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)(scale_load_down(SCHED_LOAD_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,
2607 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2609 static __always_inline u64
decay_load(u64 val
, u64 n
)
2611 unsigned int local_n
;
2615 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2618 /* after bounds checking we can collapse to 32-bit */
2622 * As y^PERIOD = 1/2, we can combine
2623 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2624 * With a look-up table which covers y^n (n<PERIOD)
2626 * To achieve constant time decay_load.
2628 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2629 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2630 local_n
%= LOAD_AVG_PERIOD
;
2633 val
= mul_u64_u32_shr(val
, runnable_avg_yN_inv
[local_n
], 32);
2638 * For updates fully spanning n periods, the contribution to runnable
2639 * average will be: \Sum 1024*y^n
2641 * We can compute this reasonably efficiently by combining:
2642 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2644 static u32
__compute_runnable_contrib(u64 n
)
2648 if (likely(n
<= LOAD_AVG_PERIOD
))
2649 return runnable_avg_yN_sum
[n
];
2650 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2651 return LOAD_AVG_MAX
;
2653 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
2655 contrib
/= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
2656 contrib
+= runnable_avg_yN_sum
[LOAD_AVG_PERIOD
];
2658 n
-= LOAD_AVG_PERIOD
;
2659 } while (n
> LOAD_AVG_PERIOD
);
2661 contrib
= decay_load(contrib
, n
);
2662 return contrib
+ runnable_avg_yN_sum
[n
];
2665 #if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
2666 #error "load tracking assumes 2^10 as unit"
2669 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2672 * We can represent the historical contribution to runnable average as the
2673 * coefficients of a geometric series. To do this we sub-divide our runnable
2674 * history into segments of approximately 1ms (1024us); label the segment that
2675 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2677 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2679 * (now) (~1ms ago) (~2ms ago)
2681 * Let u_i denote the fraction of p_i that the entity was runnable.
2683 * We then designate the fractions u_i as our co-efficients, yielding the
2684 * following representation of historical load:
2685 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2687 * We choose y based on the with of a reasonably scheduling period, fixing:
2690 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2691 * approximately half as much as the contribution to load within the last ms
2694 * When a period "rolls over" and we have new u_0`, multiplying the previous
2695 * sum again by y is sufficient to update:
2696 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2697 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2699 static __always_inline
int
2700 __update_load_avg(u64 now
, int cpu
, struct sched_avg
*sa
,
2701 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
2703 u64 delta
, scaled_delta
, periods
;
2705 unsigned int delta_w
, scaled_delta_w
, decayed
= 0;
2706 unsigned long scale_freq
, scale_cpu
;
2708 delta
= now
- sa
->last_update_time
;
2710 * This should only happen when time goes backwards, which it
2711 * unfortunately does during sched clock init when we swap over to TSC.
2713 if ((s64
)delta
< 0) {
2714 sa
->last_update_time
= now
;
2719 * Use 1024ns as the unit of measurement since it's a reasonable
2720 * approximation of 1us and fast to compute.
2725 sa
->last_update_time
= now
;
2727 scale_freq
= arch_scale_freq_capacity(NULL
, cpu
);
2728 scale_cpu
= arch_scale_cpu_capacity(NULL
, cpu
);
2730 /* delta_w is the amount already accumulated against our next period */
2731 delta_w
= sa
->period_contrib
;
2732 if (delta
+ delta_w
>= 1024) {
2735 /* how much left for next period will start over, we don't know yet */
2736 sa
->period_contrib
= 0;
2739 * Now that we know we're crossing a period boundary, figure
2740 * out how much from delta we need to complete the current
2741 * period and accrue it.
2743 delta_w
= 1024 - delta_w
;
2744 scaled_delta_w
= cap_scale(delta_w
, scale_freq
);
2746 sa
->load_sum
+= weight
* scaled_delta_w
;
2748 cfs_rq
->runnable_load_sum
+=
2749 weight
* scaled_delta_w
;
2753 sa
->util_sum
+= scaled_delta_w
* scale_cpu
;
2757 /* Figure out how many additional periods this update spans */
2758 periods
= delta
/ 1024;
2761 sa
->load_sum
= decay_load(sa
->load_sum
, periods
+ 1);
2763 cfs_rq
->runnable_load_sum
=
2764 decay_load(cfs_rq
->runnable_load_sum
, periods
+ 1);
2766 sa
->util_sum
= decay_load((u64
)(sa
->util_sum
), periods
+ 1);
2768 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2769 contrib
= __compute_runnable_contrib(periods
);
2770 contrib
= cap_scale(contrib
, scale_freq
);
2772 sa
->load_sum
+= weight
* contrib
;
2774 cfs_rq
->runnable_load_sum
+= weight
* contrib
;
2777 sa
->util_sum
+= contrib
* scale_cpu
;
2780 /* Remainder of delta accrued against u_0` */
2781 scaled_delta
= cap_scale(delta
, scale_freq
);
2783 sa
->load_sum
+= weight
* scaled_delta
;
2785 cfs_rq
->runnable_load_sum
+= weight
* scaled_delta
;
2788 sa
->util_sum
+= scaled_delta
* scale_cpu
;
2790 sa
->period_contrib
+= delta
;
2793 sa
->load_avg
= div_u64(sa
->load_sum
, LOAD_AVG_MAX
);
2795 cfs_rq
->runnable_load_avg
=
2796 div_u64(cfs_rq
->runnable_load_sum
, LOAD_AVG_MAX
);
2798 sa
->util_avg
= sa
->util_sum
/ LOAD_AVG_MAX
;
2804 #ifdef CONFIG_FAIR_GROUP_SCHED
2806 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
2807 * and effective_load (which is not done because it is too costly).
2809 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
2811 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
2814 * No need to update load_avg for root_task_group as it is not used.
2816 if (cfs_rq
->tg
== &root_task_group
)
2819 if (force
|| abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
2820 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
2821 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
2826 * Called within set_task_rq() right before setting a task's cpu. The
2827 * caller only guarantees p->pi_lock is held; no other assumptions,
2828 * including the state of rq->lock, should be made.
2830 void set_task_rq_fair(struct sched_entity
*se
,
2831 struct cfs_rq
*prev
, struct cfs_rq
*next
)
2833 if (!sched_feat(ATTACH_AGE_LOAD
))
2837 * We are supposed to update the task to "current" time, then its up to
2838 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2839 * getting what current time is, so simply throw away the out-of-date
2840 * time. This will result in the wakee task is less decayed, but giving
2841 * the wakee more load sounds not bad.
2843 if (se
->avg
.last_update_time
&& prev
) {
2844 u64 p_last_update_time
;
2845 u64 n_last_update_time
;
2847 #ifndef CONFIG_64BIT
2848 u64 p_last_update_time_copy
;
2849 u64 n_last_update_time_copy
;
2852 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
2853 n_last_update_time_copy
= next
->load_last_update_time_copy
;
2857 p_last_update_time
= prev
->avg
.last_update_time
;
2858 n_last_update_time
= next
->avg
.last_update_time
;
2860 } while (p_last_update_time
!= p_last_update_time_copy
||
2861 n_last_update_time
!= n_last_update_time_copy
);
2863 p_last_update_time
= prev
->avg
.last_update_time
;
2864 n_last_update_time
= next
->avg
.last_update_time
;
2866 __update_load_avg(p_last_update_time
, cpu_of(rq_of(prev
)),
2867 &se
->avg
, 0, 0, NULL
);
2868 se
->avg
.last_update_time
= n_last_update_time
;
2871 #else /* CONFIG_FAIR_GROUP_SCHED */
2872 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
) {}
2873 #endif /* CONFIG_FAIR_GROUP_SCHED */
2875 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
2877 /* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2878 static inline int update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
)
2880 struct sched_avg
*sa
= &cfs_rq
->avg
;
2881 struct rq
*rq
= rq_of(cfs_rq
);
2882 int decayed
, removed_load
= 0, removed_util
= 0;
2883 int cpu
= cpu_of(rq
);
2885 if (atomic_long_read(&cfs_rq
->removed_load_avg
)) {
2886 s64 r
= atomic_long_xchg(&cfs_rq
->removed_load_avg
, 0);
2887 sa
->load_avg
= max_t(long, sa
->load_avg
- r
, 0);
2888 sa
->load_sum
= max_t(s64
, sa
->load_sum
- r
* LOAD_AVG_MAX
, 0);
2892 if (atomic_long_read(&cfs_rq
->removed_util_avg
)) {
2893 long r
= atomic_long_xchg(&cfs_rq
->removed_util_avg
, 0);
2894 sa
->util_avg
= max_t(long, sa
->util_avg
- r
, 0);
2895 sa
->util_sum
= max_t(s32
, sa
->util_sum
- r
* LOAD_AVG_MAX
, 0);
2899 decayed
= __update_load_avg(now
, cpu
, sa
,
2900 scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->curr
!= NULL
, cfs_rq
);
2902 #ifndef CONFIG_64BIT
2904 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
2907 if (cpu
== smp_processor_id() && &rq
->cfs
== cfs_rq
&&
2908 (decayed
|| removed_util
)) {
2909 unsigned long max
= rq
->cpu_capacity_orig
;
2912 * There are a few boundary cases this might miss but it should
2913 * get called often enough that that should (hopefully) not be
2914 * a real problem -- added to that it only calls on the local
2915 * CPU, so if we enqueue remotely we'll miss an update, but
2916 * the next tick/schedule should update.
2918 * It will not get called when we go idle, because the idle
2919 * thread is a different class (!fair), nor will the utilization
2920 * number include things like RT tasks.
2922 * As is, the util number is not freq-invariant (we'd have to
2923 * implement arch_scale_freq_capacity() for that).
2927 cpufreq_update_util(rq_clock(rq
),
2928 min(sa
->util_avg
, max
), max
);
2931 return decayed
|| removed_load
;
2934 /* Update task and its cfs_rq load average */
2935 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
)
2937 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
2938 u64 now
= cfs_rq_clock_task(cfs_rq
);
2939 struct rq
*rq
= rq_of(cfs_rq
);
2940 int cpu
= cpu_of(rq
);
2943 * Track task load average for carrying it to new CPU after migrated, and
2944 * track group sched_entity load average for task_h_load calc in migration
2946 __update_load_avg(now
, cpu
, &se
->avg
,
2947 se
->on_rq
* scale_load_down(se
->load
.weight
),
2948 cfs_rq
->curr
== se
, NULL
);
2950 if (update_cfs_rq_load_avg(now
, cfs_rq
) && update_tg
)
2951 update_tg_load_avg(cfs_rq
, 0);
2954 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2956 if (!sched_feat(ATTACH_AGE_LOAD
))
2960 * If we got migrated (either between CPUs or between cgroups) we'll
2961 * have aged the average right before clearing @last_update_time.
2963 if (se
->avg
.last_update_time
) {
2964 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2965 &se
->avg
, 0, 0, NULL
);
2968 * XXX: we could have just aged the entire load away if we've been
2969 * absent from the fair class for too long.
2974 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
2975 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
2976 cfs_rq
->avg
.load_sum
+= se
->avg
.load_sum
;
2977 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
2978 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
2981 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2983 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
2984 &se
->avg
, se
->on_rq
* scale_load_down(se
->load
.weight
),
2985 cfs_rq
->curr
== se
, NULL
);
2987 cfs_rq
->avg
.load_avg
= max_t(long, cfs_rq
->avg
.load_avg
- se
->avg
.load_avg
, 0);
2988 cfs_rq
->avg
.load_sum
= max_t(s64
, cfs_rq
->avg
.load_sum
- se
->avg
.load_sum
, 0);
2989 cfs_rq
->avg
.util_avg
= max_t(long, cfs_rq
->avg
.util_avg
- se
->avg
.util_avg
, 0);
2990 cfs_rq
->avg
.util_sum
= max_t(s32
, cfs_rq
->avg
.util_sum
- se
->avg
.util_sum
, 0);
2993 /* Add the load generated by se into cfs_rq's load average */
2995 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2997 struct sched_avg
*sa
= &se
->avg
;
2998 u64 now
= cfs_rq_clock_task(cfs_rq
);
2999 int migrated
, decayed
;
3001 migrated
= !sa
->last_update_time
;
3003 __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
3004 se
->on_rq
* scale_load_down(se
->load
.weight
),
3005 cfs_rq
->curr
== se
, NULL
);
3008 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
);
3010 cfs_rq
->runnable_load_avg
+= sa
->load_avg
;
3011 cfs_rq
->runnable_load_sum
+= sa
->load_sum
;
3014 attach_entity_load_avg(cfs_rq
, se
);
3016 if (decayed
|| migrated
)
3017 update_tg_load_avg(cfs_rq
, 0);
3020 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3022 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3024 update_load_avg(se
, 1);
3026 cfs_rq
->runnable_load_avg
=
3027 max_t(long, cfs_rq
->runnable_load_avg
- se
->avg
.load_avg
, 0);
3028 cfs_rq
->runnable_load_sum
=
3029 max_t(s64
, cfs_rq
->runnable_load_sum
- se
->avg
.load_sum
, 0);
3032 #ifndef CONFIG_64BIT
3033 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3035 u64 last_update_time_copy
;
3036 u64 last_update_time
;
3039 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3041 last_update_time
= cfs_rq
->avg
.last_update_time
;
3042 } while (last_update_time
!= last_update_time_copy
);
3044 return last_update_time
;
3047 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3049 return cfs_rq
->avg
.last_update_time
;
3054 * Task first catches up with cfs_rq, and then subtract
3055 * itself from the cfs_rq (task must be off the queue now).
3057 void remove_entity_load_avg(struct sched_entity
*se
)
3059 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3060 u64 last_update_time
;
3063 * Newly created task or never used group entity should not be removed
3064 * from its (source) cfs_rq
3066 if (se
->avg
.last_update_time
== 0)
3069 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3071 __update_load_avg(last_update_time
, cpu_of(rq_of(cfs_rq
)), &se
->avg
, 0, 0, NULL
);
3072 atomic_long_add(se
->avg
.load_avg
, &cfs_rq
->removed_load_avg
);
3073 atomic_long_add(se
->avg
.util_avg
, &cfs_rq
->removed_util_avg
);
3076 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
)
3078 return cfs_rq
->runnable_load_avg
;
3081 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3083 return cfs_rq
->avg
.load_avg
;
3086 static int idle_balance(struct rq
*this_rq
);
3088 #else /* CONFIG_SMP */
3090 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
) {}
3092 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3094 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3095 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
3098 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3100 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3102 static inline int idle_balance(struct rq
*rq
)
3107 #endif /* CONFIG_SMP */
3109 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3111 #ifdef CONFIG_SCHEDSTATS
3112 struct task_struct
*tsk
= NULL
;
3114 if (entity_is_task(se
))
3117 if (se
->statistics
.sleep_start
) {
3118 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.sleep_start
;
3123 if (unlikely(delta
> se
->statistics
.sleep_max
))
3124 se
->statistics
.sleep_max
= delta
;
3126 se
->statistics
.sleep_start
= 0;
3127 se
->statistics
.sum_sleep_runtime
+= delta
;
3130 account_scheduler_latency(tsk
, delta
>> 10, 1);
3131 trace_sched_stat_sleep(tsk
, delta
);
3134 if (se
->statistics
.block_start
) {
3135 u64 delta
= rq_clock(rq_of(cfs_rq
)) - se
->statistics
.block_start
;
3140 if (unlikely(delta
> se
->statistics
.block_max
))
3141 se
->statistics
.block_max
= delta
;
3143 se
->statistics
.block_start
= 0;
3144 se
->statistics
.sum_sleep_runtime
+= delta
;
3147 if (tsk
->in_iowait
) {
3148 se
->statistics
.iowait_sum
+= delta
;
3149 se
->statistics
.iowait_count
++;
3150 trace_sched_stat_iowait(tsk
, delta
);
3153 trace_sched_stat_blocked(tsk
, delta
);
3156 * Blocking time is in units of nanosecs, so shift by
3157 * 20 to get a milliseconds-range estimation of the
3158 * amount of time that the task spent sleeping:
3160 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
3161 profile_hits(SLEEP_PROFILING
,
3162 (void *)get_wchan(tsk
),
3165 account_scheduler_latency(tsk
, delta
>> 10, 0);
3171 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3173 #ifdef CONFIG_SCHED_DEBUG
3174 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3179 if (d
> 3*sysctl_sched_latency
)
3180 schedstat_inc(cfs_rq
, nr_spread_over
);
3185 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3187 u64 vruntime
= cfs_rq
->min_vruntime
;
3190 * The 'current' period is already promised to the current tasks,
3191 * however the extra weight of the new task will slow them down a
3192 * little, place the new task so that it fits in the slot that
3193 * stays open at the end.
3195 if (initial
&& sched_feat(START_DEBIT
))
3196 vruntime
+= sched_vslice(cfs_rq
, se
);
3198 /* sleeps up to a single latency don't count. */
3200 unsigned long thresh
= sysctl_sched_latency
;
3203 * Halve their sleep time's effect, to allow
3204 * for a gentler effect of sleepers:
3206 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3212 /* ensure we never gain time by being placed backwards. */
3213 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3216 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3218 static inline void check_schedstat_required(void)
3220 #ifdef CONFIG_SCHEDSTATS
3221 if (schedstat_enabled())
3224 /* Force schedstat enabled if a dependent tracepoint is active */
3225 if (trace_sched_stat_wait_enabled() ||
3226 trace_sched_stat_sleep_enabled() ||
3227 trace_sched_stat_iowait_enabled() ||
3228 trace_sched_stat_blocked_enabled() ||
3229 trace_sched_stat_runtime_enabled()) {
3230 pr_warn_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3231 "stat_blocked and stat_runtime require the "
3232 "kernel parameter schedstats=enabled or "
3233 "kernel.sched_schedstats=1\n");
3239 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3241 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_WAKING
);
3242 bool curr
= cfs_rq
->curr
== se
;
3245 * If we're the current task, we must renormalise before calling
3249 se
->vruntime
+= cfs_rq
->min_vruntime
;
3251 update_curr(cfs_rq
);
3254 * Otherwise, renormalise after, such that we're placed at the current
3255 * moment in time, instead of some random moment in the past.
3257 if (renorm
&& !curr
)
3258 se
->vruntime
+= cfs_rq
->min_vruntime
;
3260 enqueue_entity_load_avg(cfs_rq
, se
);
3261 account_entity_enqueue(cfs_rq
, se
);
3262 update_cfs_shares(cfs_rq
);
3264 if (flags
& ENQUEUE_WAKEUP
) {
3265 place_entity(cfs_rq
, se
, 0);
3266 if (schedstat_enabled())
3267 enqueue_sleeper(cfs_rq
, se
);
3270 check_schedstat_required();
3271 if (schedstat_enabled()) {
3272 update_stats_enqueue(cfs_rq
, se
);
3273 check_spread(cfs_rq
, se
);
3276 __enqueue_entity(cfs_rq
, se
);
3279 if (cfs_rq
->nr_running
== 1) {
3280 list_add_leaf_cfs_rq(cfs_rq
);
3281 check_enqueue_throttle(cfs_rq
);
3285 static void __clear_buddies_last(struct sched_entity
*se
)
3287 for_each_sched_entity(se
) {
3288 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3289 if (cfs_rq
->last
!= se
)
3292 cfs_rq
->last
= NULL
;
3296 static void __clear_buddies_next(struct sched_entity
*se
)
3298 for_each_sched_entity(se
) {
3299 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3300 if (cfs_rq
->next
!= se
)
3303 cfs_rq
->next
= NULL
;
3307 static void __clear_buddies_skip(struct sched_entity
*se
)
3309 for_each_sched_entity(se
) {
3310 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3311 if (cfs_rq
->skip
!= se
)
3314 cfs_rq
->skip
= NULL
;
3318 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3320 if (cfs_rq
->last
== se
)
3321 __clear_buddies_last(se
);
3323 if (cfs_rq
->next
== se
)
3324 __clear_buddies_next(se
);
3326 if (cfs_rq
->skip
== se
)
3327 __clear_buddies_skip(se
);
3330 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3333 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3336 * Update run-time statistics of the 'current'.
3338 update_curr(cfs_rq
);
3339 dequeue_entity_load_avg(cfs_rq
, se
);
3341 if (schedstat_enabled())
3342 update_stats_dequeue(cfs_rq
, se
, flags
);
3344 clear_buddies(cfs_rq
, se
);
3346 if (se
!= cfs_rq
->curr
)
3347 __dequeue_entity(cfs_rq
, se
);
3349 account_entity_dequeue(cfs_rq
, se
);
3352 * Normalize the entity after updating the min_vruntime because the
3353 * update can refer to the ->curr item and we need to reflect this
3354 * movement in our normalized position.
3356 if (!(flags
& DEQUEUE_SLEEP
))
3357 se
->vruntime
-= cfs_rq
->min_vruntime
;
3359 /* return excess runtime on last dequeue */
3360 return_cfs_rq_runtime(cfs_rq
);
3362 update_min_vruntime(cfs_rq
);
3363 update_cfs_shares(cfs_rq
);
3367 * Preempt the current task with a newly woken task if needed:
3370 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3372 unsigned long ideal_runtime
, delta_exec
;
3373 struct sched_entity
*se
;
3376 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3377 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3378 if (delta_exec
> ideal_runtime
) {
3379 resched_curr(rq_of(cfs_rq
));
3381 * The current task ran long enough, ensure it doesn't get
3382 * re-elected due to buddy favours.
3384 clear_buddies(cfs_rq
, curr
);
3389 * Ensure that a task that missed wakeup preemption by a
3390 * narrow margin doesn't have to wait for a full slice.
3391 * This also mitigates buddy induced latencies under load.
3393 if (delta_exec
< sysctl_sched_min_granularity
)
3396 se
= __pick_first_entity(cfs_rq
);
3397 delta
= curr
->vruntime
- se
->vruntime
;
3402 if (delta
> ideal_runtime
)
3403 resched_curr(rq_of(cfs_rq
));
3407 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3409 /* 'current' is not kept within the tree. */
3412 * Any task has to be enqueued before it get to execute on
3413 * a CPU. So account for the time it spent waiting on the
3416 if (schedstat_enabled())
3417 update_stats_wait_end(cfs_rq
, se
);
3418 __dequeue_entity(cfs_rq
, se
);
3419 update_load_avg(se
, 1);
3422 update_stats_curr_start(cfs_rq
, se
);
3424 #ifdef CONFIG_SCHEDSTATS
3426 * Track our maximum slice length, if the CPU's load is at
3427 * least twice that of our own weight (i.e. dont track it
3428 * when there are only lesser-weight tasks around):
3430 if (schedstat_enabled() && rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3431 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
3432 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
3435 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3439 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3442 * Pick the next process, keeping these things in mind, in this order:
3443 * 1) keep things fair between processes/task groups
3444 * 2) pick the "next" process, since someone really wants that to run
3445 * 3) pick the "last" process, for cache locality
3446 * 4) do not run the "skip" process, if something else is available
3448 static struct sched_entity
*
3449 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3451 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
3452 struct sched_entity
*se
;
3455 * If curr is set we have to see if its left of the leftmost entity
3456 * still in the tree, provided there was anything in the tree at all.
3458 if (!left
|| (curr
&& entity_before(curr
, left
)))
3461 se
= left
; /* ideally we run the leftmost entity */
3464 * Avoid running the skip buddy, if running something else can
3465 * be done without getting too unfair.
3467 if (cfs_rq
->skip
== se
) {
3468 struct sched_entity
*second
;
3471 second
= __pick_first_entity(cfs_rq
);
3473 second
= __pick_next_entity(se
);
3474 if (!second
|| (curr
&& entity_before(curr
, second
)))
3478 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
3483 * Prefer last buddy, try to return the CPU to a preempted task.
3485 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
3489 * Someone really wants this to run. If it's not unfair, run it.
3491 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
3494 clear_buddies(cfs_rq
, se
);
3499 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3501 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
3504 * If still on the runqueue then deactivate_task()
3505 * was not called and update_curr() has to be done:
3508 update_curr(cfs_rq
);
3510 /* throttle cfs_rqs exceeding runtime */
3511 check_cfs_rq_runtime(cfs_rq
);
3513 if (schedstat_enabled()) {
3514 check_spread(cfs_rq
, prev
);
3516 update_stats_wait_start(cfs_rq
, prev
);
3520 /* Put 'current' back into the tree. */
3521 __enqueue_entity(cfs_rq
, prev
);
3522 /* in !on_rq case, update occurred at dequeue */
3523 update_load_avg(prev
, 0);
3525 cfs_rq
->curr
= NULL
;
3529 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
3532 * Update run-time statistics of the 'current'.
3534 update_curr(cfs_rq
);
3537 * Ensure that runnable average is periodically updated.
3539 update_load_avg(curr
, 1);
3540 update_cfs_shares(cfs_rq
);
3542 #ifdef CONFIG_SCHED_HRTICK
3544 * queued ticks are scheduled to match the slice, so don't bother
3545 * validating it and just reschedule.
3548 resched_curr(rq_of(cfs_rq
));
3552 * don't let the period tick interfere with the hrtick preemption
3554 if (!sched_feat(DOUBLE_TICK
) &&
3555 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3559 if (cfs_rq
->nr_running
> 1)
3560 check_preempt_tick(cfs_rq
, curr
);
3564 /**************************************************
3565 * CFS bandwidth control machinery
3568 #ifdef CONFIG_CFS_BANDWIDTH
3570 #ifdef HAVE_JUMP_LABEL
3571 static struct static_key __cfs_bandwidth_used
;
3573 static inline bool cfs_bandwidth_used(void)
3575 return static_key_false(&__cfs_bandwidth_used
);
3578 void cfs_bandwidth_usage_inc(void)
3580 static_key_slow_inc(&__cfs_bandwidth_used
);
3583 void cfs_bandwidth_usage_dec(void)
3585 static_key_slow_dec(&__cfs_bandwidth_used
);
3587 #else /* HAVE_JUMP_LABEL */
3588 static bool cfs_bandwidth_used(void)
3593 void cfs_bandwidth_usage_inc(void) {}
3594 void cfs_bandwidth_usage_dec(void) {}
3595 #endif /* HAVE_JUMP_LABEL */
3598 * default period for cfs group bandwidth.
3599 * default: 0.1s, units: nanoseconds
3601 static inline u64
default_cfs_period(void)
3603 return 100000000ULL;
3606 static inline u64
sched_cfs_bandwidth_slice(void)
3608 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3612 * Replenish runtime according to assigned quota and update expiration time.
3613 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3614 * additional synchronization around rq->lock.
3616 * requires cfs_b->lock
3618 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3622 if (cfs_b
->quota
== RUNTIME_INF
)
3625 now
= sched_clock_cpu(smp_processor_id());
3626 cfs_b
->runtime
= cfs_b
->quota
;
3627 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3630 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3632 return &tg
->cfs_bandwidth
;
3635 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3636 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3638 if (unlikely(cfs_rq
->throttle_count
))
3639 return cfs_rq
->throttled_clock_task
;
3641 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3644 /* returns 0 on failure to allocate runtime */
3645 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3647 struct task_group
*tg
= cfs_rq
->tg
;
3648 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3649 u64 amount
= 0, min_amount
, expires
;
3651 /* note: this is a positive sum as runtime_remaining <= 0 */
3652 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3654 raw_spin_lock(&cfs_b
->lock
);
3655 if (cfs_b
->quota
== RUNTIME_INF
)
3656 amount
= min_amount
;
3658 start_cfs_bandwidth(cfs_b
);
3660 if (cfs_b
->runtime
> 0) {
3661 amount
= min(cfs_b
->runtime
, min_amount
);
3662 cfs_b
->runtime
-= amount
;
3666 expires
= cfs_b
->runtime_expires
;
3667 raw_spin_unlock(&cfs_b
->lock
);
3669 cfs_rq
->runtime_remaining
+= amount
;
3671 * we may have advanced our local expiration to account for allowed
3672 * spread between our sched_clock and the one on which runtime was
3675 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3676 cfs_rq
->runtime_expires
= expires
;
3678 return cfs_rq
->runtime_remaining
> 0;
3682 * Note: This depends on the synchronization provided by sched_clock and the
3683 * fact that rq->clock snapshots this value.
3685 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3687 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3689 /* if the deadline is ahead of our clock, nothing to do */
3690 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3693 if (cfs_rq
->runtime_remaining
< 0)
3697 * If the local deadline has passed we have to consider the
3698 * possibility that our sched_clock is 'fast' and the global deadline
3699 * has not truly expired.
3701 * Fortunately we can check determine whether this the case by checking
3702 * whether the global deadline has advanced. It is valid to compare
3703 * cfs_b->runtime_expires without any locks since we only care about
3704 * exact equality, so a partial write will still work.
3707 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
3708 /* extend local deadline, drift is bounded above by 2 ticks */
3709 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3711 /* global deadline is ahead, expiration has passed */
3712 cfs_rq
->runtime_remaining
= 0;
3716 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3718 /* dock delta_exec before expiring quota (as it could span periods) */
3719 cfs_rq
->runtime_remaining
-= delta_exec
;
3720 expire_cfs_rq_runtime(cfs_rq
);
3722 if (likely(cfs_rq
->runtime_remaining
> 0))
3726 * if we're unable to extend our runtime we resched so that the active
3727 * hierarchy can be throttled
3729 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3730 resched_curr(rq_of(cfs_rq
));
3733 static __always_inline
3734 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3736 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3739 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3742 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3744 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3747 /* check whether cfs_rq, or any parent, is throttled */
3748 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3750 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3754 * Ensure that neither of the group entities corresponding to src_cpu or
3755 * dest_cpu are members of a throttled hierarchy when performing group
3756 * load-balance operations.
3758 static inline int throttled_lb_pair(struct task_group
*tg
,
3759 int src_cpu
, int dest_cpu
)
3761 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3763 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3764 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3766 return throttled_hierarchy(src_cfs_rq
) ||
3767 throttled_hierarchy(dest_cfs_rq
);
3770 /* updated child weight may affect parent so we have to do this bottom up */
3771 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3773 struct rq
*rq
= data
;
3774 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3776 cfs_rq
->throttle_count
--;
3778 if (!cfs_rq
->throttle_count
) {
3779 /* adjust cfs_rq_clock_task() */
3780 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3781 cfs_rq
->throttled_clock_task
;
3788 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3790 struct rq
*rq
= data
;
3791 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3793 /* group is entering throttled state, stop time */
3794 if (!cfs_rq
->throttle_count
)
3795 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3796 cfs_rq
->throttle_count
++;
3801 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3803 struct rq
*rq
= rq_of(cfs_rq
);
3804 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3805 struct sched_entity
*se
;
3806 long task_delta
, dequeue
= 1;
3809 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3811 /* freeze hierarchy runnable averages while throttled */
3813 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3816 task_delta
= cfs_rq
->h_nr_running
;
3817 for_each_sched_entity(se
) {
3818 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3819 /* throttled entity or throttle-on-deactivate */
3824 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3825 qcfs_rq
->h_nr_running
-= task_delta
;
3827 if (qcfs_rq
->load
.weight
)
3832 sub_nr_running(rq
, task_delta
);
3834 cfs_rq
->throttled
= 1;
3835 cfs_rq
->throttled_clock
= rq_clock(rq
);
3836 raw_spin_lock(&cfs_b
->lock
);
3837 empty
= list_empty(&cfs_b
->throttled_cfs_rq
);
3840 * Add to the _head_ of the list, so that an already-started
3841 * distribute_cfs_runtime will not see us
3843 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3846 * If we're the first throttled task, make sure the bandwidth
3850 start_cfs_bandwidth(cfs_b
);
3852 raw_spin_unlock(&cfs_b
->lock
);
3855 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3857 struct rq
*rq
= rq_of(cfs_rq
);
3858 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3859 struct sched_entity
*se
;
3863 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3865 cfs_rq
->throttled
= 0;
3867 update_rq_clock(rq
);
3869 raw_spin_lock(&cfs_b
->lock
);
3870 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3871 list_del_rcu(&cfs_rq
->throttled_list
);
3872 raw_spin_unlock(&cfs_b
->lock
);
3874 /* update hierarchical throttle state */
3875 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3877 if (!cfs_rq
->load
.weight
)
3880 task_delta
= cfs_rq
->h_nr_running
;
3881 for_each_sched_entity(se
) {
3885 cfs_rq
= cfs_rq_of(se
);
3887 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3888 cfs_rq
->h_nr_running
+= task_delta
;
3890 if (cfs_rq_throttled(cfs_rq
))
3895 add_nr_running(rq
, task_delta
);
3897 /* determine whether we need to wake up potentially idle cpu */
3898 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
3902 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
3903 u64 remaining
, u64 expires
)
3905 struct cfs_rq
*cfs_rq
;
3907 u64 starting_runtime
= remaining
;
3910 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
3912 struct rq
*rq
= rq_of(cfs_rq
);
3914 raw_spin_lock(&rq
->lock
);
3915 if (!cfs_rq_throttled(cfs_rq
))
3918 runtime
= -cfs_rq
->runtime_remaining
+ 1;
3919 if (runtime
> remaining
)
3920 runtime
= remaining
;
3921 remaining
-= runtime
;
3923 cfs_rq
->runtime_remaining
+= runtime
;
3924 cfs_rq
->runtime_expires
= expires
;
3926 /* we check whether we're throttled above */
3927 if (cfs_rq
->runtime_remaining
> 0)
3928 unthrottle_cfs_rq(cfs_rq
);
3931 raw_spin_unlock(&rq
->lock
);
3938 return starting_runtime
- remaining
;
3942 * Responsible for refilling a task_group's bandwidth and unthrottling its
3943 * cfs_rqs as appropriate. If there has been no activity within the last
3944 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
3945 * used to track this state.
3947 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
3949 u64 runtime
, runtime_expires
;
3952 /* no need to continue the timer with no bandwidth constraint */
3953 if (cfs_b
->quota
== RUNTIME_INF
)
3954 goto out_deactivate
;
3956 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3957 cfs_b
->nr_periods
+= overrun
;
3960 * idle depends on !throttled (for the case of a large deficit), and if
3961 * we're going inactive then everything else can be deferred
3963 if (cfs_b
->idle
&& !throttled
)
3964 goto out_deactivate
;
3966 __refill_cfs_bandwidth_runtime(cfs_b
);
3969 /* mark as potentially idle for the upcoming period */
3974 /* account preceding periods in which throttling occurred */
3975 cfs_b
->nr_throttled
+= overrun
;
3977 runtime_expires
= cfs_b
->runtime_expires
;
3980 * This check is repeated as we are holding onto the new bandwidth while
3981 * we unthrottle. This can potentially race with an unthrottled group
3982 * trying to acquire new bandwidth from the global pool. This can result
3983 * in us over-using our runtime if it is all used during this loop, but
3984 * only by limited amounts in that extreme case.
3986 while (throttled
&& cfs_b
->runtime
> 0) {
3987 runtime
= cfs_b
->runtime
;
3988 raw_spin_unlock(&cfs_b
->lock
);
3989 /* we can't nest cfs_b->lock while distributing bandwidth */
3990 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
3992 raw_spin_lock(&cfs_b
->lock
);
3994 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
3996 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4000 * While we are ensured activity in the period following an
4001 * unthrottle, this also covers the case in which the new bandwidth is
4002 * insufficient to cover the existing bandwidth deficit. (Forcing the
4003 * timer to remain active while there are any throttled entities.)
4013 /* a cfs_rq won't donate quota below this amount */
4014 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
4015 /* minimum remaining period time to redistribute slack quota */
4016 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
4017 /* how long we wait to gather additional slack before distributing */
4018 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
4021 * Are we near the end of the current quota period?
4023 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4024 * hrtimer base being cleared by hrtimer_start. In the case of
4025 * migrate_hrtimers, base is never cleared, so we are fine.
4027 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
4029 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
4032 /* if the call-back is running a quota refresh is already occurring */
4033 if (hrtimer_callback_running(refresh_timer
))
4036 /* is a quota refresh about to occur? */
4037 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
4038 if (remaining
< min_expire
)
4044 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
4046 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
4048 /* if there's a quota refresh soon don't bother with slack */
4049 if (runtime_refresh_within(cfs_b
, min_left
))
4052 hrtimer_start(&cfs_b
->slack_timer
,
4053 ns_to_ktime(cfs_bandwidth_slack_period
),
4057 /* we know any runtime found here is valid as update_curr() precedes return */
4058 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4060 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4061 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
4063 if (slack_runtime
<= 0)
4066 raw_spin_lock(&cfs_b
->lock
);
4067 if (cfs_b
->quota
!= RUNTIME_INF
&&
4068 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
4069 cfs_b
->runtime
+= slack_runtime
;
4071 /* we are under rq->lock, defer unthrottling using a timer */
4072 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
4073 !list_empty(&cfs_b
->throttled_cfs_rq
))
4074 start_cfs_slack_bandwidth(cfs_b
);
4076 raw_spin_unlock(&cfs_b
->lock
);
4078 /* even if it's not valid for return we don't want to try again */
4079 cfs_rq
->runtime_remaining
-= slack_runtime
;
4082 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4084 if (!cfs_bandwidth_used())
4087 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
4090 __return_cfs_rq_runtime(cfs_rq
);
4094 * This is done with a timer (instead of inline with bandwidth return) since
4095 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4097 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
4099 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
4102 /* confirm we're still not at a refresh boundary */
4103 raw_spin_lock(&cfs_b
->lock
);
4104 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
4105 raw_spin_unlock(&cfs_b
->lock
);
4109 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
4110 runtime
= cfs_b
->runtime
;
4112 expires
= cfs_b
->runtime_expires
;
4113 raw_spin_unlock(&cfs_b
->lock
);
4118 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
4120 raw_spin_lock(&cfs_b
->lock
);
4121 if (expires
== cfs_b
->runtime_expires
)
4122 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4123 raw_spin_unlock(&cfs_b
->lock
);
4127 * When a group wakes up we want to make sure that its quota is not already
4128 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4129 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4131 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
4133 if (!cfs_bandwidth_used())
4136 /* an active group must be handled by the update_curr()->put() path */
4137 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
4140 /* ensure the group is not already throttled */
4141 if (cfs_rq_throttled(cfs_rq
))
4144 /* update runtime allocation */
4145 account_cfs_rq_runtime(cfs_rq
, 0);
4146 if (cfs_rq
->runtime_remaining
<= 0)
4147 throttle_cfs_rq(cfs_rq
);
4150 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4151 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4153 if (!cfs_bandwidth_used())
4156 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
4160 * it's possible for a throttled entity to be forced into a running
4161 * state (e.g. set_curr_task), in this case we're finished.
4163 if (cfs_rq_throttled(cfs_rq
))
4166 throttle_cfs_rq(cfs_rq
);
4170 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
4172 struct cfs_bandwidth
*cfs_b
=
4173 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
4175 do_sched_cfs_slack_timer(cfs_b
);
4177 return HRTIMER_NORESTART
;
4180 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
4182 struct cfs_bandwidth
*cfs_b
=
4183 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4187 raw_spin_lock(&cfs_b
->lock
);
4189 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
4193 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4196 cfs_b
->period_active
= 0;
4197 raw_spin_unlock(&cfs_b
->lock
);
4199 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4202 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4204 raw_spin_lock_init(&cfs_b
->lock
);
4206 cfs_b
->quota
= RUNTIME_INF
;
4207 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4209 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4210 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
4211 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4212 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4213 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4216 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4218 cfs_rq
->runtime_enabled
= 0;
4219 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4222 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4224 lockdep_assert_held(&cfs_b
->lock
);
4226 if (!cfs_b
->period_active
) {
4227 cfs_b
->period_active
= 1;
4228 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
4229 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
4233 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4235 /* init_cfs_bandwidth() was not called */
4236 if (!cfs_b
->throttled_cfs_rq
.next
)
4239 hrtimer_cancel(&cfs_b
->period_timer
);
4240 hrtimer_cancel(&cfs_b
->slack_timer
);
4243 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4245 struct cfs_rq
*cfs_rq
;
4247 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4248 struct cfs_bandwidth
*cfs_b
= &cfs_rq
->tg
->cfs_bandwidth
;
4250 raw_spin_lock(&cfs_b
->lock
);
4251 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4252 raw_spin_unlock(&cfs_b
->lock
);
4256 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4258 struct cfs_rq
*cfs_rq
;
4260 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4261 if (!cfs_rq
->runtime_enabled
)
4265 * clock_task is not advancing so we just need to make sure
4266 * there's some valid quota amount
4268 cfs_rq
->runtime_remaining
= 1;
4270 * Offline rq is schedulable till cpu is completely disabled
4271 * in take_cpu_down(), so we prevent new cfs throttling here.
4273 cfs_rq
->runtime_enabled
= 0;
4275 if (cfs_rq_throttled(cfs_rq
))
4276 unthrottle_cfs_rq(cfs_rq
);
4280 #else /* CONFIG_CFS_BANDWIDTH */
4281 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4283 return rq_clock_task(rq_of(cfs_rq
));
4286 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4287 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4288 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4289 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4291 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4296 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4301 static inline int throttled_lb_pair(struct task_group
*tg
,
4302 int src_cpu
, int dest_cpu
)
4307 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4309 #ifdef CONFIG_FAIR_GROUP_SCHED
4310 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4313 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4317 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4318 static inline void update_runtime_enabled(struct rq
*rq
) {}
4319 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4321 #endif /* CONFIG_CFS_BANDWIDTH */
4323 /**************************************************
4324 * CFS operations on tasks:
4327 #ifdef CONFIG_SCHED_HRTICK
4328 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4330 struct sched_entity
*se
= &p
->se
;
4331 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4333 WARN_ON(task_rq(p
) != rq
);
4335 if (cfs_rq
->nr_running
> 1) {
4336 u64 slice
= sched_slice(cfs_rq
, se
);
4337 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4338 s64 delta
= slice
- ran
;
4345 hrtick_start(rq
, delta
);
4350 * called from enqueue/dequeue and updates the hrtick when the
4351 * current task is from our class and nr_running is low enough
4354 static void hrtick_update(struct rq
*rq
)
4356 struct task_struct
*curr
= rq
->curr
;
4358 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4361 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4362 hrtick_start_fair(rq
, curr
);
4364 #else /* !CONFIG_SCHED_HRTICK */
4366 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4370 static inline void hrtick_update(struct rq
*rq
)
4376 * The enqueue_task method is called before nr_running is
4377 * increased. Here we update the fair scheduling stats and
4378 * then put the task into the rbtree:
4381 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4383 struct cfs_rq
*cfs_rq
;
4384 struct sched_entity
*se
= &p
->se
;
4386 for_each_sched_entity(se
) {
4389 cfs_rq
= cfs_rq_of(se
);
4390 enqueue_entity(cfs_rq
, se
, flags
);
4393 * end evaluation on encountering a throttled cfs_rq
4395 * note: in the case of encountering a throttled cfs_rq we will
4396 * post the final h_nr_running increment below.
4398 if (cfs_rq_throttled(cfs_rq
))
4400 cfs_rq
->h_nr_running
++;
4402 flags
= ENQUEUE_WAKEUP
;
4405 for_each_sched_entity(se
) {
4406 cfs_rq
= cfs_rq_of(se
);
4407 cfs_rq
->h_nr_running
++;
4409 if (cfs_rq_throttled(cfs_rq
))
4412 update_load_avg(se
, 1);
4413 update_cfs_shares(cfs_rq
);
4417 add_nr_running(rq
, 1);
4422 static void set_next_buddy(struct sched_entity
*se
);
4425 * The dequeue_task method is called before nr_running is
4426 * decreased. We remove the task from the rbtree and
4427 * update the fair scheduling stats:
4429 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4431 struct cfs_rq
*cfs_rq
;
4432 struct sched_entity
*se
= &p
->se
;
4433 int task_sleep
= flags
& DEQUEUE_SLEEP
;
4435 for_each_sched_entity(se
) {
4436 cfs_rq
= cfs_rq_of(se
);
4437 dequeue_entity(cfs_rq
, se
, flags
);
4440 * end evaluation on encountering a throttled cfs_rq
4442 * note: in the case of encountering a throttled cfs_rq we will
4443 * post the final h_nr_running decrement below.
4445 if (cfs_rq_throttled(cfs_rq
))
4447 cfs_rq
->h_nr_running
--;
4449 /* Don't dequeue parent if it has other entities besides us */
4450 if (cfs_rq
->load
.weight
) {
4452 * Bias pick_next to pick a task from this cfs_rq, as
4453 * p is sleeping when it is within its sched_slice.
4455 if (task_sleep
&& parent_entity(se
))
4456 set_next_buddy(parent_entity(se
));
4458 /* avoid re-evaluating load for this entity */
4459 se
= parent_entity(se
);
4462 flags
|= DEQUEUE_SLEEP
;
4465 for_each_sched_entity(se
) {
4466 cfs_rq
= cfs_rq_of(se
);
4467 cfs_rq
->h_nr_running
--;
4469 if (cfs_rq_throttled(cfs_rq
))
4472 update_load_avg(se
, 1);
4473 update_cfs_shares(cfs_rq
);
4477 sub_nr_running(rq
, 1);
4485 * per rq 'load' arrray crap; XXX kill this.
4489 * The exact cpuload calculated at every tick would be:
4491 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4493 * If a cpu misses updates for n ticks (as it was idle) and update gets
4494 * called on the n+1-th tick when cpu may be busy, then we have:
4496 * load_n = (1 - 1/2^i)^n * load_0
4497 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4499 * decay_load_missed() below does efficient calculation of
4501 * load' = (1 - 1/2^i)^n * load
4503 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4504 * This allows us to precompute the above in said factors, thereby allowing the
4505 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4506 * fixed_power_int())
4508 * The calculation is approximated on a 128 point scale.
4510 #define DEGRADE_SHIFT 7
4512 static const u8 degrade_zero_ticks
[CPU_LOAD_IDX_MAX
] = {0, 8, 32, 64, 128};
4513 static const u8 degrade_factor
[CPU_LOAD_IDX_MAX
][DEGRADE_SHIFT
+ 1] = {
4514 { 0, 0, 0, 0, 0, 0, 0, 0 },
4515 { 64, 32, 8, 0, 0, 0, 0, 0 },
4516 { 96, 72, 40, 12, 1, 0, 0, 0 },
4517 { 112, 98, 75, 43, 15, 1, 0, 0 },
4518 { 120, 112, 98, 76, 45, 16, 2, 0 }
4522 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4523 * would be when CPU is idle and so we just decay the old load without
4524 * adding any new load.
4526 static unsigned long
4527 decay_load_missed(unsigned long load
, unsigned long missed_updates
, int idx
)
4531 if (!missed_updates
)
4534 if (missed_updates
>= degrade_zero_ticks
[idx
])
4538 return load
>> missed_updates
;
4540 while (missed_updates
) {
4541 if (missed_updates
% 2)
4542 load
= (load
* degrade_factor
[idx
][j
]) >> DEGRADE_SHIFT
;
4544 missed_updates
>>= 1;
4551 * __update_cpu_load - update the rq->cpu_load[] statistics
4552 * @this_rq: The rq to update statistics for
4553 * @this_load: The current load
4554 * @pending_updates: The number of missed updates
4555 * @active: !0 for NOHZ_FULL
4557 * Update rq->cpu_load[] statistics. This function is usually called every
4558 * scheduler tick (TICK_NSEC).
4560 * This function computes a decaying average:
4562 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4564 * Because of NOHZ it might not get called on every tick which gives need for
4565 * the @pending_updates argument.
4567 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4568 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4569 * = A * (A * load[i]_n-2 + B) + B
4570 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4571 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4572 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4573 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4574 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4576 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4577 * any change in load would have resulted in the tick being turned back on.
4579 * For regular NOHZ, this reduces to:
4581 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4583 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4584 * term. See the @active paramter.
4586 static void __update_cpu_load(struct rq
*this_rq
, unsigned long this_load
,
4587 unsigned long pending_updates
, int active
)
4589 unsigned long tickless_load
= active
? this_rq
->cpu_load
[0] : 0;
4592 this_rq
->nr_load_updates
++;
4594 /* Update our load: */
4595 this_rq
->cpu_load
[0] = this_load
; /* Fasttrack for idx 0 */
4596 for (i
= 1, scale
= 2; i
< CPU_LOAD_IDX_MAX
; i
++, scale
+= scale
) {
4597 unsigned long old_load
, new_load
;
4599 /* scale is effectively 1 << i now, and >> i divides by scale */
4601 old_load
= this_rq
->cpu_load
[i
];
4602 old_load
= decay_load_missed(old_load
, pending_updates
- 1, i
);
4603 if (tickless_load
) {
4604 old_load
-= decay_load_missed(tickless_load
, pending_updates
- 1, i
);
4606 * old_load can never be a negative value because a
4607 * decayed tickless_load cannot be greater than the
4608 * original tickless_load.
4610 old_load
+= tickless_load
;
4612 new_load
= this_load
;
4614 * Round up the averaging division if load is increasing. This
4615 * prevents us from getting stuck on 9 if the load is 10, for
4618 if (new_load
> old_load
)
4619 new_load
+= scale
- 1;
4621 this_rq
->cpu_load
[i
] = (old_load
* (scale
- 1) + new_load
) >> i
;
4624 sched_avg_update(this_rq
);
4627 /* Used instead of source_load when we know the type == 0 */
4628 static unsigned long weighted_cpuload(const int cpu
)
4630 return cfs_rq_runnable_load_avg(&cpu_rq(cpu
)->cfs
);
4633 #ifdef CONFIG_NO_HZ_COMMON
4634 static void __update_cpu_load_nohz(struct rq
*this_rq
,
4635 unsigned long curr_jiffies
,
4639 unsigned long pending_updates
;
4641 pending_updates
= curr_jiffies
- this_rq
->last_load_update_tick
;
4642 if (pending_updates
) {
4643 this_rq
->last_load_update_tick
= curr_jiffies
;
4645 * In the regular NOHZ case, we were idle, this means load 0.
4646 * In the NOHZ_FULL case, we were non-idle, we should consider
4647 * its weighted load.
4649 __update_cpu_load(this_rq
, load
, pending_updates
, active
);
4654 * There is no sane way to deal with nohz on smp when using jiffies because the
4655 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4656 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4658 * Therefore we cannot use the delta approach from the regular tick since that
4659 * would seriously skew the load calculation. However we'll make do for those
4660 * updates happening while idle (nohz_idle_balance) or coming out of idle
4661 * (tick_nohz_idle_exit).
4663 * This means we might still be one tick off for nohz periods.
4667 * Called from nohz_idle_balance() to update the load ratings before doing the
4670 static void update_cpu_load_idle(struct rq
*this_rq
)
4673 * bail if there's load or we're actually up-to-date.
4675 if (weighted_cpuload(cpu_of(this_rq
)))
4678 __update_cpu_load_nohz(this_rq
, READ_ONCE(jiffies
), 0, 0);
4682 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
4684 void update_cpu_load_nohz(int active
)
4686 struct rq
*this_rq
= this_rq();
4687 unsigned long curr_jiffies
= READ_ONCE(jiffies
);
4688 unsigned long load
= active
? weighted_cpuload(cpu_of(this_rq
)) : 0;
4690 if (curr_jiffies
== this_rq
->last_load_update_tick
)
4693 raw_spin_lock(&this_rq
->lock
);
4694 __update_cpu_load_nohz(this_rq
, curr_jiffies
, load
, active
);
4695 raw_spin_unlock(&this_rq
->lock
);
4697 #endif /* CONFIG_NO_HZ */
4700 * Called from scheduler_tick()
4702 void update_cpu_load_active(struct rq
*this_rq
)
4704 unsigned long load
= weighted_cpuload(cpu_of(this_rq
));
4706 * See the mess around update_cpu_load_idle() / update_cpu_load_nohz().
4708 this_rq
->last_load_update_tick
= jiffies
;
4709 __update_cpu_load(this_rq
, load
, 1, 1);
4713 * Return a low guess at the load of a migration-source cpu weighted
4714 * according to the scheduling class and "nice" value.
4716 * We want to under-estimate the load of migration sources, to
4717 * balance conservatively.
4719 static unsigned long source_load(int cpu
, int type
)
4721 struct rq
*rq
= cpu_rq(cpu
);
4722 unsigned long total
= weighted_cpuload(cpu
);
4724 if (type
== 0 || !sched_feat(LB_BIAS
))
4727 return min(rq
->cpu_load
[type
-1], total
);
4731 * Return a high guess at the load of a migration-target cpu weighted
4732 * according to the scheduling class and "nice" value.
4734 static unsigned long target_load(int cpu
, int type
)
4736 struct rq
*rq
= cpu_rq(cpu
);
4737 unsigned long total
= weighted_cpuload(cpu
);
4739 if (type
== 0 || !sched_feat(LB_BIAS
))
4742 return max(rq
->cpu_load
[type
-1], total
);
4745 static unsigned long capacity_of(int cpu
)
4747 return cpu_rq(cpu
)->cpu_capacity
;
4750 static unsigned long capacity_orig_of(int cpu
)
4752 return cpu_rq(cpu
)->cpu_capacity_orig
;
4755 static unsigned long cpu_avg_load_per_task(int cpu
)
4757 struct rq
*rq
= cpu_rq(cpu
);
4758 unsigned long nr_running
= READ_ONCE(rq
->cfs
.h_nr_running
);
4759 unsigned long load_avg
= weighted_cpuload(cpu
);
4762 return load_avg
/ nr_running
;
4767 static void record_wakee(struct task_struct
*p
)
4770 * Rough decay (wiping) for cost saving, don't worry
4771 * about the boundary, really active task won't care
4774 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
4775 current
->wakee_flips
>>= 1;
4776 current
->wakee_flip_decay_ts
= jiffies
;
4779 if (current
->last_wakee
!= p
) {
4780 current
->last_wakee
= p
;
4781 current
->wakee_flips
++;
4785 static void task_waking_fair(struct task_struct
*p
)
4787 struct sched_entity
*se
= &p
->se
;
4788 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4791 #ifndef CONFIG_64BIT
4792 u64 min_vruntime_copy
;
4795 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
4797 min_vruntime
= cfs_rq
->min_vruntime
;
4798 } while (min_vruntime
!= min_vruntime_copy
);
4800 min_vruntime
= cfs_rq
->min_vruntime
;
4803 se
->vruntime
-= min_vruntime
;
4807 #ifdef CONFIG_FAIR_GROUP_SCHED
4809 * effective_load() calculates the load change as seen from the root_task_group
4811 * Adding load to a group doesn't make a group heavier, but can cause movement
4812 * of group shares between cpus. Assuming the shares were perfectly aligned one
4813 * can calculate the shift in shares.
4815 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4816 * on this @cpu and results in a total addition (subtraction) of @wg to the
4817 * total group weight.
4819 * Given a runqueue weight distribution (rw_i) we can compute a shares
4820 * distribution (s_i) using:
4822 * s_i = rw_i / \Sum rw_j (1)
4824 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4825 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4826 * shares distribution (s_i):
4828 * rw_i = { 2, 4, 1, 0 }
4829 * s_i = { 2/7, 4/7, 1/7, 0 }
4831 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4832 * task used to run on and the CPU the waker is running on), we need to
4833 * compute the effect of waking a task on either CPU and, in case of a sync
4834 * wakeup, compute the effect of the current task going to sleep.
4836 * So for a change of @wl to the local @cpu with an overall group weight change
4837 * of @wl we can compute the new shares distribution (s'_i) using:
4839 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4841 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4842 * differences in waking a task to CPU 0. The additional task changes the
4843 * weight and shares distributions like:
4845 * rw'_i = { 3, 4, 1, 0 }
4846 * s'_i = { 3/8, 4/8, 1/8, 0 }
4848 * We can then compute the difference in effective weight by using:
4850 * dw_i = S * (s'_i - s_i) (3)
4852 * Where 'S' is the group weight as seen by its parent.
4854 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4855 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4856 * 4/7) times the weight of the group.
4858 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4860 struct sched_entity
*se
= tg
->se
[cpu
];
4862 if (!tg
->parent
) /* the trivial, non-cgroup case */
4865 for_each_sched_entity(se
) {
4871 * W = @wg + \Sum rw_j
4873 W
= wg
+ calc_tg_weight(tg
, se
->my_q
);
4878 w
= cfs_rq_load_avg(se
->my_q
) + wl
;
4881 * wl = S * s'_i; see (2)
4884 wl
= (w
* (long)tg
->shares
) / W
;
4889 * Per the above, wl is the new se->load.weight value; since
4890 * those are clipped to [MIN_SHARES, ...) do so now. See
4891 * calc_cfs_shares().
4893 if (wl
< MIN_SHARES
)
4897 * wl = dw_i = S * (s'_i - s_i); see (3)
4899 wl
-= se
->avg
.load_avg
;
4902 * Recursively apply this logic to all parent groups to compute
4903 * the final effective load change on the root group. Since
4904 * only the @tg group gets extra weight, all parent groups can
4905 * only redistribute existing shares. @wl is the shift in shares
4906 * resulting from this level per the above.
4915 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4923 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
4924 * A waker of many should wake a different task than the one last awakened
4925 * at a frequency roughly N times higher than one of its wakees. In order
4926 * to determine whether we should let the load spread vs consolodating to
4927 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
4928 * partner, and a factor of lls_size higher frequency in the other. With
4929 * both conditions met, we can be relatively sure that the relationship is
4930 * non-monogamous, with partner count exceeding socket size. Waker/wakee
4931 * being client/server, worker/dispatcher, interrupt source or whatever is
4932 * irrelevant, spread criteria is apparent partner count exceeds socket size.
4934 static int wake_wide(struct task_struct
*p
)
4936 unsigned int master
= current
->wakee_flips
;
4937 unsigned int slave
= p
->wakee_flips
;
4938 int factor
= this_cpu_read(sd_llc_size
);
4941 swap(master
, slave
);
4942 if (slave
< factor
|| master
< slave
* factor
)
4947 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
4949 s64 this_load
, load
;
4950 s64 this_eff_load
, prev_eff_load
;
4951 int idx
, this_cpu
, prev_cpu
;
4952 struct task_group
*tg
;
4953 unsigned long weight
;
4957 this_cpu
= smp_processor_id();
4958 prev_cpu
= task_cpu(p
);
4959 load
= source_load(prev_cpu
, idx
);
4960 this_load
= target_load(this_cpu
, idx
);
4963 * If sync wakeup then subtract the (maximum possible)
4964 * effect of the currently running task from the load
4965 * of the current CPU:
4968 tg
= task_group(current
);
4969 weight
= current
->se
.avg
.load_avg
;
4971 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
4972 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
4976 weight
= p
->se
.avg
.load_avg
;
4979 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4980 * due to the sync cause above having dropped this_load to 0, we'll
4981 * always have an imbalance, but there's really nothing you can do
4982 * about that, so that's good too.
4984 * Otherwise check if either cpus are near enough in load to allow this
4985 * task to be woken on this_cpu.
4987 this_eff_load
= 100;
4988 this_eff_load
*= capacity_of(prev_cpu
);
4990 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
4991 prev_eff_load
*= capacity_of(this_cpu
);
4993 if (this_load
> 0) {
4994 this_eff_load
*= this_load
+
4995 effective_load(tg
, this_cpu
, weight
, weight
);
4997 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
5000 balanced
= this_eff_load
<= prev_eff_load
;
5002 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
5007 schedstat_inc(sd
, ttwu_move_affine
);
5008 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
5014 * find_idlest_group finds and returns the least busy CPU group within the
5017 static struct sched_group
*
5018 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
5019 int this_cpu
, int sd_flag
)
5021 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
5022 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
5023 int load_idx
= sd
->forkexec_idx
;
5024 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
5026 if (sd_flag
& SD_BALANCE_WAKE
)
5027 load_idx
= sd
->wake_idx
;
5030 unsigned long load
, avg_load
;
5034 /* Skip over this group if it has no CPUs allowed */
5035 if (!cpumask_intersects(sched_group_cpus(group
),
5036 tsk_cpus_allowed(p
)))
5039 local_group
= cpumask_test_cpu(this_cpu
,
5040 sched_group_cpus(group
));
5042 /* Tally up the load of all CPUs in the group */
5045 for_each_cpu(i
, sched_group_cpus(group
)) {
5046 /* Bias balancing toward cpus of our domain */
5048 load
= source_load(i
, load_idx
);
5050 load
= target_load(i
, load_idx
);
5055 /* Adjust by relative CPU capacity of the group */
5056 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) / group
->sgc
->capacity
;
5059 this_load
= avg_load
;
5060 } else if (avg_load
< min_load
) {
5061 min_load
= avg_load
;
5064 } while (group
= group
->next
, group
!= sd
->groups
);
5066 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
5072 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5075 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5077 unsigned long load
, min_load
= ULONG_MAX
;
5078 unsigned int min_exit_latency
= UINT_MAX
;
5079 u64 latest_idle_timestamp
= 0;
5080 int least_loaded_cpu
= this_cpu
;
5081 int shallowest_idle_cpu
= -1;
5084 /* Traverse only the allowed CPUs */
5085 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
5087 struct rq
*rq
= cpu_rq(i
);
5088 struct cpuidle_state
*idle
= idle_get_state(rq
);
5089 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5091 * We give priority to a CPU whose idle state
5092 * has the smallest exit latency irrespective
5093 * of any idle timestamp.
5095 min_exit_latency
= idle
->exit_latency
;
5096 latest_idle_timestamp
= rq
->idle_stamp
;
5097 shallowest_idle_cpu
= i
;
5098 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5099 rq
->idle_stamp
> latest_idle_timestamp
) {
5101 * If equal or no active idle state, then
5102 * the most recently idled CPU might have
5105 latest_idle_timestamp
= rq
->idle_stamp
;
5106 shallowest_idle_cpu
= i
;
5108 } else if (shallowest_idle_cpu
== -1) {
5109 load
= weighted_cpuload(i
);
5110 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
5112 least_loaded_cpu
= i
;
5117 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5121 * Try and locate an idle CPU in the sched_domain.
5123 static int select_idle_sibling(struct task_struct
*p
, int target
)
5125 struct sched_domain
*sd
;
5126 struct sched_group
*sg
;
5127 int i
= task_cpu(p
);
5129 if (idle_cpu(target
))
5133 * If the prevous cpu is cache affine and idle, don't be stupid.
5135 if (i
!= target
&& cpus_share_cache(i
, target
) && idle_cpu(i
))
5139 * Otherwise, iterate the domains and find an eligible idle cpu.
5141 * A completely idle sched group at higher domains is more
5142 * desirable than an idle group at a lower level, because lower
5143 * domains have smaller groups and usually share hardware
5144 * resources which causes tasks to contend on them, e.g. x86
5145 * hyperthread siblings in the lowest domain (SMT) can contend
5146 * on the shared cpu pipeline.
5148 * However, while we prefer idle groups at higher domains
5149 * finding an idle cpu at the lowest domain is still better than
5150 * returning 'target', which we've already established, isn't
5153 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
5154 for_each_lower_domain(sd
) {
5157 if (!cpumask_intersects(sched_group_cpus(sg
),
5158 tsk_cpus_allowed(p
)))
5161 /* Ensure the entire group is idle */
5162 for_each_cpu(i
, sched_group_cpus(sg
)) {
5163 if (i
== target
|| !idle_cpu(i
))
5168 * It doesn't matter which cpu we pick, the
5169 * whole group is idle.
5171 target
= cpumask_first_and(sched_group_cpus(sg
),
5172 tsk_cpus_allowed(p
));
5176 } while (sg
!= sd
->groups
);
5183 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5184 * tasks. The unit of the return value must be the one of capacity so we can
5185 * compare the utilization with the capacity of the CPU that is available for
5186 * CFS task (ie cpu_capacity).
5188 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5189 * recent utilization of currently non-runnable tasks on a CPU. It represents
5190 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5191 * capacity_orig is the cpu_capacity available at the highest frequency
5192 * (arch_scale_freq_capacity()).
5193 * The utilization of a CPU converges towards a sum equal to or less than the
5194 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5195 * the running time on this CPU scaled by capacity_curr.
5197 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5198 * higher than capacity_orig because of unfortunate rounding in
5199 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5200 * the average stabilizes with the new running time. We need to check that the
5201 * utilization stays within the range of [0..capacity_orig] and cap it if
5202 * necessary. Without utilization capping, a group could be seen as overloaded
5203 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5204 * available capacity. We allow utilization to overshoot capacity_curr (but not
5205 * capacity_orig) as it useful for predicting the capacity required after task
5206 * migrations (scheduler-driven DVFS).
5208 static int cpu_util(int cpu
)
5210 unsigned long util
= cpu_rq(cpu
)->cfs
.avg
.util_avg
;
5211 unsigned long capacity
= capacity_orig_of(cpu
);
5213 return (util
>= capacity
) ? capacity
: util
;
5217 * select_task_rq_fair: Select target runqueue for the waking task in domains
5218 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5219 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5221 * Balances load by selecting the idlest cpu in the idlest group, or under
5222 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5224 * Returns the target cpu number.
5226 * preempt must be disabled.
5229 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
5231 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
5232 int cpu
= smp_processor_id();
5233 int new_cpu
= prev_cpu
;
5234 int want_affine
= 0;
5235 int sync
= wake_flags
& WF_SYNC
;
5237 if (sd_flag
& SD_BALANCE_WAKE
)
5238 want_affine
= !wake_wide(p
) && cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
));
5241 for_each_domain(cpu
, tmp
) {
5242 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
5246 * If both cpu and prev_cpu are part of this domain,
5247 * cpu is a valid SD_WAKE_AFFINE target.
5249 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
5250 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
5255 if (tmp
->flags
& sd_flag
)
5257 else if (!want_affine
)
5262 sd
= NULL
; /* Prefer wake_affine over balance flags */
5263 if (cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, sync
))
5268 if (sd_flag
& SD_BALANCE_WAKE
) /* XXX always ? */
5269 new_cpu
= select_idle_sibling(p
, new_cpu
);
5272 struct sched_group
*group
;
5275 if (!(sd
->flags
& sd_flag
)) {
5280 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
5286 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
5287 if (new_cpu
== -1 || new_cpu
== cpu
) {
5288 /* Now try balancing at a lower domain level of cpu */
5293 /* Now try balancing at a lower domain level of new_cpu */
5295 weight
= sd
->span_weight
;
5297 for_each_domain(cpu
, tmp
) {
5298 if (weight
<= tmp
->span_weight
)
5300 if (tmp
->flags
& sd_flag
)
5303 /* while loop will break here if sd == NULL */
5311 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5312 * cfs_rq_of(p) references at time of call are still valid and identify the
5313 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5315 static void migrate_task_rq_fair(struct task_struct
*p
)
5318 * We are supposed to update the task to "current" time, then its up to date
5319 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5320 * what current time is, so simply throw away the out-of-date time. This
5321 * will result in the wakee task is less decayed, but giving the wakee more
5322 * load sounds not bad.
5324 remove_entity_load_avg(&p
->se
);
5326 /* Tell new CPU we are migrated */
5327 p
->se
.avg
.last_update_time
= 0;
5329 /* We have migrated, no longer consider this task hot */
5330 p
->se
.exec_start
= 0;
5333 static void task_dead_fair(struct task_struct
*p
)
5335 remove_entity_load_avg(&p
->se
);
5337 #endif /* CONFIG_SMP */
5339 static unsigned long
5340 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
5342 unsigned long gran
= sysctl_sched_wakeup_granularity
;
5345 * Since its curr running now, convert the gran from real-time
5346 * to virtual-time in his units.
5348 * By using 'se' instead of 'curr' we penalize light tasks, so
5349 * they get preempted easier. That is, if 'se' < 'curr' then
5350 * the resulting gran will be larger, therefore penalizing the
5351 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5352 * be smaller, again penalizing the lighter task.
5354 * This is especially important for buddies when the leftmost
5355 * task is higher priority than the buddy.
5357 return calc_delta_fair(gran
, se
);
5361 * Should 'se' preempt 'curr'.
5375 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
5377 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
5382 gran
= wakeup_gran(curr
, se
);
5389 static void set_last_buddy(struct sched_entity
*se
)
5391 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5394 for_each_sched_entity(se
)
5395 cfs_rq_of(se
)->last
= se
;
5398 static void set_next_buddy(struct sched_entity
*se
)
5400 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5403 for_each_sched_entity(se
)
5404 cfs_rq_of(se
)->next
= se
;
5407 static void set_skip_buddy(struct sched_entity
*se
)
5409 for_each_sched_entity(se
)
5410 cfs_rq_of(se
)->skip
= se
;
5414 * Preempt the current task with a newly woken task if needed:
5416 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
5418 struct task_struct
*curr
= rq
->curr
;
5419 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
5420 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5421 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
5422 int next_buddy_marked
= 0;
5424 if (unlikely(se
== pse
))
5428 * This is possible from callers such as attach_tasks(), in which we
5429 * unconditionally check_prempt_curr() after an enqueue (which may have
5430 * lead to a throttle). This both saves work and prevents false
5431 * next-buddy nomination below.
5433 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
5436 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
5437 set_next_buddy(pse
);
5438 next_buddy_marked
= 1;
5442 * We can come here with TIF_NEED_RESCHED already set from new task
5445 * Note: this also catches the edge-case of curr being in a throttled
5446 * group (e.g. via set_curr_task), since update_curr() (in the
5447 * enqueue of curr) will have resulted in resched being set. This
5448 * prevents us from potentially nominating it as a false LAST_BUDDY
5451 if (test_tsk_need_resched(curr
))
5454 /* Idle tasks are by definition preempted by non-idle tasks. */
5455 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
5456 likely(p
->policy
!= SCHED_IDLE
))
5460 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5461 * is driven by the tick):
5463 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
5466 find_matching_se(&se
, &pse
);
5467 update_curr(cfs_rq_of(se
));
5469 if (wakeup_preempt_entity(se
, pse
) == 1) {
5471 * Bias pick_next to pick the sched entity that is
5472 * triggering this preemption.
5474 if (!next_buddy_marked
)
5475 set_next_buddy(pse
);
5484 * Only set the backward buddy when the current task is still
5485 * on the rq. This can happen when a wakeup gets interleaved
5486 * with schedule on the ->pre_schedule() or idle_balance()
5487 * point, either of which can * drop the rq lock.
5489 * Also, during early boot the idle thread is in the fair class,
5490 * for obvious reasons its a bad idea to schedule back to it.
5492 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
5495 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
5499 static struct task_struct
*
5500 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5502 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
5503 struct sched_entity
*se
;
5504 struct task_struct
*p
;
5508 #ifdef CONFIG_FAIR_GROUP_SCHED
5509 if (!cfs_rq
->nr_running
)
5512 if (prev
->sched_class
!= &fair_sched_class
)
5516 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5517 * likely that a next task is from the same cgroup as the current.
5519 * Therefore attempt to avoid putting and setting the entire cgroup
5520 * hierarchy, only change the part that actually changes.
5524 struct sched_entity
*curr
= cfs_rq
->curr
;
5527 * Since we got here without doing put_prev_entity() we also
5528 * have to consider cfs_rq->curr. If it is still a runnable
5529 * entity, update_curr() will update its vruntime, otherwise
5530 * forget we've ever seen it.
5534 update_curr(cfs_rq
);
5539 * This call to check_cfs_rq_runtime() will do the
5540 * throttle and dequeue its entity in the parent(s).
5541 * Therefore the 'simple' nr_running test will indeed
5544 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
5548 se
= pick_next_entity(cfs_rq
, curr
);
5549 cfs_rq
= group_cfs_rq(se
);
5555 * Since we haven't yet done put_prev_entity and if the selected task
5556 * is a different task than we started out with, try and touch the
5557 * least amount of cfs_rqs.
5560 struct sched_entity
*pse
= &prev
->se
;
5562 while (!(cfs_rq
= is_same_group(se
, pse
))) {
5563 int se_depth
= se
->depth
;
5564 int pse_depth
= pse
->depth
;
5566 if (se_depth
<= pse_depth
) {
5567 put_prev_entity(cfs_rq_of(pse
), pse
);
5568 pse
= parent_entity(pse
);
5570 if (se_depth
>= pse_depth
) {
5571 set_next_entity(cfs_rq_of(se
), se
);
5572 se
= parent_entity(se
);
5576 put_prev_entity(cfs_rq
, pse
);
5577 set_next_entity(cfs_rq
, se
);
5580 if (hrtick_enabled(rq
))
5581 hrtick_start_fair(rq
, p
);
5588 if (!cfs_rq
->nr_running
)
5591 put_prev_task(rq
, prev
);
5594 se
= pick_next_entity(cfs_rq
, NULL
);
5595 set_next_entity(cfs_rq
, se
);
5596 cfs_rq
= group_cfs_rq(se
);
5601 if (hrtick_enabled(rq
))
5602 hrtick_start_fair(rq
, p
);
5608 * This is OK, because current is on_cpu, which avoids it being picked
5609 * for load-balance and preemption/IRQs are still disabled avoiding
5610 * further scheduler activity on it and we're being very careful to
5611 * re-start the picking loop.
5613 lockdep_unpin_lock(&rq
->lock
);
5614 new_tasks
= idle_balance(rq
);
5615 lockdep_pin_lock(&rq
->lock
);
5617 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5618 * possible for any higher priority task to appear. In that case we
5619 * must re-start the pick_next_entity() loop.
5631 * Account for a descheduled task:
5633 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5635 struct sched_entity
*se
= &prev
->se
;
5636 struct cfs_rq
*cfs_rq
;
5638 for_each_sched_entity(se
) {
5639 cfs_rq
= cfs_rq_of(se
);
5640 put_prev_entity(cfs_rq
, se
);
5645 * sched_yield() is very simple
5647 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5649 static void yield_task_fair(struct rq
*rq
)
5651 struct task_struct
*curr
= rq
->curr
;
5652 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5653 struct sched_entity
*se
= &curr
->se
;
5656 * Are we the only task in the tree?
5658 if (unlikely(rq
->nr_running
== 1))
5661 clear_buddies(cfs_rq
, se
);
5663 if (curr
->policy
!= SCHED_BATCH
) {
5664 update_rq_clock(rq
);
5666 * Update run-time statistics of the 'current'.
5668 update_curr(cfs_rq
);
5670 * Tell update_rq_clock() that we've just updated,
5671 * so we don't do microscopic update in schedule()
5672 * and double the fastpath cost.
5674 rq_clock_skip_update(rq
, true);
5680 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
5682 struct sched_entity
*se
= &p
->se
;
5684 /* throttled hierarchies are not runnable */
5685 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
5688 /* Tell the scheduler that we'd really like pse to run next. */
5691 yield_task_fair(rq
);
5697 /**************************************************
5698 * Fair scheduling class load-balancing methods.
5702 * The purpose of load-balancing is to achieve the same basic fairness the
5703 * per-cpu scheduler provides, namely provide a proportional amount of compute
5704 * time to each task. This is expressed in the following equation:
5706 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5708 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5709 * W_i,0 is defined as:
5711 * W_i,0 = \Sum_j w_i,j (2)
5713 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5714 * is derived from the nice value as per sched_prio_to_weight[].
5716 * The weight average is an exponential decay average of the instantaneous
5719 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5721 * C_i is the compute capacity of cpu i, typically it is the
5722 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5723 * can also include other factors [XXX].
5725 * To achieve this balance we define a measure of imbalance which follows
5726 * directly from (1):
5728 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5730 * We them move tasks around to minimize the imbalance. In the continuous
5731 * function space it is obvious this converges, in the discrete case we get
5732 * a few fun cases generally called infeasible weight scenarios.
5735 * - infeasible weights;
5736 * - local vs global optima in the discrete case. ]
5741 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5742 * for all i,j solution, we create a tree of cpus that follows the hardware
5743 * topology where each level pairs two lower groups (or better). This results
5744 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5745 * tree to only the first of the previous level and we decrease the frequency
5746 * of load-balance at each level inv. proportional to the number of cpus in
5752 * \Sum { --- * --- * 2^i } = O(n) (5)
5754 * `- size of each group
5755 * | | `- number of cpus doing load-balance
5757 * `- sum over all levels
5759 * Coupled with a limit on how many tasks we can migrate every balance pass,
5760 * this makes (5) the runtime complexity of the balancer.
5762 * An important property here is that each CPU is still (indirectly) connected
5763 * to every other cpu in at most O(log n) steps:
5765 * The adjacency matrix of the resulting graph is given by:
5768 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5771 * And you'll find that:
5773 * A^(log_2 n)_i,j != 0 for all i,j (7)
5775 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5776 * The task movement gives a factor of O(m), giving a convergence complexity
5779 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5784 * In order to avoid CPUs going idle while there's still work to do, new idle
5785 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5786 * tree itself instead of relying on other CPUs to bring it work.
5788 * This adds some complexity to both (5) and (8) but it reduces the total idle
5796 * Cgroups make a horror show out of (2), instead of a simple sum we get:
5799 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
5804 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
5806 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
5808 * The big problem is S_k, its a global sum needed to compute a local (W_i)
5811 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
5812 * rewrite all of this once again.]
5815 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
5817 enum fbq_type
{ regular
, remote
, all
};
5819 #define LBF_ALL_PINNED 0x01
5820 #define LBF_NEED_BREAK 0x02
5821 #define LBF_DST_PINNED 0x04
5822 #define LBF_SOME_PINNED 0x08
5825 struct sched_domain
*sd
;
5833 struct cpumask
*dst_grpmask
;
5835 enum cpu_idle_type idle
;
5837 /* The set of CPUs under consideration for load-balancing */
5838 struct cpumask
*cpus
;
5843 unsigned int loop_break
;
5844 unsigned int loop_max
;
5846 enum fbq_type fbq_type
;
5847 struct list_head tasks
;
5851 * Is this task likely cache-hot:
5853 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
5857 lockdep_assert_held(&env
->src_rq
->lock
);
5859 if (p
->sched_class
!= &fair_sched_class
)
5862 if (unlikely(p
->policy
== SCHED_IDLE
))
5866 * Buddy candidates are cache hot:
5868 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
5869 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
5870 &p
->se
== cfs_rq_of(&p
->se
)->last
))
5873 if (sysctl_sched_migration_cost
== -1)
5875 if (sysctl_sched_migration_cost
== 0)
5878 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
5880 return delta
< (s64
)sysctl_sched_migration_cost
;
5883 #ifdef CONFIG_NUMA_BALANCING
5885 * Returns 1, if task migration degrades locality
5886 * Returns 0, if task migration improves locality i.e migration preferred.
5887 * Returns -1, if task migration is not affected by locality.
5889 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
5891 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
5892 unsigned long src_faults
, dst_faults
;
5893 int src_nid
, dst_nid
;
5895 if (!static_branch_likely(&sched_numa_balancing
))
5898 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
5901 src_nid
= cpu_to_node(env
->src_cpu
);
5902 dst_nid
= cpu_to_node(env
->dst_cpu
);
5904 if (src_nid
== dst_nid
)
5907 /* Migrating away from the preferred node is always bad. */
5908 if (src_nid
== p
->numa_preferred_nid
) {
5909 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
5915 /* Encourage migration to the preferred node. */
5916 if (dst_nid
== p
->numa_preferred_nid
)
5920 src_faults
= group_faults(p
, src_nid
);
5921 dst_faults
= group_faults(p
, dst_nid
);
5923 src_faults
= task_faults(p
, src_nid
);
5924 dst_faults
= task_faults(p
, dst_nid
);
5927 return dst_faults
< src_faults
;
5931 static inline int migrate_degrades_locality(struct task_struct
*p
,
5939 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
5942 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
5946 lockdep_assert_held(&env
->src_rq
->lock
);
5949 * We do not migrate tasks that are:
5950 * 1) throttled_lb_pair, or
5951 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5952 * 3) running (obviously), or
5953 * 4) are cache-hot on their current CPU.
5955 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
5958 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
5961 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
5963 env
->flags
|= LBF_SOME_PINNED
;
5966 * Remember if this task can be migrated to any other cpu in
5967 * our sched_group. We may want to revisit it if we couldn't
5968 * meet load balance goals by pulling other tasks on src_cpu.
5970 * Also avoid computing new_dst_cpu if we have already computed
5971 * one in current iteration.
5973 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
5976 /* Prevent to re-select dst_cpu via env's cpus */
5977 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
5978 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
5979 env
->flags
|= LBF_DST_PINNED
;
5980 env
->new_dst_cpu
= cpu
;
5988 /* Record that we found atleast one task that could run on dst_cpu */
5989 env
->flags
&= ~LBF_ALL_PINNED
;
5991 if (task_running(env
->src_rq
, p
)) {
5992 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
5997 * Aggressive migration if:
5998 * 1) destination numa is preferred
5999 * 2) task is cache cold, or
6000 * 3) too many balance attempts have failed.
6002 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
6003 if (tsk_cache_hot
== -1)
6004 tsk_cache_hot
= task_hot(p
, env
);
6006 if (tsk_cache_hot
<= 0 ||
6007 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
6008 if (tsk_cache_hot
== 1) {
6009 schedstat_inc(env
->sd
, lb_hot_gained
[env
->idle
]);
6010 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
6015 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
6020 * detach_task() -- detach the task for the migration specified in env
6022 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
6024 lockdep_assert_held(&env
->src_rq
->lock
);
6026 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
6027 deactivate_task(env
->src_rq
, p
, 0);
6028 set_task_cpu(p
, env
->dst_cpu
);
6032 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6033 * part of active balancing operations within "domain".
6035 * Returns a task if successful and NULL otherwise.
6037 static struct task_struct
*detach_one_task(struct lb_env
*env
)
6039 struct task_struct
*p
, *n
;
6041 lockdep_assert_held(&env
->src_rq
->lock
);
6043 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
6044 if (!can_migrate_task(p
, env
))
6047 detach_task(p
, env
);
6050 * Right now, this is only the second place where
6051 * lb_gained[env->idle] is updated (other is detach_tasks)
6052 * so we can safely collect stats here rather than
6053 * inside detach_tasks().
6055 schedstat_inc(env
->sd
, lb_gained
[env
->idle
]);
6061 static const unsigned int sched_nr_migrate_break
= 32;
6064 * detach_tasks() -- tries to detach up to imbalance weighted load from
6065 * busiest_rq, as part of a balancing operation within domain "sd".
6067 * Returns number of detached tasks if successful and 0 otherwise.
6069 static int detach_tasks(struct lb_env
*env
)
6071 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
6072 struct task_struct
*p
;
6076 lockdep_assert_held(&env
->src_rq
->lock
);
6078 if (env
->imbalance
<= 0)
6081 while (!list_empty(tasks
)) {
6083 * We don't want to steal all, otherwise we may be treated likewise,
6084 * which could at worst lead to a livelock crash.
6086 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
6089 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6092 /* We've more or less seen every task there is, call it quits */
6093 if (env
->loop
> env
->loop_max
)
6096 /* take a breather every nr_migrate tasks */
6097 if (env
->loop
> env
->loop_break
) {
6098 env
->loop_break
+= sched_nr_migrate_break
;
6099 env
->flags
|= LBF_NEED_BREAK
;
6103 if (!can_migrate_task(p
, env
))
6106 load
= task_h_load(p
);
6108 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
6111 if ((load
/ 2) > env
->imbalance
)
6114 detach_task(p
, env
);
6115 list_add(&p
->se
.group_node
, &env
->tasks
);
6118 env
->imbalance
-= load
;
6120 #ifdef CONFIG_PREEMPT
6122 * NEWIDLE balancing is a source of latency, so preemptible
6123 * kernels will stop after the first task is detached to minimize
6124 * the critical section.
6126 if (env
->idle
== CPU_NEWLY_IDLE
)
6131 * We only want to steal up to the prescribed amount of
6134 if (env
->imbalance
<= 0)
6139 list_move_tail(&p
->se
.group_node
, tasks
);
6143 * Right now, this is one of only two places we collect this stat
6144 * so we can safely collect detach_one_task() stats here rather
6145 * than inside detach_one_task().
6147 schedstat_add(env
->sd
, lb_gained
[env
->idle
], detached
);
6153 * attach_task() -- attach the task detached by detach_task() to its new rq.
6155 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
6157 lockdep_assert_held(&rq
->lock
);
6159 BUG_ON(task_rq(p
) != rq
);
6160 activate_task(rq
, p
, 0);
6161 p
->on_rq
= TASK_ON_RQ_QUEUED
;
6162 check_preempt_curr(rq
, p
, 0);
6166 * attach_one_task() -- attaches the task returned from detach_one_task() to
6169 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
6171 raw_spin_lock(&rq
->lock
);
6173 raw_spin_unlock(&rq
->lock
);
6177 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6180 static void attach_tasks(struct lb_env
*env
)
6182 struct list_head
*tasks
= &env
->tasks
;
6183 struct task_struct
*p
;
6185 raw_spin_lock(&env
->dst_rq
->lock
);
6187 while (!list_empty(tasks
)) {
6188 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6189 list_del_init(&p
->se
.group_node
);
6191 attach_task(env
->dst_rq
, p
);
6194 raw_spin_unlock(&env
->dst_rq
->lock
);
6197 #ifdef CONFIG_FAIR_GROUP_SCHED
6198 static void update_blocked_averages(int cpu
)
6200 struct rq
*rq
= cpu_rq(cpu
);
6201 struct cfs_rq
*cfs_rq
;
6202 unsigned long flags
;
6204 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6205 update_rq_clock(rq
);
6208 * Iterates the task_group tree in a bottom up fashion, see
6209 * list_add_leaf_cfs_rq() for details.
6211 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
6212 /* throttled entities do not contribute to load */
6213 if (throttled_hierarchy(cfs_rq
))
6216 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
))
6217 update_tg_load_avg(cfs_rq
, 0);
6219 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6223 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6224 * This needs to be done in a top-down fashion because the load of a child
6225 * group is a fraction of its parents load.
6227 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
6229 struct rq
*rq
= rq_of(cfs_rq
);
6230 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
6231 unsigned long now
= jiffies
;
6234 if (cfs_rq
->last_h_load_update
== now
)
6237 cfs_rq
->h_load_next
= NULL
;
6238 for_each_sched_entity(se
) {
6239 cfs_rq
= cfs_rq_of(se
);
6240 cfs_rq
->h_load_next
= se
;
6241 if (cfs_rq
->last_h_load_update
== now
)
6246 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
6247 cfs_rq
->last_h_load_update
= now
;
6250 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
6251 load
= cfs_rq
->h_load
;
6252 load
= div64_ul(load
* se
->avg
.load_avg
,
6253 cfs_rq_load_avg(cfs_rq
) + 1);
6254 cfs_rq
= group_cfs_rq(se
);
6255 cfs_rq
->h_load
= load
;
6256 cfs_rq
->last_h_load_update
= now
;
6260 static unsigned long task_h_load(struct task_struct
*p
)
6262 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
6264 update_cfs_rq_h_load(cfs_rq
);
6265 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
6266 cfs_rq_load_avg(cfs_rq
) + 1);
6269 static inline void update_blocked_averages(int cpu
)
6271 struct rq
*rq
= cpu_rq(cpu
);
6272 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
6273 unsigned long flags
;
6275 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6276 update_rq_clock(rq
);
6277 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
);
6278 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6281 static unsigned long task_h_load(struct task_struct
*p
)
6283 return p
->se
.avg
.load_avg
;
6287 /********** Helpers for find_busiest_group ************************/
6296 * sg_lb_stats - stats of a sched_group required for load_balancing
6298 struct sg_lb_stats
{
6299 unsigned long avg_load
; /*Avg load across the CPUs of the group */
6300 unsigned long group_load
; /* Total load over the CPUs of the group */
6301 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
6302 unsigned long load_per_task
;
6303 unsigned long group_capacity
;
6304 unsigned long group_util
; /* Total utilization of the group */
6305 unsigned int sum_nr_running
; /* Nr tasks running in the group */
6306 unsigned int idle_cpus
;
6307 unsigned int group_weight
;
6308 enum group_type group_type
;
6309 int group_no_capacity
;
6310 #ifdef CONFIG_NUMA_BALANCING
6311 unsigned int nr_numa_running
;
6312 unsigned int nr_preferred_running
;
6317 * sd_lb_stats - Structure to store the statistics of a sched_domain
6318 * during load balancing.
6320 struct sd_lb_stats
{
6321 struct sched_group
*busiest
; /* Busiest group in this sd */
6322 struct sched_group
*local
; /* Local group in this sd */
6323 unsigned long total_load
; /* Total load of all groups in sd */
6324 unsigned long total_capacity
; /* Total capacity of all groups in sd */
6325 unsigned long avg_load
; /* Average load across all groups in sd */
6327 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
6328 struct sg_lb_stats local_stat
; /* Statistics of the local group */
6331 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
6334 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6335 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6336 * We must however clear busiest_stat::avg_load because
6337 * update_sd_pick_busiest() reads this before assignment.
6339 *sds
= (struct sd_lb_stats
){
6343 .total_capacity
= 0UL,
6346 .sum_nr_running
= 0,
6347 .group_type
= group_other
,
6353 * get_sd_load_idx - Obtain the load index for a given sched domain.
6354 * @sd: The sched_domain whose load_idx is to be obtained.
6355 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6357 * Return: The load index.
6359 static inline int get_sd_load_idx(struct sched_domain
*sd
,
6360 enum cpu_idle_type idle
)
6366 load_idx
= sd
->busy_idx
;
6369 case CPU_NEWLY_IDLE
:
6370 load_idx
= sd
->newidle_idx
;
6373 load_idx
= sd
->idle_idx
;
6380 static unsigned long scale_rt_capacity(int cpu
)
6382 struct rq
*rq
= cpu_rq(cpu
);
6383 u64 total
, used
, age_stamp
, avg
;
6387 * Since we're reading these variables without serialization make sure
6388 * we read them once before doing sanity checks on them.
6390 age_stamp
= READ_ONCE(rq
->age_stamp
);
6391 avg
= READ_ONCE(rq
->rt_avg
);
6392 delta
= __rq_clock_broken(rq
) - age_stamp
;
6394 if (unlikely(delta
< 0))
6397 total
= sched_avg_period() + delta
;
6399 used
= div_u64(avg
, total
);
6401 if (likely(used
< SCHED_CAPACITY_SCALE
))
6402 return SCHED_CAPACITY_SCALE
- used
;
6407 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
6409 unsigned long capacity
= arch_scale_cpu_capacity(sd
, cpu
);
6410 struct sched_group
*sdg
= sd
->groups
;
6412 cpu_rq(cpu
)->cpu_capacity_orig
= capacity
;
6414 capacity
*= scale_rt_capacity(cpu
);
6415 capacity
>>= SCHED_CAPACITY_SHIFT
;
6420 cpu_rq(cpu
)->cpu_capacity
= capacity
;
6421 sdg
->sgc
->capacity
= capacity
;
6424 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
6426 struct sched_domain
*child
= sd
->child
;
6427 struct sched_group
*group
, *sdg
= sd
->groups
;
6428 unsigned long capacity
;
6429 unsigned long interval
;
6431 interval
= msecs_to_jiffies(sd
->balance_interval
);
6432 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
6433 sdg
->sgc
->next_update
= jiffies
+ interval
;
6436 update_cpu_capacity(sd
, cpu
);
6442 if (child
->flags
& SD_OVERLAP
) {
6444 * SD_OVERLAP domains cannot assume that child groups
6445 * span the current group.
6448 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
6449 struct sched_group_capacity
*sgc
;
6450 struct rq
*rq
= cpu_rq(cpu
);
6453 * build_sched_domains() -> init_sched_groups_capacity()
6454 * gets here before we've attached the domains to the
6457 * Use capacity_of(), which is set irrespective of domains
6458 * in update_cpu_capacity().
6460 * This avoids capacity from being 0 and
6461 * causing divide-by-zero issues on boot.
6463 if (unlikely(!rq
->sd
)) {
6464 capacity
+= capacity_of(cpu
);
6468 sgc
= rq
->sd
->groups
->sgc
;
6469 capacity
+= sgc
->capacity
;
6473 * !SD_OVERLAP domains can assume that child groups
6474 * span the current group.
6477 group
= child
->groups
;
6479 capacity
+= group
->sgc
->capacity
;
6480 group
= group
->next
;
6481 } while (group
!= child
->groups
);
6484 sdg
->sgc
->capacity
= capacity
;
6488 * Check whether the capacity of the rq has been noticeably reduced by side
6489 * activity. The imbalance_pct is used for the threshold.
6490 * Return true is the capacity is reduced
6493 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
6495 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
6496 (rq
->cpu_capacity_orig
* 100));
6500 * Group imbalance indicates (and tries to solve) the problem where balancing
6501 * groups is inadequate due to tsk_cpus_allowed() constraints.
6503 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6504 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6507 * { 0 1 2 3 } { 4 5 6 7 }
6510 * If we were to balance group-wise we'd place two tasks in the first group and
6511 * two tasks in the second group. Clearly this is undesired as it will overload
6512 * cpu 3 and leave one of the cpus in the second group unused.
6514 * The current solution to this issue is detecting the skew in the first group
6515 * by noticing the lower domain failed to reach balance and had difficulty
6516 * moving tasks due to affinity constraints.
6518 * When this is so detected; this group becomes a candidate for busiest; see
6519 * update_sd_pick_busiest(). And calculate_imbalance() and
6520 * find_busiest_group() avoid some of the usual balance conditions to allow it
6521 * to create an effective group imbalance.
6523 * This is a somewhat tricky proposition since the next run might not find the
6524 * group imbalance and decide the groups need to be balanced again. A most
6525 * subtle and fragile situation.
6528 static inline int sg_imbalanced(struct sched_group
*group
)
6530 return group
->sgc
->imbalance
;
6534 * group_has_capacity returns true if the group has spare capacity that could
6535 * be used by some tasks.
6536 * We consider that a group has spare capacity if the * number of task is
6537 * smaller than the number of CPUs or if the utilization is lower than the
6538 * available capacity for CFS tasks.
6539 * For the latter, we use a threshold to stabilize the state, to take into
6540 * account the variance of the tasks' load and to return true if the available
6541 * capacity in meaningful for the load balancer.
6542 * As an example, an available capacity of 1% can appear but it doesn't make
6543 * any benefit for the load balance.
6546 group_has_capacity(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6548 if (sgs
->sum_nr_running
< sgs
->group_weight
)
6551 if ((sgs
->group_capacity
* 100) >
6552 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6559 * group_is_overloaded returns true if the group has more tasks than it can
6561 * group_is_overloaded is not equals to !group_has_capacity because a group
6562 * with the exact right number of tasks, has no more spare capacity but is not
6563 * overloaded so both group_has_capacity and group_is_overloaded return
6567 group_is_overloaded(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6569 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
6572 if ((sgs
->group_capacity
* 100) <
6573 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6580 group_type
group_classify(struct sched_group
*group
,
6581 struct sg_lb_stats
*sgs
)
6583 if (sgs
->group_no_capacity
)
6584 return group_overloaded
;
6586 if (sg_imbalanced(group
))
6587 return group_imbalanced
;
6593 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6594 * @env: The load balancing environment.
6595 * @group: sched_group whose statistics are to be updated.
6596 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6597 * @local_group: Does group contain this_cpu.
6598 * @sgs: variable to hold the statistics for this group.
6599 * @overload: Indicate more than one runnable task for any CPU.
6601 static inline void update_sg_lb_stats(struct lb_env
*env
,
6602 struct sched_group
*group
, int load_idx
,
6603 int local_group
, struct sg_lb_stats
*sgs
,
6609 memset(sgs
, 0, sizeof(*sgs
));
6611 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6612 struct rq
*rq
= cpu_rq(i
);
6614 /* Bias balancing toward cpus of our domain */
6616 load
= target_load(i
, load_idx
);
6618 load
= source_load(i
, load_idx
);
6620 sgs
->group_load
+= load
;
6621 sgs
->group_util
+= cpu_util(i
);
6622 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
6624 nr_running
= rq
->nr_running
;
6628 #ifdef CONFIG_NUMA_BALANCING
6629 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
6630 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
6632 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
6634 * No need to call idle_cpu() if nr_running is not 0
6636 if (!nr_running
&& idle_cpu(i
))
6640 /* Adjust by relative CPU capacity of the group */
6641 sgs
->group_capacity
= group
->sgc
->capacity
;
6642 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
6644 if (sgs
->sum_nr_running
)
6645 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
6647 sgs
->group_weight
= group
->group_weight
;
6649 sgs
->group_no_capacity
= group_is_overloaded(env
, sgs
);
6650 sgs
->group_type
= group_classify(group
, sgs
);
6654 * update_sd_pick_busiest - return 1 on busiest group
6655 * @env: The load balancing environment.
6656 * @sds: sched_domain statistics
6657 * @sg: sched_group candidate to be checked for being the busiest
6658 * @sgs: sched_group statistics
6660 * Determine if @sg is a busier group than the previously selected
6663 * Return: %true if @sg is a busier group than the previously selected
6664 * busiest group. %false otherwise.
6666 static bool update_sd_pick_busiest(struct lb_env
*env
,
6667 struct sd_lb_stats
*sds
,
6668 struct sched_group
*sg
,
6669 struct sg_lb_stats
*sgs
)
6671 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
6673 if (sgs
->group_type
> busiest
->group_type
)
6676 if (sgs
->group_type
< busiest
->group_type
)
6679 if (sgs
->avg_load
<= busiest
->avg_load
)
6682 /* This is the busiest node in its class. */
6683 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6686 /* No ASYM_PACKING if target cpu is already busy */
6687 if (env
->idle
== CPU_NOT_IDLE
)
6690 * ASYM_PACKING needs to move all the work to the lowest
6691 * numbered CPUs in the group, therefore mark all groups
6692 * higher than ourself as busy.
6694 if (sgs
->sum_nr_running
&& env
->dst_cpu
< group_first_cpu(sg
)) {
6698 /* Prefer to move from highest possible cpu's work */
6699 if (group_first_cpu(sds
->busiest
) < group_first_cpu(sg
))
6706 #ifdef CONFIG_NUMA_BALANCING
6707 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6709 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
6711 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
6716 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6718 if (rq
->nr_running
> rq
->nr_numa_running
)
6720 if (rq
->nr_running
> rq
->nr_preferred_running
)
6725 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6730 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6734 #endif /* CONFIG_NUMA_BALANCING */
6737 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6738 * @env: The load balancing environment.
6739 * @sds: variable to hold the statistics for this sched_domain.
6741 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6743 struct sched_domain
*child
= env
->sd
->child
;
6744 struct sched_group
*sg
= env
->sd
->groups
;
6745 struct sg_lb_stats tmp_sgs
;
6746 int load_idx
, prefer_sibling
= 0;
6747 bool overload
= false;
6749 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
6752 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
6755 struct sg_lb_stats
*sgs
= &tmp_sgs
;
6758 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
6761 sgs
= &sds
->local_stat
;
6763 if (env
->idle
!= CPU_NEWLY_IDLE
||
6764 time_after_eq(jiffies
, sg
->sgc
->next_update
))
6765 update_group_capacity(env
->sd
, env
->dst_cpu
);
6768 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
6775 * In case the child domain prefers tasks go to siblings
6776 * first, lower the sg capacity so that we'll try
6777 * and move all the excess tasks away. We lower the capacity
6778 * of a group only if the local group has the capacity to fit
6779 * these excess tasks. The extra check prevents the case where
6780 * you always pull from the heaviest group when it is already
6781 * under-utilized (possible with a large weight task outweighs
6782 * the tasks on the system).
6784 if (prefer_sibling
&& sds
->local
&&
6785 group_has_capacity(env
, &sds
->local_stat
) &&
6786 (sgs
->sum_nr_running
> 1)) {
6787 sgs
->group_no_capacity
= 1;
6788 sgs
->group_type
= group_classify(sg
, sgs
);
6791 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
6793 sds
->busiest_stat
= *sgs
;
6797 /* Now, start updating sd_lb_stats */
6798 sds
->total_load
+= sgs
->group_load
;
6799 sds
->total_capacity
+= sgs
->group_capacity
;
6802 } while (sg
!= env
->sd
->groups
);
6804 if (env
->sd
->flags
& SD_NUMA
)
6805 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
6807 if (!env
->sd
->parent
) {
6808 /* update overload indicator if we are at root domain */
6809 if (env
->dst_rq
->rd
->overload
!= overload
)
6810 env
->dst_rq
->rd
->overload
= overload
;
6816 * check_asym_packing - Check to see if the group is packed into the
6819 * This is primarily intended to used at the sibling level. Some
6820 * cores like POWER7 prefer to use lower numbered SMT threads. In the
6821 * case of POWER7, it can move to lower SMT modes only when higher
6822 * threads are idle. When in lower SMT modes, the threads will
6823 * perform better since they share less core resources. Hence when we
6824 * have idle threads, we want them to be the higher ones.
6826 * This packing function is run on idle threads. It checks to see if
6827 * the busiest CPU in this domain (core in the P7 case) has a higher
6828 * CPU number than the packing function is being run on. Here we are
6829 * assuming lower CPU number will be equivalent to lower a SMT thread
6832 * Return: 1 when packing is required and a task should be moved to
6833 * this CPU. The amount of the imbalance is returned in *imbalance.
6835 * @env: The load balancing environment.
6836 * @sds: Statistics of the sched_domain which is to be packed
6838 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6842 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6845 if (env
->idle
== CPU_NOT_IDLE
)
6851 busiest_cpu
= group_first_cpu(sds
->busiest
);
6852 if (env
->dst_cpu
> busiest_cpu
)
6855 env
->imbalance
= DIV_ROUND_CLOSEST(
6856 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
6857 SCHED_CAPACITY_SCALE
);
6863 * fix_small_imbalance - Calculate the minor imbalance that exists
6864 * amongst the groups of a sched_domain, during
6866 * @env: The load balancing environment.
6867 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
6870 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6872 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
6873 unsigned int imbn
= 2;
6874 unsigned long scaled_busy_load_per_task
;
6875 struct sg_lb_stats
*local
, *busiest
;
6877 local
= &sds
->local_stat
;
6878 busiest
= &sds
->busiest_stat
;
6880 if (!local
->sum_nr_running
)
6881 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
6882 else if (busiest
->load_per_task
> local
->load_per_task
)
6885 scaled_busy_load_per_task
=
6886 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6887 busiest
->group_capacity
;
6889 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
6890 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
6891 env
->imbalance
= busiest
->load_per_task
;
6896 * OK, we don't have enough imbalance to justify moving tasks,
6897 * however we may be able to increase total CPU capacity used by
6901 capa_now
+= busiest
->group_capacity
*
6902 min(busiest
->load_per_task
, busiest
->avg_load
);
6903 capa_now
+= local
->group_capacity
*
6904 min(local
->load_per_task
, local
->avg_load
);
6905 capa_now
/= SCHED_CAPACITY_SCALE
;
6907 /* Amount of load we'd subtract */
6908 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
6909 capa_move
+= busiest
->group_capacity
*
6910 min(busiest
->load_per_task
,
6911 busiest
->avg_load
- scaled_busy_load_per_task
);
6914 /* Amount of load we'd add */
6915 if (busiest
->avg_load
* busiest
->group_capacity
<
6916 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
6917 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
6918 local
->group_capacity
;
6920 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
6921 local
->group_capacity
;
6923 capa_move
+= local
->group_capacity
*
6924 min(local
->load_per_task
, local
->avg_load
+ tmp
);
6925 capa_move
/= SCHED_CAPACITY_SCALE
;
6927 /* Move if we gain throughput */
6928 if (capa_move
> capa_now
)
6929 env
->imbalance
= busiest
->load_per_task
;
6933 * calculate_imbalance - Calculate the amount of imbalance present within the
6934 * groups of a given sched_domain during load balance.
6935 * @env: load balance environment
6936 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
6938 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6940 unsigned long max_pull
, load_above_capacity
= ~0UL;
6941 struct sg_lb_stats
*local
, *busiest
;
6943 local
= &sds
->local_stat
;
6944 busiest
= &sds
->busiest_stat
;
6946 if (busiest
->group_type
== group_imbalanced
) {
6948 * In the group_imb case we cannot rely on group-wide averages
6949 * to ensure cpu-load equilibrium, look at wider averages. XXX
6951 busiest
->load_per_task
=
6952 min(busiest
->load_per_task
, sds
->avg_load
);
6956 * In the presence of smp nice balancing, certain scenarios can have
6957 * max load less than avg load(as we skip the groups at or below
6958 * its cpu_capacity, while calculating max_load..)
6960 if (busiest
->avg_load
<= sds
->avg_load
||
6961 local
->avg_load
>= sds
->avg_load
) {
6963 return fix_small_imbalance(env
, sds
);
6967 * If there aren't any idle cpus, avoid creating some.
6969 if (busiest
->group_type
== group_overloaded
&&
6970 local
->group_type
== group_overloaded
) {
6971 load_above_capacity
= busiest
->sum_nr_running
*
6973 if (load_above_capacity
> busiest
->group_capacity
)
6974 load_above_capacity
-= busiest
->group_capacity
;
6976 load_above_capacity
= ~0UL;
6980 * We're trying to get all the cpus to the average_load, so we don't
6981 * want to push ourselves above the average load, nor do we wish to
6982 * reduce the max loaded cpu below the average load. At the same time,
6983 * we also don't want to reduce the group load below the group capacity
6984 * (so that we can implement power-savings policies etc). Thus we look
6985 * for the minimum possible imbalance.
6987 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
6989 /* How much load to actually move to equalise the imbalance */
6990 env
->imbalance
= min(
6991 max_pull
* busiest
->group_capacity
,
6992 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
6993 ) / SCHED_CAPACITY_SCALE
;
6996 * if *imbalance is less than the average load per runnable task
6997 * there is no guarantee that any tasks will be moved so we'll have
6998 * a think about bumping its value to force at least one task to be
7001 if (env
->imbalance
< busiest
->load_per_task
)
7002 return fix_small_imbalance(env
, sds
);
7005 /******* find_busiest_group() helpers end here *********************/
7008 * find_busiest_group - Returns the busiest group within the sched_domain
7009 * if there is an imbalance. If there isn't an imbalance, and
7010 * the user has opted for power-savings, it returns a group whose
7011 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
7012 * such a group exists.
7014 * Also calculates the amount of weighted load which should be moved
7015 * to restore balance.
7017 * @env: The load balancing environment.
7019 * Return: - The busiest group if imbalance exists.
7020 * - If no imbalance and user has opted for power-savings balance,
7021 * return the least loaded group whose CPUs can be
7022 * put to idle by rebalancing its tasks onto our group.
7024 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
7026 struct sg_lb_stats
*local
, *busiest
;
7027 struct sd_lb_stats sds
;
7029 init_sd_lb_stats(&sds
);
7032 * Compute the various statistics relavent for load balancing at
7035 update_sd_lb_stats(env
, &sds
);
7036 local
= &sds
.local_stat
;
7037 busiest
= &sds
.busiest_stat
;
7039 /* ASYM feature bypasses nice load balance check */
7040 if (check_asym_packing(env
, &sds
))
7043 /* There is no busy sibling group to pull tasks from */
7044 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
7047 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
7048 / sds
.total_capacity
;
7051 * If the busiest group is imbalanced the below checks don't
7052 * work because they assume all things are equal, which typically
7053 * isn't true due to cpus_allowed constraints and the like.
7055 if (busiest
->group_type
== group_imbalanced
)
7058 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7059 if (env
->idle
== CPU_NEWLY_IDLE
&& group_has_capacity(env
, local
) &&
7060 busiest
->group_no_capacity
)
7064 * If the local group is busier than the selected busiest group
7065 * don't try and pull any tasks.
7067 if (local
->avg_load
>= busiest
->avg_load
)
7071 * Don't pull any tasks if this group is already above the domain
7074 if (local
->avg_load
>= sds
.avg_load
)
7077 if (env
->idle
== CPU_IDLE
) {
7079 * This cpu is idle. If the busiest group is not overloaded
7080 * and there is no imbalance between this and busiest group
7081 * wrt idle cpus, it is balanced. The imbalance becomes
7082 * significant if the diff is greater than 1 otherwise we
7083 * might end up to just move the imbalance on another group
7085 if ((busiest
->group_type
!= group_overloaded
) &&
7086 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
7090 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7091 * imbalance_pct to be conservative.
7093 if (100 * busiest
->avg_load
<=
7094 env
->sd
->imbalance_pct
* local
->avg_load
)
7099 /* Looks like there is an imbalance. Compute it */
7100 calculate_imbalance(env
, &sds
);
7109 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7111 static struct rq
*find_busiest_queue(struct lb_env
*env
,
7112 struct sched_group
*group
)
7114 struct rq
*busiest
= NULL
, *rq
;
7115 unsigned long busiest_load
= 0, busiest_capacity
= 1;
7118 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
7119 unsigned long capacity
, wl
;
7123 rt
= fbq_classify_rq(rq
);
7126 * We classify groups/runqueues into three groups:
7127 * - regular: there are !numa tasks
7128 * - remote: there are numa tasks that run on the 'wrong' node
7129 * - all: there is no distinction
7131 * In order to avoid migrating ideally placed numa tasks,
7132 * ignore those when there's better options.
7134 * If we ignore the actual busiest queue to migrate another
7135 * task, the next balance pass can still reduce the busiest
7136 * queue by moving tasks around inside the node.
7138 * If we cannot move enough load due to this classification
7139 * the next pass will adjust the group classification and
7140 * allow migration of more tasks.
7142 * Both cases only affect the total convergence complexity.
7144 if (rt
> env
->fbq_type
)
7147 capacity
= capacity_of(i
);
7149 wl
= weighted_cpuload(i
);
7152 * When comparing with imbalance, use weighted_cpuload()
7153 * which is not scaled with the cpu capacity.
7156 if (rq
->nr_running
== 1 && wl
> env
->imbalance
&&
7157 !check_cpu_capacity(rq
, env
->sd
))
7161 * For the load comparisons with the other cpu's, consider
7162 * the weighted_cpuload() scaled with the cpu capacity, so
7163 * that the load can be moved away from the cpu that is
7164 * potentially running at a lower capacity.
7166 * Thus we're looking for max(wl_i / capacity_i), crosswise
7167 * multiplication to rid ourselves of the division works out
7168 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7169 * our previous maximum.
7171 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
7173 busiest_capacity
= capacity
;
7182 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7183 * so long as it is large enough.
7185 #define MAX_PINNED_INTERVAL 512
7187 /* Working cpumask for load_balance and load_balance_newidle. */
7188 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
7190 static int need_active_balance(struct lb_env
*env
)
7192 struct sched_domain
*sd
= env
->sd
;
7194 if (env
->idle
== CPU_NEWLY_IDLE
) {
7197 * ASYM_PACKING needs to force migrate tasks from busy but
7198 * higher numbered CPUs in order to pack all tasks in the
7199 * lowest numbered CPUs.
7201 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
7206 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7207 * It's worth migrating the task if the src_cpu's capacity is reduced
7208 * because of other sched_class or IRQs if more capacity stays
7209 * available on dst_cpu.
7211 if ((env
->idle
!= CPU_NOT_IDLE
) &&
7212 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
7213 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
7214 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
7218 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
7221 static int active_load_balance_cpu_stop(void *data
);
7223 static int should_we_balance(struct lb_env
*env
)
7225 struct sched_group
*sg
= env
->sd
->groups
;
7226 struct cpumask
*sg_cpus
, *sg_mask
;
7227 int cpu
, balance_cpu
= -1;
7230 * In the newly idle case, we will allow all the cpu's
7231 * to do the newly idle load balance.
7233 if (env
->idle
== CPU_NEWLY_IDLE
)
7236 sg_cpus
= sched_group_cpus(sg
);
7237 sg_mask
= sched_group_mask(sg
);
7238 /* Try to find first idle cpu */
7239 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
7240 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
7247 if (balance_cpu
== -1)
7248 balance_cpu
= group_balance_cpu(sg
);
7251 * First idle cpu or the first cpu(busiest) in this sched group
7252 * is eligible for doing load balancing at this and above domains.
7254 return balance_cpu
== env
->dst_cpu
;
7258 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7259 * tasks if there is an imbalance.
7261 static int load_balance(int this_cpu
, struct rq
*this_rq
,
7262 struct sched_domain
*sd
, enum cpu_idle_type idle
,
7263 int *continue_balancing
)
7265 int ld_moved
, cur_ld_moved
, active_balance
= 0;
7266 struct sched_domain
*sd_parent
= sd
->parent
;
7267 struct sched_group
*group
;
7269 unsigned long flags
;
7270 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
7272 struct lb_env env
= {
7274 .dst_cpu
= this_cpu
,
7276 .dst_grpmask
= sched_group_cpus(sd
->groups
),
7278 .loop_break
= sched_nr_migrate_break
,
7281 .tasks
= LIST_HEAD_INIT(env
.tasks
),
7285 * For NEWLY_IDLE load_balancing, we don't need to consider
7286 * other cpus in our group
7288 if (idle
== CPU_NEWLY_IDLE
)
7289 env
.dst_grpmask
= NULL
;
7291 cpumask_copy(cpus
, cpu_active_mask
);
7293 schedstat_inc(sd
, lb_count
[idle
]);
7296 if (!should_we_balance(&env
)) {
7297 *continue_balancing
= 0;
7301 group
= find_busiest_group(&env
);
7303 schedstat_inc(sd
, lb_nobusyg
[idle
]);
7307 busiest
= find_busiest_queue(&env
, group
);
7309 schedstat_inc(sd
, lb_nobusyq
[idle
]);
7313 BUG_ON(busiest
== env
.dst_rq
);
7315 schedstat_add(sd
, lb_imbalance
[idle
], env
.imbalance
);
7317 env
.src_cpu
= busiest
->cpu
;
7318 env
.src_rq
= busiest
;
7321 if (busiest
->nr_running
> 1) {
7323 * Attempt to move tasks. If find_busiest_group has found
7324 * an imbalance but busiest->nr_running <= 1, the group is
7325 * still unbalanced. ld_moved simply stays zero, so it is
7326 * correctly treated as an imbalance.
7328 env
.flags
|= LBF_ALL_PINNED
;
7329 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
7332 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7335 * cur_ld_moved - load moved in current iteration
7336 * ld_moved - cumulative load moved across iterations
7338 cur_ld_moved
= detach_tasks(&env
);
7341 * We've detached some tasks from busiest_rq. Every
7342 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7343 * unlock busiest->lock, and we are able to be sure
7344 * that nobody can manipulate the tasks in parallel.
7345 * See task_rq_lock() family for the details.
7348 raw_spin_unlock(&busiest
->lock
);
7352 ld_moved
+= cur_ld_moved
;
7355 local_irq_restore(flags
);
7357 if (env
.flags
& LBF_NEED_BREAK
) {
7358 env
.flags
&= ~LBF_NEED_BREAK
;
7363 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7364 * us and move them to an alternate dst_cpu in our sched_group
7365 * where they can run. The upper limit on how many times we
7366 * iterate on same src_cpu is dependent on number of cpus in our
7369 * This changes load balance semantics a bit on who can move
7370 * load to a given_cpu. In addition to the given_cpu itself
7371 * (or a ilb_cpu acting on its behalf where given_cpu is
7372 * nohz-idle), we now have balance_cpu in a position to move
7373 * load to given_cpu. In rare situations, this may cause
7374 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7375 * _independently_ and at _same_ time to move some load to
7376 * given_cpu) causing exceess load to be moved to given_cpu.
7377 * This however should not happen so much in practice and
7378 * moreover subsequent load balance cycles should correct the
7379 * excess load moved.
7381 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
7383 /* Prevent to re-select dst_cpu via env's cpus */
7384 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
7386 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
7387 env
.dst_cpu
= env
.new_dst_cpu
;
7388 env
.flags
&= ~LBF_DST_PINNED
;
7390 env
.loop_break
= sched_nr_migrate_break
;
7393 * Go back to "more_balance" rather than "redo" since we
7394 * need to continue with same src_cpu.
7400 * We failed to reach balance because of affinity.
7403 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7405 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
7406 *group_imbalance
= 1;
7409 /* All tasks on this runqueue were pinned by CPU affinity */
7410 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
7411 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
7412 if (!cpumask_empty(cpus
)) {
7414 env
.loop_break
= sched_nr_migrate_break
;
7417 goto out_all_pinned
;
7422 schedstat_inc(sd
, lb_failed
[idle
]);
7424 * Increment the failure counter only on periodic balance.
7425 * We do not want newidle balance, which can be very
7426 * frequent, pollute the failure counter causing
7427 * excessive cache_hot migrations and active balances.
7429 if (idle
!= CPU_NEWLY_IDLE
)
7430 sd
->nr_balance_failed
++;
7432 if (need_active_balance(&env
)) {
7433 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7435 /* don't kick the active_load_balance_cpu_stop,
7436 * if the curr task on busiest cpu can't be
7439 if (!cpumask_test_cpu(this_cpu
,
7440 tsk_cpus_allowed(busiest
->curr
))) {
7441 raw_spin_unlock_irqrestore(&busiest
->lock
,
7443 env
.flags
|= LBF_ALL_PINNED
;
7444 goto out_one_pinned
;
7448 * ->active_balance synchronizes accesses to
7449 * ->active_balance_work. Once set, it's cleared
7450 * only after active load balance is finished.
7452 if (!busiest
->active_balance
) {
7453 busiest
->active_balance
= 1;
7454 busiest
->push_cpu
= this_cpu
;
7457 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
7459 if (active_balance
) {
7460 stop_one_cpu_nowait(cpu_of(busiest
),
7461 active_load_balance_cpu_stop
, busiest
,
7462 &busiest
->active_balance_work
);
7465 /* We've kicked active balancing, force task migration. */
7466 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
7469 sd
->nr_balance_failed
= 0;
7471 if (likely(!active_balance
)) {
7472 /* We were unbalanced, so reset the balancing interval */
7473 sd
->balance_interval
= sd
->min_interval
;
7476 * If we've begun active balancing, start to back off. This
7477 * case may not be covered by the all_pinned logic if there
7478 * is only 1 task on the busy runqueue (because we don't call
7481 if (sd
->balance_interval
< sd
->max_interval
)
7482 sd
->balance_interval
*= 2;
7489 * We reach balance although we may have faced some affinity
7490 * constraints. Clear the imbalance flag if it was set.
7493 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7495 if (*group_imbalance
)
7496 *group_imbalance
= 0;
7501 * We reach balance because all tasks are pinned at this level so
7502 * we can't migrate them. Let the imbalance flag set so parent level
7503 * can try to migrate them.
7505 schedstat_inc(sd
, lb_balanced
[idle
]);
7507 sd
->nr_balance_failed
= 0;
7510 /* tune up the balancing interval */
7511 if (((env
.flags
& LBF_ALL_PINNED
) &&
7512 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
7513 (sd
->balance_interval
< sd
->max_interval
))
7514 sd
->balance_interval
*= 2;
7521 static inline unsigned long
7522 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
7524 unsigned long interval
= sd
->balance_interval
;
7527 interval
*= sd
->busy_factor
;
7529 /* scale ms to jiffies */
7530 interval
= msecs_to_jiffies(interval
);
7531 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7537 update_next_balance(struct sched_domain
*sd
, int cpu_busy
, unsigned long *next_balance
)
7539 unsigned long interval
, next
;
7541 interval
= get_sd_balance_interval(sd
, cpu_busy
);
7542 next
= sd
->last_balance
+ interval
;
7544 if (time_after(*next_balance
, next
))
7545 *next_balance
= next
;
7549 * idle_balance is called by schedule() if this_cpu is about to become
7550 * idle. Attempts to pull tasks from other CPUs.
7552 static int idle_balance(struct rq
*this_rq
)
7554 unsigned long next_balance
= jiffies
+ HZ
;
7555 int this_cpu
= this_rq
->cpu
;
7556 struct sched_domain
*sd
;
7557 int pulled_task
= 0;
7561 * We must set idle_stamp _before_ calling idle_balance(), such that we
7562 * measure the duration of idle_balance() as idle time.
7564 this_rq
->idle_stamp
= rq_clock(this_rq
);
7566 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
7567 !this_rq
->rd
->overload
) {
7569 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
7571 update_next_balance(sd
, 0, &next_balance
);
7577 raw_spin_unlock(&this_rq
->lock
);
7579 update_blocked_averages(this_cpu
);
7581 for_each_domain(this_cpu
, sd
) {
7582 int continue_balancing
= 1;
7583 u64 t0
, domain_cost
;
7585 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7588 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
7589 update_next_balance(sd
, 0, &next_balance
);
7593 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
7594 t0
= sched_clock_cpu(this_cpu
);
7596 pulled_task
= load_balance(this_cpu
, this_rq
,
7598 &continue_balancing
);
7600 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
7601 if (domain_cost
> sd
->max_newidle_lb_cost
)
7602 sd
->max_newidle_lb_cost
= domain_cost
;
7604 curr_cost
+= domain_cost
;
7607 update_next_balance(sd
, 0, &next_balance
);
7610 * Stop searching for tasks to pull if there are
7611 * now runnable tasks on this rq.
7613 if (pulled_task
|| this_rq
->nr_running
> 0)
7618 raw_spin_lock(&this_rq
->lock
);
7620 if (curr_cost
> this_rq
->max_idle_balance_cost
)
7621 this_rq
->max_idle_balance_cost
= curr_cost
;
7624 * While browsing the domains, we released the rq lock, a task could
7625 * have been enqueued in the meantime. Since we're not going idle,
7626 * pretend we pulled a task.
7628 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
7632 /* Move the next balance forward */
7633 if (time_after(this_rq
->next_balance
, next_balance
))
7634 this_rq
->next_balance
= next_balance
;
7636 /* Is there a task of a high priority class? */
7637 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
7641 this_rq
->idle_stamp
= 0;
7647 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7648 * running tasks off the busiest CPU onto idle CPUs. It requires at
7649 * least 1 task to be running on each physical CPU where possible, and
7650 * avoids physical / logical imbalances.
7652 static int active_load_balance_cpu_stop(void *data
)
7654 struct rq
*busiest_rq
= data
;
7655 int busiest_cpu
= cpu_of(busiest_rq
);
7656 int target_cpu
= busiest_rq
->push_cpu
;
7657 struct rq
*target_rq
= cpu_rq(target_cpu
);
7658 struct sched_domain
*sd
;
7659 struct task_struct
*p
= NULL
;
7661 raw_spin_lock_irq(&busiest_rq
->lock
);
7663 /* make sure the requested cpu hasn't gone down in the meantime */
7664 if (unlikely(busiest_cpu
!= smp_processor_id() ||
7665 !busiest_rq
->active_balance
))
7668 /* Is there any task to move? */
7669 if (busiest_rq
->nr_running
<= 1)
7673 * This condition is "impossible", if it occurs
7674 * we need to fix it. Originally reported by
7675 * Bjorn Helgaas on a 128-cpu setup.
7677 BUG_ON(busiest_rq
== target_rq
);
7679 /* Search for an sd spanning us and the target CPU. */
7681 for_each_domain(target_cpu
, sd
) {
7682 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
7683 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
7688 struct lb_env env
= {
7690 .dst_cpu
= target_cpu
,
7691 .dst_rq
= target_rq
,
7692 .src_cpu
= busiest_rq
->cpu
,
7693 .src_rq
= busiest_rq
,
7697 schedstat_inc(sd
, alb_count
);
7699 p
= detach_one_task(&env
);
7701 schedstat_inc(sd
, alb_pushed
);
7702 /* Active balancing done, reset the failure counter. */
7703 sd
->nr_balance_failed
= 0;
7705 schedstat_inc(sd
, alb_failed
);
7710 busiest_rq
->active_balance
= 0;
7711 raw_spin_unlock(&busiest_rq
->lock
);
7714 attach_one_task(target_rq
, p
);
7721 static inline int on_null_domain(struct rq
*rq
)
7723 return unlikely(!rcu_dereference_sched(rq
->sd
));
7726 #ifdef CONFIG_NO_HZ_COMMON
7728 * idle load balancing details
7729 * - When one of the busy CPUs notice that there may be an idle rebalancing
7730 * needed, they will kick the idle load balancer, which then does idle
7731 * load balancing for all the idle CPUs.
7734 cpumask_var_t idle_cpus_mask
;
7736 unsigned long next_balance
; /* in jiffy units */
7737 } nohz ____cacheline_aligned
;
7739 static inline int find_new_ilb(void)
7741 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
7743 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
7750 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7751 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7752 * CPU (if there is one).
7754 static void nohz_balancer_kick(void)
7758 nohz
.next_balance
++;
7760 ilb_cpu
= find_new_ilb();
7762 if (ilb_cpu
>= nr_cpu_ids
)
7765 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
7768 * Use smp_send_reschedule() instead of resched_cpu().
7769 * This way we generate a sched IPI on the target cpu which
7770 * is idle. And the softirq performing nohz idle load balance
7771 * will be run before returning from the IPI.
7773 smp_send_reschedule(ilb_cpu
);
7777 static inline void nohz_balance_exit_idle(int cpu
)
7779 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
7781 * Completely isolated CPUs don't ever set, so we must test.
7783 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
7784 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
7785 atomic_dec(&nohz
.nr_cpus
);
7787 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7791 static inline void set_cpu_sd_state_busy(void)
7793 struct sched_domain
*sd
;
7794 int cpu
= smp_processor_id();
7797 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7799 if (!sd
|| !sd
->nohz_idle
)
7803 atomic_inc(&sd
->groups
->sgc
->nr_busy_cpus
);
7808 void set_cpu_sd_state_idle(void)
7810 struct sched_domain
*sd
;
7811 int cpu
= smp_processor_id();
7814 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
7816 if (!sd
|| sd
->nohz_idle
)
7820 atomic_dec(&sd
->groups
->sgc
->nr_busy_cpus
);
7826 * This routine will record that the cpu is going idle with tick stopped.
7827 * This info will be used in performing idle load balancing in the future.
7829 void nohz_balance_enter_idle(int cpu
)
7832 * If this cpu is going down, then nothing needs to be done.
7834 if (!cpu_active(cpu
))
7837 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
7841 * If we're a completely isolated CPU, we don't play.
7843 if (on_null_domain(cpu_rq(cpu
)))
7846 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
7847 atomic_inc(&nohz
.nr_cpus
);
7848 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7851 static int sched_ilb_notifier(struct notifier_block
*nfb
,
7852 unsigned long action
, void *hcpu
)
7854 switch (action
& ~CPU_TASKS_FROZEN
) {
7856 nohz_balance_exit_idle(smp_processor_id());
7864 static DEFINE_SPINLOCK(balancing
);
7867 * Scale the max load_balance interval with the number of CPUs in the system.
7868 * This trades load-balance latency on larger machines for less cross talk.
7870 void update_max_interval(void)
7872 max_load_balance_interval
= HZ
*num_online_cpus()/10;
7876 * It checks each scheduling domain to see if it is due to be balanced,
7877 * and initiates a balancing operation if so.
7879 * Balancing parameters are set up in init_sched_domains.
7881 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
7883 int continue_balancing
= 1;
7885 unsigned long interval
;
7886 struct sched_domain
*sd
;
7887 /* Earliest time when we have to do rebalance again */
7888 unsigned long next_balance
= jiffies
+ 60*HZ
;
7889 int update_next_balance
= 0;
7890 int need_serialize
, need_decay
= 0;
7893 update_blocked_averages(cpu
);
7896 for_each_domain(cpu
, sd
) {
7898 * Decay the newidle max times here because this is a regular
7899 * visit to all the domains. Decay ~1% per second.
7901 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
7902 sd
->max_newidle_lb_cost
=
7903 (sd
->max_newidle_lb_cost
* 253) / 256;
7904 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
7907 max_cost
+= sd
->max_newidle_lb_cost
;
7909 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7913 * Stop the load balance at this level. There is another
7914 * CPU in our sched group which is doing load balancing more
7917 if (!continue_balancing
) {
7923 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
7925 need_serialize
= sd
->flags
& SD_SERIALIZE
;
7926 if (need_serialize
) {
7927 if (!spin_trylock(&balancing
))
7931 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
7932 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
7934 * The LBF_DST_PINNED logic could have changed
7935 * env->dst_cpu, so we can't know our idle
7936 * state even if we migrated tasks. Update it.
7938 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
7940 sd
->last_balance
= jiffies
;
7941 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
7944 spin_unlock(&balancing
);
7946 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
7947 next_balance
= sd
->last_balance
+ interval
;
7948 update_next_balance
= 1;
7953 * Ensure the rq-wide value also decays but keep it at a
7954 * reasonable floor to avoid funnies with rq->avg_idle.
7956 rq
->max_idle_balance_cost
=
7957 max((u64
)sysctl_sched_migration_cost
, max_cost
);
7962 * next_balance will be updated only when there is a need.
7963 * When the cpu is attached to null domain for ex, it will not be
7966 if (likely(update_next_balance
)) {
7967 rq
->next_balance
= next_balance
;
7969 #ifdef CONFIG_NO_HZ_COMMON
7971 * If this CPU has been elected to perform the nohz idle
7972 * balance. Other idle CPUs have already rebalanced with
7973 * nohz_idle_balance() and nohz.next_balance has been
7974 * updated accordingly. This CPU is now running the idle load
7975 * balance for itself and we need to update the
7976 * nohz.next_balance accordingly.
7978 if ((idle
== CPU_IDLE
) && time_after(nohz
.next_balance
, rq
->next_balance
))
7979 nohz
.next_balance
= rq
->next_balance
;
7984 #ifdef CONFIG_NO_HZ_COMMON
7986 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7987 * rebalancing for all the cpus for whom scheduler ticks are stopped.
7989 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
7991 int this_cpu
= this_rq
->cpu
;
7994 /* Earliest time when we have to do rebalance again */
7995 unsigned long next_balance
= jiffies
+ 60*HZ
;
7996 int update_next_balance
= 0;
7998 if (idle
!= CPU_IDLE
||
7999 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
8002 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
8003 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
8007 * If this cpu gets work to do, stop the load balancing
8008 * work being done for other cpus. Next load
8009 * balancing owner will pick it up.
8014 rq
= cpu_rq(balance_cpu
);
8017 * If time for next balance is due,
8020 if (time_after_eq(jiffies
, rq
->next_balance
)) {
8021 raw_spin_lock_irq(&rq
->lock
);
8022 update_rq_clock(rq
);
8023 update_cpu_load_idle(rq
);
8024 raw_spin_unlock_irq(&rq
->lock
);
8025 rebalance_domains(rq
, CPU_IDLE
);
8028 if (time_after(next_balance
, rq
->next_balance
)) {
8029 next_balance
= rq
->next_balance
;
8030 update_next_balance
= 1;
8035 * next_balance will be updated only when there is a need.
8036 * When the CPU is attached to null domain for ex, it will not be
8039 if (likely(update_next_balance
))
8040 nohz
.next_balance
= next_balance
;
8042 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
8046 * Current heuristic for kicking the idle load balancer in the presence
8047 * of an idle cpu in the system.
8048 * - This rq has more than one task.
8049 * - This rq has at least one CFS task and the capacity of the CPU is
8050 * significantly reduced because of RT tasks or IRQs.
8051 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8052 * multiple busy cpu.
8053 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8054 * domain span are idle.
8056 static inline bool nohz_kick_needed(struct rq
*rq
)
8058 unsigned long now
= jiffies
;
8059 struct sched_domain
*sd
;
8060 struct sched_group_capacity
*sgc
;
8061 int nr_busy
, cpu
= rq
->cpu
;
8064 if (unlikely(rq
->idle_balance
))
8068 * We may be recently in ticked or tickless idle mode. At the first
8069 * busy tick after returning from idle, we will update the busy stats.
8071 set_cpu_sd_state_busy();
8072 nohz_balance_exit_idle(cpu
);
8075 * None are in tickless mode and hence no need for NOHZ idle load
8078 if (likely(!atomic_read(&nohz
.nr_cpus
)))
8081 if (time_before(now
, nohz
.next_balance
))
8084 if (rq
->nr_running
>= 2)
8088 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8090 sgc
= sd
->groups
->sgc
;
8091 nr_busy
= atomic_read(&sgc
->nr_busy_cpus
);
8100 sd
= rcu_dereference(rq
->sd
);
8102 if ((rq
->cfs
.h_nr_running
>= 1) &&
8103 check_cpu_capacity(rq
, sd
)) {
8109 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
8110 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
8111 sched_domain_span(sd
)) < cpu
)) {
8121 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
8125 * run_rebalance_domains is triggered when needed from the scheduler tick.
8126 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8128 static void run_rebalance_domains(struct softirq_action
*h
)
8130 struct rq
*this_rq
= this_rq();
8131 enum cpu_idle_type idle
= this_rq
->idle_balance
?
8132 CPU_IDLE
: CPU_NOT_IDLE
;
8135 * If this cpu has a pending nohz_balance_kick, then do the
8136 * balancing on behalf of the other idle cpus whose ticks are
8137 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8138 * give the idle cpus a chance to load balance. Else we may
8139 * load balance only within the local sched_domain hierarchy
8140 * and abort nohz_idle_balance altogether if we pull some load.
8142 nohz_idle_balance(this_rq
, idle
);
8143 rebalance_domains(this_rq
, idle
);
8147 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8149 void trigger_load_balance(struct rq
*rq
)
8151 /* Don't need to rebalance while attached to NULL domain */
8152 if (unlikely(on_null_domain(rq
)))
8155 if (time_after_eq(jiffies
, rq
->next_balance
))
8156 raise_softirq(SCHED_SOFTIRQ
);
8157 #ifdef CONFIG_NO_HZ_COMMON
8158 if (nohz_kick_needed(rq
))
8159 nohz_balancer_kick();
8163 static void rq_online_fair(struct rq
*rq
)
8167 update_runtime_enabled(rq
);
8170 static void rq_offline_fair(struct rq
*rq
)
8174 /* Ensure any throttled groups are reachable by pick_next_task */
8175 unthrottle_offline_cfs_rqs(rq
);
8178 #endif /* CONFIG_SMP */
8181 * scheduler tick hitting a task of our scheduling class:
8183 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
8185 struct cfs_rq
*cfs_rq
;
8186 struct sched_entity
*se
= &curr
->se
;
8188 for_each_sched_entity(se
) {
8189 cfs_rq
= cfs_rq_of(se
);
8190 entity_tick(cfs_rq
, se
, queued
);
8193 if (static_branch_unlikely(&sched_numa_balancing
))
8194 task_tick_numa(rq
, curr
);
8198 * called on fork with the child task as argument from the parent's context
8199 * - child not yet on the tasklist
8200 * - preemption disabled
8202 static void task_fork_fair(struct task_struct
*p
)
8204 struct cfs_rq
*cfs_rq
;
8205 struct sched_entity
*se
= &p
->se
, *curr
;
8206 int this_cpu
= smp_processor_id();
8207 struct rq
*rq
= this_rq();
8208 unsigned long flags
;
8210 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8212 update_rq_clock(rq
);
8214 cfs_rq
= task_cfs_rq(current
);
8215 curr
= cfs_rq
->curr
;
8218 * Not only the cpu but also the task_group of the parent might have
8219 * been changed after parent->se.parent,cfs_rq were copied to
8220 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
8221 * of child point to valid ones.
8224 __set_task_cpu(p
, this_cpu
);
8227 update_curr(cfs_rq
);
8230 se
->vruntime
= curr
->vruntime
;
8231 place_entity(cfs_rq
, se
, 1);
8233 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
8235 * Upon rescheduling, sched_class::put_prev_task() will place
8236 * 'current' within the tree based on its new key value.
8238 swap(curr
->vruntime
, se
->vruntime
);
8242 se
->vruntime
-= cfs_rq
->min_vruntime
;
8244 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8248 * Priority of the task has changed. Check to see if we preempt
8252 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
8254 if (!task_on_rq_queued(p
))
8258 * Reschedule if we are currently running on this runqueue and
8259 * our priority decreased, or if we are not currently running on
8260 * this runqueue and our priority is higher than the current's
8262 if (rq
->curr
== p
) {
8263 if (p
->prio
> oldprio
)
8266 check_preempt_curr(rq
, p
, 0);
8269 static inline bool vruntime_normalized(struct task_struct
*p
)
8271 struct sched_entity
*se
= &p
->se
;
8274 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8275 * the dequeue_entity(.flags=0) will already have normalized the
8282 * When !on_rq, vruntime of the task has usually NOT been normalized.
8283 * But there are some cases where it has already been normalized:
8285 * - A forked child which is waiting for being woken up by
8286 * wake_up_new_task().
8287 * - A task which has been woken up by try_to_wake_up() and
8288 * waiting for actually being woken up by sched_ttwu_pending().
8290 if (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
)
8296 static void detach_task_cfs_rq(struct task_struct
*p
)
8298 struct sched_entity
*se
= &p
->se
;
8299 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8301 if (!vruntime_normalized(p
)) {
8303 * Fix up our vruntime so that the current sleep doesn't
8304 * cause 'unlimited' sleep bonus.
8306 place_entity(cfs_rq
, se
, 0);
8307 se
->vruntime
-= cfs_rq
->min_vruntime
;
8310 /* Catch up with the cfs_rq and remove our load when we leave */
8311 detach_entity_load_avg(cfs_rq
, se
);
8314 static void attach_task_cfs_rq(struct task_struct
*p
)
8316 struct sched_entity
*se
= &p
->se
;
8317 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8319 #ifdef CONFIG_FAIR_GROUP_SCHED
8321 * Since the real-depth could have been changed (only FAIR
8322 * class maintain depth value), reset depth properly.
8324 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8327 /* Synchronize task with its cfs_rq */
8328 attach_entity_load_avg(cfs_rq
, se
);
8330 if (!vruntime_normalized(p
))
8331 se
->vruntime
+= cfs_rq
->min_vruntime
;
8334 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
8336 detach_task_cfs_rq(p
);
8339 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
8341 attach_task_cfs_rq(p
);
8343 if (task_on_rq_queued(p
)) {
8345 * We were most likely switched from sched_rt, so
8346 * kick off the schedule if running, otherwise just see
8347 * if we can still preempt the current task.
8352 check_preempt_curr(rq
, p
, 0);
8356 /* Account for a task changing its policy or group.
8358 * This routine is mostly called to set cfs_rq->curr field when a task
8359 * migrates between groups/classes.
8361 static void set_curr_task_fair(struct rq
*rq
)
8363 struct sched_entity
*se
= &rq
->curr
->se
;
8365 for_each_sched_entity(se
) {
8366 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8368 set_next_entity(cfs_rq
, se
);
8369 /* ensure bandwidth has been allocated on our new cfs_rq */
8370 account_cfs_rq_runtime(cfs_rq
, 0);
8374 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
8376 cfs_rq
->tasks_timeline
= RB_ROOT
;
8377 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
8378 #ifndef CONFIG_64BIT
8379 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
8382 atomic_long_set(&cfs_rq
->removed_load_avg
, 0);
8383 atomic_long_set(&cfs_rq
->removed_util_avg
, 0);
8387 #ifdef CONFIG_FAIR_GROUP_SCHED
8388 static void task_move_group_fair(struct task_struct
*p
)
8390 detach_task_cfs_rq(p
);
8391 set_task_rq(p
, task_cpu(p
));
8394 /* Tell se's cfs_rq has been changed -- migrated */
8395 p
->se
.avg
.last_update_time
= 0;
8397 attach_task_cfs_rq(p
);
8400 void free_fair_sched_group(struct task_group
*tg
)
8404 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8406 for_each_possible_cpu(i
) {
8408 kfree(tg
->cfs_rq
[i
]);
8417 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8419 struct cfs_rq
*cfs_rq
;
8420 struct sched_entity
*se
;
8423 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
8426 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
8430 tg
->shares
= NICE_0_LOAD
;
8432 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8434 for_each_possible_cpu(i
) {
8435 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
8436 GFP_KERNEL
, cpu_to_node(i
));
8440 se
= kzalloc_node(sizeof(struct sched_entity
),
8441 GFP_KERNEL
, cpu_to_node(i
));
8445 init_cfs_rq(cfs_rq
);
8446 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
8447 init_entity_runnable_average(se
);
8448 post_init_entity_util_avg(se
);
8459 void unregister_fair_sched_group(struct task_group
*tg
)
8461 unsigned long flags
;
8465 for_each_possible_cpu(cpu
) {
8467 remove_entity_load_avg(tg
->se
[cpu
]);
8470 * Only empty task groups can be destroyed; so we can speculatively
8471 * check on_list without danger of it being re-added.
8473 if (!tg
->cfs_rq
[cpu
]->on_list
)
8478 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8479 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
8480 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8484 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
8485 struct sched_entity
*se
, int cpu
,
8486 struct sched_entity
*parent
)
8488 struct rq
*rq
= cpu_rq(cpu
);
8492 init_cfs_rq_runtime(cfs_rq
);
8494 tg
->cfs_rq
[cpu
] = cfs_rq
;
8497 /* se could be NULL for root_task_group */
8502 se
->cfs_rq
= &rq
->cfs
;
8505 se
->cfs_rq
= parent
->my_q
;
8506 se
->depth
= parent
->depth
+ 1;
8510 /* guarantee group entities always have weight */
8511 update_load_set(&se
->load
, NICE_0_LOAD
);
8512 se
->parent
= parent
;
8515 static DEFINE_MUTEX(shares_mutex
);
8517 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
8520 unsigned long flags
;
8523 * We can't change the weight of the root cgroup.
8528 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
8530 mutex_lock(&shares_mutex
);
8531 if (tg
->shares
== shares
)
8534 tg
->shares
= shares
;
8535 for_each_possible_cpu(i
) {
8536 struct rq
*rq
= cpu_rq(i
);
8537 struct sched_entity
*se
;
8540 /* Propagate contribution to hierarchy */
8541 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8543 /* Possible calls to update_curr() need rq clock */
8544 update_rq_clock(rq
);
8545 for_each_sched_entity(se
)
8546 update_cfs_shares(group_cfs_rq(se
));
8547 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8551 mutex_unlock(&shares_mutex
);
8554 #else /* CONFIG_FAIR_GROUP_SCHED */
8556 void free_fair_sched_group(struct task_group
*tg
) { }
8558 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8563 void unregister_fair_sched_group(struct task_group
*tg
) { }
8565 #endif /* CONFIG_FAIR_GROUP_SCHED */
8568 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
8570 struct sched_entity
*se
= &task
->se
;
8571 unsigned int rr_interval
= 0;
8574 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8577 if (rq
->cfs
.load
.weight
)
8578 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
8584 * All the scheduling class methods:
8586 const struct sched_class fair_sched_class
= {
8587 .next
= &idle_sched_class
,
8588 .enqueue_task
= enqueue_task_fair
,
8589 .dequeue_task
= dequeue_task_fair
,
8590 .yield_task
= yield_task_fair
,
8591 .yield_to_task
= yield_to_task_fair
,
8593 .check_preempt_curr
= check_preempt_wakeup
,
8595 .pick_next_task
= pick_next_task_fair
,
8596 .put_prev_task
= put_prev_task_fair
,
8599 .select_task_rq
= select_task_rq_fair
,
8600 .migrate_task_rq
= migrate_task_rq_fair
,
8602 .rq_online
= rq_online_fair
,
8603 .rq_offline
= rq_offline_fair
,
8605 .task_waking
= task_waking_fair
,
8606 .task_dead
= task_dead_fair
,
8607 .set_cpus_allowed
= set_cpus_allowed_common
,
8610 .set_curr_task
= set_curr_task_fair
,
8611 .task_tick
= task_tick_fair
,
8612 .task_fork
= task_fork_fair
,
8614 .prio_changed
= prio_changed_fair
,
8615 .switched_from
= switched_from_fair
,
8616 .switched_to
= switched_to_fair
,
8618 .get_rr_interval
= get_rr_interval_fair
,
8620 .update_curr
= update_curr_fair
,
8622 #ifdef CONFIG_FAIR_GROUP_SCHED
8623 .task_move_group
= task_move_group_fair
,
8627 #ifdef CONFIG_SCHED_DEBUG
8628 void print_cfs_stats(struct seq_file
*m
, int cpu
)
8630 struct cfs_rq
*cfs_rq
;
8633 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
8634 print_cfs_rq(m
, cpu
, cfs_rq
);
8638 #ifdef CONFIG_NUMA_BALANCING
8639 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
8642 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
8644 for_each_online_node(node
) {
8645 if (p
->numa_faults
) {
8646 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
8647 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8649 if (p
->numa_group
) {
8650 gsf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
8651 gpf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8653 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
8656 #endif /* CONFIG_NUMA_BALANCING */
8657 #endif /* CONFIG_SCHED_DEBUG */
8659 __init
void init_sched_fair_class(void)
8662 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
8664 #ifdef CONFIG_NO_HZ_COMMON
8665 nohz
.next_balance
= jiffies
;
8666 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);
8667 cpu_notifier(sched_ilb_notifier
, 0);