2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
23 #include <linux/sched.h>
24 #include <linux/latencytop.h>
25 #include <linux/cpumask.h>
26 #include <linux/cpuidle.h>
27 #include <linux/slab.h>
28 #include <linux/profile.h>
29 #include <linux/interrupt.h>
30 #include <linux/mempolicy.h>
31 #include <linux/migrate.h>
32 #include <linux/task_work.h>
34 #include <trace/events/sched.h>
39 * Targeted preemption latency for CPU-bound tasks:
40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
42 * NOTE: this latency value is not the same as the concept of
43 * 'timeslice length' - timeslices in CFS are of variable length
44 * and have no persistent notion like in traditional, time-slice
45 * based scheduling concepts.
47 * (to see the precise effective timeslice length of your workload,
48 * run vmstat and monitor the context-switches (cs) field)
50 unsigned int sysctl_sched_latency
= 6000000ULL;
51 unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
54 * The initial- and re-scaling of tunables is configurable
55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
62 enum sched_tunable_scaling sysctl_sched_tunable_scaling
63 = SCHED_TUNABLESCALING_LOG
;
66 * Minimal preemption granularity for CPU-bound tasks:
67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
69 unsigned int sysctl_sched_min_granularity
= 750000ULL;
70 unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
75 static unsigned int sched_nr_latency
= 8;
78 * After fork, child runs first. If set to 0 (default) then
79 * parent will (try to) run first.
81 unsigned int sysctl_sched_child_runs_first __read_mostly
;
84 * SCHED_OTHER wake-up granularity.
85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
87 * This option delays the preemption effects of decoupled workloads
88 * and reduces their over-scheduling. Synchronous workloads will still
89 * have immediate wakeup/sleep latencies.
91 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
92 unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
94 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
97 * The exponential sliding window over which load is averaged for shares
101 unsigned int __read_mostly sysctl_sched_shares_window
= 10000000UL;
103 #ifdef CONFIG_CFS_BANDWIDTH
105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
106 * each time a cfs_rq requests quota.
108 * Note: in the case that the slice exceeds the runtime remaining (either due
109 * to consumption or the quota being specified to be smaller than the slice)
110 * we will always only issue the remaining available time.
112 * default: 5 msec, units: microseconds
114 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
117 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
123 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
129 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
136 * Increase the granularity value when there are more CPUs,
137 * because with more CPUs the 'effective latency' as visible
138 * to users decreases. But the relationship is not linear,
139 * so pick a second-best guess by going with the log2 of the
142 * This idea comes from the SD scheduler of Con Kolivas:
144 static unsigned int get_update_sysctl_factor(void)
146 unsigned int cpus
= min_t(unsigned int, num_online_cpus(), 8);
149 switch (sysctl_sched_tunable_scaling
) {
150 case SCHED_TUNABLESCALING_NONE
:
153 case SCHED_TUNABLESCALING_LINEAR
:
156 case SCHED_TUNABLESCALING_LOG
:
158 factor
= 1 + ilog2(cpus
);
165 static void update_sysctl(void)
167 unsigned int factor
= get_update_sysctl_factor();
169 #define SET_SYSCTL(name) \
170 (sysctl_##name = (factor) * normalized_sysctl_##name)
171 SET_SYSCTL(sched_min_granularity
);
172 SET_SYSCTL(sched_latency
);
173 SET_SYSCTL(sched_wakeup_granularity
);
177 void sched_init_granularity(void)
182 #define WMULT_CONST (~0U)
183 #define WMULT_SHIFT 32
185 static void __update_inv_weight(struct load_weight
*lw
)
189 if (likely(lw
->inv_weight
))
192 w
= scale_load_down(lw
->weight
);
194 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
196 else if (unlikely(!w
))
197 lw
->inv_weight
= WMULT_CONST
;
199 lw
->inv_weight
= WMULT_CONST
/ w
;
203 * delta_exec * weight / lw.weight
205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
207 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
208 * we're guaranteed shift stays positive because inv_weight is guaranteed to
209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
212 * weight/lw.weight <= 1, and therefore our shift will also be positive.
214 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
216 u64 fact
= scale_load_down(weight
);
217 int shift
= WMULT_SHIFT
;
219 __update_inv_weight(lw
);
221 if (unlikely(fact
>> 32)) {
228 /* hint to use a 32x32->64 mul */
229 fact
= (u64
)(u32
)fact
* lw
->inv_weight
;
236 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
240 const struct sched_class fair_sched_class
;
242 /**************************************************************
243 * CFS operations on generic schedulable entities:
246 #ifdef CONFIG_FAIR_GROUP_SCHED
248 /* cpu runqueue to which this cfs_rq is attached */
249 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
254 /* An entity is a task if it doesn't "own" a runqueue */
255 #define entity_is_task(se) (!se->my_q)
257 static inline struct task_struct
*task_of(struct sched_entity
*se
)
259 #ifdef CONFIG_SCHED_DEBUG
260 WARN_ON_ONCE(!entity_is_task(se
));
262 return container_of(se
, struct task_struct
, se
);
265 /* Walk up scheduling entities hierarchy */
266 #define for_each_sched_entity(se) \
267 for (; se; se = se->parent)
269 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
274 /* runqueue on which this entity is (to be) queued */
275 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
280 /* runqueue "owned" by this group */
281 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
286 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
288 if (!cfs_rq
->on_list
) {
290 * Ensure we either appear before our parent (if already
291 * enqueued) or force our parent to appear after us when it is
292 * enqueued. The fact that we always enqueue bottom-up
293 * reduces this to two cases.
295 if (cfs_rq
->tg
->parent
&&
296 cfs_rq
->tg
->parent
->cfs_rq
[cpu_of(rq_of(cfs_rq
))]->on_list
) {
297 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
298 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
300 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
301 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
308 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
310 if (cfs_rq
->on_list
) {
311 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
316 /* Iterate thr' all leaf cfs_rq's on a runqueue */
317 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
318 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
320 /* Do the two (enqueued) entities belong to the same group ? */
321 static inline struct cfs_rq
*
322 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
324 if (se
->cfs_rq
== pse
->cfs_rq
)
330 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
336 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
338 int se_depth
, pse_depth
;
341 * preemption test can be made between sibling entities who are in the
342 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
343 * both tasks until we find their ancestors who are siblings of common
347 /* First walk up until both entities are at same depth */
348 se_depth
= (*se
)->depth
;
349 pse_depth
= (*pse
)->depth
;
351 while (se_depth
> pse_depth
) {
353 *se
= parent_entity(*se
);
356 while (pse_depth
> se_depth
) {
358 *pse
= parent_entity(*pse
);
361 while (!is_same_group(*se
, *pse
)) {
362 *se
= parent_entity(*se
);
363 *pse
= parent_entity(*pse
);
367 #else /* !CONFIG_FAIR_GROUP_SCHED */
369 static inline struct task_struct
*task_of(struct sched_entity
*se
)
371 return container_of(se
, struct task_struct
, se
);
374 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
376 return container_of(cfs_rq
, struct rq
, cfs
);
379 #define entity_is_task(se) 1
381 #define for_each_sched_entity(se) \
382 for (; se; se = NULL)
384 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
386 return &task_rq(p
)->cfs
;
389 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
391 struct task_struct
*p
= task_of(se
);
392 struct rq
*rq
= task_rq(p
);
397 /* runqueue "owned" by this group */
398 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
403 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
407 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
411 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
412 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
414 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
420 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
424 #endif /* CONFIG_FAIR_GROUP_SCHED */
426 static __always_inline
427 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
429 /**************************************************************
430 * Scheduling class tree data structure manipulation methods:
433 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
435 s64 delta
= (s64
)(vruntime
- max_vruntime
);
437 max_vruntime
= vruntime
;
442 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
444 s64 delta
= (s64
)(vruntime
- min_vruntime
);
446 min_vruntime
= vruntime
;
451 static inline int entity_before(struct sched_entity
*a
,
452 struct sched_entity
*b
)
454 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
457 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
459 u64 vruntime
= cfs_rq
->min_vruntime
;
462 vruntime
= cfs_rq
->curr
->vruntime
;
464 if (cfs_rq
->rb_leftmost
) {
465 struct sched_entity
*se
= rb_entry(cfs_rq
->rb_leftmost
,
470 vruntime
= se
->vruntime
;
472 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
475 /* ensure we never gain time by being placed backwards. */
476 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
479 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
484 * Enqueue an entity into the rb-tree:
486 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
488 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
489 struct rb_node
*parent
= NULL
;
490 struct sched_entity
*entry
;
494 * Find the right place in the rbtree:
498 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
500 * We dont care about collisions. Nodes with
501 * the same key stay together.
503 if (entity_before(se
, entry
)) {
504 link
= &parent
->rb_left
;
506 link
= &parent
->rb_right
;
512 * Maintain a cache of leftmost tree entries (it is frequently
516 cfs_rq
->rb_leftmost
= &se
->run_node
;
518 rb_link_node(&se
->run_node
, parent
, link
);
519 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
522 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
524 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
525 struct rb_node
*next_node
;
527 next_node
= rb_next(&se
->run_node
);
528 cfs_rq
->rb_leftmost
= next_node
;
531 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
534 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
536 struct rb_node
*left
= cfs_rq
->rb_leftmost
;
541 return rb_entry(left
, struct sched_entity
, run_node
);
544 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
546 struct rb_node
*next
= rb_next(&se
->run_node
);
551 return rb_entry(next
, struct sched_entity
, run_node
);
554 #ifdef CONFIG_SCHED_DEBUG
555 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
557 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
562 return rb_entry(last
, struct sched_entity
, run_node
);
565 /**************************************************************
566 * Scheduling class statistics methods:
569 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
570 void __user
*buffer
, size_t *lenp
,
573 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
574 unsigned int factor
= get_update_sysctl_factor();
579 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
580 sysctl_sched_min_granularity
);
582 #define WRT_SYSCTL(name) \
583 (normalized_sysctl_##name = sysctl_##name / (factor))
584 WRT_SYSCTL(sched_min_granularity
);
585 WRT_SYSCTL(sched_latency
);
586 WRT_SYSCTL(sched_wakeup_granularity
);
596 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
598 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
599 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
605 * The idea is to set a period in which each task runs once.
607 * When there are too many tasks (sched_nr_latency) we have to stretch
608 * this period because otherwise the slices get too small.
610 * p = (nr <= nl) ? l : l*nr/nl
612 static u64
__sched_period(unsigned long nr_running
)
614 if (unlikely(nr_running
> sched_nr_latency
))
615 return nr_running
* sysctl_sched_min_granularity
;
617 return sysctl_sched_latency
;
621 * We calculate the wall-time slice from the period by taking a part
622 * proportional to the weight.
626 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
628 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
630 for_each_sched_entity(se
) {
631 struct load_weight
*load
;
632 struct load_weight lw
;
634 cfs_rq
= cfs_rq_of(se
);
635 load
= &cfs_rq
->load
;
637 if (unlikely(!se
->on_rq
)) {
640 update_load_add(&lw
, se
->load
.weight
);
643 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
649 * We calculate the vruntime slice of a to-be-inserted task.
653 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
655 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
659 static int select_idle_sibling(struct task_struct
*p
, int cpu
);
660 static unsigned long task_h_load(struct task_struct
*p
);
663 * We choose a half-life close to 1 scheduling period.
664 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
665 * dependent on this value.
667 #define LOAD_AVG_PERIOD 32
668 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
671 /* Give new sched_entity start runnable values to heavy its load in infant time */
672 void init_entity_runnable_average(struct sched_entity
*se
)
674 struct sched_avg
*sa
= &se
->avg
;
676 sa
->last_update_time
= 0;
678 * sched_avg's period_contrib should be strictly less then 1024, so
679 * we give it 1023 to make sure it is almost a period (1024us), and
680 * will definitely be update (after enqueue).
682 sa
->period_contrib
= 1023;
683 sa
->load_avg
= scale_load_down(se
->load
.weight
);
684 sa
->load_sum
= sa
->load_avg
* LOAD_AVG_MAX
;
686 * At this point, util_avg won't be used in select_task_rq_fair anyway
690 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
694 * With new tasks being created, their initial util_avgs are extrapolated
695 * based on the cfs_rq's current util_avg:
697 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
699 * However, in many cases, the above util_avg does not give a desired
700 * value. Moreover, the sum of the util_avgs may be divergent, such
701 * as when the series is a harmonic series.
703 * To solve this problem, we also cap the util_avg of successive tasks to
704 * only 1/2 of the left utilization budget:
706 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
708 * where n denotes the nth task.
710 * For example, a simplest series from the beginning would be like:
712 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
713 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
715 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
716 * if util_avg > util_avg_cap.
718 void post_init_entity_util_avg(struct sched_entity
*se
)
720 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
721 struct sched_avg
*sa
= &se
->avg
;
722 long cap
= (long)(SCHED_CAPACITY_SCALE
- cfs_rq
->avg
.util_avg
) / 2;
725 if (cfs_rq
->avg
.util_avg
!= 0) {
726 sa
->util_avg
= cfs_rq
->avg
.util_avg
* se
->load
.weight
;
727 sa
->util_avg
/= (cfs_rq
->avg
.load_avg
+ 1);
729 if (sa
->util_avg
> cap
)
734 sa
->util_sum
= sa
->util_avg
* LOAD_AVG_MAX
;
738 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
);
739 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
);
741 void init_entity_runnable_average(struct sched_entity
*se
)
744 void post_init_entity_util_avg(struct sched_entity
*se
)
750 * Update the current task's runtime statistics.
752 static void update_curr(struct cfs_rq
*cfs_rq
)
754 struct sched_entity
*curr
= cfs_rq
->curr
;
755 u64 now
= rq_clock_task(rq_of(cfs_rq
));
761 delta_exec
= now
- curr
->exec_start
;
762 if (unlikely((s64
)delta_exec
<= 0))
765 curr
->exec_start
= now
;
767 schedstat_set(curr
->statistics
.exec_max
,
768 max(delta_exec
, curr
->statistics
.exec_max
));
770 curr
->sum_exec_runtime
+= delta_exec
;
771 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
773 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
774 update_min_vruntime(cfs_rq
);
776 if (entity_is_task(curr
)) {
777 struct task_struct
*curtask
= task_of(curr
);
779 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
780 cpuacct_charge(curtask
, delta_exec
);
781 account_group_exec_runtime(curtask
, delta_exec
);
784 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
787 static void update_curr_fair(struct rq
*rq
)
789 update_curr(cfs_rq_of(&rq
->curr
->se
));
792 #ifdef CONFIG_SCHEDSTATS
794 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
796 u64 wait_start
= rq_clock(rq_of(cfs_rq
));
798 if (entity_is_task(se
) && task_on_rq_migrating(task_of(se
)) &&
799 likely(wait_start
> se
->statistics
.wait_start
))
800 wait_start
-= se
->statistics
.wait_start
;
802 se
->statistics
.wait_start
= wait_start
;
806 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
808 struct task_struct
*p
;
811 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.wait_start
;
813 if (entity_is_task(se
)) {
815 if (task_on_rq_migrating(p
)) {
817 * Preserve migrating task's wait time so wait_start
818 * time stamp can be adjusted to accumulate wait time
819 * prior to migration.
821 se
->statistics
.wait_start
= delta
;
824 trace_sched_stat_wait(p
, delta
);
827 se
->statistics
.wait_max
= max(se
->statistics
.wait_max
, delta
);
828 se
->statistics
.wait_count
++;
829 se
->statistics
.wait_sum
+= delta
;
830 se
->statistics
.wait_start
= 0;
834 * Task is being enqueued - update stats:
837 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
840 * Are we enqueueing a waiting task? (for current tasks
841 * a dequeue/enqueue event is a NOP)
843 if (se
!= cfs_rq
->curr
)
844 update_stats_wait_start(cfs_rq
, se
);
848 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
851 * Mark the end of the wait period if dequeueing a
854 if (se
!= cfs_rq
->curr
)
855 update_stats_wait_end(cfs_rq
, se
);
857 if (flags
& DEQUEUE_SLEEP
) {
858 if (entity_is_task(se
)) {
859 struct task_struct
*tsk
= task_of(se
);
861 if (tsk
->state
& TASK_INTERRUPTIBLE
)
862 se
->statistics
.sleep_start
= rq_clock(rq_of(cfs_rq
));
863 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
864 se
->statistics
.block_start
= rq_clock(rq_of(cfs_rq
));
871 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
876 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
881 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
886 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
892 * We are picking a new current task - update its stats:
895 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
898 * We are starting a new run period:
900 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
903 /**************************************************
904 * Scheduling class queueing methods:
907 #ifdef CONFIG_NUMA_BALANCING
909 * Approximate time to scan a full NUMA task in ms. The task scan period is
910 * calculated based on the tasks virtual memory size and
911 * numa_balancing_scan_size.
913 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
914 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
916 /* Portion of address space to scan in MB */
917 unsigned int sysctl_numa_balancing_scan_size
= 256;
919 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
920 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
922 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
924 unsigned long rss
= 0;
925 unsigned long nr_scan_pages
;
928 * Calculations based on RSS as non-present and empty pages are skipped
929 * by the PTE scanner and NUMA hinting faults should be trapped based
932 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
933 rss
= get_mm_rss(p
->mm
);
937 rss
= round_up(rss
, nr_scan_pages
);
938 return rss
/ nr_scan_pages
;
941 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
942 #define MAX_SCAN_WINDOW 2560
944 static unsigned int task_scan_min(struct task_struct
*p
)
946 unsigned int scan_size
= READ_ONCE(sysctl_numa_balancing_scan_size
);
947 unsigned int scan
, floor
;
948 unsigned int windows
= 1;
950 if (scan_size
< MAX_SCAN_WINDOW
)
951 windows
= MAX_SCAN_WINDOW
/ scan_size
;
952 floor
= 1000 / windows
;
954 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
955 return max_t(unsigned int, floor
, scan
);
958 static unsigned int task_scan_max(struct task_struct
*p
)
960 unsigned int smin
= task_scan_min(p
);
963 /* Watch for min being lower than max due to floor calculations */
964 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
965 return max(smin
, smax
);
968 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
970 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
971 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
974 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
976 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
977 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
983 spinlock_t lock
; /* nr_tasks, tasks */
989 unsigned long total_faults
;
990 unsigned long max_faults_cpu
;
992 * Faults_cpu is used to decide whether memory should move
993 * towards the CPU. As a consequence, these stats are weighted
994 * more by CPU use than by memory faults.
996 unsigned long *faults_cpu
;
997 unsigned long faults
[0];
1000 /* Shared or private faults. */
1001 #define NR_NUMA_HINT_FAULT_TYPES 2
1003 /* Memory and CPU locality */
1004 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1006 /* Averaged statistics, and temporary buffers. */
1007 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1009 pid_t
task_numa_group_id(struct task_struct
*p
)
1011 return p
->numa_group
? p
->numa_group
->gid
: 0;
1015 * The averaged statistics, shared & private, memory & cpu,
1016 * occupy the first half of the array. The second half of the
1017 * array is for current counters, which are averaged into the
1018 * first set by task_numa_placement.
1020 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
1022 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
1025 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
1027 if (!p
->numa_faults
)
1030 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1031 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1034 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
1039 return p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1040 p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1043 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
1045 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1046 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1050 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1051 * considered part of a numa group's pseudo-interleaving set. Migrations
1052 * between these nodes are slowed down, to allow things to settle down.
1054 #define ACTIVE_NODE_FRACTION 3
1056 static bool numa_is_active_node(int nid
, struct numa_group
*ng
)
1058 return group_faults_cpu(ng
, nid
) * ACTIVE_NODE_FRACTION
> ng
->max_faults_cpu
;
1061 /* Handle placement on systems where not all nodes are directly connected. */
1062 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
1063 int maxdist
, bool task
)
1065 unsigned long score
= 0;
1069 * All nodes are directly connected, and the same distance
1070 * from each other. No need for fancy placement algorithms.
1072 if (sched_numa_topology_type
== NUMA_DIRECT
)
1076 * This code is called for each node, introducing N^2 complexity,
1077 * which should be ok given the number of nodes rarely exceeds 8.
1079 for_each_online_node(node
) {
1080 unsigned long faults
;
1081 int dist
= node_distance(nid
, node
);
1084 * The furthest away nodes in the system are not interesting
1085 * for placement; nid was already counted.
1087 if (dist
== sched_max_numa_distance
|| node
== nid
)
1091 * On systems with a backplane NUMA topology, compare groups
1092 * of nodes, and move tasks towards the group with the most
1093 * memory accesses. When comparing two nodes at distance
1094 * "hoplimit", only nodes closer by than "hoplimit" are part
1095 * of each group. Skip other nodes.
1097 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1101 /* Add up the faults from nearby nodes. */
1103 faults
= task_faults(p
, node
);
1105 faults
= group_faults(p
, node
);
1108 * On systems with a glueless mesh NUMA topology, there are
1109 * no fixed "groups of nodes". Instead, nodes that are not
1110 * directly connected bounce traffic through intermediate
1111 * nodes; a numa_group can occupy any set of nodes.
1112 * The further away a node is, the less the faults count.
1113 * This seems to result in good task placement.
1115 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1116 faults
*= (sched_max_numa_distance
- dist
);
1117 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1127 * These return the fraction of accesses done by a particular task, or
1128 * task group, on a particular numa node. The group weight is given a
1129 * larger multiplier, in order to group tasks together that are almost
1130 * evenly spread out between numa nodes.
1132 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1135 unsigned long faults
, total_faults
;
1137 if (!p
->numa_faults
)
1140 total_faults
= p
->total_numa_faults
;
1145 faults
= task_faults(p
, nid
);
1146 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1148 return 1000 * faults
/ total_faults
;
1151 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1154 unsigned long faults
, total_faults
;
1159 total_faults
= p
->numa_group
->total_faults
;
1164 faults
= group_faults(p
, nid
);
1165 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1167 return 1000 * faults
/ total_faults
;
1170 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1171 int src_nid
, int dst_cpu
)
1173 struct numa_group
*ng
= p
->numa_group
;
1174 int dst_nid
= cpu_to_node(dst_cpu
);
1175 int last_cpupid
, this_cpupid
;
1177 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1180 * Multi-stage node selection is used in conjunction with a periodic
1181 * migration fault to build a temporal task<->page relation. By using
1182 * a two-stage filter we remove short/unlikely relations.
1184 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1185 * a task's usage of a particular page (n_p) per total usage of this
1186 * page (n_t) (in a given time-span) to a probability.
1188 * Our periodic faults will sample this probability and getting the
1189 * same result twice in a row, given these samples are fully
1190 * independent, is then given by P(n)^2, provided our sample period
1191 * is sufficiently short compared to the usage pattern.
1193 * This quadric squishes small probabilities, making it less likely we
1194 * act on an unlikely task<->page relation.
1196 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1197 if (!cpupid_pid_unset(last_cpupid
) &&
1198 cpupid_to_nid(last_cpupid
) != dst_nid
)
1201 /* Always allow migrate on private faults */
1202 if (cpupid_match_pid(p
, last_cpupid
))
1205 /* A shared fault, but p->numa_group has not been set up yet. */
1210 * Destination node is much more heavily used than the source
1211 * node? Allow migration.
1213 if (group_faults_cpu(ng
, dst_nid
) > group_faults_cpu(ng
, src_nid
) *
1214 ACTIVE_NODE_FRACTION
)
1218 * Distribute memory according to CPU & memory use on each node,
1219 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1221 * faults_cpu(dst) 3 faults_cpu(src)
1222 * --------------- * - > ---------------
1223 * faults_mem(dst) 4 faults_mem(src)
1225 return group_faults_cpu(ng
, dst_nid
) * group_faults(p
, src_nid
) * 3 >
1226 group_faults_cpu(ng
, src_nid
) * group_faults(p
, dst_nid
) * 4;
1229 static unsigned long weighted_cpuload(const int cpu
);
1230 static unsigned long source_load(int cpu
, int type
);
1231 static unsigned long target_load(int cpu
, int type
);
1232 static unsigned long capacity_of(int cpu
);
1233 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
);
1235 /* Cached statistics for all CPUs within a node */
1237 unsigned long nr_running
;
1240 /* Total compute capacity of CPUs on a node */
1241 unsigned long compute_capacity
;
1243 /* Approximate capacity in terms of runnable tasks on a node */
1244 unsigned long task_capacity
;
1245 int has_free_capacity
;
1249 * XXX borrowed from update_sg_lb_stats
1251 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1253 int smt
, cpu
, cpus
= 0;
1254 unsigned long capacity
;
1256 memset(ns
, 0, sizeof(*ns
));
1257 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1258 struct rq
*rq
= cpu_rq(cpu
);
1260 ns
->nr_running
+= rq
->nr_running
;
1261 ns
->load
+= weighted_cpuload(cpu
);
1262 ns
->compute_capacity
+= capacity_of(cpu
);
1268 * If we raced with hotplug and there are no CPUs left in our mask
1269 * the @ns structure is NULL'ed and task_numa_compare() will
1270 * not find this node attractive.
1272 * We'll either bail at !has_free_capacity, or we'll detect a huge
1273 * imbalance and bail there.
1278 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1279 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, ns
->compute_capacity
);
1280 capacity
= cpus
/ smt
; /* cores */
1282 ns
->task_capacity
= min_t(unsigned, capacity
,
1283 DIV_ROUND_CLOSEST(ns
->compute_capacity
, SCHED_CAPACITY_SCALE
));
1284 ns
->has_free_capacity
= (ns
->nr_running
< ns
->task_capacity
);
1287 struct task_numa_env
{
1288 struct task_struct
*p
;
1290 int src_cpu
, src_nid
;
1291 int dst_cpu
, dst_nid
;
1293 struct numa_stats src_stats
, dst_stats
;
1298 struct task_struct
*best_task
;
1303 static void task_numa_assign(struct task_numa_env
*env
,
1304 struct task_struct
*p
, long imp
)
1307 put_task_struct(env
->best_task
);
1310 env
->best_imp
= imp
;
1311 env
->best_cpu
= env
->dst_cpu
;
1314 static bool load_too_imbalanced(long src_load
, long dst_load
,
1315 struct task_numa_env
*env
)
1318 long orig_src_load
, orig_dst_load
;
1319 long src_capacity
, dst_capacity
;
1322 * The load is corrected for the CPU capacity available on each node.
1325 * ------------ vs ---------
1326 * src_capacity dst_capacity
1328 src_capacity
= env
->src_stats
.compute_capacity
;
1329 dst_capacity
= env
->dst_stats
.compute_capacity
;
1331 /* We care about the slope of the imbalance, not the direction. */
1332 if (dst_load
< src_load
)
1333 swap(dst_load
, src_load
);
1335 /* Is the difference below the threshold? */
1336 imb
= dst_load
* src_capacity
* 100 -
1337 src_load
* dst_capacity
* env
->imbalance_pct
;
1342 * The imbalance is above the allowed threshold.
1343 * Compare it with the old imbalance.
1345 orig_src_load
= env
->src_stats
.load
;
1346 orig_dst_load
= env
->dst_stats
.load
;
1348 if (orig_dst_load
< orig_src_load
)
1349 swap(orig_dst_load
, orig_src_load
);
1351 old_imb
= orig_dst_load
* src_capacity
* 100 -
1352 orig_src_load
* dst_capacity
* env
->imbalance_pct
;
1354 /* Would this change make things worse? */
1355 return (imb
> old_imb
);
1359 * This checks if the overall compute and NUMA accesses of the system would
1360 * be improved if the source tasks was migrated to the target dst_cpu taking
1361 * into account that it might be best if task running on the dst_cpu should
1362 * be exchanged with the source task
1364 static void task_numa_compare(struct task_numa_env
*env
,
1365 long taskimp
, long groupimp
)
1367 struct rq
*src_rq
= cpu_rq(env
->src_cpu
);
1368 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1369 struct task_struct
*cur
;
1370 long src_load
, dst_load
;
1372 long imp
= env
->p
->numa_group
? groupimp
: taskimp
;
1374 int dist
= env
->dist
;
1375 bool assigned
= false;
1379 raw_spin_lock_irq(&dst_rq
->lock
);
1382 * No need to move the exiting task or idle task.
1384 if ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
))
1388 * The task_struct must be protected here to protect the
1389 * p->numa_faults access in the task_weight since the
1390 * numa_faults could already be freed in the following path:
1391 * finish_task_switch()
1392 * --> put_task_struct()
1393 * --> __put_task_struct()
1394 * --> task_numa_free()
1396 get_task_struct(cur
);
1399 raw_spin_unlock_irq(&dst_rq
->lock
);
1402 * Because we have preemption enabled we can get migrated around and
1403 * end try selecting ourselves (current == env->p) as a swap candidate.
1409 * "imp" is the fault differential for the source task between the
1410 * source and destination node. Calculate the total differential for
1411 * the source task and potential destination task. The more negative
1412 * the value is, the more rmeote accesses that would be expected to
1413 * be incurred if the tasks were swapped.
1416 /* Skip this swap candidate if cannot move to the source cpu */
1417 if (!cpumask_test_cpu(env
->src_cpu
, tsk_cpus_allowed(cur
)))
1421 * If dst and source tasks are in the same NUMA group, or not
1422 * in any group then look only at task weights.
1424 if (cur
->numa_group
== env
->p
->numa_group
) {
1425 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1426 task_weight(cur
, env
->dst_nid
, dist
);
1428 * Add some hysteresis to prevent swapping the
1429 * tasks within a group over tiny differences.
1431 if (cur
->numa_group
)
1435 * Compare the group weights. If a task is all by
1436 * itself (not part of a group), use the task weight
1439 if (cur
->numa_group
)
1440 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1441 group_weight(cur
, env
->dst_nid
, dist
);
1443 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1444 task_weight(cur
, env
->dst_nid
, dist
);
1448 if (imp
<= env
->best_imp
&& moveimp
<= env
->best_imp
)
1452 /* Is there capacity at our destination? */
1453 if (env
->src_stats
.nr_running
<= env
->src_stats
.task_capacity
&&
1454 !env
->dst_stats
.has_free_capacity
)
1460 /* Balance doesn't matter much if we're running a task per cpu */
1461 if (imp
> env
->best_imp
&& src_rq
->nr_running
== 1 &&
1462 dst_rq
->nr_running
== 1)
1466 * In the overloaded case, try and keep the load balanced.
1469 load
= task_h_load(env
->p
);
1470 dst_load
= env
->dst_stats
.load
+ load
;
1471 src_load
= env
->src_stats
.load
- load
;
1473 if (moveimp
> imp
&& moveimp
> env
->best_imp
) {
1475 * If the improvement from just moving env->p direction is
1476 * better than swapping tasks around, check if a move is
1477 * possible. Store a slightly smaller score than moveimp,
1478 * so an actually idle CPU will win.
1480 if (!load_too_imbalanced(src_load
, dst_load
, env
)) {
1482 put_task_struct(cur
);
1488 if (imp
<= env
->best_imp
)
1492 load
= task_h_load(cur
);
1497 if (load_too_imbalanced(src_load
, dst_load
, env
))
1501 * One idle CPU per node is evaluated for a task numa move.
1502 * Call select_idle_sibling to maybe find a better one.
1505 env
->dst_cpu
= select_idle_sibling(env
->p
, env
->dst_cpu
);
1509 task_numa_assign(env
, cur
, imp
);
1513 * The dst_rq->curr isn't assigned. The protection for task_struct is
1516 if (cur
&& !assigned
)
1517 put_task_struct(cur
);
1520 static void task_numa_find_cpu(struct task_numa_env
*env
,
1521 long taskimp
, long groupimp
)
1525 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1526 /* Skip this CPU if the source task cannot migrate */
1527 if (!cpumask_test_cpu(cpu
, tsk_cpus_allowed(env
->p
)))
1531 task_numa_compare(env
, taskimp
, groupimp
);
1535 /* Only move tasks to a NUMA node less busy than the current node. */
1536 static bool numa_has_capacity(struct task_numa_env
*env
)
1538 struct numa_stats
*src
= &env
->src_stats
;
1539 struct numa_stats
*dst
= &env
->dst_stats
;
1541 if (src
->has_free_capacity
&& !dst
->has_free_capacity
)
1545 * Only consider a task move if the source has a higher load
1546 * than the destination, corrected for CPU capacity on each node.
1548 * src->load dst->load
1549 * --------------------- vs ---------------------
1550 * src->compute_capacity dst->compute_capacity
1552 if (src
->load
* dst
->compute_capacity
* env
->imbalance_pct
>
1554 dst
->load
* src
->compute_capacity
* 100)
1560 static int task_numa_migrate(struct task_struct
*p
)
1562 struct task_numa_env env
= {
1565 .src_cpu
= task_cpu(p
),
1566 .src_nid
= task_node(p
),
1568 .imbalance_pct
= 112,
1574 struct sched_domain
*sd
;
1575 unsigned long taskweight
, groupweight
;
1577 long taskimp
, groupimp
;
1580 * Pick the lowest SD_NUMA domain, as that would have the smallest
1581 * imbalance and would be the first to start moving tasks about.
1583 * And we want to avoid any moving of tasks about, as that would create
1584 * random movement of tasks -- counter the numa conditions we're trying
1588 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1590 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1594 * Cpusets can break the scheduler domain tree into smaller
1595 * balance domains, some of which do not cross NUMA boundaries.
1596 * Tasks that are "trapped" in such domains cannot be migrated
1597 * elsewhere, so there is no point in (re)trying.
1599 if (unlikely(!sd
)) {
1600 p
->numa_preferred_nid
= task_node(p
);
1604 env
.dst_nid
= p
->numa_preferred_nid
;
1605 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1606 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1607 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1608 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1609 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
1610 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
1611 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1613 /* Try to find a spot on the preferred nid. */
1614 if (numa_has_capacity(&env
))
1615 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1618 * Look at other nodes in these cases:
1619 * - there is no space available on the preferred_nid
1620 * - the task is part of a numa_group that is interleaved across
1621 * multiple NUMA nodes; in order to better consolidate the group,
1622 * we need to check other locations.
1624 if (env
.best_cpu
== -1 || (p
->numa_group
&& p
->numa_group
->active_nodes
> 1)) {
1625 for_each_online_node(nid
) {
1626 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1629 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1630 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1632 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1633 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1636 /* Only consider nodes where both task and groups benefit */
1637 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
1638 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
1639 if (taskimp
< 0 && groupimp
< 0)
1644 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1645 if (numa_has_capacity(&env
))
1646 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1651 * If the task is part of a workload that spans multiple NUMA nodes,
1652 * and is migrating into one of the workload's active nodes, remember
1653 * this node as the task's preferred numa node, so the workload can
1655 * A task that migrated to a second choice node will be better off
1656 * trying for a better one later. Do not set the preferred node here.
1658 if (p
->numa_group
) {
1659 struct numa_group
*ng
= p
->numa_group
;
1661 if (env
.best_cpu
== -1)
1666 if (ng
->active_nodes
> 1 && numa_is_active_node(env
.dst_nid
, ng
))
1667 sched_setnuma(p
, env
.dst_nid
);
1670 /* No better CPU than the current one was found. */
1671 if (env
.best_cpu
== -1)
1675 * Reset the scan period if the task is being rescheduled on an
1676 * alternative node to recheck if the tasks is now properly placed.
1678 p
->numa_scan_period
= task_scan_min(p
);
1680 if (env
.best_task
== NULL
) {
1681 ret
= migrate_task_to(p
, env
.best_cpu
);
1683 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1687 ret
= migrate_swap(p
, env
.best_task
);
1689 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1690 put_task_struct(env
.best_task
);
1694 /* Attempt to migrate a task to a CPU on the preferred node. */
1695 static void numa_migrate_preferred(struct task_struct
*p
)
1697 unsigned long interval
= HZ
;
1699 /* This task has no NUMA fault statistics yet */
1700 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults
))
1703 /* Periodically retry migrating the task to the preferred node */
1704 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
1705 p
->numa_migrate_retry
= jiffies
+ interval
;
1707 /* Success if task is already running on preferred CPU */
1708 if (task_node(p
) == p
->numa_preferred_nid
)
1711 /* Otherwise, try migrate to a CPU on the preferred node */
1712 task_numa_migrate(p
);
1716 * Find out how many nodes on the workload is actively running on. Do this by
1717 * tracking the nodes from which NUMA hinting faults are triggered. This can
1718 * be different from the set of nodes where the workload's memory is currently
1721 static void numa_group_count_active_nodes(struct numa_group
*numa_group
)
1723 unsigned long faults
, max_faults
= 0;
1724 int nid
, active_nodes
= 0;
1726 for_each_online_node(nid
) {
1727 faults
= group_faults_cpu(numa_group
, nid
);
1728 if (faults
> max_faults
)
1729 max_faults
= faults
;
1732 for_each_online_node(nid
) {
1733 faults
= group_faults_cpu(numa_group
, nid
);
1734 if (faults
* ACTIVE_NODE_FRACTION
> max_faults
)
1738 numa_group
->max_faults_cpu
= max_faults
;
1739 numa_group
->active_nodes
= active_nodes
;
1743 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1744 * increments. The more local the fault statistics are, the higher the scan
1745 * period will be for the next scan window. If local/(local+remote) ratio is
1746 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1747 * the scan period will decrease. Aim for 70% local accesses.
1749 #define NUMA_PERIOD_SLOTS 10
1750 #define NUMA_PERIOD_THRESHOLD 7
1753 * Increase the scan period (slow down scanning) if the majority of
1754 * our memory is already on our local node, or if the majority of
1755 * the page accesses are shared with other processes.
1756 * Otherwise, decrease the scan period.
1758 static void update_task_scan_period(struct task_struct
*p
,
1759 unsigned long shared
, unsigned long private)
1761 unsigned int period_slot
;
1765 unsigned long remote
= p
->numa_faults_locality
[0];
1766 unsigned long local
= p
->numa_faults_locality
[1];
1769 * If there were no record hinting faults then either the task is
1770 * completely idle or all activity is areas that are not of interest
1771 * to automatic numa balancing. Related to that, if there were failed
1772 * migration then it implies we are migrating too quickly or the local
1773 * node is overloaded. In either case, scan slower
1775 if (local
+ shared
== 0 || p
->numa_faults_locality
[2]) {
1776 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1777 p
->numa_scan_period
<< 1);
1779 p
->mm
->numa_next_scan
= jiffies
+
1780 msecs_to_jiffies(p
->numa_scan_period
);
1786 * Prepare to scale scan period relative to the current period.
1787 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1788 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1789 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1791 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1792 ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1793 if (ratio
>= NUMA_PERIOD_THRESHOLD
) {
1794 int slot
= ratio
- NUMA_PERIOD_THRESHOLD
;
1797 diff
= slot
* period_slot
;
1799 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
1802 * Scale scan rate increases based on sharing. There is an
1803 * inverse relationship between the degree of sharing and
1804 * the adjustment made to the scanning period. Broadly
1805 * speaking the intent is that there is little point
1806 * scanning faster if shared accesses dominate as it may
1807 * simply bounce migrations uselessly
1809 ratio
= DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS
, (private + shared
+ 1));
1810 diff
= (diff
* ratio
) / NUMA_PERIOD_SLOTS
;
1813 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
1814 task_scan_min(p
), task_scan_max(p
));
1815 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1819 * Get the fraction of time the task has been running since the last
1820 * NUMA placement cycle. The scheduler keeps similar statistics, but
1821 * decays those on a 32ms period, which is orders of magnitude off
1822 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1823 * stats only if the task is so new there are no NUMA statistics yet.
1825 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
1827 u64 runtime
, delta
, now
;
1828 /* Use the start of this time slice to avoid calculations. */
1829 now
= p
->se
.exec_start
;
1830 runtime
= p
->se
.sum_exec_runtime
;
1832 if (p
->last_task_numa_placement
) {
1833 delta
= runtime
- p
->last_sum_exec_runtime
;
1834 *period
= now
- p
->last_task_numa_placement
;
1836 delta
= p
->se
.avg
.load_sum
/ p
->se
.load
.weight
;
1837 *period
= LOAD_AVG_MAX
;
1840 p
->last_sum_exec_runtime
= runtime
;
1841 p
->last_task_numa_placement
= now
;
1847 * Determine the preferred nid for a task in a numa_group. This needs to
1848 * be done in a way that produces consistent results with group_weight,
1849 * otherwise workloads might not converge.
1851 static int preferred_group_nid(struct task_struct
*p
, int nid
)
1856 /* Direct connections between all NUMA nodes. */
1857 if (sched_numa_topology_type
== NUMA_DIRECT
)
1861 * On a system with glueless mesh NUMA topology, group_weight
1862 * scores nodes according to the number of NUMA hinting faults on
1863 * both the node itself, and on nearby nodes.
1865 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1866 unsigned long score
, max_score
= 0;
1867 int node
, max_node
= nid
;
1869 dist
= sched_max_numa_distance
;
1871 for_each_online_node(node
) {
1872 score
= group_weight(p
, node
, dist
);
1873 if (score
> max_score
) {
1882 * Finding the preferred nid in a system with NUMA backplane
1883 * interconnect topology is more involved. The goal is to locate
1884 * tasks from numa_groups near each other in the system, and
1885 * untangle workloads from different sides of the system. This requires
1886 * searching down the hierarchy of node groups, recursively searching
1887 * inside the highest scoring group of nodes. The nodemask tricks
1888 * keep the complexity of the search down.
1890 nodes
= node_online_map
;
1891 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
1892 unsigned long max_faults
= 0;
1893 nodemask_t max_group
= NODE_MASK_NONE
;
1896 /* Are there nodes at this distance from each other? */
1897 if (!find_numa_distance(dist
))
1900 for_each_node_mask(a
, nodes
) {
1901 unsigned long faults
= 0;
1902 nodemask_t this_group
;
1903 nodes_clear(this_group
);
1905 /* Sum group's NUMA faults; includes a==b case. */
1906 for_each_node_mask(b
, nodes
) {
1907 if (node_distance(a
, b
) < dist
) {
1908 faults
+= group_faults(p
, b
);
1909 node_set(b
, this_group
);
1910 node_clear(b
, nodes
);
1914 /* Remember the top group. */
1915 if (faults
> max_faults
) {
1916 max_faults
= faults
;
1917 max_group
= this_group
;
1919 * subtle: at the smallest distance there is
1920 * just one node left in each "group", the
1921 * winner is the preferred nid.
1926 /* Next round, evaluate the nodes within max_group. */
1934 static void task_numa_placement(struct task_struct
*p
)
1936 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
1937 unsigned long max_faults
= 0, max_group_faults
= 0;
1938 unsigned long fault_types
[2] = { 0, 0 };
1939 unsigned long total_faults
;
1940 u64 runtime
, period
;
1941 spinlock_t
*group_lock
= NULL
;
1944 * The p->mm->numa_scan_seq field gets updated without
1945 * exclusive access. Use READ_ONCE() here to ensure
1946 * that the field is read in a single access:
1948 seq
= READ_ONCE(p
->mm
->numa_scan_seq
);
1949 if (p
->numa_scan_seq
== seq
)
1951 p
->numa_scan_seq
= seq
;
1952 p
->numa_scan_period_max
= task_scan_max(p
);
1954 total_faults
= p
->numa_faults_locality
[0] +
1955 p
->numa_faults_locality
[1];
1956 runtime
= numa_get_avg_runtime(p
, &period
);
1958 /* If the task is part of a group prevent parallel updates to group stats */
1959 if (p
->numa_group
) {
1960 group_lock
= &p
->numa_group
->lock
;
1961 spin_lock_irq(group_lock
);
1964 /* Find the node with the highest number of faults */
1965 for_each_online_node(nid
) {
1966 /* Keep track of the offsets in numa_faults array */
1967 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
1968 unsigned long faults
= 0, group_faults
= 0;
1971 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
1972 long diff
, f_diff
, f_weight
;
1974 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
1975 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
1976 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
1977 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
1979 /* Decay existing window, copy faults since last scan */
1980 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
1981 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
1982 p
->numa_faults
[membuf_idx
] = 0;
1985 * Normalize the faults_from, so all tasks in a group
1986 * count according to CPU use, instead of by the raw
1987 * number of faults. Tasks with little runtime have
1988 * little over-all impact on throughput, and thus their
1989 * faults are less important.
1991 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
1992 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
1994 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
1995 p
->numa_faults
[cpubuf_idx
] = 0;
1997 p
->numa_faults
[mem_idx
] += diff
;
1998 p
->numa_faults
[cpu_idx
] += f_diff
;
1999 faults
+= p
->numa_faults
[mem_idx
];
2000 p
->total_numa_faults
+= diff
;
2001 if (p
->numa_group
) {
2003 * safe because we can only change our own group
2005 * mem_idx represents the offset for a given
2006 * nid and priv in a specific region because it
2007 * is at the beginning of the numa_faults array.
2009 p
->numa_group
->faults
[mem_idx
] += diff
;
2010 p
->numa_group
->faults_cpu
[mem_idx
] += f_diff
;
2011 p
->numa_group
->total_faults
+= diff
;
2012 group_faults
+= p
->numa_group
->faults
[mem_idx
];
2016 if (faults
> max_faults
) {
2017 max_faults
= faults
;
2021 if (group_faults
> max_group_faults
) {
2022 max_group_faults
= group_faults
;
2023 max_group_nid
= nid
;
2027 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
2029 if (p
->numa_group
) {
2030 numa_group_count_active_nodes(p
->numa_group
);
2031 spin_unlock_irq(group_lock
);
2032 max_nid
= preferred_group_nid(p
, max_group_nid
);
2036 /* Set the new preferred node */
2037 if (max_nid
!= p
->numa_preferred_nid
)
2038 sched_setnuma(p
, max_nid
);
2040 if (task_node(p
) != p
->numa_preferred_nid
)
2041 numa_migrate_preferred(p
);
2045 static inline int get_numa_group(struct numa_group
*grp
)
2047 return atomic_inc_not_zero(&grp
->refcount
);
2050 static inline void put_numa_group(struct numa_group
*grp
)
2052 if (atomic_dec_and_test(&grp
->refcount
))
2053 kfree_rcu(grp
, rcu
);
2056 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
2059 struct numa_group
*grp
, *my_grp
;
2060 struct task_struct
*tsk
;
2062 int cpu
= cpupid_to_cpu(cpupid
);
2065 if (unlikely(!p
->numa_group
)) {
2066 unsigned int size
= sizeof(struct numa_group
) +
2067 4*nr_node_ids
*sizeof(unsigned long);
2069 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
2073 atomic_set(&grp
->refcount
, 1);
2074 grp
->active_nodes
= 1;
2075 grp
->max_faults_cpu
= 0;
2076 spin_lock_init(&grp
->lock
);
2078 /* Second half of the array tracks nids where faults happen */
2079 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
2082 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2083 grp
->faults
[i
] = p
->numa_faults
[i
];
2085 grp
->total_faults
= p
->total_numa_faults
;
2088 rcu_assign_pointer(p
->numa_group
, grp
);
2092 tsk
= READ_ONCE(cpu_rq(cpu
)->curr
);
2094 if (!cpupid_match_pid(tsk
, cpupid
))
2097 grp
= rcu_dereference(tsk
->numa_group
);
2101 my_grp
= p
->numa_group
;
2106 * Only join the other group if its bigger; if we're the bigger group,
2107 * the other task will join us.
2109 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
2113 * Tie-break on the grp address.
2115 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
2118 /* Always join threads in the same process. */
2119 if (tsk
->mm
== current
->mm
)
2122 /* Simple filter to avoid false positives due to PID collisions */
2123 if (flags
& TNF_SHARED
)
2126 /* Update priv based on whether false sharing was detected */
2129 if (join
&& !get_numa_group(grp
))
2137 BUG_ON(irqs_disabled());
2138 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
2140 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
2141 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
2142 grp
->faults
[i
] += p
->numa_faults
[i
];
2144 my_grp
->total_faults
-= p
->total_numa_faults
;
2145 grp
->total_faults
+= p
->total_numa_faults
;
2150 spin_unlock(&my_grp
->lock
);
2151 spin_unlock_irq(&grp
->lock
);
2153 rcu_assign_pointer(p
->numa_group
, grp
);
2155 put_numa_group(my_grp
);
2163 void task_numa_free(struct task_struct
*p
)
2165 struct numa_group
*grp
= p
->numa_group
;
2166 void *numa_faults
= p
->numa_faults
;
2167 unsigned long flags
;
2171 spin_lock_irqsave(&grp
->lock
, flags
);
2172 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2173 grp
->faults
[i
] -= p
->numa_faults
[i
];
2174 grp
->total_faults
-= p
->total_numa_faults
;
2177 spin_unlock_irqrestore(&grp
->lock
, flags
);
2178 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2179 put_numa_group(grp
);
2182 p
->numa_faults
= NULL
;
2187 * Got a PROT_NONE fault for a page on @node.
2189 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2191 struct task_struct
*p
= current
;
2192 bool migrated
= flags
& TNF_MIGRATED
;
2193 int cpu_node
= task_node(current
);
2194 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2195 struct numa_group
*ng
;
2198 if (!static_branch_likely(&sched_numa_balancing
))
2201 /* for example, ksmd faulting in a user's mm */
2205 /* Allocate buffer to track faults on a per-node basis */
2206 if (unlikely(!p
->numa_faults
)) {
2207 int size
= sizeof(*p
->numa_faults
) *
2208 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2210 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2211 if (!p
->numa_faults
)
2214 p
->total_numa_faults
= 0;
2215 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2219 * First accesses are treated as private, otherwise consider accesses
2220 * to be private if the accessing pid has not changed
2222 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2225 priv
= cpupid_match_pid(p
, last_cpupid
);
2226 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2227 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2231 * If a workload spans multiple NUMA nodes, a shared fault that
2232 * occurs wholly within the set of nodes that the workload is
2233 * actively using should be counted as local. This allows the
2234 * scan rate to slow down when a workload has settled down.
2237 if (!priv
&& !local
&& ng
&& ng
->active_nodes
> 1 &&
2238 numa_is_active_node(cpu_node
, ng
) &&
2239 numa_is_active_node(mem_node
, ng
))
2242 task_numa_placement(p
);
2245 * Retry task to preferred node migration periodically, in case it
2246 * case it previously failed, or the scheduler moved us.
2248 if (time_after(jiffies
, p
->numa_migrate_retry
))
2249 numa_migrate_preferred(p
);
2252 p
->numa_pages_migrated
+= pages
;
2253 if (flags
& TNF_MIGRATE_FAIL
)
2254 p
->numa_faults_locality
[2] += pages
;
2256 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2257 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2258 p
->numa_faults_locality
[local
] += pages
;
2261 static void reset_ptenuma_scan(struct task_struct
*p
)
2264 * We only did a read acquisition of the mmap sem, so
2265 * p->mm->numa_scan_seq is written to without exclusive access
2266 * and the update is not guaranteed to be atomic. That's not
2267 * much of an issue though, since this is just used for
2268 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2269 * expensive, to avoid any form of compiler optimizations:
2271 WRITE_ONCE(p
->mm
->numa_scan_seq
, READ_ONCE(p
->mm
->numa_scan_seq
) + 1);
2272 p
->mm
->numa_scan_offset
= 0;
2276 * The expensive part of numa migration is done from task_work context.
2277 * Triggered from task_tick_numa().
2279 void task_numa_work(struct callback_head
*work
)
2281 unsigned long migrate
, next_scan
, now
= jiffies
;
2282 struct task_struct
*p
= current
;
2283 struct mm_struct
*mm
= p
->mm
;
2284 u64 runtime
= p
->se
.sum_exec_runtime
;
2285 struct vm_area_struct
*vma
;
2286 unsigned long start
, end
;
2287 unsigned long nr_pte_updates
= 0;
2288 long pages
, virtpages
;
2290 WARN_ON_ONCE(p
!= container_of(work
, struct task_struct
, numa_work
));
2292 work
->next
= work
; /* protect against double add */
2294 * Who cares about NUMA placement when they're dying.
2296 * NOTE: make sure not to dereference p->mm before this check,
2297 * exit_task_work() happens _after_ exit_mm() so we could be called
2298 * without p->mm even though we still had it when we enqueued this
2301 if (p
->flags
& PF_EXITING
)
2304 if (!mm
->numa_next_scan
) {
2305 mm
->numa_next_scan
= now
+
2306 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2310 * Enforce maximal scan/migration frequency..
2312 migrate
= mm
->numa_next_scan
;
2313 if (time_before(now
, migrate
))
2316 if (p
->numa_scan_period
== 0) {
2317 p
->numa_scan_period_max
= task_scan_max(p
);
2318 p
->numa_scan_period
= task_scan_min(p
);
2321 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2322 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2326 * Delay this task enough that another task of this mm will likely win
2327 * the next time around.
2329 p
->node_stamp
+= 2 * TICK_NSEC
;
2331 start
= mm
->numa_scan_offset
;
2332 pages
= sysctl_numa_balancing_scan_size
;
2333 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2334 virtpages
= pages
* 8; /* Scan up to this much virtual space */
2339 down_read(&mm
->mmap_sem
);
2340 vma
= find_vma(mm
, start
);
2342 reset_ptenuma_scan(p
);
2346 for (; vma
; vma
= vma
->vm_next
) {
2347 if (!vma_migratable(vma
) || !vma_policy_mof(vma
) ||
2348 is_vm_hugetlb_page(vma
) || (vma
->vm_flags
& VM_MIXEDMAP
)) {
2353 * Shared library pages mapped by multiple processes are not
2354 * migrated as it is expected they are cache replicated. Avoid
2355 * hinting faults in read-only file-backed mappings or the vdso
2356 * as migrating the pages will be of marginal benefit.
2359 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2363 * Skip inaccessible VMAs to avoid any confusion between
2364 * PROT_NONE and NUMA hinting ptes
2366 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
2370 start
= max(start
, vma
->vm_start
);
2371 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2372 end
= min(end
, vma
->vm_end
);
2373 nr_pte_updates
= change_prot_numa(vma
, start
, end
);
2376 * Try to scan sysctl_numa_balancing_size worth of
2377 * hpages that have at least one present PTE that
2378 * is not already pte-numa. If the VMA contains
2379 * areas that are unused or already full of prot_numa
2380 * PTEs, scan up to virtpages, to skip through those
2384 pages
-= (end
- start
) >> PAGE_SHIFT
;
2385 virtpages
-= (end
- start
) >> PAGE_SHIFT
;
2388 if (pages
<= 0 || virtpages
<= 0)
2392 } while (end
!= vma
->vm_end
);
2397 * It is possible to reach the end of the VMA list but the last few
2398 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2399 * would find the !migratable VMA on the next scan but not reset the
2400 * scanner to the start so check it now.
2403 mm
->numa_scan_offset
= start
;
2405 reset_ptenuma_scan(p
);
2406 up_read(&mm
->mmap_sem
);
2409 * Make sure tasks use at least 32x as much time to run other code
2410 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2411 * Usually update_task_scan_period slows down scanning enough; on an
2412 * overloaded system we need to limit overhead on a per task basis.
2414 if (unlikely(p
->se
.sum_exec_runtime
!= runtime
)) {
2415 u64 diff
= p
->se
.sum_exec_runtime
- runtime
;
2416 p
->node_stamp
+= 32 * diff
;
2421 * Drive the periodic memory faults..
2423 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2425 struct callback_head
*work
= &curr
->numa_work
;
2429 * We don't care about NUMA placement if we don't have memory.
2431 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
2435 * Using runtime rather than walltime has the dual advantage that
2436 * we (mostly) drive the selection from busy threads and that the
2437 * task needs to have done some actual work before we bother with
2440 now
= curr
->se
.sum_exec_runtime
;
2441 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2443 if (now
> curr
->node_stamp
+ period
) {
2444 if (!curr
->node_stamp
)
2445 curr
->numa_scan_period
= task_scan_min(curr
);
2446 curr
->node_stamp
+= period
;
2448 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
2449 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
2450 task_work_add(curr
, work
, true);
2455 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2459 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2463 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2466 #endif /* CONFIG_NUMA_BALANCING */
2469 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2471 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
2472 if (!parent_entity(se
))
2473 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2475 if (entity_is_task(se
)) {
2476 struct rq
*rq
= rq_of(cfs_rq
);
2478 account_numa_enqueue(rq
, task_of(se
));
2479 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2482 cfs_rq
->nr_running
++;
2486 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2488 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2489 if (!parent_entity(se
))
2490 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2492 if (entity_is_task(se
)) {
2493 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2494 list_del_init(&se
->group_node
);
2497 cfs_rq
->nr_running
--;
2500 #ifdef CONFIG_FAIR_GROUP_SCHED
2502 static inline long calc_tg_weight(struct task_group
*tg
, struct cfs_rq
*cfs_rq
)
2507 * Use this CPU's real-time load instead of the last load contribution
2508 * as the updating of the contribution is delayed, and we will use the
2509 * the real-time load to calc the share. See update_tg_load_avg().
2511 tg_weight
= atomic_long_read(&tg
->load_avg
);
2512 tg_weight
-= cfs_rq
->tg_load_avg_contrib
;
2513 tg_weight
+= cfs_rq
->load
.weight
;
2518 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2520 long tg_weight
, load
, shares
;
2522 tg_weight
= calc_tg_weight(tg
, cfs_rq
);
2523 load
= cfs_rq
->load
.weight
;
2525 shares
= (tg
->shares
* load
);
2527 shares
/= tg_weight
;
2529 if (shares
< MIN_SHARES
)
2530 shares
= MIN_SHARES
;
2531 if (shares
> tg
->shares
)
2532 shares
= tg
->shares
;
2536 # else /* CONFIG_SMP */
2537 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2541 # endif /* CONFIG_SMP */
2542 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2543 unsigned long weight
)
2546 /* commit outstanding execution time */
2547 if (cfs_rq
->curr
== se
)
2548 update_curr(cfs_rq
);
2549 account_entity_dequeue(cfs_rq
, se
);
2552 update_load_set(&se
->load
, weight
);
2555 account_entity_enqueue(cfs_rq
, se
);
2558 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2560 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2562 struct task_group
*tg
;
2563 struct sched_entity
*se
;
2567 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
2568 if (!se
|| throttled_hierarchy(cfs_rq
))
2571 if (likely(se
->load
.weight
== tg
->shares
))
2574 shares
= calc_cfs_shares(cfs_rq
, tg
);
2576 reweight_entity(cfs_rq_of(se
), se
, shares
);
2578 #else /* CONFIG_FAIR_GROUP_SCHED */
2579 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2582 #endif /* CONFIG_FAIR_GROUP_SCHED */
2585 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2586 static const u32 runnable_avg_yN_inv
[] = {
2587 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2588 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2589 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2590 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2591 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2592 0x85aac367, 0x82cd8698,
2596 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2597 * over-estimates when re-combining.
2599 static const u32 runnable_avg_yN_sum
[] = {
2600 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2601 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2602 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2606 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
2607 * lower integers. See Documentation/scheduler/sched-avg.txt how these
2610 static const u32 __accumulated_sum_N32
[] = {
2611 0, 23371, 35056, 40899, 43820, 45281,
2612 46011, 46376, 46559, 46650, 46696, 46719,
2617 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2619 static __always_inline u64
decay_load(u64 val
, u64 n
)
2621 unsigned int local_n
;
2625 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2628 /* after bounds checking we can collapse to 32-bit */
2632 * As y^PERIOD = 1/2, we can combine
2633 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2634 * With a look-up table which covers y^n (n<PERIOD)
2636 * To achieve constant time decay_load.
2638 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2639 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2640 local_n
%= LOAD_AVG_PERIOD
;
2643 val
= mul_u64_u32_shr(val
, runnable_avg_yN_inv
[local_n
], 32);
2648 * For updates fully spanning n periods, the contribution to runnable
2649 * average will be: \Sum 1024*y^n
2651 * We can compute this reasonably efficiently by combining:
2652 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2654 static u32
__compute_runnable_contrib(u64 n
)
2658 if (likely(n
<= LOAD_AVG_PERIOD
))
2659 return runnable_avg_yN_sum
[n
];
2660 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2661 return LOAD_AVG_MAX
;
2663 /* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
2664 contrib
= __accumulated_sum_N32
[n
/LOAD_AVG_PERIOD
];
2665 n
%= LOAD_AVG_PERIOD
;
2666 contrib
= decay_load(contrib
, n
);
2667 return contrib
+ runnable_avg_yN_sum
[n
];
2670 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2673 * We can represent the historical contribution to runnable average as the
2674 * coefficients of a geometric series. To do this we sub-divide our runnable
2675 * history into segments of approximately 1ms (1024us); label the segment that
2676 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2678 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2680 * (now) (~1ms ago) (~2ms ago)
2682 * Let u_i denote the fraction of p_i that the entity was runnable.
2684 * We then designate the fractions u_i as our co-efficients, yielding the
2685 * following representation of historical load:
2686 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2688 * We choose y based on the with of a reasonably scheduling period, fixing:
2691 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2692 * approximately half as much as the contribution to load within the last ms
2695 * When a period "rolls over" and we have new u_0`, multiplying the previous
2696 * sum again by y is sufficient to update:
2697 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2698 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2700 static __always_inline
int
2701 __update_load_avg(u64 now
, int cpu
, struct sched_avg
*sa
,
2702 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
2704 u64 delta
, scaled_delta
, periods
;
2706 unsigned int delta_w
, scaled_delta_w
, decayed
= 0;
2707 unsigned long scale_freq
, scale_cpu
;
2709 delta
= now
- sa
->last_update_time
;
2711 * This should only happen when time goes backwards, which it
2712 * unfortunately does during sched clock init when we swap over to TSC.
2714 if ((s64
)delta
< 0) {
2715 sa
->last_update_time
= now
;
2720 * Use 1024ns as the unit of measurement since it's a reasonable
2721 * approximation of 1us and fast to compute.
2726 sa
->last_update_time
= now
;
2728 scale_freq
= arch_scale_freq_capacity(NULL
, cpu
);
2729 scale_cpu
= arch_scale_cpu_capacity(NULL
, cpu
);
2731 /* delta_w is the amount already accumulated against our next period */
2732 delta_w
= sa
->period_contrib
;
2733 if (delta
+ delta_w
>= 1024) {
2736 /* how much left for next period will start over, we don't know yet */
2737 sa
->period_contrib
= 0;
2740 * Now that we know we're crossing a period boundary, figure
2741 * out how much from delta we need to complete the current
2742 * period and accrue it.
2744 delta_w
= 1024 - delta_w
;
2745 scaled_delta_w
= cap_scale(delta_w
, scale_freq
);
2747 sa
->load_sum
+= weight
* scaled_delta_w
;
2749 cfs_rq
->runnable_load_sum
+=
2750 weight
* scaled_delta_w
;
2754 sa
->util_sum
+= scaled_delta_w
* scale_cpu
;
2758 /* Figure out how many additional periods this update spans */
2759 periods
= delta
/ 1024;
2762 sa
->load_sum
= decay_load(sa
->load_sum
, periods
+ 1);
2764 cfs_rq
->runnable_load_sum
=
2765 decay_load(cfs_rq
->runnable_load_sum
, periods
+ 1);
2767 sa
->util_sum
= decay_load((u64
)(sa
->util_sum
), periods
+ 1);
2769 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2770 contrib
= __compute_runnable_contrib(periods
);
2771 contrib
= cap_scale(contrib
, scale_freq
);
2773 sa
->load_sum
+= weight
* contrib
;
2775 cfs_rq
->runnable_load_sum
+= weight
* contrib
;
2778 sa
->util_sum
+= contrib
* scale_cpu
;
2781 /* Remainder of delta accrued against u_0` */
2782 scaled_delta
= cap_scale(delta
, scale_freq
);
2784 sa
->load_sum
+= weight
* scaled_delta
;
2786 cfs_rq
->runnable_load_sum
+= weight
* scaled_delta
;
2789 sa
->util_sum
+= scaled_delta
* scale_cpu
;
2791 sa
->period_contrib
+= delta
;
2794 sa
->load_avg
= div_u64(sa
->load_sum
, LOAD_AVG_MAX
);
2796 cfs_rq
->runnable_load_avg
=
2797 div_u64(cfs_rq
->runnable_load_sum
, LOAD_AVG_MAX
);
2799 sa
->util_avg
= sa
->util_sum
/ LOAD_AVG_MAX
;
2805 #ifdef CONFIG_FAIR_GROUP_SCHED
2807 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2808 * and effective_load (which is not done because it is too costly).
2810 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
2812 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
2815 * No need to update load_avg for root_task_group as it is not used.
2817 if (cfs_rq
->tg
== &root_task_group
)
2820 if (force
|| abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
2821 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
2822 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
2827 * Called within set_task_rq() right before setting a task's cpu. The
2828 * caller only guarantees p->pi_lock is held; no other assumptions,
2829 * including the state of rq->lock, should be made.
2831 void set_task_rq_fair(struct sched_entity
*se
,
2832 struct cfs_rq
*prev
, struct cfs_rq
*next
)
2834 if (!sched_feat(ATTACH_AGE_LOAD
))
2838 * We are supposed to update the task to "current" time, then its up to
2839 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2840 * getting what current time is, so simply throw away the out-of-date
2841 * time. This will result in the wakee task is less decayed, but giving
2842 * the wakee more load sounds not bad.
2844 if (se
->avg
.last_update_time
&& prev
) {
2845 u64 p_last_update_time
;
2846 u64 n_last_update_time
;
2848 #ifndef CONFIG_64BIT
2849 u64 p_last_update_time_copy
;
2850 u64 n_last_update_time_copy
;
2853 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
2854 n_last_update_time_copy
= next
->load_last_update_time_copy
;
2858 p_last_update_time
= prev
->avg
.last_update_time
;
2859 n_last_update_time
= next
->avg
.last_update_time
;
2861 } while (p_last_update_time
!= p_last_update_time_copy
||
2862 n_last_update_time
!= n_last_update_time_copy
);
2864 p_last_update_time
= prev
->avg
.last_update_time
;
2865 n_last_update_time
= next
->avg
.last_update_time
;
2867 __update_load_avg(p_last_update_time
, cpu_of(rq_of(prev
)),
2868 &se
->avg
, 0, 0, NULL
);
2869 se
->avg
.last_update_time
= n_last_update_time
;
2872 #else /* CONFIG_FAIR_GROUP_SCHED */
2873 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
) {}
2874 #endif /* CONFIG_FAIR_GROUP_SCHED */
2876 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
2878 static inline void cfs_rq_util_change(struct cfs_rq
*cfs_rq
)
2880 struct rq
*rq
= rq_of(cfs_rq
);
2881 int cpu
= cpu_of(rq
);
2883 if (cpu
== smp_processor_id() && &rq
->cfs
== cfs_rq
) {
2884 unsigned long max
= rq
->cpu_capacity_orig
;
2887 * There are a few boundary cases this might miss but it should
2888 * get called often enough that that should (hopefully) not be
2889 * a real problem -- added to that it only calls on the local
2890 * CPU, so if we enqueue remotely we'll miss an update, but
2891 * the next tick/schedule should update.
2893 * It will not get called when we go idle, because the idle
2894 * thread is a different class (!fair), nor will the utilization
2895 * number include things like RT tasks.
2897 * As is, the util number is not freq-invariant (we'd have to
2898 * implement arch_scale_freq_capacity() for that).
2902 cpufreq_update_util(rq_clock(rq
),
2903 min(cfs_rq
->avg
.util_avg
, max
), max
);
2908 * Unsigned subtract and clamp on underflow.
2910 * Explicitly do a load-store to ensure the intermediate value never hits
2911 * memory. This allows lockless observations without ever seeing the negative
2914 #define sub_positive(_ptr, _val) do { \
2915 typeof(_ptr) ptr = (_ptr); \
2916 typeof(*ptr) val = (_val); \
2917 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2921 WRITE_ONCE(*ptr, res); \
2924 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2926 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
)
2928 struct sched_avg
*sa
= &cfs_rq
->avg
;
2929 int decayed
, removed_load
= 0, removed_util
= 0;
2931 if (atomic_long_read(&cfs_rq
->removed_load_avg
)) {
2932 s64 r
= atomic_long_xchg(&cfs_rq
->removed_load_avg
, 0);
2933 sub_positive(&sa
->load_avg
, r
);
2934 sub_positive(&sa
->load_sum
, r
* LOAD_AVG_MAX
);
2938 if (atomic_long_read(&cfs_rq
->removed_util_avg
)) {
2939 long r
= atomic_long_xchg(&cfs_rq
->removed_util_avg
, 0);
2940 sub_positive(&sa
->util_avg
, r
);
2941 sub_positive(&sa
->util_sum
, r
* LOAD_AVG_MAX
);
2945 decayed
= __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
2946 scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->curr
!= NULL
, cfs_rq
);
2948 #ifndef CONFIG_64BIT
2950 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
2953 if (update_freq
&& (decayed
|| removed_util
))
2954 cfs_rq_util_change(cfs_rq
);
2956 return decayed
|| removed_load
;
2959 /* Update task and its cfs_rq load average */
2960 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
)
2962 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2963 u64 now
= cfs_rq_clock_task(cfs_rq
);
2964 struct rq
*rq
= rq_of(cfs_rq
);
2965 int cpu
= cpu_of(rq
);
2968 * Track task load average for carrying it to new CPU after migrated, and
2969 * track group sched_entity load average for task_h_load calc in migration
2971 __update_load_avg(now
, cpu
, &se
->avg
,
2972 se
->on_rq
* scale_load_down(se
->load
.weight
),
2973 cfs_rq
->curr
== se
, NULL
);
2975 if (update_cfs_rq_load_avg(now
, cfs_rq
, true) && update_tg
)
2976 update_tg_load_avg(cfs_rq
, 0);
2979 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2981 if (!sched_feat(ATTACH_AGE_LOAD
))
2985 * If we got migrated (either between CPUs or between cgroups) we'll
2986 * have aged the average right before clearing @last_update_time.
2988 if (se
->avg
.last_update_time
) {
2989 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2990 &se
->avg
, 0, 0, NULL
);
2993 * XXX: we could have just aged the entire load away if we've been
2994 * absent from the fair class for too long.
2999 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
3000 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
3001 cfs_rq
->avg
.load_sum
+= se
->avg
.load_sum
;
3002 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
3003 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
3005 cfs_rq_util_change(cfs_rq
);
3008 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3010 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
3011 &se
->avg
, se
->on_rq
* scale_load_down(se
->load
.weight
),
3012 cfs_rq
->curr
== se
, NULL
);
3014 sub_positive(&cfs_rq
->avg
.load_avg
, se
->avg
.load_avg
);
3015 sub_positive(&cfs_rq
->avg
.load_sum
, se
->avg
.load_sum
);
3016 sub_positive(&cfs_rq
->avg
.util_avg
, se
->avg
.util_avg
);
3017 sub_positive(&cfs_rq
->avg
.util_sum
, se
->avg
.util_sum
);
3019 cfs_rq_util_change(cfs_rq
);
3022 /* Add the load generated by se into cfs_rq's load average */
3024 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3026 struct sched_avg
*sa
= &se
->avg
;
3027 u64 now
= cfs_rq_clock_task(cfs_rq
);
3028 int migrated
, decayed
;
3030 migrated
= !sa
->last_update_time
;
3032 __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
3033 se
->on_rq
* scale_load_down(se
->load
.weight
),
3034 cfs_rq
->curr
== se
, NULL
);
3037 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
, !migrated
);
3039 cfs_rq
->runnable_load_avg
+= sa
->load_avg
;
3040 cfs_rq
->runnable_load_sum
+= sa
->load_sum
;
3043 attach_entity_load_avg(cfs_rq
, se
);
3045 if (decayed
|| migrated
)
3046 update_tg_load_avg(cfs_rq
, 0);
3049 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3051 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3053 update_load_avg(se
, 1);
3055 cfs_rq
->runnable_load_avg
=
3056 max_t(long, cfs_rq
->runnable_load_avg
- se
->avg
.load_avg
, 0);
3057 cfs_rq
->runnable_load_sum
=
3058 max_t(s64
, cfs_rq
->runnable_load_sum
- se
->avg
.load_sum
, 0);
3061 #ifndef CONFIG_64BIT
3062 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3064 u64 last_update_time_copy
;
3065 u64 last_update_time
;
3068 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3070 last_update_time
= cfs_rq
->avg
.last_update_time
;
3071 } while (last_update_time
!= last_update_time_copy
);
3073 return last_update_time
;
3076 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3078 return cfs_rq
->avg
.last_update_time
;
3083 * Task first catches up with cfs_rq, and then subtract
3084 * itself from the cfs_rq (task must be off the queue now).
3086 void remove_entity_load_avg(struct sched_entity
*se
)
3088 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3089 u64 last_update_time
;
3092 * Newly created task or never used group entity should not be removed
3093 * from its (source) cfs_rq
3095 if (se
->avg
.last_update_time
== 0)
3098 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3100 __update_load_avg(last_update_time
, cpu_of(rq_of(cfs_rq
)), &se
->avg
, 0, 0, NULL
);
3101 atomic_long_add(se
->avg
.load_avg
, &cfs_rq
->removed_load_avg
);
3102 atomic_long_add(se
->avg
.util_avg
, &cfs_rq
->removed_util_avg
);
3105 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
)
3107 return cfs_rq
->runnable_load_avg
;
3110 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3112 return cfs_rq
->avg
.load_avg
;
3115 static int idle_balance(struct rq
*this_rq
);
3117 #else /* CONFIG_SMP */
3119 static inline void update_load_avg(struct sched_entity
*se
, int not_used
)
3121 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3122 struct rq
*rq
= rq_of(cfs_rq
);
3124 cpufreq_trigger_update(rq_clock(rq
));
3128 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3130 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3131 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
3134 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3136 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3138 static inline int idle_balance(struct rq
*rq
)
3143 #endif /* CONFIG_SMP */
3145 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3147 #ifdef CONFIG_SCHEDSTATS
3148 struct task_struct
*tsk
= NULL
;
3150 if (entity_is_task(se
))
3153 if (se
->statistics
.sleep_start
) {
3154 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.sleep_start
;
3159 if (unlikely(delta
> se
->statistics
.sleep_max
))
3160 se
->statistics
.sleep_max
= delta
;
3162 se
->statistics
.sleep_start
= 0;
3163 se
->statistics
.sum_sleep_runtime
+= delta
;
3166 account_scheduler_latency(tsk
, delta
>> 10, 1);
3167 trace_sched_stat_sleep(tsk
, delta
);
3170 if (se
->statistics
.block_start
) {
3171 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.block_start
;
3176 if (unlikely(delta
> se
->statistics
.block_max
))
3177 se
->statistics
.block_max
= delta
;
3179 se
->statistics
.block_start
= 0;
3180 se
->statistics
.sum_sleep_runtime
+= delta
;
3183 if (tsk
->in_iowait
) {
3184 se
->statistics
.iowait_sum
+= delta
;
3185 se
->statistics
.iowait_count
++;
3186 trace_sched_stat_iowait(tsk
, delta
);
3189 trace_sched_stat_blocked(tsk
, delta
);
3192 * Blocking time is in units of nanosecs, so shift by
3193 * 20 to get a milliseconds-range estimation of the
3194 * amount of time that the task spent sleeping:
3196 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
3197 profile_hits(SLEEP_PROFILING
,
3198 (void *)get_wchan(tsk
),
3201 account_scheduler_latency(tsk
, delta
>> 10, 0);
3207 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3209 #ifdef CONFIG_SCHED_DEBUG
3210 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3215 if (d
> 3*sysctl_sched_latency
)
3216 schedstat_inc(cfs_rq
, nr_spread_over
);
3221 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3223 u64 vruntime
= cfs_rq
->min_vruntime
;
3226 * The 'current' period is already promised to the current tasks,
3227 * however the extra weight of the new task will slow them down a
3228 * little, place the new task so that it fits in the slot that
3229 * stays open at the end.
3231 if (initial
&& sched_feat(START_DEBIT
))
3232 vruntime
+= sched_vslice(cfs_rq
, se
);
3234 /* sleeps up to a single latency don't count. */
3236 unsigned long thresh
= sysctl_sched_latency
;
3239 * Halve their sleep time's effect, to allow
3240 * for a gentler effect of sleepers:
3242 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3248 /* ensure we never gain time by being placed backwards. */
3249 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3252 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3254 static inline void check_schedstat_required(void)
3256 #ifdef CONFIG_SCHEDSTATS
3257 if (schedstat_enabled())
3260 /* Force schedstat enabled if a dependent tracepoint is active */
3261 if (trace_sched_stat_wait_enabled() ||
3262 trace_sched_stat_sleep_enabled() ||
3263 trace_sched_stat_iowait_enabled() ||
3264 trace_sched_stat_blocked_enabled() ||
3265 trace_sched_stat_runtime_enabled()) {
3266 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3267 "stat_blocked and stat_runtime require the "
3268 "kernel parameter schedstats=enabled or "
3269 "kernel.sched_schedstats=1\n");
3280 * update_min_vruntime()
3281 * vruntime -= min_vruntime
3285 * update_min_vruntime()
3286 * vruntime += min_vruntime
3288 * this way the vruntime transition between RQs is done when both
3289 * min_vruntime are up-to-date.
3293 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
3294 * vruntime -= min_vruntime
3298 * update_min_vruntime()
3299 * vruntime += min_vruntime
3301 * this way we don't have the most up-to-date min_vruntime on the originating
3302 * CPU and an up-to-date min_vruntime on the destination CPU.
3306 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3308 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_MIGRATED
);
3309 bool curr
= cfs_rq
->curr
== se
;
3312 * If we're the current task, we must renormalise before calling
3316 se
->vruntime
+= cfs_rq
->min_vruntime
;
3318 update_curr(cfs_rq
);
3321 * Otherwise, renormalise after, such that we're placed at the current
3322 * moment in time, instead of some random moment in the past. Being
3323 * placed in the past could significantly boost this task to the
3324 * fairness detriment of existing tasks.
3326 if (renorm
&& !curr
)
3327 se
->vruntime
+= cfs_rq
->min_vruntime
;
3329 enqueue_entity_load_avg(cfs_rq
, se
);
3330 account_entity_enqueue(cfs_rq
, se
);
3331 update_cfs_shares(cfs_rq
);
3333 if (flags
& ENQUEUE_WAKEUP
) {
3334 place_entity(cfs_rq
, se
, 0);
3335 if (schedstat_enabled())
3336 enqueue_sleeper(cfs_rq
, se
);
3339 check_schedstat_required();
3340 if (schedstat_enabled()) {
3341 update_stats_enqueue(cfs_rq
, se
);
3342 check_spread(cfs_rq
, se
);
3345 __enqueue_entity(cfs_rq
, se
);
3348 if (cfs_rq
->nr_running
== 1) {
3349 list_add_leaf_cfs_rq(cfs_rq
);
3350 check_enqueue_throttle(cfs_rq
);
3354 static void __clear_buddies_last(struct sched_entity
*se
)
3356 for_each_sched_entity(se
) {
3357 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3358 if (cfs_rq
->last
!= se
)
3361 cfs_rq
->last
= NULL
;
3365 static void __clear_buddies_next(struct sched_entity
*se
)
3367 for_each_sched_entity(se
) {
3368 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3369 if (cfs_rq
->next
!= se
)
3372 cfs_rq
->next
= NULL
;
3376 static void __clear_buddies_skip(struct sched_entity
*se
)
3378 for_each_sched_entity(se
) {
3379 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3380 if (cfs_rq
->skip
!= se
)
3383 cfs_rq
->skip
= NULL
;
3387 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3389 if (cfs_rq
->last
== se
)
3390 __clear_buddies_last(se
);
3392 if (cfs_rq
->next
== se
)
3393 __clear_buddies_next(se
);
3395 if (cfs_rq
->skip
== se
)
3396 __clear_buddies_skip(se
);
3399 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3402 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3405 * Update run-time statistics of the 'current'.
3407 update_curr(cfs_rq
);
3408 dequeue_entity_load_avg(cfs_rq
, se
);
3410 if (schedstat_enabled())
3411 update_stats_dequeue(cfs_rq
, se
, flags
);
3413 clear_buddies(cfs_rq
, se
);
3415 if (se
!= cfs_rq
->curr
)
3416 __dequeue_entity(cfs_rq
, se
);
3418 account_entity_dequeue(cfs_rq
, se
);
3421 * Normalize the entity after updating the min_vruntime because the
3422 * update can refer to the ->curr item and we need to reflect this
3423 * movement in our normalized position.
3425 if (!(flags
& DEQUEUE_SLEEP
))
3426 se
->vruntime
-= cfs_rq
->min_vruntime
;
3428 /* return excess runtime on last dequeue */
3429 return_cfs_rq_runtime(cfs_rq
);
3431 update_min_vruntime(cfs_rq
);
3432 update_cfs_shares(cfs_rq
);
3436 * Preempt the current task with a newly woken task if needed:
3439 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3441 unsigned long ideal_runtime
, delta_exec
;
3442 struct sched_entity
*se
;
3445 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3446 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3447 if (delta_exec
> ideal_runtime
) {
3448 resched_curr(rq_of(cfs_rq
));
3450 * The current task ran long enough, ensure it doesn't get
3451 * re-elected due to buddy favours.
3453 clear_buddies(cfs_rq
, curr
);
3458 * Ensure that a task that missed wakeup preemption by a
3459 * narrow margin doesn't have to wait for a full slice.
3460 * This also mitigates buddy induced latencies under load.
3462 if (delta_exec
< sysctl_sched_min_granularity
)
3465 se
= __pick_first_entity(cfs_rq
);
3466 delta
= curr
->vruntime
- se
->vruntime
;
3471 if (delta
> ideal_runtime
)
3472 resched_curr(rq_of(cfs_rq
));
3476 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3478 /* 'current' is not kept within the tree. */
3481 * Any task has to be enqueued before it get to execute on
3482 * a CPU. So account for the time it spent waiting on the
3485 if (schedstat_enabled())
3486 update_stats_wait_end(cfs_rq
, se
);
3487 __dequeue_entity(cfs_rq
, se
);
3488 update_load_avg(se
, 1);
3491 update_stats_curr_start(cfs_rq
, se
);
3493 #ifdef CONFIG_SCHEDSTATS
3495 * Track our maximum slice length, if the CPU's load is at
3496 * least twice that of our own weight (i.e. dont track it
3497 * when there are only lesser-weight tasks around):
3499 if (schedstat_enabled() && rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3500 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
3501 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
3504 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3508 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3511 * Pick the next process, keeping these things in mind, in this order:
3512 * 1) keep things fair between processes/task groups
3513 * 2) pick the "next" process, since someone really wants that to run
3514 * 3) pick the "last" process, for cache locality
3515 * 4) do not run the "skip" process, if something else is available
3517 static struct sched_entity
*
3518 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3520 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
3521 struct sched_entity
*se
;
3524 * If curr is set we have to see if its left of the leftmost entity
3525 * still in the tree, provided there was anything in the tree at all.
3527 if (!left
|| (curr
&& entity_before(curr
, left
)))
3530 se
= left
; /* ideally we run the leftmost entity */
3533 * Avoid running the skip buddy, if running something else can
3534 * be done without getting too unfair.
3536 if (cfs_rq
->skip
== se
) {
3537 struct sched_entity
*second
;
3540 second
= __pick_first_entity(cfs_rq
);
3542 second
= __pick_next_entity(se
);
3543 if (!second
|| (curr
&& entity_before(curr
, second
)))
3547 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
3552 * Prefer last buddy, try to return the CPU to a preempted task.
3554 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
3558 * Someone really wants this to run. If it's not unfair, run it.
3560 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
3563 clear_buddies(cfs_rq
, se
);
3568 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3570 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
3573 * If still on the runqueue then deactivate_task()
3574 * was not called and update_curr() has to be done:
3577 update_curr(cfs_rq
);
3579 /* throttle cfs_rqs exceeding runtime */
3580 check_cfs_rq_runtime(cfs_rq
);
3582 if (schedstat_enabled()) {
3583 check_spread(cfs_rq
, prev
);
3585 update_stats_wait_start(cfs_rq
, prev
);
3589 /* Put 'current' back into the tree. */
3590 __enqueue_entity(cfs_rq
, prev
);
3591 /* in !on_rq case, update occurred at dequeue */
3592 update_load_avg(prev
, 0);
3594 cfs_rq
->curr
= NULL
;
3598 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
3601 * Update run-time statistics of the 'current'.
3603 update_curr(cfs_rq
);
3606 * Ensure that runnable average is periodically updated.
3608 update_load_avg(curr
, 1);
3609 update_cfs_shares(cfs_rq
);
3611 #ifdef CONFIG_SCHED_HRTICK
3613 * queued ticks are scheduled to match the slice, so don't bother
3614 * validating it and just reschedule.
3617 resched_curr(rq_of(cfs_rq
));
3621 * don't let the period tick interfere with the hrtick preemption
3623 if (!sched_feat(DOUBLE_TICK
) &&
3624 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3628 if (cfs_rq
->nr_running
> 1)
3629 check_preempt_tick(cfs_rq
, curr
);
3633 /**************************************************
3634 * CFS bandwidth control machinery
3637 #ifdef CONFIG_CFS_BANDWIDTH
3639 #ifdef HAVE_JUMP_LABEL
3640 static struct static_key __cfs_bandwidth_used
;
3642 static inline bool cfs_bandwidth_used(void)
3644 return static_key_false(&__cfs_bandwidth_used
);
3647 void cfs_bandwidth_usage_inc(void)
3649 static_key_slow_inc(&__cfs_bandwidth_used
);
3652 void cfs_bandwidth_usage_dec(void)
3654 static_key_slow_dec(&__cfs_bandwidth_used
);
3656 #else /* HAVE_JUMP_LABEL */
3657 static bool cfs_bandwidth_used(void)
3662 void cfs_bandwidth_usage_inc(void) {}
3663 void cfs_bandwidth_usage_dec(void) {}
3664 #endif /* HAVE_JUMP_LABEL */
3667 * default period for cfs group bandwidth.
3668 * default: 0.1s, units: nanoseconds
3670 static inline u64
default_cfs_period(void)
3672 return 100000000ULL;
3675 static inline u64
sched_cfs_bandwidth_slice(void)
3677 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3681 * Replenish runtime according to assigned quota and update expiration time.
3682 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3683 * additional synchronization around rq->lock.
3685 * requires cfs_b->lock
3687 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3691 if (cfs_b
->quota
== RUNTIME_INF
)
3694 now
= sched_clock_cpu(smp_processor_id());
3695 cfs_b
->runtime
= cfs_b
->quota
;
3696 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3699 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3701 return &tg
->cfs_bandwidth
;
3704 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3705 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3707 if (unlikely(cfs_rq
->throttle_count
))
3708 return cfs_rq
->throttled_clock_task
;
3710 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3713 /* returns 0 on failure to allocate runtime */
3714 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3716 struct task_group
*tg
= cfs_rq
->tg
;
3717 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3718 u64 amount
= 0, min_amount
, expires
;
3720 /* note: this is a positive sum as runtime_remaining <= 0 */
3721 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3723 raw_spin_lock(&cfs_b
->lock
);
3724 if (cfs_b
->quota
== RUNTIME_INF
)
3725 amount
= min_amount
;
3727 start_cfs_bandwidth(cfs_b
);
3729 if (cfs_b
->runtime
> 0) {
3730 amount
= min(cfs_b
->runtime
, min_amount
);
3731 cfs_b
->runtime
-= amount
;
3735 expires
= cfs_b
->runtime_expires
;
3736 raw_spin_unlock(&cfs_b
->lock
);
3738 cfs_rq
->runtime_remaining
+= amount
;
3740 * we may have advanced our local expiration to account for allowed
3741 * spread between our sched_clock and the one on which runtime was
3744 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3745 cfs_rq
->runtime_expires
= expires
;
3747 return cfs_rq
->runtime_remaining
> 0;
3751 * Note: This depends on the synchronization provided by sched_clock and the
3752 * fact that rq->clock snapshots this value.
3754 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3756 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3758 /* if the deadline is ahead of our clock, nothing to do */
3759 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3762 if (cfs_rq
->runtime_remaining
< 0)
3766 * If the local deadline has passed we have to consider the
3767 * possibility that our sched_clock is 'fast' and the global deadline
3768 * has not truly expired.
3770 * Fortunately we can check determine whether this the case by checking
3771 * whether the global deadline has advanced. It is valid to compare
3772 * cfs_b->runtime_expires without any locks since we only care about
3773 * exact equality, so a partial write will still work.
3776 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
3777 /* extend local deadline, drift is bounded above by 2 ticks */
3778 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3780 /* global deadline is ahead, expiration has passed */
3781 cfs_rq
->runtime_remaining
= 0;
3785 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3787 /* dock delta_exec before expiring quota (as it could span periods) */
3788 cfs_rq
->runtime_remaining
-= delta_exec
;
3789 expire_cfs_rq_runtime(cfs_rq
);
3791 if (likely(cfs_rq
->runtime_remaining
> 0))
3795 * if we're unable to extend our runtime we resched so that the active
3796 * hierarchy can be throttled
3798 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3799 resched_curr(rq_of(cfs_rq
));
3802 static __always_inline
3803 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3805 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3808 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3811 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3813 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3816 /* check whether cfs_rq, or any parent, is throttled */
3817 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3819 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3823 * Ensure that neither of the group entities corresponding to src_cpu or
3824 * dest_cpu are members of a throttled hierarchy when performing group
3825 * load-balance operations.
3827 static inline int throttled_lb_pair(struct task_group
*tg
,
3828 int src_cpu
, int dest_cpu
)
3830 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3832 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3833 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3835 return throttled_hierarchy(src_cfs_rq
) ||
3836 throttled_hierarchy(dest_cfs_rq
);
3839 /* updated child weight may affect parent so we have to do this bottom up */
3840 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3842 struct rq
*rq
= data
;
3843 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3845 cfs_rq
->throttle_count
--;
3847 if (!cfs_rq
->throttle_count
) {
3848 /* adjust cfs_rq_clock_task() */
3849 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3850 cfs_rq
->throttled_clock_task
;
3857 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3859 struct rq
*rq
= data
;
3860 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3862 /* group is entering throttled state, stop time */
3863 if (!cfs_rq
->throttle_count
)
3864 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3865 cfs_rq
->throttle_count
++;
3870 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3872 struct rq
*rq
= rq_of(cfs_rq
);
3873 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3874 struct sched_entity
*se
;
3875 long task_delta
, dequeue
= 1;
3878 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3880 /* freeze hierarchy runnable averages while throttled */
3882 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3885 task_delta
= cfs_rq
->h_nr_running
;
3886 for_each_sched_entity(se
) {
3887 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3888 /* throttled entity or throttle-on-deactivate */
3893 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3894 qcfs_rq
->h_nr_running
-= task_delta
;
3896 if (qcfs_rq
->load
.weight
)
3901 sub_nr_running(rq
, task_delta
);
3903 cfs_rq
->throttled
= 1;
3904 cfs_rq
->throttled_clock
= rq_clock(rq
);
3905 raw_spin_lock(&cfs_b
->lock
);
3906 empty
= list_empty(&cfs_b
->throttled_cfs_rq
);
3909 * Add to the _head_ of the list, so that an already-started
3910 * distribute_cfs_runtime will not see us
3912 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3915 * If we're the first throttled task, make sure the bandwidth
3919 start_cfs_bandwidth(cfs_b
);
3921 raw_spin_unlock(&cfs_b
->lock
);
3924 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3926 struct rq
*rq
= rq_of(cfs_rq
);
3927 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3928 struct sched_entity
*se
;
3932 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3934 cfs_rq
->throttled
= 0;
3936 update_rq_clock(rq
);
3938 raw_spin_lock(&cfs_b
->lock
);
3939 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3940 list_del_rcu(&cfs_rq
->throttled_list
);
3941 raw_spin_unlock(&cfs_b
->lock
);
3943 /* update hierarchical throttle state */
3944 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3946 if (!cfs_rq
->load
.weight
)
3949 task_delta
= cfs_rq
->h_nr_running
;
3950 for_each_sched_entity(se
) {
3954 cfs_rq
= cfs_rq_of(se
);
3956 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3957 cfs_rq
->h_nr_running
+= task_delta
;
3959 if (cfs_rq_throttled(cfs_rq
))
3964 add_nr_running(rq
, task_delta
);
3966 /* determine whether we need to wake up potentially idle cpu */
3967 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
3971 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
3972 u64 remaining
, u64 expires
)
3974 struct cfs_rq
*cfs_rq
;
3976 u64 starting_runtime
= remaining
;
3979 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
3981 struct rq
*rq
= rq_of(cfs_rq
);
3983 raw_spin_lock(&rq
->lock
);
3984 if (!cfs_rq_throttled(cfs_rq
))
3987 runtime
= -cfs_rq
->runtime_remaining
+ 1;
3988 if (runtime
> remaining
)
3989 runtime
= remaining
;
3990 remaining
-= runtime
;
3992 cfs_rq
->runtime_remaining
+= runtime
;
3993 cfs_rq
->runtime_expires
= expires
;
3995 /* we check whether we're throttled above */
3996 if (cfs_rq
->runtime_remaining
> 0)
3997 unthrottle_cfs_rq(cfs_rq
);
4000 raw_spin_unlock(&rq
->lock
);
4007 return starting_runtime
- remaining
;
4011 * Responsible for refilling a task_group's bandwidth and unthrottling its
4012 * cfs_rqs as appropriate. If there has been no activity within the last
4013 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4014 * used to track this state.
4016 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
4018 u64 runtime
, runtime_expires
;
4021 /* no need to continue the timer with no bandwidth constraint */
4022 if (cfs_b
->quota
== RUNTIME_INF
)
4023 goto out_deactivate
;
4025 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4026 cfs_b
->nr_periods
+= overrun
;
4029 * idle depends on !throttled (for the case of a large deficit), and if
4030 * we're going inactive then everything else can be deferred
4032 if (cfs_b
->idle
&& !throttled
)
4033 goto out_deactivate
;
4035 __refill_cfs_bandwidth_runtime(cfs_b
);
4038 /* mark as potentially idle for the upcoming period */
4043 /* account preceding periods in which throttling occurred */
4044 cfs_b
->nr_throttled
+= overrun
;
4046 runtime_expires
= cfs_b
->runtime_expires
;
4049 * This check is repeated as we are holding onto the new bandwidth while
4050 * we unthrottle. This can potentially race with an unthrottled group
4051 * trying to acquire new bandwidth from the global pool. This can result
4052 * in us over-using our runtime if it is all used during this loop, but
4053 * only by limited amounts in that extreme case.
4055 while (throttled
&& cfs_b
->runtime
> 0) {
4056 runtime
= cfs_b
->runtime
;
4057 raw_spin_unlock(&cfs_b
->lock
);
4058 /* we can't nest cfs_b->lock while distributing bandwidth */
4059 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
4061 raw_spin_lock(&cfs_b
->lock
);
4063 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4065 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4069 * While we are ensured activity in the period following an
4070 * unthrottle, this also covers the case in which the new bandwidth is
4071 * insufficient to cover the existing bandwidth deficit. (Forcing the
4072 * timer to remain active while there are any throttled entities.)
4082 /* a cfs_rq won't donate quota below this amount */
4083 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
4084 /* minimum remaining period time to redistribute slack quota */
4085 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
4086 /* how long we wait to gather additional slack before distributing */
4087 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
4090 * Are we near the end of the current quota period?
4092 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4093 * hrtimer base being cleared by hrtimer_start. In the case of
4094 * migrate_hrtimers, base is never cleared, so we are fine.
4096 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
4098 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
4101 /* if the call-back is running a quota refresh is already occurring */
4102 if (hrtimer_callback_running(refresh_timer
))
4105 /* is a quota refresh about to occur? */
4106 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
4107 if (remaining
< min_expire
)
4113 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
4115 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
4117 /* if there's a quota refresh soon don't bother with slack */
4118 if (runtime_refresh_within(cfs_b
, min_left
))
4121 hrtimer_start(&cfs_b
->slack_timer
,
4122 ns_to_ktime(cfs_bandwidth_slack_period
),
4126 /* we know any runtime found here is valid as update_curr() precedes return */
4127 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4129 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4130 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
4132 if (slack_runtime
<= 0)
4135 raw_spin_lock(&cfs_b
->lock
);
4136 if (cfs_b
->quota
!= RUNTIME_INF
&&
4137 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
4138 cfs_b
->runtime
+= slack_runtime
;
4140 /* we are under rq->lock, defer unthrottling using a timer */
4141 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
4142 !list_empty(&cfs_b
->throttled_cfs_rq
))
4143 start_cfs_slack_bandwidth(cfs_b
);
4145 raw_spin_unlock(&cfs_b
->lock
);
4147 /* even if it's not valid for return we don't want to try again */
4148 cfs_rq
->runtime_remaining
-= slack_runtime
;
4151 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4153 if (!cfs_bandwidth_used())
4156 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
4159 __return_cfs_rq_runtime(cfs_rq
);
4163 * This is done with a timer (instead of inline with bandwidth return) since
4164 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4166 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
4168 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
4171 /* confirm we're still not at a refresh boundary */
4172 raw_spin_lock(&cfs_b
->lock
);
4173 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
4174 raw_spin_unlock(&cfs_b
->lock
);
4178 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
4179 runtime
= cfs_b
->runtime
;
4181 expires
= cfs_b
->runtime_expires
;
4182 raw_spin_unlock(&cfs_b
->lock
);
4187 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
4189 raw_spin_lock(&cfs_b
->lock
);
4190 if (expires
== cfs_b
->runtime_expires
)
4191 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4192 raw_spin_unlock(&cfs_b
->lock
);
4196 * When a group wakes up we want to make sure that its quota is not already
4197 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4198 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4200 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
4202 if (!cfs_bandwidth_used())
4205 /* an active group must be handled by the update_curr()->put() path */
4206 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
4209 /* ensure the group is not already throttled */
4210 if (cfs_rq_throttled(cfs_rq
))
4213 /* update runtime allocation */
4214 account_cfs_rq_runtime(cfs_rq
, 0);
4215 if (cfs_rq
->runtime_remaining
<= 0)
4216 throttle_cfs_rq(cfs_rq
);
4219 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4220 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4222 if (!cfs_bandwidth_used())
4225 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
4229 * it's possible for a throttled entity to be forced into a running
4230 * state (e.g. set_curr_task), in this case we're finished.
4232 if (cfs_rq_throttled(cfs_rq
))
4235 throttle_cfs_rq(cfs_rq
);
4239 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
4241 struct cfs_bandwidth
*cfs_b
=
4242 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
4244 do_sched_cfs_slack_timer(cfs_b
);
4246 return HRTIMER_NORESTART
;
4249 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
4251 struct cfs_bandwidth
*cfs_b
=
4252 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4256 raw_spin_lock(&cfs_b
->lock
);
4258 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
4262 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4265 cfs_b
->period_active
= 0;
4266 raw_spin_unlock(&cfs_b
->lock
);
4268 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4271 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4273 raw_spin_lock_init(&cfs_b
->lock
);
4275 cfs_b
->quota
= RUNTIME_INF
;
4276 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4278 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4279 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
4280 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4281 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4282 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4285 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4287 cfs_rq
->runtime_enabled
= 0;
4288 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4291 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4293 lockdep_assert_held(&cfs_b
->lock
);
4295 if (!cfs_b
->period_active
) {
4296 cfs_b
->period_active
= 1;
4297 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
4298 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
4302 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4304 /* init_cfs_bandwidth() was not called */
4305 if (!cfs_b
->throttled_cfs_rq
.next
)
4308 hrtimer_cancel(&cfs_b
->period_timer
);
4309 hrtimer_cancel(&cfs_b
->slack_timer
);
4312 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4314 struct cfs_rq
*cfs_rq
;
4316 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4317 struct cfs_bandwidth
*cfs_b
= &cfs_rq
->tg
->cfs_bandwidth
;
4319 raw_spin_lock(&cfs_b
->lock
);
4320 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4321 raw_spin_unlock(&cfs_b
->lock
);
4325 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4327 struct cfs_rq
*cfs_rq
;
4329 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4330 if (!cfs_rq
->runtime_enabled
)
4334 * clock_task is not advancing so we just need to make sure
4335 * there's some valid quota amount
4337 cfs_rq
->runtime_remaining
= 1;
4339 * Offline rq is schedulable till cpu is completely disabled
4340 * in take_cpu_down(), so we prevent new cfs throttling here.
4342 cfs_rq
->runtime_enabled
= 0;
4344 if (cfs_rq_throttled(cfs_rq
))
4345 unthrottle_cfs_rq(cfs_rq
);
4349 #else /* CONFIG_CFS_BANDWIDTH */
4350 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4352 return rq_clock_task(rq_of(cfs_rq
));
4355 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4356 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4357 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4358 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4360 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4365 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4370 static inline int throttled_lb_pair(struct task_group
*tg
,
4371 int src_cpu
, int dest_cpu
)
4376 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4378 #ifdef CONFIG_FAIR_GROUP_SCHED
4379 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4382 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4386 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4387 static inline void update_runtime_enabled(struct rq
*rq
) {}
4388 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4390 #endif /* CONFIG_CFS_BANDWIDTH */
4392 /**************************************************
4393 * CFS operations on tasks:
4396 #ifdef CONFIG_SCHED_HRTICK
4397 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4399 struct sched_entity
*se
= &p
->se
;
4400 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4402 WARN_ON(task_rq(p
) != rq
);
4404 if (cfs_rq
->nr_running
> 1) {
4405 u64 slice
= sched_slice(cfs_rq
, se
);
4406 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4407 s64 delta
= slice
- ran
;
4414 hrtick_start(rq
, delta
);
4419 * called from enqueue/dequeue and updates the hrtick when the
4420 * current task is from our class and nr_running is low enough
4423 static void hrtick_update(struct rq
*rq
)
4425 struct task_struct
*curr
= rq
->curr
;
4427 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4430 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4431 hrtick_start_fair(rq
, curr
);
4433 #else /* !CONFIG_SCHED_HRTICK */
4435 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4439 static inline void hrtick_update(struct rq
*rq
)
4445 * The enqueue_task method is called before nr_running is
4446 * increased. Here we update the fair scheduling stats and
4447 * then put the task into the rbtree:
4450 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4452 struct cfs_rq
*cfs_rq
;
4453 struct sched_entity
*se
= &p
->se
;
4455 for_each_sched_entity(se
) {
4458 cfs_rq
= cfs_rq_of(se
);
4459 enqueue_entity(cfs_rq
, se
, flags
);
4462 * end evaluation on encountering a throttled cfs_rq
4464 * note: in the case of encountering a throttled cfs_rq we will
4465 * post the final h_nr_running increment below.
4467 if (cfs_rq_throttled(cfs_rq
))
4469 cfs_rq
->h_nr_running
++;
4471 flags
= ENQUEUE_WAKEUP
;
4474 for_each_sched_entity(se
) {
4475 cfs_rq
= cfs_rq_of(se
);
4476 cfs_rq
->h_nr_running
++;
4478 if (cfs_rq_throttled(cfs_rq
))
4481 update_load_avg(se
, 1);
4482 update_cfs_shares(cfs_rq
);
4486 add_nr_running(rq
, 1);
4491 static void set_next_buddy(struct sched_entity
*se
);
4494 * The dequeue_task method is called before nr_running is
4495 * decreased. We remove the task from the rbtree and
4496 * update the fair scheduling stats:
4498 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4500 struct cfs_rq
*cfs_rq
;
4501 struct sched_entity
*se
= &p
->se
;
4502 int task_sleep
= flags
& DEQUEUE_SLEEP
;
4504 for_each_sched_entity(se
) {
4505 cfs_rq
= cfs_rq_of(se
);
4506 dequeue_entity(cfs_rq
, se
, flags
);
4509 * end evaluation on encountering a throttled cfs_rq
4511 * note: in the case of encountering a throttled cfs_rq we will
4512 * post the final h_nr_running decrement below.
4514 if (cfs_rq_throttled(cfs_rq
))
4516 cfs_rq
->h_nr_running
--;
4518 /* Don't dequeue parent if it has other entities besides us */
4519 if (cfs_rq
->load
.weight
) {
4521 * Bias pick_next to pick a task from this cfs_rq, as
4522 * p is sleeping when it is within its sched_slice.
4524 if (task_sleep
&& parent_entity(se
))
4525 set_next_buddy(parent_entity(se
));
4527 /* avoid re-evaluating load for this entity */
4528 se
= parent_entity(se
);
4531 flags
|= DEQUEUE_SLEEP
;
4534 for_each_sched_entity(se
) {
4535 cfs_rq
= cfs_rq_of(se
);
4536 cfs_rq
->h_nr_running
--;
4538 if (cfs_rq_throttled(cfs_rq
))
4541 update_load_avg(se
, 1);
4542 update_cfs_shares(cfs_rq
);
4546 sub_nr_running(rq
, 1);
4552 #ifdef CONFIG_NO_HZ_COMMON
4554 * per rq 'load' arrray crap; XXX kill this.
4558 * The exact cpuload calculated at every tick would be:
4560 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4562 * If a cpu misses updates for n ticks (as it was idle) and update gets
4563 * called on the n+1-th tick when cpu may be busy, then we have:
4565 * load_n = (1 - 1/2^i)^n * load_0
4566 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4568 * decay_load_missed() below does efficient calculation of
4570 * load' = (1 - 1/2^i)^n * load
4572 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4573 * This allows us to precompute the above in said factors, thereby allowing the
4574 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4575 * fixed_power_int())
4577 * The calculation is approximated on a 128 point scale.
4579 #define DEGRADE_SHIFT 7
4581 static const u8 degrade_zero_ticks
[CPU_LOAD_IDX_MAX
] = {0, 8, 32, 64, 128};
4582 static const u8 degrade_factor
[CPU_LOAD_IDX_MAX
][DEGRADE_SHIFT
+ 1] = {
4583 { 0, 0, 0, 0, 0, 0, 0, 0 },
4584 { 64, 32, 8, 0, 0, 0, 0, 0 },
4585 { 96, 72, 40, 12, 1, 0, 0, 0 },
4586 { 112, 98, 75, 43, 15, 1, 0, 0 },
4587 { 120, 112, 98, 76, 45, 16, 2, 0 }
4591 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4592 * would be when CPU is idle and so we just decay the old load without
4593 * adding any new load.
4595 static unsigned long
4596 decay_load_missed(unsigned long load
, unsigned long missed_updates
, int idx
)
4600 if (!missed_updates
)
4603 if (missed_updates
>= degrade_zero_ticks
[idx
])
4607 return load
>> missed_updates
;
4609 while (missed_updates
) {
4610 if (missed_updates
% 2)
4611 load
= (load
* degrade_factor
[idx
][j
]) >> DEGRADE_SHIFT
;
4613 missed_updates
>>= 1;
4618 #endif /* CONFIG_NO_HZ_COMMON */
4621 * __cpu_load_update - update the rq->cpu_load[] statistics
4622 * @this_rq: The rq to update statistics for
4623 * @this_load: The current load
4624 * @pending_updates: The number of missed updates
4626 * Update rq->cpu_load[] statistics. This function is usually called every
4627 * scheduler tick (TICK_NSEC).
4629 * This function computes a decaying average:
4631 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4633 * Because of NOHZ it might not get called on every tick which gives need for
4634 * the @pending_updates argument.
4636 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4637 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4638 * = A * (A * load[i]_n-2 + B) + B
4639 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4640 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4641 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4642 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4643 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4645 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4646 * any change in load would have resulted in the tick being turned back on.
4648 * For regular NOHZ, this reduces to:
4650 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4652 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4655 static void cpu_load_update(struct rq
*this_rq
, unsigned long this_load
,
4656 unsigned long pending_updates
)
4658 unsigned long __maybe_unused tickless_load
= this_rq
->cpu_load
[0];
4661 this_rq
->nr_load_updates
++;
4663 /* Update our load: */
4664 this_rq
->cpu_load
[0] = this_load
; /* Fasttrack for idx 0 */
4665 for (i
= 1, scale
= 2; i
< CPU_LOAD_IDX_MAX
; i
++, scale
+= scale
) {
4666 unsigned long old_load
, new_load
;
4668 /* scale is effectively 1 << i now, and >> i divides by scale */
4670 old_load
= this_rq
->cpu_load
[i
];
4671 #ifdef CONFIG_NO_HZ_COMMON
4672 old_load
= decay_load_missed(old_load
, pending_updates
- 1, i
);
4673 if (tickless_load
) {
4674 old_load
-= decay_load_missed(tickless_load
, pending_updates
- 1, i
);
4676 * old_load can never be a negative value because a
4677 * decayed tickless_load cannot be greater than the
4678 * original tickless_load.
4680 old_load
+= tickless_load
;
4683 new_load
= this_load
;
4685 * Round up the averaging division if load is increasing. This
4686 * prevents us from getting stuck on 9 if the load is 10, for
4689 if (new_load
> old_load
)
4690 new_load
+= scale
- 1;
4692 this_rq
->cpu_load
[i
] = (old_load
* (scale
- 1) + new_load
) >> i
;
4695 sched_avg_update(this_rq
);
4698 /* Used instead of source_load when we know the type == 0 */
4699 static unsigned long weighted_cpuload(const int cpu
)
4701 return cfs_rq_runnable_load_avg(&cpu_rq(cpu
)->cfs
);
4704 #ifdef CONFIG_NO_HZ_COMMON
4706 * There is no sane way to deal with nohz on smp when using jiffies because the
4707 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4708 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4710 * Therefore we need to avoid the delta approach from the regular tick when
4711 * possible since that would seriously skew the load calculation. This is why we
4712 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4713 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
4714 * loop exit, nohz_idle_balance, nohz full exit...)
4716 * This means we might still be one tick off for nohz periods.
4719 static void cpu_load_update_nohz(struct rq
*this_rq
,
4720 unsigned long curr_jiffies
,
4723 unsigned long pending_updates
;
4725 pending_updates
= curr_jiffies
- this_rq
->last_load_update_tick
;
4726 if (pending_updates
) {
4727 this_rq
->last_load_update_tick
= curr_jiffies
;
4729 * In the regular NOHZ case, we were idle, this means load 0.
4730 * In the NOHZ_FULL case, we were non-idle, we should consider
4731 * its weighted load.
4733 cpu_load_update(this_rq
, load
, pending_updates
);
4738 * Called from nohz_idle_balance() to update the load ratings before doing the
4741 static void cpu_load_update_idle(struct rq
*this_rq
)
4744 * bail if there's load or we're actually up-to-date.
4746 if (weighted_cpuload(cpu_of(this_rq
)))
4749 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), 0);
4753 * Record CPU load on nohz entry so we know the tickless load to account
4754 * on nohz exit. cpu_load[0] happens then to be updated more frequently
4755 * than other cpu_load[idx] but it should be fine as cpu_load readers
4756 * shouldn't rely into synchronized cpu_load[*] updates.
4758 void cpu_load_update_nohz_start(void)
4760 struct rq
*this_rq
= this_rq();
4763 * This is all lockless but should be fine. If weighted_cpuload changes
4764 * concurrently we'll exit nohz. And cpu_load write can race with
4765 * cpu_load_update_idle() but both updater would be writing the same.
4767 this_rq
->cpu_load
[0] = weighted_cpuload(cpu_of(this_rq
));
4771 * Account the tickless load in the end of a nohz frame.
4773 void cpu_load_update_nohz_stop(void)
4775 unsigned long curr_jiffies
= READ_ONCE(jiffies
);
4776 struct rq
*this_rq
= this_rq();
4779 if (curr_jiffies
== this_rq
->last_load_update_tick
)
4782 load
= weighted_cpuload(cpu_of(this_rq
));
4783 raw_spin_lock(&this_rq
->lock
);
4784 update_rq_clock(this_rq
);
4785 cpu_load_update_nohz(this_rq
, curr_jiffies
, load
);
4786 raw_spin_unlock(&this_rq
->lock
);
4788 #else /* !CONFIG_NO_HZ_COMMON */
4789 static inline void cpu_load_update_nohz(struct rq
*this_rq
,
4790 unsigned long curr_jiffies
,
4791 unsigned long load
) { }
4792 #endif /* CONFIG_NO_HZ_COMMON */
4794 static void cpu_load_update_periodic(struct rq
*this_rq
, unsigned long load
)
4796 #ifdef CONFIG_NO_HZ_COMMON
4797 /* See the mess around cpu_load_update_nohz(). */
4798 this_rq
->last_load_update_tick
= READ_ONCE(jiffies
);
4800 cpu_load_update(this_rq
, load
, 1);
4804 * Called from scheduler_tick()
4806 void cpu_load_update_active(struct rq
*this_rq
)
4808 unsigned long load
= weighted_cpuload(cpu_of(this_rq
));
4810 if (tick_nohz_tick_stopped())
4811 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), load
);
4813 cpu_load_update_periodic(this_rq
, load
);
4817 * Return a low guess at the load of a migration-source cpu weighted
4818 * according to the scheduling class and "nice" value.
4820 * We want to under-estimate the load of migration sources, to
4821 * balance conservatively.
4823 static unsigned long source_load(int cpu
, int type
)
4825 struct rq
*rq
= cpu_rq(cpu
);
4826 unsigned long total
= weighted_cpuload(cpu
);
4828 if (type
== 0 || !sched_feat(LB_BIAS
))
4831 return min(rq
->cpu_load
[type
-1], total
);
4835 * Return a high guess at the load of a migration-target cpu weighted
4836 * according to the scheduling class and "nice" value.
4838 static unsigned long target_load(int cpu
, int type
)
4840 struct rq
*rq
= cpu_rq(cpu
);
4841 unsigned long total
= weighted_cpuload(cpu
);
4843 if (type
== 0 || !sched_feat(LB_BIAS
))
4846 return max(rq
->cpu_load
[type
-1], total
);
4849 static unsigned long capacity_of(int cpu
)
4851 return cpu_rq(cpu
)->cpu_capacity
;
4854 static unsigned long capacity_orig_of(int cpu
)
4856 return cpu_rq(cpu
)->cpu_capacity_orig
;
4859 static unsigned long cpu_avg_load_per_task(int cpu
)
4861 struct rq
*rq
= cpu_rq(cpu
);
4862 unsigned long nr_running
= READ_ONCE(rq
->cfs
.h_nr_running
);
4863 unsigned long load_avg
= weighted_cpuload(cpu
);
4866 return load_avg
/ nr_running
;
4871 #ifdef CONFIG_FAIR_GROUP_SCHED
4873 * effective_load() calculates the load change as seen from the root_task_group
4875 * Adding load to a group doesn't make a group heavier, but can cause movement
4876 * of group shares between cpus. Assuming the shares were perfectly aligned one
4877 * can calculate the shift in shares.
4879 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4880 * on this @cpu and results in a total addition (subtraction) of @wg to the
4881 * total group weight.
4883 * Given a runqueue weight distribution (rw_i) we can compute a shares
4884 * distribution (s_i) using:
4886 * s_i = rw_i / \Sum rw_j (1)
4888 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4889 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4890 * shares distribution (s_i):
4892 * rw_i = { 2, 4, 1, 0 }
4893 * s_i = { 2/7, 4/7, 1/7, 0 }
4895 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4896 * task used to run on and the CPU the waker is running on), we need to
4897 * compute the effect of waking a task on either CPU and, in case of a sync
4898 * wakeup, compute the effect of the current task going to sleep.
4900 * So for a change of @wl to the local @cpu with an overall group weight change
4901 * of @wl we can compute the new shares distribution (s'_i) using:
4903 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4905 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4906 * differences in waking a task to CPU 0. The additional task changes the
4907 * weight and shares distributions like:
4909 * rw'_i = { 3, 4, 1, 0 }
4910 * s'_i = { 3/8, 4/8, 1/8, 0 }
4912 * We can then compute the difference in effective weight by using:
4914 * dw_i = S * (s'_i - s_i) (3)
4916 * Where 'S' is the group weight as seen by its parent.
4918 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4919 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4920 * 4/7) times the weight of the group.
4922 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4924 struct sched_entity
*se
= tg
->se
[cpu
];
4926 if (!tg
->parent
) /* the trivial, non-cgroup case */
4929 for_each_sched_entity(se
) {
4935 * W = @wg + \Sum rw_j
4937 W
= wg
+ calc_tg_weight(tg
, se
->my_q
);
4942 w
= cfs_rq_load_avg(se
->my_q
) + wl
;
4945 * wl = S * s'_i; see (2)
4948 wl
= (w
* (long)tg
->shares
) / W
;
4953 * Per the above, wl is the new se->load.weight value; since
4954 * those are clipped to [MIN_SHARES, ...) do so now. See
4955 * calc_cfs_shares().
4957 if (wl
< MIN_SHARES
)
4961 * wl = dw_i = S * (s'_i - s_i); see (3)
4963 wl
-= se
->avg
.load_avg
;
4966 * Recursively apply this logic to all parent groups to compute
4967 * the final effective load change on the root group. Since
4968 * only the @tg group gets extra weight, all parent groups can
4969 * only redistribute existing shares. @wl is the shift in shares
4970 * resulting from this level per the above.
4979 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4986 static void record_wakee(struct task_struct
*p
)
4989 * Only decay a single time; tasks that have less then 1 wakeup per
4990 * jiffy will not have built up many flips.
4992 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
4993 current
->wakee_flips
>>= 1;
4994 current
->wakee_flip_decay_ts
= jiffies
;
4997 if (current
->last_wakee
!= p
) {
4998 current
->last_wakee
= p
;
4999 current
->wakee_flips
++;
5004 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5006 * A waker of many should wake a different task than the one last awakened
5007 * at a frequency roughly N times higher than one of its wakees.
5009 * In order to determine whether we should let the load spread vs consolidating
5010 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5011 * partner, and a factor of lls_size higher frequency in the other.
5013 * With both conditions met, we can be relatively sure that the relationship is
5014 * non-monogamous, with partner count exceeding socket size.
5016 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5017 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5020 static int wake_wide(struct task_struct
*p
)
5022 unsigned int master
= current
->wakee_flips
;
5023 unsigned int slave
= p
->wakee_flips
;
5024 int factor
= this_cpu_read(sd_llc_size
);
5027 swap(master
, slave
);
5028 if (slave
< factor
|| master
< slave
* factor
)
5033 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
5035 s64 this_load
, load
;
5036 s64 this_eff_load
, prev_eff_load
;
5037 int idx
, this_cpu
, prev_cpu
;
5038 struct task_group
*tg
;
5039 unsigned long weight
;
5043 this_cpu
= smp_processor_id();
5044 prev_cpu
= task_cpu(p
);
5045 load
= source_load(prev_cpu
, idx
);
5046 this_load
= target_load(this_cpu
, idx
);
5049 * If sync wakeup then subtract the (maximum possible)
5050 * effect of the currently running task from the load
5051 * of the current CPU:
5054 tg
= task_group(current
);
5055 weight
= current
->se
.avg
.load_avg
;
5057 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
5058 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
5062 weight
= p
->se
.avg
.load_avg
;
5065 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5066 * due to the sync cause above having dropped this_load to 0, we'll
5067 * always have an imbalance, but there's really nothing you can do
5068 * about that, so that's good too.
5070 * Otherwise check if either cpus are near enough in load to allow this
5071 * task to be woken on this_cpu.
5073 this_eff_load
= 100;
5074 this_eff_load
*= capacity_of(prev_cpu
);
5076 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
5077 prev_eff_load
*= capacity_of(this_cpu
);
5079 if (this_load
> 0) {
5080 this_eff_load
*= this_load
+
5081 effective_load(tg
, this_cpu
, weight
, weight
);
5083 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
5086 balanced
= this_eff_load
<= prev_eff_load
;
5088 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
5093 schedstat_inc(sd
, ttwu_move_affine
);
5094 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
5100 * find_idlest_group finds and returns the least busy CPU group within the
5103 static struct sched_group
*
5104 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
5105 int this_cpu
, int sd_flag
)
5107 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
5108 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
5109 int load_idx
= sd
->forkexec_idx
;
5110 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
5112 if (sd_flag
& SD_BALANCE_WAKE
)
5113 load_idx
= sd
->wake_idx
;
5116 unsigned long load
, avg_load
;
5120 /* Skip over this group if it has no CPUs allowed */
5121 if (!cpumask_intersects(sched_group_cpus(group
),
5122 tsk_cpus_allowed(p
)))
5125 local_group
= cpumask_test_cpu(this_cpu
,
5126 sched_group_cpus(group
));
5128 /* Tally up the load of all CPUs in the group */
5131 for_each_cpu(i
, sched_group_cpus(group
)) {
5132 /* Bias balancing toward cpus of our domain */
5134 load
= source_load(i
, load_idx
);
5136 load
= target_load(i
, load_idx
);
5141 /* Adjust by relative CPU capacity of the group */
5142 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) / group
->sgc
->capacity
;
5145 this_load
= avg_load
;
5146 } else if (avg_load
< min_load
) {
5147 min_load
= avg_load
;
5150 } while (group
= group
->next
, group
!= sd
->groups
);
5152 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
5158 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5161 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5163 unsigned long load
, min_load
= ULONG_MAX
;
5164 unsigned int min_exit_latency
= UINT_MAX
;
5165 u64 latest_idle_timestamp
= 0;
5166 int least_loaded_cpu
= this_cpu
;
5167 int shallowest_idle_cpu
= -1;
5170 /* Traverse only the allowed CPUs */
5171 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
5173 struct rq
*rq
= cpu_rq(i
);
5174 struct cpuidle_state
*idle
= idle_get_state(rq
);
5175 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5177 * We give priority to a CPU whose idle state
5178 * has the smallest exit latency irrespective
5179 * of any idle timestamp.
5181 min_exit_latency
= idle
->exit_latency
;
5182 latest_idle_timestamp
= rq
->idle_stamp
;
5183 shallowest_idle_cpu
= i
;
5184 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5185 rq
->idle_stamp
> latest_idle_timestamp
) {
5187 * If equal or no active idle state, then
5188 * the most recently idled CPU might have
5191 latest_idle_timestamp
= rq
->idle_stamp
;
5192 shallowest_idle_cpu
= i
;
5194 } else if (shallowest_idle_cpu
== -1) {
5195 load
= weighted_cpuload(i
);
5196 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
5198 least_loaded_cpu
= i
;
5203 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5207 * Try and locate an idle CPU in the sched_domain.
5209 static int select_idle_sibling(struct task_struct
*p
, int target
)
5211 struct sched_domain
*sd
;
5212 struct sched_group
*sg
;
5213 int i
= task_cpu(p
);
5215 if (idle_cpu(target
))
5219 * If the prevous cpu is cache affine and idle, don't be stupid.
5221 if (i
!= target
&& cpus_share_cache(i
, target
) && idle_cpu(i
))
5225 * Otherwise, iterate the domains and find an eligible idle cpu.
5227 * A completely idle sched group at higher domains is more
5228 * desirable than an idle group at a lower level, because lower
5229 * domains have smaller groups and usually share hardware
5230 * resources which causes tasks to contend on them, e.g. x86
5231 * hyperthread siblings in the lowest domain (SMT) can contend
5232 * on the shared cpu pipeline.
5234 * However, while we prefer idle groups at higher domains
5235 * finding an idle cpu at the lowest domain is still better than
5236 * returning 'target', which we've already established, isn't
5239 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
5240 for_each_lower_domain(sd
) {
5243 if (!cpumask_intersects(sched_group_cpus(sg
),
5244 tsk_cpus_allowed(p
)))
5247 /* Ensure the entire group is idle */
5248 for_each_cpu(i
, sched_group_cpus(sg
)) {
5249 if (i
== target
|| !idle_cpu(i
))
5254 * It doesn't matter which cpu we pick, the
5255 * whole group is idle.
5257 target
= cpumask_first_and(sched_group_cpus(sg
),
5258 tsk_cpus_allowed(p
));
5262 } while (sg
!= sd
->groups
);
5269 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5270 * tasks. The unit of the return value must be the one of capacity so we can
5271 * compare the utilization with the capacity of the CPU that is available for
5272 * CFS task (ie cpu_capacity).
5274 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5275 * recent utilization of currently non-runnable tasks on a CPU. It represents
5276 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5277 * capacity_orig is the cpu_capacity available at the highest frequency
5278 * (arch_scale_freq_capacity()).
5279 * The utilization of a CPU converges towards a sum equal to or less than the
5280 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5281 * the running time on this CPU scaled by capacity_curr.
5283 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5284 * higher than capacity_orig because of unfortunate rounding in
5285 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5286 * the average stabilizes with the new running time. We need to check that the
5287 * utilization stays within the range of [0..capacity_orig] and cap it if
5288 * necessary. Without utilization capping, a group could be seen as overloaded
5289 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5290 * available capacity. We allow utilization to overshoot capacity_curr (but not
5291 * capacity_orig) as it useful for predicting the capacity required after task
5292 * migrations (scheduler-driven DVFS).
5294 static int cpu_util(int cpu
)
5296 unsigned long util
= cpu_rq(cpu
)->cfs
.avg
.util_avg
;
5297 unsigned long capacity
= capacity_orig_of(cpu
);
5299 return (util
>= capacity
) ? capacity
: util
;
5303 * select_task_rq_fair: Select target runqueue for the waking task in domains
5304 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5305 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5307 * Balances load by selecting the idlest cpu in the idlest group, or under
5308 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5310 * Returns the target cpu number.
5312 * preempt must be disabled.
5315 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
5317 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
5318 int cpu
= smp_processor_id();
5319 int new_cpu
= prev_cpu
;
5320 int want_affine
= 0;
5321 int sync
= wake_flags
& WF_SYNC
;
5323 if (sd_flag
& SD_BALANCE_WAKE
) {
5325 want_affine
= !wake_wide(p
) && cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
));
5329 for_each_domain(cpu
, tmp
) {
5330 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
5334 * If both cpu and prev_cpu are part of this domain,
5335 * cpu is a valid SD_WAKE_AFFINE target.
5337 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
5338 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
5343 if (tmp
->flags
& sd_flag
)
5345 else if (!want_affine
)
5350 sd
= NULL
; /* Prefer wake_affine over balance flags */
5351 if (cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, sync
))
5356 if (sd_flag
& SD_BALANCE_WAKE
) /* XXX always ? */
5357 new_cpu
= select_idle_sibling(p
, new_cpu
);
5360 struct sched_group
*group
;
5363 if (!(sd
->flags
& sd_flag
)) {
5368 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
5374 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
5375 if (new_cpu
== -1 || new_cpu
== cpu
) {
5376 /* Now try balancing at a lower domain level of cpu */
5381 /* Now try balancing at a lower domain level of new_cpu */
5383 weight
= sd
->span_weight
;
5385 for_each_domain(cpu
, tmp
) {
5386 if (weight
<= tmp
->span_weight
)
5388 if (tmp
->flags
& sd_flag
)
5391 /* while loop will break here if sd == NULL */
5399 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5400 * cfs_rq_of(p) references at time of call are still valid and identify the
5401 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5403 static void migrate_task_rq_fair(struct task_struct
*p
)
5406 * As blocked tasks retain absolute vruntime the migration needs to
5407 * deal with this by subtracting the old and adding the new
5408 * min_vruntime -- the latter is done by enqueue_entity() when placing
5409 * the task on the new runqueue.
5411 if (p
->state
== TASK_WAKING
) {
5412 struct sched_entity
*se
= &p
->se
;
5413 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
5416 #ifndef CONFIG_64BIT
5417 u64 min_vruntime_copy
;
5420 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
5422 min_vruntime
= cfs_rq
->min_vruntime
;
5423 } while (min_vruntime
!= min_vruntime_copy
);
5425 min_vruntime
= cfs_rq
->min_vruntime
;
5428 se
->vruntime
-= min_vruntime
;
5432 * We are supposed to update the task to "current" time, then its up to date
5433 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5434 * what current time is, so simply throw away the out-of-date time. This
5435 * will result in the wakee task is less decayed, but giving the wakee more
5436 * load sounds not bad.
5438 remove_entity_load_avg(&p
->se
);
5440 /* Tell new CPU we are migrated */
5441 p
->se
.avg
.last_update_time
= 0;
5443 /* We have migrated, no longer consider this task hot */
5444 p
->se
.exec_start
= 0;
5447 static void task_dead_fair(struct task_struct
*p
)
5449 remove_entity_load_avg(&p
->se
);
5451 #endif /* CONFIG_SMP */
5453 static unsigned long
5454 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
5456 unsigned long gran
= sysctl_sched_wakeup_granularity
;
5459 * Since its curr running now, convert the gran from real-time
5460 * to virtual-time in his units.
5462 * By using 'se' instead of 'curr' we penalize light tasks, so
5463 * they get preempted easier. That is, if 'se' < 'curr' then
5464 * the resulting gran will be larger, therefore penalizing the
5465 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5466 * be smaller, again penalizing the lighter task.
5468 * This is especially important for buddies when the leftmost
5469 * task is higher priority than the buddy.
5471 return calc_delta_fair(gran
, se
);
5475 * Should 'se' preempt 'curr'.
5489 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
5491 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
5496 gran
= wakeup_gran(curr
, se
);
5503 static void set_last_buddy(struct sched_entity
*se
)
5505 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5508 for_each_sched_entity(se
)
5509 cfs_rq_of(se
)->last
= se
;
5512 static void set_next_buddy(struct sched_entity
*se
)
5514 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5517 for_each_sched_entity(se
)
5518 cfs_rq_of(se
)->next
= se
;
5521 static void set_skip_buddy(struct sched_entity
*se
)
5523 for_each_sched_entity(se
)
5524 cfs_rq_of(se
)->skip
= se
;
5528 * Preempt the current task with a newly woken task if needed:
5530 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
5532 struct task_struct
*curr
= rq
->curr
;
5533 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
5534 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5535 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
5536 int next_buddy_marked
= 0;
5538 if (unlikely(se
== pse
))
5542 * This is possible from callers such as attach_tasks(), in which we
5543 * unconditionally check_prempt_curr() after an enqueue (which may have
5544 * lead to a throttle). This both saves work and prevents false
5545 * next-buddy nomination below.
5547 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
5550 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
5551 set_next_buddy(pse
);
5552 next_buddy_marked
= 1;
5556 * We can come here with TIF_NEED_RESCHED already set from new task
5559 * Note: this also catches the edge-case of curr being in a throttled
5560 * group (e.g. via set_curr_task), since update_curr() (in the
5561 * enqueue of curr) will have resulted in resched being set. This
5562 * prevents us from potentially nominating it as a false LAST_BUDDY
5565 if (test_tsk_need_resched(curr
))
5568 /* Idle tasks are by definition preempted by non-idle tasks. */
5569 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
5570 likely(p
->policy
!= SCHED_IDLE
))
5574 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5575 * is driven by the tick):
5577 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
5580 find_matching_se(&se
, &pse
);
5581 update_curr(cfs_rq_of(se
));
5583 if (wakeup_preempt_entity(se
, pse
) == 1) {
5585 * Bias pick_next to pick the sched entity that is
5586 * triggering this preemption.
5588 if (!next_buddy_marked
)
5589 set_next_buddy(pse
);
5598 * Only set the backward buddy when the current task is still
5599 * on the rq. This can happen when a wakeup gets interleaved
5600 * with schedule on the ->pre_schedule() or idle_balance()
5601 * point, either of which can * drop the rq lock.
5603 * Also, during early boot the idle thread is in the fair class,
5604 * for obvious reasons its a bad idea to schedule back to it.
5606 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
5609 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
5613 static struct task_struct
*
5614 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
, struct pin_cookie cookie
)
5616 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
5617 struct sched_entity
*se
;
5618 struct task_struct
*p
;
5622 #ifdef CONFIG_FAIR_GROUP_SCHED
5623 if (!cfs_rq
->nr_running
)
5626 if (prev
->sched_class
!= &fair_sched_class
)
5630 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5631 * likely that a next task is from the same cgroup as the current.
5633 * Therefore attempt to avoid putting and setting the entire cgroup
5634 * hierarchy, only change the part that actually changes.
5638 struct sched_entity
*curr
= cfs_rq
->curr
;
5641 * Since we got here without doing put_prev_entity() we also
5642 * have to consider cfs_rq->curr. If it is still a runnable
5643 * entity, update_curr() will update its vruntime, otherwise
5644 * forget we've ever seen it.
5648 update_curr(cfs_rq
);
5653 * This call to check_cfs_rq_runtime() will do the
5654 * throttle and dequeue its entity in the parent(s).
5655 * Therefore the 'simple' nr_running test will indeed
5658 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
5662 se
= pick_next_entity(cfs_rq
, curr
);
5663 cfs_rq
= group_cfs_rq(se
);
5669 * Since we haven't yet done put_prev_entity and if the selected task
5670 * is a different task than we started out with, try and touch the
5671 * least amount of cfs_rqs.
5674 struct sched_entity
*pse
= &prev
->se
;
5676 while (!(cfs_rq
= is_same_group(se
, pse
))) {
5677 int se_depth
= se
->depth
;
5678 int pse_depth
= pse
->depth
;
5680 if (se_depth
<= pse_depth
) {
5681 put_prev_entity(cfs_rq_of(pse
), pse
);
5682 pse
= parent_entity(pse
);
5684 if (se_depth
>= pse_depth
) {
5685 set_next_entity(cfs_rq_of(se
), se
);
5686 se
= parent_entity(se
);
5690 put_prev_entity(cfs_rq
, pse
);
5691 set_next_entity(cfs_rq
, se
);
5694 if (hrtick_enabled(rq
))
5695 hrtick_start_fair(rq
, p
);
5702 if (!cfs_rq
->nr_running
)
5705 put_prev_task(rq
, prev
);
5708 se
= pick_next_entity(cfs_rq
, NULL
);
5709 set_next_entity(cfs_rq
, se
);
5710 cfs_rq
= group_cfs_rq(se
);
5715 if (hrtick_enabled(rq
))
5716 hrtick_start_fair(rq
, p
);
5722 * This is OK, because current is on_cpu, which avoids it being picked
5723 * for load-balance and preemption/IRQs are still disabled avoiding
5724 * further scheduler activity on it and we're being very careful to
5725 * re-start the picking loop.
5727 lockdep_unpin_lock(&rq
->lock
, cookie
);
5728 new_tasks
= idle_balance(rq
);
5729 lockdep_repin_lock(&rq
->lock
, cookie
);
5731 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5732 * possible for any higher priority task to appear. In that case we
5733 * must re-start the pick_next_entity() loop.
5745 * Account for a descheduled task:
5747 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5749 struct sched_entity
*se
= &prev
->se
;
5750 struct cfs_rq
*cfs_rq
;
5752 for_each_sched_entity(se
) {
5753 cfs_rq
= cfs_rq_of(se
);
5754 put_prev_entity(cfs_rq
, se
);
5759 * sched_yield() is very simple
5761 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5763 static void yield_task_fair(struct rq
*rq
)
5765 struct task_struct
*curr
= rq
->curr
;
5766 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5767 struct sched_entity
*se
= &curr
->se
;
5770 * Are we the only task in the tree?
5772 if (unlikely(rq
->nr_running
== 1))
5775 clear_buddies(cfs_rq
, se
);
5777 if (curr
->policy
!= SCHED_BATCH
) {
5778 update_rq_clock(rq
);
5780 * Update run-time statistics of the 'current'.
5782 update_curr(cfs_rq
);
5784 * Tell update_rq_clock() that we've just updated,
5785 * so we don't do microscopic update in schedule()
5786 * and double the fastpath cost.
5788 rq_clock_skip_update(rq
, true);
5794 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
5796 struct sched_entity
*se
= &p
->se
;
5798 /* throttled hierarchies are not runnable */
5799 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
5802 /* Tell the scheduler that we'd really like pse to run next. */
5805 yield_task_fair(rq
);
5811 /**************************************************
5812 * Fair scheduling class load-balancing methods.
5816 * The purpose of load-balancing is to achieve the same basic fairness the
5817 * per-cpu scheduler provides, namely provide a proportional amount of compute
5818 * time to each task. This is expressed in the following equation:
5820 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5822 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5823 * W_i,0 is defined as:
5825 * W_i,0 = \Sum_j w_i,j (2)
5827 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5828 * is derived from the nice value as per sched_prio_to_weight[].
5830 * The weight average is an exponential decay average of the instantaneous
5833 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5835 * C_i is the compute capacity of cpu i, typically it is the
5836 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5837 * can also include other factors [XXX].
5839 * To achieve this balance we define a measure of imbalance which follows
5840 * directly from (1):
5842 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5844 * We them move tasks around to minimize the imbalance. In the continuous
5845 * function space it is obvious this converges, in the discrete case we get
5846 * a few fun cases generally called infeasible weight scenarios.
5849 * - infeasible weights;
5850 * - local vs global optima in the discrete case. ]
5855 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5856 * for all i,j solution, we create a tree of cpus that follows the hardware
5857 * topology where each level pairs two lower groups (or better). This results
5858 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5859 * tree to only the first of the previous level and we decrease the frequency
5860 * of load-balance at each level inv. proportional to the number of cpus in
5866 * \Sum { --- * --- * 2^i } = O(n) (5)
5868 * `- size of each group
5869 * | | `- number of cpus doing load-balance
5871 * `- sum over all levels
5873 * Coupled with a limit on how many tasks we can migrate every balance pass,
5874 * this makes (5) the runtime complexity of the balancer.
5876 * An important property here is that each CPU is still (indirectly) connected
5877 * to every other cpu in at most O(log n) steps:
5879 * The adjacency matrix of the resulting graph is given by:
5882 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5885 * And you'll find that:
5887 * A^(log_2 n)_i,j != 0 for all i,j (7)
5889 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5890 * The task movement gives a factor of O(m), giving a convergence complexity
5893 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5898 * In order to avoid CPUs going idle while there's still work to do, new idle
5899 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5900 * tree itself instead of relying on other CPUs to bring it work.
5902 * This adds some complexity to both (5) and (8) but it reduces the total idle
5910 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5913 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5918 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5920 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5922 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5925 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5926 * rewrite all of this once again.]
5929 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
5931 enum fbq_type
{ regular
, remote
, all
};
5933 #define LBF_ALL_PINNED 0x01
5934 #define LBF_NEED_BREAK 0x02
5935 #define LBF_DST_PINNED 0x04
5936 #define LBF_SOME_PINNED 0x08
5939 struct sched_domain
*sd
;
5947 struct cpumask
*dst_grpmask
;
5949 enum cpu_idle_type idle
;
5951 /* The set of CPUs under consideration for load-balancing */
5952 struct cpumask
*cpus
;
5957 unsigned int loop_break
;
5958 unsigned int loop_max
;
5960 enum fbq_type fbq_type
;
5961 struct list_head tasks
;
5965 * Is this task likely cache-hot:
5967 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
5971 lockdep_assert_held(&env
->src_rq
->lock
);
5973 if (p
->sched_class
!= &fair_sched_class
)
5976 if (unlikely(p
->policy
== SCHED_IDLE
))
5980 * Buddy candidates are cache hot:
5982 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
5983 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
5984 &p
->se
== cfs_rq_of(&p
->se
)->last
))
5987 if (sysctl_sched_migration_cost
== -1)
5989 if (sysctl_sched_migration_cost
== 0)
5992 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
5994 return delta
< (s64
)sysctl_sched_migration_cost
;
5997 #ifdef CONFIG_NUMA_BALANCING
5999 * Returns 1, if task migration degrades locality
6000 * Returns 0, if task migration improves locality i.e migration preferred.
6001 * Returns -1, if task migration is not affected by locality.
6003 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
6005 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
6006 unsigned long src_faults
, dst_faults
;
6007 int src_nid
, dst_nid
;
6009 if (!static_branch_likely(&sched_numa_balancing
))
6012 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
6015 src_nid
= cpu_to_node(env
->src_cpu
);
6016 dst_nid
= cpu_to_node(env
->dst_cpu
);
6018 if (src_nid
== dst_nid
)
6021 /* Migrating away from the preferred node is always bad. */
6022 if (src_nid
== p
->numa_preferred_nid
) {
6023 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
6029 /* Encourage migration to the preferred node. */
6030 if (dst_nid
== p
->numa_preferred_nid
)
6034 src_faults
= group_faults(p
, src_nid
);
6035 dst_faults
= group_faults(p
, dst_nid
);
6037 src_faults
= task_faults(p
, src_nid
);
6038 dst_faults
= task_faults(p
, dst_nid
);
6041 return dst_faults
< src_faults
;
6045 static inline int migrate_degrades_locality(struct task_struct
*p
,
6053 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6056 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
6060 lockdep_assert_held(&env
->src_rq
->lock
);
6063 * We do not migrate tasks that are:
6064 * 1) throttled_lb_pair, or
6065 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6066 * 3) running (obviously), or
6067 * 4) are cache-hot on their current CPU.
6069 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
6072 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
6075 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
6077 env
->flags
|= LBF_SOME_PINNED
;
6080 * Remember if this task can be migrated to any other cpu in
6081 * our sched_group. We may want to revisit it if we couldn't
6082 * meet load balance goals by pulling other tasks on src_cpu.
6084 * Also avoid computing new_dst_cpu if we have already computed
6085 * one in current iteration.
6087 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
6090 /* Prevent to re-select dst_cpu via env's cpus */
6091 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
6092 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
6093 env
->flags
|= LBF_DST_PINNED
;
6094 env
->new_dst_cpu
= cpu
;
6102 /* Record that we found atleast one task that could run on dst_cpu */
6103 env
->flags
&= ~LBF_ALL_PINNED
;
6105 if (task_running(env
->src_rq
, p
)) {
6106 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
6111 * Aggressive migration if:
6112 * 1) destination numa is preferred
6113 * 2) task is cache cold, or
6114 * 3) too many balance attempts have failed.
6116 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
6117 if (tsk_cache_hot
== -1)
6118 tsk_cache_hot
= task_hot(p
, env
);
6120 if (tsk_cache_hot
<= 0 ||
6121 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
6122 if (tsk_cache_hot
== 1) {
6123 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
6124 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
6129 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
6134 * detach_task() -- detach the task for the migration specified in env
6136 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
6138 lockdep_assert_held(&env
->src_rq
->lock
);
6140 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
6141 deactivate_task(env
->src_rq
, p
, 0);
6142 set_task_cpu(p
, env
->dst_cpu
);
6146 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6147 * part of active balancing operations within "domain".
6149 * Returns a task if successful and NULL otherwise.
6151 static struct task_struct
*detach_one_task(struct lb_env
*env
)
6153 struct task_struct
*p
, *n
;
6155 lockdep_assert_held(&env
->src_rq
->lock
);
6157 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
6158 if (!can_migrate_task(p
, env
))
6161 detach_task(p
, env
);
6164 * Right now, this is only the second place where
6165 * lb_gained[env->idle] is updated (other is detach_tasks)
6166 * so we can safely collect stats here rather than
6167 * inside detach_tasks().
6169 schedstat_inc(env
->sd
, lb_gained
[env
->idle
]);
6175 static const unsigned int sched_nr_migrate_break
= 32;
6178 * detach_tasks() -- tries to detach up to imbalance weighted load from
6179 * busiest_rq, as part of a balancing operation within domain "sd".
6181 * Returns number of detached tasks if successful and 0 otherwise.
6183 static int detach_tasks(struct lb_env
*env
)
6185 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
6186 struct task_struct
*p
;
6190 lockdep_assert_held(&env
->src_rq
->lock
);
6192 if (env
->imbalance
<= 0)
6195 while (!list_empty(tasks
)) {
6197 * We don't want to steal all, otherwise we may be treated likewise,
6198 * which could at worst lead to a livelock crash.
6200 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
6203 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6206 /* We've more or less seen every task there is, call it quits */
6207 if (env
->loop
> env
->loop_max
)
6210 /* take a breather every nr_migrate tasks */
6211 if (env
->loop
> env
->loop_break
) {
6212 env
->loop_break
+= sched_nr_migrate_break
;
6213 env
->flags
|= LBF_NEED_BREAK
;
6217 if (!can_migrate_task(p
, env
))
6220 load
= task_h_load(p
);
6222 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
6225 if ((load
/ 2) > env
->imbalance
)
6228 detach_task(p
, env
);
6229 list_add(&p
->se
.group_node
, &env
->tasks
);
6232 env
->imbalance
-= load
;
6234 #ifdef CONFIG_PREEMPT
6236 * NEWIDLE balancing is a source of latency, so preemptible
6237 * kernels will stop after the first task is detached to minimize
6238 * the critical section.
6240 if (env
->idle
== CPU_NEWLY_IDLE
)
6245 * We only want to steal up to the prescribed amount of
6248 if (env
->imbalance
<= 0)
6253 list_move_tail(&p
->se
.group_node
, tasks
);
6257 * Right now, this is one of only two places we collect this stat
6258 * so we can safely collect detach_one_task() stats here rather
6259 * than inside detach_one_task().
6261 schedstat_add(env
->sd
, lb_gained
[env
->idle
], detached
);
6267 * attach_task() -- attach the task detached by detach_task() to its new rq.
6269 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
6271 lockdep_assert_held(&rq
->lock
);
6273 BUG_ON(task_rq(p
) != rq
);
6274 activate_task(rq
, p
, 0);
6275 p
->on_rq
= TASK_ON_RQ_QUEUED
;
6276 check_preempt_curr(rq
, p
, 0);
6280 * attach_one_task() -- attaches the task returned from detach_one_task() to
6283 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
6285 raw_spin_lock(&rq
->lock
);
6287 raw_spin_unlock(&rq
->lock
);
6291 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6294 static void attach_tasks(struct lb_env
*env
)
6296 struct list_head
*tasks
= &env
->tasks
;
6297 struct task_struct
*p
;
6299 raw_spin_lock(&env
->dst_rq
->lock
);
6301 while (!list_empty(tasks
)) {
6302 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6303 list_del_init(&p
->se
.group_node
);
6305 attach_task(env
->dst_rq
, p
);
6308 raw_spin_unlock(&env
->dst_rq
->lock
);
6311 #ifdef CONFIG_FAIR_GROUP_SCHED
6312 static void update_blocked_averages(int cpu
)
6314 struct rq
*rq
= cpu_rq(cpu
);
6315 struct cfs_rq
*cfs_rq
;
6316 unsigned long flags
;
6318 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6319 update_rq_clock(rq
);
6322 * Iterates the task_group tree in a bottom up fashion, see
6323 * list_add_leaf_cfs_rq() for details.
6325 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
6326 /* throttled entities do not contribute to load */
6327 if (throttled_hierarchy(cfs_rq
))
6330 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true))
6331 update_tg_load_avg(cfs_rq
, 0);
6333 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6337 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6338 * This needs to be done in a top-down fashion because the load of a child
6339 * group is a fraction of its parents load.
6341 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
6343 struct rq
*rq
= rq_of(cfs_rq
);
6344 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
6345 unsigned long now
= jiffies
;
6348 if (cfs_rq
->last_h_load_update
== now
)
6351 cfs_rq
->h_load_next
= NULL
;
6352 for_each_sched_entity(se
) {
6353 cfs_rq
= cfs_rq_of(se
);
6354 cfs_rq
->h_load_next
= se
;
6355 if (cfs_rq
->last_h_load_update
== now
)
6360 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
6361 cfs_rq
->last_h_load_update
= now
;
6364 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
6365 load
= cfs_rq
->h_load
;
6366 load
= div64_ul(load
* se
->avg
.load_avg
,
6367 cfs_rq_load_avg(cfs_rq
) + 1);
6368 cfs_rq
= group_cfs_rq(se
);
6369 cfs_rq
->h_load
= load
;
6370 cfs_rq
->last_h_load_update
= now
;
6374 static unsigned long task_h_load(struct task_struct
*p
)
6376 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
6378 update_cfs_rq_h_load(cfs_rq
);
6379 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
6380 cfs_rq_load_avg(cfs_rq
) + 1);
6383 static inline void update_blocked_averages(int cpu
)
6385 struct rq
*rq
= cpu_rq(cpu
);
6386 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
6387 unsigned long flags
;
6389 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6390 update_rq_clock(rq
);
6391 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true);
6392 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6395 static unsigned long task_h_load(struct task_struct
*p
)
6397 return p
->se
.avg
.load_avg
;
6401 /********** Helpers for find_busiest_group ************************/
6410 * sg_lb_stats - stats of a sched_group required for load_balancing
6412 struct sg_lb_stats
{
6413 unsigned long avg_load
; /*Avg load across the CPUs of the group */
6414 unsigned long group_load
; /* Total load over the CPUs of the group */
6415 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
6416 unsigned long load_per_task
;
6417 unsigned long group_capacity
;
6418 unsigned long group_util
; /* Total utilization of the group */
6419 unsigned int sum_nr_running
; /* Nr tasks running in the group */
6420 unsigned int idle_cpus
;
6421 unsigned int group_weight
;
6422 enum group_type group_type
;
6423 int group_no_capacity
;
6424 #ifdef CONFIG_NUMA_BALANCING
6425 unsigned int nr_numa_running
;
6426 unsigned int nr_preferred_running
;
6431 * sd_lb_stats - Structure to store the statistics of a sched_domain
6432 * during load balancing.
6434 struct sd_lb_stats
{
6435 struct sched_group
*busiest
; /* Busiest group in this sd */
6436 struct sched_group
*local
; /* Local group in this sd */
6437 unsigned long total_load
; /* Total load of all groups in sd */
6438 unsigned long total_capacity
; /* Total capacity of all groups in sd */
6439 unsigned long avg_load
; /* Average load across all groups in sd */
6441 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
6442 struct sg_lb_stats local_stat
; /* Statistics of the local group */
6445 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
6448 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6449 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6450 * We must however clear busiest_stat::avg_load because
6451 * update_sd_pick_busiest() reads this before assignment.
6453 *sds
= (struct sd_lb_stats
){
6457 .total_capacity
= 0UL,
6460 .sum_nr_running
= 0,
6461 .group_type
= group_other
,
6467 * get_sd_load_idx - Obtain the load index for a given sched domain.
6468 * @sd: The sched_domain whose load_idx is to be obtained.
6469 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6471 * Return: The load index.
6473 static inline int get_sd_load_idx(struct sched_domain
*sd
,
6474 enum cpu_idle_type idle
)
6480 load_idx
= sd
->busy_idx
;
6483 case CPU_NEWLY_IDLE
:
6484 load_idx
= sd
->newidle_idx
;
6487 load_idx
= sd
->idle_idx
;
6494 static unsigned long scale_rt_capacity(int cpu
)
6496 struct rq
*rq
= cpu_rq(cpu
);
6497 u64 total
, used
, age_stamp
, avg
;
6501 * Since we're reading these variables without serialization make sure
6502 * we read them once before doing sanity checks on them.
6504 age_stamp
= READ_ONCE(rq
->age_stamp
);
6505 avg
= READ_ONCE(rq
->rt_avg
);
6506 delta
= __rq_clock_broken(rq
) - age_stamp
;
6508 if (unlikely(delta
< 0))
6511 total
= sched_avg_period() + delta
;
6513 used
= div_u64(avg
, total
);
6515 if (likely(used
< SCHED_CAPACITY_SCALE
))
6516 return SCHED_CAPACITY_SCALE
- used
;
6521 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
6523 unsigned long capacity
= arch_scale_cpu_capacity(sd
, cpu
);
6524 struct sched_group
*sdg
= sd
->groups
;
6526 cpu_rq(cpu
)->cpu_capacity_orig
= capacity
;
6528 capacity
*= scale_rt_capacity(cpu
);
6529 capacity
>>= SCHED_CAPACITY_SHIFT
;
6534 cpu_rq(cpu
)->cpu_capacity
= capacity
;
6535 sdg
->sgc
->capacity
= capacity
;
6538 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
6540 struct sched_domain
*child
= sd
->child
;
6541 struct sched_group
*group
, *sdg
= sd
->groups
;
6542 unsigned long capacity
;
6543 unsigned long interval
;
6545 interval
= msecs_to_jiffies(sd
->balance_interval
);
6546 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
6547 sdg
->sgc
->next_update
= jiffies
+ interval
;
6550 update_cpu_capacity(sd
, cpu
);
6556 if (child
->flags
& SD_OVERLAP
) {
6558 * SD_OVERLAP domains cannot assume that child groups
6559 * span the current group.
6562 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
6563 struct sched_group_capacity
*sgc
;
6564 struct rq
*rq
= cpu_rq(cpu
);
6567 * build_sched_domains() -> init_sched_groups_capacity()
6568 * gets here before we've attached the domains to the
6571 * Use capacity_of(), which is set irrespective of domains
6572 * in update_cpu_capacity().
6574 * This avoids capacity from being 0 and
6575 * causing divide-by-zero issues on boot.
6577 if (unlikely(!rq
->sd
)) {
6578 capacity
+= capacity_of(cpu
);
6582 sgc
= rq
->sd
->groups
->sgc
;
6583 capacity
+= sgc
->capacity
;
6587 * !SD_OVERLAP domains can assume that child groups
6588 * span the current group.
6591 group
= child
->groups
;
6593 capacity
+= group
->sgc
->capacity
;
6594 group
= group
->next
;
6595 } while (group
!= child
->groups
);
6598 sdg
->sgc
->capacity
= capacity
;
6602 * Check whether the capacity of the rq has been noticeably reduced by side
6603 * activity. The imbalance_pct is used for the threshold.
6604 * Return true is the capacity is reduced
6607 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
6609 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
6610 (rq
->cpu_capacity_orig
* 100));
6614 * Group imbalance indicates (and tries to solve) the problem where balancing
6615 * groups is inadequate due to tsk_cpus_allowed() constraints.
6617 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6618 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6621 * { 0 1 2 3 } { 4 5 6 7 }
6624 * If we were to balance group-wise we'd place two tasks in the first group and
6625 * two tasks in the second group. Clearly this is undesired as it will overload
6626 * cpu 3 and leave one of the cpus in the second group unused.
6628 * The current solution to this issue is detecting the skew in the first group
6629 * by noticing the lower domain failed to reach balance and had difficulty
6630 * moving tasks due to affinity constraints.
6632 * When this is so detected; this group becomes a candidate for busiest; see
6633 * update_sd_pick_busiest(). And calculate_imbalance() and
6634 * find_busiest_group() avoid some of the usual balance conditions to allow it
6635 * to create an effective group imbalance.
6637 * This is a somewhat tricky proposition since the next run might not find the
6638 * group imbalance and decide the groups need to be balanced again. A most
6639 * subtle and fragile situation.
6642 static inline int sg_imbalanced(struct sched_group
*group
)
6644 return group
->sgc
->imbalance
;
6648 * group_has_capacity returns true if the group has spare capacity that could
6649 * be used by some tasks.
6650 * We consider that a group has spare capacity if the * number of task is
6651 * smaller than the number of CPUs or if the utilization is lower than the
6652 * available capacity for CFS tasks.
6653 * For the latter, we use a threshold to stabilize the state, to take into
6654 * account the variance of the tasks' load and to return true if the available
6655 * capacity in meaningful for the load balancer.
6656 * As an example, an available capacity of 1% can appear but it doesn't make
6657 * any benefit for the load balance.
6660 group_has_capacity(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6662 if (sgs
->sum_nr_running
< sgs
->group_weight
)
6665 if ((sgs
->group_capacity
* 100) >
6666 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6673 * group_is_overloaded returns true if the group has more tasks than it can
6675 * group_is_overloaded is not equals to !group_has_capacity because a group
6676 * with the exact right number of tasks, has no more spare capacity but is not
6677 * overloaded so both group_has_capacity and group_is_overloaded return
6681 group_is_overloaded(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6683 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
6686 if ((sgs
->group_capacity
* 100) <
6687 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6694 group_type
group_classify(struct sched_group
*group
,
6695 struct sg_lb_stats
*sgs
)
6697 if (sgs
->group_no_capacity
)
6698 return group_overloaded
;
6700 if (sg_imbalanced(group
))
6701 return group_imbalanced
;
6707 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6708 * @env: The load balancing environment.
6709 * @group: sched_group whose statistics are to be updated.
6710 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6711 * @local_group: Does group contain this_cpu.
6712 * @sgs: variable to hold the statistics for this group.
6713 * @overload: Indicate more than one runnable task for any CPU.
6715 static inline void update_sg_lb_stats(struct lb_env
*env
,
6716 struct sched_group
*group
, int load_idx
,
6717 int local_group
, struct sg_lb_stats
*sgs
,
6723 memset(sgs
, 0, sizeof(*sgs
));
6725 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6726 struct rq
*rq
= cpu_rq(i
);
6728 /* Bias balancing toward cpus of our domain */
6730 load
= target_load(i
, load_idx
);
6732 load
= source_load(i
, load_idx
);
6734 sgs
->group_load
+= load
;
6735 sgs
->group_util
+= cpu_util(i
);
6736 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
6738 nr_running
= rq
->nr_running
;
6742 #ifdef CONFIG_NUMA_BALANCING
6743 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
6744 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
6746 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
6748 * No need to call idle_cpu() if nr_running is not 0
6750 if (!nr_running
&& idle_cpu(i
))
6754 /* Adjust by relative CPU capacity of the group */
6755 sgs
->group_capacity
= group
->sgc
->capacity
;
6756 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
6758 if (sgs
->sum_nr_running
)
6759 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
6761 sgs
->group_weight
= group
->group_weight
;
6763 sgs
->group_no_capacity
= group_is_overloaded(env
, sgs
);
6764 sgs
->group_type
= group_classify(group
, sgs
);
6768 * update_sd_pick_busiest - return 1 on busiest group
6769 * @env: The load balancing environment.
6770 * @sds: sched_domain statistics
6771 * @sg: sched_group candidate to be checked for being the busiest
6772 * @sgs: sched_group statistics
6774 * Determine if @sg is a busier group than the previously selected
6777 * Return: %true if @sg is a busier group than the previously selected
6778 * busiest group. %false otherwise.
6780 static bool update_sd_pick_busiest(struct lb_env
*env
,
6781 struct sd_lb_stats
*sds
,
6782 struct sched_group
*sg
,
6783 struct sg_lb_stats
*sgs
)
6785 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
6787 if (sgs
->group_type
> busiest
->group_type
)
6790 if (sgs
->group_type
< busiest
->group_type
)
6793 if (sgs
->avg_load
<= busiest
->avg_load
)
6796 /* This is the busiest node in its class. */
6797 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6800 /* No ASYM_PACKING if target cpu is already busy */
6801 if (env
->idle
== CPU_NOT_IDLE
)
6804 * ASYM_PACKING needs to move all the work to the lowest
6805 * numbered CPUs in the group, therefore mark all groups
6806 * higher than ourself as busy.
6808 if (sgs
->sum_nr_running
&& env
->dst_cpu
< group_first_cpu(sg
)) {
6812 /* Prefer to move from highest possible cpu's work */
6813 if (group_first_cpu(sds
->busiest
) < group_first_cpu(sg
))
6820 #ifdef CONFIG_NUMA_BALANCING
6821 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6823 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
6825 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
6830 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6832 if (rq
->nr_running
> rq
->nr_numa_running
)
6834 if (rq
->nr_running
> rq
->nr_preferred_running
)
6839 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6844 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6848 #endif /* CONFIG_NUMA_BALANCING */
6851 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6852 * @env: The load balancing environment.
6853 * @sds: variable to hold the statistics for this sched_domain.
6855 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6857 struct sched_domain
*child
= env
->sd
->child
;
6858 struct sched_group
*sg
= env
->sd
->groups
;
6859 struct sg_lb_stats tmp_sgs
;
6860 int load_idx
, prefer_sibling
= 0;
6861 bool overload
= false;
6863 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
6866 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
6869 struct sg_lb_stats
*sgs
= &tmp_sgs
;
6872 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
6875 sgs
= &sds
->local_stat
;
6877 if (env
->idle
!= CPU_NEWLY_IDLE
||
6878 time_after_eq(jiffies
, sg
->sgc
->next_update
))
6879 update_group_capacity(env
->sd
, env
->dst_cpu
);
6882 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
6889 * In case the child domain prefers tasks go to siblings
6890 * first, lower the sg capacity so that we'll try
6891 * and move all the excess tasks away. We lower the capacity
6892 * of a group only if the local group has the capacity to fit
6893 * these excess tasks. The extra check prevents the case where
6894 * you always pull from the heaviest group when it is already
6895 * under-utilized (possible with a large weight task outweighs
6896 * the tasks on the system).
6898 if (prefer_sibling
&& sds
->local
&&
6899 group_has_capacity(env
, &sds
->local_stat
) &&
6900 (sgs
->sum_nr_running
> 1)) {
6901 sgs
->group_no_capacity
= 1;
6902 sgs
->group_type
= group_classify(sg
, sgs
);
6905 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
6907 sds
->busiest_stat
= *sgs
;
6911 /* Now, start updating sd_lb_stats */
6912 sds
->total_load
+= sgs
->group_load
;
6913 sds
->total_capacity
+= sgs
->group_capacity
;
6916 } while (sg
!= env
->sd
->groups
);
6918 if (env
->sd
->flags
& SD_NUMA
)
6919 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
6921 if (!env
->sd
->parent
) {
6922 /* update overload indicator if we are at root domain */
6923 if (env
->dst_rq
->rd
->overload
!= overload
)
6924 env
->dst_rq
->rd
->overload
= overload
;
6930 * check_asym_packing - Check to see if the group is packed into the
6933 * This is primarily intended to used at the sibling level. Some
6934 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6935 * case of POWER7, it can move to lower SMT modes only when higher
6936 * threads are idle. When in lower SMT modes, the threads will
6937 * perform better since they share less core resources. Hence when we
6938 * have idle threads, we want them to be the higher ones.
6940 * This packing function is run on idle threads. It checks to see if
6941 * the busiest CPU in this domain (core in the P7 case) has a higher
6942 * CPU number than the packing function is being run on. Here we are
6943 * assuming lower CPU number will be equivalent to lower a SMT thread
6946 * Return: 1 when packing is required and a task should be moved to
6947 * this CPU. The amount of the imbalance is returned in *imbalance.
6949 * @env: The load balancing environment.
6950 * @sds: Statistics of the sched_domain which is to be packed
6952 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6956 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6959 if (env
->idle
== CPU_NOT_IDLE
)
6965 busiest_cpu
= group_first_cpu(sds
->busiest
);
6966 if (env
->dst_cpu
> busiest_cpu
)
6969 env
->imbalance
= DIV_ROUND_CLOSEST(
6970 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
6971 SCHED_CAPACITY_SCALE
);
6977 * fix_small_imbalance - Calculate the minor imbalance that exists
6978 * amongst the groups of a sched_domain, during
6980 * @env: The load balancing environment.
6981 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6984 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6986 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
6987 unsigned int imbn
= 2;
6988 unsigned long scaled_busy_load_per_task
;
6989 struct sg_lb_stats
*local
, *busiest
;
6991 local
= &sds
->local_stat
;
6992 busiest
= &sds
->busiest_stat
;
6994 if (!local
->sum_nr_running
)
6995 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
6996 else if (busiest
->load_per_task
> local
->load_per_task
)
6999 scaled_busy_load_per_task
=
7000 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7001 busiest
->group_capacity
;
7003 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
7004 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
7005 env
->imbalance
= busiest
->load_per_task
;
7010 * OK, we don't have enough imbalance to justify moving tasks,
7011 * however we may be able to increase total CPU capacity used by
7015 capa_now
+= busiest
->group_capacity
*
7016 min(busiest
->load_per_task
, busiest
->avg_load
);
7017 capa_now
+= local
->group_capacity
*
7018 min(local
->load_per_task
, local
->avg_load
);
7019 capa_now
/= SCHED_CAPACITY_SCALE
;
7021 /* Amount of load we'd subtract */
7022 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
7023 capa_move
+= busiest
->group_capacity
*
7024 min(busiest
->load_per_task
,
7025 busiest
->avg_load
- scaled_busy_load_per_task
);
7028 /* Amount of load we'd add */
7029 if (busiest
->avg_load
* busiest
->group_capacity
<
7030 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
7031 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
7032 local
->group_capacity
;
7034 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7035 local
->group_capacity
;
7037 capa_move
+= local
->group_capacity
*
7038 min(local
->load_per_task
, local
->avg_load
+ tmp
);
7039 capa_move
/= SCHED_CAPACITY_SCALE
;
7041 /* Move if we gain throughput */
7042 if (capa_move
> capa_now
)
7043 env
->imbalance
= busiest
->load_per_task
;
7047 * calculate_imbalance - Calculate the amount of imbalance present within the
7048 * groups of a given sched_domain during load balance.
7049 * @env: load balance environment
7050 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7052 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7054 unsigned long max_pull
, load_above_capacity
= ~0UL;
7055 struct sg_lb_stats
*local
, *busiest
;
7057 local
= &sds
->local_stat
;
7058 busiest
= &sds
->busiest_stat
;
7060 if (busiest
->group_type
== group_imbalanced
) {
7062 * In the group_imb case we cannot rely on group-wide averages
7063 * to ensure cpu-load equilibrium, look at wider averages. XXX
7065 busiest
->load_per_task
=
7066 min(busiest
->load_per_task
, sds
->avg_load
);
7070 * Avg load of busiest sg can be less and avg load of local sg can
7071 * be greater than avg load across all sgs of sd because avg load
7072 * factors in sg capacity and sgs with smaller group_type are
7073 * skipped when updating the busiest sg:
7075 if (busiest
->avg_load
<= sds
->avg_load
||
7076 local
->avg_load
>= sds
->avg_load
) {
7078 return fix_small_imbalance(env
, sds
);
7082 * If there aren't any idle cpus, avoid creating some.
7084 if (busiest
->group_type
== group_overloaded
&&
7085 local
->group_type
== group_overloaded
) {
7086 load_above_capacity
= busiest
->sum_nr_running
* SCHED_CAPACITY_SCALE
;
7087 if (load_above_capacity
> busiest
->group_capacity
) {
7088 load_above_capacity
-= busiest
->group_capacity
;
7089 load_above_capacity
*= NICE_0_LOAD
;
7090 load_above_capacity
/= busiest
->group_capacity
;
7092 load_above_capacity
= ~0UL;
7096 * We're trying to get all the cpus to the average_load, so we don't
7097 * want to push ourselves above the average load, nor do we wish to
7098 * reduce the max loaded cpu below the average load. At the same time,
7099 * we also don't want to reduce the group load below the group
7100 * capacity. Thus we look for the minimum possible imbalance.
7102 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
7104 /* How much load to actually move to equalise the imbalance */
7105 env
->imbalance
= min(
7106 max_pull
* busiest
->group_capacity
,
7107 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
7108 ) / SCHED_CAPACITY_SCALE
;
7111 * if *imbalance is less than the average load per runnable task
7112 * there is no guarantee that any tasks will be moved so we'll have
7113 * a think about bumping its value to force at least one task to be
7116 if (env
->imbalance
< busiest
->load_per_task
)
7117 return fix_small_imbalance(env
, sds
);
7120 /******* find_busiest_group() helpers end here *********************/
7123 * find_busiest_group - Returns the busiest group within the sched_domain
7124 * if there is an imbalance.
7126 * Also calculates the amount of weighted load which should be moved
7127 * to restore balance.
7129 * @env: The load balancing environment.
7131 * Return: - The busiest group if imbalance exists.
7133 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
7135 struct sg_lb_stats
*local
, *busiest
;
7136 struct sd_lb_stats sds
;
7138 init_sd_lb_stats(&sds
);
7141 * Compute the various statistics relavent for load balancing at
7144 update_sd_lb_stats(env
, &sds
);
7145 local
= &sds
.local_stat
;
7146 busiest
= &sds
.busiest_stat
;
7148 /* ASYM feature bypasses nice load balance check */
7149 if (check_asym_packing(env
, &sds
))
7152 /* There is no busy sibling group to pull tasks from */
7153 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
7156 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
7157 / sds
.total_capacity
;
7160 * If the busiest group is imbalanced the below checks don't
7161 * work because they assume all things are equal, which typically
7162 * isn't true due to cpus_allowed constraints and the like.
7164 if (busiest
->group_type
== group_imbalanced
)
7167 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7168 if (env
->idle
== CPU_NEWLY_IDLE
&& group_has_capacity(env
, local
) &&
7169 busiest
->group_no_capacity
)
7173 * If the local group is busier than the selected busiest group
7174 * don't try and pull any tasks.
7176 if (local
->avg_load
>= busiest
->avg_load
)
7180 * Don't pull any tasks if this group is already above the domain
7183 if (local
->avg_load
>= sds
.avg_load
)
7186 if (env
->idle
== CPU_IDLE
) {
7188 * This cpu is idle. If the busiest group is not overloaded
7189 * and there is no imbalance between this and busiest group
7190 * wrt idle cpus, it is balanced. The imbalance becomes
7191 * significant if the diff is greater than 1 otherwise we
7192 * might end up to just move the imbalance on another group
7194 if ((busiest
->group_type
!= group_overloaded
) &&
7195 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
7199 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7200 * imbalance_pct to be conservative.
7202 if (100 * busiest
->avg_load
<=
7203 env
->sd
->imbalance_pct
* local
->avg_load
)
7208 /* Looks like there is an imbalance. Compute it */
7209 calculate_imbalance(env
, &sds
);
7218 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7220 static struct rq
*find_busiest_queue(struct lb_env
*env
,
7221 struct sched_group
*group
)
7223 struct rq
*busiest
= NULL
, *rq
;
7224 unsigned long busiest_load
= 0, busiest_capacity
= 1;
7227 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
7228 unsigned long capacity
, wl
;
7232 rt
= fbq_classify_rq(rq
);
7235 * We classify groups/runqueues into three groups:
7236 * - regular: there are !numa tasks
7237 * - remote: there are numa tasks that run on the 'wrong' node
7238 * - all: there is no distinction
7240 * In order to avoid migrating ideally placed numa tasks,
7241 * ignore those when there's better options.
7243 * If we ignore the actual busiest queue to migrate another
7244 * task, the next balance pass can still reduce the busiest
7245 * queue by moving tasks around inside the node.
7247 * If we cannot move enough load due to this classification
7248 * the next pass will adjust the group classification and
7249 * allow migration of more tasks.
7251 * Both cases only affect the total convergence complexity.
7253 if (rt
> env
->fbq_type
)
7256 capacity
= capacity_of(i
);
7258 wl
= weighted_cpuload(i
);
7261 * When comparing with imbalance, use weighted_cpuload()
7262 * which is not scaled with the cpu capacity.
7265 if (rq
->nr_running
== 1 && wl
> env
->imbalance
&&
7266 !check_cpu_capacity(rq
, env
->sd
))
7270 * For the load comparisons with the other cpu's, consider
7271 * the weighted_cpuload() scaled with the cpu capacity, so
7272 * that the load can be moved away from the cpu that is
7273 * potentially running at a lower capacity.
7275 * Thus we're looking for max(wl_i / capacity_i), crosswise
7276 * multiplication to rid ourselves of the division works out
7277 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7278 * our previous maximum.
7280 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
7282 busiest_capacity
= capacity
;
7291 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7292 * so long as it is large enough.
7294 #define MAX_PINNED_INTERVAL 512
7296 /* Working cpumask for load_balance and load_balance_newidle. */
7297 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
7299 static int need_active_balance(struct lb_env
*env
)
7301 struct sched_domain
*sd
= env
->sd
;
7303 if (env
->idle
== CPU_NEWLY_IDLE
) {
7306 * ASYM_PACKING needs to force migrate tasks from busy but
7307 * higher numbered CPUs in order to pack all tasks in the
7308 * lowest numbered CPUs.
7310 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
7315 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7316 * It's worth migrating the task if the src_cpu's capacity is reduced
7317 * because of other sched_class or IRQs if more capacity stays
7318 * available on dst_cpu.
7320 if ((env
->idle
!= CPU_NOT_IDLE
) &&
7321 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
7322 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
7323 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
7327 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
7330 static int active_load_balance_cpu_stop(void *data
);
7332 static int should_we_balance(struct lb_env
*env
)
7334 struct sched_group
*sg
= env
->sd
->groups
;
7335 struct cpumask
*sg_cpus
, *sg_mask
;
7336 int cpu
, balance_cpu
= -1;
7339 * In the newly idle case, we will allow all the cpu's
7340 * to do the newly idle load balance.
7342 if (env
->idle
== CPU_NEWLY_IDLE
)
7345 sg_cpus
= sched_group_cpus(sg
);
7346 sg_mask
= sched_group_mask(sg
);
7347 /* Try to find first idle cpu */
7348 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
7349 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
7356 if (balance_cpu
== -1)
7357 balance_cpu
= group_balance_cpu(sg
);
7360 * First idle cpu or the first cpu(busiest) in this sched group
7361 * is eligible for doing load balancing at this and above domains.
7363 return balance_cpu
== env
->dst_cpu
;
7367 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7368 * tasks if there is an imbalance.
7370 static int load_balance(int this_cpu
, struct rq
*this_rq
,
7371 struct sched_domain
*sd
, enum cpu_idle_type idle
,
7372 int *continue_balancing
)
7374 int ld_moved
, cur_ld_moved
, active_balance
= 0;
7375 struct sched_domain
*sd_parent
= sd
->parent
;
7376 struct sched_group
*group
;
7378 unsigned long flags
;
7379 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
7381 struct lb_env env
= {
7383 .dst_cpu
= this_cpu
,
7385 .dst_grpmask
= sched_group_cpus(sd
->groups
),
7387 .loop_break
= sched_nr_migrate_break
,
7390 .tasks
= LIST_HEAD_INIT(env
.tasks
),
7394 * For NEWLY_IDLE load_balancing, we don't need to consider
7395 * other cpus in our group
7397 if (idle
== CPU_NEWLY_IDLE
)
7398 env
.dst_grpmask
= NULL
;
7400 cpumask_copy(cpus
, cpu_active_mask
);
7402 schedstat_inc(sd
, lb_count
[idle
]);
7405 if (!should_we_balance(&env
)) {
7406 *continue_balancing
= 0;
7410 group
= find_busiest_group(&env
);
7412 schedstat_inc(sd
, lb_nobusyg
[idle
]);
7416 busiest
= find_busiest_queue(&env
, group
);
7418 schedstat_inc(sd
, lb_nobusyq
[idle
]);
7422 BUG_ON(busiest
== env
.dst_rq
);
7424 schedstat_add(sd
, lb_imbalance
[idle
], env
.imbalance
);
7426 env
.src_cpu
= busiest
->cpu
;
7427 env
.src_rq
= busiest
;
7430 if (busiest
->nr_running
> 1) {
7432 * Attempt to move tasks. If find_busiest_group has found
7433 * an imbalance but busiest->nr_running <= 1, the group is
7434 * still unbalanced. ld_moved simply stays zero, so it is
7435 * correctly treated as an imbalance.
7437 env
.flags
|= LBF_ALL_PINNED
;
7438 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
7441 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7444 * cur_ld_moved - load moved in current iteration
7445 * ld_moved - cumulative load moved across iterations
7447 cur_ld_moved
= detach_tasks(&env
);
7450 * We've detached some tasks from busiest_rq. Every
7451 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7452 * unlock busiest->lock, and we are able to be sure
7453 * that nobody can manipulate the tasks in parallel.
7454 * See task_rq_lock() family for the details.
7457 raw_spin_unlock(&busiest
->lock
);
7461 ld_moved
+= cur_ld_moved
;
7464 local_irq_restore(flags
);
7466 if (env
.flags
& LBF_NEED_BREAK
) {
7467 env
.flags
&= ~LBF_NEED_BREAK
;
7472 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7473 * us and move them to an alternate dst_cpu in our sched_group
7474 * where they can run. The upper limit on how many times we
7475 * iterate on same src_cpu is dependent on number of cpus in our
7478 * This changes load balance semantics a bit on who can move
7479 * load to a given_cpu. In addition to the given_cpu itself
7480 * (or a ilb_cpu acting on its behalf where given_cpu is
7481 * nohz-idle), we now have balance_cpu in a position to move
7482 * load to given_cpu. In rare situations, this may cause
7483 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7484 * _independently_ and at _same_ time to move some load to
7485 * given_cpu) causing exceess load to be moved to given_cpu.
7486 * This however should not happen so much in practice and
7487 * moreover subsequent load balance cycles should correct the
7488 * excess load moved.
7490 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
7492 /* Prevent to re-select dst_cpu via env's cpus */
7493 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
7495 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
7496 env
.dst_cpu
= env
.new_dst_cpu
;
7497 env
.flags
&= ~LBF_DST_PINNED
;
7499 env
.loop_break
= sched_nr_migrate_break
;
7502 * Go back to "more_balance" rather than "redo" since we
7503 * need to continue with same src_cpu.
7509 * We failed to reach balance because of affinity.
7512 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7514 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
7515 *group_imbalance
= 1;
7518 /* All tasks on this runqueue were pinned by CPU affinity */
7519 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
7520 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
7521 if (!cpumask_empty(cpus
)) {
7523 env
.loop_break
= sched_nr_migrate_break
;
7526 goto out_all_pinned
;
7531 schedstat_inc(sd
, lb_failed
[idle
]);
7533 * Increment the failure counter only on periodic balance.
7534 * We do not want newidle balance, which can be very
7535 * frequent, pollute the failure counter causing
7536 * excessive cache_hot migrations and active balances.
7538 if (idle
!= CPU_NEWLY_IDLE
)
7539 sd
->nr_balance_failed
++;
7541 if (need_active_balance(&env
)) {
7542 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7544 /* don't kick the active_load_balance_cpu_stop,
7545 * if the curr task on busiest cpu can't be
7548 if (!cpumask_test_cpu(this_cpu
,
7549 tsk_cpus_allowed(busiest
->curr
))) {
7550 raw_spin_unlock_irqrestore(&busiest
->lock
,
7552 env
.flags
|= LBF_ALL_PINNED
;
7553 goto out_one_pinned
;
7557 * ->active_balance synchronizes accesses to
7558 * ->active_balance_work. Once set, it's cleared
7559 * only after active load balance is finished.
7561 if (!busiest
->active_balance
) {
7562 busiest
->active_balance
= 1;
7563 busiest
->push_cpu
= this_cpu
;
7566 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
7568 if (active_balance
) {
7569 stop_one_cpu_nowait(cpu_of(busiest
),
7570 active_load_balance_cpu_stop
, busiest
,
7571 &busiest
->active_balance_work
);
7574 /* We've kicked active balancing, force task migration. */
7575 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
7578 sd
->nr_balance_failed
= 0;
7580 if (likely(!active_balance
)) {
7581 /* We were unbalanced, so reset the balancing interval */
7582 sd
->balance_interval
= sd
->min_interval
;
7585 * If we've begun active balancing, start to back off. This
7586 * case may not be covered by the all_pinned logic if there
7587 * is only 1 task on the busy runqueue (because we don't call
7590 if (sd
->balance_interval
< sd
->max_interval
)
7591 sd
->balance_interval
*= 2;
7598 * We reach balance although we may have faced some affinity
7599 * constraints. Clear the imbalance flag if it was set.
7602 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7604 if (*group_imbalance
)
7605 *group_imbalance
= 0;
7610 * We reach balance because all tasks are pinned at this level so
7611 * we can't migrate them. Let the imbalance flag set so parent level
7612 * can try to migrate them.
7614 schedstat_inc(sd
, lb_balanced
[idle
]);
7616 sd
->nr_balance_failed
= 0;
7619 /* tune up the balancing interval */
7620 if (((env
.flags
& LBF_ALL_PINNED
) &&
7621 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
7622 (sd
->balance_interval
< sd
->max_interval
))
7623 sd
->balance_interval
*= 2;
7630 static inline unsigned long
7631 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
7633 unsigned long interval
= sd
->balance_interval
;
7636 interval
*= sd
->busy_factor
;
7638 /* scale ms to jiffies */
7639 interval
= msecs_to_jiffies(interval
);
7640 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7646 update_next_balance(struct sched_domain
*sd
, int cpu_busy
, unsigned long *next_balance
)
7648 unsigned long interval
, next
;
7650 interval
= get_sd_balance_interval(sd
, cpu_busy
);
7651 next
= sd
->last_balance
+ interval
;
7653 if (time_after(*next_balance
, next
))
7654 *next_balance
= next
;
7658 * idle_balance is called by schedule() if this_cpu is about to become
7659 * idle. Attempts to pull tasks from other CPUs.
7661 static int idle_balance(struct rq
*this_rq
)
7663 unsigned long next_balance
= jiffies
+ HZ
;
7664 int this_cpu
= this_rq
->cpu
;
7665 struct sched_domain
*sd
;
7666 int pulled_task
= 0;
7670 * We must set idle_stamp _before_ calling idle_balance(), such that we
7671 * measure the duration of idle_balance() as idle time.
7673 this_rq
->idle_stamp
= rq_clock(this_rq
);
7675 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
7676 !this_rq
->rd
->overload
) {
7678 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
7680 update_next_balance(sd
, 0, &next_balance
);
7686 raw_spin_unlock(&this_rq
->lock
);
7688 update_blocked_averages(this_cpu
);
7690 for_each_domain(this_cpu
, sd
) {
7691 int continue_balancing
= 1;
7692 u64 t0
, domain_cost
;
7694 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7697 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
7698 update_next_balance(sd
, 0, &next_balance
);
7702 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
7703 t0
= sched_clock_cpu(this_cpu
);
7705 pulled_task
= load_balance(this_cpu
, this_rq
,
7707 &continue_balancing
);
7709 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
7710 if (domain_cost
> sd
->max_newidle_lb_cost
)
7711 sd
->max_newidle_lb_cost
= domain_cost
;
7713 curr_cost
+= domain_cost
;
7716 update_next_balance(sd
, 0, &next_balance
);
7719 * Stop searching for tasks to pull if there are
7720 * now runnable tasks on this rq.
7722 if (pulled_task
|| this_rq
->nr_running
> 0)
7727 raw_spin_lock(&this_rq
->lock
);
7729 if (curr_cost
> this_rq
->max_idle_balance_cost
)
7730 this_rq
->max_idle_balance_cost
= curr_cost
;
7733 * While browsing the domains, we released the rq lock, a task could
7734 * have been enqueued in the meantime. Since we're not going idle,
7735 * pretend we pulled a task.
7737 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
7741 /* Move the next balance forward */
7742 if (time_after(this_rq
->next_balance
, next_balance
))
7743 this_rq
->next_balance
= next_balance
;
7745 /* Is there a task of a high priority class? */
7746 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
7750 this_rq
->idle_stamp
= 0;
7756 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7757 * running tasks off the busiest CPU onto idle CPUs. It requires at
7758 * least 1 task to be running on each physical CPU where possible, and
7759 * avoids physical / logical imbalances.
7761 static int active_load_balance_cpu_stop(void *data
)
7763 struct rq
*busiest_rq
= data
;
7764 int busiest_cpu
= cpu_of(busiest_rq
);
7765 int target_cpu
= busiest_rq
->push_cpu
;
7766 struct rq
*target_rq
= cpu_rq(target_cpu
);
7767 struct sched_domain
*sd
;
7768 struct task_struct
*p
= NULL
;
7770 raw_spin_lock_irq(&busiest_rq
->lock
);
7772 /* make sure the requested cpu hasn't gone down in the meantime */
7773 if (unlikely(busiest_cpu
!= smp_processor_id() ||
7774 !busiest_rq
->active_balance
))
7777 /* Is there any task to move? */
7778 if (busiest_rq
->nr_running
<= 1)
7782 * This condition is "impossible", if it occurs
7783 * we need to fix it. Originally reported by
7784 * Bjorn Helgaas on a 128-cpu setup.
7786 BUG_ON(busiest_rq
== target_rq
);
7788 /* Search for an sd spanning us and the target CPU. */
7790 for_each_domain(target_cpu
, sd
) {
7791 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
7792 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
7797 struct lb_env env
= {
7799 .dst_cpu
= target_cpu
,
7800 .dst_rq
= target_rq
,
7801 .src_cpu
= busiest_rq
->cpu
,
7802 .src_rq
= busiest_rq
,
7806 schedstat_inc(sd
, alb_count
);
7808 p
= detach_one_task(&env
);
7810 schedstat_inc(sd
, alb_pushed
);
7811 /* Active balancing done, reset the failure counter. */
7812 sd
->nr_balance_failed
= 0;
7814 schedstat_inc(sd
, alb_failed
);
7819 busiest_rq
->active_balance
= 0;
7820 raw_spin_unlock(&busiest_rq
->lock
);
7823 attach_one_task(target_rq
, p
);
7830 static inline int on_null_domain(struct rq
*rq
)
7832 return unlikely(!rcu_dereference_sched(rq
->sd
));
7835 #ifdef CONFIG_NO_HZ_COMMON
7837 * idle load balancing details
7838 * - When one of the busy CPUs notice that there may be an idle rebalancing
7839 * needed, they will kick the idle load balancer, which then does idle
7840 * load balancing for all the idle CPUs.
7843 cpumask_var_t idle_cpus_mask
;
7845 unsigned long next_balance
; /* in jiffy units */
7846 } nohz ____cacheline_aligned
;
7848 static inline int find_new_ilb(void)
7850 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
7852 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
7859 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7860 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7861 * CPU (if there is one).
7863 static void nohz_balancer_kick(void)
7867 nohz
.next_balance
++;
7869 ilb_cpu
= find_new_ilb();
7871 if (ilb_cpu
>= nr_cpu_ids
)
7874 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
7877 * Use smp_send_reschedule() instead of resched_cpu().
7878 * This way we generate a sched IPI on the target cpu which
7879 * is idle. And the softirq performing nohz idle load balance
7880 * will be run before returning from the IPI.
7882 smp_send_reschedule(ilb_cpu
);
7886 void nohz_balance_exit_idle(unsigned int cpu
)
7888 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
7890 * Completely isolated CPUs don't ever set, so we must test.
7892 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
7893 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
7894 atomic_dec(&nohz
.nr_cpus
);
7896 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7900 static inline void set_cpu_sd_state_busy(void)
7902 struct sched_domain
*sd
;
7903 int cpu
= smp_processor_id();
7906 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7908 if (!sd
|| !sd
->nohz_idle
)
7912 atomic_inc(&sd
->groups
->sgc
->nr_busy_cpus
);
7917 void set_cpu_sd_state_idle(void)
7919 struct sched_domain
*sd
;
7920 int cpu
= smp_processor_id();
7923 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7925 if (!sd
|| sd
->nohz_idle
)
7929 atomic_dec(&sd
->groups
->sgc
->nr_busy_cpus
);
7935 * This routine will record that the cpu is going idle with tick stopped.
7936 * This info will be used in performing idle load balancing in the future.
7938 void nohz_balance_enter_idle(int cpu
)
7941 * If this cpu is going down, then nothing needs to be done.
7943 if (!cpu_active(cpu
))
7946 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
7950 * If we're a completely isolated CPU, we don't play.
7952 if (on_null_domain(cpu_rq(cpu
)))
7955 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
7956 atomic_inc(&nohz
.nr_cpus
);
7957 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7961 static DEFINE_SPINLOCK(balancing
);
7964 * Scale the max load_balance interval with the number of CPUs in the system.
7965 * This trades load-balance latency on larger machines for less cross talk.
7967 void update_max_interval(void)
7969 max_load_balance_interval
= HZ
*num_online_cpus()/10;
7973 * It checks each scheduling domain to see if it is due to be balanced,
7974 * and initiates a balancing operation if so.
7976 * Balancing parameters are set up in init_sched_domains.
7978 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
7980 int continue_balancing
= 1;
7982 unsigned long interval
;
7983 struct sched_domain
*sd
;
7984 /* Earliest time when we have to do rebalance again */
7985 unsigned long next_balance
= jiffies
+ 60*HZ
;
7986 int update_next_balance
= 0;
7987 int need_serialize
, need_decay
= 0;
7990 update_blocked_averages(cpu
);
7993 for_each_domain(cpu
, sd
) {
7995 * Decay the newidle max times here because this is a regular
7996 * visit to all the domains. Decay ~1% per second.
7998 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
7999 sd
->max_newidle_lb_cost
=
8000 (sd
->max_newidle_lb_cost
* 253) / 256;
8001 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
8004 max_cost
+= sd
->max_newidle_lb_cost
;
8006 if (!(sd
->flags
& SD_LOAD_BALANCE
))
8010 * Stop the load balance at this level. There is another
8011 * CPU in our sched group which is doing load balancing more
8014 if (!continue_balancing
) {
8020 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8022 need_serialize
= sd
->flags
& SD_SERIALIZE
;
8023 if (need_serialize
) {
8024 if (!spin_trylock(&balancing
))
8028 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
8029 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
8031 * The LBF_DST_PINNED logic could have changed
8032 * env->dst_cpu, so we can't know our idle
8033 * state even if we migrated tasks. Update it.
8035 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
8037 sd
->last_balance
= jiffies
;
8038 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8041 spin_unlock(&balancing
);
8043 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
8044 next_balance
= sd
->last_balance
+ interval
;
8045 update_next_balance
= 1;
8050 * Ensure the rq-wide value also decays but keep it at a
8051 * reasonable floor to avoid funnies with rq->avg_idle.
8053 rq
->max_idle_balance_cost
=
8054 max((u64
)sysctl_sched_migration_cost
, max_cost
);
8059 * next_balance will be updated only when there is a need.
8060 * When the cpu is attached to null domain for ex, it will not be
8063 if (likely(update_next_balance
)) {
8064 rq
->next_balance
= next_balance
;
8066 #ifdef CONFIG_NO_HZ_COMMON
8068 * If this CPU has been elected to perform the nohz idle
8069 * balance. Other idle CPUs have already rebalanced with
8070 * nohz_idle_balance() and nohz.next_balance has been
8071 * updated accordingly. This CPU is now running the idle load
8072 * balance for itself and we need to update the
8073 * nohz.next_balance accordingly.
8075 if ((idle
== CPU_IDLE
) && time_after(nohz
.next_balance
, rq
->next_balance
))
8076 nohz
.next_balance
= rq
->next_balance
;
8081 #ifdef CONFIG_NO_HZ_COMMON
8083 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8084 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8086 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
8088 int this_cpu
= this_rq
->cpu
;
8091 /* Earliest time when we have to do rebalance again */
8092 unsigned long next_balance
= jiffies
+ 60*HZ
;
8093 int update_next_balance
= 0;
8095 if (idle
!= CPU_IDLE
||
8096 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
8099 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
8100 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
8104 * If this cpu gets work to do, stop the load balancing
8105 * work being done for other cpus. Next load
8106 * balancing owner will pick it up.
8111 rq
= cpu_rq(balance_cpu
);
8114 * If time for next balance is due,
8117 if (time_after_eq(jiffies
, rq
->next_balance
)) {
8118 raw_spin_lock_irq(&rq
->lock
);
8119 update_rq_clock(rq
);
8120 cpu_load_update_idle(rq
);
8121 raw_spin_unlock_irq(&rq
->lock
);
8122 rebalance_domains(rq
, CPU_IDLE
);
8125 if (time_after(next_balance
, rq
->next_balance
)) {
8126 next_balance
= rq
->next_balance
;
8127 update_next_balance
= 1;
8132 * next_balance will be updated only when there is a need.
8133 * When the CPU is attached to null domain for ex, it will not be
8136 if (likely(update_next_balance
))
8137 nohz
.next_balance
= next_balance
;
8139 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
8143 * Current heuristic for kicking the idle load balancer in the presence
8144 * of an idle cpu in the system.
8145 * - This rq has more than one task.
8146 * - This rq has at least one CFS task and the capacity of the CPU is
8147 * significantly reduced because of RT tasks or IRQs.
8148 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8149 * multiple busy cpu.
8150 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8151 * domain span are idle.
8153 static inline bool nohz_kick_needed(struct rq
*rq
)
8155 unsigned long now
= jiffies
;
8156 struct sched_domain
*sd
;
8157 struct sched_group_capacity
*sgc
;
8158 int nr_busy
, cpu
= rq
->cpu
;
8161 if (unlikely(rq
->idle_balance
))
8165 * We may be recently in ticked or tickless idle mode. At the first
8166 * busy tick after returning from idle, we will update the busy stats.
8168 set_cpu_sd_state_busy();
8169 nohz_balance_exit_idle(cpu
);
8172 * None are in tickless mode and hence no need for NOHZ idle load
8175 if (likely(!atomic_read(&nohz
.nr_cpus
)))
8178 if (time_before(now
, nohz
.next_balance
))
8181 if (rq
->nr_running
>= 2)
8185 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8187 sgc
= sd
->groups
->sgc
;
8188 nr_busy
= atomic_read(&sgc
->nr_busy_cpus
);
8197 sd
= rcu_dereference(rq
->sd
);
8199 if ((rq
->cfs
.h_nr_running
>= 1) &&
8200 check_cpu_capacity(rq
, sd
)) {
8206 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
8207 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
8208 sched_domain_span(sd
)) < cpu
)) {
8218 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
8222 * run_rebalance_domains is triggered when needed from the scheduler tick.
8223 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8225 static void run_rebalance_domains(struct softirq_action
*h
)
8227 struct rq
*this_rq
= this_rq();
8228 enum cpu_idle_type idle
= this_rq
->idle_balance
?
8229 CPU_IDLE
: CPU_NOT_IDLE
;
8232 * If this cpu has a pending nohz_balance_kick, then do the
8233 * balancing on behalf of the other idle cpus whose ticks are
8234 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8235 * give the idle cpus a chance to load balance. Else we may
8236 * load balance only within the local sched_domain hierarchy
8237 * and abort nohz_idle_balance altogether if we pull some load.
8239 nohz_idle_balance(this_rq
, idle
);
8240 rebalance_domains(this_rq
, idle
);
8244 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8246 void trigger_load_balance(struct rq
*rq
)
8248 /* Don't need to rebalance while attached to NULL domain */
8249 if (unlikely(on_null_domain(rq
)))
8252 if (time_after_eq(jiffies
, rq
->next_balance
))
8253 raise_softirq(SCHED_SOFTIRQ
);
8254 #ifdef CONFIG_NO_HZ_COMMON
8255 if (nohz_kick_needed(rq
))
8256 nohz_balancer_kick();
8260 static void rq_online_fair(struct rq
*rq
)
8264 update_runtime_enabled(rq
);
8267 static void rq_offline_fair(struct rq
*rq
)
8271 /* Ensure any throttled groups are reachable by pick_next_task */
8272 unthrottle_offline_cfs_rqs(rq
);
8275 #endif /* CONFIG_SMP */
8278 * scheduler tick hitting a task of our scheduling class:
8280 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
8282 struct cfs_rq
*cfs_rq
;
8283 struct sched_entity
*se
= &curr
->se
;
8285 for_each_sched_entity(se
) {
8286 cfs_rq
= cfs_rq_of(se
);
8287 entity_tick(cfs_rq
, se
, queued
);
8290 if (static_branch_unlikely(&sched_numa_balancing
))
8291 task_tick_numa(rq
, curr
);
8295 * called on fork with the child task as argument from the parent's context
8296 * - child not yet on the tasklist
8297 * - preemption disabled
8299 static void task_fork_fair(struct task_struct
*p
)
8301 struct cfs_rq
*cfs_rq
;
8302 struct sched_entity
*se
= &p
->se
, *curr
;
8303 int this_cpu
= smp_processor_id();
8304 struct rq
*rq
= this_rq();
8305 unsigned long flags
;
8307 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8309 update_rq_clock(rq
);
8311 cfs_rq
= task_cfs_rq(current
);
8312 curr
= cfs_rq
->curr
;
8315 * Not only the cpu but also the task_group of the parent might have
8316 * been changed after parent->se.parent,cfs_rq were copied to
8317 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8318 * of child point to valid ones.
8321 __set_task_cpu(p
, this_cpu
);
8324 update_curr(cfs_rq
);
8327 se
->vruntime
= curr
->vruntime
;
8328 place_entity(cfs_rq
, se
, 1);
8330 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
8332 * Upon rescheduling, sched_class::put_prev_task() will place
8333 * 'current' within the tree based on its new key value.
8335 swap(curr
->vruntime
, se
->vruntime
);
8339 se
->vruntime
-= cfs_rq
->min_vruntime
;
8341 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8345 * Priority of the task has changed. Check to see if we preempt
8349 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
8351 if (!task_on_rq_queued(p
))
8355 * Reschedule if we are currently running on this runqueue and
8356 * our priority decreased, or if we are not currently running on
8357 * this runqueue and our priority is higher than the current's
8359 if (rq
->curr
== p
) {
8360 if (p
->prio
> oldprio
)
8363 check_preempt_curr(rq
, p
, 0);
8366 static inline bool vruntime_normalized(struct task_struct
*p
)
8368 struct sched_entity
*se
= &p
->se
;
8371 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8372 * the dequeue_entity(.flags=0) will already have normalized the
8379 * When !on_rq, vruntime of the task has usually NOT been normalized.
8380 * But there are some cases where it has already been normalized:
8382 * - A forked child which is waiting for being woken up by
8383 * wake_up_new_task().
8384 * - A task which has been woken up by try_to_wake_up() and
8385 * waiting for actually being woken up by sched_ttwu_pending().
8387 if (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
)
8393 static void detach_task_cfs_rq(struct task_struct
*p
)
8395 struct sched_entity
*se
= &p
->se
;
8396 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8398 if (!vruntime_normalized(p
)) {
8400 * Fix up our vruntime so that the current sleep doesn't
8401 * cause 'unlimited' sleep bonus.
8403 place_entity(cfs_rq
, se
, 0);
8404 se
->vruntime
-= cfs_rq
->min_vruntime
;
8407 /* Catch up with the cfs_rq and remove our load when we leave */
8408 detach_entity_load_avg(cfs_rq
, se
);
8411 static void attach_task_cfs_rq(struct task_struct
*p
)
8413 struct sched_entity
*se
= &p
->se
;
8414 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8416 #ifdef CONFIG_FAIR_GROUP_SCHED
8418 * Since the real-depth could have been changed (only FAIR
8419 * class maintain depth value), reset depth properly.
8421 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8424 /* Synchronize task with its cfs_rq */
8425 attach_entity_load_avg(cfs_rq
, se
);
8427 if (!vruntime_normalized(p
))
8428 se
->vruntime
+= cfs_rq
->min_vruntime
;
8431 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
8433 detach_task_cfs_rq(p
);
8436 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
8438 attach_task_cfs_rq(p
);
8440 if (task_on_rq_queued(p
)) {
8442 * We were most likely switched from sched_rt, so
8443 * kick off the schedule if running, otherwise just see
8444 * if we can still preempt the current task.
8449 check_preempt_curr(rq
, p
, 0);
8453 /* Account for a task changing its policy or group.
8455 * This routine is mostly called to set cfs_rq->curr field when a task
8456 * migrates between groups/classes.
8458 static void set_curr_task_fair(struct rq
*rq
)
8460 struct sched_entity
*se
= &rq
->curr
->se
;
8462 for_each_sched_entity(se
) {
8463 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8465 set_next_entity(cfs_rq
, se
);
8466 /* ensure bandwidth has been allocated on our new cfs_rq */
8467 account_cfs_rq_runtime(cfs_rq
, 0);
8471 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
8473 cfs_rq
->tasks_timeline
= RB_ROOT
;
8474 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
8475 #ifndef CONFIG_64BIT
8476 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
8479 atomic_long_set(&cfs_rq
->removed_load_avg
, 0);
8480 atomic_long_set(&cfs_rq
->removed_util_avg
, 0);
8484 #ifdef CONFIG_FAIR_GROUP_SCHED
8485 static void task_move_group_fair(struct task_struct
*p
)
8487 detach_task_cfs_rq(p
);
8488 set_task_rq(p
, task_cpu(p
));
8491 /* Tell se's cfs_rq has been changed -- migrated */
8492 p
->se
.avg
.last_update_time
= 0;
8494 attach_task_cfs_rq(p
);
8497 void free_fair_sched_group(struct task_group
*tg
)
8501 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8503 for_each_possible_cpu(i
) {
8505 kfree(tg
->cfs_rq
[i
]);
8514 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8516 struct sched_entity
*se
;
8517 struct cfs_rq
*cfs_rq
;
8521 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
8524 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
8528 tg
->shares
= NICE_0_LOAD
;
8530 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8532 for_each_possible_cpu(i
) {
8535 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
8536 GFP_KERNEL
, cpu_to_node(i
));
8540 se
= kzalloc_node(sizeof(struct sched_entity
),
8541 GFP_KERNEL
, cpu_to_node(i
));
8545 init_cfs_rq(cfs_rq
);
8546 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
8547 init_entity_runnable_average(se
);
8549 raw_spin_lock_irq(&rq
->lock
);
8550 post_init_entity_util_avg(se
);
8551 raw_spin_unlock_irq(&rq
->lock
);
8562 void unregister_fair_sched_group(struct task_group
*tg
)
8564 unsigned long flags
;
8568 for_each_possible_cpu(cpu
) {
8570 remove_entity_load_avg(tg
->se
[cpu
]);
8573 * Only empty task groups can be destroyed; so we can speculatively
8574 * check on_list without danger of it being re-added.
8576 if (!tg
->cfs_rq
[cpu
]->on_list
)
8581 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8582 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
8583 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8587 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
8588 struct sched_entity
*se
, int cpu
,
8589 struct sched_entity
*parent
)
8591 struct rq
*rq
= cpu_rq(cpu
);
8595 init_cfs_rq_runtime(cfs_rq
);
8597 tg
->cfs_rq
[cpu
] = cfs_rq
;
8600 /* se could be NULL for root_task_group */
8605 se
->cfs_rq
= &rq
->cfs
;
8608 se
->cfs_rq
= parent
->my_q
;
8609 se
->depth
= parent
->depth
+ 1;
8613 /* guarantee group entities always have weight */
8614 update_load_set(&se
->load
, NICE_0_LOAD
);
8615 se
->parent
= parent
;
8618 static DEFINE_MUTEX(shares_mutex
);
8620 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
8623 unsigned long flags
;
8626 * We can't change the weight of the root cgroup.
8631 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
8633 mutex_lock(&shares_mutex
);
8634 if (tg
->shares
== shares
)
8637 tg
->shares
= shares
;
8638 for_each_possible_cpu(i
) {
8639 struct rq
*rq
= cpu_rq(i
);
8640 struct sched_entity
*se
;
8643 /* Propagate contribution to hierarchy */
8644 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8646 /* Possible calls to update_curr() need rq clock */
8647 update_rq_clock(rq
);
8648 for_each_sched_entity(se
)
8649 update_cfs_shares(group_cfs_rq(se
));
8650 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8654 mutex_unlock(&shares_mutex
);
8657 #else /* CONFIG_FAIR_GROUP_SCHED */
8659 void free_fair_sched_group(struct task_group
*tg
) { }
8661 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8666 void unregister_fair_sched_group(struct task_group
*tg
) { }
8668 #endif /* CONFIG_FAIR_GROUP_SCHED */
8671 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
8673 struct sched_entity
*se
= &task
->se
;
8674 unsigned int rr_interval
= 0;
8677 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8680 if (rq
->cfs
.load
.weight
)
8681 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
8687 * All the scheduling class methods:
8689 const struct sched_class fair_sched_class
= {
8690 .next
= &idle_sched_class
,
8691 .enqueue_task
= enqueue_task_fair
,
8692 .dequeue_task
= dequeue_task_fair
,
8693 .yield_task
= yield_task_fair
,
8694 .yield_to_task
= yield_to_task_fair
,
8696 .check_preempt_curr
= check_preempt_wakeup
,
8698 .pick_next_task
= pick_next_task_fair
,
8699 .put_prev_task
= put_prev_task_fair
,
8702 .select_task_rq
= select_task_rq_fair
,
8703 .migrate_task_rq
= migrate_task_rq_fair
,
8705 .rq_online
= rq_online_fair
,
8706 .rq_offline
= rq_offline_fair
,
8708 .task_dead
= task_dead_fair
,
8709 .set_cpus_allowed
= set_cpus_allowed_common
,
8712 .set_curr_task
= set_curr_task_fair
,
8713 .task_tick
= task_tick_fair
,
8714 .task_fork
= task_fork_fair
,
8716 .prio_changed
= prio_changed_fair
,
8717 .switched_from
= switched_from_fair
,
8718 .switched_to
= switched_to_fair
,
8720 .get_rr_interval
= get_rr_interval_fair
,
8722 .update_curr
= update_curr_fair
,
8724 #ifdef CONFIG_FAIR_GROUP_SCHED
8725 .task_move_group
= task_move_group_fair
,
8729 #ifdef CONFIG_SCHED_DEBUG
8730 void print_cfs_stats(struct seq_file
*m
, int cpu
)
8732 struct cfs_rq
*cfs_rq
;
8735 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
8736 print_cfs_rq(m
, cpu
, cfs_rq
);
8740 #ifdef CONFIG_NUMA_BALANCING
8741 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
8744 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
8746 for_each_online_node(node
) {
8747 if (p
->numa_faults
) {
8748 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
8749 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8751 if (p
->numa_group
) {
8752 gsf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
8753 gpf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8755 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
8758 #endif /* CONFIG_NUMA_BALANCING */
8759 #endif /* CONFIG_SCHED_DEBUG */
8761 __init
void init_sched_fair_class(void)
8764 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
8766 #ifdef CONFIG_NO_HZ_COMMON
8767 nohz
.next_balance
= jiffies
;
8768 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);