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 <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
26 #include <linux/slab.h>
27 #include <linux/profile.h>
28 #include <linux/interrupt.h>
29 #include <linux/mempolicy.h>
30 #include <linux/task_work.h>
32 #include <trace/events/sched.h>
37 * Targeted preemption latency for CPU-bound tasks:
38 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
40 * NOTE: this latency value is not the same as the concept of
41 * 'timeslice length' - timeslices in CFS are of variable length
42 * and have no persistent notion like in traditional, time-slice
43 * based scheduling concepts.
45 * (to see the precise effective timeslice length of your workload,
46 * run vmstat and monitor the context-switches (cs) field)
48 unsigned int sysctl_sched_latency = 6000000ULL;
49 unsigned int normalized_sysctl_sched_latency = 6000000ULL;
52 * The initial- and re-scaling of tunables is configurable
53 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
56 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
57 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
58 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
60 enum sched_tunable_scaling sysctl_sched_tunable_scaling
61 = SCHED_TUNABLESCALING_LOG;
64 * Minimal preemption granularity for CPU-bound tasks:
65 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
67 unsigned int sysctl_sched_min_granularity = 750000ULL;
68 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
71 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
73 static unsigned int sched_nr_latency = 8;
76 * After fork, child runs first. If set to 0 (default) then
77 * parent will (try to) run first.
79 unsigned int sysctl_sched_child_runs_first __read_mostly;
82 * SCHED_OTHER wake-up granularity.
83 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
85 * This option delays the preemption effects of decoupled workloads
86 * and reduces their over-scheduling. Synchronous workloads will still
87 * have immediate wakeup/sleep latencies.
89 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
90 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
92 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
95 * The exponential sliding window over which load is averaged for shares
99 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;
101 #ifdef CONFIG_CFS_BANDWIDTH
103 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
104 * each time a cfs_rq requests quota.
106 * Note: in the case that the slice exceeds the runtime remaining (either due
107 * to consumption or the quota being specified to be smaller than the slice)
108 * we will always only issue the remaining available time.
110 * default: 5 msec, units: microseconds
112 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
116 * Increase the granularity value when there are more CPUs,
117 * because with more CPUs the 'effective latency' as visible
118 * to users decreases. But the relationship is not linear,
119 * so pick a second-best guess by going with the log2 of the
122 * This idea comes from the SD scheduler of Con Kolivas:
124 static int get_update_sysctl_factor(void)
126 unsigned int cpus = min_t(int, num_online_cpus(), 8);
129 switch (sysctl_sched_tunable_scaling) {
130 case SCHED_TUNABLESCALING_NONE:
133 case SCHED_TUNABLESCALING_LINEAR:
136 case SCHED_TUNABLESCALING_LOG:
138 factor = 1 + ilog2(cpus);
145 static void update_sysctl(void)
147 unsigned int factor = get_update_sysctl_factor();
149 #define SET_SYSCTL(name) \
150 (sysctl_##name = (factor) * normalized_sysctl_##name)
151 SET_SYSCTL(sched_min_granularity);
152 SET_SYSCTL(sched_latency);
153 SET_SYSCTL(sched_wakeup_granularity);
157 void sched_init_granularity(void)
162 #if BITS_PER_LONG == 32
163 # define WMULT_CONST (~0UL)
165 # define WMULT_CONST (1UL << 32)
168 #define WMULT_SHIFT 32
171 * Shift right and round:
173 #define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))
176 * delta *= weight / lw
179 calc_delta_mine(unsigned long delta_exec, unsigned long weight,
180 struct load_weight *lw)
185 * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
186 * entities since MIN_SHARES = 2. Treat weight as 1 if less than
187 * 2^SCHED_LOAD_RESOLUTION.
189 if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
190 tmp = (u64)delta_exec * scale_load_down(weight);
192 tmp = (u64)delta_exec;
194 if (!lw->inv_weight) {
195 unsigned long w = scale_load_down(lw->weight);
197 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
199 else if (unlikely(!w))
200 lw->inv_weight = WMULT_CONST;
202 lw->inv_weight = WMULT_CONST / w;
206 * Check whether we'd overflow the 64-bit multiplication:
208 if (unlikely(tmp > WMULT_CONST))
209 tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
212 tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);
214 return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
218 const struct sched_class fair_sched_class;
220 /**************************************************************
221 * CFS operations on generic schedulable entities:
224 #ifdef CONFIG_FAIR_GROUP_SCHED
226 /* cpu runqueue to which this cfs_rq is attached */
227 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
232 /* An entity is a task if it doesn't "own" a runqueue */
233 #define entity_is_task(se) (!se->my_q)
235 static inline struct task_struct *task_of(struct sched_entity *se)
237 #ifdef CONFIG_SCHED_DEBUG
238 WARN_ON_ONCE(!entity_is_task(se));
240 return container_of(se, struct task_struct, se);
243 /* Walk up scheduling entities hierarchy */
244 #define for_each_sched_entity(se) \
245 for (; se; se = se->parent)
247 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
252 /* runqueue on which this entity is (to be) queued */
253 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
258 /* runqueue "owned" by this group */
259 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
264 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
266 if (!cfs_rq->on_list) {
268 * Ensure we either appear before our parent (if already
269 * enqueued) or force our parent to appear after us when it is
270 * enqueued. The fact that we always enqueue bottom-up
271 * reduces this to two cases.
273 if (cfs_rq->tg->parent &&
274 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
275 list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
276 &rq_of(cfs_rq)->leaf_cfs_rq_list);
278 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
279 &rq_of(cfs_rq)->leaf_cfs_rq_list);
286 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
288 if (cfs_rq->on_list) {
289 list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
294 /* Iterate thr' all leaf cfs_rq's on a runqueue */
295 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
296 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
298 /* Do the two (enqueued) entities belong to the same group ? */
300 is_same_group(struct sched_entity *se, struct sched_entity *pse)
302 if (se->cfs_rq == pse->cfs_rq)
308 static inline struct sched_entity *parent_entity(struct sched_entity *se)
313 /* return depth at which a sched entity is present in the hierarchy */
314 static inline int depth_se(struct sched_entity *se)
318 for_each_sched_entity(se)
325 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
327 int se_depth, pse_depth;
330 * preemption test can be made between sibling entities who are in the
331 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
332 * both tasks until we find their ancestors who are siblings of common
336 /* First walk up until both entities are at same depth */
337 se_depth = depth_se(*se);
338 pse_depth = depth_se(*pse);
340 while (se_depth > pse_depth) {
342 *se = parent_entity(*se);
345 while (pse_depth > se_depth) {
347 *pse = parent_entity(*pse);
350 while (!is_same_group(*se, *pse)) {
351 *se = parent_entity(*se);
352 *pse = parent_entity(*pse);
356 #else /* !CONFIG_FAIR_GROUP_SCHED */
358 static inline struct task_struct *task_of(struct sched_entity *se)
360 return container_of(se, struct task_struct, se);
363 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
365 return container_of(cfs_rq, struct rq, cfs);
368 #define entity_is_task(se) 1
370 #define for_each_sched_entity(se) \
371 for (; se; se = NULL)
373 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
375 return &task_rq(p)->cfs;
378 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
380 struct task_struct *p = task_of(se);
381 struct rq *rq = task_rq(p);
386 /* runqueue "owned" by this group */
387 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
392 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
396 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
400 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
401 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
404 is_same_group(struct sched_entity *se, struct sched_entity *pse)
409 static inline struct sched_entity *parent_entity(struct sched_entity *se)
415 find_matching_se(struct sched_entity **se, struct sched_entity **pse)
419 #endif /* CONFIG_FAIR_GROUP_SCHED */
421 static __always_inline
422 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec);
424 /**************************************************************
425 * Scheduling class tree data structure manipulation methods:
428 static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
430 s64 delta = (s64)(vruntime - min_vruntime);
432 min_vruntime = vruntime;
437 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
439 s64 delta = (s64)(vruntime - min_vruntime);
441 min_vruntime = vruntime;
446 static inline int entity_before(struct sched_entity *a,
447 struct sched_entity *b)
449 return (s64)(a->vruntime - b->vruntime) < 0;
452 static void update_min_vruntime(struct cfs_rq *cfs_rq)
454 u64 vruntime = cfs_rq->min_vruntime;
457 vruntime = cfs_rq->curr->vruntime;
459 if (cfs_rq->rb_leftmost) {
460 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
465 vruntime = se->vruntime;
467 vruntime = min_vruntime(vruntime, se->vruntime);
470 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
473 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
478 * Enqueue an entity into the rb-tree:
480 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
482 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
483 struct rb_node *parent = NULL;
484 struct sched_entity *entry;
488 * Find the right place in the rbtree:
492 entry = rb_entry(parent, struct sched_entity, run_node);
494 * We dont care about collisions. Nodes with
495 * the same key stay together.
497 if (entity_before(se, entry)) {
498 link = &parent->rb_left;
500 link = &parent->rb_right;
506 * Maintain a cache of leftmost tree entries (it is frequently
510 cfs_rq->rb_leftmost = &se->run_node;
512 rb_link_node(&se->run_node, parent, link);
513 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
516 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
518 if (cfs_rq->rb_leftmost == &se->run_node) {
519 struct rb_node *next_node;
521 next_node = rb_next(&se->run_node);
522 cfs_rq->rb_leftmost = next_node;
525 rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
528 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
530 struct rb_node *left = cfs_rq->rb_leftmost;
535 return rb_entry(left, struct sched_entity, run_node);
538 static struct sched_entity *__pick_next_entity(struct sched_entity *se)
540 struct rb_node *next = rb_next(&se->run_node);
545 return rb_entry(next, struct sched_entity, run_node);
548 #ifdef CONFIG_SCHED_DEBUG
549 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
551 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
556 return rb_entry(last, struct sched_entity, run_node);
559 /**************************************************************
560 * Scheduling class statistics methods:
563 int sched_proc_update_handler(struct ctl_table *table, int write,
564 void __user *buffer, size_t *lenp,
567 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
568 int factor = get_update_sysctl_factor();
573 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
574 sysctl_sched_min_granularity);
576 #define WRT_SYSCTL(name) \
577 (normalized_sysctl_##name = sysctl_##name / (factor))
578 WRT_SYSCTL(sched_min_granularity);
579 WRT_SYSCTL(sched_latency);
580 WRT_SYSCTL(sched_wakeup_granularity);
590 static inline unsigned long
591 calc_delta_fair(unsigned long delta, struct sched_entity *se)
593 if (unlikely(se->load.weight != NICE_0_LOAD))
594 delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load);
600 * The idea is to set a period in which each task runs once.
602 * When there are too many tasks (sched_nr_latency) we have to stretch
603 * this period because otherwise the slices get too small.
605 * p = (nr <= nl) ? l : l*nr/nl
607 static u64 __sched_period(unsigned long nr_running)
609 u64 period = sysctl_sched_latency;
610 unsigned long nr_latency = sched_nr_latency;
612 if (unlikely(nr_running > nr_latency)) {
613 period = sysctl_sched_min_granularity;
614 period *= nr_running;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
628 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
630 for_each_sched_entity(se) {
631 struct load_weight *load;
632 struct load_weight lw;
634 cfs_rq = cfs_rq_of(se);
635 load = &cfs_rq->load;
637 if (unlikely(!se->on_rq)) {
640 update_load_add(&lw, se->load.weight);
643 slice = calc_delta_mine(slice, se->load.weight, load);
649 * We calculate the vruntime slice of a to be inserted task
653 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
655 return calc_delta_fair(sched_slice(cfs_rq, se), se);
658 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
659 static void update_cfs_shares(struct cfs_rq *cfs_rq);
662 * Update the current task's runtime statistics. Skip current tasks that
663 * are not in our scheduling class.
666 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
667 unsigned long delta_exec)
669 unsigned long delta_exec_weighted;
671 schedstat_set(curr->statistics.exec_max,
672 max((u64)delta_exec, curr->statistics.exec_max));
674 curr->sum_exec_runtime += delta_exec;
675 schedstat_add(cfs_rq, exec_clock, delta_exec);
676 delta_exec_weighted = calc_delta_fair(delta_exec, curr);
678 curr->vruntime += delta_exec_weighted;
679 update_min_vruntime(cfs_rq);
681 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
682 cfs_rq->load_unacc_exec_time += delta_exec;
686 static void update_curr(struct cfs_rq *cfs_rq)
688 struct sched_entity *curr = cfs_rq->curr;
689 u64 now = rq_of(cfs_rq)->clock_task;
690 unsigned long delta_exec;
696 * Get the amount of time the current task was running
697 * since the last time we changed load (this cannot
698 * overflow on 32 bits):
700 delta_exec = (unsigned long)(now - curr->exec_start);
704 __update_curr(cfs_rq, curr, delta_exec);
705 curr->exec_start = now;
707 if (entity_is_task(curr)) {
708 struct task_struct *curtask = task_of(curr);
710 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
711 cpuacct_charge(curtask, delta_exec);
712 account_group_exec_runtime(curtask, delta_exec);
715 account_cfs_rq_runtime(cfs_rq, delta_exec);
719 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
721 schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
725 * Task is being enqueued - update stats:
727 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
730 * Are we enqueueing a waiting task? (for current tasks
731 * a dequeue/enqueue event is a NOP)
733 if (se != cfs_rq->curr)
734 update_stats_wait_start(cfs_rq, se);
738 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
740 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
741 rq_of(cfs_rq)->clock - se->statistics.wait_start));
742 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
743 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
744 rq_of(cfs_rq)->clock - se->statistics.wait_start);
745 #ifdef CONFIG_SCHEDSTATS
746 if (entity_is_task(se)) {
747 trace_sched_stat_wait(task_of(se),
748 rq_of(cfs_rq)->clock - se->statistics.wait_start);
751 schedstat_set(se->statistics.wait_start, 0);
755 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
758 * Mark the end of the wait period if dequeueing a
761 if (se != cfs_rq->curr)
762 update_stats_wait_end(cfs_rq, se);
766 * We are picking a new current task - update its stats:
769 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
772 * We are starting a new run period:
774 se->exec_start = rq_of(cfs_rq)->clock_task;
777 /**************************************************
778 * Scheduling class queueing methods:
781 #ifdef CONFIG_NUMA_BALANCING
783 * numa task sample period in ms
785 unsigned int sysctl_numa_balancing_scan_period_min = 100;
786 unsigned int sysctl_numa_balancing_scan_period_max = 100*16;
788 /* Portion of address space to scan in MB */
789 unsigned int sysctl_numa_balancing_scan_size = 256;
791 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
792 unsigned int sysctl_numa_balancing_scan_delay = 1000;
794 static void task_numa_placement(struct task_struct *p)
796 int seq = ACCESS_ONCE(p->mm->numa_scan_seq);
798 if (p->numa_scan_seq == seq)
800 p->numa_scan_seq = seq;
802 /* FIXME: Scheduling placement policy hints go here */
806 * Got a PROT_NONE fault for a page on @node.
808 void task_numa_fault(int node, int pages)
810 struct task_struct *p = current;
812 /* FIXME: Allocate task-specific structure for placement policy here */
814 task_numa_placement(p);
817 static void reset_ptenuma_scan(struct task_struct *p)
819 ACCESS_ONCE(p->mm->numa_scan_seq)++;
820 p->mm->numa_scan_offset = 0;
824 * The expensive part of numa migration is done from task_work context.
825 * Triggered from task_tick_numa().
827 void task_numa_work(struct callback_head *work)
829 unsigned long migrate, next_scan, now = jiffies;
830 struct task_struct *p = current;
831 struct mm_struct *mm = p->mm;
832 struct vm_area_struct *vma;
833 unsigned long start, end;
836 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
838 work->next = work; /* protect against double add */
840 * Who cares about NUMA placement when they're dying.
842 * NOTE: make sure not to dereference p->mm before this check,
843 * exit_task_work() happens _after_ exit_mm() so we could be called
844 * without p->mm even though we still had it when we enqueued this
847 if (p->flags & PF_EXITING)
851 * Enforce maximal scan/migration frequency..
853 migrate = mm->numa_next_scan;
854 if (time_before(now, migrate))
857 if (p->numa_scan_period == 0)
858 p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
860 next_scan = now + 2*msecs_to_jiffies(p->numa_scan_period);
861 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
864 start = mm->numa_scan_offset;
865 pages = sysctl_numa_balancing_scan_size;
866 pages <<= 20 - PAGE_SHIFT; /* MB in pages */
870 down_read(&mm->mmap_sem);
871 vma = find_vma(mm, start);
873 reset_ptenuma_scan(p);
877 for (; vma; vma = vma->vm_next) {
878 if (!vma_migratable(vma))
881 /* Skip small VMAs. They are not likely to be of relevance */
882 if (((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) < HPAGE_PMD_NR)
886 start = max(start, vma->vm_start);
887 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
888 end = min(end, vma->vm_end);
889 pages -= change_prot_numa(vma, start, end);
894 } while (end != vma->vm_end);
899 * It is possible to reach the end of the VMA list but the last few VMAs are
900 * not guaranteed to the vma_migratable. If they are not, we would find the
901 * !migratable VMA on the next scan but not reset the scanner to the start
905 mm->numa_scan_offset = start;
907 reset_ptenuma_scan(p);
908 up_read(&mm->mmap_sem);
912 * Drive the periodic memory faults..
914 void task_tick_numa(struct rq *rq, struct task_struct *curr)
916 struct callback_head *work = &curr->numa_work;
920 * We don't care about NUMA placement if we don't have memory.
922 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
926 * Using runtime rather than walltime has the dual advantage that
927 * we (mostly) drive the selection from busy threads and that the
928 * task needs to have done some actual work before we bother with
931 now = curr->se.sum_exec_runtime;
932 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
934 if (now - curr->node_stamp > period) {
935 if (!curr->node_stamp)
936 curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
937 curr->node_stamp = now;
939 if (!time_before(jiffies, curr->mm->numa_next_scan)) {
940 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
941 task_work_add(curr, work, true);
946 static void task_tick_numa(struct rq *rq, struct task_struct *curr)
949 #endif /* CONFIG_NUMA_BALANCING */
952 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
954 update_load_add(&cfs_rq->load, se->load.weight);
955 if (!parent_entity(se))
956 update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
958 if (entity_is_task(se))
959 list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
961 cfs_rq->nr_running++;
965 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
967 update_load_sub(&cfs_rq->load, se->load.weight);
968 if (!parent_entity(se))
969 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
970 if (entity_is_task(se))
971 list_del_init(&se->group_node);
972 cfs_rq->nr_running--;
975 #ifdef CONFIG_FAIR_GROUP_SCHED
976 /* we need this in update_cfs_load and load-balance functions below */
977 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);
979 static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
982 struct task_group *tg = cfs_rq->tg;
985 load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
986 load_avg -= cfs_rq->load_contribution;
988 if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
989 atomic_add(load_avg, &tg->load_weight);
990 cfs_rq->load_contribution += load_avg;
994 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
996 u64 period = sysctl_sched_shares_window;
998 unsigned long load = cfs_rq->load.weight;
1000 if (cfs_rq->tg == &root_task_group || throttled_hierarchy(cfs_rq))
1003 now = rq_of(cfs_rq)->clock_task;
1004 delta = now - cfs_rq->load_stamp;
1006 /* truncate load history at 4 idle periods */
1007 if (cfs_rq->load_stamp > cfs_rq->load_last &&
1008 now - cfs_rq->load_last > 4 * period) {
1009 cfs_rq->load_period = 0;
1010 cfs_rq->load_avg = 0;
1014 cfs_rq->load_stamp = now;
1015 cfs_rq->load_unacc_exec_time = 0;
1016 cfs_rq->load_period += delta;
1018 cfs_rq->load_last = now;
1019 cfs_rq->load_avg += delta * load;
1022 /* consider updating load contribution on each fold or truncate */
1023 if (global_update || cfs_rq->load_period > period
1024 || !cfs_rq->load_period)
1025 update_cfs_rq_load_contribution(cfs_rq, global_update);
1027 while (cfs_rq->load_period > period) {
1029 * Inline assembly required to prevent the compiler
1030 * optimising this loop into a divmod call.
1031 * See __iter_div_u64_rem() for another example of this.
1033 asm("" : "+rm" (cfs_rq->load_period));
1034 cfs_rq->load_period /= 2;
1035 cfs_rq->load_avg /= 2;
1038 if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
1039 list_del_leaf_cfs_rq(cfs_rq);
1042 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
1047 * Use this CPU's actual weight instead of the last load_contribution
1048 * to gain a more accurate current total weight. See
1049 * update_cfs_rq_load_contribution().
1051 tg_weight = atomic_read(&tg->load_weight);
1052 tg_weight -= cfs_rq->load_contribution;
1053 tg_weight += cfs_rq->load.weight;
1058 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1060 long tg_weight, load, shares;
1062 tg_weight = calc_tg_weight(tg, cfs_rq);
1063 load = cfs_rq->load.weight;
1065 shares = (tg->shares * load);
1067 shares /= tg_weight;
1069 if (shares < MIN_SHARES)
1070 shares = MIN_SHARES;
1071 if (shares > tg->shares)
1072 shares = tg->shares;
1077 static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
1079 if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
1080 update_cfs_load(cfs_rq, 0);
1081 update_cfs_shares(cfs_rq);
1084 # else /* CONFIG_SMP */
1085 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
1089 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1094 static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
1097 # endif /* CONFIG_SMP */
1098 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
1099 unsigned long weight)
1102 /* commit outstanding execution time */
1103 if (cfs_rq->curr == se)
1104 update_curr(cfs_rq);
1105 account_entity_dequeue(cfs_rq, se);
1108 update_load_set(&se->load, weight);
1111 account_entity_enqueue(cfs_rq, se);
1114 static void update_cfs_shares(struct cfs_rq *cfs_rq)
1116 struct task_group *tg;
1117 struct sched_entity *se;
1121 se = tg->se[cpu_of(rq_of(cfs_rq))];
1122 if (!se || throttled_hierarchy(cfs_rq))
1125 if (likely(se->load.weight == tg->shares))
1128 shares = calc_cfs_shares(cfs_rq, tg);
1130 reweight_entity(cfs_rq_of(se), se, shares);
1132 #else /* CONFIG_FAIR_GROUP_SCHED */
1133 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
1137 static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
1141 static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
1144 #endif /* CONFIG_FAIR_GROUP_SCHED */
1146 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1148 #ifdef CONFIG_SCHEDSTATS
1149 struct task_struct *tsk = NULL;
1151 if (entity_is_task(se))
1154 if (se->statistics.sleep_start) {
1155 u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
1160 if (unlikely(delta > se->statistics.sleep_max))
1161 se->statistics.sleep_max = delta;
1163 se->statistics.sleep_start = 0;
1164 se->statistics.sum_sleep_runtime += delta;
1167 account_scheduler_latency(tsk, delta >> 10, 1);
1168 trace_sched_stat_sleep(tsk, delta);
1171 if (se->statistics.block_start) {
1172 u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
1177 if (unlikely(delta > se->statistics.block_max))
1178 se->statistics.block_max = delta;
1180 se->statistics.block_start = 0;
1181 se->statistics.sum_sleep_runtime += delta;
1184 if (tsk->in_iowait) {
1185 se->statistics.iowait_sum += delta;
1186 se->statistics.iowait_count++;
1187 trace_sched_stat_iowait(tsk, delta);
1190 trace_sched_stat_blocked(tsk, delta);
1193 * Blocking time is in units of nanosecs, so shift by
1194 * 20 to get a milliseconds-range estimation of the
1195 * amount of time that the task spent sleeping:
1197 if (unlikely(prof_on == SLEEP_PROFILING)) {
1198 profile_hits(SLEEP_PROFILING,
1199 (void *)get_wchan(tsk),
1202 account_scheduler_latency(tsk, delta >> 10, 0);
1208 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
1210 #ifdef CONFIG_SCHED_DEBUG
1211 s64 d = se->vruntime - cfs_rq->min_vruntime;
1216 if (d > 3*sysctl_sched_latency)
1217 schedstat_inc(cfs_rq, nr_spread_over);
1222 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
1224 u64 vruntime = cfs_rq->min_vruntime;
1227 * The 'current' period is already promised to the current tasks,
1228 * however the extra weight of the new task will slow them down a
1229 * little, place the new task so that it fits in the slot that
1230 * stays open at the end.
1232 if (initial && sched_feat(START_DEBIT))
1233 vruntime += sched_vslice(cfs_rq, se);
1235 /* sleeps up to a single latency don't count. */
1237 unsigned long thresh = sysctl_sched_latency;
1240 * Halve their sleep time's effect, to allow
1241 * for a gentler effect of sleepers:
1243 if (sched_feat(GENTLE_FAIR_SLEEPERS))
1249 /* ensure we never gain time by being placed backwards. */
1250 vruntime = max_vruntime(se->vruntime, vruntime);
1252 se->vruntime = vruntime;
1255 static void check_enqueue_throttle(struct cfs_rq *cfs_rq);
1258 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1261 * Update the normalized vruntime before updating min_vruntime
1262 * through callig update_curr().
1264 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1265 se->vruntime += cfs_rq->min_vruntime;
1268 * Update run-time statistics of the 'current'.
1270 update_curr(cfs_rq);
1271 update_cfs_load(cfs_rq, 0);
1272 account_entity_enqueue(cfs_rq, se);
1273 update_cfs_shares(cfs_rq);
1275 if (flags & ENQUEUE_WAKEUP) {
1276 place_entity(cfs_rq, se, 0);
1277 enqueue_sleeper(cfs_rq, se);
1280 update_stats_enqueue(cfs_rq, se);
1281 check_spread(cfs_rq, se);
1282 if (se != cfs_rq->curr)
1283 __enqueue_entity(cfs_rq, se);
1286 if (cfs_rq->nr_running == 1) {
1287 list_add_leaf_cfs_rq(cfs_rq);
1288 check_enqueue_throttle(cfs_rq);
1292 static void __clear_buddies_last(struct sched_entity *se)
1294 for_each_sched_entity(se) {
1295 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1296 if (cfs_rq->last == se)
1297 cfs_rq->last = NULL;
1303 static void __clear_buddies_next(struct sched_entity *se)
1305 for_each_sched_entity(se) {
1306 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1307 if (cfs_rq->next == se)
1308 cfs_rq->next = NULL;
1314 static void __clear_buddies_skip(struct sched_entity *se)
1316 for_each_sched_entity(se) {
1317 struct cfs_rq *cfs_rq = cfs_rq_of(se);
1318 if (cfs_rq->skip == se)
1319 cfs_rq->skip = NULL;
1325 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
1327 if (cfs_rq->last == se)
1328 __clear_buddies_last(se);
1330 if (cfs_rq->next == se)
1331 __clear_buddies_next(se);
1333 if (cfs_rq->skip == se)
1334 __clear_buddies_skip(se);
1337 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1340 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1343 * Update run-time statistics of the 'current'.
1345 update_curr(cfs_rq);
1347 update_stats_dequeue(cfs_rq, se);
1348 if (flags & DEQUEUE_SLEEP) {
1349 #ifdef CONFIG_SCHEDSTATS
1350 if (entity_is_task(se)) {
1351 struct task_struct *tsk = task_of(se);
1353 if (tsk->state & TASK_INTERRUPTIBLE)
1354 se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1355 if (tsk->state & TASK_UNINTERRUPTIBLE)
1356 se->statistics.block_start = rq_of(cfs_rq)->clock;
1361 clear_buddies(cfs_rq, se);
1363 if (se != cfs_rq->curr)
1364 __dequeue_entity(cfs_rq, se);
1366 update_cfs_load(cfs_rq, 0);
1367 account_entity_dequeue(cfs_rq, se);
1370 * Normalize the entity after updating the min_vruntime because the
1371 * update can refer to the ->curr item and we need to reflect this
1372 * movement in our normalized position.
1374 if (!(flags & DEQUEUE_SLEEP))
1375 se->vruntime -= cfs_rq->min_vruntime;
1377 /* return excess runtime on last dequeue */
1378 return_cfs_rq_runtime(cfs_rq);
1380 update_min_vruntime(cfs_rq);
1381 update_cfs_shares(cfs_rq);
1385 * Preempt the current task with a newly woken task if needed:
1388 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1390 unsigned long ideal_runtime, delta_exec;
1391 struct sched_entity *se;
1394 ideal_runtime = sched_slice(cfs_rq, curr);
1395 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1396 if (delta_exec > ideal_runtime) {
1397 resched_task(rq_of(cfs_rq)->curr);
1399 * The current task ran long enough, ensure it doesn't get
1400 * re-elected due to buddy favours.
1402 clear_buddies(cfs_rq, curr);
1407 * Ensure that a task that missed wakeup preemption by a
1408 * narrow margin doesn't have to wait for a full slice.
1409 * This also mitigates buddy induced latencies under load.
1411 if (delta_exec < sysctl_sched_min_granularity)
1414 se = __pick_first_entity(cfs_rq);
1415 delta = curr->vruntime - se->vruntime;
1420 if (delta > ideal_runtime)
1421 resched_task(rq_of(cfs_rq)->curr);
1425 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1427 /* 'current' is not kept within the tree. */
1430 * Any task has to be enqueued before it get to execute on
1431 * a CPU. So account for the time it spent waiting on the
1434 update_stats_wait_end(cfs_rq, se);
1435 __dequeue_entity(cfs_rq, se);
1438 update_stats_curr_start(cfs_rq, se);
1440 #ifdef CONFIG_SCHEDSTATS
1442 * Track our maximum slice length, if the CPU's load is at
1443 * least twice that of our own weight (i.e. dont track it
1444 * when there are only lesser-weight tasks around):
1446 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1447 se->statistics.slice_max = max(se->statistics.slice_max,
1448 se->sum_exec_runtime - se->prev_sum_exec_runtime);
1451 se->prev_sum_exec_runtime = se->sum_exec_runtime;
1455 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
1458 * Pick the next process, keeping these things in mind, in this order:
1459 * 1) keep things fair between processes/task groups
1460 * 2) pick the "next" process, since someone really wants that to run
1461 * 3) pick the "last" process, for cache locality
1462 * 4) do not run the "skip" process, if something else is available
1464 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1466 struct sched_entity *se = __pick_first_entity(cfs_rq);
1467 struct sched_entity *left = se;
1470 * Avoid running the skip buddy, if running something else can
1471 * be done without getting too unfair.
1473 if (cfs_rq->skip == se) {
1474 struct sched_entity *second = __pick_next_entity(se);
1475 if (second && wakeup_preempt_entity(second, left) < 1)
1480 * Prefer last buddy, try to return the CPU to a preempted task.
1482 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
1486 * Someone really wants this to run. If it's not unfair, run it.
1488 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
1491 clear_buddies(cfs_rq, se);
1496 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1498 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1501 * If still on the runqueue then deactivate_task()
1502 * was not called and update_curr() has to be done:
1505 update_curr(cfs_rq);
1507 /* throttle cfs_rqs exceeding runtime */
1508 check_cfs_rq_runtime(cfs_rq);
1510 check_spread(cfs_rq, prev);
1512 update_stats_wait_start(cfs_rq, prev);
1513 /* Put 'current' back into the tree. */
1514 __enqueue_entity(cfs_rq, prev);
1516 cfs_rq->curr = NULL;
1520 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1523 * Update run-time statistics of the 'current'.
1525 update_curr(cfs_rq);
1528 * Update share accounting for long-running entities.
1530 update_entity_shares_tick(cfs_rq);
1532 #ifdef CONFIG_SCHED_HRTICK
1534 * queued ticks are scheduled to match the slice, so don't bother
1535 * validating it and just reschedule.
1538 resched_task(rq_of(cfs_rq)->curr);
1542 * don't let the period tick interfere with the hrtick preemption
1544 if (!sched_feat(DOUBLE_TICK) &&
1545 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
1549 if (cfs_rq->nr_running > 1)
1550 check_preempt_tick(cfs_rq, curr);
1554 /**************************************************
1555 * CFS bandwidth control machinery
1558 #ifdef CONFIG_CFS_BANDWIDTH
1560 #ifdef HAVE_JUMP_LABEL
1561 static struct static_key __cfs_bandwidth_used;
1563 static inline bool cfs_bandwidth_used(void)
1565 return static_key_false(&__cfs_bandwidth_used);
1568 void account_cfs_bandwidth_used(int enabled, int was_enabled)
1570 /* only need to count groups transitioning between enabled/!enabled */
1571 if (enabled && !was_enabled)
1572 static_key_slow_inc(&__cfs_bandwidth_used);
1573 else if (!enabled && was_enabled)
1574 static_key_slow_dec(&__cfs_bandwidth_used);
1576 #else /* HAVE_JUMP_LABEL */
1577 static bool cfs_bandwidth_used(void)
1582 void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
1583 #endif /* HAVE_JUMP_LABEL */
1586 * default period for cfs group bandwidth.
1587 * default: 0.1s, units: nanoseconds
1589 static inline u64 default_cfs_period(void)
1591 return 100000000ULL;
1594 static inline u64 sched_cfs_bandwidth_slice(void)
1596 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
1600 * Replenish runtime according to assigned quota and update expiration time.
1601 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
1602 * additional synchronization around rq->lock.
1604 * requires cfs_b->lock
1606 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
1610 if (cfs_b->quota == RUNTIME_INF)
1613 now = sched_clock_cpu(smp_processor_id());
1614 cfs_b->runtime = cfs_b->quota;
1615 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
1618 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
1620 return &tg->cfs_bandwidth;
1623 /* returns 0 on failure to allocate runtime */
1624 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
1626 struct task_group *tg = cfs_rq->tg;
1627 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
1628 u64 amount = 0, min_amount, expires;
1630 /* note: this is a positive sum as runtime_remaining <= 0 */
1631 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;
1633 raw_spin_lock(&cfs_b->lock);
1634 if (cfs_b->quota == RUNTIME_INF)
1635 amount = min_amount;
1638 * If the bandwidth pool has become inactive, then at least one
1639 * period must have elapsed since the last consumption.
1640 * Refresh the global state and ensure bandwidth timer becomes
1643 if (!cfs_b->timer_active) {
1644 __refill_cfs_bandwidth_runtime(cfs_b);
1645 __start_cfs_bandwidth(cfs_b);
1648 if (cfs_b->runtime > 0) {
1649 amount = min(cfs_b->runtime, min_amount);
1650 cfs_b->runtime -= amount;
1654 expires = cfs_b->runtime_expires;
1655 raw_spin_unlock(&cfs_b->lock);
1657 cfs_rq->runtime_remaining += amount;
1659 * we may have advanced our local expiration to account for allowed
1660 * spread between our sched_clock and the one on which runtime was
1663 if ((s64)(expires - cfs_rq->runtime_expires) > 0)
1664 cfs_rq->runtime_expires = expires;
1666 return cfs_rq->runtime_remaining > 0;
1670 * Note: This depends on the synchronization provided by sched_clock and the
1671 * fact that rq->clock snapshots this value.
1673 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
1675 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
1676 struct rq *rq = rq_of(cfs_rq);
1678 /* if the deadline is ahead of our clock, nothing to do */
1679 if (likely((s64)(rq->clock - cfs_rq->runtime_expires) < 0))
1682 if (cfs_rq->runtime_remaining < 0)
1686 * If the local deadline has passed we have to consider the
1687 * possibility that our sched_clock is 'fast' and the global deadline
1688 * has not truly expired.
1690 * Fortunately we can check determine whether this the case by checking
1691 * whether the global deadline has advanced.
1694 if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
1695 /* extend local deadline, drift is bounded above by 2 ticks */
1696 cfs_rq->runtime_expires += TICK_NSEC;
1698 /* global deadline is ahead, expiration has passed */
1699 cfs_rq->runtime_remaining = 0;
1703 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
1704 unsigned long delta_exec)
1706 /* dock delta_exec before expiring quota (as it could span periods) */
1707 cfs_rq->runtime_remaining -= delta_exec;
1708 expire_cfs_rq_runtime(cfs_rq);
1710 if (likely(cfs_rq->runtime_remaining > 0))
1714 * if we're unable to extend our runtime we resched so that the active
1715 * hierarchy can be throttled
1717 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
1718 resched_task(rq_of(cfs_rq)->curr);
1721 static __always_inline
1722 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
1724 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
1727 __account_cfs_rq_runtime(cfs_rq, delta_exec);
1730 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
1732 return cfs_bandwidth_used() && cfs_rq->throttled;
1735 /* check whether cfs_rq, or any parent, is throttled */
1736 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
1738 return cfs_bandwidth_used() && cfs_rq->throttle_count;
1742 * Ensure that neither of the group entities corresponding to src_cpu or
1743 * dest_cpu are members of a throttled hierarchy when performing group
1744 * load-balance operations.
1746 static inline int throttled_lb_pair(struct task_group *tg,
1747 int src_cpu, int dest_cpu)
1749 struct cfs_rq *src_cfs_rq, *dest_cfs_rq;
1751 src_cfs_rq = tg->cfs_rq[src_cpu];
1752 dest_cfs_rq = tg->cfs_rq[dest_cpu];
1754 return throttled_hierarchy(src_cfs_rq) ||
1755 throttled_hierarchy(dest_cfs_rq);
1758 /* updated child weight may affect parent so we have to do this bottom up */
1759 static int tg_unthrottle_up(struct task_group *tg, void *data)
1761 struct rq *rq = data;
1762 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
1764 cfs_rq->throttle_count--;
1766 if (!cfs_rq->throttle_count) {
1767 u64 delta = rq->clock_task - cfs_rq->load_stamp;
1769 /* leaving throttled state, advance shares averaging windows */
1770 cfs_rq->load_stamp += delta;
1771 cfs_rq->load_last += delta;
1773 /* update entity weight now that we are on_rq again */
1774 update_cfs_shares(cfs_rq);
1781 static int tg_throttle_down(struct task_group *tg, void *data)
1783 struct rq *rq = data;
1784 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
1786 /* group is entering throttled state, record last load */
1787 if (!cfs_rq->throttle_count)
1788 update_cfs_load(cfs_rq, 0);
1789 cfs_rq->throttle_count++;
1794 static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
1796 struct rq *rq = rq_of(cfs_rq);
1797 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
1798 struct sched_entity *se;
1799 long task_delta, dequeue = 1;
1801 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
1803 /* account load preceding throttle */
1805 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
1808 task_delta = cfs_rq->h_nr_running;
1809 for_each_sched_entity(se) {
1810 struct cfs_rq *qcfs_rq = cfs_rq_of(se);
1811 /* throttled entity or throttle-on-deactivate */
1816 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
1817 qcfs_rq->h_nr_running -= task_delta;
1819 if (qcfs_rq->load.weight)
1824 rq->nr_running -= task_delta;
1826 cfs_rq->throttled = 1;
1827 cfs_rq->throttled_timestamp = rq->clock;
1828 raw_spin_lock(&cfs_b->lock);
1829 list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
1830 raw_spin_unlock(&cfs_b->lock);
1833 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
1835 struct rq *rq = rq_of(cfs_rq);
1836 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
1837 struct sched_entity *se;
1841 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
1843 cfs_rq->throttled = 0;
1844 raw_spin_lock(&cfs_b->lock);
1845 cfs_b->throttled_time += rq->clock - cfs_rq->throttled_timestamp;
1846 list_del_rcu(&cfs_rq->throttled_list);
1847 raw_spin_unlock(&cfs_b->lock);
1848 cfs_rq->throttled_timestamp = 0;
1850 update_rq_clock(rq);
1851 /* update hierarchical throttle state */
1852 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);
1854 if (!cfs_rq->load.weight)
1857 task_delta = cfs_rq->h_nr_running;
1858 for_each_sched_entity(se) {
1862 cfs_rq = cfs_rq_of(se);
1864 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
1865 cfs_rq->h_nr_running += task_delta;
1867 if (cfs_rq_throttled(cfs_rq))
1872 rq->nr_running += task_delta;
1874 /* determine whether we need to wake up potentially idle cpu */
1875 if (rq->curr == rq->idle && rq->cfs.nr_running)
1876 resched_task(rq->curr);
1879 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
1880 u64 remaining, u64 expires)
1882 struct cfs_rq *cfs_rq;
1883 u64 runtime = remaining;
1886 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
1888 struct rq *rq = rq_of(cfs_rq);
1890 raw_spin_lock(&rq->lock);
1891 if (!cfs_rq_throttled(cfs_rq))
1894 runtime = -cfs_rq->runtime_remaining + 1;
1895 if (runtime > remaining)
1896 runtime = remaining;
1897 remaining -= runtime;
1899 cfs_rq->runtime_remaining += runtime;
1900 cfs_rq->runtime_expires = expires;
1902 /* we check whether we're throttled above */
1903 if (cfs_rq->runtime_remaining > 0)
1904 unthrottle_cfs_rq(cfs_rq);
1907 raw_spin_unlock(&rq->lock);
1918 * Responsible for refilling a task_group's bandwidth and unthrottling its
1919 * cfs_rqs as appropriate. If there has been no activity within the last
1920 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
1921 * used to track this state.
1923 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
1925 u64 runtime, runtime_expires;
1926 int idle = 1, throttled;
1928 raw_spin_lock(&cfs_b->lock);
1929 /* no need to continue the timer with no bandwidth constraint */
1930 if (cfs_b->quota == RUNTIME_INF)
1933 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
1934 /* idle depends on !throttled (for the case of a large deficit) */
1935 idle = cfs_b->idle && !throttled;
1936 cfs_b->nr_periods += overrun;
1938 /* if we're going inactive then everything else can be deferred */
1942 __refill_cfs_bandwidth_runtime(cfs_b);
1945 /* mark as potentially idle for the upcoming period */
1950 /* account preceding periods in which throttling occurred */
1951 cfs_b->nr_throttled += overrun;
1954 * There are throttled entities so we must first use the new bandwidth
1955 * to unthrottle them before making it generally available. This
1956 * ensures that all existing debts will be paid before a new cfs_rq is
1959 runtime = cfs_b->runtime;
1960 runtime_expires = cfs_b->runtime_expires;
1964 * This check is repeated as we are holding onto the new bandwidth
1965 * while we unthrottle. This can potentially race with an unthrottled
1966 * group trying to acquire new bandwidth from the global pool.
1968 while (throttled && runtime > 0) {
1969 raw_spin_unlock(&cfs_b->lock);
1970 /* we can't nest cfs_b->lock while distributing bandwidth */
1971 runtime = distribute_cfs_runtime(cfs_b, runtime,
1973 raw_spin_lock(&cfs_b->lock);
1975 throttled = !list_empty(&cfs_b->throttled_cfs_rq);
1978 /* return (any) remaining runtime */
1979 cfs_b->runtime = runtime;
1981 * While we are ensured activity in the period following an
1982 * unthrottle, this also covers the case in which the new bandwidth is
1983 * insufficient to cover the existing bandwidth deficit. (Forcing the
1984 * timer to remain active while there are any throttled entities.)
1989 cfs_b->timer_active = 0;
1990 raw_spin_unlock(&cfs_b->lock);
1995 /* a cfs_rq won't donate quota below this amount */
1996 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
1997 /* minimum remaining period time to redistribute slack quota */
1998 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
1999 /* how long we wait to gather additional slack before distributing */
2000 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
2002 /* are we near the end of the current quota period? */
2003 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
2005 struct hrtimer *refresh_timer = &cfs_b->period_timer;
2008 /* if the call-back is running a quota refresh is already occurring */
2009 if (hrtimer_callback_running(refresh_timer))
2012 /* is a quota refresh about to occur? */
2013 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
2014 if (remaining < min_expire)
2020 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
2022 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;
2024 /* if there's a quota refresh soon don't bother with slack */
2025 if (runtime_refresh_within(cfs_b, min_left))
2028 start_bandwidth_timer(&cfs_b->slack_timer,
2029 ns_to_ktime(cfs_bandwidth_slack_period));
2032 /* we know any runtime found here is valid as update_curr() precedes return */
2033 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2035 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2036 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;
2038 if (slack_runtime <= 0)
2041 raw_spin_lock(&cfs_b->lock);
2042 if (cfs_b->quota != RUNTIME_INF &&
2043 cfs_rq->runtime_expires == cfs_b->runtime_expires) {
2044 cfs_b->runtime += slack_runtime;
2046 /* we are under rq->lock, defer unthrottling using a timer */
2047 if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
2048 !list_empty(&cfs_b->throttled_cfs_rq))
2049 start_cfs_slack_bandwidth(cfs_b);
2051 raw_spin_unlock(&cfs_b->lock);
2053 /* even if it's not valid for return we don't want to try again */
2054 cfs_rq->runtime_remaining -= slack_runtime;
2057 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2059 if (!cfs_bandwidth_used())
2062 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
2065 __return_cfs_rq_runtime(cfs_rq);
2069 * This is done with a timer (instead of inline with bandwidth return) since
2070 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
2072 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
2074 u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
2077 /* confirm we're still not at a refresh boundary */
2078 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
2081 raw_spin_lock(&cfs_b->lock);
2082 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
2083 runtime = cfs_b->runtime;
2086 expires = cfs_b->runtime_expires;
2087 raw_spin_unlock(&cfs_b->lock);
2092 runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
2094 raw_spin_lock(&cfs_b->lock);
2095 if (expires == cfs_b->runtime_expires)
2096 cfs_b->runtime = runtime;
2097 raw_spin_unlock(&cfs_b->lock);
2101 * When a group wakes up we want to make sure that its quota is not already
2102 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
2103 * runtime as update_curr() throttling can not not trigger until it's on-rq.
2105 static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
2107 if (!cfs_bandwidth_used())
2110 /* an active group must be handled by the update_curr()->put() path */
2111 if (!cfs_rq->runtime_enabled || cfs_rq->curr)
2114 /* ensure the group is not already throttled */
2115 if (cfs_rq_throttled(cfs_rq))
2118 /* update runtime allocation */
2119 account_cfs_rq_runtime(cfs_rq, 0);
2120 if (cfs_rq->runtime_remaining <= 0)
2121 throttle_cfs_rq(cfs_rq);
2124 /* conditionally throttle active cfs_rq's from put_prev_entity() */
2125 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2127 if (!cfs_bandwidth_used())
2130 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
2134 * it's possible for a throttled entity to be forced into a running
2135 * state (e.g. set_curr_task), in this case we're finished.
2137 if (cfs_rq_throttled(cfs_rq))
2140 throttle_cfs_rq(cfs_rq);
2143 static inline u64 default_cfs_period(void);
2144 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun);
2145 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b);
2147 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
2149 struct cfs_bandwidth *cfs_b =
2150 container_of(timer, struct cfs_bandwidth, slack_timer);
2151 do_sched_cfs_slack_timer(cfs_b);
2153 return HRTIMER_NORESTART;
2156 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
2158 struct cfs_bandwidth *cfs_b =
2159 container_of(timer, struct cfs_bandwidth, period_timer);
2165 now = hrtimer_cb_get_time(timer);
2166 overrun = hrtimer_forward(timer, now, cfs_b->period);
2171 idle = do_sched_cfs_period_timer(cfs_b, overrun);
2174 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
2177 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2179 raw_spin_lock_init(&cfs_b->lock);
2181 cfs_b->quota = RUNTIME_INF;
2182 cfs_b->period = ns_to_ktime(default_cfs_period());
2184 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
2185 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
2186 cfs_b->period_timer.function = sched_cfs_period_timer;
2187 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
2188 cfs_b->slack_timer.function = sched_cfs_slack_timer;
2191 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2193 cfs_rq->runtime_enabled = 0;
2194 INIT_LIST_HEAD(&cfs_rq->throttled_list);
2197 /* requires cfs_b->lock, may release to reprogram timer */
2198 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2201 * The timer may be active because we're trying to set a new bandwidth
2202 * period or because we're racing with the tear-down path
2203 * (timer_active==0 becomes visible before the hrtimer call-back
2204 * terminates). In either case we ensure that it's re-programmed
2206 while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
2207 raw_spin_unlock(&cfs_b->lock);
2208 /* ensure cfs_b->lock is available while we wait */
2209 hrtimer_cancel(&cfs_b->period_timer);
2211 raw_spin_lock(&cfs_b->lock);
2212 /* if someone else restarted the timer then we're done */
2213 if (cfs_b->timer_active)
2217 cfs_b->timer_active = 1;
2218 start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
2221 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
2223 hrtimer_cancel(&cfs_b->period_timer);
2224 hrtimer_cancel(&cfs_b->slack_timer);
2227 static void unthrottle_offline_cfs_rqs(struct rq *rq)
2229 struct cfs_rq *cfs_rq;
2231 for_each_leaf_cfs_rq(rq, cfs_rq) {
2232 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
2234 if (!cfs_rq->runtime_enabled)
2238 * clock_task is not advancing so we just need to make sure
2239 * there's some valid quota amount
2241 cfs_rq->runtime_remaining = cfs_b->quota;
2242 if (cfs_rq_throttled(cfs_rq))
2243 unthrottle_cfs_rq(cfs_rq);
2247 #else /* CONFIG_CFS_BANDWIDTH */
2248 static __always_inline
2249 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) {}
2250 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2251 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2252 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2254 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
2259 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
2264 static inline int throttled_lb_pair(struct task_group *tg,
2265 int src_cpu, int dest_cpu)
2270 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2272 #ifdef CONFIG_FAIR_GROUP_SCHED
2273 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2276 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
2280 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
2281 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2283 #endif /* CONFIG_CFS_BANDWIDTH */
2285 /**************************************************
2286 * CFS operations on tasks:
2289 #ifdef CONFIG_SCHED_HRTICK
2290 static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
2292 struct sched_entity *se = &p->se;
2293 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2295 WARN_ON(task_rq(p) != rq);
2297 if (cfs_rq->nr_running > 1) {
2298 u64 slice = sched_slice(cfs_rq, se);
2299 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
2300 s64 delta = slice - ran;
2309 * Don't schedule slices shorter than 10000ns, that just
2310 * doesn't make sense. Rely on vruntime for fairness.
2313 delta = max_t(s64, 10000LL, delta);
2315 hrtick_start(rq, delta);
2320 * called from enqueue/dequeue and updates the hrtick when the
2321 * current task is from our class and nr_running is low enough
2324 static void hrtick_update(struct rq *rq)
2326 struct task_struct *curr = rq->curr;
2328 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
2331 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
2332 hrtick_start_fair(rq, curr);
2334 #else /* !CONFIG_SCHED_HRTICK */
2336 hrtick_start_fair(struct rq *rq, struct task_struct *p)
2340 static inline void hrtick_update(struct rq *rq)
2346 * The enqueue_task method is called before nr_running is
2347 * increased. Here we update the fair scheduling stats and
2348 * then put the task into the rbtree:
2351 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2353 struct cfs_rq *cfs_rq;
2354 struct sched_entity *se = &p->se;
2356 for_each_sched_entity(se) {
2359 cfs_rq = cfs_rq_of(se);
2360 enqueue_entity(cfs_rq, se, flags);
2363 * end evaluation on encountering a throttled cfs_rq
2365 * note: in the case of encountering a throttled cfs_rq we will
2366 * post the final h_nr_running increment below.
2368 if (cfs_rq_throttled(cfs_rq))
2370 cfs_rq->h_nr_running++;
2372 flags = ENQUEUE_WAKEUP;
2375 for_each_sched_entity(se) {
2376 cfs_rq = cfs_rq_of(se);
2377 cfs_rq->h_nr_running++;
2379 if (cfs_rq_throttled(cfs_rq))
2382 update_cfs_load(cfs_rq, 0);
2383 update_cfs_shares(cfs_rq);
2391 static void set_next_buddy(struct sched_entity *se);
2394 * The dequeue_task method is called before nr_running is
2395 * decreased. We remove the task from the rbtree and
2396 * update the fair scheduling stats:
2398 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2400 struct cfs_rq *cfs_rq;
2401 struct sched_entity *se = &p->se;
2402 int task_sleep = flags & DEQUEUE_SLEEP;
2404 for_each_sched_entity(se) {
2405 cfs_rq = cfs_rq_of(se);
2406 dequeue_entity(cfs_rq, se, flags);
2409 * end evaluation on encountering a throttled cfs_rq
2411 * note: in the case of encountering a throttled cfs_rq we will
2412 * post the final h_nr_running decrement below.
2414 if (cfs_rq_throttled(cfs_rq))
2416 cfs_rq->h_nr_running--;
2418 /* Don't dequeue parent if it has other entities besides us */
2419 if (cfs_rq->load.weight) {
2421 * Bias pick_next to pick a task from this cfs_rq, as
2422 * p is sleeping when it is within its sched_slice.
2424 if (task_sleep && parent_entity(se))
2425 set_next_buddy(parent_entity(se));
2427 /* avoid re-evaluating load for this entity */
2428 se = parent_entity(se);
2431 flags |= DEQUEUE_SLEEP;
2434 for_each_sched_entity(se) {
2435 cfs_rq = cfs_rq_of(se);
2436 cfs_rq->h_nr_running--;
2438 if (cfs_rq_throttled(cfs_rq))
2441 update_cfs_load(cfs_rq, 0);
2442 update_cfs_shares(cfs_rq);
2451 /* Used instead of source_load when we know the type == 0 */
2452 static unsigned long weighted_cpuload(const int cpu)
2454 return cpu_rq(cpu)->load.weight;
2458 * Return a low guess at the load of a migration-source cpu weighted
2459 * according to the scheduling class and "nice" value.
2461 * We want to under-estimate the load of migration sources, to
2462 * balance conservatively.
2464 static unsigned long source_load(int cpu, int type)
2466 struct rq *rq = cpu_rq(cpu);
2467 unsigned long total = weighted_cpuload(cpu);
2469 if (type == 0 || !sched_feat(LB_BIAS))
2472 return min(rq->cpu_load[type-1], total);
2476 * Return a high guess at the load of a migration-target cpu weighted
2477 * according to the scheduling class and "nice" value.
2479 static unsigned long target_load(int cpu, int type)
2481 struct rq *rq = cpu_rq(cpu);
2482 unsigned long total = weighted_cpuload(cpu);
2484 if (type == 0 || !sched_feat(LB_BIAS))
2487 return max(rq->cpu_load[type-1], total);
2490 static unsigned long power_of(int cpu)
2492 return cpu_rq(cpu)->cpu_power;
2495 static unsigned long cpu_avg_load_per_task(int cpu)
2497 struct rq *rq = cpu_rq(cpu);
2498 unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
2501 return rq->load.weight / nr_running;
2507 static void task_waking_fair(struct task_struct *p)
2509 struct sched_entity *se = &p->se;
2510 struct cfs_rq *cfs_rq = cfs_rq_of(se);
2513 #ifndef CONFIG_64BIT
2514 u64 min_vruntime_copy;
2517 min_vruntime_copy = cfs_rq->min_vruntime_copy;
2519 min_vruntime = cfs_rq->min_vruntime;
2520 } while (min_vruntime != min_vruntime_copy);
2522 min_vruntime = cfs_rq->min_vruntime;
2525 se->vruntime -= min_vruntime;
2528 #ifdef CONFIG_FAIR_GROUP_SCHED
2530 * effective_load() calculates the load change as seen from the root_task_group
2532 * Adding load to a group doesn't make a group heavier, but can cause movement
2533 * of group shares between cpus. Assuming the shares were perfectly aligned one
2534 * can calculate the shift in shares.
2536 * Calculate the effective load difference if @wl is added (subtracted) to @tg
2537 * on this @cpu and results in a total addition (subtraction) of @wg to the
2538 * total group weight.
2540 * Given a runqueue weight distribution (rw_i) we can compute a shares
2541 * distribution (s_i) using:
2543 * s_i = rw_i / \Sum rw_j (1)
2545 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
2546 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
2547 * shares distribution (s_i):
2549 * rw_i = { 2, 4, 1, 0 }
2550 * s_i = { 2/7, 4/7, 1/7, 0 }
2552 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
2553 * task used to run on and the CPU the waker is running on), we need to
2554 * compute the effect of waking a task on either CPU and, in case of a sync
2555 * wakeup, compute the effect of the current task going to sleep.
2557 * So for a change of @wl to the local @cpu with an overall group weight change
2558 * of @wl we can compute the new shares distribution (s'_i) using:
2560 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
2562 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
2563 * differences in waking a task to CPU 0. The additional task changes the
2564 * weight and shares distributions like:
2566 * rw'_i = { 3, 4, 1, 0 }
2567 * s'_i = { 3/8, 4/8, 1/8, 0 }
2569 * We can then compute the difference in effective weight by using:
2571 * dw_i = S * (s'_i - s_i) (3)
2573 * Where 'S' is the group weight as seen by its parent.
2575 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
2576 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
2577 * 4/7) times the weight of the group.
2579 static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
2581 struct sched_entity *se = tg->se[cpu];
2583 if (!tg->parent) /* the trivial, non-cgroup case */
2586 for_each_sched_entity(se) {
2592 * W = @wg + \Sum rw_j
2594 W = wg + calc_tg_weight(tg, se->my_q);
2599 w = se->my_q->load.weight + wl;
2602 * wl = S * s'_i; see (2)
2605 wl = (w * tg->shares) / W;
2610 * Per the above, wl is the new se->load.weight value; since
2611 * those are clipped to [MIN_SHARES, ...) do so now. See
2612 * calc_cfs_shares().
2614 if (wl < MIN_SHARES)
2618 * wl = dw_i = S * (s'_i - s_i); see (3)
2620 wl -= se->load.weight;
2623 * Recursively apply this logic to all parent groups to compute
2624 * the final effective load change on the root group. Since
2625 * only the @tg group gets extra weight, all parent groups can
2626 * only redistribute existing shares. @wl is the shift in shares
2627 * resulting from this level per the above.
2636 static inline unsigned long effective_load(struct task_group *tg, int cpu,
2637 unsigned long wl, unsigned long wg)
2644 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
2646 s64 this_load, load;
2647 int idx, this_cpu, prev_cpu;
2648 unsigned long tl_per_task;
2649 struct task_group *tg;
2650 unsigned long weight;
2654 this_cpu = smp_processor_id();
2655 prev_cpu = task_cpu(p);
2656 load = source_load(prev_cpu, idx);
2657 this_load = target_load(this_cpu, idx);
2660 * If sync wakeup then subtract the (maximum possible)
2661 * effect of the currently running task from the load
2662 * of the current CPU:
2665 tg = task_group(current);
2666 weight = current->se.load.weight;
2668 this_load += effective_load(tg, this_cpu, -weight, -weight);
2669 load += effective_load(tg, prev_cpu, 0, -weight);
2673 weight = p->se.load.weight;
2676 * In low-load situations, where prev_cpu is idle and this_cpu is idle
2677 * due to the sync cause above having dropped this_load to 0, we'll
2678 * always have an imbalance, but there's really nothing you can do
2679 * about that, so that's good too.
2681 * Otherwise check if either cpus are near enough in load to allow this
2682 * task to be woken on this_cpu.
2684 if (this_load > 0) {
2685 s64 this_eff_load, prev_eff_load;
2687 this_eff_load = 100;
2688 this_eff_load *= power_of(prev_cpu);
2689 this_eff_load *= this_load +
2690 effective_load(tg, this_cpu, weight, weight);
2692 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
2693 prev_eff_load *= power_of(this_cpu);
2694 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
2696 balanced = this_eff_load <= prev_eff_load;
2701 * If the currently running task will sleep within
2702 * a reasonable amount of time then attract this newly
2705 if (sync && balanced)
2708 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
2709 tl_per_task = cpu_avg_load_per_task(this_cpu);
2712 (this_load <= load &&
2713 this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
2715 * This domain has SD_WAKE_AFFINE and
2716 * p is cache cold in this domain, and
2717 * there is no bad imbalance.
2719 schedstat_inc(sd, ttwu_move_affine);
2720 schedstat_inc(p, se.statistics.nr_wakeups_affine);
2728 * find_idlest_group finds and returns the least busy CPU group within the
2731 static struct sched_group *
2732 find_idlest_group(struct sched_domain *sd, struct task_struct *p,
2733 int this_cpu, int load_idx)
2735 struct sched_group *idlest = NULL, *group = sd->groups;
2736 unsigned long min_load = ULONG_MAX, this_load = 0;
2737 int imbalance = 100 + (sd->imbalance_pct-100)/2;
2740 unsigned long load, avg_load;
2744 /* Skip over this group if it has no CPUs allowed */
2745 if (!cpumask_intersects(sched_group_cpus(group),
2746 tsk_cpus_allowed(p)))
2749 local_group = cpumask_test_cpu(this_cpu,
2750 sched_group_cpus(group));
2752 /* Tally up the load of all CPUs in the group */
2755 for_each_cpu(i, sched_group_cpus(group)) {
2756 /* Bias balancing toward cpus of our domain */
2758 load = source_load(i, load_idx);
2760 load = target_load(i, load_idx);
2765 /* Adjust by relative CPU power of the group */
2766 avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
2769 this_load = avg_load;
2770 } else if (avg_load < min_load) {
2771 min_load = avg_load;
2774 } while (group = group->next, group != sd->groups);
2776 if (!idlest || 100*this_load < imbalance*min_load)
2782 * find_idlest_cpu - find the idlest cpu among the cpus in group.
2785 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
2787 unsigned long load, min_load = ULONG_MAX;
2791 /* Traverse only the allowed CPUs */
2792 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
2793 load = weighted_cpuload(i);
2795 if (load < min_load || (load == min_load && i == this_cpu)) {
2805 * Try and locate an idle CPU in the sched_domain.
2807 static int select_idle_sibling(struct task_struct *p, int target)
2809 int cpu = smp_processor_id();
2810 int prev_cpu = task_cpu(p);
2811 struct sched_domain *sd;
2812 struct sched_group *sg;
2816 * If the task is going to be woken-up on this cpu and if it is
2817 * already idle, then it is the right target.
2819 if (target == cpu && idle_cpu(cpu))
2823 * If the task is going to be woken-up on the cpu where it previously
2824 * ran and if it is currently idle, then it the right target.
2826 if (target == prev_cpu && idle_cpu(prev_cpu))
2830 * Otherwise, iterate the domains and find an elegible idle cpu.
2832 sd = rcu_dereference(per_cpu(sd_llc, target));
2833 for_each_lower_domain(sd) {
2836 if (!cpumask_intersects(sched_group_cpus(sg),
2837 tsk_cpus_allowed(p)))
2840 for_each_cpu(i, sched_group_cpus(sg)) {
2845 target = cpumask_first_and(sched_group_cpus(sg),
2846 tsk_cpus_allowed(p));
2850 } while (sg != sd->groups);
2857 * sched_balance_self: balance the current task (running on cpu) in domains
2858 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
2861 * Balance, ie. select the least loaded group.
2863 * Returns the target CPU number, or the same CPU if no balancing is needed.
2865 * preempt must be disabled.
2868 select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
2870 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
2871 int cpu = smp_processor_id();
2872 int prev_cpu = task_cpu(p);
2874 int want_affine = 0;
2875 int sync = wake_flags & WF_SYNC;
2877 if (p->nr_cpus_allowed == 1)
2880 if (sd_flag & SD_BALANCE_WAKE) {
2881 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
2887 for_each_domain(cpu, tmp) {
2888 if (!(tmp->flags & SD_LOAD_BALANCE))
2892 * If both cpu and prev_cpu are part of this domain,
2893 * cpu is a valid SD_WAKE_AFFINE target.
2895 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
2896 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
2901 if (tmp->flags & sd_flag)
2906 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
2909 new_cpu = select_idle_sibling(p, prev_cpu);
2914 int load_idx = sd->forkexec_idx;
2915 struct sched_group *group;
2918 if (!(sd->flags & sd_flag)) {
2923 if (sd_flag & SD_BALANCE_WAKE)
2924 load_idx = sd->wake_idx;
2926 group = find_idlest_group(sd, p, cpu, load_idx);
2932 new_cpu = find_idlest_cpu(group, p, cpu);
2933 if (new_cpu == -1 || new_cpu == cpu) {
2934 /* Now try balancing at a lower domain level of cpu */
2939 /* Now try balancing at a lower domain level of new_cpu */
2941 weight = sd->span_weight;
2943 for_each_domain(cpu, tmp) {
2944 if (weight <= tmp->span_weight)
2946 if (tmp->flags & sd_flag)
2949 /* while loop will break here if sd == NULL */
2956 #endif /* CONFIG_SMP */
2958 static unsigned long
2959 wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
2961 unsigned long gran = sysctl_sched_wakeup_granularity;
2964 * Since its curr running now, convert the gran from real-time
2965 * to virtual-time in his units.
2967 * By using 'se' instead of 'curr' we penalize light tasks, so
2968 * they get preempted easier. That is, if 'se' < 'curr' then
2969 * the resulting gran will be larger, therefore penalizing the
2970 * lighter, if otoh 'se' > 'curr' then the resulting gran will
2971 * be smaller, again penalizing the lighter task.
2973 * This is especially important for buddies when the leftmost
2974 * task is higher priority than the buddy.
2976 return calc_delta_fair(gran, se);
2980 * Should 'se' preempt 'curr'.
2994 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
2996 s64 gran, vdiff = curr->vruntime - se->vruntime;
3001 gran = wakeup_gran(curr, se);
3008 static void set_last_buddy(struct sched_entity *se)
3010 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
3013 for_each_sched_entity(se)
3014 cfs_rq_of(se)->last = se;
3017 static void set_next_buddy(struct sched_entity *se)
3019 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
3022 for_each_sched_entity(se)
3023 cfs_rq_of(se)->next = se;
3026 static void set_skip_buddy(struct sched_entity *se)
3028 for_each_sched_entity(se)
3029 cfs_rq_of(se)->skip = se;
3033 * Preempt the current task with a newly woken task if needed:
3035 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3037 struct task_struct *curr = rq->curr;
3038 struct sched_entity *se = &curr->se, *pse = &p->se;
3039 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3040 int scale = cfs_rq->nr_running >= sched_nr_latency;
3041 int next_buddy_marked = 0;
3043 if (unlikely(se == pse))
3047 * This is possible from callers such as move_task(), in which we
3048 * unconditionally check_prempt_curr() after an enqueue (which may have
3049 * lead to a throttle). This both saves work and prevents false
3050 * next-buddy nomination below.
3052 if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
3055 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
3056 set_next_buddy(pse);
3057 next_buddy_marked = 1;
3061 * We can come here with TIF_NEED_RESCHED already set from new task
3064 * Note: this also catches the edge-case of curr being in a throttled
3065 * group (e.g. via set_curr_task), since update_curr() (in the
3066 * enqueue of curr) will have resulted in resched being set. This
3067 * prevents us from potentially nominating it as a false LAST_BUDDY
3070 if (test_tsk_need_resched(curr))
3073 /* Idle tasks are by definition preempted by non-idle tasks. */
3074 if (unlikely(curr->policy == SCHED_IDLE) &&
3075 likely(p->policy != SCHED_IDLE))
3079 * Batch and idle tasks do not preempt non-idle tasks (their preemption
3080 * is driven by the tick):
3082 if (unlikely(p->policy != SCHED_NORMAL))
3085 find_matching_se(&se, &pse);
3086 update_curr(cfs_rq_of(se));
3088 if (wakeup_preempt_entity(se, pse) == 1) {
3090 * Bias pick_next to pick the sched entity that is
3091 * triggering this preemption.
3093 if (!next_buddy_marked)
3094 set_next_buddy(pse);
3103 * Only set the backward buddy when the current task is still
3104 * on the rq. This can happen when a wakeup gets interleaved
3105 * with schedule on the ->pre_schedule() or idle_balance()
3106 * point, either of which can * drop the rq lock.
3108 * Also, during early boot the idle thread is in the fair class,
3109 * for obvious reasons its a bad idea to schedule back to it.
3111 if (unlikely(!se->on_rq || curr == rq->idle))
3114 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
3118 static struct task_struct *pick_next_task_fair(struct rq *rq)
3120 struct task_struct *p;
3121 struct cfs_rq *cfs_rq = &rq->cfs;
3122 struct sched_entity *se;
3124 if (!cfs_rq->nr_running)
3128 se = pick_next_entity(cfs_rq);
3129 set_next_entity(cfs_rq, se);
3130 cfs_rq = group_cfs_rq(se);
3134 if (hrtick_enabled(rq))
3135 hrtick_start_fair(rq, p);
3141 * Account for a descheduled task:
3143 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3145 struct sched_entity *se = &prev->se;
3146 struct cfs_rq *cfs_rq;
3148 for_each_sched_entity(se) {
3149 cfs_rq = cfs_rq_of(se);
3150 put_prev_entity(cfs_rq, se);
3155 * sched_yield() is very simple
3157 * The magic of dealing with the ->skip buddy is in pick_next_entity.
3159 static void yield_task_fair(struct rq *rq)
3161 struct task_struct *curr = rq->curr;
3162 struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3163 struct sched_entity *se = &curr->se;
3166 * Are we the only task in the tree?
3168 if (unlikely(rq->nr_running == 1))
3171 clear_buddies(cfs_rq, se);
3173 if (curr->policy != SCHED_BATCH) {
3174 update_rq_clock(rq);
3176 * Update run-time statistics of the 'current'.
3178 update_curr(cfs_rq);
3180 * Tell update_rq_clock() that we've just updated,
3181 * so we don't do microscopic update in schedule()
3182 * and double the fastpath cost.
3184 rq->skip_clock_update = 1;
3190 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
3192 struct sched_entity *se = &p->se;
3194 /* throttled hierarchies are not runnable */
3195 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3198 /* Tell the scheduler that we'd really like pse to run next. */
3201 yield_task_fair(rq);
3207 /**************************************************
3208 * Fair scheduling class load-balancing methods:
3211 static unsigned long __read_mostly max_load_balance_interval = HZ/10;
3213 #define LBF_ALL_PINNED 0x01
3214 #define LBF_NEED_BREAK 0x02
3215 #define LBF_SOME_PINNED 0x04
3218 struct sched_domain *sd;
3226 struct cpumask *dst_grpmask;
3228 enum cpu_idle_type idle;
3230 /* The set of CPUs under consideration for load-balancing */
3231 struct cpumask *cpus;
3236 unsigned int loop_break;
3237 unsigned int loop_max;
3241 * move_task - move a task from one runqueue to another runqueue.
3242 * Both runqueues must be locked.
3244 static void move_task(struct task_struct *p, struct lb_env *env)
3246 deactivate_task(env->src_rq, p, 0);
3247 set_task_cpu(p, env->dst_cpu);
3248 activate_task(env->dst_rq, p, 0);
3249 check_preempt_curr(env->dst_rq, p, 0);
3253 * Is this task likely cache-hot:
3256 task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
3260 if (p->sched_class != &fair_sched_class)
3263 if (unlikely(p->policy == SCHED_IDLE))
3267 * Buddy candidates are cache hot:
3269 if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
3270 (&p->se == cfs_rq_of(&p->se)->next ||
3271 &p->se == cfs_rq_of(&p->se)->last))
3274 if (sysctl_sched_migration_cost == -1)
3276 if (sysctl_sched_migration_cost == 0)
3279 delta = now - p->se.exec_start;
3281 return delta < (s64)sysctl_sched_migration_cost;
3285 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
3288 int can_migrate_task(struct task_struct *p, struct lb_env *env)
3290 int tsk_cache_hot = 0;
3292 * We do not migrate tasks that are:
3293 * 1) running (obviously), or
3294 * 2) cannot be migrated to this CPU due to cpus_allowed, or
3295 * 3) are cache-hot on their current CPU.
3297 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
3300 schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
3303 * Remember if this task can be migrated to any other cpu in
3304 * our sched_group. We may want to revisit it if we couldn't
3305 * meet load balance goals by pulling other tasks on src_cpu.
3307 * Also avoid computing new_dst_cpu if we have already computed
3308 * one in current iteration.
3310 if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
3313 new_dst_cpu = cpumask_first_and(env->dst_grpmask,
3314 tsk_cpus_allowed(p));
3315 if (new_dst_cpu < nr_cpu_ids) {
3316 env->flags |= LBF_SOME_PINNED;
3317 env->new_dst_cpu = new_dst_cpu;
3322 /* Record that we found atleast one task that could run on dst_cpu */
3323 env->flags &= ~LBF_ALL_PINNED;
3325 if (task_running(env->src_rq, p)) {
3326 schedstat_inc(p, se.statistics.nr_failed_migrations_running);
3331 * Aggressive migration if:
3332 * 1) task is cache cold, or
3333 * 2) too many balance attempts have failed.
3336 tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
3337 if (!tsk_cache_hot ||
3338 env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
3339 #ifdef CONFIG_SCHEDSTATS
3340 if (tsk_cache_hot) {
3341 schedstat_inc(env->sd, lb_hot_gained[env->idle]);
3342 schedstat_inc(p, se.statistics.nr_forced_migrations);
3348 if (tsk_cache_hot) {
3349 schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
3356 * move_one_task tries to move exactly one task from busiest to this_rq, as
3357 * part of active balancing operations within "domain".
3358 * Returns 1 if successful and 0 otherwise.
3360 * Called with both runqueues locked.
3362 static int move_one_task(struct lb_env *env)
3364 struct task_struct *p, *n;
3366 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
3367 if (throttled_lb_pair(task_group(p), env->src_rq->cpu, env->dst_cpu))
3370 if (!can_migrate_task(p, env))
3375 * Right now, this is only the second place move_task()
3376 * is called, so we can safely collect move_task()
3377 * stats here rather than inside move_task().
3379 schedstat_inc(env->sd, lb_gained[env->idle]);
3385 static unsigned long task_h_load(struct task_struct *p);
3387 static const unsigned int sched_nr_migrate_break = 32;
3390 * move_tasks tries to move up to imbalance weighted load from busiest to
3391 * this_rq, as part of a balancing operation within domain "sd".
3392 * Returns 1 if successful and 0 otherwise.
3394 * Called with both runqueues locked.
3396 static int move_tasks(struct lb_env *env)
3398 struct list_head *tasks = &env->src_rq->cfs_tasks;
3399 struct task_struct *p;
3403 if (env->imbalance <= 0)
3406 while (!list_empty(tasks)) {
3407 p = list_first_entry(tasks, struct task_struct, se.group_node);
3410 /* We've more or less seen every task there is, call it quits */
3411 if (env->loop > env->loop_max)
3414 /* take a breather every nr_migrate tasks */
3415 if (env->loop > env->loop_break) {
3416 env->loop_break += sched_nr_migrate_break;
3417 env->flags |= LBF_NEED_BREAK;
3421 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
3424 load = task_h_load(p);
3426 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
3429 if ((load / 2) > env->imbalance)
3432 if (!can_migrate_task(p, env))
3437 env->imbalance -= load;
3439 #ifdef CONFIG_PREEMPT
3441 * NEWIDLE balancing is a source of latency, so preemptible
3442 * kernels will stop after the first task is pulled to minimize
3443 * the critical section.
3445 if (env->idle == CPU_NEWLY_IDLE)
3450 * We only want to steal up to the prescribed amount of
3453 if (env->imbalance <= 0)
3458 list_move_tail(&p->se.group_node, tasks);
3462 * Right now, this is one of only two places move_task() is called,
3463 * so we can safely collect move_task() stats here rather than
3464 * inside move_task().
3466 schedstat_add(env->sd, lb_gained[env->idle], pulled);
3471 #ifdef CONFIG_FAIR_GROUP_SCHED
3473 * update tg->load_weight by folding this cpu's load_avg
3475 static int update_shares_cpu(struct task_group *tg, int cpu)
3477 struct cfs_rq *cfs_rq;
3478 unsigned long flags;
3485 cfs_rq = tg->cfs_rq[cpu];
3487 raw_spin_lock_irqsave(&rq->lock, flags);
3489 update_rq_clock(rq);
3490 update_cfs_load(cfs_rq, 1);
3493 * We need to update shares after updating tg->load_weight in
3494 * order to adjust the weight of groups with long running tasks.
3496 update_cfs_shares(cfs_rq);
3498 raw_spin_unlock_irqrestore(&rq->lock, flags);
3503 static void update_shares(int cpu)
3505 struct cfs_rq *cfs_rq;
3506 struct rq *rq = cpu_rq(cpu);
3510 * Iterates the task_group tree in a bottom up fashion, see
3511 * list_add_leaf_cfs_rq() for details.
3513 for_each_leaf_cfs_rq(rq, cfs_rq) {
3514 /* throttled entities do not contribute to load */
3515 if (throttled_hierarchy(cfs_rq))
3518 update_shares_cpu(cfs_rq->tg, cpu);
3524 * Compute the cpu's hierarchical load factor for each task group.
3525 * This needs to be done in a top-down fashion because the load of a child
3526 * group is a fraction of its parents load.
3528 static int tg_load_down(struct task_group *tg, void *data)
3531 long cpu = (long)data;
3534 load = cpu_rq(cpu)->load.weight;
3536 load = tg->parent->cfs_rq[cpu]->h_load;
3537 load *= tg->se[cpu]->load.weight;
3538 load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
3541 tg->cfs_rq[cpu]->h_load = load;
3546 static void update_h_load(long cpu)
3548 struct rq *rq = cpu_rq(cpu);
3549 unsigned long now = jiffies;
3551 if (rq->h_load_throttle == now)
3554 rq->h_load_throttle = now;
3557 walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
3561 static unsigned long task_h_load(struct task_struct *p)
3563 struct cfs_rq *cfs_rq = task_cfs_rq(p);
3566 load = p->se.load.weight;
3567 load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1);
3572 static inline void update_shares(int cpu)
3576 static inline void update_h_load(long cpu)
3580 static unsigned long task_h_load(struct task_struct *p)
3582 return p->se.load.weight;
3586 /********** Helpers for find_busiest_group ************************/
3588 * sd_lb_stats - Structure to store the statistics of a sched_domain
3589 * during load balancing.
3591 struct sd_lb_stats {
3592 struct sched_group *busiest; /* Busiest group in this sd */
3593 struct sched_group *this; /* Local group in this sd */
3594 unsigned long total_load; /* Total load of all groups in sd */
3595 unsigned long total_pwr; /* Total power of all groups in sd */
3596 unsigned long avg_load; /* Average load across all groups in sd */
3598 /** Statistics of this group */
3599 unsigned long this_load;
3600 unsigned long this_load_per_task;
3601 unsigned long this_nr_running;
3602 unsigned long this_has_capacity;
3603 unsigned int this_idle_cpus;
3605 /* Statistics of the busiest group */
3606 unsigned int busiest_idle_cpus;
3607 unsigned long max_load;
3608 unsigned long busiest_load_per_task;
3609 unsigned long busiest_nr_running;
3610 unsigned long busiest_group_capacity;
3611 unsigned long busiest_has_capacity;
3612 unsigned int busiest_group_weight;
3614 int group_imb; /* Is there imbalance in this sd */
3618 * sg_lb_stats - stats of a sched_group required for load_balancing
3620 struct sg_lb_stats {
3621 unsigned long avg_load; /*Avg load across the CPUs of the group */
3622 unsigned long group_load; /* Total load over the CPUs of the group */
3623 unsigned long sum_nr_running; /* Nr tasks running in the group */
3624 unsigned long sum_weighted_load; /* Weighted load of group's tasks */
3625 unsigned long group_capacity;
3626 unsigned long idle_cpus;
3627 unsigned long group_weight;
3628 int group_imb; /* Is there an imbalance in the group ? */
3629 int group_has_capacity; /* Is there extra capacity in the group? */
3633 * get_sd_load_idx - Obtain the load index for a given sched domain.
3634 * @sd: The sched_domain whose load_idx is to be obtained.
3635 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
3637 static inline int get_sd_load_idx(struct sched_domain *sd,
3638 enum cpu_idle_type idle)
3644 load_idx = sd->busy_idx;
3647 case CPU_NEWLY_IDLE:
3648 load_idx = sd->newidle_idx;
3651 load_idx = sd->idle_idx;
3658 unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
3660 return SCHED_POWER_SCALE;
3663 unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
3665 return default_scale_freq_power(sd, cpu);
3668 unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
3670 unsigned long weight = sd->span_weight;
3671 unsigned long smt_gain = sd->smt_gain;
3678 unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
3680 return default_scale_smt_power(sd, cpu);
3683 unsigned long scale_rt_power(int cpu)
3685 struct rq *rq = cpu_rq(cpu);
3686 u64 total, available, age_stamp, avg;
3689 * Since we're reading these variables without serialization make sure
3690 * we read them once before doing sanity checks on them.
3692 age_stamp = ACCESS_ONCE(rq->age_stamp);
3693 avg = ACCESS_ONCE(rq->rt_avg);
3695 total = sched_avg_period() + (rq->clock - age_stamp);
3697 if (unlikely(total < avg)) {
3698 /* Ensures that power won't end up being negative */
3701 available = total - avg;
3704 if (unlikely((s64)total < SCHED_POWER_SCALE))
3705 total = SCHED_POWER_SCALE;
3707 total >>= SCHED_POWER_SHIFT;
3709 return div_u64(available, total);
3712 static void update_cpu_power(struct sched_domain *sd, int cpu)
3714 unsigned long weight = sd->span_weight;
3715 unsigned long power = SCHED_POWER_SCALE;
3716 struct sched_group *sdg = sd->groups;
3718 if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
3719 if (sched_feat(ARCH_POWER))
3720 power *= arch_scale_smt_power(sd, cpu);
3722 power *= default_scale_smt_power(sd, cpu);
3724 power >>= SCHED_POWER_SHIFT;
3727 sdg->sgp->power_orig = power;
3729 if (sched_feat(ARCH_POWER))
3730 power *= arch_scale_freq_power(sd, cpu);
3732 power *= default_scale_freq_power(sd, cpu);
3734 power >>= SCHED_POWER_SHIFT;
3736 power *= scale_rt_power(cpu);
3737 power >>= SCHED_POWER_SHIFT;
3742 cpu_rq(cpu)->cpu_power = power;
3743 sdg->sgp->power = power;
3746 void update_group_power(struct sched_domain *sd, int cpu)
3748 struct sched_domain *child = sd->child;
3749 struct sched_group *group, *sdg = sd->groups;
3750 unsigned long power;
3751 unsigned long interval;
3753 interval = msecs_to_jiffies(sd->balance_interval);
3754 interval = clamp(interval, 1UL, max_load_balance_interval);
3755 sdg->sgp->next_update = jiffies + interval;
3758 update_cpu_power(sd, cpu);
3764 if (child->flags & SD_OVERLAP) {
3766 * SD_OVERLAP domains cannot assume that child groups
3767 * span the current group.
3770 for_each_cpu(cpu, sched_group_cpus(sdg))
3771 power += power_of(cpu);
3774 * !SD_OVERLAP domains can assume that child groups
3775 * span the current group.
3778 group = child->groups;
3780 power += group->sgp->power;
3781 group = group->next;
3782 } while (group != child->groups);
3785 sdg->sgp->power_orig = sdg->sgp->power = power;
3789 * Try and fix up capacity for tiny siblings, this is needed when
3790 * things like SD_ASYM_PACKING need f_b_g to select another sibling
3791 * which on its own isn't powerful enough.
3793 * See update_sd_pick_busiest() and check_asym_packing().
3796 fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
3799 * Only siblings can have significantly less than SCHED_POWER_SCALE
3801 if (!(sd->flags & SD_SHARE_CPUPOWER))
3805 * If ~90% of the cpu_power is still there, we're good.
3807 if (group->sgp->power * 32 > group->sgp->power_orig * 29)
3814 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
3815 * @env: The load balancing environment.
3816 * @group: sched_group whose statistics are to be updated.
3817 * @load_idx: Load index of sched_domain of this_cpu for load calc.
3818 * @local_group: Does group contain this_cpu.
3819 * @balance: Should we balance.
3820 * @sgs: variable to hold the statistics for this group.
3822 static inline void update_sg_lb_stats(struct lb_env *env,
3823 struct sched_group *group, int load_idx,
3824 int local_group, int *balance, struct sg_lb_stats *sgs)
3826 unsigned long nr_running, max_nr_running, min_nr_running;
3827 unsigned long load, max_cpu_load, min_cpu_load;
3828 unsigned int balance_cpu = -1, first_idle_cpu = 0;
3829 unsigned long avg_load_per_task = 0;
3833 balance_cpu = group_balance_cpu(group);
3835 /* Tally up the load of all CPUs in the group */
3837 min_cpu_load = ~0UL;
3839 min_nr_running = ~0UL;
3841 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
3842 struct rq *rq = cpu_rq(i);
3844 nr_running = rq->nr_running;
3846 /* Bias balancing toward cpus of our domain */
3848 if (idle_cpu(i) && !first_idle_cpu &&
3849 cpumask_test_cpu(i, sched_group_mask(group))) {
3854 load = target_load(i, load_idx);
3856 load = source_load(i, load_idx);
3857 if (load > max_cpu_load)
3858 max_cpu_load = load;
3859 if (min_cpu_load > load)
3860 min_cpu_load = load;
3862 if (nr_running > max_nr_running)
3863 max_nr_running = nr_running;
3864 if (min_nr_running > nr_running)
3865 min_nr_running = nr_running;
3868 sgs->group_load += load;
3869 sgs->sum_nr_running += nr_running;
3870 sgs->sum_weighted_load += weighted_cpuload(i);
3876 * First idle cpu or the first cpu(busiest) in this sched group
3877 * is eligible for doing load balancing at this and above
3878 * domains. In the newly idle case, we will allow all the cpu's
3879 * to do the newly idle load balance.
3882 if (env->idle != CPU_NEWLY_IDLE) {
3883 if (balance_cpu != env->dst_cpu) {
3887 update_group_power(env->sd, env->dst_cpu);
3888 } else if (time_after_eq(jiffies, group->sgp->next_update))
3889 update_group_power(env->sd, env->dst_cpu);
3892 /* Adjust by relative CPU power of the group */
3893 sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
3896 * Consider the group unbalanced when the imbalance is larger
3897 * than the average weight of a task.
3899 * APZ: with cgroup the avg task weight can vary wildly and
3900 * might not be a suitable number - should we keep a
3901 * normalized nr_running number somewhere that negates
3904 if (sgs->sum_nr_running)
3905 avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
3907 if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
3908 (max_nr_running - min_nr_running) > 1)
3911 sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
3913 if (!sgs->group_capacity)
3914 sgs->group_capacity = fix_small_capacity(env->sd, group);
3915 sgs->group_weight = group->group_weight;
3917 if (sgs->group_capacity > sgs->sum_nr_running)
3918 sgs->group_has_capacity = 1;
3922 * update_sd_pick_busiest - return 1 on busiest group
3923 * @env: The load balancing environment.
3924 * @sds: sched_domain statistics
3925 * @sg: sched_group candidate to be checked for being the busiest
3926 * @sgs: sched_group statistics
3928 * Determine if @sg is a busier group than the previously selected
3931 static bool update_sd_pick_busiest(struct lb_env *env,
3932 struct sd_lb_stats *sds,
3933 struct sched_group *sg,
3934 struct sg_lb_stats *sgs)
3936 if (sgs->avg_load <= sds->max_load)
3939 if (sgs->sum_nr_running > sgs->group_capacity)
3946 * ASYM_PACKING needs to move all the work to the lowest
3947 * numbered CPUs in the group, therefore mark all groups
3948 * higher than ourself as busy.
3950 if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
3951 env->dst_cpu < group_first_cpu(sg)) {
3955 if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
3963 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
3964 * @env: The load balancing environment.
3965 * @balance: Should we balance.
3966 * @sds: variable to hold the statistics for this sched_domain.
3968 static inline void update_sd_lb_stats(struct lb_env *env,
3969 int *balance, struct sd_lb_stats *sds)
3971 struct sched_domain *child = env->sd->child;
3972 struct sched_group *sg = env->sd->groups;
3973 struct sg_lb_stats sgs;
3974 int load_idx, prefer_sibling = 0;
3976 if (child && child->flags & SD_PREFER_SIBLING)
3979 load_idx = get_sd_load_idx(env->sd, env->idle);
3984 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
3985 memset(&sgs, 0, sizeof(sgs));
3986 update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);
3988 if (local_group && !(*balance))
3991 sds->total_load += sgs.group_load;
3992 sds->total_pwr += sg->sgp->power;
3995 * In case the child domain prefers tasks go to siblings
3996 * first, lower the sg capacity to one so that we'll try
3997 * and move all the excess tasks away. We lower the capacity
3998 * of a group only if the local group has the capacity to fit
3999 * these excess tasks, i.e. nr_running < group_capacity. The
4000 * extra check prevents the case where you always pull from the
4001 * heaviest group when it is already under-utilized (possible
4002 * with a large weight task outweighs the tasks on the system).
4004 if (prefer_sibling && !local_group && sds->this_has_capacity)
4005 sgs.group_capacity = min(sgs.group_capacity, 1UL);
4008 sds->this_load = sgs.avg_load;
4010 sds->this_nr_running = sgs.sum_nr_running;
4011 sds->this_load_per_task = sgs.sum_weighted_load;
4012 sds->this_has_capacity = sgs.group_has_capacity;
4013 sds->this_idle_cpus = sgs.idle_cpus;
4014 } else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
4015 sds->max_load = sgs.avg_load;
4017 sds->busiest_nr_running = sgs.sum_nr_running;
4018 sds->busiest_idle_cpus = sgs.idle_cpus;
4019 sds->busiest_group_capacity = sgs.group_capacity;
4020 sds->busiest_load_per_task = sgs.sum_weighted_load;
4021 sds->busiest_has_capacity = sgs.group_has_capacity;
4022 sds->busiest_group_weight = sgs.group_weight;
4023 sds->group_imb = sgs.group_imb;
4027 } while (sg != env->sd->groups);
4031 * check_asym_packing - Check to see if the group is packed into the
4034 * This is primarily intended to used at the sibling level. Some
4035 * cores like POWER7 prefer to use lower numbered SMT threads. In the
4036 * case of POWER7, it can move to lower SMT modes only when higher
4037 * threads are idle. When in lower SMT modes, the threads will
4038 * perform better since they share less core resources. Hence when we
4039 * have idle threads, we want them to be the higher ones.
4041 * This packing function is run on idle threads. It checks to see if
4042 * the busiest CPU in this domain (core in the P7 case) has a higher
4043 * CPU number than the packing function is being run on. Here we are
4044 * assuming lower CPU number will be equivalent to lower a SMT thread
4047 * Returns 1 when packing is required and a task should be moved to
4048 * this CPU. The amount of the imbalance is returned in *imbalance.
4050 * @env: The load balancing environment.
4051 * @sds: Statistics of the sched_domain which is to be packed
4053 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4057 if (!(env->sd->flags & SD_ASYM_PACKING))
4063 busiest_cpu = group_first_cpu(sds->busiest);
4064 if (env->dst_cpu > busiest_cpu)
4067 env->imbalance = DIV_ROUND_CLOSEST(
4068 sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);
4074 * fix_small_imbalance - Calculate the minor imbalance that exists
4075 * amongst the groups of a sched_domain, during
4077 * @env: The load balancing environment.
4078 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
4081 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4083 unsigned long tmp, pwr_now = 0, pwr_move = 0;
4084 unsigned int imbn = 2;
4085 unsigned long scaled_busy_load_per_task;
4087 if (sds->this_nr_running) {
4088 sds->this_load_per_task /= sds->this_nr_running;
4089 if (sds->busiest_load_per_task >
4090 sds->this_load_per_task)
4093 sds->this_load_per_task =
4094 cpu_avg_load_per_task(env->dst_cpu);
4097 scaled_busy_load_per_task = sds->busiest_load_per_task
4098 * SCHED_POWER_SCALE;
4099 scaled_busy_load_per_task /= sds->busiest->sgp->power;
4101 if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
4102 (scaled_busy_load_per_task * imbn)) {
4103 env->imbalance = sds->busiest_load_per_task;
4108 * OK, we don't have enough imbalance to justify moving tasks,
4109 * however we may be able to increase total CPU power used by
4113 pwr_now += sds->busiest->sgp->power *
4114 min(sds->busiest_load_per_task, sds->max_load);
4115 pwr_now += sds->this->sgp->power *
4116 min(sds->this_load_per_task, sds->this_load);
4117 pwr_now /= SCHED_POWER_SCALE;
4119 /* Amount of load we'd subtract */
4120 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4121 sds->busiest->sgp->power;
4122 if (sds->max_load > tmp)
4123 pwr_move += sds->busiest->sgp->power *
4124 min(sds->busiest_load_per_task, sds->max_load - tmp);
4126 /* Amount of load we'd add */
4127 if (sds->max_load * sds->busiest->sgp->power <
4128 sds->busiest_load_per_task * SCHED_POWER_SCALE)
4129 tmp = (sds->max_load * sds->busiest->sgp->power) /
4130 sds->this->sgp->power;
4132 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4133 sds->this->sgp->power;
4134 pwr_move += sds->this->sgp->power *
4135 min(sds->this_load_per_task, sds->this_load + tmp);
4136 pwr_move /= SCHED_POWER_SCALE;
4138 /* Move if we gain throughput */
4139 if (pwr_move > pwr_now)
4140 env->imbalance = sds->busiest_load_per_task;
4144 * calculate_imbalance - Calculate the amount of imbalance present within the
4145 * groups of a given sched_domain during load balance.
4146 * @env: load balance environment
4147 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
4149 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4151 unsigned long max_pull, load_above_capacity = ~0UL;
4153 sds->busiest_load_per_task /= sds->busiest_nr_running;
4154 if (sds->group_imb) {
4155 sds->busiest_load_per_task =
4156 min(sds->busiest_load_per_task, sds->avg_load);
4160 * In the presence of smp nice balancing, certain scenarios can have
4161 * max load less than avg load(as we skip the groups at or below
4162 * its cpu_power, while calculating max_load..)
4164 if (sds->max_load < sds->avg_load) {
4166 return fix_small_imbalance(env, sds);
4169 if (!sds->group_imb) {
4171 * Don't want to pull so many tasks that a group would go idle.
4173 load_above_capacity = (sds->busiest_nr_running -
4174 sds->busiest_group_capacity);
4176 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
4178 load_above_capacity /= sds->busiest->sgp->power;
4182 * We're trying to get all the cpus to the average_load, so we don't
4183 * want to push ourselves above the average load, nor do we wish to
4184 * reduce the max loaded cpu below the average load. At the same time,
4185 * we also don't want to reduce the group load below the group capacity
4186 * (so that we can implement power-savings policies etc). Thus we look
4187 * for the minimum possible imbalance.
4188 * Be careful of negative numbers as they'll appear as very large values
4189 * with unsigned longs.
4191 max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
4193 /* How much load to actually move to equalise the imbalance */
4194 env->imbalance = min(max_pull * sds->busiest->sgp->power,
4195 (sds->avg_load - sds->this_load) * sds->this->sgp->power)
4196 / SCHED_POWER_SCALE;
4199 * if *imbalance is less than the average load per runnable task
4200 * there is no guarantee that any tasks will be moved so we'll have
4201 * a think about bumping its value to force at least one task to be
4204 if (env->imbalance < sds->busiest_load_per_task)
4205 return fix_small_imbalance(env, sds);
4209 /******* find_busiest_group() helpers end here *********************/
4212 * find_busiest_group - Returns the busiest group within the sched_domain
4213 * if there is an imbalance. If there isn't an imbalance, and
4214 * the user has opted for power-savings, it returns a group whose
4215 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
4216 * such a group exists.
4218 * Also calculates the amount of weighted load which should be moved
4219 * to restore balance.
4221 * @env: The load balancing environment.
4222 * @balance: Pointer to a variable indicating if this_cpu
4223 * is the appropriate cpu to perform load balancing at this_level.
4225 * Returns: - the busiest group if imbalance exists.
4226 * - If no imbalance and user has opted for power-savings balance,
4227 * return the least loaded group whose CPUs can be
4228 * put to idle by rebalancing its tasks onto our group.
4230 static struct sched_group *
4231 find_busiest_group(struct lb_env *env, int *balance)
4233 struct sd_lb_stats sds;
4235 memset(&sds, 0, sizeof(sds));
4238 * Compute the various statistics relavent for load balancing at
4241 update_sd_lb_stats(env, balance, &sds);
4244 * this_cpu is not the appropriate cpu to perform load balancing at
4250 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
4251 check_asym_packing(env, &sds))
4254 /* There is no busy sibling group to pull tasks from */
4255 if (!sds.busiest || sds.busiest_nr_running == 0)
4258 sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
4261 * If the busiest group is imbalanced the below checks don't
4262 * work because they assumes all things are equal, which typically
4263 * isn't true due to cpus_allowed constraints and the like.
4268 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
4269 if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
4270 !sds.busiest_has_capacity)
4274 * If the local group is more busy than the selected busiest group
4275 * don't try and pull any tasks.
4277 if (sds.this_load >= sds.max_load)
4281 * Don't pull any tasks if this group is already above the domain
4284 if (sds.this_load >= sds.avg_load)
4287 if (env->idle == CPU_IDLE) {
4289 * This cpu is idle. If the busiest group load doesn't
4290 * have more tasks than the number of available cpu's and
4291 * there is no imbalance between this and busiest group
4292 * wrt to idle cpu's, it is balanced.
4294 if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
4295 sds.busiest_nr_running <= sds.busiest_group_weight)
4299 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
4300 * imbalance_pct to be conservative.
4302 if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
4307 /* Looks like there is an imbalance. Compute it */
4308 calculate_imbalance(env, &sds);
4318 * find_busiest_queue - find the busiest runqueue among the cpus in group.
4320 static struct rq *find_busiest_queue(struct lb_env *env,
4321 struct sched_group *group)
4323 struct rq *busiest = NULL, *rq;
4324 unsigned long max_load = 0;
4327 for_each_cpu(i, sched_group_cpus(group)) {
4328 unsigned long power = power_of(i);
4329 unsigned long capacity = DIV_ROUND_CLOSEST(power,
4334 capacity = fix_small_capacity(env->sd, group);
4336 if (!cpumask_test_cpu(i, env->cpus))
4340 wl = weighted_cpuload(i);
4343 * When comparing with imbalance, use weighted_cpuload()
4344 * which is not scaled with the cpu power.
4346 if (capacity && rq->nr_running == 1 && wl > env->imbalance)
4350 * For the load comparisons with the other cpu's, consider
4351 * the weighted_cpuload() scaled with the cpu power, so that
4352 * the load can be moved away from the cpu that is potentially
4353 * running at a lower capacity.
4355 wl = (wl * SCHED_POWER_SCALE) / power;
4357 if (wl > max_load) {
4367 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
4368 * so long as it is large enough.
4370 #define MAX_PINNED_INTERVAL 512
4372 /* Working cpumask for load_balance and load_balance_newidle. */
4373 DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
4375 static int need_active_balance(struct lb_env *env)
4377 struct sched_domain *sd = env->sd;
4379 if (env->idle == CPU_NEWLY_IDLE) {
4382 * ASYM_PACKING needs to force migrate tasks from busy but
4383 * higher numbered CPUs in order to pack all tasks in the
4384 * lowest numbered CPUs.
4386 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
4390 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
4393 static int active_load_balance_cpu_stop(void *data);
4396 * Check this_cpu to ensure it is balanced within domain. Attempt to move
4397 * tasks if there is an imbalance.
4399 static int load_balance(int this_cpu, struct rq *this_rq,
4400 struct sched_domain *sd, enum cpu_idle_type idle,
4403 int ld_moved, cur_ld_moved, active_balance = 0;
4404 int lb_iterations, max_lb_iterations;
4405 struct sched_group *group;
4407 unsigned long flags;
4408 struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
4410 struct lb_env env = {
4412 .dst_cpu = this_cpu,
4414 .dst_grpmask = sched_group_cpus(sd->groups),
4416 .loop_break = sched_nr_migrate_break,
4420 cpumask_copy(cpus, cpu_active_mask);
4421 max_lb_iterations = cpumask_weight(env.dst_grpmask);
4423 schedstat_inc(sd, lb_count[idle]);
4426 group = find_busiest_group(&env, balance);
4432 schedstat_inc(sd, lb_nobusyg[idle]);
4436 busiest = find_busiest_queue(&env, group);
4438 schedstat_inc(sd, lb_nobusyq[idle]);
4442 BUG_ON(busiest == env.dst_rq);
4444 schedstat_add(sd, lb_imbalance[idle], env.imbalance);
4448 if (busiest->nr_running > 1) {
4450 * Attempt to move tasks. If find_busiest_group has found
4451 * an imbalance but busiest->nr_running <= 1, the group is
4452 * still unbalanced. ld_moved simply stays zero, so it is
4453 * correctly treated as an imbalance.
4455 env.flags |= LBF_ALL_PINNED;
4456 env.src_cpu = busiest->cpu;
4457 env.src_rq = busiest;
4458 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
4460 update_h_load(env.src_cpu);
4462 local_irq_save(flags);
4463 double_rq_lock(env.dst_rq, busiest);
4466 * cur_ld_moved - load moved in current iteration
4467 * ld_moved - cumulative load moved across iterations
4469 cur_ld_moved = move_tasks(&env);
4470 ld_moved += cur_ld_moved;
4471 double_rq_unlock(env.dst_rq, busiest);
4472 local_irq_restore(flags);
4474 if (env.flags & LBF_NEED_BREAK) {
4475 env.flags &= ~LBF_NEED_BREAK;
4480 * some other cpu did the load balance for us.
4482 if (cur_ld_moved && env.dst_cpu != smp_processor_id())
4483 resched_cpu(env.dst_cpu);
4486 * Revisit (affine) tasks on src_cpu that couldn't be moved to
4487 * us and move them to an alternate dst_cpu in our sched_group
4488 * where they can run. The upper limit on how many times we
4489 * iterate on same src_cpu is dependent on number of cpus in our
4492 * This changes load balance semantics a bit on who can move
4493 * load to a given_cpu. In addition to the given_cpu itself
4494 * (or a ilb_cpu acting on its behalf where given_cpu is
4495 * nohz-idle), we now have balance_cpu in a position to move
4496 * load to given_cpu. In rare situations, this may cause
4497 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
4498 * _independently_ and at _same_ time to move some load to
4499 * given_cpu) causing exceess load to be moved to given_cpu.
4500 * This however should not happen so much in practice and
4501 * moreover subsequent load balance cycles should correct the
4502 * excess load moved.
4504 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 &&
4505 lb_iterations++ < max_lb_iterations) {
4507 env.dst_rq = cpu_rq(env.new_dst_cpu);
4508 env.dst_cpu = env.new_dst_cpu;
4509 env.flags &= ~LBF_SOME_PINNED;
4511 env.loop_break = sched_nr_migrate_break;
4513 * Go back to "more_balance" rather than "redo" since we
4514 * need to continue with same src_cpu.
4519 /* All tasks on this runqueue were pinned by CPU affinity */
4520 if (unlikely(env.flags & LBF_ALL_PINNED)) {
4521 cpumask_clear_cpu(cpu_of(busiest), cpus);
4522 if (!cpumask_empty(cpus)) {
4524 env.loop_break = sched_nr_migrate_break;
4532 schedstat_inc(sd, lb_failed[idle]);
4534 * Increment the failure counter only on periodic balance.
4535 * We do not want newidle balance, which can be very
4536 * frequent, pollute the failure counter causing
4537 * excessive cache_hot migrations and active balances.
4539 if (idle != CPU_NEWLY_IDLE)
4540 sd->nr_balance_failed++;
4542 if (need_active_balance(&env)) {
4543 raw_spin_lock_irqsave(&busiest->lock, flags);
4545 /* don't kick the active_load_balance_cpu_stop,
4546 * if the curr task on busiest cpu can't be
4549 if (!cpumask_test_cpu(this_cpu,
4550 tsk_cpus_allowed(busiest->curr))) {
4551 raw_spin_unlock_irqrestore(&busiest->lock,
4553 env.flags |= LBF_ALL_PINNED;
4554 goto out_one_pinned;
4558 * ->active_balance synchronizes accesses to
4559 * ->active_balance_work. Once set, it's cleared
4560 * only after active load balance is finished.
4562 if (!busiest->active_balance) {
4563 busiest->active_balance = 1;
4564 busiest->push_cpu = this_cpu;
4567 raw_spin_unlock_irqrestore(&busiest->lock, flags);
4569 if (active_balance) {
4570 stop_one_cpu_nowait(cpu_of(busiest),
4571 active_load_balance_cpu_stop, busiest,
4572 &busiest->active_balance_work);
4576 * We've kicked active balancing, reset the failure
4579 sd->nr_balance_failed = sd->cache_nice_tries+1;
4582 sd->nr_balance_failed = 0;
4584 if (likely(!active_balance)) {
4585 /* We were unbalanced, so reset the balancing interval */
4586 sd->balance_interval = sd->min_interval;
4589 * If we've begun active balancing, start to back off. This
4590 * case may not be covered by the all_pinned logic if there
4591 * is only 1 task on the busy runqueue (because we don't call
4594 if (sd->balance_interval < sd->max_interval)
4595 sd->balance_interval *= 2;
4601 schedstat_inc(sd, lb_balanced[idle]);
4603 sd->nr_balance_failed = 0;
4606 /* tune up the balancing interval */
4607 if (((env.flags & LBF_ALL_PINNED) &&
4608 sd->balance_interval < MAX_PINNED_INTERVAL) ||
4609 (sd->balance_interval < sd->max_interval))
4610 sd->balance_interval *= 2;
4618 * idle_balance is called by schedule() if this_cpu is about to become
4619 * idle. Attempts to pull tasks from other CPUs.
4621 void idle_balance(int this_cpu, struct rq *this_rq)
4623 struct sched_domain *sd;
4624 int pulled_task = 0;
4625 unsigned long next_balance = jiffies + HZ;
4627 this_rq->idle_stamp = this_rq->clock;
4629 if (this_rq->avg_idle < sysctl_sched_migration_cost)
4633 * Drop the rq->lock, but keep IRQ/preempt disabled.
4635 raw_spin_unlock(&this_rq->lock);
4637 update_shares(this_cpu);
4639 for_each_domain(this_cpu, sd) {
4640 unsigned long interval;
4643 if (!(sd->flags & SD_LOAD_BALANCE))
4646 if (sd->flags & SD_BALANCE_NEWIDLE) {
4647 /* If we've pulled tasks over stop searching: */
4648 pulled_task = load_balance(this_cpu, this_rq,
4649 sd, CPU_NEWLY_IDLE, &balance);
4652 interval = msecs_to_jiffies(sd->balance_interval);
4653 if (time_after(next_balance, sd->last_balance + interval))
4654 next_balance = sd->last_balance + interval;
4656 this_rq->idle_stamp = 0;
4662 raw_spin_lock(&this_rq->lock);
4664 if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
4666 * We are going idle. next_balance may be set based on
4667 * a busy processor. So reset next_balance.
4669 this_rq->next_balance = next_balance;
4674 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
4675 * running tasks off the busiest CPU onto idle CPUs. It requires at
4676 * least 1 task to be running on each physical CPU where possible, and
4677 * avoids physical / logical imbalances.
4679 static int active_load_balance_cpu_stop(void *data)
4681 struct rq *busiest_rq = data;
4682 int busiest_cpu = cpu_of(busiest_rq);
4683 int target_cpu = busiest_rq->push_cpu;
4684 struct rq *target_rq = cpu_rq(target_cpu);
4685 struct sched_domain *sd;
4687 raw_spin_lock_irq(&busiest_rq->lock);
4689 /* make sure the requested cpu hasn't gone down in the meantime */
4690 if (unlikely(busiest_cpu != smp_processor_id() ||
4691 !busiest_rq->active_balance))
4694 /* Is there any task to move? */
4695 if (busiest_rq->nr_running <= 1)
4699 * This condition is "impossible", if it occurs
4700 * we need to fix it. Originally reported by
4701 * Bjorn Helgaas on a 128-cpu setup.
4703 BUG_ON(busiest_rq == target_rq);
4705 /* move a task from busiest_rq to target_rq */
4706 double_lock_balance(busiest_rq, target_rq);
4708 /* Search for an sd spanning us and the target CPU. */
4710 for_each_domain(target_cpu, sd) {
4711 if ((sd->flags & SD_LOAD_BALANCE) &&
4712 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
4717 struct lb_env env = {
4719 .dst_cpu = target_cpu,
4720 .dst_rq = target_rq,
4721 .src_cpu = busiest_rq->cpu,
4722 .src_rq = busiest_rq,
4726 schedstat_inc(sd, alb_count);
4728 if (move_one_task(&env))
4729 schedstat_inc(sd, alb_pushed);
4731 schedstat_inc(sd, alb_failed);
4734 double_unlock_balance(busiest_rq, target_rq);
4736 busiest_rq->active_balance = 0;
4737 raw_spin_unlock_irq(&busiest_rq->lock);
4743 * idle load balancing details
4744 * - When one of the busy CPUs notice that there may be an idle rebalancing
4745 * needed, they will kick the idle load balancer, which then does idle
4746 * load balancing for all the idle CPUs.
4749 cpumask_var_t idle_cpus_mask;
4751 unsigned long next_balance; /* in jiffy units */
4752 } nohz ____cacheline_aligned;
4754 static inline int find_new_ilb(int call_cpu)
4756 int ilb = cpumask_first(nohz.idle_cpus_mask);
4758 if (ilb < nr_cpu_ids && idle_cpu(ilb))
4765 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
4766 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
4767 * CPU (if there is one).
4769 static void nohz_balancer_kick(int cpu)
4773 nohz.next_balance++;
4775 ilb_cpu = find_new_ilb(cpu);
4777 if (ilb_cpu >= nr_cpu_ids)
4780 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
4783 * Use smp_send_reschedule() instead of resched_cpu().
4784 * This way we generate a sched IPI on the target cpu which
4785 * is idle. And the softirq performing nohz idle load balance
4786 * will be run before returning from the IPI.
4788 smp_send_reschedule(ilb_cpu);
4792 static inline void nohz_balance_exit_idle(int cpu)
4794 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
4795 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
4796 atomic_dec(&nohz.nr_cpus);
4797 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
4801 static inline void set_cpu_sd_state_busy(void)
4803 struct sched_domain *sd;
4804 int cpu = smp_processor_id();
4806 if (!test_bit(NOHZ_IDLE, nohz_flags(cpu)))
4808 clear_bit(NOHZ_IDLE, nohz_flags(cpu));
4811 for_each_domain(cpu, sd)
4812 atomic_inc(&sd->groups->sgp->nr_busy_cpus);
4816 void set_cpu_sd_state_idle(void)
4818 struct sched_domain *sd;
4819 int cpu = smp_processor_id();
4821 if (test_bit(NOHZ_IDLE, nohz_flags(cpu)))
4823 set_bit(NOHZ_IDLE, nohz_flags(cpu));
4826 for_each_domain(cpu, sd)
4827 atomic_dec(&sd->groups->sgp->nr_busy_cpus);
4832 * This routine will record that the cpu is going idle with tick stopped.
4833 * This info will be used in performing idle load balancing in the future.
4835 void nohz_balance_enter_idle(int cpu)
4838 * If this cpu is going down, then nothing needs to be done.
4840 if (!cpu_active(cpu))
4843 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
4846 cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
4847 atomic_inc(&nohz.nr_cpus);
4848 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
4851 static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
4852 unsigned long action, void *hcpu)
4854 switch (action & ~CPU_TASKS_FROZEN) {
4856 nohz_balance_exit_idle(smp_processor_id());
4864 static DEFINE_SPINLOCK(balancing);
4867 * Scale the max load_balance interval with the number of CPUs in the system.
4868 * This trades load-balance latency on larger machines for less cross talk.
4870 void update_max_interval(void)
4872 max_load_balance_interval = HZ*num_online_cpus()/10;
4876 * It checks each scheduling domain to see if it is due to be balanced,
4877 * and initiates a balancing operation if so.
4879 * Balancing parameters are set up in arch_init_sched_domains.
4881 static void rebalance_domains(int cpu, enum cpu_idle_type idle)
4884 struct rq *rq = cpu_rq(cpu);
4885 unsigned long interval;
4886 struct sched_domain *sd;
4887 /* Earliest time when we have to do rebalance again */
4888 unsigned long next_balance = jiffies + 60*HZ;
4889 int update_next_balance = 0;
4895 for_each_domain(cpu, sd) {
4896 if (!(sd->flags & SD_LOAD_BALANCE))
4899 interval = sd->balance_interval;
4900 if (idle != CPU_IDLE)
4901 interval *= sd->busy_factor;
4903 /* scale ms to jiffies */
4904 interval = msecs_to_jiffies(interval);
4905 interval = clamp(interval, 1UL, max_load_balance_interval);
4907 need_serialize = sd->flags & SD_SERIALIZE;
4909 if (need_serialize) {
4910 if (!spin_trylock(&balancing))
4914 if (time_after_eq(jiffies, sd->last_balance + interval)) {
4915 if (load_balance(cpu, rq, sd, idle, &balance)) {
4917 * We've pulled tasks over so either we're no
4920 idle = CPU_NOT_IDLE;
4922 sd->last_balance = jiffies;
4925 spin_unlock(&balancing);
4927 if (time_after(next_balance, sd->last_balance + interval)) {
4928 next_balance = sd->last_balance + interval;
4929 update_next_balance = 1;
4933 * Stop the load balance at this level. There is another
4934 * CPU in our sched group which is doing load balancing more
4943 * next_balance will be updated only when there is a need.
4944 * When the cpu is attached to null domain for ex, it will not be
4947 if (likely(update_next_balance))
4948 rq->next_balance = next_balance;
4953 * In CONFIG_NO_HZ case, the idle balance kickee will do the
4954 * rebalancing for all the cpus for whom scheduler ticks are stopped.
4956 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
4958 struct rq *this_rq = cpu_rq(this_cpu);
4962 if (idle != CPU_IDLE ||
4963 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
4966 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
4967 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
4971 * If this cpu gets work to do, stop the load balancing
4972 * work being done for other cpus. Next load
4973 * balancing owner will pick it up.
4978 rq = cpu_rq(balance_cpu);
4980 raw_spin_lock_irq(&rq->lock);
4981 update_rq_clock(rq);
4982 update_idle_cpu_load(rq);
4983 raw_spin_unlock_irq(&rq->lock);
4985 rebalance_domains(balance_cpu, CPU_IDLE);
4987 if (time_after(this_rq->next_balance, rq->next_balance))
4988 this_rq->next_balance = rq->next_balance;
4990 nohz.next_balance = this_rq->next_balance;
4992 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
4996 * Current heuristic for kicking the idle load balancer in the presence
4997 * of an idle cpu is the system.
4998 * - This rq has more than one task.
4999 * - At any scheduler domain level, this cpu's scheduler group has multiple
5000 * busy cpu's exceeding the group's power.
5001 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
5002 * domain span are idle.
5004 static inline int nohz_kick_needed(struct rq *rq, int cpu)
5006 unsigned long now = jiffies;
5007 struct sched_domain *sd;
5009 if (unlikely(idle_cpu(cpu)))
5013 * We may be recently in ticked or tickless idle mode. At the first
5014 * busy tick after returning from idle, we will update the busy stats.
5016 set_cpu_sd_state_busy();
5017 nohz_balance_exit_idle(cpu);
5020 * None are in tickless mode and hence no need for NOHZ idle load
5023 if (likely(!atomic_read(&nohz.nr_cpus)))
5026 if (time_before(now, nohz.next_balance))
5029 if (rq->nr_running >= 2)
5033 for_each_domain(cpu, sd) {
5034 struct sched_group *sg = sd->groups;
5035 struct sched_group_power *sgp = sg->sgp;
5036 int nr_busy = atomic_read(&sgp->nr_busy_cpus);
5038 if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5039 goto need_kick_unlock;
5041 if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
5042 && (cpumask_first_and(nohz.idle_cpus_mask,
5043 sched_domain_span(sd)) < cpu))
5044 goto need_kick_unlock;
5046 if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
5058 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
5062 * run_rebalance_domains is triggered when needed from the scheduler tick.
5063 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
5065 static void run_rebalance_domains(struct softirq_action *h)
5067 int this_cpu = smp_processor_id();
5068 struct rq *this_rq = cpu_rq(this_cpu);
5069 enum cpu_idle_type idle = this_rq->idle_balance ?
5070 CPU_IDLE : CPU_NOT_IDLE;
5072 rebalance_domains(this_cpu, idle);
5075 * If this cpu has a pending nohz_balance_kick, then do the
5076 * balancing on behalf of the other idle cpus whose ticks are
5079 nohz_idle_balance(this_cpu, idle);
5082 static inline int on_null_domain(int cpu)
5084 return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5088 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
5090 void trigger_load_balance(struct rq *rq, int cpu)
5092 /* Don't need to rebalance while attached to NULL domain */
5093 if (time_after_eq(jiffies, rq->next_balance) &&
5094 likely(!on_null_domain(cpu)))
5095 raise_softirq(SCHED_SOFTIRQ);
5097 if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
5098 nohz_balancer_kick(cpu);
5102 static void rq_online_fair(struct rq *rq)
5107 static void rq_offline_fair(struct rq *rq)
5111 /* Ensure any throttled groups are reachable by pick_next_task */
5112 unthrottle_offline_cfs_rqs(rq);
5115 #endif /* CONFIG_SMP */
5118 * scheduler tick hitting a task of our scheduling class:
5120 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
5122 struct cfs_rq *cfs_rq;
5123 struct sched_entity *se = &curr->se;
5125 for_each_sched_entity(se) {
5126 cfs_rq = cfs_rq_of(se);
5127 entity_tick(cfs_rq, se, queued);
5130 if (sched_feat_numa(NUMA))
5131 task_tick_numa(rq, curr);
5135 * called on fork with the child task as argument from the parent's context
5136 * - child not yet on the tasklist
5137 * - preemption disabled
5139 static void task_fork_fair(struct task_struct *p)
5141 struct cfs_rq *cfs_rq;
5142 struct sched_entity *se = &p->se, *curr;
5143 int this_cpu = smp_processor_id();
5144 struct rq *rq = this_rq();
5145 unsigned long flags;
5147 raw_spin_lock_irqsave(&rq->lock, flags);
5149 update_rq_clock(rq);
5151 cfs_rq = task_cfs_rq(current);
5152 curr = cfs_rq->curr;
5154 if (unlikely(task_cpu(p) != this_cpu)) {
5156 __set_task_cpu(p, this_cpu);
5160 update_curr(cfs_rq);
5163 se->vruntime = curr->vruntime;
5164 place_entity(cfs_rq, se, 1);
5166 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
5168 * Upon rescheduling, sched_class::put_prev_task() will place
5169 * 'current' within the tree based on its new key value.
5171 swap(curr->vruntime, se->vruntime);
5172 resched_task(rq->curr);
5175 se->vruntime -= cfs_rq->min_vruntime;
5177 raw_spin_unlock_irqrestore(&rq->lock, flags);
5181 * Priority of the task has changed. Check to see if we preempt
5185 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
5191 * Reschedule if we are currently running on this runqueue and
5192 * our priority decreased, or if we are not currently running on
5193 * this runqueue and our priority is higher than the current's
5195 if (rq->curr == p) {
5196 if (p->prio > oldprio)
5197 resched_task(rq->curr);
5199 check_preempt_curr(rq, p, 0);
5202 static void switched_from_fair(struct rq *rq, struct task_struct *p)
5204 struct sched_entity *se = &p->se;
5205 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5208 * Ensure the task's vruntime is normalized, so that when its
5209 * switched back to the fair class the enqueue_entity(.flags=0) will
5210 * do the right thing.
5212 * If it was on_rq, then the dequeue_entity(.flags=0) will already
5213 * have normalized the vruntime, if it was !on_rq, then only when
5214 * the task is sleeping will it still have non-normalized vruntime.
5216 if (!se->on_rq && p->state != TASK_RUNNING) {
5218 * Fix up our vruntime so that the current sleep doesn't
5219 * cause 'unlimited' sleep bonus.
5221 place_entity(cfs_rq, se, 0);
5222 se->vruntime -= cfs_rq->min_vruntime;
5227 * We switched to the sched_fair class.
5229 static void switched_to_fair(struct rq *rq, struct task_struct *p)
5235 * We were most likely switched from sched_rt, so
5236 * kick off the schedule if running, otherwise just see
5237 * if we can still preempt the current task.
5240 resched_task(rq->curr);
5242 check_preempt_curr(rq, p, 0);
5245 /* Account for a task changing its policy or group.
5247 * This routine is mostly called to set cfs_rq->curr field when a task
5248 * migrates between groups/classes.
5250 static void set_curr_task_fair(struct rq *rq)
5252 struct sched_entity *se = &rq->curr->se;
5254 for_each_sched_entity(se) {
5255 struct cfs_rq *cfs_rq = cfs_rq_of(se);
5257 set_next_entity(cfs_rq, se);
5258 /* ensure bandwidth has been allocated on our new cfs_rq */
5259 account_cfs_rq_runtime(cfs_rq, 0);
5263 void init_cfs_rq(struct cfs_rq *cfs_rq)
5265 cfs_rq->tasks_timeline = RB_ROOT;
5266 cfs_rq->min_vruntime = (u64)(-(1LL << 20));
5267 #ifndef CONFIG_64BIT
5268 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
5272 #ifdef CONFIG_FAIR_GROUP_SCHED
5273 static void task_move_group_fair(struct task_struct *p, int on_rq)
5276 * If the task was not on the rq at the time of this cgroup movement
5277 * it must have been asleep, sleeping tasks keep their ->vruntime
5278 * absolute on their old rq until wakeup (needed for the fair sleeper
5279 * bonus in place_entity()).
5281 * If it was on the rq, we've just 'preempted' it, which does convert
5282 * ->vruntime to a relative base.
5284 * Make sure both cases convert their relative position when migrating
5285 * to another cgroup's rq. This does somewhat interfere with the
5286 * fair sleeper stuff for the first placement, but who cares.
5289 * When !on_rq, vruntime of the task has usually NOT been normalized.
5290 * But there are some cases where it has already been normalized:
5292 * - Moving a forked child which is waiting for being woken up by
5293 * wake_up_new_task().
5294 * - Moving a task which has been woken up by try_to_wake_up() and
5295 * waiting for actually being woken up by sched_ttwu_pending().
5297 * To prevent boost or penalty in the new cfs_rq caused by delta
5298 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
5300 if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
5304 p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
5305 set_task_rq(p, task_cpu(p));
5307 p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
5310 void free_fair_sched_group(struct task_group *tg)
5314 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));
5316 for_each_possible_cpu(i) {
5318 kfree(tg->cfs_rq[i]);
5327 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
5329 struct cfs_rq *cfs_rq;
5330 struct sched_entity *se;
5333 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
5336 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
5340 tg->shares = NICE_0_LOAD;
5342 init_cfs_bandwidth(tg_cfs_bandwidth(tg));
5344 for_each_possible_cpu(i) {
5345 cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
5346 GFP_KERNEL, cpu_to_node(i));
5350 se = kzalloc_node(sizeof(struct sched_entity),
5351 GFP_KERNEL, cpu_to_node(i));
5355 init_cfs_rq(cfs_rq);
5356 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
5367 void unregister_fair_sched_group(struct task_group *tg, int cpu)
5369 struct rq *rq = cpu_rq(cpu);
5370 unsigned long flags;
5373 * Only empty task groups can be destroyed; so we can speculatively
5374 * check on_list without danger of it being re-added.
5376 if (!tg->cfs_rq[cpu]->on_list)
5379 raw_spin_lock_irqsave(&rq->lock, flags);
5380 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
5381 raw_spin_unlock_irqrestore(&rq->lock, flags);
5384 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
5385 struct sched_entity *se, int cpu,
5386 struct sched_entity *parent)
5388 struct rq *rq = cpu_rq(cpu);
5393 /* allow initial update_cfs_load() to truncate */
5394 cfs_rq->load_stamp = 1;
5396 init_cfs_rq_runtime(cfs_rq);
5398 tg->cfs_rq[cpu] = cfs_rq;
5401 /* se could be NULL for root_task_group */
5406 se->cfs_rq = &rq->cfs;
5408 se->cfs_rq = parent->my_q;
5411 update_load_set(&se->load, 0);
5412 se->parent = parent;
5415 static DEFINE_MUTEX(shares_mutex);
5417 int sched_group_set_shares(struct task_group *tg, unsigned long shares)
5420 unsigned long flags;
5423 * We can't change the weight of the root cgroup.
5428 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
5430 mutex_lock(&shares_mutex);
5431 if (tg->shares == shares)
5434 tg->shares = shares;
5435 for_each_possible_cpu(i) {
5436 struct rq *rq = cpu_rq(i);
5437 struct sched_entity *se;
5440 /* Propagate contribution to hierarchy */
5441 raw_spin_lock_irqsave(&rq->lock, flags);
5442 for_each_sched_entity(se)
5443 update_cfs_shares(group_cfs_rq(se));
5444 raw_spin_unlock_irqrestore(&rq->lock, flags);
5448 mutex_unlock(&shares_mutex);
5451 #else /* CONFIG_FAIR_GROUP_SCHED */
5453 void free_fair_sched_group(struct task_group *tg) { }
5455 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
5460 void unregister_fair_sched_group(struct task_group *tg, int cpu) { }
5462 #endif /* CONFIG_FAIR_GROUP_SCHED */
5465 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
5467 struct sched_entity *se = &task->se;
5468 unsigned int rr_interval = 0;
5471 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
5474 if (rq->cfs.load.weight)
5475 rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
5481 * All the scheduling class methods:
5483 const struct sched_class fair_sched_class = {
5484 .next = &idle_sched_class,
5485 .enqueue_task = enqueue_task_fair,
5486 .dequeue_task = dequeue_task_fair,
5487 .yield_task = yield_task_fair,
5488 .yield_to_task = yield_to_task_fair,
5490 .check_preempt_curr = check_preempt_wakeup,
5492 .pick_next_task = pick_next_task_fair,
5493 .put_prev_task = put_prev_task_fair,
5496 .select_task_rq = select_task_rq_fair,
5498 .rq_online = rq_online_fair,
5499 .rq_offline = rq_offline_fair,
5501 .task_waking = task_waking_fair,
5504 .set_curr_task = set_curr_task_fair,
5505 .task_tick = task_tick_fair,
5506 .task_fork = task_fork_fair,
5508 .prio_changed = prio_changed_fair,
5509 .switched_from = switched_from_fair,
5510 .switched_to = switched_to_fair,
5512 .get_rr_interval = get_rr_interval_fair,
5514 #ifdef CONFIG_FAIR_GROUP_SCHED
5515 .task_move_group = task_move_group_fair,
5519 #ifdef CONFIG_SCHED_DEBUG
5520 void print_cfs_stats(struct seq_file *m, int cpu)
5522 struct cfs_rq *cfs_rq;
5525 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
5526 print_cfs_rq(m, cpu, cfs_rq);
5531 __init void init_sched_fair_class(void)
5534 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
5537 nohz.next_balance = jiffies;
5538 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
5539 cpu_notifier(sched_ilb_notifier, 0);