS_FROZEN) {
8374 nohz_balance_exit_idle(smp_processor_id());
8382 static DEFINE_SPINLOCK(balancing);
8385 * Scale the max load_balance interval with the number of CPUs in the system.
8386 * This trades load-balance latency on larger machines for less cross talk.
8388 void update_max_interval(void)
8390 max_load_balance_interval = HZ*num_online_cpus()/10;
8394 * It checks each scheduling domain to see if it is due to be balanced,
8395 * and initiates a balancing operation if so.
8397 * Balancing parameters are set up in init_sched_domains.
8399 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8401 int continue_balancing = 1;
8403 unsigned long interval;
8404 struct sched_domain *sd;
8405 /* Earliest time when we have to do rebalance again */
8406 unsigned long next_balance = jiffies + 60*HZ;
8407 int update_next_balance = 0;
8408 int need_serialize, need_decay = 0;
8411 update_blocked_averages(cpu);
8414 for_each_domain(cpu, sd) {
8416 * Decay the newidle max times here because this is a regular
8417 * visit to all the domains. Decay ~1% per second.
8419 if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
8420 sd->max_newidle_lb_cost =
8421 (sd->max_newidle_lb_cost * 253) / 256;
8422 sd->next_decay_max_lb_cost = jiffies + HZ;
8425 max_cost += sd->max_newidle_lb_cost;
8427 if (!(sd->flags & SD_LOAD_BALANCE))
8431 * Stop the load balance at this level. There is another
8432 * CPU in our sched group which is doing load balancing more
8435 if (!continue_balancing) {
8441 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8443 need_serialize = sd->flags & SD_SERIALIZE;
8444 if (need_serialize) {
8445 if (!spin_trylock(&balancing))
8449 if (time_after_eq(jiffies, sd->last_balance + interval)) {
8450 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8452 * The LBF_DST_PINNED logic could have changed
8453 * env->dst_cpu, so we can't know our idle
8454 * state even if we migrated tasks. Update it.
8456 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8458 sd->last_balance = jiffies;
8459 interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8462 spin_unlock(&balancing);
8464 if (time_after(next_balance, sd->last_balance + interval)) {
8465 next_balance = sd->last_balance + interval;
8466 update_next_balance = 1;
8471 * Ensure the rq-wide value also decays but keep it at a
8472 * reasonable floor to avoid funnies with rq->avg_idle.
8474 rq->max_idle_balance_cost =
8475 max((u64)sysctl_sched_migration_cost, max_cost);
8480 * next_balance will be updated only when there is a need.
8481 * When the cpu is attached to null domain for ex, it will not be
8484 if (likely(update_next_balance)) {
8485 rq->next_balance = next_balance;
8487 #ifdef CONFIG_NO_HZ_COMMON
8489 * If this CPU has been elected to perform the nohz idle
8490 * balance. Other idle CPUs have already rebalanced with
8491 * nohz_idle_balance() and nohz.next_balance has been
8492 * updated accordingly. This CPU is now running the idle load
8493 * balance for itself and we need to update the
8494 * nohz.next_balance accordingly.
8496 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
8497 nohz.next_balance = rq->next_balance;
8502 #ifdef CONFIG_NO_HZ_COMMON
8504 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8505 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8507 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8509 int this_cpu = this_rq->cpu;
8512 /* Earliest time when we have to do rebalance again */
8513 unsigned long next_balance = jiffies + 60*HZ;
8514 int update_next_balance = 0;
8516 if (idle != CPU_IDLE ||
8517 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
8520 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8521 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8525 * If this cpu gets work to do, stop the load balancing
8526 * work being done for other cpus. Next load
8527 * balancing owner will pick it up.
8532 rq = cpu_rq(balance_cpu);
8535 * If time for next balance is due,
8538 if (time_after_eq(jiffies, rq->next_balance)) {
8539 raw_spin_lock_irq(&rq->lock);
8540 update_rq_clock(rq);
8541 update_idle_cpu_load(rq);
8542 raw_spin_unlock_irq(&rq->lock);
8543 rebalance_domains(rq, CPU_IDLE);
8546 if (time_after(next_balance, rq->next_balance)) {
8547 next_balance = rq->next_balance;
8548 update_next_balance = 1;
8553 * next_balance will be updated only when there is a need.
8554 * When the CPU is attached to null domain for ex, it will not be
8557 if (likely(update_next_balance))
8558 nohz.next_balance = next_balance;
8560 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8564 * Current heuristic for kicking the idle load balancer in the presence
8565 * of an idle cpu in the system.
8566 * - This rq has more than one task.
8567 * - This rq has at least one CFS task and the capacity of the CPU is
8568 * significantly reduced because of RT tasks or IRQs.
8569 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8570 * multiple busy cpu.
8571 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8572 * domain span are idle.
8574 static inline bool nohz_kick_needed(struct rq *rq)
8576 unsigned long now = jiffies;
8577 struct sched_domain *sd;
8578 struct sched_group_capacity *sgc;
8579 int nr_busy, cpu = rq->cpu;
8582 if (unlikely(rq->idle_balance))
8586 * We may be recently in ticked or tickless idle mode. At the first
8587 * busy tick after returning from idle, we will update the busy stats.
8589 set_cpu_sd_state_busy();
8590 nohz_balance_exit_idle(cpu);
8593 * None are in tickless mode and hence no need for NOHZ idle load
8596 if (likely(!atomic_read(&nohz.nr_cpus)))
8599 if (time_before(now, nohz.next_balance))
8602 if (rq->nr_running >= 2 &&
8603 (!energy_aware() || cpu_overutilized(cpu)))
8607 sd = rcu_dereference(per_cpu(sd_busy, cpu));
8608 if (sd && !energy_aware()) {
8609 sgc = sd->groups->sgc;
8610 nr_busy = atomic_read(&sgc->nr_busy_cpus);
8619 sd = rcu_dereference(rq->sd);
8621 if ((rq->cfs.h_nr_running >= 1) &&
8622 check_cpu_capacity(rq, sd)) {
8628 sd = rcu_dereference(per_cpu(sd_asym, cpu));
8629 if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8630 sched_domain_span(sd)) < cpu)) {
8640 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8644 * run_rebalance_domains is triggered when needed from the scheduler tick.
8645 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8647 static void run_rebalance_domains(struct softirq_action *h)
8649 struct rq *this_rq = this_rq();
8650 enum cpu_idle_type idle = this_rq->idle_balance ?
8651 CPU_IDLE : CPU_NOT_IDLE;
8654 * If this cpu has a pending nohz_balance_kick, then do the
8655 * balancing on behalf of the other idle cpus whose ticks are
8656 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8657 * give the idle cpus a chance to load balance. Else we may
8658 * load balance only within the local sched_domain hierarchy
8659 * and abort nohz_idle_balance altogether if we pull some load.
8661 nohz_idle_balance(this_rq, idle);
8662 rebalance_domains(this_rq, idle);
8666 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8668 void trigger_load_balance(struct rq *rq)
8670 /* Don't need to rebalance while attached to NULL domain */
8671 if (unlikely(on_null_domain(rq)))
8674 if (time_after_eq(jiffies, rq->next_balance))
8675 raise_softirq(SCHED_SOFTIRQ);
8676 #ifdef CONFIG_NO_HZ_COMMON
8677 if (nohz_kick_needed(rq))
8678 nohz_balancer_kick();
8682 static void rq_online_fair(struct rq *rq)
8686 update_runtime_enabled(rq);
8689 static void rq_offline_fair(struct rq *rq)
8693 /* Ensure any throttled groups are reachable by pick_next_task */
8694 unthrottle_offline_cfs_rqs(rq);
8697 #endif /* CONFIG_SMP */
8700 * scheduler tick hitting a task of our scheduling class:
8702 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8704 struct cfs_rq *cfs_rq;
8705 struct sched_entity *se = &curr->se;
8707 for_each_sched_entity(se) {
8708 cfs_rq = cfs_rq_of(se);
8709 entity_tick(cfs_rq, se, queued);
8712 if (static_branch_unlikely(&sched_numa_balancing))
8713 task_tick_numa(rq, curr);
8715 if (!rq->rd->overutilized && cpu_overutilized(task_cpu(curr)))
8716 rq->rd->overutilized = true;
8718 rq->misfit_task = !task_fits_max(curr, rq->cpu);
8722 * called on fork with the child task as argument from the parent's context
8723 * - child not yet on the tasklist
8724 * - preemption disabled
8726 static void task_fork_fair(struct task_struct *p)
8728 struct cfs_rq *cfs_rq;
8729 struct sched_entity *se = &p->se, *curr;
8730 int this_cpu = smp_processor_id();
8731 struct rq *rq = this_rq();
8732 unsigned long flags;
8734 raw_spin_lock_irqsave(&rq->lock, flags);
8736 update_rq_clock(rq);
8738 cfs_rq = task_cfs_rq(current);
8739 curr = cfs_rq->curr;
8742 * Not only the cpu but also the task_group of the parent might have
8743 * been changed after parent->se.parent,cfs_rq were copied to
8744 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8745 * of child point to valid ones.
8748 __set_task_cpu(p, this_cpu);
8751 update_curr(cfs_rq);
8754 se->vruntime = curr->vruntime;
8755 place_entity(cfs_rq, se, 1);
8757 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
8759 * Upon rescheduling, sched_class::put_prev_task() will place
8760 * 'current' within the tree based on its new key value.
8762 swap(curr->vruntime, se->vruntime);
8766 se->vruntime -= cfs_rq->min_vruntime;
8768 raw_spin_unlock_irqrestore(&rq->lock, flags);
8772 * Priority of the task has changed. Check to see if we preempt
8776 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8778 if (!task_on_rq_queued(p))
8782 * Reschedule if we are currently running on this runqueue and
8783 * our priority decreased, or if we are not currently running on
8784 * this runqueue and our priority is higher than the current's
8786 if (rq->curr == p) {
8787 if (p->prio > oldprio)
8790 check_preempt_curr(rq, p, 0);
8793 static inline bool vruntime_normalized(struct task_struct *p)
8795 struct sched_entity *se = &p->se;
8798 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8799 * the dequeue_entity(.flags=0) will already have normalized the
8806 * When !on_rq, vruntime of the task has usually NOT been normalized.
8807 * But there are some cases where it has already been normalized:
8809 * - A forked child which is waiting for being woken up by
8810 * wake_up_new_task().
8811 * - A task which has been woken up by try_to_wake_up() and
8812 * waiting for actually being woken up by sched_ttwu_pending().
8814 if (!se->sum_exec_runtime || p->state == TASK_WAKING)
8820 static void detach_task_cfs_rq(struct task_struct *p)
8822 struct sched_entity *se = &p->se;
8823 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8825 if (!vruntime_normalized(p)) {
8827 * Fix up our vruntime so that the current sleep doesn't
8828 * cause 'unlimited' sleep bonus.
8830 place_entity(cfs_rq, se, 0);
8831 se->vruntime -= cfs_rq->min_vruntime;
8834 /* Catch up with the cfs_rq and remove our load when we leave */
8835 detach_entity_load_avg(cfs_rq, se);
8838 static void attach_task_cfs_rq(struct task_struct *p)
8840 struct sched_entity *se = &p->se;
8841 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8843 #ifdef CONFIG_FAIR_GROUP_SCHED
8845 * Since the real-depth could have been changed (only FAIR
8846 * class maintain depth value), reset depth properly.
8848 se->depth = se->parent ? se->parent->depth + 1 : 0;
8851 /* Synchronize task with its cfs_rq */
8852 attach_entity_load_avg(cfs_rq, se);
8854 if (!vruntime_normalized(p))
8855 se->vruntime += cfs_rq->min_vruntime;
8858 static void switched_from_fair(struct rq *rq, struct task_struct *p)
8860 detach_task_cfs_rq(p);
8863 static void switched_to_fair(struct rq *rq, struct task_struct *p)
8865 attach_task_cfs_rq(p);
8867 if (task_on_rq_queued(p)) {
8869 * We were most likely switched from sched_rt, so
8870 * kick off the schedule if running, otherwise just see
8871 * if we can still preempt the current task.
8876 check_preempt_curr(rq, p, 0);
8880 /* Account for a task changing its policy or group.
8882 * This routine is mostly called to set cfs_rq->curr field when a task
8883 * migrates between groups/classes.
8885 static void set_curr_task_fair(struct rq *rq)
8887 struct sched_entity *se = &rq->curr->se;
8889 for_each_sched_entity(se) {
8890 struct cfs_rq *cfs_rq = cfs_rq_of(se);
8892 set_next_entity(cfs_rq, se);
8893 /* ensure bandwidth has been allocated on our new cfs_rq */
8894 account_cfs_rq_runtime(cfs_rq, 0);
8898 void init_cfs_rq(struct cfs_rq *cfs_rq)
8900 cfs_rq->tasks_timeline = RB_ROOT;
8901 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
8902 #ifndef CONFIG_64BIT
8903 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
8906 atomic_long_set(&cfs_rq->removed_load_avg, 0);
8907 atomic_long_set(&cfs_rq->removed_util_avg, 0);
8911 #ifdef CONFIG_FAIR_GROUP_SCHED
8912 static void task_move_group_fair(struct task_struct *p)
8914 detach_task_cfs_rq(p);
8915 set_task_rq(p, task_cpu(p));
8918 /* Tell se's cfs_rq has been changed -- migrated */
8919 p->se.avg.last_update_time = 0;
8921 attach_task_cfs_rq(p);
8924 void free_fair_sched_group(struct task_group *tg)
8928 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
8930 for_each_possible_cpu(i) {
8932 kfree(tg->cfs_rq[i]);
8935 remove_entity_load_avg(tg->se[i]);
8944 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
8946 struct cfs_rq *cfs_rq;
8947 struct sched_entity *se;
8950 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
8953 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
8957 tg->shares = NICE_0_LOAD;
8959 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
8961 for_each_possible_cpu(i) {
8962 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
8963 GFP_KERNEL, cpu_to_node(i));
8967 se = kzalloc_node(sizeof(struct sched_entity),
8968 GFP_KERNEL, cpu_to_node(i));
8972 init_cfs_rq(cfs_rq);
8973 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
8974 init_entity_runnable_average(se);
8985 void unregister_fair_sched_group(struct task_group *tg, int cpu)
8987 struct rq *rq = cpu_rq(cpu);
8988 unsigned long flags;
8991 * Only empty task groups can be destroyed; so we can speculatively
8992 * check on_list without danger of it being re-added.
8994 if (!tg->cfs_rq[cpu]->on_list)
8997 raw_spin_lock_irqsave(&rq->lock, flags);
8998 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
8999 raw_spin_unlock_irqrestore(&rq->lock, flags);
9002 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
9003 struct sched_entity *se, int cpu,
9004 struct sched_entity *parent)
9006 struct rq *rq = cpu_rq(cpu);
9010 init_cfs_rq_runtime(cfs_rq);
9012 tg->cfs_rq[cpu] = cfs_rq;
9015 /* se could be NULL for root_task_group */
9020 se->cfs_rq = &rq->cfs;
9023 se->cfs_rq = parent->my_q;
9024 se->depth = parent->depth + 1;
9028 /* guarantee group entities always have weight */
9029 update_load_set(&se->load, NICE_0_LOAD);
9030 se->parent = parent;
9033 static DEFINE_MUTEX(shares_mutex);
9035 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
9038 unsigned long flags;
9041 * We can't change the weight of the root cgroup.
9046 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
9048 mutex_lock(&shares_mutex);
9049 if (tg->shares == shares)
9052 tg->shares = shares;
9053 for_each_possible_cpu(i) {
9054 struct rq *rq = cpu_rq(i);
9055 struct sched_entity *se;
9058 /* Propagate contribution to hierarchy */
9059 raw_spin_lock_irqsave(&rq->lock, flags);
9061 /* Possible calls to update_curr() need rq clock */
9062 update_rq_clock(rq);
9063 for_each_sched_entity(se)
9064 update_cfs_shares(group_cfs_rq(se));
9065 raw_spin_unlock_irqrestore(&rq->lock, flags);
9069 mutex_unlock(&shares_mutex);
9072 #else /* CONFIG_FAIR_GROUP_SCHED */
9074 void free_fair_sched_group(struct task_group *tg) { }
9076 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
9081 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
9083 #endif /* CONFIG_FAIR_GROUP_SCHED */
9086 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
9088 struct sched_entity *se = &task->se;
9089 unsigned int rr_interval = 0;
9092 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
9095 if (rq->cfs.load.weight)
9096 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
9102 * All the scheduling class methods:
9104 const struct sched_class fair_sched_class = {
9105 .next = &idle_sched_class,
9106 .enqueue_task = enqueue_task_fair,
9107 .dequeue_task = dequeue_task_fair,
9108 .yield_task = yield_task_fair,
9109 .yield_to_task = yield_to_task_fair,
9111 .check_preempt_curr = check_preempt_wakeup,
9113 .pick_next_task = pick_next_task_fair,
9114 .put_prev_task = put_prev_task_fair,
9117 .select_task_rq = select_task_rq_fair,
9118 .migrate_task_rq = migrate_task_rq_fair,
9120 .rq_online = rq_online_fair,
9121 .rq_offline = rq_offline_fair,
9123 .task_waking = task_waking_fair,
9124 .task_dead = task_dead_fair,
9125 .set_cpus_allowed = set_cpus_allowed_common,
9128 .set_curr_task = set_curr_task_fair,
9129 .task_tick = task_tick_fair,
9130 .task_fork = task_fork_fair,
9132 .prio_changed = prio_changed_fair,
9133 .switched_from = switched_from_fair,
9134 .switched_to = switched_to_fair,
9136 .get_rr_interval = get_rr_interval_fair,
9138 .update_curr = update_curr_fair,
9140 #ifdef CONFIG_FAIR_GROUP_SCHED
9141 .task_move_group = task_move_group_fair,
9145 #ifdef CONFIG_SCHED_DEBUG
9146 void print_cfs_stats(struct seq_file *m, int cpu)
9148 struct cfs_rq *cfs_rq;
9151 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
9152 print_cfs_rq(m, cpu, cfs_rq);
9156 #ifdef CONFIG_NUMA_BALANCING
9157 void show_numa_stats(struct task_struct *p, struct seq_file *m)
9160 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
9162 for_each_online_node(node) {
9163 if (p->numa_faults) {
9164 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
9165 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
9167 if (p->numa_group) {
9168 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
9169 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
9171 print_numa_stats(m, node, tsf, tpf, gsf, gpf);
9174 #endif /* CONFIG_NUMA_BALANCING */
9175 #endif /* CONFIG_SCHED_DEBUG */
9177 __init void init_sched_fair_class(void)
9180 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
9182 #ifdef CONFIG_NO_HZ_COMMON
9183 nohz.next_balance = jiffies;
9184 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
9185 cpu_notifier(sched_ilb_notifier, 0);