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;
118 * The margin used when comparing utilization with CPU capacity:
119 * util * 1024 < capacity * margin
121 unsigned int capacity_margin
= 1280; /* ~20% */
123 static inline void update_load_add(struct load_weight
*lw
, unsigned long inc
)
129 static inline void update_load_sub(struct load_weight
*lw
, unsigned long dec
)
135 static inline void update_load_set(struct load_weight
*lw
, unsigned long w
)
142 * Increase the granularity value when there are more CPUs,
143 * because with more CPUs the 'effective latency' as visible
144 * to users decreases. But the relationship is not linear,
145 * so pick a second-best guess by going with the log2 of the
148 * This idea comes from the SD scheduler of Con Kolivas:
150 static unsigned int get_update_sysctl_factor(void)
152 unsigned int cpus
= min_t(unsigned int, num_online_cpus(), 8);
155 switch (sysctl_sched_tunable_scaling
) {
156 case SCHED_TUNABLESCALING_NONE
:
159 case SCHED_TUNABLESCALING_LINEAR
:
162 case SCHED_TUNABLESCALING_LOG
:
164 factor
= 1 + ilog2(cpus
);
171 static void update_sysctl(void)
173 unsigned int factor
= get_update_sysctl_factor();
175 #define SET_SYSCTL(name) \
176 (sysctl_##name = (factor) * normalized_sysctl_##name)
177 SET_SYSCTL(sched_min_granularity
);
178 SET_SYSCTL(sched_latency
);
179 SET_SYSCTL(sched_wakeup_granularity
);
183 void sched_init_granularity(void)
188 #define WMULT_CONST (~0U)
189 #define WMULT_SHIFT 32
191 static void __update_inv_weight(struct load_weight
*lw
)
195 if (likely(lw
->inv_weight
))
198 w
= scale_load_down(lw
->weight
);
200 if (BITS_PER_LONG
> 32 && unlikely(w
>= WMULT_CONST
))
202 else if (unlikely(!w
))
203 lw
->inv_weight
= WMULT_CONST
;
205 lw
->inv_weight
= WMULT_CONST
/ w
;
209 * delta_exec * weight / lw.weight
211 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
213 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
214 * we're guaranteed shift stays positive because inv_weight is guaranteed to
215 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
217 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
218 * weight/lw.weight <= 1, and therefore our shift will also be positive.
220 static u64
__calc_delta(u64 delta_exec
, unsigned long weight
, struct load_weight
*lw
)
222 u64 fact
= scale_load_down(weight
);
223 int shift
= WMULT_SHIFT
;
225 __update_inv_weight(lw
);
227 if (unlikely(fact
>> 32)) {
234 /* hint to use a 32x32->64 mul */
235 fact
= (u64
)(u32
)fact
* lw
->inv_weight
;
242 return mul_u64_u32_shr(delta_exec
, fact
, shift
);
246 const struct sched_class fair_sched_class
;
248 /**************************************************************
249 * CFS operations on generic schedulable entities:
252 #ifdef CONFIG_FAIR_GROUP_SCHED
254 /* cpu runqueue to which this cfs_rq is attached */
255 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
260 /* An entity is a task if it doesn't "own" a runqueue */
261 #define entity_is_task(se) (!se->my_q)
263 static inline struct task_struct
*task_of(struct sched_entity
*se
)
265 #ifdef CONFIG_SCHED_DEBUG
266 WARN_ON_ONCE(!entity_is_task(se
));
268 return container_of(se
, struct task_struct
, se
);
271 /* Walk up scheduling entities hierarchy */
272 #define for_each_sched_entity(se) \
273 for (; se; se = se->parent)
275 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
280 /* runqueue on which this entity is (to be) queued */
281 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
286 /* runqueue "owned" by this group */
287 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
292 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
294 if (!cfs_rq
->on_list
) {
296 * Ensure we either appear before our parent (if already
297 * enqueued) or force our parent to appear after us when it is
298 * enqueued. The fact that we always enqueue bottom-up
299 * reduces this to two cases.
301 if (cfs_rq
->tg
->parent
&&
302 cfs_rq
->tg
->parent
->cfs_rq
[cpu_of(rq_of(cfs_rq
))]->on_list
) {
303 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
304 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
306 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
307 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
314 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
316 if (cfs_rq
->on_list
) {
317 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
322 /* Iterate thr' all leaf cfs_rq's on a runqueue */
323 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
324 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
326 /* Do the two (enqueued) entities belong to the same group ? */
327 static inline struct cfs_rq
*
328 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
330 if (se
->cfs_rq
== pse
->cfs_rq
)
336 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
342 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
344 int se_depth
, pse_depth
;
347 * preemption test can be made between sibling entities who are in the
348 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
349 * both tasks until we find their ancestors who are siblings of common
353 /* First walk up until both entities are at same depth */
354 se_depth
= (*se
)->depth
;
355 pse_depth
= (*pse
)->depth
;
357 while (se_depth
> pse_depth
) {
359 *se
= parent_entity(*se
);
362 while (pse_depth
> se_depth
) {
364 *pse
= parent_entity(*pse
);
367 while (!is_same_group(*se
, *pse
)) {
368 *se
= parent_entity(*se
);
369 *pse
= parent_entity(*pse
);
373 #else /* !CONFIG_FAIR_GROUP_SCHED */
375 static inline struct task_struct
*task_of(struct sched_entity
*se
)
377 return container_of(se
, struct task_struct
, se
);
380 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
382 return container_of(cfs_rq
, struct rq
, cfs
);
385 #define entity_is_task(se) 1
387 #define for_each_sched_entity(se) \
388 for (; se; se = NULL)
390 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
392 return &task_rq(p
)->cfs
;
395 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
397 struct task_struct
*p
= task_of(se
);
398 struct rq
*rq
= task_rq(p
);
403 /* runqueue "owned" by this group */
404 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
409 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
413 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
417 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
418 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
420 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
426 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
430 #endif /* CONFIG_FAIR_GROUP_SCHED */
432 static __always_inline
433 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
);
435 /**************************************************************
436 * Scheduling class tree data structure manipulation methods:
439 static inline u64
max_vruntime(u64 max_vruntime
, u64 vruntime
)
441 s64 delta
= (s64
)(vruntime
- max_vruntime
);
443 max_vruntime
= vruntime
;
448 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
450 s64 delta
= (s64
)(vruntime
- min_vruntime
);
452 min_vruntime
= vruntime
;
457 static inline int entity_before(struct sched_entity
*a
,
458 struct sched_entity
*b
)
460 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
463 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
465 u64 vruntime
= cfs_rq
->min_vruntime
;
468 vruntime
= cfs_rq
->curr
->vruntime
;
470 if (cfs_rq
->rb_leftmost
) {
471 struct sched_entity
*se
= rb_entry(cfs_rq
->rb_leftmost
,
476 vruntime
= se
->vruntime
;
478 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
481 /* ensure we never gain time by being placed backwards. */
482 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
485 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
490 * Enqueue an entity into the rb-tree:
492 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
494 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
495 struct rb_node
*parent
= NULL
;
496 struct sched_entity
*entry
;
500 * Find the right place in the rbtree:
504 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
506 * We dont care about collisions. Nodes with
507 * the same key stay together.
509 if (entity_before(se
, entry
)) {
510 link
= &parent
->rb_left
;
512 link
= &parent
->rb_right
;
518 * Maintain a cache of leftmost tree entries (it is frequently
522 cfs_rq
->rb_leftmost
= &se
->run_node
;
524 rb_link_node(&se
->run_node
, parent
, link
);
525 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
528 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
530 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
531 struct rb_node
*next_node
;
533 next_node
= rb_next(&se
->run_node
);
534 cfs_rq
->rb_leftmost
= next_node
;
537 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
540 struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
542 struct rb_node
*left
= cfs_rq
->rb_leftmost
;
547 return rb_entry(left
, struct sched_entity
, run_node
);
550 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
552 struct rb_node
*next
= rb_next(&se
->run_node
);
557 return rb_entry(next
, struct sched_entity
, run_node
);
560 #ifdef CONFIG_SCHED_DEBUG
561 struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
563 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
568 return rb_entry(last
, struct sched_entity
, run_node
);
571 /**************************************************************
572 * Scheduling class statistics methods:
575 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
576 void __user
*buffer
, size_t *lenp
,
579 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
580 unsigned int factor
= get_update_sysctl_factor();
585 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
586 sysctl_sched_min_granularity
);
588 #define WRT_SYSCTL(name) \
589 (normalized_sysctl_##name = sysctl_##name / (factor))
590 WRT_SYSCTL(sched_min_granularity
);
591 WRT_SYSCTL(sched_latency
);
592 WRT_SYSCTL(sched_wakeup_granularity
);
602 static inline u64
calc_delta_fair(u64 delta
, struct sched_entity
*se
)
604 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
605 delta
= __calc_delta(delta
, NICE_0_LOAD
, &se
->load
);
611 * The idea is to set a period in which each task runs once.
613 * When there are too many tasks (sched_nr_latency) we have to stretch
614 * this period because otherwise the slices get too small.
616 * p = (nr <= nl) ? l : l*nr/nl
618 static u64
__sched_period(unsigned long nr_running
)
620 if (unlikely(nr_running
> sched_nr_latency
))
621 return nr_running
* sysctl_sched_min_granularity
;
623 return sysctl_sched_latency
;
627 * We calculate the wall-time slice from the period by taking a part
628 * proportional to the weight.
632 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
634 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
636 for_each_sched_entity(se
) {
637 struct load_weight
*load
;
638 struct load_weight lw
;
640 cfs_rq
= cfs_rq_of(se
);
641 load
= &cfs_rq
->load
;
643 if (unlikely(!se
->on_rq
)) {
646 update_load_add(&lw
, se
->load
.weight
);
649 slice
= __calc_delta(slice
, se
->load
.weight
, load
);
655 * We calculate the vruntime slice of a to-be-inserted task.
659 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
661 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
665 static int select_idle_sibling(struct task_struct
*p
, int prev_cpu
, int cpu
);
666 static unsigned long task_h_load(struct task_struct
*p
);
669 * We choose a half-life close to 1 scheduling period.
670 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
671 * dependent on this value.
673 #define LOAD_AVG_PERIOD 32
674 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
675 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
677 /* Give new sched_entity start runnable values to heavy its load in infant time */
678 void init_entity_runnable_average(struct sched_entity
*se
)
680 struct sched_avg
*sa
= &se
->avg
;
682 sa
->last_update_time
= 0;
684 * sched_avg's period_contrib should be strictly less then 1024, so
685 * we give it 1023 to make sure it is almost a period (1024us), and
686 * will definitely be update (after enqueue).
688 sa
->period_contrib
= 1023;
689 sa
->load_avg
= scale_load_down(se
->load
.weight
);
690 sa
->load_sum
= sa
->load_avg
* LOAD_AVG_MAX
;
692 * At this point, util_avg won't be used in select_task_rq_fair anyway
696 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
699 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
);
700 static int update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
);
701 static void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
);
702 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
);
705 * With new tasks being created, their initial util_avgs are extrapolated
706 * based on the cfs_rq's current util_avg:
708 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
710 * However, in many cases, the above util_avg does not give a desired
711 * value. Moreover, the sum of the util_avgs may be divergent, such
712 * as when the series is a harmonic series.
714 * To solve this problem, we also cap the util_avg of successive tasks to
715 * only 1/2 of the left utilization budget:
717 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
719 * where n denotes the nth task.
721 * For example, a simplest series from the beginning would be like:
723 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ...
724 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
726 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
727 * if util_avg > util_avg_cap.
729 void post_init_entity_util_avg(struct sched_entity
*se
)
731 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
732 struct sched_avg
*sa
= &se
->avg
;
733 long cap
= (long)(SCHED_CAPACITY_SCALE
- cfs_rq
->avg
.util_avg
) / 2;
734 u64 now
= cfs_rq_clock_task(cfs_rq
);
737 if (cfs_rq
->avg
.util_avg
!= 0) {
738 sa
->util_avg
= cfs_rq
->avg
.util_avg
* se
->load
.weight
;
739 sa
->util_avg
/= (cfs_rq
->avg
.load_avg
+ 1);
741 if (sa
->util_avg
> cap
)
746 sa
->util_sum
= sa
->util_avg
* LOAD_AVG_MAX
;
749 if (entity_is_task(se
)) {
750 struct task_struct
*p
= task_of(se
);
751 if (p
->sched_class
!= &fair_sched_class
) {
753 * For !fair tasks do:
755 update_cfs_rq_load_avg(now, cfs_rq, false);
756 attach_entity_load_avg(cfs_rq, se);
757 switched_from_fair(rq, p);
759 * such that the next switched_to_fair() has the
762 se
->avg
.last_update_time
= now
;
767 update_cfs_rq_load_avg(now
, cfs_rq
, false);
768 attach_entity_load_avg(cfs_rq
, se
);
769 update_tg_load_avg(cfs_rq
, false);
772 #else /* !CONFIG_SMP */
773 void init_entity_runnable_average(struct sched_entity
*se
)
776 void post_init_entity_util_avg(struct sched_entity
*se
)
779 static void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
782 #endif /* CONFIG_SMP */
785 * Update the current task's runtime statistics.
787 static void update_curr(struct cfs_rq
*cfs_rq
)
789 struct sched_entity
*curr
= cfs_rq
->curr
;
790 u64 now
= rq_clock_task(rq_of(cfs_rq
));
796 delta_exec
= now
- curr
->exec_start
;
797 if (unlikely((s64
)delta_exec
<= 0))
800 curr
->exec_start
= now
;
802 schedstat_set(curr
->statistics
.exec_max
,
803 max(delta_exec
, curr
->statistics
.exec_max
));
805 curr
->sum_exec_runtime
+= delta_exec
;
806 schedstat_add(cfs_rq
->exec_clock
, delta_exec
);
808 curr
->vruntime
+= calc_delta_fair(delta_exec
, curr
);
809 update_min_vruntime(cfs_rq
);
811 if (entity_is_task(curr
)) {
812 struct task_struct
*curtask
= task_of(curr
);
814 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
815 cpuacct_charge(curtask
, delta_exec
);
816 account_group_exec_runtime(curtask
, delta_exec
);
819 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
822 static void update_curr_fair(struct rq
*rq
)
824 update_curr(cfs_rq_of(&rq
->curr
->se
));
828 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
830 u64 wait_start
, prev_wait_start
;
832 if (!schedstat_enabled())
835 wait_start
= rq_clock(rq_of(cfs_rq
));
836 prev_wait_start
= schedstat_val(se
->statistics
.wait_start
);
838 if (entity_is_task(se
) && task_on_rq_migrating(task_of(se
)) &&
839 likely(wait_start
> prev_wait_start
))
840 wait_start
-= prev_wait_start
;
842 schedstat_set(se
->statistics
.wait_start
, wait_start
);
846 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
848 struct task_struct
*p
;
851 if (!schedstat_enabled())
854 delta
= rq_clock(rq_of(cfs_rq
)) - schedstat_val(se
->statistics
.wait_start
);
856 if (entity_is_task(se
)) {
858 if (task_on_rq_migrating(p
)) {
860 * Preserve migrating task's wait time so wait_start
861 * time stamp can be adjusted to accumulate wait time
862 * prior to migration.
864 schedstat_set(se
->statistics
.wait_start
, delta
);
867 trace_sched_stat_wait(p
, delta
);
870 schedstat_set(se
->statistics
.wait_max
,
871 max(schedstat_val(se
->statistics
.wait_max
), delta
));
872 schedstat_inc(se
->statistics
.wait_count
);
873 schedstat_add(se
->statistics
.wait_sum
, delta
);
874 schedstat_set(se
->statistics
.wait_start
, 0);
878 update_stats_enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
880 struct task_struct
*tsk
= NULL
;
881 u64 sleep_start
, block_start
;
883 if (!schedstat_enabled())
886 sleep_start
= schedstat_val(se
->statistics
.sleep_start
);
887 block_start
= schedstat_val(se
->statistics
.block_start
);
889 if (entity_is_task(se
))
893 u64 delta
= rq_clock(rq_of(cfs_rq
)) - sleep_start
;
898 if (unlikely(delta
> schedstat_val(se
->statistics
.sleep_max
)))
899 schedstat_set(se
->statistics
.sleep_max
, delta
);
901 schedstat_set(se
->statistics
.sleep_start
, 0);
902 schedstat_add(se
->statistics
.sum_sleep_runtime
, delta
);
905 account_scheduler_latency(tsk
, delta
>> 10, 1);
906 trace_sched_stat_sleep(tsk
, delta
);
910 u64 delta
= rq_clock(rq_of(cfs_rq
)) - block_start
;
915 if (unlikely(delta
> schedstat_val(se
->statistics
.block_max
)))
916 schedstat_set(se
->statistics
.block_max
, delta
);
918 schedstat_set(se
->statistics
.block_start
, 0);
919 schedstat_add(se
->statistics
.sum_sleep_runtime
, delta
);
922 if (tsk
->in_iowait
) {
923 schedstat_add(se
->statistics
.iowait_sum
, delta
);
924 schedstat_inc(se
->statistics
.iowait_count
);
925 trace_sched_stat_iowait(tsk
, delta
);
928 trace_sched_stat_blocked(tsk
, delta
);
931 * Blocking time is in units of nanosecs, so shift by
932 * 20 to get a milliseconds-range estimation of the
933 * amount of time that the task spent sleeping:
935 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
936 profile_hits(SLEEP_PROFILING
,
937 (void *)get_wchan(tsk
),
940 account_scheduler_latency(tsk
, delta
>> 10, 0);
946 * Task is being enqueued - update stats:
949 update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
951 if (!schedstat_enabled())
955 * Are we enqueueing a waiting task? (for current tasks
956 * a dequeue/enqueue event is a NOP)
958 if (se
!= cfs_rq
->curr
)
959 update_stats_wait_start(cfs_rq
, se
);
961 if (flags
& ENQUEUE_WAKEUP
)
962 update_stats_enqueue_sleeper(cfs_rq
, se
);
966 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
969 if (!schedstat_enabled())
973 * Mark the end of the wait period if dequeueing a
976 if (se
!= cfs_rq
->curr
)
977 update_stats_wait_end(cfs_rq
, se
);
979 if ((flags
& DEQUEUE_SLEEP
) && entity_is_task(se
)) {
980 struct task_struct
*tsk
= task_of(se
);
982 if (tsk
->state
& TASK_INTERRUPTIBLE
)
983 schedstat_set(se
->statistics
.sleep_start
,
984 rq_clock(rq_of(cfs_rq
)));
985 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
986 schedstat_set(se
->statistics
.block_start
,
987 rq_clock(rq_of(cfs_rq
)));
992 * We are picking a new current task - update its stats:
995 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
998 * We are starting a new run period:
1000 se
->exec_start
= rq_clock_task(rq_of(cfs_rq
));
1003 /**************************************************
1004 * Scheduling class queueing methods:
1007 #ifdef CONFIG_NUMA_BALANCING
1009 * Approximate time to scan a full NUMA task in ms. The task scan period is
1010 * calculated based on the tasks virtual memory size and
1011 * numa_balancing_scan_size.
1013 unsigned int sysctl_numa_balancing_scan_period_min
= 1000;
1014 unsigned int sysctl_numa_balancing_scan_period_max
= 60000;
1016 /* Portion of address space to scan in MB */
1017 unsigned int sysctl_numa_balancing_scan_size
= 256;
1019 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
1020 unsigned int sysctl_numa_balancing_scan_delay
= 1000;
1022 static unsigned int task_nr_scan_windows(struct task_struct
*p
)
1024 unsigned long rss
= 0;
1025 unsigned long nr_scan_pages
;
1028 * Calculations based on RSS as non-present and empty pages are skipped
1029 * by the PTE scanner and NUMA hinting faults should be trapped based
1032 nr_scan_pages
= sysctl_numa_balancing_scan_size
<< (20 - PAGE_SHIFT
);
1033 rss
= get_mm_rss(p
->mm
);
1035 rss
= nr_scan_pages
;
1037 rss
= round_up(rss
, nr_scan_pages
);
1038 return rss
/ nr_scan_pages
;
1041 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
1042 #define MAX_SCAN_WINDOW 2560
1044 static unsigned int task_scan_min(struct task_struct
*p
)
1046 unsigned int scan_size
= READ_ONCE(sysctl_numa_balancing_scan_size
);
1047 unsigned int scan
, floor
;
1048 unsigned int windows
= 1;
1050 if (scan_size
< MAX_SCAN_WINDOW
)
1051 windows
= MAX_SCAN_WINDOW
/ scan_size
;
1052 floor
= 1000 / windows
;
1054 scan
= sysctl_numa_balancing_scan_period_min
/ task_nr_scan_windows(p
);
1055 return max_t(unsigned int, floor
, scan
);
1058 static unsigned int task_scan_max(struct task_struct
*p
)
1060 unsigned int smin
= task_scan_min(p
);
1063 /* Watch for min being lower than max due to floor calculations */
1064 smax
= sysctl_numa_balancing_scan_period_max
/ task_nr_scan_windows(p
);
1065 return max(smin
, smax
);
1068 static void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
1070 rq
->nr_numa_running
+= (p
->numa_preferred_nid
!= -1);
1071 rq
->nr_preferred_running
+= (p
->numa_preferred_nid
== task_node(p
));
1074 static void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
1076 rq
->nr_numa_running
-= (p
->numa_preferred_nid
!= -1);
1077 rq
->nr_preferred_running
-= (p
->numa_preferred_nid
== task_node(p
));
1083 spinlock_t lock
; /* nr_tasks, tasks */
1088 struct rcu_head rcu
;
1089 unsigned long total_faults
;
1090 unsigned long max_faults_cpu
;
1092 * Faults_cpu is used to decide whether memory should move
1093 * towards the CPU. As a consequence, these stats are weighted
1094 * more by CPU use than by memory faults.
1096 unsigned long *faults_cpu
;
1097 unsigned long faults
[0];
1100 /* Shared or private faults. */
1101 #define NR_NUMA_HINT_FAULT_TYPES 2
1103 /* Memory and CPU locality */
1104 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)
1106 /* Averaged statistics, and temporary buffers. */
1107 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)
1109 pid_t
task_numa_group_id(struct task_struct
*p
)
1111 return p
->numa_group
? p
->numa_group
->gid
: 0;
1115 * The averaged statistics, shared & private, memory & cpu,
1116 * occupy the first half of the array. The second half of the
1117 * array is for current counters, which are averaged into the
1118 * first set by task_numa_placement.
1120 static inline int task_faults_idx(enum numa_faults_stats s
, int nid
, int priv
)
1122 return NR_NUMA_HINT_FAULT_TYPES
* (s
* nr_node_ids
+ nid
) + priv
;
1125 static inline unsigned long task_faults(struct task_struct
*p
, int nid
)
1127 if (!p
->numa_faults
)
1130 return p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1131 p
->numa_faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1134 static inline unsigned long group_faults(struct task_struct
*p
, int nid
)
1139 return p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1140 p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1143 static inline unsigned long group_faults_cpu(struct numa_group
*group
, int nid
)
1145 return group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 0)] +
1146 group
->faults_cpu
[task_faults_idx(NUMA_MEM
, nid
, 1)];
1150 * A node triggering more than 1/3 as many NUMA faults as the maximum is
1151 * considered part of a numa group's pseudo-interleaving set. Migrations
1152 * between these nodes are slowed down, to allow things to settle down.
1154 #define ACTIVE_NODE_FRACTION 3
1156 static bool numa_is_active_node(int nid
, struct numa_group
*ng
)
1158 return group_faults_cpu(ng
, nid
) * ACTIVE_NODE_FRACTION
> ng
->max_faults_cpu
;
1161 /* Handle placement on systems where not all nodes are directly connected. */
1162 static unsigned long score_nearby_nodes(struct task_struct
*p
, int nid
,
1163 int maxdist
, bool task
)
1165 unsigned long score
= 0;
1169 * All nodes are directly connected, and the same distance
1170 * from each other. No need for fancy placement algorithms.
1172 if (sched_numa_topology_type
== NUMA_DIRECT
)
1176 * This code is called for each node, introducing N^2 complexity,
1177 * which should be ok given the number of nodes rarely exceeds 8.
1179 for_each_online_node(node
) {
1180 unsigned long faults
;
1181 int dist
= node_distance(nid
, node
);
1184 * The furthest away nodes in the system are not interesting
1185 * for placement; nid was already counted.
1187 if (dist
== sched_max_numa_distance
|| node
== nid
)
1191 * On systems with a backplane NUMA topology, compare groups
1192 * of nodes, and move tasks towards the group with the most
1193 * memory accesses. When comparing two nodes at distance
1194 * "hoplimit", only nodes closer by than "hoplimit" are part
1195 * of each group. Skip other nodes.
1197 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1201 /* Add up the faults from nearby nodes. */
1203 faults
= task_faults(p
, node
);
1205 faults
= group_faults(p
, node
);
1208 * On systems with a glueless mesh NUMA topology, there are
1209 * no fixed "groups of nodes". Instead, nodes that are not
1210 * directly connected bounce traffic through intermediate
1211 * nodes; a numa_group can occupy any set of nodes.
1212 * The further away a node is, the less the faults count.
1213 * This seems to result in good task placement.
1215 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1216 faults
*= (sched_max_numa_distance
- dist
);
1217 faults
/= (sched_max_numa_distance
- LOCAL_DISTANCE
);
1227 * These return the fraction of accesses done by a particular task, or
1228 * task group, on a particular numa node. The group weight is given a
1229 * larger multiplier, in order to group tasks together that are almost
1230 * evenly spread out between numa nodes.
1232 static inline unsigned long task_weight(struct task_struct
*p
, int nid
,
1235 unsigned long faults
, total_faults
;
1237 if (!p
->numa_faults
)
1240 total_faults
= p
->total_numa_faults
;
1245 faults
= task_faults(p
, nid
);
1246 faults
+= score_nearby_nodes(p
, nid
, dist
, true);
1248 return 1000 * faults
/ total_faults
;
1251 static inline unsigned long group_weight(struct task_struct
*p
, int nid
,
1254 unsigned long faults
, total_faults
;
1259 total_faults
= p
->numa_group
->total_faults
;
1264 faults
= group_faults(p
, nid
);
1265 faults
+= score_nearby_nodes(p
, nid
, dist
, false);
1267 return 1000 * faults
/ total_faults
;
1270 bool should_numa_migrate_memory(struct task_struct
*p
, struct page
* page
,
1271 int src_nid
, int dst_cpu
)
1273 struct numa_group
*ng
= p
->numa_group
;
1274 int dst_nid
= cpu_to_node(dst_cpu
);
1275 int last_cpupid
, this_cpupid
;
1277 this_cpupid
= cpu_pid_to_cpupid(dst_cpu
, current
->pid
);
1280 * Multi-stage node selection is used in conjunction with a periodic
1281 * migration fault to build a temporal task<->page relation. By using
1282 * a two-stage filter we remove short/unlikely relations.
1284 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
1285 * a task's usage of a particular page (n_p) per total usage of this
1286 * page (n_t) (in a given time-span) to a probability.
1288 * Our periodic faults will sample this probability and getting the
1289 * same result twice in a row, given these samples are fully
1290 * independent, is then given by P(n)^2, provided our sample period
1291 * is sufficiently short compared to the usage pattern.
1293 * This quadric squishes small probabilities, making it less likely we
1294 * act on an unlikely task<->page relation.
1296 last_cpupid
= page_cpupid_xchg_last(page
, this_cpupid
);
1297 if (!cpupid_pid_unset(last_cpupid
) &&
1298 cpupid_to_nid(last_cpupid
) != dst_nid
)
1301 /* Always allow migrate on private faults */
1302 if (cpupid_match_pid(p
, last_cpupid
))
1305 /* A shared fault, but p->numa_group has not been set up yet. */
1310 * Destination node is much more heavily used than the source
1311 * node? Allow migration.
1313 if (group_faults_cpu(ng
, dst_nid
) > group_faults_cpu(ng
, src_nid
) *
1314 ACTIVE_NODE_FRACTION
)
1318 * Distribute memory according to CPU & memory use on each node,
1319 * with 3/4 hysteresis to avoid unnecessary memory migrations:
1321 * faults_cpu(dst) 3 faults_cpu(src)
1322 * --------------- * - > ---------------
1323 * faults_mem(dst) 4 faults_mem(src)
1325 return group_faults_cpu(ng
, dst_nid
) * group_faults(p
, src_nid
) * 3 >
1326 group_faults_cpu(ng
, src_nid
) * group_faults(p
, dst_nid
) * 4;
1329 static unsigned long weighted_cpuload(const int cpu
);
1330 static unsigned long source_load(int cpu
, int type
);
1331 static unsigned long target_load(int cpu
, int type
);
1332 static unsigned long capacity_of(int cpu
);
1333 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
);
1335 /* Cached statistics for all CPUs within a node */
1337 unsigned long nr_running
;
1340 /* Total compute capacity of CPUs on a node */
1341 unsigned long compute_capacity
;
1343 /* Approximate capacity in terms of runnable tasks on a node */
1344 unsigned long task_capacity
;
1345 int has_free_capacity
;
1349 * XXX borrowed from update_sg_lb_stats
1351 static void update_numa_stats(struct numa_stats
*ns
, int nid
)
1353 int smt
, cpu
, cpus
= 0;
1354 unsigned long capacity
;
1356 memset(ns
, 0, sizeof(*ns
));
1357 for_each_cpu(cpu
, cpumask_of_node(nid
)) {
1358 struct rq
*rq
= cpu_rq(cpu
);
1360 ns
->nr_running
+= rq
->nr_running
;
1361 ns
->load
+= weighted_cpuload(cpu
);
1362 ns
->compute_capacity
+= capacity_of(cpu
);
1368 * If we raced with hotplug and there are no CPUs left in our mask
1369 * the @ns structure is NULL'ed and task_numa_compare() will
1370 * not find this node attractive.
1372 * We'll either bail at !has_free_capacity, or we'll detect a huge
1373 * imbalance and bail there.
1378 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
1379 smt
= DIV_ROUND_UP(SCHED_CAPACITY_SCALE
* cpus
, ns
->compute_capacity
);
1380 capacity
= cpus
/ smt
; /* cores */
1382 ns
->task_capacity
= min_t(unsigned, capacity
,
1383 DIV_ROUND_CLOSEST(ns
->compute_capacity
, SCHED_CAPACITY_SCALE
));
1384 ns
->has_free_capacity
= (ns
->nr_running
< ns
->task_capacity
);
1387 struct task_numa_env
{
1388 struct task_struct
*p
;
1390 int src_cpu
, src_nid
;
1391 int dst_cpu
, dst_nid
;
1393 struct numa_stats src_stats
, dst_stats
;
1398 struct task_struct
*best_task
;
1403 static void task_numa_assign(struct task_numa_env
*env
,
1404 struct task_struct
*p
, long imp
)
1407 put_task_struct(env
->best_task
);
1412 env
->best_imp
= imp
;
1413 env
->best_cpu
= env
->dst_cpu
;
1416 static bool load_too_imbalanced(long src_load
, long dst_load
,
1417 struct task_numa_env
*env
)
1420 long orig_src_load
, orig_dst_load
;
1421 long src_capacity
, dst_capacity
;
1424 * The load is corrected for the CPU capacity available on each node.
1427 * ------------ vs ---------
1428 * src_capacity dst_capacity
1430 src_capacity
= env
->src_stats
.compute_capacity
;
1431 dst_capacity
= env
->dst_stats
.compute_capacity
;
1433 /* We care about the slope of the imbalance, not the direction. */
1434 if (dst_load
< src_load
)
1435 swap(dst_load
, src_load
);
1437 /* Is the difference below the threshold? */
1438 imb
= dst_load
* src_capacity
* 100 -
1439 src_load
* dst_capacity
* env
->imbalance_pct
;
1444 * The imbalance is above the allowed threshold.
1445 * Compare it with the old imbalance.
1447 orig_src_load
= env
->src_stats
.load
;
1448 orig_dst_load
= env
->dst_stats
.load
;
1450 if (orig_dst_load
< orig_src_load
)
1451 swap(orig_dst_load
, orig_src_load
);
1453 old_imb
= orig_dst_load
* src_capacity
* 100 -
1454 orig_src_load
* dst_capacity
* env
->imbalance_pct
;
1456 /* Would this change make things worse? */
1457 return (imb
> old_imb
);
1461 * This checks if the overall compute and NUMA accesses of the system would
1462 * be improved if the source tasks was migrated to the target dst_cpu taking
1463 * into account that it might be best if task running on the dst_cpu should
1464 * be exchanged with the source task
1466 static void task_numa_compare(struct task_numa_env
*env
,
1467 long taskimp
, long groupimp
)
1469 struct rq
*src_rq
= cpu_rq(env
->src_cpu
);
1470 struct rq
*dst_rq
= cpu_rq(env
->dst_cpu
);
1471 struct task_struct
*cur
;
1472 long src_load
, dst_load
;
1474 long imp
= env
->p
->numa_group
? groupimp
: taskimp
;
1476 int dist
= env
->dist
;
1479 cur
= task_rcu_dereference(&dst_rq
->curr
);
1480 if (cur
&& ((cur
->flags
& PF_EXITING
) || is_idle_task(cur
)))
1484 * Because we have preemption enabled we can get migrated around and
1485 * end try selecting ourselves (current == env->p) as a swap candidate.
1491 * "imp" is the fault differential for the source task between the
1492 * source and destination node. Calculate the total differential for
1493 * the source task and potential destination task. The more negative
1494 * the value is, the more rmeote accesses that would be expected to
1495 * be incurred if the tasks were swapped.
1498 /* Skip this swap candidate if cannot move to the source cpu */
1499 if (!cpumask_test_cpu(env
->src_cpu
, tsk_cpus_allowed(cur
)))
1503 * If dst and source tasks are in the same NUMA group, or not
1504 * in any group then look only at task weights.
1506 if (cur
->numa_group
== env
->p
->numa_group
) {
1507 imp
= taskimp
+ task_weight(cur
, env
->src_nid
, dist
) -
1508 task_weight(cur
, env
->dst_nid
, dist
);
1510 * Add some hysteresis to prevent swapping the
1511 * tasks within a group over tiny differences.
1513 if (cur
->numa_group
)
1517 * Compare the group weights. If a task is all by
1518 * itself (not part of a group), use the task weight
1521 if (cur
->numa_group
)
1522 imp
+= group_weight(cur
, env
->src_nid
, dist
) -
1523 group_weight(cur
, env
->dst_nid
, dist
);
1525 imp
+= task_weight(cur
, env
->src_nid
, dist
) -
1526 task_weight(cur
, env
->dst_nid
, dist
);
1530 if (imp
<= env
->best_imp
&& moveimp
<= env
->best_imp
)
1534 /* Is there capacity at our destination? */
1535 if (env
->src_stats
.nr_running
<= env
->src_stats
.task_capacity
&&
1536 !env
->dst_stats
.has_free_capacity
)
1542 /* Balance doesn't matter much if we're running a task per cpu */
1543 if (imp
> env
->best_imp
&& src_rq
->nr_running
== 1 &&
1544 dst_rq
->nr_running
== 1)
1548 * In the overloaded case, try and keep the load balanced.
1551 load
= task_h_load(env
->p
);
1552 dst_load
= env
->dst_stats
.load
+ load
;
1553 src_load
= env
->src_stats
.load
- load
;
1555 if (moveimp
> imp
&& moveimp
> env
->best_imp
) {
1557 * If the improvement from just moving env->p direction is
1558 * better than swapping tasks around, check if a move is
1559 * possible. Store a slightly smaller score than moveimp,
1560 * so an actually idle CPU will win.
1562 if (!load_too_imbalanced(src_load
, dst_load
, env
)) {
1569 if (imp
<= env
->best_imp
)
1573 load
= task_h_load(cur
);
1578 if (load_too_imbalanced(src_load
, dst_load
, env
))
1582 * One idle CPU per node is evaluated for a task numa move.
1583 * Call select_idle_sibling to maybe find a better one.
1586 env
->dst_cpu
= select_idle_sibling(env
->p
, env
->src_cpu
,
1590 task_numa_assign(env
, cur
, imp
);
1595 static void task_numa_find_cpu(struct task_numa_env
*env
,
1596 long taskimp
, long groupimp
)
1600 for_each_cpu(cpu
, cpumask_of_node(env
->dst_nid
)) {
1601 /* Skip this CPU if the source task cannot migrate */
1602 if (!cpumask_test_cpu(cpu
, tsk_cpus_allowed(env
->p
)))
1606 task_numa_compare(env
, taskimp
, groupimp
);
1610 /* Only move tasks to a NUMA node less busy than the current node. */
1611 static bool numa_has_capacity(struct task_numa_env
*env
)
1613 struct numa_stats
*src
= &env
->src_stats
;
1614 struct numa_stats
*dst
= &env
->dst_stats
;
1616 if (src
->has_free_capacity
&& !dst
->has_free_capacity
)
1620 * Only consider a task move if the source has a higher load
1621 * than the destination, corrected for CPU capacity on each node.
1623 * src->load dst->load
1624 * --------------------- vs ---------------------
1625 * src->compute_capacity dst->compute_capacity
1627 if (src
->load
* dst
->compute_capacity
* env
->imbalance_pct
>
1629 dst
->load
* src
->compute_capacity
* 100)
1635 static int task_numa_migrate(struct task_struct
*p
)
1637 struct task_numa_env env
= {
1640 .src_cpu
= task_cpu(p
),
1641 .src_nid
= task_node(p
),
1643 .imbalance_pct
= 112,
1649 struct sched_domain
*sd
;
1650 unsigned long taskweight
, groupweight
;
1652 long taskimp
, groupimp
;
1655 * Pick the lowest SD_NUMA domain, as that would have the smallest
1656 * imbalance and would be the first to start moving tasks about.
1658 * And we want to avoid any moving of tasks about, as that would create
1659 * random movement of tasks -- counter the numa conditions we're trying
1663 sd
= rcu_dereference(per_cpu(sd_numa
, env
.src_cpu
));
1665 env
.imbalance_pct
= 100 + (sd
->imbalance_pct
- 100) / 2;
1669 * Cpusets can break the scheduler domain tree into smaller
1670 * balance domains, some of which do not cross NUMA boundaries.
1671 * Tasks that are "trapped" in such domains cannot be migrated
1672 * elsewhere, so there is no point in (re)trying.
1674 if (unlikely(!sd
)) {
1675 p
->numa_preferred_nid
= task_node(p
);
1679 env
.dst_nid
= p
->numa_preferred_nid
;
1680 dist
= env
.dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1681 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1682 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1683 update_numa_stats(&env
.src_stats
, env
.src_nid
);
1684 taskimp
= task_weight(p
, env
.dst_nid
, dist
) - taskweight
;
1685 groupimp
= group_weight(p
, env
.dst_nid
, dist
) - groupweight
;
1686 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1688 /* Try to find a spot on the preferred nid. */
1689 if (numa_has_capacity(&env
))
1690 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1693 * Look at other nodes in these cases:
1694 * - there is no space available on the preferred_nid
1695 * - the task is part of a numa_group that is interleaved across
1696 * multiple NUMA nodes; in order to better consolidate the group,
1697 * we need to check other locations.
1699 if (env
.best_cpu
== -1 || (p
->numa_group
&& p
->numa_group
->active_nodes
> 1)) {
1700 for_each_online_node(nid
) {
1701 if (nid
== env
.src_nid
|| nid
== p
->numa_preferred_nid
)
1704 dist
= node_distance(env
.src_nid
, env
.dst_nid
);
1705 if (sched_numa_topology_type
== NUMA_BACKPLANE
&&
1707 taskweight
= task_weight(p
, env
.src_nid
, dist
);
1708 groupweight
= group_weight(p
, env
.src_nid
, dist
);
1711 /* Only consider nodes where both task and groups benefit */
1712 taskimp
= task_weight(p
, nid
, dist
) - taskweight
;
1713 groupimp
= group_weight(p
, nid
, dist
) - groupweight
;
1714 if (taskimp
< 0 && groupimp
< 0)
1719 update_numa_stats(&env
.dst_stats
, env
.dst_nid
);
1720 if (numa_has_capacity(&env
))
1721 task_numa_find_cpu(&env
, taskimp
, groupimp
);
1726 * If the task is part of a workload that spans multiple NUMA nodes,
1727 * and is migrating into one of the workload's active nodes, remember
1728 * this node as the task's preferred numa node, so the workload can
1730 * A task that migrated to a second choice node will be better off
1731 * trying for a better one later. Do not set the preferred node here.
1733 if (p
->numa_group
) {
1734 struct numa_group
*ng
= p
->numa_group
;
1736 if (env
.best_cpu
== -1)
1741 if (ng
->active_nodes
> 1 && numa_is_active_node(env
.dst_nid
, ng
))
1742 sched_setnuma(p
, env
.dst_nid
);
1745 /* No better CPU than the current one was found. */
1746 if (env
.best_cpu
== -1)
1750 * Reset the scan period if the task is being rescheduled on an
1751 * alternative node to recheck if the tasks is now properly placed.
1753 p
->numa_scan_period
= task_scan_min(p
);
1755 if (env
.best_task
== NULL
) {
1756 ret
= migrate_task_to(p
, env
.best_cpu
);
1758 trace_sched_stick_numa(p
, env
.src_cpu
, env
.best_cpu
);
1762 ret
= migrate_swap(p
, env
.best_task
);
1764 trace_sched_stick_numa(p
, env
.src_cpu
, task_cpu(env
.best_task
));
1765 put_task_struct(env
.best_task
);
1769 /* Attempt to migrate a task to a CPU on the preferred node. */
1770 static void numa_migrate_preferred(struct task_struct
*p
)
1772 unsigned long interval
= HZ
;
1774 /* This task has no NUMA fault statistics yet */
1775 if (unlikely(p
->numa_preferred_nid
== -1 || !p
->numa_faults
))
1778 /* Periodically retry migrating the task to the preferred node */
1779 interval
= min(interval
, msecs_to_jiffies(p
->numa_scan_period
) / 16);
1780 p
->numa_migrate_retry
= jiffies
+ interval
;
1782 /* Success if task is already running on preferred CPU */
1783 if (task_node(p
) == p
->numa_preferred_nid
)
1786 /* Otherwise, try migrate to a CPU on the preferred node */
1787 task_numa_migrate(p
);
1791 * Find out how many nodes on the workload is actively running on. Do this by
1792 * tracking the nodes from which NUMA hinting faults are triggered. This can
1793 * be different from the set of nodes where the workload's memory is currently
1796 static void numa_group_count_active_nodes(struct numa_group
*numa_group
)
1798 unsigned long faults
, max_faults
= 0;
1799 int nid
, active_nodes
= 0;
1801 for_each_online_node(nid
) {
1802 faults
= group_faults_cpu(numa_group
, nid
);
1803 if (faults
> max_faults
)
1804 max_faults
= faults
;
1807 for_each_online_node(nid
) {
1808 faults
= group_faults_cpu(numa_group
, nid
);
1809 if (faults
* ACTIVE_NODE_FRACTION
> max_faults
)
1813 numa_group
->max_faults_cpu
= max_faults
;
1814 numa_group
->active_nodes
= active_nodes
;
1818 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
1819 * increments. The more local the fault statistics are, the higher the scan
1820 * period will be for the next scan window. If local/(local+remote) ratio is
1821 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
1822 * the scan period will decrease. Aim for 70% local accesses.
1824 #define NUMA_PERIOD_SLOTS 10
1825 #define NUMA_PERIOD_THRESHOLD 7
1828 * Increase the scan period (slow down scanning) if the majority of
1829 * our memory is already on our local node, or if the majority of
1830 * the page accesses are shared with other processes.
1831 * Otherwise, decrease the scan period.
1833 static void update_task_scan_period(struct task_struct
*p
,
1834 unsigned long shared
, unsigned long private)
1836 unsigned int period_slot
;
1840 unsigned long remote
= p
->numa_faults_locality
[0];
1841 unsigned long local
= p
->numa_faults_locality
[1];
1844 * If there were no record hinting faults then either the task is
1845 * completely idle or all activity is areas that are not of interest
1846 * to automatic numa balancing. Related to that, if there were failed
1847 * migration then it implies we are migrating too quickly or the local
1848 * node is overloaded. In either case, scan slower
1850 if (local
+ shared
== 0 || p
->numa_faults_locality
[2]) {
1851 p
->numa_scan_period
= min(p
->numa_scan_period_max
,
1852 p
->numa_scan_period
<< 1);
1854 p
->mm
->numa_next_scan
= jiffies
+
1855 msecs_to_jiffies(p
->numa_scan_period
);
1861 * Prepare to scale scan period relative to the current period.
1862 * == NUMA_PERIOD_THRESHOLD scan period stays the same
1863 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
1864 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
1866 period_slot
= DIV_ROUND_UP(p
->numa_scan_period
, NUMA_PERIOD_SLOTS
);
1867 ratio
= (local
* NUMA_PERIOD_SLOTS
) / (local
+ remote
);
1868 if (ratio
>= NUMA_PERIOD_THRESHOLD
) {
1869 int slot
= ratio
- NUMA_PERIOD_THRESHOLD
;
1872 diff
= slot
* period_slot
;
1874 diff
= -(NUMA_PERIOD_THRESHOLD
- ratio
) * period_slot
;
1877 * Scale scan rate increases based on sharing. There is an
1878 * inverse relationship between the degree of sharing and
1879 * the adjustment made to the scanning period. Broadly
1880 * speaking the intent is that there is little point
1881 * scanning faster if shared accesses dominate as it may
1882 * simply bounce migrations uselessly
1884 ratio
= DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS
, (private + shared
+ 1));
1885 diff
= (diff
* ratio
) / NUMA_PERIOD_SLOTS
;
1888 p
->numa_scan_period
= clamp(p
->numa_scan_period
+ diff
,
1889 task_scan_min(p
), task_scan_max(p
));
1890 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
1894 * Get the fraction of time the task has been running since the last
1895 * NUMA placement cycle. The scheduler keeps similar statistics, but
1896 * decays those on a 32ms period, which is orders of magnitude off
1897 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
1898 * stats only if the task is so new there are no NUMA statistics yet.
1900 static u64
numa_get_avg_runtime(struct task_struct
*p
, u64
*period
)
1902 u64 runtime
, delta
, now
;
1903 /* Use the start of this time slice to avoid calculations. */
1904 now
= p
->se
.exec_start
;
1905 runtime
= p
->se
.sum_exec_runtime
;
1907 if (p
->last_task_numa_placement
) {
1908 delta
= runtime
- p
->last_sum_exec_runtime
;
1909 *period
= now
- p
->last_task_numa_placement
;
1911 delta
= p
->se
.avg
.load_sum
/ p
->se
.load
.weight
;
1912 *period
= LOAD_AVG_MAX
;
1915 p
->last_sum_exec_runtime
= runtime
;
1916 p
->last_task_numa_placement
= now
;
1922 * Determine the preferred nid for a task in a numa_group. This needs to
1923 * be done in a way that produces consistent results with group_weight,
1924 * otherwise workloads might not converge.
1926 static int preferred_group_nid(struct task_struct
*p
, int nid
)
1931 /* Direct connections between all NUMA nodes. */
1932 if (sched_numa_topology_type
== NUMA_DIRECT
)
1936 * On a system with glueless mesh NUMA topology, group_weight
1937 * scores nodes according to the number of NUMA hinting faults on
1938 * both the node itself, and on nearby nodes.
1940 if (sched_numa_topology_type
== NUMA_GLUELESS_MESH
) {
1941 unsigned long score
, max_score
= 0;
1942 int node
, max_node
= nid
;
1944 dist
= sched_max_numa_distance
;
1946 for_each_online_node(node
) {
1947 score
= group_weight(p
, node
, dist
);
1948 if (score
> max_score
) {
1957 * Finding the preferred nid in a system with NUMA backplane
1958 * interconnect topology is more involved. The goal is to locate
1959 * tasks from numa_groups near each other in the system, and
1960 * untangle workloads from different sides of the system. This requires
1961 * searching down the hierarchy of node groups, recursively searching
1962 * inside the highest scoring group of nodes. The nodemask tricks
1963 * keep the complexity of the search down.
1965 nodes
= node_online_map
;
1966 for (dist
= sched_max_numa_distance
; dist
> LOCAL_DISTANCE
; dist
--) {
1967 unsigned long max_faults
= 0;
1968 nodemask_t max_group
= NODE_MASK_NONE
;
1971 /* Are there nodes at this distance from each other? */
1972 if (!find_numa_distance(dist
))
1975 for_each_node_mask(a
, nodes
) {
1976 unsigned long faults
= 0;
1977 nodemask_t this_group
;
1978 nodes_clear(this_group
);
1980 /* Sum group's NUMA faults; includes a==b case. */
1981 for_each_node_mask(b
, nodes
) {
1982 if (node_distance(a
, b
) < dist
) {
1983 faults
+= group_faults(p
, b
);
1984 node_set(b
, this_group
);
1985 node_clear(b
, nodes
);
1989 /* Remember the top group. */
1990 if (faults
> max_faults
) {
1991 max_faults
= faults
;
1992 max_group
= this_group
;
1994 * subtle: at the smallest distance there is
1995 * just one node left in each "group", the
1996 * winner is the preferred nid.
2001 /* Next round, evaluate the nodes within max_group. */
2009 static void task_numa_placement(struct task_struct
*p
)
2011 int seq
, nid
, max_nid
= -1, max_group_nid
= -1;
2012 unsigned long max_faults
= 0, max_group_faults
= 0;
2013 unsigned long fault_types
[2] = { 0, 0 };
2014 unsigned long total_faults
;
2015 u64 runtime
, period
;
2016 spinlock_t
*group_lock
= NULL
;
2019 * The p->mm->numa_scan_seq field gets updated without
2020 * exclusive access. Use READ_ONCE() here to ensure
2021 * that the field is read in a single access:
2023 seq
= READ_ONCE(p
->mm
->numa_scan_seq
);
2024 if (p
->numa_scan_seq
== seq
)
2026 p
->numa_scan_seq
= seq
;
2027 p
->numa_scan_period_max
= task_scan_max(p
);
2029 total_faults
= p
->numa_faults_locality
[0] +
2030 p
->numa_faults_locality
[1];
2031 runtime
= numa_get_avg_runtime(p
, &period
);
2033 /* If the task is part of a group prevent parallel updates to group stats */
2034 if (p
->numa_group
) {
2035 group_lock
= &p
->numa_group
->lock
;
2036 spin_lock_irq(group_lock
);
2039 /* Find the node with the highest number of faults */
2040 for_each_online_node(nid
) {
2041 /* Keep track of the offsets in numa_faults array */
2042 int mem_idx
, membuf_idx
, cpu_idx
, cpubuf_idx
;
2043 unsigned long faults
= 0, group_faults
= 0;
2046 for (priv
= 0; priv
< NR_NUMA_HINT_FAULT_TYPES
; priv
++) {
2047 long diff
, f_diff
, f_weight
;
2049 mem_idx
= task_faults_idx(NUMA_MEM
, nid
, priv
);
2050 membuf_idx
= task_faults_idx(NUMA_MEMBUF
, nid
, priv
);
2051 cpu_idx
= task_faults_idx(NUMA_CPU
, nid
, priv
);
2052 cpubuf_idx
= task_faults_idx(NUMA_CPUBUF
, nid
, priv
);
2054 /* Decay existing window, copy faults since last scan */
2055 diff
= p
->numa_faults
[membuf_idx
] - p
->numa_faults
[mem_idx
] / 2;
2056 fault_types
[priv
] += p
->numa_faults
[membuf_idx
];
2057 p
->numa_faults
[membuf_idx
] = 0;
2060 * Normalize the faults_from, so all tasks in a group
2061 * count according to CPU use, instead of by the raw
2062 * number of faults. Tasks with little runtime have
2063 * little over-all impact on throughput, and thus their
2064 * faults are less important.
2066 f_weight
= div64_u64(runtime
<< 16, period
+ 1);
2067 f_weight
= (f_weight
* p
->numa_faults
[cpubuf_idx
]) /
2069 f_diff
= f_weight
- p
->numa_faults
[cpu_idx
] / 2;
2070 p
->numa_faults
[cpubuf_idx
] = 0;
2072 p
->numa_faults
[mem_idx
] += diff
;
2073 p
->numa_faults
[cpu_idx
] += f_diff
;
2074 faults
+= p
->numa_faults
[mem_idx
];
2075 p
->total_numa_faults
+= diff
;
2076 if (p
->numa_group
) {
2078 * safe because we can only change our own group
2080 * mem_idx represents the offset for a given
2081 * nid and priv in a specific region because it
2082 * is at the beginning of the numa_faults array.
2084 p
->numa_group
->faults
[mem_idx
] += diff
;
2085 p
->numa_group
->faults_cpu
[mem_idx
] += f_diff
;
2086 p
->numa_group
->total_faults
+= diff
;
2087 group_faults
+= p
->numa_group
->faults
[mem_idx
];
2091 if (faults
> max_faults
) {
2092 max_faults
= faults
;
2096 if (group_faults
> max_group_faults
) {
2097 max_group_faults
= group_faults
;
2098 max_group_nid
= nid
;
2102 update_task_scan_period(p
, fault_types
[0], fault_types
[1]);
2104 if (p
->numa_group
) {
2105 numa_group_count_active_nodes(p
->numa_group
);
2106 spin_unlock_irq(group_lock
);
2107 max_nid
= preferred_group_nid(p
, max_group_nid
);
2111 /* Set the new preferred node */
2112 if (max_nid
!= p
->numa_preferred_nid
)
2113 sched_setnuma(p
, max_nid
);
2115 if (task_node(p
) != p
->numa_preferred_nid
)
2116 numa_migrate_preferred(p
);
2120 static inline int get_numa_group(struct numa_group
*grp
)
2122 return atomic_inc_not_zero(&grp
->refcount
);
2125 static inline void put_numa_group(struct numa_group
*grp
)
2127 if (atomic_dec_and_test(&grp
->refcount
))
2128 kfree_rcu(grp
, rcu
);
2131 static void task_numa_group(struct task_struct
*p
, int cpupid
, int flags
,
2134 struct numa_group
*grp
, *my_grp
;
2135 struct task_struct
*tsk
;
2137 int cpu
= cpupid_to_cpu(cpupid
);
2140 if (unlikely(!p
->numa_group
)) {
2141 unsigned int size
= sizeof(struct numa_group
) +
2142 4*nr_node_ids
*sizeof(unsigned long);
2144 grp
= kzalloc(size
, GFP_KERNEL
| __GFP_NOWARN
);
2148 atomic_set(&grp
->refcount
, 1);
2149 grp
->active_nodes
= 1;
2150 grp
->max_faults_cpu
= 0;
2151 spin_lock_init(&grp
->lock
);
2153 /* Second half of the array tracks nids where faults happen */
2154 grp
->faults_cpu
= grp
->faults
+ NR_NUMA_HINT_FAULT_TYPES
*
2157 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2158 grp
->faults
[i
] = p
->numa_faults
[i
];
2160 grp
->total_faults
= p
->total_numa_faults
;
2163 rcu_assign_pointer(p
->numa_group
, grp
);
2167 tsk
= READ_ONCE(cpu_rq(cpu
)->curr
);
2169 if (!cpupid_match_pid(tsk
, cpupid
))
2172 grp
= rcu_dereference(tsk
->numa_group
);
2176 my_grp
= p
->numa_group
;
2181 * Only join the other group if its bigger; if we're the bigger group,
2182 * the other task will join us.
2184 if (my_grp
->nr_tasks
> grp
->nr_tasks
)
2188 * Tie-break on the grp address.
2190 if (my_grp
->nr_tasks
== grp
->nr_tasks
&& my_grp
> grp
)
2193 /* Always join threads in the same process. */
2194 if (tsk
->mm
== current
->mm
)
2197 /* Simple filter to avoid false positives due to PID collisions */
2198 if (flags
& TNF_SHARED
)
2201 /* Update priv based on whether false sharing was detected */
2204 if (join
&& !get_numa_group(grp
))
2212 BUG_ON(irqs_disabled());
2213 double_lock_irq(&my_grp
->lock
, &grp
->lock
);
2215 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++) {
2216 my_grp
->faults
[i
] -= p
->numa_faults
[i
];
2217 grp
->faults
[i
] += p
->numa_faults
[i
];
2219 my_grp
->total_faults
-= p
->total_numa_faults
;
2220 grp
->total_faults
+= p
->total_numa_faults
;
2225 spin_unlock(&my_grp
->lock
);
2226 spin_unlock_irq(&grp
->lock
);
2228 rcu_assign_pointer(p
->numa_group
, grp
);
2230 put_numa_group(my_grp
);
2238 void task_numa_free(struct task_struct
*p
)
2240 struct numa_group
*grp
= p
->numa_group
;
2241 void *numa_faults
= p
->numa_faults
;
2242 unsigned long flags
;
2246 spin_lock_irqsave(&grp
->lock
, flags
);
2247 for (i
= 0; i
< NR_NUMA_HINT_FAULT_STATS
* nr_node_ids
; i
++)
2248 grp
->faults
[i
] -= p
->numa_faults
[i
];
2249 grp
->total_faults
-= p
->total_numa_faults
;
2252 spin_unlock_irqrestore(&grp
->lock
, flags
);
2253 RCU_INIT_POINTER(p
->numa_group
, NULL
);
2254 put_numa_group(grp
);
2257 p
->numa_faults
= NULL
;
2262 * Got a PROT_NONE fault for a page on @node.
2264 void task_numa_fault(int last_cpupid
, int mem_node
, int pages
, int flags
)
2266 struct task_struct
*p
= current
;
2267 bool migrated
= flags
& TNF_MIGRATED
;
2268 int cpu_node
= task_node(current
);
2269 int local
= !!(flags
& TNF_FAULT_LOCAL
);
2270 struct numa_group
*ng
;
2273 if (!static_branch_likely(&sched_numa_balancing
))
2276 /* for example, ksmd faulting in a user's mm */
2280 /* Allocate buffer to track faults on a per-node basis */
2281 if (unlikely(!p
->numa_faults
)) {
2282 int size
= sizeof(*p
->numa_faults
) *
2283 NR_NUMA_HINT_FAULT_BUCKETS
* nr_node_ids
;
2285 p
->numa_faults
= kzalloc(size
, GFP_KERNEL
|__GFP_NOWARN
);
2286 if (!p
->numa_faults
)
2289 p
->total_numa_faults
= 0;
2290 memset(p
->numa_faults_locality
, 0, sizeof(p
->numa_faults_locality
));
2294 * First accesses are treated as private, otherwise consider accesses
2295 * to be private if the accessing pid has not changed
2297 if (unlikely(last_cpupid
== (-1 & LAST_CPUPID_MASK
))) {
2300 priv
= cpupid_match_pid(p
, last_cpupid
);
2301 if (!priv
&& !(flags
& TNF_NO_GROUP
))
2302 task_numa_group(p
, last_cpupid
, flags
, &priv
);
2306 * If a workload spans multiple NUMA nodes, a shared fault that
2307 * occurs wholly within the set of nodes that the workload is
2308 * actively using should be counted as local. This allows the
2309 * scan rate to slow down when a workload has settled down.
2312 if (!priv
&& !local
&& ng
&& ng
->active_nodes
> 1 &&
2313 numa_is_active_node(cpu_node
, ng
) &&
2314 numa_is_active_node(mem_node
, ng
))
2317 task_numa_placement(p
);
2320 * Retry task to preferred node migration periodically, in case it
2321 * case it previously failed, or the scheduler moved us.
2323 if (time_after(jiffies
, p
->numa_migrate_retry
))
2324 numa_migrate_preferred(p
);
2327 p
->numa_pages_migrated
+= pages
;
2328 if (flags
& TNF_MIGRATE_FAIL
)
2329 p
->numa_faults_locality
[2] += pages
;
2331 p
->numa_faults
[task_faults_idx(NUMA_MEMBUF
, mem_node
, priv
)] += pages
;
2332 p
->numa_faults
[task_faults_idx(NUMA_CPUBUF
, cpu_node
, priv
)] += pages
;
2333 p
->numa_faults_locality
[local
] += pages
;
2336 static void reset_ptenuma_scan(struct task_struct
*p
)
2339 * We only did a read acquisition of the mmap sem, so
2340 * p->mm->numa_scan_seq is written to without exclusive access
2341 * and the update is not guaranteed to be atomic. That's not
2342 * much of an issue though, since this is just used for
2343 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
2344 * expensive, to avoid any form of compiler optimizations:
2346 WRITE_ONCE(p
->mm
->numa_scan_seq
, READ_ONCE(p
->mm
->numa_scan_seq
) + 1);
2347 p
->mm
->numa_scan_offset
= 0;
2351 * The expensive part of numa migration is done from task_work context.
2352 * Triggered from task_tick_numa().
2354 void task_numa_work(struct callback_head
*work
)
2356 unsigned long migrate
, next_scan
, now
= jiffies
;
2357 struct task_struct
*p
= current
;
2358 struct mm_struct
*mm
= p
->mm
;
2359 u64 runtime
= p
->se
.sum_exec_runtime
;
2360 struct vm_area_struct
*vma
;
2361 unsigned long start
, end
;
2362 unsigned long nr_pte_updates
= 0;
2363 long pages
, virtpages
;
2365 WARN_ON_ONCE(p
!= container_of(work
, struct task_struct
, numa_work
));
2367 work
->next
= work
; /* protect against double add */
2369 * Who cares about NUMA placement when they're dying.
2371 * NOTE: make sure not to dereference p->mm before this check,
2372 * exit_task_work() happens _after_ exit_mm() so we could be called
2373 * without p->mm even though we still had it when we enqueued this
2376 if (p
->flags
& PF_EXITING
)
2379 if (!mm
->numa_next_scan
) {
2380 mm
->numa_next_scan
= now
+
2381 msecs_to_jiffies(sysctl_numa_balancing_scan_delay
);
2385 * Enforce maximal scan/migration frequency..
2387 migrate
= mm
->numa_next_scan
;
2388 if (time_before(now
, migrate
))
2391 if (p
->numa_scan_period
== 0) {
2392 p
->numa_scan_period_max
= task_scan_max(p
);
2393 p
->numa_scan_period
= task_scan_min(p
);
2396 next_scan
= now
+ msecs_to_jiffies(p
->numa_scan_period
);
2397 if (cmpxchg(&mm
->numa_next_scan
, migrate
, next_scan
) != migrate
)
2401 * Delay this task enough that another task of this mm will likely win
2402 * the next time around.
2404 p
->node_stamp
+= 2 * TICK_NSEC
;
2406 start
= mm
->numa_scan_offset
;
2407 pages
= sysctl_numa_balancing_scan_size
;
2408 pages
<<= 20 - PAGE_SHIFT
; /* MB in pages */
2409 virtpages
= pages
* 8; /* Scan up to this much virtual space */
2414 down_read(&mm
->mmap_sem
);
2415 vma
= find_vma(mm
, start
);
2417 reset_ptenuma_scan(p
);
2421 for (; vma
; vma
= vma
->vm_next
) {
2422 if (!vma_migratable(vma
) || !vma_policy_mof(vma
) ||
2423 is_vm_hugetlb_page(vma
) || (vma
->vm_flags
& VM_MIXEDMAP
)) {
2428 * Shared library pages mapped by multiple processes are not
2429 * migrated as it is expected they are cache replicated. Avoid
2430 * hinting faults in read-only file-backed mappings or the vdso
2431 * as migrating the pages will be of marginal benefit.
2434 (vma
->vm_file
&& (vma
->vm_flags
& (VM_READ
|VM_WRITE
)) == (VM_READ
)))
2438 * Skip inaccessible VMAs to avoid any confusion between
2439 * PROT_NONE and NUMA hinting ptes
2441 if (!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
)))
2445 start
= max(start
, vma
->vm_start
);
2446 end
= ALIGN(start
+ (pages
<< PAGE_SHIFT
), HPAGE_SIZE
);
2447 end
= min(end
, vma
->vm_end
);
2448 nr_pte_updates
= change_prot_numa(vma
, start
, end
);
2451 * Try to scan sysctl_numa_balancing_size worth of
2452 * hpages that have at least one present PTE that
2453 * is not already pte-numa. If the VMA contains
2454 * areas that are unused or already full of prot_numa
2455 * PTEs, scan up to virtpages, to skip through those
2459 pages
-= (end
- start
) >> PAGE_SHIFT
;
2460 virtpages
-= (end
- start
) >> PAGE_SHIFT
;
2463 if (pages
<= 0 || virtpages
<= 0)
2467 } while (end
!= vma
->vm_end
);
2472 * It is possible to reach the end of the VMA list but the last few
2473 * VMAs are not guaranteed to the vma_migratable. If they are not, we
2474 * would find the !migratable VMA on the next scan but not reset the
2475 * scanner to the start so check it now.
2478 mm
->numa_scan_offset
= start
;
2480 reset_ptenuma_scan(p
);
2481 up_read(&mm
->mmap_sem
);
2484 * Make sure tasks use at least 32x as much time to run other code
2485 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
2486 * Usually update_task_scan_period slows down scanning enough; on an
2487 * overloaded system we need to limit overhead on a per task basis.
2489 if (unlikely(p
->se
.sum_exec_runtime
!= runtime
)) {
2490 u64 diff
= p
->se
.sum_exec_runtime
- runtime
;
2491 p
->node_stamp
+= 32 * diff
;
2496 * Drive the periodic memory faults..
2498 void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2500 struct callback_head
*work
= &curr
->numa_work
;
2504 * We don't care about NUMA placement if we don't have memory.
2506 if (!curr
->mm
|| (curr
->flags
& PF_EXITING
) || work
->next
!= work
)
2510 * Using runtime rather than walltime has the dual advantage that
2511 * we (mostly) drive the selection from busy threads and that the
2512 * task needs to have done some actual work before we bother with
2515 now
= curr
->se
.sum_exec_runtime
;
2516 period
= (u64
)curr
->numa_scan_period
* NSEC_PER_MSEC
;
2518 if (now
> curr
->node_stamp
+ period
) {
2519 if (!curr
->node_stamp
)
2520 curr
->numa_scan_period
= task_scan_min(curr
);
2521 curr
->node_stamp
+= period
;
2523 if (!time_before(jiffies
, curr
->mm
->numa_next_scan
)) {
2524 init_task_work(work
, task_numa_work
); /* TODO: move this into sched_fork() */
2525 task_work_add(curr
, work
, true);
2530 static void task_tick_numa(struct rq
*rq
, struct task_struct
*curr
)
2534 static inline void account_numa_enqueue(struct rq
*rq
, struct task_struct
*p
)
2538 static inline void account_numa_dequeue(struct rq
*rq
, struct task_struct
*p
)
2541 #endif /* CONFIG_NUMA_BALANCING */
2544 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2546 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
2547 if (!parent_entity(se
))
2548 update_load_add(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2550 if (entity_is_task(se
)) {
2551 struct rq
*rq
= rq_of(cfs_rq
);
2553 account_numa_enqueue(rq
, task_of(se
));
2554 list_add(&se
->group_node
, &rq
->cfs_tasks
);
2557 cfs_rq
->nr_running
++;
2561 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
2563 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
2564 if (!parent_entity(se
))
2565 update_load_sub(&rq_of(cfs_rq
)->load
, se
->load
.weight
);
2567 if (entity_is_task(se
)) {
2568 account_numa_dequeue(rq_of(cfs_rq
), task_of(se
));
2569 list_del_init(&se
->group_node
);
2572 cfs_rq
->nr_running
--;
2575 #ifdef CONFIG_FAIR_GROUP_SCHED
2577 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2579 long tg_weight
, load
, shares
;
2582 * This really should be: cfs_rq->avg.load_avg, but instead we use
2583 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
2584 * the shares for small weight interactive tasks.
2586 load
= scale_load_down(cfs_rq
->load
.weight
);
2588 tg_weight
= atomic_long_read(&tg
->load_avg
);
2590 /* Ensure tg_weight >= load */
2591 tg_weight
-= cfs_rq
->tg_load_avg_contrib
;
2594 shares
= (tg
->shares
* load
);
2596 shares
/= tg_weight
;
2598 if (shares
< MIN_SHARES
)
2599 shares
= MIN_SHARES
;
2600 if (shares
> tg
->shares
)
2601 shares
= tg
->shares
;
2605 # else /* CONFIG_SMP */
2606 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
2610 # endif /* CONFIG_SMP */
2612 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
2613 unsigned long weight
)
2616 /* commit outstanding execution time */
2617 if (cfs_rq
->curr
== se
)
2618 update_curr(cfs_rq
);
2619 account_entity_dequeue(cfs_rq
, se
);
2622 update_load_set(&se
->load
, weight
);
2625 account_entity_enqueue(cfs_rq
, se
);
2628 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
);
2630 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2632 struct task_group
*tg
;
2633 struct sched_entity
*se
;
2637 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
2638 if (!se
|| throttled_hierarchy(cfs_rq
))
2641 if (likely(se
->load
.weight
== tg
->shares
))
2644 shares
= calc_cfs_shares(cfs_rq
, tg
);
2646 reweight_entity(cfs_rq_of(se
), se
, shares
);
2648 #else /* CONFIG_FAIR_GROUP_SCHED */
2649 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
2652 #endif /* CONFIG_FAIR_GROUP_SCHED */
2655 /* Precomputed fixed inverse multiplies for multiplication by y^n */
2656 static const u32 runnable_avg_yN_inv
[] = {
2657 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
2658 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
2659 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
2660 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
2661 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
2662 0x85aac367, 0x82cd8698,
2666 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent
2667 * over-estimates when re-combining.
2669 static const u32 runnable_avg_yN_sum
[] = {
2670 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
2671 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
2672 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
2676 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
2677 * lower integers. See Documentation/scheduler/sched-avg.txt how these
2680 static const u32 __accumulated_sum_N32
[] = {
2681 0, 23371, 35056, 40899, 43820, 45281,
2682 46011, 46376, 46559, 46650, 46696, 46719,
2687 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period)
2689 static __always_inline u64
decay_load(u64 val
, u64 n
)
2691 unsigned int local_n
;
2695 else if (unlikely(n
> LOAD_AVG_PERIOD
* 63))
2698 /* after bounds checking we can collapse to 32-bit */
2702 * As y^PERIOD = 1/2, we can combine
2703 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
2704 * With a look-up table which covers y^n (n<PERIOD)
2706 * To achieve constant time decay_load.
2708 if (unlikely(local_n
>= LOAD_AVG_PERIOD
)) {
2709 val
>>= local_n
/ LOAD_AVG_PERIOD
;
2710 local_n
%= LOAD_AVG_PERIOD
;
2713 val
= mul_u64_u32_shr(val
, runnable_avg_yN_inv
[local_n
], 32);
2718 * For updates fully spanning n periods, the contribution to runnable
2719 * average will be: \Sum 1024*y^n
2721 * We can compute this reasonably efficiently by combining:
2722 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD}
2724 static u32
__compute_runnable_contrib(u64 n
)
2728 if (likely(n
<= LOAD_AVG_PERIOD
))
2729 return runnable_avg_yN_sum
[n
];
2730 else if (unlikely(n
>= LOAD_AVG_MAX_N
))
2731 return LOAD_AVG_MAX
;
2733 /* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
2734 contrib
= __accumulated_sum_N32
[n
/LOAD_AVG_PERIOD
];
2735 n
%= LOAD_AVG_PERIOD
;
2736 contrib
= decay_load(contrib
, n
);
2737 return contrib
+ runnable_avg_yN_sum
[n
];
2740 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2743 * We can represent the historical contribution to runnable average as the
2744 * coefficients of a geometric series. To do this we sub-divide our runnable
2745 * history into segments of approximately 1ms (1024us); label the segment that
2746 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
2748 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
2750 * (now) (~1ms ago) (~2ms ago)
2752 * Let u_i denote the fraction of p_i that the entity was runnable.
2754 * We then designate the fractions u_i as our co-efficients, yielding the
2755 * following representation of historical load:
2756 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
2758 * We choose y based on the with of a reasonably scheduling period, fixing:
2761 * This means that the contribution to load ~32ms ago (u_32) will be weighted
2762 * approximately half as much as the contribution to load within the last ms
2765 * When a period "rolls over" and we have new u_0`, multiplying the previous
2766 * sum again by y is sufficient to update:
2767 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
2768 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
2770 static __always_inline
int
2771 __update_load_avg(u64 now
, int cpu
, struct sched_avg
*sa
,
2772 unsigned long weight
, int running
, struct cfs_rq
*cfs_rq
)
2774 u64 delta
, scaled_delta
, periods
;
2776 unsigned int delta_w
, scaled_delta_w
, decayed
= 0;
2777 unsigned long scale_freq
, scale_cpu
;
2779 delta
= now
- sa
->last_update_time
;
2781 * This should only happen when time goes backwards, which it
2782 * unfortunately does during sched clock init when we swap over to TSC.
2784 if ((s64
)delta
< 0) {
2785 sa
->last_update_time
= now
;
2790 * Use 1024ns as the unit of measurement since it's a reasonable
2791 * approximation of 1us and fast to compute.
2796 sa
->last_update_time
= now
;
2798 scale_freq
= arch_scale_freq_capacity(NULL
, cpu
);
2799 scale_cpu
= arch_scale_cpu_capacity(NULL
, cpu
);
2801 /* delta_w is the amount already accumulated against our next period */
2802 delta_w
= sa
->period_contrib
;
2803 if (delta
+ delta_w
>= 1024) {
2806 /* how much left for next period will start over, we don't know yet */
2807 sa
->period_contrib
= 0;
2810 * Now that we know we're crossing a period boundary, figure
2811 * out how much from delta we need to complete the current
2812 * period and accrue it.
2814 delta_w
= 1024 - delta_w
;
2815 scaled_delta_w
= cap_scale(delta_w
, scale_freq
);
2817 sa
->load_sum
+= weight
* scaled_delta_w
;
2819 cfs_rq
->runnable_load_sum
+=
2820 weight
* scaled_delta_w
;
2824 sa
->util_sum
+= scaled_delta_w
* scale_cpu
;
2828 /* Figure out how many additional periods this update spans */
2829 periods
= delta
/ 1024;
2832 sa
->load_sum
= decay_load(sa
->load_sum
, periods
+ 1);
2834 cfs_rq
->runnable_load_sum
=
2835 decay_load(cfs_rq
->runnable_load_sum
, periods
+ 1);
2837 sa
->util_sum
= decay_load((u64
)(sa
->util_sum
), periods
+ 1);
2839 /* Efficiently calculate \sum (1..n_period) 1024*y^i */
2840 contrib
= __compute_runnable_contrib(periods
);
2841 contrib
= cap_scale(contrib
, scale_freq
);
2843 sa
->load_sum
+= weight
* contrib
;
2845 cfs_rq
->runnable_load_sum
+= weight
* contrib
;
2848 sa
->util_sum
+= contrib
* scale_cpu
;
2851 /* Remainder of delta accrued against u_0` */
2852 scaled_delta
= cap_scale(delta
, scale_freq
);
2854 sa
->load_sum
+= weight
* scaled_delta
;
2856 cfs_rq
->runnable_load_sum
+= weight
* scaled_delta
;
2859 sa
->util_sum
+= scaled_delta
* scale_cpu
;
2861 sa
->period_contrib
+= delta
;
2864 sa
->load_avg
= div_u64(sa
->load_sum
, LOAD_AVG_MAX
);
2866 cfs_rq
->runnable_load_avg
=
2867 div_u64(cfs_rq
->runnable_load_sum
, LOAD_AVG_MAX
);
2869 sa
->util_avg
= sa
->util_sum
/ LOAD_AVG_MAX
;
2875 #ifdef CONFIG_FAIR_GROUP_SCHED
2877 * update_tg_load_avg - update the tg's load avg
2878 * @cfs_rq: the cfs_rq whose avg changed
2879 * @force: update regardless of how small the difference
2881 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
2882 * However, because tg->load_avg is a global value there are performance
2885 * In order to avoid having to look at the other cfs_rq's, we use a
2886 * differential update where we store the last value we propagated. This in
2887 * turn allows skipping updates if the differential is 'small'.
2889 * Updating tg's load_avg is necessary before update_cfs_share() (which is
2890 * done) and effective_load() (which is not done because it is too costly).
2892 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
)
2894 long delta
= cfs_rq
->avg
.load_avg
- cfs_rq
->tg_load_avg_contrib
;
2897 * No need to update load_avg for root_task_group as it is not used.
2899 if (cfs_rq
->tg
== &root_task_group
)
2902 if (force
|| abs(delta
) > cfs_rq
->tg_load_avg_contrib
/ 64) {
2903 atomic_long_add(delta
, &cfs_rq
->tg
->load_avg
);
2904 cfs_rq
->tg_load_avg_contrib
= cfs_rq
->avg
.load_avg
;
2909 * Called within set_task_rq() right before setting a task's cpu. The
2910 * caller only guarantees p->pi_lock is held; no other assumptions,
2911 * including the state of rq->lock, should be made.
2913 void set_task_rq_fair(struct sched_entity
*se
,
2914 struct cfs_rq
*prev
, struct cfs_rq
*next
)
2916 if (!sched_feat(ATTACH_AGE_LOAD
))
2920 * We are supposed to update the task to "current" time, then its up to
2921 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
2922 * getting what current time is, so simply throw away the out-of-date
2923 * time. This will result in the wakee task is less decayed, but giving
2924 * the wakee more load sounds not bad.
2926 if (se
->avg
.last_update_time
&& prev
) {
2927 u64 p_last_update_time
;
2928 u64 n_last_update_time
;
2930 #ifndef CONFIG_64BIT
2931 u64 p_last_update_time_copy
;
2932 u64 n_last_update_time_copy
;
2935 p_last_update_time_copy
= prev
->load_last_update_time_copy
;
2936 n_last_update_time_copy
= next
->load_last_update_time_copy
;
2940 p_last_update_time
= prev
->avg
.last_update_time
;
2941 n_last_update_time
= next
->avg
.last_update_time
;
2943 } while (p_last_update_time
!= p_last_update_time_copy
||
2944 n_last_update_time
!= n_last_update_time_copy
);
2946 p_last_update_time
= prev
->avg
.last_update_time
;
2947 n_last_update_time
= next
->avg
.last_update_time
;
2949 __update_load_avg(p_last_update_time
, cpu_of(rq_of(prev
)),
2950 &se
->avg
, 0, 0, NULL
);
2951 se
->avg
.last_update_time
= n_last_update_time
;
2954 #else /* CONFIG_FAIR_GROUP_SCHED */
2955 static inline void update_tg_load_avg(struct cfs_rq
*cfs_rq
, int force
) {}
2956 #endif /* CONFIG_FAIR_GROUP_SCHED */
2958 static inline void cfs_rq_util_change(struct cfs_rq
*cfs_rq
)
2960 if (&this_rq()->cfs
== cfs_rq
) {
2962 * There are a few boundary cases this might miss but it should
2963 * get called often enough that that should (hopefully) not be
2964 * a real problem -- added to that it only calls on the local
2965 * CPU, so if we enqueue remotely we'll miss an update, but
2966 * the next tick/schedule should update.
2968 * It will not get called when we go idle, because the idle
2969 * thread is a different class (!fair), nor will the utilization
2970 * number include things like RT tasks.
2972 * As is, the util number is not freq-invariant (we'd have to
2973 * implement arch_scale_freq_capacity() for that).
2977 cpufreq_update_util(rq_of(cfs_rq
), 0);
2982 * Unsigned subtract and clamp on underflow.
2984 * Explicitly do a load-store to ensure the intermediate value never hits
2985 * memory. This allows lockless observations without ever seeing the negative
2988 #define sub_positive(_ptr, _val) do { \
2989 typeof(_ptr) ptr = (_ptr); \
2990 typeof(*ptr) val = (_val); \
2991 typeof(*ptr) res, var = READ_ONCE(*ptr); \
2995 WRITE_ONCE(*ptr, res); \
2999 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
3000 * @now: current time, as per cfs_rq_clock_task()
3001 * @cfs_rq: cfs_rq to update
3002 * @update_freq: should we call cfs_rq_util_change() or will the call do so
3004 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
3005 * avg. The immediate corollary is that all (fair) tasks must be attached, see
3006 * post_init_entity_util_avg().
3008 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
3010 * Returns true if the load decayed or we removed load.
3012 * Since both these conditions indicate a changed cfs_rq->avg.load we should
3013 * call update_tg_load_avg() when this function returns true.
3016 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
)
3018 struct sched_avg
*sa
= &cfs_rq
->avg
;
3019 int decayed
, removed_load
= 0, removed_util
= 0;
3021 if (atomic_long_read(&cfs_rq
->removed_load_avg
)) {
3022 s64 r
= atomic_long_xchg(&cfs_rq
->removed_load_avg
, 0);
3023 sub_positive(&sa
->load_avg
, r
);
3024 sub_positive(&sa
->load_sum
, r
* LOAD_AVG_MAX
);
3028 if (atomic_long_read(&cfs_rq
->removed_util_avg
)) {
3029 long r
= atomic_long_xchg(&cfs_rq
->removed_util_avg
, 0);
3030 sub_positive(&sa
->util_avg
, r
);
3031 sub_positive(&sa
->util_sum
, r
* LOAD_AVG_MAX
);
3035 decayed
= __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
3036 scale_load_down(cfs_rq
->load
.weight
), cfs_rq
->curr
!= NULL
, cfs_rq
);
3038 #ifndef CONFIG_64BIT
3040 cfs_rq
->load_last_update_time_copy
= sa
->last_update_time
;
3043 if (update_freq
&& (decayed
|| removed_util
))
3044 cfs_rq_util_change(cfs_rq
);
3046 return decayed
|| removed_load
;
3049 /* Update task and its cfs_rq load average */
3050 static inline void update_load_avg(struct sched_entity
*se
, int update_tg
)
3052 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3053 u64 now
= cfs_rq_clock_task(cfs_rq
);
3054 struct rq
*rq
= rq_of(cfs_rq
);
3055 int cpu
= cpu_of(rq
);
3058 * Track task load average for carrying it to new CPU after migrated, and
3059 * track group sched_entity load average for task_h_load calc in migration
3061 __update_load_avg(now
, cpu
, &se
->avg
,
3062 se
->on_rq
* scale_load_down(se
->load
.weight
),
3063 cfs_rq
->curr
== se
, NULL
);
3065 if (update_cfs_rq_load_avg(now
, cfs_rq
, true) && update_tg
)
3066 update_tg_load_avg(cfs_rq
, 0);
3070 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
3071 * @cfs_rq: cfs_rq to attach to
3072 * @se: sched_entity to attach
3074 * Must call update_cfs_rq_load_avg() before this, since we rely on
3075 * cfs_rq->avg.last_update_time being current.
3077 static void attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3079 if (!sched_feat(ATTACH_AGE_LOAD
))
3083 * If we got migrated (either between CPUs or between cgroups) we'll
3084 * have aged the average right before clearing @last_update_time.
3086 * Or we're fresh through post_init_entity_util_avg().
3088 if (se
->avg
.last_update_time
) {
3089 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
3090 &se
->avg
, 0, 0, NULL
);
3093 * XXX: we could have just aged the entire load away if we've been
3094 * absent from the fair class for too long.
3099 se
->avg
.last_update_time
= cfs_rq
->avg
.last_update_time
;
3100 cfs_rq
->avg
.load_avg
+= se
->avg
.load_avg
;
3101 cfs_rq
->avg
.load_sum
+= se
->avg
.load_sum
;
3102 cfs_rq
->avg
.util_avg
+= se
->avg
.util_avg
;
3103 cfs_rq
->avg
.util_sum
+= se
->avg
.util_sum
;
3105 cfs_rq_util_change(cfs_rq
);
3109 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
3110 * @cfs_rq: cfs_rq to detach from
3111 * @se: sched_entity to detach
3113 * Must call update_cfs_rq_load_avg() before this, since we rely on
3114 * cfs_rq->avg.last_update_time being current.
3116 static void detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3118 __update_load_avg(cfs_rq
->avg
.last_update_time
, cpu_of(rq_of(cfs_rq
)),
3119 &se
->avg
, se
->on_rq
* scale_load_down(se
->load
.weight
),
3120 cfs_rq
->curr
== se
, NULL
);
3122 sub_positive(&cfs_rq
->avg
.load_avg
, se
->avg
.load_avg
);
3123 sub_positive(&cfs_rq
->avg
.load_sum
, se
->avg
.load_sum
);
3124 sub_positive(&cfs_rq
->avg
.util_avg
, se
->avg
.util_avg
);
3125 sub_positive(&cfs_rq
->avg
.util_sum
, se
->avg
.util_sum
);
3127 cfs_rq_util_change(cfs_rq
);
3130 /* Add the load generated by se into cfs_rq's load average */
3132 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3134 struct sched_avg
*sa
= &se
->avg
;
3135 u64 now
= cfs_rq_clock_task(cfs_rq
);
3136 int migrated
, decayed
;
3138 migrated
= !sa
->last_update_time
;
3140 __update_load_avg(now
, cpu_of(rq_of(cfs_rq
)), sa
,
3141 se
->on_rq
* scale_load_down(se
->load
.weight
),
3142 cfs_rq
->curr
== se
, NULL
);
3145 decayed
= update_cfs_rq_load_avg(now
, cfs_rq
, !migrated
);
3147 cfs_rq
->runnable_load_avg
+= sa
->load_avg
;
3148 cfs_rq
->runnable_load_sum
+= sa
->load_sum
;
3151 attach_entity_load_avg(cfs_rq
, se
);
3153 if (decayed
|| migrated
)
3154 update_tg_load_avg(cfs_rq
, 0);
3157 /* Remove the runnable load generated by se from cfs_rq's runnable load average */
3159 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3161 update_load_avg(se
, 1);
3163 cfs_rq
->runnable_load_avg
=
3164 max_t(long, cfs_rq
->runnable_load_avg
- se
->avg
.load_avg
, 0);
3165 cfs_rq
->runnable_load_sum
=
3166 max_t(s64
, cfs_rq
->runnable_load_sum
- se
->avg
.load_sum
, 0);
3169 #ifndef CONFIG_64BIT
3170 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3172 u64 last_update_time_copy
;
3173 u64 last_update_time
;
3176 last_update_time_copy
= cfs_rq
->load_last_update_time_copy
;
3178 last_update_time
= cfs_rq
->avg
.last_update_time
;
3179 } while (last_update_time
!= last_update_time_copy
);
3181 return last_update_time
;
3184 static inline u64
cfs_rq_last_update_time(struct cfs_rq
*cfs_rq
)
3186 return cfs_rq
->avg
.last_update_time
;
3191 * Task first catches up with cfs_rq, and then subtract
3192 * itself from the cfs_rq (task must be off the queue now).
3194 void remove_entity_load_avg(struct sched_entity
*se
)
3196 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3197 u64 last_update_time
;
3200 * tasks cannot exit without having gone through wake_up_new_task() ->
3201 * post_init_entity_util_avg() which will have added things to the
3202 * cfs_rq, so we can remove unconditionally.
3204 * Similarly for groups, they will have passed through
3205 * post_init_entity_util_avg() before unregister_sched_fair_group()
3209 last_update_time
= cfs_rq_last_update_time(cfs_rq
);
3211 __update_load_avg(last_update_time
, cpu_of(rq_of(cfs_rq
)), &se
->avg
, 0, 0, NULL
);
3212 atomic_long_add(se
->avg
.load_avg
, &cfs_rq
->removed_load_avg
);
3213 atomic_long_add(se
->avg
.util_avg
, &cfs_rq
->removed_util_avg
);
3216 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq
*cfs_rq
)
3218 return cfs_rq
->runnable_load_avg
;
3221 static inline unsigned long cfs_rq_load_avg(struct cfs_rq
*cfs_rq
)
3223 return cfs_rq
->avg
.load_avg
;
3226 static int idle_balance(struct rq
*this_rq
);
3228 #else /* CONFIG_SMP */
3231 update_cfs_rq_load_avg(u64 now
, struct cfs_rq
*cfs_rq
, bool update_freq
)
3236 static inline void update_load_avg(struct sched_entity
*se
, int not_used
)
3238 cpufreq_update_util(rq_of(cfs_rq_of(se
)), 0);
3242 enqueue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3244 dequeue_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3245 static inline void remove_entity_load_avg(struct sched_entity
*se
) {}
3248 attach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3250 detach_entity_load_avg(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
) {}
3252 static inline int idle_balance(struct rq
*rq
)
3257 #endif /* CONFIG_SMP */
3259 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3261 #ifdef CONFIG_SCHED_DEBUG
3262 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
3267 if (d
> 3*sysctl_sched_latency
)
3268 schedstat_inc(cfs_rq
->nr_spread_over
);
3273 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
3275 u64 vruntime
= cfs_rq
->min_vruntime
;
3278 * The 'current' period is already promised to the current tasks,
3279 * however the extra weight of the new task will slow them down a
3280 * little, place the new task so that it fits in the slot that
3281 * stays open at the end.
3283 if (initial
&& sched_feat(START_DEBIT
))
3284 vruntime
+= sched_vslice(cfs_rq
, se
);
3286 /* sleeps up to a single latency don't count. */
3288 unsigned long thresh
= sysctl_sched_latency
;
3291 * Halve their sleep time's effect, to allow
3292 * for a gentler effect of sleepers:
3294 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
3300 /* ensure we never gain time by being placed backwards. */
3301 se
->vruntime
= max_vruntime(se
->vruntime
, vruntime
);
3304 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
);
3306 static inline void check_schedstat_required(void)
3308 #ifdef CONFIG_SCHEDSTATS
3309 if (schedstat_enabled())
3312 /* Force schedstat enabled if a dependent tracepoint is active */
3313 if (trace_sched_stat_wait_enabled() ||
3314 trace_sched_stat_sleep_enabled() ||
3315 trace_sched_stat_iowait_enabled() ||
3316 trace_sched_stat_blocked_enabled() ||
3317 trace_sched_stat_runtime_enabled()) {
3318 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3319 "stat_blocked and stat_runtime require the "
3320 "kernel parameter schedstats=enabled or "
3321 "kernel.sched_schedstats=1\n");
3332 * update_min_vruntime()
3333 * vruntime -= min_vruntime
3337 * update_min_vruntime()
3338 * vruntime += min_vruntime
3340 * this way the vruntime transition between RQs is done when both
3341 * min_vruntime are up-to-date.
3345 * ->migrate_task_rq_fair() (p->state == TASK_WAKING)
3346 * vruntime -= min_vruntime
3350 * update_min_vruntime()
3351 * vruntime += min_vruntime
3353 * this way we don't have the most up-to-date min_vruntime on the originating
3354 * CPU and an up-to-date min_vruntime on the destination CPU.
3358 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3360 bool renorm
= !(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_MIGRATED
);
3361 bool curr
= cfs_rq
->curr
== se
;
3364 * If we're the current task, we must renormalise before calling
3368 se
->vruntime
+= cfs_rq
->min_vruntime
;
3370 update_curr(cfs_rq
);
3373 * Otherwise, renormalise after, such that we're placed at the current
3374 * moment in time, instead of some random moment in the past. Being
3375 * placed in the past could significantly boost this task to the
3376 * fairness detriment of existing tasks.
3378 if (renorm
&& !curr
)
3379 se
->vruntime
+= cfs_rq
->min_vruntime
;
3381 enqueue_entity_load_avg(cfs_rq
, se
);
3382 account_entity_enqueue(cfs_rq
, se
);
3383 update_cfs_shares(cfs_rq
);
3385 if (flags
& ENQUEUE_WAKEUP
)
3386 place_entity(cfs_rq
, se
, 0);
3388 check_schedstat_required();
3389 update_stats_enqueue(cfs_rq
, se
, flags
);
3390 check_spread(cfs_rq
, se
);
3392 __enqueue_entity(cfs_rq
, se
);
3395 if (cfs_rq
->nr_running
== 1) {
3396 list_add_leaf_cfs_rq(cfs_rq
);
3397 check_enqueue_throttle(cfs_rq
);
3401 static void __clear_buddies_last(struct sched_entity
*se
)
3403 for_each_sched_entity(se
) {
3404 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3405 if (cfs_rq
->last
!= se
)
3408 cfs_rq
->last
= NULL
;
3412 static void __clear_buddies_next(struct sched_entity
*se
)
3414 for_each_sched_entity(se
) {
3415 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3416 if (cfs_rq
->next
!= se
)
3419 cfs_rq
->next
= NULL
;
3423 static void __clear_buddies_skip(struct sched_entity
*se
)
3425 for_each_sched_entity(se
) {
3426 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
3427 if (cfs_rq
->skip
!= se
)
3430 cfs_rq
->skip
= NULL
;
3434 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3436 if (cfs_rq
->last
== se
)
3437 __clear_buddies_last(se
);
3439 if (cfs_rq
->next
== se
)
3440 __clear_buddies_next(se
);
3442 if (cfs_rq
->skip
== se
)
3443 __clear_buddies_skip(se
);
3446 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3449 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
3452 * Update run-time statistics of the 'current'.
3454 update_curr(cfs_rq
);
3455 dequeue_entity_load_avg(cfs_rq
, se
);
3457 update_stats_dequeue(cfs_rq
, se
, flags
);
3459 clear_buddies(cfs_rq
, se
);
3461 if (se
!= cfs_rq
->curr
)
3462 __dequeue_entity(cfs_rq
, se
);
3464 account_entity_dequeue(cfs_rq
, se
);
3467 * Normalize the entity after updating the min_vruntime because the
3468 * update can refer to the ->curr item and we need to reflect this
3469 * movement in our normalized position.
3471 if (!(flags
& DEQUEUE_SLEEP
))
3472 se
->vruntime
-= cfs_rq
->min_vruntime
;
3474 /* return excess runtime on last dequeue */
3475 return_cfs_rq_runtime(cfs_rq
);
3477 update_min_vruntime(cfs_rq
);
3478 update_cfs_shares(cfs_rq
);
3482 * Preempt the current task with a newly woken task if needed:
3485 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3487 unsigned long ideal_runtime
, delta_exec
;
3488 struct sched_entity
*se
;
3491 ideal_runtime
= sched_slice(cfs_rq
, curr
);
3492 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
3493 if (delta_exec
> ideal_runtime
) {
3494 resched_curr(rq_of(cfs_rq
));
3496 * The current task ran long enough, ensure it doesn't get
3497 * re-elected due to buddy favours.
3499 clear_buddies(cfs_rq
, curr
);
3504 * Ensure that a task that missed wakeup preemption by a
3505 * narrow margin doesn't have to wait for a full slice.
3506 * This also mitigates buddy induced latencies under load.
3508 if (delta_exec
< sysctl_sched_min_granularity
)
3511 se
= __pick_first_entity(cfs_rq
);
3512 delta
= curr
->vruntime
- se
->vruntime
;
3517 if (delta
> ideal_runtime
)
3518 resched_curr(rq_of(cfs_rq
));
3522 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
3524 /* 'current' is not kept within the tree. */
3527 * Any task has to be enqueued before it get to execute on
3528 * a CPU. So account for the time it spent waiting on the
3531 update_stats_wait_end(cfs_rq
, se
);
3532 __dequeue_entity(cfs_rq
, se
);
3533 update_load_avg(se
, 1);
3536 update_stats_curr_start(cfs_rq
, se
);
3540 * Track our maximum slice length, if the CPU's load is at
3541 * least twice that of our own weight (i.e. dont track it
3542 * when there are only lesser-weight tasks around):
3544 if (schedstat_enabled() && rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
3545 schedstat_set(se
->statistics
.slice_max
,
3546 max((u64
)schedstat_val(se
->statistics
.slice_max
),
3547 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
));
3550 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
3554 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
3557 * Pick the next process, keeping these things in mind, in this order:
3558 * 1) keep things fair between processes/task groups
3559 * 2) pick the "next" process, since someone really wants that to run
3560 * 3) pick the "last" process, for cache locality
3561 * 4) do not run the "skip" process, if something else is available
3563 static struct sched_entity
*
3564 pick_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
3566 struct sched_entity
*left
= __pick_first_entity(cfs_rq
);
3567 struct sched_entity
*se
;
3570 * If curr is set we have to see if its left of the leftmost entity
3571 * still in the tree, provided there was anything in the tree at all.
3573 if (!left
|| (curr
&& entity_before(curr
, left
)))
3576 se
= left
; /* ideally we run the leftmost entity */
3579 * Avoid running the skip buddy, if running something else can
3580 * be done without getting too unfair.
3582 if (cfs_rq
->skip
== se
) {
3583 struct sched_entity
*second
;
3586 second
= __pick_first_entity(cfs_rq
);
3588 second
= __pick_next_entity(se
);
3589 if (!second
|| (curr
&& entity_before(curr
, second
)))
3593 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
3598 * Prefer last buddy, try to return the CPU to a preempted task.
3600 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
3604 * Someone really wants this to run. If it's not unfair, run it.
3606 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
3609 clear_buddies(cfs_rq
, se
);
3614 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
);
3616 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
3619 * If still on the runqueue then deactivate_task()
3620 * was not called and update_curr() has to be done:
3623 update_curr(cfs_rq
);
3625 /* throttle cfs_rqs exceeding runtime */
3626 check_cfs_rq_runtime(cfs_rq
);
3628 check_spread(cfs_rq
, prev
);
3631 update_stats_wait_start(cfs_rq
, prev
);
3632 /* Put 'current' back into the tree. */
3633 __enqueue_entity(cfs_rq
, prev
);
3634 /* in !on_rq case, update occurred at dequeue */
3635 update_load_avg(prev
, 0);
3637 cfs_rq
->curr
= NULL
;
3641 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
3644 * Update run-time statistics of the 'current'.
3646 update_curr(cfs_rq
);
3649 * Ensure that runnable average is periodically updated.
3651 update_load_avg(curr
, 1);
3652 update_cfs_shares(cfs_rq
);
3654 #ifdef CONFIG_SCHED_HRTICK
3656 * queued ticks are scheduled to match the slice, so don't bother
3657 * validating it and just reschedule.
3660 resched_curr(rq_of(cfs_rq
));
3664 * don't let the period tick interfere with the hrtick preemption
3666 if (!sched_feat(DOUBLE_TICK
) &&
3667 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
3671 if (cfs_rq
->nr_running
> 1)
3672 check_preempt_tick(cfs_rq
, curr
);
3676 /**************************************************
3677 * CFS bandwidth control machinery
3680 #ifdef CONFIG_CFS_BANDWIDTH
3682 #ifdef HAVE_JUMP_LABEL
3683 static struct static_key __cfs_bandwidth_used
;
3685 static inline bool cfs_bandwidth_used(void)
3687 return static_key_false(&__cfs_bandwidth_used
);
3690 void cfs_bandwidth_usage_inc(void)
3692 static_key_slow_inc(&__cfs_bandwidth_used
);
3695 void cfs_bandwidth_usage_dec(void)
3697 static_key_slow_dec(&__cfs_bandwidth_used
);
3699 #else /* HAVE_JUMP_LABEL */
3700 static bool cfs_bandwidth_used(void)
3705 void cfs_bandwidth_usage_inc(void) {}
3706 void cfs_bandwidth_usage_dec(void) {}
3707 #endif /* HAVE_JUMP_LABEL */
3710 * default period for cfs group bandwidth.
3711 * default: 0.1s, units: nanoseconds
3713 static inline u64
default_cfs_period(void)
3715 return 100000000ULL;
3718 static inline u64
sched_cfs_bandwidth_slice(void)
3720 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
3724 * Replenish runtime according to assigned quota and update expiration time.
3725 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
3726 * additional synchronization around rq->lock.
3728 * requires cfs_b->lock
3730 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
3734 if (cfs_b
->quota
== RUNTIME_INF
)
3737 now
= sched_clock_cpu(smp_processor_id());
3738 cfs_b
->runtime
= cfs_b
->quota
;
3739 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
3742 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
3744 return &tg
->cfs_bandwidth
;
3747 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */
3748 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
3750 if (unlikely(cfs_rq
->throttle_count
))
3751 return cfs_rq
->throttled_clock_task
- cfs_rq
->throttled_clock_task_time
;
3753 return rq_clock_task(rq_of(cfs_rq
)) - cfs_rq
->throttled_clock_task_time
;
3756 /* returns 0 on failure to allocate runtime */
3757 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3759 struct task_group
*tg
= cfs_rq
->tg
;
3760 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
3761 u64 amount
= 0, min_amount
, expires
;
3763 /* note: this is a positive sum as runtime_remaining <= 0 */
3764 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
3766 raw_spin_lock(&cfs_b
->lock
);
3767 if (cfs_b
->quota
== RUNTIME_INF
)
3768 amount
= min_amount
;
3770 start_cfs_bandwidth(cfs_b
);
3772 if (cfs_b
->runtime
> 0) {
3773 amount
= min(cfs_b
->runtime
, min_amount
);
3774 cfs_b
->runtime
-= amount
;
3778 expires
= cfs_b
->runtime_expires
;
3779 raw_spin_unlock(&cfs_b
->lock
);
3781 cfs_rq
->runtime_remaining
+= amount
;
3783 * we may have advanced our local expiration to account for allowed
3784 * spread between our sched_clock and the one on which runtime was
3787 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
3788 cfs_rq
->runtime_expires
= expires
;
3790 return cfs_rq
->runtime_remaining
> 0;
3794 * Note: This depends on the synchronization provided by sched_clock and the
3795 * fact that rq->clock snapshots this value.
3797 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
3799 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3801 /* if the deadline is ahead of our clock, nothing to do */
3802 if (likely((s64
)(rq_clock(rq_of(cfs_rq
)) - cfs_rq
->runtime_expires
) < 0))
3805 if (cfs_rq
->runtime_remaining
< 0)
3809 * If the local deadline has passed we have to consider the
3810 * possibility that our sched_clock is 'fast' and the global deadline
3811 * has not truly expired.
3813 * Fortunately we can check determine whether this the case by checking
3814 * whether the global deadline has advanced. It is valid to compare
3815 * cfs_b->runtime_expires without any locks since we only care about
3816 * exact equality, so a partial write will still work.
3819 if (cfs_rq
->runtime_expires
!= cfs_b
->runtime_expires
) {
3820 /* extend local deadline, drift is bounded above by 2 ticks */
3821 cfs_rq
->runtime_expires
+= TICK_NSEC
;
3823 /* global deadline is ahead, expiration has passed */
3824 cfs_rq
->runtime_remaining
= 0;
3828 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3830 /* dock delta_exec before expiring quota (as it could span periods) */
3831 cfs_rq
->runtime_remaining
-= delta_exec
;
3832 expire_cfs_rq_runtime(cfs_rq
);
3834 if (likely(cfs_rq
->runtime_remaining
> 0))
3838 * if we're unable to extend our runtime we resched so that the active
3839 * hierarchy can be throttled
3841 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
3842 resched_curr(rq_of(cfs_rq
));
3845 static __always_inline
3846 void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
)
3848 if (!cfs_bandwidth_used() || !cfs_rq
->runtime_enabled
)
3851 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
3854 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
3856 return cfs_bandwidth_used() && cfs_rq
->throttled
;
3859 /* check whether cfs_rq, or any parent, is throttled */
3860 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
3862 return cfs_bandwidth_used() && cfs_rq
->throttle_count
;
3866 * Ensure that neither of the group entities corresponding to src_cpu or
3867 * dest_cpu are members of a throttled hierarchy when performing group
3868 * load-balance operations.
3870 static inline int throttled_lb_pair(struct task_group
*tg
,
3871 int src_cpu
, int dest_cpu
)
3873 struct cfs_rq
*src_cfs_rq
, *dest_cfs_rq
;
3875 src_cfs_rq
= tg
->cfs_rq
[src_cpu
];
3876 dest_cfs_rq
= tg
->cfs_rq
[dest_cpu
];
3878 return throttled_hierarchy(src_cfs_rq
) ||
3879 throttled_hierarchy(dest_cfs_rq
);
3882 /* updated child weight may affect parent so we have to do this bottom up */
3883 static int tg_unthrottle_up(struct task_group
*tg
, void *data
)
3885 struct rq
*rq
= data
;
3886 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3888 cfs_rq
->throttle_count
--;
3889 if (!cfs_rq
->throttle_count
) {
3890 /* adjust cfs_rq_clock_task() */
3891 cfs_rq
->throttled_clock_task_time
+= rq_clock_task(rq
) -
3892 cfs_rq
->throttled_clock_task
;
3898 static int tg_throttle_down(struct task_group
*tg
, void *data
)
3900 struct rq
*rq
= data
;
3901 struct cfs_rq
*cfs_rq
= tg
->cfs_rq
[cpu_of(rq
)];
3903 /* group is entering throttled state, stop time */
3904 if (!cfs_rq
->throttle_count
)
3905 cfs_rq
->throttled_clock_task
= rq_clock_task(rq
);
3906 cfs_rq
->throttle_count
++;
3911 static void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
3913 struct rq
*rq
= rq_of(cfs_rq
);
3914 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3915 struct sched_entity
*se
;
3916 long task_delta
, dequeue
= 1;
3919 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
3921 /* freeze hierarchy runnable averages while throttled */
3923 walk_tg_tree_from(cfs_rq
->tg
, tg_throttle_down
, tg_nop
, (void *)rq
);
3926 task_delta
= cfs_rq
->h_nr_running
;
3927 for_each_sched_entity(se
) {
3928 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
3929 /* throttled entity or throttle-on-deactivate */
3934 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
3935 qcfs_rq
->h_nr_running
-= task_delta
;
3937 if (qcfs_rq
->load
.weight
)
3942 sub_nr_running(rq
, task_delta
);
3944 cfs_rq
->throttled
= 1;
3945 cfs_rq
->throttled_clock
= rq_clock(rq
);
3946 raw_spin_lock(&cfs_b
->lock
);
3947 empty
= list_empty(&cfs_b
->throttled_cfs_rq
);
3950 * Add to the _head_ of the list, so that an already-started
3951 * distribute_cfs_runtime will not see us
3953 list_add_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
3956 * If we're the first throttled task, make sure the bandwidth
3960 start_cfs_bandwidth(cfs_b
);
3962 raw_spin_unlock(&cfs_b
->lock
);
3965 void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
3967 struct rq
*rq
= rq_of(cfs_rq
);
3968 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
3969 struct sched_entity
*se
;
3973 se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
3975 cfs_rq
->throttled
= 0;
3977 update_rq_clock(rq
);
3979 raw_spin_lock(&cfs_b
->lock
);
3980 cfs_b
->throttled_time
+= rq_clock(rq
) - cfs_rq
->throttled_clock
;
3981 list_del_rcu(&cfs_rq
->throttled_list
);
3982 raw_spin_unlock(&cfs_b
->lock
);
3984 /* update hierarchical throttle state */
3985 walk_tg_tree_from(cfs_rq
->tg
, tg_nop
, tg_unthrottle_up
, (void *)rq
);
3987 if (!cfs_rq
->load
.weight
)
3990 task_delta
= cfs_rq
->h_nr_running
;
3991 for_each_sched_entity(se
) {
3995 cfs_rq
= cfs_rq_of(se
);
3997 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
3998 cfs_rq
->h_nr_running
+= task_delta
;
4000 if (cfs_rq_throttled(cfs_rq
))
4005 add_nr_running(rq
, task_delta
);
4007 /* determine whether we need to wake up potentially idle cpu */
4008 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
4012 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
4013 u64 remaining
, u64 expires
)
4015 struct cfs_rq
*cfs_rq
;
4017 u64 starting_runtime
= remaining
;
4020 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
4022 struct rq
*rq
= rq_of(cfs_rq
);
4024 raw_spin_lock(&rq
->lock
);
4025 if (!cfs_rq_throttled(cfs_rq
))
4028 runtime
= -cfs_rq
->runtime_remaining
+ 1;
4029 if (runtime
> remaining
)
4030 runtime
= remaining
;
4031 remaining
-= runtime
;
4033 cfs_rq
->runtime_remaining
+= runtime
;
4034 cfs_rq
->runtime_expires
= expires
;
4036 /* we check whether we're throttled above */
4037 if (cfs_rq
->runtime_remaining
> 0)
4038 unthrottle_cfs_rq(cfs_rq
);
4041 raw_spin_unlock(&rq
->lock
);
4048 return starting_runtime
- remaining
;
4052 * Responsible for refilling a task_group's bandwidth and unthrottling its
4053 * cfs_rqs as appropriate. If there has been no activity within the last
4054 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
4055 * used to track this state.
4057 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
4059 u64 runtime
, runtime_expires
;
4062 /* no need to continue the timer with no bandwidth constraint */
4063 if (cfs_b
->quota
== RUNTIME_INF
)
4064 goto out_deactivate
;
4066 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4067 cfs_b
->nr_periods
+= overrun
;
4070 * idle depends on !throttled (for the case of a large deficit), and if
4071 * we're going inactive then everything else can be deferred
4073 if (cfs_b
->idle
&& !throttled
)
4074 goto out_deactivate
;
4076 __refill_cfs_bandwidth_runtime(cfs_b
);
4079 /* mark as potentially idle for the upcoming period */
4084 /* account preceding periods in which throttling occurred */
4085 cfs_b
->nr_throttled
+= overrun
;
4087 runtime_expires
= cfs_b
->runtime_expires
;
4090 * This check is repeated as we are holding onto the new bandwidth while
4091 * we unthrottle. This can potentially race with an unthrottled group
4092 * trying to acquire new bandwidth from the global pool. This can result
4093 * in us over-using our runtime if it is all used during this loop, but
4094 * only by limited amounts in that extreme case.
4096 while (throttled
&& cfs_b
->runtime
> 0) {
4097 runtime
= cfs_b
->runtime
;
4098 raw_spin_unlock(&cfs_b
->lock
);
4099 /* we can't nest cfs_b->lock while distributing bandwidth */
4100 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
4102 raw_spin_lock(&cfs_b
->lock
);
4104 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
4106 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4110 * While we are ensured activity in the period following an
4111 * unthrottle, this also covers the case in which the new bandwidth is
4112 * insufficient to cover the existing bandwidth deficit. (Forcing the
4113 * timer to remain active while there are any throttled entities.)
4123 /* a cfs_rq won't donate quota below this amount */
4124 static const u64 min_cfs_rq_runtime
= 1 * NSEC_PER_MSEC
;
4125 /* minimum remaining period time to redistribute slack quota */
4126 static const u64 min_bandwidth_expiration
= 2 * NSEC_PER_MSEC
;
4127 /* how long we wait to gather additional slack before distributing */
4128 static const u64 cfs_bandwidth_slack_period
= 5 * NSEC_PER_MSEC
;
4131 * Are we near the end of the current quota period?
4133 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4134 * hrtimer base being cleared by hrtimer_start. In the case of
4135 * migrate_hrtimers, base is never cleared, so we are fine.
4137 static int runtime_refresh_within(struct cfs_bandwidth
*cfs_b
, u64 min_expire
)
4139 struct hrtimer
*refresh_timer
= &cfs_b
->period_timer
;
4142 /* if the call-back is running a quota refresh is already occurring */
4143 if (hrtimer_callback_running(refresh_timer
))
4146 /* is a quota refresh about to occur? */
4147 remaining
= ktime_to_ns(hrtimer_expires_remaining(refresh_timer
));
4148 if (remaining
< min_expire
)
4154 static void start_cfs_slack_bandwidth(struct cfs_bandwidth
*cfs_b
)
4156 u64 min_left
= cfs_bandwidth_slack_period
+ min_bandwidth_expiration
;
4158 /* if there's a quota refresh soon don't bother with slack */
4159 if (runtime_refresh_within(cfs_b
, min_left
))
4162 hrtimer_start(&cfs_b
->slack_timer
,
4163 ns_to_ktime(cfs_bandwidth_slack_period
),
4167 /* we know any runtime found here is valid as update_curr() precedes return */
4168 static void __return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4170 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
4171 s64 slack_runtime
= cfs_rq
->runtime_remaining
- min_cfs_rq_runtime
;
4173 if (slack_runtime
<= 0)
4176 raw_spin_lock(&cfs_b
->lock
);
4177 if (cfs_b
->quota
!= RUNTIME_INF
&&
4178 cfs_rq
->runtime_expires
== cfs_b
->runtime_expires
) {
4179 cfs_b
->runtime
+= slack_runtime
;
4181 /* we are under rq->lock, defer unthrottling using a timer */
4182 if (cfs_b
->runtime
> sched_cfs_bandwidth_slice() &&
4183 !list_empty(&cfs_b
->throttled_cfs_rq
))
4184 start_cfs_slack_bandwidth(cfs_b
);
4186 raw_spin_unlock(&cfs_b
->lock
);
4188 /* even if it's not valid for return we don't want to try again */
4189 cfs_rq
->runtime_remaining
-= slack_runtime
;
4192 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4194 if (!cfs_bandwidth_used())
4197 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->nr_running
)
4200 __return_cfs_rq_runtime(cfs_rq
);
4204 * This is done with a timer (instead of inline with bandwidth return) since
4205 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
4207 static void do_sched_cfs_slack_timer(struct cfs_bandwidth
*cfs_b
)
4209 u64 runtime
= 0, slice
= sched_cfs_bandwidth_slice();
4212 /* confirm we're still not at a refresh boundary */
4213 raw_spin_lock(&cfs_b
->lock
);
4214 if (runtime_refresh_within(cfs_b
, min_bandwidth_expiration
)) {
4215 raw_spin_unlock(&cfs_b
->lock
);
4219 if (cfs_b
->quota
!= RUNTIME_INF
&& cfs_b
->runtime
> slice
)
4220 runtime
= cfs_b
->runtime
;
4222 expires
= cfs_b
->runtime_expires
;
4223 raw_spin_unlock(&cfs_b
->lock
);
4228 runtime
= distribute_cfs_runtime(cfs_b
, runtime
, expires
);
4230 raw_spin_lock(&cfs_b
->lock
);
4231 if (expires
== cfs_b
->runtime_expires
)
4232 cfs_b
->runtime
-= min(runtime
, cfs_b
->runtime
);
4233 raw_spin_unlock(&cfs_b
->lock
);
4237 * When a group wakes up we want to make sure that its quota is not already
4238 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
4239 * runtime as update_curr() throttling can not not trigger until it's on-rq.
4241 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
)
4243 if (!cfs_bandwidth_used())
4246 /* an active group must be handled by the update_curr()->put() path */
4247 if (!cfs_rq
->runtime_enabled
|| cfs_rq
->curr
)
4250 /* ensure the group is not already throttled */
4251 if (cfs_rq_throttled(cfs_rq
))
4254 /* update runtime allocation */
4255 account_cfs_rq_runtime(cfs_rq
, 0);
4256 if (cfs_rq
->runtime_remaining
<= 0)
4257 throttle_cfs_rq(cfs_rq
);
4260 static void sync_throttle(struct task_group
*tg
, int cpu
)
4262 struct cfs_rq
*pcfs_rq
, *cfs_rq
;
4264 if (!cfs_bandwidth_used())
4270 cfs_rq
= tg
->cfs_rq
[cpu
];
4271 pcfs_rq
= tg
->parent
->cfs_rq
[cpu
];
4273 cfs_rq
->throttle_count
= pcfs_rq
->throttle_count
;
4274 cfs_rq
->throttled_clock_task
= rq_clock_task(cpu_rq(cpu
));
4277 /* conditionally throttle active cfs_rq's from put_prev_entity() */
4278 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4280 if (!cfs_bandwidth_used())
4283 if (likely(!cfs_rq
->runtime_enabled
|| cfs_rq
->runtime_remaining
> 0))
4287 * it's possible for a throttled entity to be forced into a running
4288 * state (e.g. set_curr_task), in this case we're finished.
4290 if (cfs_rq_throttled(cfs_rq
))
4293 throttle_cfs_rq(cfs_rq
);
4297 static enum hrtimer_restart
sched_cfs_slack_timer(struct hrtimer
*timer
)
4299 struct cfs_bandwidth
*cfs_b
=
4300 container_of(timer
, struct cfs_bandwidth
, slack_timer
);
4302 do_sched_cfs_slack_timer(cfs_b
);
4304 return HRTIMER_NORESTART
;
4307 static enum hrtimer_restart
sched_cfs_period_timer(struct hrtimer
*timer
)
4309 struct cfs_bandwidth
*cfs_b
=
4310 container_of(timer
, struct cfs_bandwidth
, period_timer
);
4314 raw_spin_lock(&cfs_b
->lock
);
4316 overrun
= hrtimer_forward_now(timer
, cfs_b
->period
);
4320 idle
= do_sched_cfs_period_timer(cfs_b
, overrun
);
4323 cfs_b
->period_active
= 0;
4324 raw_spin_unlock(&cfs_b
->lock
);
4326 return idle
? HRTIMER_NORESTART
: HRTIMER_RESTART
;
4329 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4331 raw_spin_lock_init(&cfs_b
->lock
);
4333 cfs_b
->quota
= RUNTIME_INF
;
4334 cfs_b
->period
= ns_to_ktime(default_cfs_period());
4336 INIT_LIST_HEAD(&cfs_b
->throttled_cfs_rq
);
4337 hrtimer_init(&cfs_b
->period_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS_PINNED
);
4338 cfs_b
->period_timer
.function
= sched_cfs_period_timer
;
4339 hrtimer_init(&cfs_b
->slack_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
4340 cfs_b
->slack_timer
.function
= sched_cfs_slack_timer
;
4343 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
4345 cfs_rq
->runtime_enabled
= 0;
4346 INIT_LIST_HEAD(&cfs_rq
->throttled_list
);
4349 void start_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4351 lockdep_assert_held(&cfs_b
->lock
);
4353 if (!cfs_b
->period_active
) {
4354 cfs_b
->period_active
= 1;
4355 hrtimer_forward_now(&cfs_b
->period_timer
, cfs_b
->period
);
4356 hrtimer_start_expires(&cfs_b
->period_timer
, HRTIMER_MODE_ABS_PINNED
);
4360 static void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
)
4362 /* init_cfs_bandwidth() was not called */
4363 if (!cfs_b
->throttled_cfs_rq
.next
)
4366 hrtimer_cancel(&cfs_b
->period_timer
);
4367 hrtimer_cancel(&cfs_b
->slack_timer
);
4370 static void __maybe_unused
update_runtime_enabled(struct rq
*rq
)
4372 struct cfs_rq
*cfs_rq
;
4374 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4375 struct cfs_bandwidth
*cfs_b
= &cfs_rq
->tg
->cfs_bandwidth
;
4377 raw_spin_lock(&cfs_b
->lock
);
4378 cfs_rq
->runtime_enabled
= cfs_b
->quota
!= RUNTIME_INF
;
4379 raw_spin_unlock(&cfs_b
->lock
);
4383 static void __maybe_unused
unthrottle_offline_cfs_rqs(struct rq
*rq
)
4385 struct cfs_rq
*cfs_rq
;
4387 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
4388 if (!cfs_rq
->runtime_enabled
)
4392 * clock_task is not advancing so we just need to make sure
4393 * there's some valid quota amount
4395 cfs_rq
->runtime_remaining
= 1;
4397 * Offline rq is schedulable till cpu is completely disabled
4398 * in take_cpu_down(), so we prevent new cfs throttling here.
4400 cfs_rq
->runtime_enabled
= 0;
4402 if (cfs_rq_throttled(cfs_rq
))
4403 unthrottle_cfs_rq(cfs_rq
);
4407 #else /* CONFIG_CFS_BANDWIDTH */
4408 static inline u64
cfs_rq_clock_task(struct cfs_rq
*cfs_rq
)
4410 return rq_clock_task(rq_of(cfs_rq
));
4413 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
, u64 delta_exec
) {}
4414 static bool check_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) { return false; }
4415 static void check_enqueue_throttle(struct cfs_rq
*cfs_rq
) {}
4416 static inline void sync_throttle(struct task_group
*tg
, int cpu
) {}
4417 static __always_inline
void return_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4419 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
4424 static inline int throttled_hierarchy(struct cfs_rq
*cfs_rq
)
4429 static inline int throttled_lb_pair(struct task_group
*tg
,
4430 int src_cpu
, int dest_cpu
)
4435 void init_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4437 #ifdef CONFIG_FAIR_GROUP_SCHED
4438 static void init_cfs_rq_runtime(struct cfs_rq
*cfs_rq
) {}
4441 static inline struct cfs_bandwidth
*tg_cfs_bandwidth(struct task_group
*tg
)
4445 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth
*cfs_b
) {}
4446 static inline void update_runtime_enabled(struct rq
*rq
) {}
4447 static inline void unthrottle_offline_cfs_rqs(struct rq
*rq
) {}
4449 #endif /* CONFIG_CFS_BANDWIDTH */
4451 /**************************************************
4452 * CFS operations on tasks:
4455 #ifdef CONFIG_SCHED_HRTICK
4456 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4458 struct sched_entity
*se
= &p
->se
;
4459 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4461 WARN_ON(task_rq(p
) != rq
);
4463 if (cfs_rq
->nr_running
> 1) {
4464 u64 slice
= sched_slice(cfs_rq
, se
);
4465 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
4466 s64 delta
= slice
- ran
;
4473 hrtick_start(rq
, delta
);
4478 * called from enqueue/dequeue and updates the hrtick when the
4479 * current task is from our class and nr_running is low enough
4482 static void hrtick_update(struct rq
*rq
)
4484 struct task_struct
*curr
= rq
->curr
;
4486 if (!hrtick_enabled(rq
) || curr
->sched_class
!= &fair_sched_class
)
4489 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
4490 hrtick_start_fair(rq
, curr
);
4492 #else /* !CONFIG_SCHED_HRTICK */
4494 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
4498 static inline void hrtick_update(struct rq
*rq
)
4504 * The enqueue_task method is called before nr_running is
4505 * increased. Here we update the fair scheduling stats and
4506 * then put the task into the rbtree:
4509 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4511 struct cfs_rq
*cfs_rq
;
4512 struct sched_entity
*se
= &p
->se
;
4514 for_each_sched_entity(se
) {
4517 cfs_rq
= cfs_rq_of(se
);
4518 enqueue_entity(cfs_rq
, se
, flags
);
4521 * end evaluation on encountering a throttled cfs_rq
4523 * note: in the case of encountering a throttled cfs_rq we will
4524 * post the final h_nr_running increment below.
4526 if (cfs_rq_throttled(cfs_rq
))
4528 cfs_rq
->h_nr_running
++;
4530 flags
= ENQUEUE_WAKEUP
;
4533 for_each_sched_entity(se
) {
4534 cfs_rq
= cfs_rq_of(se
);
4535 cfs_rq
->h_nr_running
++;
4537 if (cfs_rq_throttled(cfs_rq
))
4540 update_load_avg(se
, 1);
4541 update_cfs_shares(cfs_rq
);
4545 add_nr_running(rq
, 1);
4550 static void set_next_buddy(struct sched_entity
*se
);
4553 * The dequeue_task method is called before nr_running is
4554 * decreased. We remove the task from the rbtree and
4555 * update the fair scheduling stats:
4557 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
4559 struct cfs_rq
*cfs_rq
;
4560 struct sched_entity
*se
= &p
->se
;
4561 int task_sleep
= flags
& DEQUEUE_SLEEP
;
4563 for_each_sched_entity(se
) {
4564 cfs_rq
= cfs_rq_of(se
);
4565 dequeue_entity(cfs_rq
, se
, flags
);
4568 * end evaluation on encountering a throttled cfs_rq
4570 * note: in the case of encountering a throttled cfs_rq we will
4571 * post the final h_nr_running decrement below.
4573 if (cfs_rq_throttled(cfs_rq
))
4575 cfs_rq
->h_nr_running
--;
4577 /* Don't dequeue parent if it has other entities besides us */
4578 if (cfs_rq
->load
.weight
) {
4579 /* Avoid re-evaluating load for this entity: */
4580 se
= parent_entity(se
);
4582 * Bias pick_next to pick a task from this cfs_rq, as
4583 * p is sleeping when it is within its sched_slice.
4585 if (task_sleep
&& se
&& !throttled_hierarchy(cfs_rq
))
4589 flags
|= DEQUEUE_SLEEP
;
4592 for_each_sched_entity(se
) {
4593 cfs_rq
= cfs_rq_of(se
);
4594 cfs_rq
->h_nr_running
--;
4596 if (cfs_rq_throttled(cfs_rq
))
4599 update_load_avg(se
, 1);
4600 update_cfs_shares(cfs_rq
);
4604 sub_nr_running(rq
, 1);
4610 #ifdef CONFIG_NO_HZ_COMMON
4612 * per rq 'load' arrray crap; XXX kill this.
4616 * The exact cpuload calculated at every tick would be:
4618 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
4620 * If a cpu misses updates for n ticks (as it was idle) and update gets
4621 * called on the n+1-th tick when cpu may be busy, then we have:
4623 * load_n = (1 - 1/2^i)^n * load_0
4624 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load
4626 * decay_load_missed() below does efficient calculation of
4628 * load' = (1 - 1/2^i)^n * load
4630 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
4631 * This allows us to precompute the above in said factors, thereby allowing the
4632 * reduction of an arbitrary n in O(log_2 n) steps. (See also
4633 * fixed_power_int())
4635 * The calculation is approximated on a 128 point scale.
4637 #define DEGRADE_SHIFT 7
4639 static const u8 degrade_zero_ticks
[CPU_LOAD_IDX_MAX
] = {0, 8, 32, 64, 128};
4640 static const u8 degrade_factor
[CPU_LOAD_IDX_MAX
][DEGRADE_SHIFT
+ 1] = {
4641 { 0, 0, 0, 0, 0, 0, 0, 0 },
4642 { 64, 32, 8, 0, 0, 0, 0, 0 },
4643 { 96, 72, 40, 12, 1, 0, 0, 0 },
4644 { 112, 98, 75, 43, 15, 1, 0, 0 },
4645 { 120, 112, 98, 76, 45, 16, 2, 0 }
4649 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
4650 * would be when CPU is idle and so we just decay the old load without
4651 * adding any new load.
4653 static unsigned long
4654 decay_load_missed(unsigned long load
, unsigned long missed_updates
, int idx
)
4658 if (!missed_updates
)
4661 if (missed_updates
>= degrade_zero_ticks
[idx
])
4665 return load
>> missed_updates
;
4667 while (missed_updates
) {
4668 if (missed_updates
% 2)
4669 load
= (load
* degrade_factor
[idx
][j
]) >> DEGRADE_SHIFT
;
4671 missed_updates
>>= 1;
4676 #endif /* CONFIG_NO_HZ_COMMON */
4679 * __cpu_load_update - update the rq->cpu_load[] statistics
4680 * @this_rq: The rq to update statistics for
4681 * @this_load: The current load
4682 * @pending_updates: The number of missed updates
4684 * Update rq->cpu_load[] statistics. This function is usually called every
4685 * scheduler tick (TICK_NSEC).
4687 * This function computes a decaying average:
4689 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
4691 * Because of NOHZ it might not get called on every tick which gives need for
4692 * the @pending_updates argument.
4694 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
4695 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
4696 * = A * (A * load[i]_n-2 + B) + B
4697 * = A * (A * (A * load[i]_n-3 + B) + B) + B
4698 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
4699 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
4700 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
4701 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
4703 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
4704 * any change in load would have resulted in the tick being turned back on.
4706 * For regular NOHZ, this reduces to:
4708 * load[i]_n = (1 - 1/2^i)^n * load[i]_0
4710 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4713 static void cpu_load_update(struct rq
*this_rq
, unsigned long this_load
,
4714 unsigned long pending_updates
)
4716 unsigned long __maybe_unused tickless_load
= this_rq
->cpu_load
[0];
4719 this_rq
->nr_load_updates
++;
4721 /* Update our load: */
4722 this_rq
->cpu_load
[0] = this_load
; /* Fasttrack for idx 0 */
4723 for (i
= 1, scale
= 2; i
< CPU_LOAD_IDX_MAX
; i
++, scale
+= scale
) {
4724 unsigned long old_load
, new_load
;
4726 /* scale is effectively 1 << i now, and >> i divides by scale */
4728 old_load
= this_rq
->cpu_load
[i
];
4729 #ifdef CONFIG_NO_HZ_COMMON
4730 old_load
= decay_load_missed(old_load
, pending_updates
- 1, i
);
4731 if (tickless_load
) {
4732 old_load
-= decay_load_missed(tickless_load
, pending_updates
- 1, i
);
4734 * old_load can never be a negative value because a
4735 * decayed tickless_load cannot be greater than the
4736 * original tickless_load.
4738 old_load
+= tickless_load
;
4741 new_load
= this_load
;
4743 * Round up the averaging division if load is increasing. This
4744 * prevents us from getting stuck on 9 if the load is 10, for
4747 if (new_load
> old_load
)
4748 new_load
+= scale
- 1;
4750 this_rq
->cpu_load
[i
] = (old_load
* (scale
- 1) + new_load
) >> i
;
4753 sched_avg_update(this_rq
);
4756 /* Used instead of source_load when we know the type == 0 */
4757 static unsigned long weighted_cpuload(const int cpu
)
4759 return cfs_rq_runnable_load_avg(&cpu_rq(cpu
)->cfs
);
4762 #ifdef CONFIG_NO_HZ_COMMON
4764 * There is no sane way to deal with nohz on smp when using jiffies because the
4765 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
4766 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
4768 * Therefore we need to avoid the delta approach from the regular tick when
4769 * possible since that would seriously skew the load calculation. This is why we
4770 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
4771 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
4772 * loop exit, nohz_idle_balance, nohz full exit...)
4774 * This means we might still be one tick off for nohz periods.
4777 static void cpu_load_update_nohz(struct rq
*this_rq
,
4778 unsigned long curr_jiffies
,
4781 unsigned long pending_updates
;
4783 pending_updates
= curr_jiffies
- this_rq
->last_load_update_tick
;
4784 if (pending_updates
) {
4785 this_rq
->last_load_update_tick
= curr_jiffies
;
4787 * In the regular NOHZ case, we were idle, this means load 0.
4788 * In the NOHZ_FULL case, we were non-idle, we should consider
4789 * its weighted load.
4791 cpu_load_update(this_rq
, load
, pending_updates
);
4796 * Called from nohz_idle_balance() to update the load ratings before doing the
4799 static void cpu_load_update_idle(struct rq
*this_rq
)
4802 * bail if there's load or we're actually up-to-date.
4804 if (weighted_cpuload(cpu_of(this_rq
)))
4807 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), 0);
4811 * Record CPU load on nohz entry so we know the tickless load to account
4812 * on nohz exit. cpu_load[0] happens then to be updated more frequently
4813 * than other cpu_load[idx] but it should be fine as cpu_load readers
4814 * shouldn't rely into synchronized cpu_load[*] updates.
4816 void cpu_load_update_nohz_start(void)
4818 struct rq
*this_rq
= this_rq();
4821 * This is all lockless but should be fine. If weighted_cpuload changes
4822 * concurrently we'll exit nohz. And cpu_load write can race with
4823 * cpu_load_update_idle() but both updater would be writing the same.
4825 this_rq
->cpu_load
[0] = weighted_cpuload(cpu_of(this_rq
));
4829 * Account the tickless load in the end of a nohz frame.
4831 void cpu_load_update_nohz_stop(void)
4833 unsigned long curr_jiffies
= READ_ONCE(jiffies
);
4834 struct rq
*this_rq
= this_rq();
4837 if (curr_jiffies
== this_rq
->last_load_update_tick
)
4840 load
= weighted_cpuload(cpu_of(this_rq
));
4841 raw_spin_lock(&this_rq
->lock
);
4842 update_rq_clock(this_rq
);
4843 cpu_load_update_nohz(this_rq
, curr_jiffies
, load
);
4844 raw_spin_unlock(&this_rq
->lock
);
4846 #else /* !CONFIG_NO_HZ_COMMON */
4847 static inline void cpu_load_update_nohz(struct rq
*this_rq
,
4848 unsigned long curr_jiffies
,
4849 unsigned long load
) { }
4850 #endif /* CONFIG_NO_HZ_COMMON */
4852 static void cpu_load_update_periodic(struct rq
*this_rq
, unsigned long load
)
4854 #ifdef CONFIG_NO_HZ_COMMON
4855 /* See the mess around cpu_load_update_nohz(). */
4856 this_rq
->last_load_update_tick
= READ_ONCE(jiffies
);
4858 cpu_load_update(this_rq
, load
, 1);
4862 * Called from scheduler_tick()
4864 void cpu_load_update_active(struct rq
*this_rq
)
4866 unsigned long load
= weighted_cpuload(cpu_of(this_rq
));
4868 if (tick_nohz_tick_stopped())
4869 cpu_load_update_nohz(this_rq
, READ_ONCE(jiffies
), load
);
4871 cpu_load_update_periodic(this_rq
, load
);
4875 * Return a low guess at the load of a migration-source cpu weighted
4876 * according to the scheduling class and "nice" value.
4878 * We want to under-estimate the load of migration sources, to
4879 * balance conservatively.
4881 static unsigned long source_load(int cpu
, int type
)
4883 struct rq
*rq
= cpu_rq(cpu
);
4884 unsigned long total
= weighted_cpuload(cpu
);
4886 if (type
== 0 || !sched_feat(LB_BIAS
))
4889 return min(rq
->cpu_load
[type
-1], total
);
4893 * Return a high guess at the load of a migration-target cpu weighted
4894 * according to the scheduling class and "nice" value.
4896 static unsigned long target_load(int cpu
, int type
)
4898 struct rq
*rq
= cpu_rq(cpu
);
4899 unsigned long total
= weighted_cpuload(cpu
);
4901 if (type
== 0 || !sched_feat(LB_BIAS
))
4904 return max(rq
->cpu_load
[type
-1], total
);
4907 static unsigned long capacity_of(int cpu
)
4909 return cpu_rq(cpu
)->cpu_capacity
;
4912 static unsigned long capacity_orig_of(int cpu
)
4914 return cpu_rq(cpu
)->cpu_capacity_orig
;
4917 static unsigned long cpu_avg_load_per_task(int cpu
)
4919 struct rq
*rq
= cpu_rq(cpu
);
4920 unsigned long nr_running
= READ_ONCE(rq
->cfs
.h_nr_running
);
4921 unsigned long load_avg
= weighted_cpuload(cpu
);
4924 return load_avg
/ nr_running
;
4929 #ifdef CONFIG_FAIR_GROUP_SCHED
4931 * effective_load() calculates the load change as seen from the root_task_group
4933 * Adding load to a group doesn't make a group heavier, but can cause movement
4934 * of group shares between cpus. Assuming the shares were perfectly aligned one
4935 * can calculate the shift in shares.
4937 * Calculate the effective load difference if @wl is added (subtracted) to @tg
4938 * on this @cpu and results in a total addition (subtraction) of @wg to the
4939 * total group weight.
4941 * Given a runqueue weight distribution (rw_i) we can compute a shares
4942 * distribution (s_i) using:
4944 * s_i = rw_i / \Sum rw_j (1)
4946 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
4947 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
4948 * shares distribution (s_i):
4950 * rw_i = { 2, 4, 1, 0 }
4951 * s_i = { 2/7, 4/7, 1/7, 0 }
4953 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
4954 * task used to run on and the CPU the waker is running on), we need to
4955 * compute the effect of waking a task on either CPU and, in case of a sync
4956 * wakeup, compute the effect of the current task going to sleep.
4958 * So for a change of @wl to the local @cpu with an overall group weight change
4959 * of @wl we can compute the new shares distribution (s'_i) using:
4961 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2)
4963 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
4964 * differences in waking a task to CPU 0. The additional task changes the
4965 * weight and shares distributions like:
4967 * rw'_i = { 3, 4, 1, 0 }
4968 * s'_i = { 3/8, 4/8, 1/8, 0 }
4970 * We can then compute the difference in effective weight by using:
4972 * dw_i = S * (s'_i - s_i) (3)
4974 * Where 'S' is the group weight as seen by its parent.
4976 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
4977 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
4978 * 4/7) times the weight of the group.
4980 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
4982 struct sched_entity
*se
= tg
->se
[cpu
];
4984 if (!tg
->parent
) /* the trivial, non-cgroup case */
4987 for_each_sched_entity(se
) {
4988 struct cfs_rq
*cfs_rq
= se
->my_q
;
4989 long W
, w
= cfs_rq_load_avg(cfs_rq
);
4994 * W = @wg + \Sum rw_j
4996 W
= wg
+ atomic_long_read(&tg
->load_avg
);
4998 /* Ensure \Sum rw_j >= rw_i */
4999 W
-= cfs_rq
->tg_load_avg_contrib
;
5008 * wl = S * s'_i; see (2)
5011 wl
= (w
* (long)tg
->shares
) / W
;
5016 * Per the above, wl is the new se->load.weight value; since
5017 * those are clipped to [MIN_SHARES, ...) do so now. See
5018 * calc_cfs_shares().
5020 if (wl
< MIN_SHARES
)
5024 * wl = dw_i = S * (s'_i - s_i); see (3)
5026 wl
-= se
->avg
.load_avg
;
5029 * Recursively apply this logic to all parent groups to compute
5030 * the final effective load change on the root group. Since
5031 * only the @tg group gets extra weight, all parent groups can
5032 * only redistribute existing shares. @wl is the shift in shares
5033 * resulting from this level per the above.
5042 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
5049 static void record_wakee(struct task_struct
*p
)
5052 * Only decay a single time; tasks that have less then 1 wakeup per
5053 * jiffy will not have built up many flips.
5055 if (time_after(jiffies
, current
->wakee_flip_decay_ts
+ HZ
)) {
5056 current
->wakee_flips
>>= 1;
5057 current
->wakee_flip_decay_ts
= jiffies
;
5060 if (current
->last_wakee
!= p
) {
5061 current
->last_wakee
= p
;
5062 current
->wakee_flips
++;
5067 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
5069 * A waker of many should wake a different task than the one last awakened
5070 * at a frequency roughly N times higher than one of its wakees.
5072 * In order to determine whether we should let the load spread vs consolidating
5073 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
5074 * partner, and a factor of lls_size higher frequency in the other.
5076 * With both conditions met, we can be relatively sure that the relationship is
5077 * non-monogamous, with partner count exceeding socket size.
5079 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
5080 * whatever is irrelevant, spread criteria is apparent partner count exceeds
5083 static int wake_wide(struct task_struct
*p
)
5085 unsigned int master
= current
->wakee_flips
;
5086 unsigned int slave
= p
->wakee_flips
;
5087 int factor
= this_cpu_read(sd_llc_size
);
5090 swap(master
, slave
);
5091 if (slave
< factor
|| master
< slave
* factor
)
5096 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
,
5097 int prev_cpu
, int sync
)
5099 s64 this_load
, load
;
5100 s64 this_eff_load
, prev_eff_load
;
5102 struct task_group
*tg
;
5103 unsigned long weight
;
5107 this_cpu
= smp_processor_id();
5108 load
= source_load(prev_cpu
, idx
);
5109 this_load
= target_load(this_cpu
, idx
);
5112 * If sync wakeup then subtract the (maximum possible)
5113 * effect of the currently running task from the load
5114 * of the current CPU:
5117 tg
= task_group(current
);
5118 weight
= current
->se
.avg
.load_avg
;
5120 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
5121 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
5125 weight
= p
->se
.avg
.load_avg
;
5128 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5129 * due to the sync cause above having dropped this_load to 0, we'll
5130 * always have an imbalance, but there's really nothing you can do
5131 * about that, so that's good too.
5133 * Otherwise check if either cpus are near enough in load to allow this
5134 * task to be woken on this_cpu.
5136 this_eff_load
= 100;
5137 this_eff_load
*= capacity_of(prev_cpu
);
5139 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
5140 prev_eff_load
*= capacity_of(this_cpu
);
5142 if (this_load
> 0) {
5143 this_eff_load
*= this_load
+
5144 effective_load(tg
, this_cpu
, weight
, weight
);
5146 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
5149 balanced
= this_eff_load
<= prev_eff_load
;
5151 schedstat_inc(p
->se
.statistics
.nr_wakeups_affine_attempts
);
5156 schedstat_inc(sd
->ttwu_move_affine
);
5157 schedstat_inc(p
->se
.statistics
.nr_wakeups_affine
);
5163 * find_idlest_group finds and returns the least busy CPU group within the
5166 static struct sched_group
*
5167 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
5168 int this_cpu
, int sd_flag
)
5170 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
5171 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
5172 int load_idx
= sd
->forkexec_idx
;
5173 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
5175 if (sd_flag
& SD_BALANCE_WAKE
)
5176 load_idx
= sd
->wake_idx
;
5179 unsigned long load
, avg_load
;
5183 /* Skip over this group if it has no CPUs allowed */
5184 if (!cpumask_intersects(sched_group_cpus(group
),
5185 tsk_cpus_allowed(p
)))
5188 local_group
= cpumask_test_cpu(this_cpu
,
5189 sched_group_cpus(group
));
5191 /* Tally up the load of all CPUs in the group */
5194 for_each_cpu(i
, sched_group_cpus(group
)) {
5195 /* Bias balancing toward cpus of our domain */
5197 load
= source_load(i
, load_idx
);
5199 load
= target_load(i
, load_idx
);
5204 /* Adjust by relative CPU capacity of the group */
5205 avg_load
= (avg_load
* SCHED_CAPACITY_SCALE
) / group
->sgc
->capacity
;
5208 this_load
= avg_load
;
5209 } else if (avg_load
< min_load
) {
5210 min_load
= avg_load
;
5213 } while (group
= group
->next
, group
!= sd
->groups
);
5215 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
5221 * find_idlest_cpu - find the idlest cpu among the cpus in group.
5224 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
5226 unsigned long load
, min_load
= ULONG_MAX
;
5227 unsigned int min_exit_latency
= UINT_MAX
;
5228 u64 latest_idle_timestamp
= 0;
5229 int least_loaded_cpu
= this_cpu
;
5230 int shallowest_idle_cpu
= -1;
5233 /* Check if we have any choice: */
5234 if (group
->group_weight
== 1)
5235 return cpumask_first(sched_group_cpus(group
));
5237 /* Traverse only the allowed CPUs */
5238 for_each_cpu_and(i
, sched_group_cpus(group
), tsk_cpus_allowed(p
)) {
5240 struct rq
*rq
= cpu_rq(i
);
5241 struct cpuidle_state
*idle
= idle_get_state(rq
);
5242 if (idle
&& idle
->exit_latency
< min_exit_latency
) {
5244 * We give priority to a CPU whose idle state
5245 * has the smallest exit latency irrespective
5246 * of any idle timestamp.
5248 min_exit_latency
= idle
->exit_latency
;
5249 latest_idle_timestamp
= rq
->idle_stamp
;
5250 shallowest_idle_cpu
= i
;
5251 } else if ((!idle
|| idle
->exit_latency
== min_exit_latency
) &&
5252 rq
->idle_stamp
> latest_idle_timestamp
) {
5254 * If equal or no active idle state, then
5255 * the most recently idled CPU might have
5258 latest_idle_timestamp
= rq
->idle_stamp
;
5259 shallowest_idle_cpu
= i
;
5261 } else if (shallowest_idle_cpu
== -1) {
5262 load
= weighted_cpuload(i
);
5263 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
5265 least_loaded_cpu
= i
;
5270 return shallowest_idle_cpu
!= -1 ? shallowest_idle_cpu
: least_loaded_cpu
;
5274 * Try and locate an idle CPU in the sched_domain.
5276 static int select_idle_sibling(struct task_struct
*p
, int prev
, int target
)
5278 struct sched_domain
*sd
;
5279 struct sched_group
*sg
;
5281 if (idle_cpu(target
))
5285 * If the prevous cpu is cache affine and idle, don't be stupid.
5287 if (prev
!= target
&& cpus_share_cache(prev
, target
) && idle_cpu(prev
))
5291 * Otherwise, iterate the domains and find an eligible idle cpu.
5293 * A completely idle sched group at higher domains is more
5294 * desirable than an idle group at a lower level, because lower
5295 * domains have smaller groups and usually share hardware
5296 * resources which causes tasks to contend on them, e.g. x86
5297 * hyperthread siblings in the lowest domain (SMT) can contend
5298 * on the shared cpu pipeline.
5300 * However, while we prefer idle groups at higher domains
5301 * finding an idle cpu at the lowest domain is still better than
5302 * returning 'target', which we've already established, isn't
5305 sd
= rcu_dereference(per_cpu(sd_llc
, target
));
5306 for_each_lower_domain(sd
) {
5311 if (!cpumask_intersects(sched_group_cpus(sg
),
5312 tsk_cpus_allowed(p
)))
5315 /* Ensure the entire group is idle */
5316 for_each_cpu(i
, sched_group_cpus(sg
)) {
5317 if (i
== target
|| !idle_cpu(i
))
5322 * It doesn't matter which cpu we pick, the
5323 * whole group is idle.
5325 target
= cpumask_first_and(sched_group_cpus(sg
),
5326 tsk_cpus_allowed(p
));
5330 } while (sg
!= sd
->groups
);
5337 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5338 * tasks. The unit of the return value must be the one of capacity so we can
5339 * compare the utilization with the capacity of the CPU that is available for
5340 * CFS task (ie cpu_capacity).
5342 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
5343 * recent utilization of currently non-runnable tasks on a CPU. It represents
5344 * the amount of utilization of a CPU in the range [0..capacity_orig] where
5345 * capacity_orig is the cpu_capacity available at the highest frequency
5346 * (arch_scale_freq_capacity()).
5347 * The utilization of a CPU converges towards a sum equal to or less than the
5348 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
5349 * the running time on this CPU scaled by capacity_curr.
5351 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
5352 * higher than capacity_orig because of unfortunate rounding in
5353 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
5354 * the average stabilizes with the new running time. We need to check that the
5355 * utilization stays within the range of [0..capacity_orig] and cap it if
5356 * necessary. Without utilization capping, a group could be seen as overloaded
5357 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
5358 * available capacity. We allow utilization to overshoot capacity_curr (but not
5359 * capacity_orig) as it useful for predicting the capacity required after task
5360 * migrations (scheduler-driven DVFS).
5362 static int cpu_util(int cpu
)
5364 unsigned long util
= cpu_rq(cpu
)->cfs
.avg
.util_avg
;
5365 unsigned long capacity
= capacity_orig_of(cpu
);
5367 return (util
>= capacity
) ? capacity
: util
;
5370 static inline int task_util(struct task_struct
*p
)
5372 return p
->se
.avg
.util_avg
;
5376 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
5377 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
5379 * In that case WAKE_AFFINE doesn't make sense and we'll let
5380 * BALANCE_WAKE sort things out.
5382 static int wake_cap(struct task_struct
*p
, int cpu
, int prev_cpu
)
5384 long min_cap
, max_cap
;
5386 min_cap
= min(capacity_orig_of(prev_cpu
), capacity_orig_of(cpu
));
5387 max_cap
= cpu_rq(cpu
)->rd
->max_cpu_capacity
;
5389 /* Minimum capacity is close to max, no need to abort wake_affine */
5390 if (max_cap
- min_cap
< max_cap
>> 3)
5393 return min_cap
* 1024 < task_util(p
) * capacity_margin
;
5397 * select_task_rq_fair: Select target runqueue for the waking task in domains
5398 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
5399 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
5401 * Balances load by selecting the idlest cpu in the idlest group, or under
5402 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set.
5404 * Returns the target cpu number.
5406 * preempt must be disabled.
5409 select_task_rq_fair(struct task_struct
*p
, int prev_cpu
, int sd_flag
, int wake_flags
)
5411 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
5412 int cpu
= smp_processor_id();
5413 int new_cpu
= prev_cpu
;
5414 int want_affine
= 0;
5415 int sync
= wake_flags
& WF_SYNC
;
5417 if (sd_flag
& SD_BALANCE_WAKE
) {
5419 want_affine
= !wake_wide(p
) && !wake_cap(p
, cpu
, prev_cpu
)
5420 && cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
));
5424 for_each_domain(cpu
, tmp
) {
5425 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
5429 * If both cpu and prev_cpu are part of this domain,
5430 * cpu is a valid SD_WAKE_AFFINE target.
5432 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
5433 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
5438 if (tmp
->flags
& sd_flag
)
5440 else if (!want_affine
)
5445 sd
= NULL
; /* Prefer wake_affine over balance flags */
5446 if (cpu
!= prev_cpu
&& wake_affine(affine_sd
, p
, prev_cpu
, sync
))
5451 if (sd_flag
& SD_BALANCE_WAKE
) /* XXX always ? */
5452 new_cpu
= select_idle_sibling(p
, prev_cpu
, new_cpu
);
5455 struct sched_group
*group
;
5458 if (!(sd
->flags
& sd_flag
)) {
5463 group
= find_idlest_group(sd
, p
, cpu
, sd_flag
);
5469 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
5470 if (new_cpu
== -1 || new_cpu
== cpu
) {
5471 /* Now try balancing at a lower domain level of cpu */
5476 /* Now try balancing at a lower domain level of new_cpu */
5478 weight
= sd
->span_weight
;
5480 for_each_domain(cpu
, tmp
) {
5481 if (weight
<= tmp
->span_weight
)
5483 if (tmp
->flags
& sd_flag
)
5486 /* while loop will break here if sd == NULL */
5494 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
5495 * cfs_rq_of(p) references at time of call are still valid and identify the
5496 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5498 static void migrate_task_rq_fair(struct task_struct
*p
)
5501 * As blocked tasks retain absolute vruntime the migration needs to
5502 * deal with this by subtracting the old and adding the new
5503 * min_vruntime -- the latter is done by enqueue_entity() when placing
5504 * the task on the new runqueue.
5506 if (p
->state
== TASK_WAKING
) {
5507 struct sched_entity
*se
= &p
->se
;
5508 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
5511 #ifndef CONFIG_64BIT
5512 u64 min_vruntime_copy
;
5515 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
5517 min_vruntime
= cfs_rq
->min_vruntime
;
5518 } while (min_vruntime
!= min_vruntime_copy
);
5520 min_vruntime
= cfs_rq
->min_vruntime
;
5523 se
->vruntime
-= min_vruntime
;
5527 * We are supposed to update the task to "current" time, then its up to date
5528 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
5529 * what current time is, so simply throw away the out-of-date time. This
5530 * will result in the wakee task is less decayed, but giving the wakee more
5531 * load sounds not bad.
5533 remove_entity_load_avg(&p
->se
);
5535 /* Tell new CPU we are migrated */
5536 p
->se
.avg
.last_update_time
= 0;
5538 /* We have migrated, no longer consider this task hot */
5539 p
->se
.exec_start
= 0;
5542 static void task_dead_fair(struct task_struct
*p
)
5544 remove_entity_load_avg(&p
->se
);
5546 #endif /* CONFIG_SMP */
5548 static unsigned long
5549 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
5551 unsigned long gran
= sysctl_sched_wakeup_granularity
;
5554 * Since its curr running now, convert the gran from real-time
5555 * to virtual-time in his units.
5557 * By using 'se' instead of 'curr' we penalize light tasks, so
5558 * they get preempted easier. That is, if 'se' < 'curr' then
5559 * the resulting gran will be larger, therefore penalizing the
5560 * lighter, if otoh 'se' > 'curr' then the resulting gran will
5561 * be smaller, again penalizing the lighter task.
5563 * This is especially important for buddies when the leftmost
5564 * task is higher priority than the buddy.
5566 return calc_delta_fair(gran
, se
);
5570 * Should 'se' preempt 'curr'.
5584 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
5586 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
5591 gran
= wakeup_gran(curr
, se
);
5598 static void set_last_buddy(struct sched_entity
*se
)
5600 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5603 for_each_sched_entity(se
)
5604 cfs_rq_of(se
)->last
= se
;
5607 static void set_next_buddy(struct sched_entity
*se
)
5609 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
5612 for_each_sched_entity(se
)
5613 cfs_rq_of(se
)->next
= se
;
5616 static void set_skip_buddy(struct sched_entity
*se
)
5618 for_each_sched_entity(se
)
5619 cfs_rq_of(se
)->skip
= se
;
5623 * Preempt the current task with a newly woken task if needed:
5625 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
5627 struct task_struct
*curr
= rq
->curr
;
5628 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
5629 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5630 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
5631 int next_buddy_marked
= 0;
5633 if (unlikely(se
== pse
))
5637 * This is possible from callers such as attach_tasks(), in which we
5638 * unconditionally check_prempt_curr() after an enqueue (which may have
5639 * lead to a throttle). This both saves work and prevents false
5640 * next-buddy nomination below.
5642 if (unlikely(throttled_hierarchy(cfs_rq_of(pse
))))
5645 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
5646 set_next_buddy(pse
);
5647 next_buddy_marked
= 1;
5651 * We can come here with TIF_NEED_RESCHED already set from new task
5654 * Note: this also catches the edge-case of curr being in a throttled
5655 * group (e.g. via set_curr_task), since update_curr() (in the
5656 * enqueue of curr) will have resulted in resched being set. This
5657 * prevents us from potentially nominating it as a false LAST_BUDDY
5660 if (test_tsk_need_resched(curr
))
5663 /* Idle tasks are by definition preempted by non-idle tasks. */
5664 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
5665 likely(p
->policy
!= SCHED_IDLE
))
5669 * Batch and idle tasks do not preempt non-idle tasks (their preemption
5670 * is driven by the tick):
5672 if (unlikely(p
->policy
!= SCHED_NORMAL
) || !sched_feat(WAKEUP_PREEMPTION
))
5675 find_matching_se(&se
, &pse
);
5676 update_curr(cfs_rq_of(se
));
5678 if (wakeup_preempt_entity(se
, pse
) == 1) {
5680 * Bias pick_next to pick the sched entity that is
5681 * triggering this preemption.
5683 if (!next_buddy_marked
)
5684 set_next_buddy(pse
);
5693 * Only set the backward buddy when the current task is still
5694 * on the rq. This can happen when a wakeup gets interleaved
5695 * with schedule on the ->pre_schedule() or idle_balance()
5696 * point, either of which can * drop the rq lock.
5698 * Also, during early boot the idle thread is in the fair class,
5699 * for obvious reasons its a bad idea to schedule back to it.
5701 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
5704 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
5708 static struct task_struct
*
5709 pick_next_task_fair(struct rq
*rq
, struct task_struct
*prev
, struct pin_cookie cookie
)
5711 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
5712 struct sched_entity
*se
;
5713 struct task_struct
*p
;
5717 #ifdef CONFIG_FAIR_GROUP_SCHED
5718 if (!cfs_rq
->nr_running
)
5721 if (prev
->sched_class
!= &fair_sched_class
)
5725 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
5726 * likely that a next task is from the same cgroup as the current.
5728 * Therefore attempt to avoid putting and setting the entire cgroup
5729 * hierarchy, only change the part that actually changes.
5733 struct sched_entity
*curr
= cfs_rq
->curr
;
5736 * Since we got here without doing put_prev_entity() we also
5737 * have to consider cfs_rq->curr. If it is still a runnable
5738 * entity, update_curr() will update its vruntime, otherwise
5739 * forget we've ever seen it.
5743 update_curr(cfs_rq
);
5748 * This call to check_cfs_rq_runtime() will do the
5749 * throttle and dequeue its entity in the parent(s).
5750 * Therefore the 'simple' nr_running test will indeed
5753 if (unlikely(check_cfs_rq_runtime(cfs_rq
)))
5757 se
= pick_next_entity(cfs_rq
, curr
);
5758 cfs_rq
= group_cfs_rq(se
);
5764 * Since we haven't yet done put_prev_entity and if the selected task
5765 * is a different task than we started out with, try and touch the
5766 * least amount of cfs_rqs.
5769 struct sched_entity
*pse
= &prev
->se
;
5771 while (!(cfs_rq
= is_same_group(se
, pse
))) {
5772 int se_depth
= se
->depth
;
5773 int pse_depth
= pse
->depth
;
5775 if (se_depth
<= pse_depth
) {
5776 put_prev_entity(cfs_rq_of(pse
), pse
);
5777 pse
= parent_entity(pse
);
5779 if (se_depth
>= pse_depth
) {
5780 set_next_entity(cfs_rq_of(se
), se
);
5781 se
= parent_entity(se
);
5785 put_prev_entity(cfs_rq
, pse
);
5786 set_next_entity(cfs_rq
, se
);
5789 if (hrtick_enabled(rq
))
5790 hrtick_start_fair(rq
, p
);
5797 if (!cfs_rq
->nr_running
)
5800 put_prev_task(rq
, prev
);
5803 se
= pick_next_entity(cfs_rq
, NULL
);
5804 set_next_entity(cfs_rq
, se
);
5805 cfs_rq
= group_cfs_rq(se
);
5810 if (hrtick_enabled(rq
))
5811 hrtick_start_fair(rq
, p
);
5817 * This is OK, because current is on_cpu, which avoids it being picked
5818 * for load-balance and preemption/IRQs are still disabled avoiding
5819 * further scheduler activity on it and we're being very careful to
5820 * re-start the picking loop.
5822 lockdep_unpin_lock(&rq
->lock
, cookie
);
5823 new_tasks
= idle_balance(rq
);
5824 lockdep_repin_lock(&rq
->lock
, cookie
);
5826 * Because idle_balance() releases (and re-acquires) rq->lock, it is
5827 * possible for any higher priority task to appear. In that case we
5828 * must re-start the pick_next_entity() loop.
5840 * Account for a descheduled task:
5842 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
5844 struct sched_entity
*se
= &prev
->se
;
5845 struct cfs_rq
*cfs_rq
;
5847 for_each_sched_entity(se
) {
5848 cfs_rq
= cfs_rq_of(se
);
5849 put_prev_entity(cfs_rq
, se
);
5854 * sched_yield() is very simple
5856 * The magic of dealing with the ->skip buddy is in pick_next_entity.
5858 static void yield_task_fair(struct rq
*rq
)
5860 struct task_struct
*curr
= rq
->curr
;
5861 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
5862 struct sched_entity
*se
= &curr
->se
;
5865 * Are we the only task in the tree?
5867 if (unlikely(rq
->nr_running
== 1))
5870 clear_buddies(cfs_rq
, se
);
5872 if (curr
->policy
!= SCHED_BATCH
) {
5873 update_rq_clock(rq
);
5875 * Update run-time statistics of the 'current'.
5877 update_curr(cfs_rq
);
5879 * Tell update_rq_clock() that we've just updated,
5880 * so we don't do microscopic update in schedule()
5881 * and double the fastpath cost.
5883 rq_clock_skip_update(rq
, true);
5889 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
5891 struct sched_entity
*se
= &p
->se
;
5893 /* throttled hierarchies are not runnable */
5894 if (!se
->on_rq
|| throttled_hierarchy(cfs_rq_of(se
)))
5897 /* Tell the scheduler that we'd really like pse to run next. */
5900 yield_task_fair(rq
);
5906 /**************************************************
5907 * Fair scheduling class load-balancing methods.
5911 * The purpose of load-balancing is to achieve the same basic fairness the
5912 * per-cpu scheduler provides, namely provide a proportional amount of compute
5913 * time to each task. This is expressed in the following equation:
5915 * W_i,n/P_i == W_j,n/P_j for all i,j (1)
5917 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
5918 * W_i,0 is defined as:
5920 * W_i,0 = \Sum_j w_i,j (2)
5922 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
5923 * is derived from the nice value as per sched_prio_to_weight[].
5925 * The weight average is an exponential decay average of the instantaneous
5928 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3)
5930 * C_i is the compute capacity of cpu i, typically it is the
5931 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
5932 * can also include other factors [XXX].
5934 * To achieve this balance we define a measure of imbalance which follows
5935 * directly from (1):
5937 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4)
5939 * We them move tasks around to minimize the imbalance. In the continuous
5940 * function space it is obvious this converges, in the discrete case we get
5941 * a few fun cases generally called infeasible weight scenarios.
5944 * - infeasible weights;
5945 * - local vs global optima in the discrete case. ]
5950 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
5951 * for all i,j solution, we create a tree of cpus that follows the hardware
5952 * topology where each level pairs two lower groups (or better). This results
5953 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
5954 * tree to only the first of the previous level and we decrease the frequency
5955 * of load-balance at each level inv. proportional to the number of cpus in
5961 * \Sum { --- * --- * 2^i } = O(n) (5)
5963 * `- size of each group
5964 * | | `- number of cpus doing load-balance
5966 * `- sum over all levels
5968 * Coupled with a limit on how many tasks we can migrate every balance pass,
5969 * this makes (5) the runtime complexity of the balancer.
5971 * An important property here is that each CPU is still (indirectly) connected
5972 * to every other cpu in at most O(log n) steps:
5974 * The adjacency matrix of the resulting graph is given by:
5977 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6)
5980 * And you'll find that:
5982 * A^(log_2 n)_i,j != 0 for all i,j (7)
5984 * Showing there's indeed a path between every cpu in at most O(log n) steps.
5985 * The task movement gives a factor of O(m), giving a convergence complexity
5988 * O(nm log n), n := nr_cpus, m := nr_tasks (8)
5993 * In order to avoid CPUs going idle while there's still work to do, new idle
5994 * balancing is more aggressive and has the newly idle cpu iterate up the domain
5995 * tree itself instead of relying on other CPUs to bring it work.
5997 * This adds some complexity to both (5) and (8) but it reduces the total idle
6005 * Cgroups make a horror show out of (2), instead of a simple sum we get:
6008 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9)
6013 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10)
6015 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
6017 * The big problem is S_k, its a global sum needed to compute a local (W_i)
6020 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
6021 * rewrite all of this once again.]
6024 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
6026 enum fbq_type
{ regular
, remote
, all
};
6028 #define LBF_ALL_PINNED 0x01
6029 #define LBF_NEED_BREAK 0x02
6030 #define LBF_DST_PINNED 0x04
6031 #define LBF_SOME_PINNED 0x08
6034 struct sched_domain
*sd
;
6042 struct cpumask
*dst_grpmask
;
6044 enum cpu_idle_type idle
;
6046 /* The set of CPUs under consideration for load-balancing */
6047 struct cpumask
*cpus
;
6052 unsigned int loop_break
;
6053 unsigned int loop_max
;
6055 enum fbq_type fbq_type
;
6056 struct list_head tasks
;
6060 * Is this task likely cache-hot:
6062 static int task_hot(struct task_struct
*p
, struct lb_env
*env
)
6066 lockdep_assert_held(&env
->src_rq
->lock
);
6068 if (p
->sched_class
!= &fair_sched_class
)
6071 if (unlikely(p
->policy
== SCHED_IDLE
))
6075 * Buddy candidates are cache hot:
6077 if (sched_feat(CACHE_HOT_BUDDY
) && env
->dst_rq
->nr_running
&&
6078 (&p
->se
== cfs_rq_of(&p
->se
)->next
||
6079 &p
->se
== cfs_rq_of(&p
->se
)->last
))
6082 if (sysctl_sched_migration_cost
== -1)
6084 if (sysctl_sched_migration_cost
== 0)
6087 delta
= rq_clock_task(env
->src_rq
) - p
->se
.exec_start
;
6089 return delta
< (s64
)sysctl_sched_migration_cost
;
6092 #ifdef CONFIG_NUMA_BALANCING
6094 * Returns 1, if task migration degrades locality
6095 * Returns 0, if task migration improves locality i.e migration preferred.
6096 * Returns -1, if task migration is not affected by locality.
6098 static int migrate_degrades_locality(struct task_struct
*p
, struct lb_env
*env
)
6100 struct numa_group
*numa_group
= rcu_dereference(p
->numa_group
);
6101 unsigned long src_faults
, dst_faults
;
6102 int src_nid
, dst_nid
;
6104 if (!static_branch_likely(&sched_numa_balancing
))
6107 if (!p
->numa_faults
|| !(env
->sd
->flags
& SD_NUMA
))
6110 src_nid
= cpu_to_node(env
->src_cpu
);
6111 dst_nid
= cpu_to_node(env
->dst_cpu
);
6113 if (src_nid
== dst_nid
)
6116 /* Migrating away from the preferred node is always bad. */
6117 if (src_nid
== p
->numa_preferred_nid
) {
6118 if (env
->src_rq
->nr_running
> env
->src_rq
->nr_preferred_running
)
6124 /* Encourage migration to the preferred node. */
6125 if (dst_nid
== p
->numa_preferred_nid
)
6129 src_faults
= group_faults(p
, src_nid
);
6130 dst_faults
= group_faults(p
, dst_nid
);
6132 src_faults
= task_faults(p
, src_nid
);
6133 dst_faults
= task_faults(p
, dst_nid
);
6136 return dst_faults
< src_faults
;
6140 static inline int migrate_degrades_locality(struct task_struct
*p
,
6148 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
6151 int can_migrate_task(struct task_struct
*p
, struct lb_env
*env
)
6155 lockdep_assert_held(&env
->src_rq
->lock
);
6158 * We do not migrate tasks that are:
6159 * 1) throttled_lb_pair, or
6160 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6161 * 3) running (obviously), or
6162 * 4) are cache-hot on their current CPU.
6164 if (throttled_lb_pair(task_group(p
), env
->src_cpu
, env
->dst_cpu
))
6167 if (!cpumask_test_cpu(env
->dst_cpu
, tsk_cpus_allowed(p
))) {
6170 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_affine
);
6172 env
->flags
|= LBF_SOME_PINNED
;
6175 * Remember if this task can be migrated to any other cpu in
6176 * our sched_group. We may want to revisit it if we couldn't
6177 * meet load balance goals by pulling other tasks on src_cpu.
6179 * Also avoid computing new_dst_cpu if we have already computed
6180 * one in current iteration.
6182 if (!env
->dst_grpmask
|| (env
->flags
& LBF_DST_PINNED
))
6185 /* Prevent to re-select dst_cpu via env's cpus */
6186 for_each_cpu_and(cpu
, env
->dst_grpmask
, env
->cpus
) {
6187 if (cpumask_test_cpu(cpu
, tsk_cpus_allowed(p
))) {
6188 env
->flags
|= LBF_DST_PINNED
;
6189 env
->new_dst_cpu
= cpu
;
6197 /* Record that we found atleast one task that could run on dst_cpu */
6198 env
->flags
&= ~LBF_ALL_PINNED
;
6200 if (task_running(env
->src_rq
, p
)) {
6201 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_running
);
6206 * Aggressive migration if:
6207 * 1) destination numa is preferred
6208 * 2) task is cache cold, or
6209 * 3) too many balance attempts have failed.
6211 tsk_cache_hot
= migrate_degrades_locality(p
, env
);
6212 if (tsk_cache_hot
== -1)
6213 tsk_cache_hot
= task_hot(p
, env
);
6215 if (tsk_cache_hot
<= 0 ||
6216 env
->sd
->nr_balance_failed
> env
->sd
->cache_nice_tries
) {
6217 if (tsk_cache_hot
== 1) {
6218 schedstat_inc(env
->sd
->lb_hot_gained
[env
->idle
]);
6219 schedstat_inc(p
->se
.statistics
.nr_forced_migrations
);
6224 schedstat_inc(p
->se
.statistics
.nr_failed_migrations_hot
);
6229 * detach_task() -- detach the task for the migration specified in env
6231 static void detach_task(struct task_struct
*p
, struct lb_env
*env
)
6233 lockdep_assert_held(&env
->src_rq
->lock
);
6235 p
->on_rq
= TASK_ON_RQ_MIGRATING
;
6236 deactivate_task(env
->src_rq
, p
, 0);
6237 set_task_cpu(p
, env
->dst_cpu
);
6241 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6242 * part of active balancing operations within "domain".
6244 * Returns a task if successful and NULL otherwise.
6246 static struct task_struct
*detach_one_task(struct lb_env
*env
)
6248 struct task_struct
*p
, *n
;
6250 lockdep_assert_held(&env
->src_rq
->lock
);
6252 list_for_each_entry_safe(p
, n
, &env
->src_rq
->cfs_tasks
, se
.group_node
) {
6253 if (!can_migrate_task(p
, env
))
6256 detach_task(p
, env
);
6259 * Right now, this is only the second place where
6260 * lb_gained[env->idle] is updated (other is detach_tasks)
6261 * so we can safely collect stats here rather than
6262 * inside detach_tasks().
6264 schedstat_inc(env
->sd
->lb_gained
[env
->idle
]);
6270 static const unsigned int sched_nr_migrate_break
= 32;
6273 * detach_tasks() -- tries to detach up to imbalance weighted load from
6274 * busiest_rq, as part of a balancing operation within domain "sd".
6276 * Returns number of detached tasks if successful and 0 otherwise.
6278 static int detach_tasks(struct lb_env
*env
)
6280 struct list_head
*tasks
= &env
->src_rq
->cfs_tasks
;
6281 struct task_struct
*p
;
6285 lockdep_assert_held(&env
->src_rq
->lock
);
6287 if (env
->imbalance
<= 0)
6290 while (!list_empty(tasks
)) {
6292 * We don't want to steal all, otherwise we may be treated likewise,
6293 * which could at worst lead to a livelock crash.
6295 if (env
->idle
!= CPU_NOT_IDLE
&& env
->src_rq
->nr_running
<= 1)
6298 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6301 /* We've more or less seen every task there is, call it quits */
6302 if (env
->loop
> env
->loop_max
)
6305 /* take a breather every nr_migrate tasks */
6306 if (env
->loop
> env
->loop_break
) {
6307 env
->loop_break
+= sched_nr_migrate_break
;
6308 env
->flags
|= LBF_NEED_BREAK
;
6312 if (!can_migrate_task(p
, env
))
6315 load
= task_h_load(p
);
6317 if (sched_feat(LB_MIN
) && load
< 16 && !env
->sd
->nr_balance_failed
)
6320 if ((load
/ 2) > env
->imbalance
)
6323 detach_task(p
, env
);
6324 list_add(&p
->se
.group_node
, &env
->tasks
);
6327 env
->imbalance
-= load
;
6329 #ifdef CONFIG_PREEMPT
6331 * NEWIDLE balancing is a source of latency, so preemptible
6332 * kernels will stop after the first task is detached to minimize
6333 * the critical section.
6335 if (env
->idle
== CPU_NEWLY_IDLE
)
6340 * We only want to steal up to the prescribed amount of
6343 if (env
->imbalance
<= 0)
6348 list_move_tail(&p
->se
.group_node
, tasks
);
6352 * Right now, this is one of only two places we collect this stat
6353 * so we can safely collect detach_one_task() stats here rather
6354 * than inside detach_one_task().
6356 schedstat_add(env
->sd
->lb_gained
[env
->idle
], detached
);
6362 * attach_task() -- attach the task detached by detach_task() to its new rq.
6364 static void attach_task(struct rq
*rq
, struct task_struct
*p
)
6366 lockdep_assert_held(&rq
->lock
);
6368 BUG_ON(task_rq(p
) != rq
);
6369 activate_task(rq
, p
, 0);
6370 p
->on_rq
= TASK_ON_RQ_QUEUED
;
6371 check_preempt_curr(rq
, p
, 0);
6375 * attach_one_task() -- attaches the task returned from detach_one_task() to
6378 static void attach_one_task(struct rq
*rq
, struct task_struct
*p
)
6380 raw_spin_lock(&rq
->lock
);
6382 raw_spin_unlock(&rq
->lock
);
6386 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
6389 static void attach_tasks(struct lb_env
*env
)
6391 struct list_head
*tasks
= &env
->tasks
;
6392 struct task_struct
*p
;
6394 raw_spin_lock(&env
->dst_rq
->lock
);
6396 while (!list_empty(tasks
)) {
6397 p
= list_first_entry(tasks
, struct task_struct
, se
.group_node
);
6398 list_del_init(&p
->se
.group_node
);
6400 attach_task(env
->dst_rq
, p
);
6403 raw_spin_unlock(&env
->dst_rq
->lock
);
6406 #ifdef CONFIG_FAIR_GROUP_SCHED
6407 static void update_blocked_averages(int cpu
)
6409 struct rq
*rq
= cpu_rq(cpu
);
6410 struct cfs_rq
*cfs_rq
;
6411 unsigned long flags
;
6413 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6414 update_rq_clock(rq
);
6417 * Iterates the task_group tree in a bottom up fashion, see
6418 * list_add_leaf_cfs_rq() for details.
6420 for_each_leaf_cfs_rq(rq
, cfs_rq
) {
6421 /* throttled entities do not contribute to load */
6422 if (throttled_hierarchy(cfs_rq
))
6425 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true))
6426 update_tg_load_avg(cfs_rq
, 0);
6428 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6432 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6433 * This needs to be done in a top-down fashion because the load of a child
6434 * group is a fraction of its parents load.
6436 static void update_cfs_rq_h_load(struct cfs_rq
*cfs_rq
)
6438 struct rq
*rq
= rq_of(cfs_rq
);
6439 struct sched_entity
*se
= cfs_rq
->tg
->se
[cpu_of(rq
)];
6440 unsigned long now
= jiffies
;
6443 if (cfs_rq
->last_h_load_update
== now
)
6446 cfs_rq
->h_load_next
= NULL
;
6447 for_each_sched_entity(se
) {
6448 cfs_rq
= cfs_rq_of(se
);
6449 cfs_rq
->h_load_next
= se
;
6450 if (cfs_rq
->last_h_load_update
== now
)
6455 cfs_rq
->h_load
= cfs_rq_load_avg(cfs_rq
);
6456 cfs_rq
->last_h_load_update
= now
;
6459 while ((se
= cfs_rq
->h_load_next
) != NULL
) {
6460 load
= cfs_rq
->h_load
;
6461 load
= div64_ul(load
* se
->avg
.load_avg
,
6462 cfs_rq_load_avg(cfs_rq
) + 1);
6463 cfs_rq
= group_cfs_rq(se
);
6464 cfs_rq
->h_load
= load
;
6465 cfs_rq
->last_h_load_update
= now
;
6469 static unsigned long task_h_load(struct task_struct
*p
)
6471 struct cfs_rq
*cfs_rq
= task_cfs_rq(p
);
6473 update_cfs_rq_h_load(cfs_rq
);
6474 return div64_ul(p
->se
.avg
.load_avg
* cfs_rq
->h_load
,
6475 cfs_rq_load_avg(cfs_rq
) + 1);
6478 static inline void update_blocked_averages(int cpu
)
6480 struct rq
*rq
= cpu_rq(cpu
);
6481 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
6482 unsigned long flags
;
6484 raw_spin_lock_irqsave(&rq
->lock
, flags
);
6485 update_rq_clock(rq
);
6486 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq
), cfs_rq
, true);
6487 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
6490 static unsigned long task_h_load(struct task_struct
*p
)
6492 return p
->se
.avg
.load_avg
;
6496 /********** Helpers for find_busiest_group ************************/
6505 * sg_lb_stats - stats of a sched_group required for load_balancing
6507 struct sg_lb_stats
{
6508 unsigned long avg_load
; /*Avg load across the CPUs of the group */
6509 unsigned long group_load
; /* Total load over the CPUs of the group */
6510 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
6511 unsigned long load_per_task
;
6512 unsigned long group_capacity
;
6513 unsigned long group_util
; /* Total utilization of the group */
6514 unsigned int sum_nr_running
; /* Nr tasks running in the group */
6515 unsigned int idle_cpus
;
6516 unsigned int group_weight
;
6517 enum group_type group_type
;
6518 int group_no_capacity
;
6519 #ifdef CONFIG_NUMA_BALANCING
6520 unsigned int nr_numa_running
;
6521 unsigned int nr_preferred_running
;
6526 * sd_lb_stats - Structure to store the statistics of a sched_domain
6527 * during load balancing.
6529 struct sd_lb_stats
{
6530 struct sched_group
*busiest
; /* Busiest group in this sd */
6531 struct sched_group
*local
; /* Local group in this sd */
6532 unsigned long total_load
; /* Total load of all groups in sd */
6533 unsigned long total_capacity
; /* Total capacity of all groups in sd */
6534 unsigned long avg_load
; /* Average load across all groups in sd */
6536 struct sg_lb_stats busiest_stat
;/* Statistics of the busiest group */
6537 struct sg_lb_stats local_stat
; /* Statistics of the local group */
6540 static inline void init_sd_lb_stats(struct sd_lb_stats
*sds
)
6543 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
6544 * local_stat because update_sg_lb_stats() does a full clear/assignment.
6545 * We must however clear busiest_stat::avg_load because
6546 * update_sd_pick_busiest() reads this before assignment.
6548 *sds
= (struct sd_lb_stats
){
6552 .total_capacity
= 0UL,
6555 .sum_nr_running
= 0,
6556 .group_type
= group_other
,
6562 * get_sd_load_idx - Obtain the load index for a given sched domain.
6563 * @sd: The sched_domain whose load_idx is to be obtained.
6564 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6566 * Return: The load index.
6568 static inline int get_sd_load_idx(struct sched_domain
*sd
,
6569 enum cpu_idle_type idle
)
6575 load_idx
= sd
->busy_idx
;
6578 case CPU_NEWLY_IDLE
:
6579 load_idx
= sd
->newidle_idx
;
6582 load_idx
= sd
->idle_idx
;
6589 static unsigned long scale_rt_capacity(int cpu
)
6591 struct rq
*rq
= cpu_rq(cpu
);
6592 u64 total
, used
, age_stamp
, avg
;
6596 * Since we're reading these variables without serialization make sure
6597 * we read them once before doing sanity checks on them.
6599 age_stamp
= READ_ONCE(rq
->age_stamp
);
6600 avg
= READ_ONCE(rq
->rt_avg
);
6601 delta
= __rq_clock_broken(rq
) - age_stamp
;
6603 if (unlikely(delta
< 0))
6606 total
= sched_avg_period() + delta
;
6608 used
= div_u64(avg
, total
);
6610 if (likely(used
< SCHED_CAPACITY_SCALE
))
6611 return SCHED_CAPACITY_SCALE
- used
;
6616 static void update_cpu_capacity(struct sched_domain
*sd
, int cpu
)
6618 unsigned long capacity
= arch_scale_cpu_capacity(sd
, cpu
);
6619 struct sched_group
*sdg
= sd
->groups
;
6621 cpu_rq(cpu
)->cpu_capacity_orig
= capacity
;
6623 capacity
*= scale_rt_capacity(cpu
);
6624 capacity
>>= SCHED_CAPACITY_SHIFT
;
6629 cpu_rq(cpu
)->cpu_capacity
= capacity
;
6630 sdg
->sgc
->capacity
= capacity
;
6633 void update_group_capacity(struct sched_domain
*sd
, int cpu
)
6635 struct sched_domain
*child
= sd
->child
;
6636 struct sched_group
*group
, *sdg
= sd
->groups
;
6637 unsigned long capacity
;
6638 unsigned long interval
;
6640 interval
= msecs_to_jiffies(sd
->balance_interval
);
6641 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
6642 sdg
->sgc
->next_update
= jiffies
+ interval
;
6645 update_cpu_capacity(sd
, cpu
);
6651 if (child
->flags
& SD_OVERLAP
) {
6653 * SD_OVERLAP domains cannot assume that child groups
6654 * span the current group.
6657 for_each_cpu(cpu
, sched_group_cpus(sdg
)) {
6658 struct sched_group_capacity
*sgc
;
6659 struct rq
*rq
= cpu_rq(cpu
);
6662 * build_sched_domains() -> init_sched_groups_capacity()
6663 * gets here before we've attached the domains to the
6666 * Use capacity_of(), which is set irrespective of domains
6667 * in update_cpu_capacity().
6669 * This avoids capacity from being 0 and
6670 * causing divide-by-zero issues on boot.
6672 if (unlikely(!rq
->sd
)) {
6673 capacity
+= capacity_of(cpu
);
6677 sgc
= rq
->sd
->groups
->sgc
;
6678 capacity
+= sgc
->capacity
;
6682 * !SD_OVERLAP domains can assume that child groups
6683 * span the current group.
6686 group
= child
->groups
;
6688 capacity
+= group
->sgc
->capacity
;
6689 group
= group
->next
;
6690 } while (group
!= child
->groups
);
6693 sdg
->sgc
->capacity
= capacity
;
6697 * Check whether the capacity of the rq has been noticeably reduced by side
6698 * activity. The imbalance_pct is used for the threshold.
6699 * Return true is the capacity is reduced
6702 check_cpu_capacity(struct rq
*rq
, struct sched_domain
*sd
)
6704 return ((rq
->cpu_capacity
* sd
->imbalance_pct
) <
6705 (rq
->cpu_capacity_orig
* 100));
6709 * Group imbalance indicates (and tries to solve) the problem where balancing
6710 * groups is inadequate due to tsk_cpus_allowed() constraints.
6712 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
6713 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
6716 * { 0 1 2 3 } { 4 5 6 7 }
6719 * If we were to balance group-wise we'd place two tasks in the first group and
6720 * two tasks in the second group. Clearly this is undesired as it will overload
6721 * cpu 3 and leave one of the cpus in the second group unused.
6723 * The current solution to this issue is detecting the skew in the first group
6724 * by noticing the lower domain failed to reach balance and had difficulty
6725 * moving tasks due to affinity constraints.
6727 * When this is so detected; this group becomes a candidate for busiest; see
6728 * update_sd_pick_busiest(). And calculate_imbalance() and
6729 * find_busiest_group() avoid some of the usual balance conditions to allow it
6730 * to create an effective group imbalance.
6732 * This is a somewhat tricky proposition since the next run might not find the
6733 * group imbalance and decide the groups need to be balanced again. A most
6734 * subtle and fragile situation.
6737 static inline int sg_imbalanced(struct sched_group
*group
)
6739 return group
->sgc
->imbalance
;
6743 * group_has_capacity returns true if the group has spare capacity that could
6744 * be used by some tasks.
6745 * We consider that a group has spare capacity if the * number of task is
6746 * smaller than the number of CPUs or if the utilization is lower than the
6747 * available capacity for CFS tasks.
6748 * For the latter, we use a threshold to stabilize the state, to take into
6749 * account the variance of the tasks' load and to return true if the available
6750 * capacity in meaningful for the load balancer.
6751 * As an example, an available capacity of 1% can appear but it doesn't make
6752 * any benefit for the load balance.
6755 group_has_capacity(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6757 if (sgs
->sum_nr_running
< sgs
->group_weight
)
6760 if ((sgs
->group_capacity
* 100) >
6761 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6768 * group_is_overloaded returns true if the group has more tasks than it can
6770 * group_is_overloaded is not equals to !group_has_capacity because a group
6771 * with the exact right number of tasks, has no more spare capacity but is not
6772 * overloaded so both group_has_capacity and group_is_overloaded return
6776 group_is_overloaded(struct lb_env
*env
, struct sg_lb_stats
*sgs
)
6778 if (sgs
->sum_nr_running
<= sgs
->group_weight
)
6781 if ((sgs
->group_capacity
* 100) <
6782 (sgs
->group_util
* env
->sd
->imbalance_pct
))
6789 group_type
group_classify(struct sched_group
*group
,
6790 struct sg_lb_stats
*sgs
)
6792 if (sgs
->group_no_capacity
)
6793 return group_overloaded
;
6795 if (sg_imbalanced(group
))
6796 return group_imbalanced
;
6802 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6803 * @env: The load balancing environment.
6804 * @group: sched_group whose statistics are to be updated.
6805 * @load_idx: Load index of sched_domain of this_cpu for load calc.
6806 * @local_group: Does group contain this_cpu.
6807 * @sgs: variable to hold the statistics for this group.
6808 * @overload: Indicate more than one runnable task for any CPU.
6810 static inline void update_sg_lb_stats(struct lb_env
*env
,
6811 struct sched_group
*group
, int load_idx
,
6812 int local_group
, struct sg_lb_stats
*sgs
,
6818 memset(sgs
, 0, sizeof(*sgs
));
6820 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
6821 struct rq
*rq
= cpu_rq(i
);
6823 /* Bias balancing toward cpus of our domain */
6825 load
= target_load(i
, load_idx
);
6827 load
= source_load(i
, load_idx
);
6829 sgs
->group_load
+= load
;
6830 sgs
->group_util
+= cpu_util(i
);
6831 sgs
->sum_nr_running
+= rq
->cfs
.h_nr_running
;
6833 nr_running
= rq
->nr_running
;
6837 #ifdef CONFIG_NUMA_BALANCING
6838 sgs
->nr_numa_running
+= rq
->nr_numa_running
;
6839 sgs
->nr_preferred_running
+= rq
->nr_preferred_running
;
6841 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
6843 * No need to call idle_cpu() if nr_running is not 0
6845 if (!nr_running
&& idle_cpu(i
))
6849 /* Adjust by relative CPU capacity of the group */
6850 sgs
->group_capacity
= group
->sgc
->capacity
;
6851 sgs
->avg_load
= (sgs
->group_load
*SCHED_CAPACITY_SCALE
) / sgs
->group_capacity
;
6853 if (sgs
->sum_nr_running
)
6854 sgs
->load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
6856 sgs
->group_weight
= group
->group_weight
;
6858 sgs
->group_no_capacity
= group_is_overloaded(env
, sgs
);
6859 sgs
->group_type
= group_classify(group
, sgs
);
6863 * update_sd_pick_busiest - return 1 on busiest group
6864 * @env: The load balancing environment.
6865 * @sds: sched_domain statistics
6866 * @sg: sched_group candidate to be checked for being the busiest
6867 * @sgs: sched_group statistics
6869 * Determine if @sg is a busier group than the previously selected
6872 * Return: %true if @sg is a busier group than the previously selected
6873 * busiest group. %false otherwise.
6875 static bool update_sd_pick_busiest(struct lb_env
*env
,
6876 struct sd_lb_stats
*sds
,
6877 struct sched_group
*sg
,
6878 struct sg_lb_stats
*sgs
)
6880 struct sg_lb_stats
*busiest
= &sds
->busiest_stat
;
6882 if (sgs
->group_type
> busiest
->group_type
)
6885 if (sgs
->group_type
< busiest
->group_type
)
6888 if (sgs
->avg_load
<= busiest
->avg_load
)
6891 /* This is the busiest node in its class. */
6892 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
6895 /* No ASYM_PACKING if target cpu is already busy */
6896 if (env
->idle
== CPU_NOT_IDLE
)
6899 * ASYM_PACKING needs to move all the work to the lowest
6900 * numbered CPUs in the group, therefore mark all groups
6901 * higher than ourself as busy.
6903 if (sgs
->sum_nr_running
&& env
->dst_cpu
< group_first_cpu(sg
)) {
6907 /* Prefer to move from highest possible cpu's work */
6908 if (group_first_cpu(sds
->busiest
) < group_first_cpu(sg
))
6915 #ifdef CONFIG_NUMA_BALANCING
6916 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6918 if (sgs
->sum_nr_running
> sgs
->nr_numa_running
)
6920 if (sgs
->sum_nr_running
> sgs
->nr_preferred_running
)
6925 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6927 if (rq
->nr_running
> rq
->nr_numa_running
)
6929 if (rq
->nr_running
> rq
->nr_preferred_running
)
6934 static inline enum fbq_type
fbq_classify_group(struct sg_lb_stats
*sgs
)
6939 static inline enum fbq_type
fbq_classify_rq(struct rq
*rq
)
6943 #endif /* CONFIG_NUMA_BALANCING */
6946 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6947 * @env: The load balancing environment.
6948 * @sds: variable to hold the statistics for this sched_domain.
6950 static inline void update_sd_lb_stats(struct lb_env
*env
, struct sd_lb_stats
*sds
)
6952 struct sched_domain
*child
= env
->sd
->child
;
6953 struct sched_group
*sg
= env
->sd
->groups
;
6954 struct sg_lb_stats tmp_sgs
;
6955 int load_idx
, prefer_sibling
= 0;
6956 bool overload
= false;
6958 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
6961 load_idx
= get_sd_load_idx(env
->sd
, env
->idle
);
6964 struct sg_lb_stats
*sgs
= &tmp_sgs
;
6967 local_group
= cpumask_test_cpu(env
->dst_cpu
, sched_group_cpus(sg
));
6970 sgs
= &sds
->local_stat
;
6972 if (env
->idle
!= CPU_NEWLY_IDLE
||
6973 time_after_eq(jiffies
, sg
->sgc
->next_update
))
6974 update_group_capacity(env
->sd
, env
->dst_cpu
);
6977 update_sg_lb_stats(env
, sg
, load_idx
, local_group
, sgs
,
6984 * In case the child domain prefers tasks go to siblings
6985 * first, lower the sg capacity so that we'll try
6986 * and move all the excess tasks away. We lower the capacity
6987 * of a group only if the local group has the capacity to fit
6988 * these excess tasks. The extra check prevents the case where
6989 * you always pull from the heaviest group when it is already
6990 * under-utilized (possible with a large weight task outweighs
6991 * the tasks on the system).
6993 if (prefer_sibling
&& sds
->local
&&
6994 group_has_capacity(env
, &sds
->local_stat
) &&
6995 (sgs
->sum_nr_running
> 1)) {
6996 sgs
->group_no_capacity
= 1;
6997 sgs
->group_type
= group_classify(sg
, sgs
);
7000 if (update_sd_pick_busiest(env
, sds
, sg
, sgs
)) {
7002 sds
->busiest_stat
= *sgs
;
7006 /* Now, start updating sd_lb_stats */
7007 sds
->total_load
+= sgs
->group_load
;
7008 sds
->total_capacity
+= sgs
->group_capacity
;
7011 } while (sg
!= env
->sd
->groups
);
7013 if (env
->sd
->flags
& SD_NUMA
)
7014 env
->fbq_type
= fbq_classify_group(&sds
->busiest_stat
);
7016 if (!env
->sd
->parent
) {
7017 /* update overload indicator if we are at root domain */
7018 if (env
->dst_rq
->rd
->overload
!= overload
)
7019 env
->dst_rq
->rd
->overload
= overload
;
7025 * check_asym_packing - Check to see if the group is packed into the
7028 * This is primarily intended to used at the sibling level. Some
7029 * cores like POWER7 prefer to use lower numbered SMT threads. In the
7030 * case of POWER7, it can move to lower SMT modes only when higher
7031 * threads are idle. When in lower SMT modes, the threads will
7032 * perform better since they share less core resources. Hence when we
7033 * have idle threads, we want them to be the higher ones.
7035 * This packing function is run on idle threads. It checks to see if
7036 * the busiest CPU in this domain (core in the P7 case) has a higher
7037 * CPU number than the packing function is being run on. Here we are
7038 * assuming lower CPU number will be equivalent to lower a SMT thread
7041 * Return: 1 when packing is required and a task should be moved to
7042 * this CPU. The amount of the imbalance is returned in *imbalance.
7044 * @env: The load balancing environment.
7045 * @sds: Statistics of the sched_domain which is to be packed
7047 static int check_asym_packing(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7051 if (!(env
->sd
->flags
& SD_ASYM_PACKING
))
7054 if (env
->idle
== CPU_NOT_IDLE
)
7060 busiest_cpu
= group_first_cpu(sds
->busiest
);
7061 if (env
->dst_cpu
> busiest_cpu
)
7064 env
->imbalance
= DIV_ROUND_CLOSEST(
7065 sds
->busiest_stat
.avg_load
* sds
->busiest_stat
.group_capacity
,
7066 SCHED_CAPACITY_SCALE
);
7072 * fix_small_imbalance - Calculate the minor imbalance that exists
7073 * amongst the groups of a sched_domain, during
7075 * @env: The load balancing environment.
7076 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
7079 void fix_small_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7081 unsigned long tmp
, capa_now
= 0, capa_move
= 0;
7082 unsigned int imbn
= 2;
7083 unsigned long scaled_busy_load_per_task
;
7084 struct sg_lb_stats
*local
, *busiest
;
7086 local
= &sds
->local_stat
;
7087 busiest
= &sds
->busiest_stat
;
7089 if (!local
->sum_nr_running
)
7090 local
->load_per_task
= cpu_avg_load_per_task(env
->dst_cpu
);
7091 else if (busiest
->load_per_task
> local
->load_per_task
)
7094 scaled_busy_load_per_task
=
7095 (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7096 busiest
->group_capacity
;
7098 if (busiest
->avg_load
+ scaled_busy_load_per_task
>=
7099 local
->avg_load
+ (scaled_busy_load_per_task
* imbn
)) {
7100 env
->imbalance
= busiest
->load_per_task
;
7105 * OK, we don't have enough imbalance to justify moving tasks,
7106 * however we may be able to increase total CPU capacity used by
7110 capa_now
+= busiest
->group_capacity
*
7111 min(busiest
->load_per_task
, busiest
->avg_load
);
7112 capa_now
+= local
->group_capacity
*
7113 min(local
->load_per_task
, local
->avg_load
);
7114 capa_now
/= SCHED_CAPACITY_SCALE
;
7116 /* Amount of load we'd subtract */
7117 if (busiest
->avg_load
> scaled_busy_load_per_task
) {
7118 capa_move
+= busiest
->group_capacity
*
7119 min(busiest
->load_per_task
,
7120 busiest
->avg_load
- scaled_busy_load_per_task
);
7123 /* Amount of load we'd add */
7124 if (busiest
->avg_load
* busiest
->group_capacity
<
7125 busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) {
7126 tmp
= (busiest
->avg_load
* busiest
->group_capacity
) /
7127 local
->group_capacity
;
7129 tmp
= (busiest
->load_per_task
* SCHED_CAPACITY_SCALE
) /
7130 local
->group_capacity
;
7132 capa_move
+= local
->group_capacity
*
7133 min(local
->load_per_task
, local
->avg_load
+ tmp
);
7134 capa_move
/= SCHED_CAPACITY_SCALE
;
7136 /* Move if we gain throughput */
7137 if (capa_move
> capa_now
)
7138 env
->imbalance
= busiest
->load_per_task
;
7142 * calculate_imbalance - Calculate the amount of imbalance present within the
7143 * groups of a given sched_domain during load balance.
7144 * @env: load balance environment
7145 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
7147 static inline void calculate_imbalance(struct lb_env
*env
, struct sd_lb_stats
*sds
)
7149 unsigned long max_pull
, load_above_capacity
= ~0UL;
7150 struct sg_lb_stats
*local
, *busiest
;
7152 local
= &sds
->local_stat
;
7153 busiest
= &sds
->busiest_stat
;
7155 if (busiest
->group_type
== group_imbalanced
) {
7157 * In the group_imb case we cannot rely on group-wide averages
7158 * to ensure cpu-load equilibrium, look at wider averages. XXX
7160 busiest
->load_per_task
=
7161 min(busiest
->load_per_task
, sds
->avg_load
);
7165 * Avg load of busiest sg can be less and avg load of local sg can
7166 * be greater than avg load across all sgs of sd because avg load
7167 * factors in sg capacity and sgs with smaller group_type are
7168 * skipped when updating the busiest sg:
7170 if (busiest
->avg_load
<= sds
->avg_load
||
7171 local
->avg_load
>= sds
->avg_load
) {
7173 return fix_small_imbalance(env
, sds
);
7177 * If there aren't any idle cpus, avoid creating some.
7179 if (busiest
->group_type
== group_overloaded
&&
7180 local
->group_type
== group_overloaded
) {
7181 load_above_capacity
= busiest
->sum_nr_running
* SCHED_CAPACITY_SCALE
;
7182 if (load_above_capacity
> busiest
->group_capacity
) {
7183 load_above_capacity
-= busiest
->group_capacity
;
7184 load_above_capacity
*= scale_load_down(NICE_0_LOAD
);
7185 load_above_capacity
/= busiest
->group_capacity
;
7187 load_above_capacity
= ~0UL;
7191 * We're trying to get all the cpus to the average_load, so we don't
7192 * want to push ourselves above the average load, nor do we wish to
7193 * reduce the max loaded cpu below the average load. At the same time,
7194 * we also don't want to reduce the group load below the group
7195 * capacity. Thus we look for the minimum possible imbalance.
7197 max_pull
= min(busiest
->avg_load
- sds
->avg_load
, load_above_capacity
);
7199 /* How much load to actually move to equalise the imbalance */
7200 env
->imbalance
= min(
7201 max_pull
* busiest
->group_capacity
,
7202 (sds
->avg_load
- local
->avg_load
) * local
->group_capacity
7203 ) / SCHED_CAPACITY_SCALE
;
7206 * if *imbalance is less than the average load per runnable task
7207 * there is no guarantee that any tasks will be moved so we'll have
7208 * a think about bumping its value to force at least one task to be
7211 if (env
->imbalance
< busiest
->load_per_task
)
7212 return fix_small_imbalance(env
, sds
);
7215 /******* find_busiest_group() helpers end here *********************/
7218 * find_busiest_group - Returns the busiest group within the sched_domain
7219 * if there is an imbalance.
7221 * Also calculates the amount of weighted load which should be moved
7222 * to restore balance.
7224 * @env: The load balancing environment.
7226 * Return: - The busiest group if imbalance exists.
7228 static struct sched_group
*find_busiest_group(struct lb_env
*env
)
7230 struct sg_lb_stats
*local
, *busiest
;
7231 struct sd_lb_stats sds
;
7233 init_sd_lb_stats(&sds
);
7236 * Compute the various statistics relavent for load balancing at
7239 update_sd_lb_stats(env
, &sds
);
7240 local
= &sds
.local_stat
;
7241 busiest
= &sds
.busiest_stat
;
7243 /* ASYM feature bypasses nice load balance check */
7244 if (check_asym_packing(env
, &sds
))
7247 /* There is no busy sibling group to pull tasks from */
7248 if (!sds
.busiest
|| busiest
->sum_nr_running
== 0)
7251 sds
.avg_load
= (SCHED_CAPACITY_SCALE
* sds
.total_load
)
7252 / sds
.total_capacity
;
7255 * If the busiest group is imbalanced the below checks don't
7256 * work because they assume all things are equal, which typically
7257 * isn't true due to cpus_allowed constraints and the like.
7259 if (busiest
->group_type
== group_imbalanced
)
7262 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7263 if (env
->idle
== CPU_NEWLY_IDLE
&& group_has_capacity(env
, local
) &&
7264 busiest
->group_no_capacity
)
7268 * If the local group is busier than the selected busiest group
7269 * don't try and pull any tasks.
7271 if (local
->avg_load
>= busiest
->avg_load
)
7275 * Don't pull any tasks if this group is already above the domain
7278 if (local
->avg_load
>= sds
.avg_load
)
7281 if (env
->idle
== CPU_IDLE
) {
7283 * This cpu is idle. If the busiest group is not overloaded
7284 * and there is no imbalance between this and busiest group
7285 * wrt idle cpus, it is balanced. The imbalance becomes
7286 * significant if the diff is greater than 1 otherwise we
7287 * might end up to just move the imbalance on another group
7289 if ((busiest
->group_type
!= group_overloaded
) &&
7290 (local
->idle_cpus
<= (busiest
->idle_cpus
+ 1)))
7294 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
7295 * imbalance_pct to be conservative.
7297 if (100 * busiest
->avg_load
<=
7298 env
->sd
->imbalance_pct
* local
->avg_load
)
7303 /* Looks like there is an imbalance. Compute it */
7304 calculate_imbalance(env
, &sds
);
7313 * find_busiest_queue - find the busiest runqueue among the cpus in group.
7315 static struct rq
*find_busiest_queue(struct lb_env
*env
,
7316 struct sched_group
*group
)
7318 struct rq
*busiest
= NULL
, *rq
;
7319 unsigned long busiest_load
= 0, busiest_capacity
= 1;
7322 for_each_cpu_and(i
, sched_group_cpus(group
), env
->cpus
) {
7323 unsigned long capacity
, wl
;
7327 rt
= fbq_classify_rq(rq
);
7330 * We classify groups/runqueues into three groups:
7331 * - regular: there are !numa tasks
7332 * - remote: there are numa tasks that run on the 'wrong' node
7333 * - all: there is no distinction
7335 * In order to avoid migrating ideally placed numa tasks,
7336 * ignore those when there's better options.
7338 * If we ignore the actual busiest queue to migrate another
7339 * task, the next balance pass can still reduce the busiest
7340 * queue by moving tasks around inside the node.
7342 * If we cannot move enough load due to this classification
7343 * the next pass will adjust the group classification and
7344 * allow migration of more tasks.
7346 * Both cases only affect the total convergence complexity.
7348 if (rt
> env
->fbq_type
)
7351 capacity
= capacity_of(i
);
7353 wl
= weighted_cpuload(i
);
7356 * When comparing with imbalance, use weighted_cpuload()
7357 * which is not scaled with the cpu capacity.
7360 if (rq
->nr_running
== 1 && wl
> env
->imbalance
&&
7361 !check_cpu_capacity(rq
, env
->sd
))
7365 * For the load comparisons with the other cpu's, consider
7366 * the weighted_cpuload() scaled with the cpu capacity, so
7367 * that the load can be moved away from the cpu that is
7368 * potentially running at a lower capacity.
7370 * Thus we're looking for max(wl_i / capacity_i), crosswise
7371 * multiplication to rid ourselves of the division works out
7372 * to: wl_i * capacity_j > wl_j * capacity_i; where j is
7373 * our previous maximum.
7375 if (wl
* busiest_capacity
> busiest_load
* capacity
) {
7377 busiest_capacity
= capacity
;
7386 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
7387 * so long as it is large enough.
7389 #define MAX_PINNED_INTERVAL 512
7391 /* Working cpumask for load_balance and load_balance_newidle. */
7392 DEFINE_PER_CPU(cpumask_var_t
, load_balance_mask
);
7394 static int need_active_balance(struct lb_env
*env
)
7396 struct sched_domain
*sd
= env
->sd
;
7398 if (env
->idle
== CPU_NEWLY_IDLE
) {
7401 * ASYM_PACKING needs to force migrate tasks from busy but
7402 * higher numbered CPUs in order to pack all tasks in the
7403 * lowest numbered CPUs.
7405 if ((sd
->flags
& SD_ASYM_PACKING
) && env
->src_cpu
> env
->dst_cpu
)
7410 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
7411 * It's worth migrating the task if the src_cpu's capacity is reduced
7412 * because of other sched_class or IRQs if more capacity stays
7413 * available on dst_cpu.
7415 if ((env
->idle
!= CPU_NOT_IDLE
) &&
7416 (env
->src_rq
->cfs
.h_nr_running
== 1)) {
7417 if ((check_cpu_capacity(env
->src_rq
, sd
)) &&
7418 (capacity_of(env
->src_cpu
)*sd
->imbalance_pct
< capacity_of(env
->dst_cpu
)*100))
7422 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
7425 static int active_load_balance_cpu_stop(void *data
);
7427 static int should_we_balance(struct lb_env
*env
)
7429 struct sched_group
*sg
= env
->sd
->groups
;
7430 struct cpumask
*sg_cpus
, *sg_mask
;
7431 int cpu
, balance_cpu
= -1;
7434 * In the newly idle case, we will allow all the cpu's
7435 * to do the newly idle load balance.
7437 if (env
->idle
== CPU_NEWLY_IDLE
)
7440 sg_cpus
= sched_group_cpus(sg
);
7441 sg_mask
= sched_group_mask(sg
);
7442 /* Try to find first idle cpu */
7443 for_each_cpu_and(cpu
, sg_cpus
, env
->cpus
) {
7444 if (!cpumask_test_cpu(cpu
, sg_mask
) || !idle_cpu(cpu
))
7451 if (balance_cpu
== -1)
7452 balance_cpu
= group_balance_cpu(sg
);
7455 * First idle cpu or the first cpu(busiest) in this sched group
7456 * is eligible for doing load balancing at this and above domains.
7458 return balance_cpu
== env
->dst_cpu
;
7462 * Check this_cpu to ensure it is balanced within domain. Attempt to move
7463 * tasks if there is an imbalance.
7465 static int load_balance(int this_cpu
, struct rq
*this_rq
,
7466 struct sched_domain
*sd
, enum cpu_idle_type idle
,
7467 int *continue_balancing
)
7469 int ld_moved
, cur_ld_moved
, active_balance
= 0;
7470 struct sched_domain
*sd_parent
= sd
->parent
;
7471 struct sched_group
*group
;
7473 unsigned long flags
;
7474 struct cpumask
*cpus
= this_cpu_cpumask_var_ptr(load_balance_mask
);
7476 struct lb_env env
= {
7478 .dst_cpu
= this_cpu
,
7480 .dst_grpmask
= sched_group_cpus(sd
->groups
),
7482 .loop_break
= sched_nr_migrate_break
,
7485 .tasks
= LIST_HEAD_INIT(env
.tasks
),
7489 * For NEWLY_IDLE load_balancing, we don't need to consider
7490 * other cpus in our group
7492 if (idle
== CPU_NEWLY_IDLE
)
7493 env
.dst_grpmask
= NULL
;
7495 cpumask_copy(cpus
, cpu_active_mask
);
7497 schedstat_inc(sd
->lb_count
[idle
]);
7500 if (!should_we_balance(&env
)) {
7501 *continue_balancing
= 0;
7505 group
= find_busiest_group(&env
);
7507 schedstat_inc(sd
->lb_nobusyg
[idle
]);
7511 busiest
= find_busiest_queue(&env
, group
);
7513 schedstat_inc(sd
->lb_nobusyq
[idle
]);
7517 BUG_ON(busiest
== env
.dst_rq
);
7519 schedstat_add(sd
->lb_imbalance
[idle
], env
.imbalance
);
7521 env
.src_cpu
= busiest
->cpu
;
7522 env
.src_rq
= busiest
;
7525 if (busiest
->nr_running
> 1) {
7527 * Attempt to move tasks. If find_busiest_group has found
7528 * an imbalance but busiest->nr_running <= 1, the group is
7529 * still unbalanced. ld_moved simply stays zero, so it is
7530 * correctly treated as an imbalance.
7532 env
.flags
|= LBF_ALL_PINNED
;
7533 env
.loop_max
= min(sysctl_sched_nr_migrate
, busiest
->nr_running
);
7536 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7539 * cur_ld_moved - load moved in current iteration
7540 * ld_moved - cumulative load moved across iterations
7542 cur_ld_moved
= detach_tasks(&env
);
7545 * We've detached some tasks from busiest_rq. Every
7546 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
7547 * unlock busiest->lock, and we are able to be sure
7548 * that nobody can manipulate the tasks in parallel.
7549 * See task_rq_lock() family for the details.
7552 raw_spin_unlock(&busiest
->lock
);
7556 ld_moved
+= cur_ld_moved
;
7559 local_irq_restore(flags
);
7561 if (env
.flags
& LBF_NEED_BREAK
) {
7562 env
.flags
&= ~LBF_NEED_BREAK
;
7567 * Revisit (affine) tasks on src_cpu that couldn't be moved to
7568 * us and move them to an alternate dst_cpu in our sched_group
7569 * where they can run. The upper limit on how many times we
7570 * iterate on same src_cpu is dependent on number of cpus in our
7573 * This changes load balance semantics a bit on who can move
7574 * load to a given_cpu. In addition to the given_cpu itself
7575 * (or a ilb_cpu acting on its behalf where given_cpu is
7576 * nohz-idle), we now have balance_cpu in a position to move
7577 * load to given_cpu. In rare situations, this may cause
7578 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
7579 * _independently_ and at _same_ time to move some load to
7580 * given_cpu) causing exceess load to be moved to given_cpu.
7581 * This however should not happen so much in practice and
7582 * moreover subsequent load balance cycles should correct the
7583 * excess load moved.
7585 if ((env
.flags
& LBF_DST_PINNED
) && env
.imbalance
> 0) {
7587 /* Prevent to re-select dst_cpu via env's cpus */
7588 cpumask_clear_cpu(env
.dst_cpu
, env
.cpus
);
7590 env
.dst_rq
= cpu_rq(env
.new_dst_cpu
);
7591 env
.dst_cpu
= env
.new_dst_cpu
;
7592 env
.flags
&= ~LBF_DST_PINNED
;
7594 env
.loop_break
= sched_nr_migrate_break
;
7597 * Go back to "more_balance" rather than "redo" since we
7598 * need to continue with same src_cpu.
7604 * We failed to reach balance because of affinity.
7607 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7609 if ((env
.flags
& LBF_SOME_PINNED
) && env
.imbalance
> 0)
7610 *group_imbalance
= 1;
7613 /* All tasks on this runqueue were pinned by CPU affinity */
7614 if (unlikely(env
.flags
& LBF_ALL_PINNED
)) {
7615 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
7616 if (!cpumask_empty(cpus
)) {
7618 env
.loop_break
= sched_nr_migrate_break
;
7621 goto out_all_pinned
;
7626 schedstat_inc(sd
->lb_failed
[idle
]);
7628 * Increment the failure counter only on periodic balance.
7629 * We do not want newidle balance, which can be very
7630 * frequent, pollute the failure counter causing
7631 * excessive cache_hot migrations and active balances.
7633 if (idle
!= CPU_NEWLY_IDLE
)
7634 sd
->nr_balance_failed
++;
7636 if (need_active_balance(&env
)) {
7637 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
7639 /* don't kick the active_load_balance_cpu_stop,
7640 * if the curr task on busiest cpu can't be
7643 if (!cpumask_test_cpu(this_cpu
,
7644 tsk_cpus_allowed(busiest
->curr
))) {
7645 raw_spin_unlock_irqrestore(&busiest
->lock
,
7647 env
.flags
|= LBF_ALL_PINNED
;
7648 goto out_one_pinned
;
7652 * ->active_balance synchronizes accesses to
7653 * ->active_balance_work. Once set, it's cleared
7654 * only after active load balance is finished.
7656 if (!busiest
->active_balance
) {
7657 busiest
->active_balance
= 1;
7658 busiest
->push_cpu
= this_cpu
;
7661 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
7663 if (active_balance
) {
7664 stop_one_cpu_nowait(cpu_of(busiest
),
7665 active_load_balance_cpu_stop
, busiest
,
7666 &busiest
->active_balance_work
);
7669 /* We've kicked active balancing, force task migration. */
7670 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
7673 sd
->nr_balance_failed
= 0;
7675 if (likely(!active_balance
)) {
7676 /* We were unbalanced, so reset the balancing interval */
7677 sd
->balance_interval
= sd
->min_interval
;
7680 * If we've begun active balancing, start to back off. This
7681 * case may not be covered by the all_pinned logic if there
7682 * is only 1 task on the busy runqueue (because we don't call
7685 if (sd
->balance_interval
< sd
->max_interval
)
7686 sd
->balance_interval
*= 2;
7693 * We reach balance although we may have faced some affinity
7694 * constraints. Clear the imbalance flag if it was set.
7697 int *group_imbalance
= &sd_parent
->groups
->sgc
->imbalance
;
7699 if (*group_imbalance
)
7700 *group_imbalance
= 0;
7705 * We reach balance because all tasks are pinned at this level so
7706 * we can't migrate them. Let the imbalance flag set so parent level
7707 * can try to migrate them.
7709 schedstat_inc(sd
->lb_balanced
[idle
]);
7711 sd
->nr_balance_failed
= 0;
7714 /* tune up the balancing interval */
7715 if (((env
.flags
& LBF_ALL_PINNED
) &&
7716 sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
7717 (sd
->balance_interval
< sd
->max_interval
))
7718 sd
->balance_interval
*= 2;
7725 static inline unsigned long
7726 get_sd_balance_interval(struct sched_domain
*sd
, int cpu_busy
)
7728 unsigned long interval
= sd
->balance_interval
;
7731 interval
*= sd
->busy_factor
;
7733 /* scale ms to jiffies */
7734 interval
= msecs_to_jiffies(interval
);
7735 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
7741 update_next_balance(struct sched_domain
*sd
, unsigned long *next_balance
)
7743 unsigned long interval
, next
;
7745 /* used by idle balance, so cpu_busy = 0 */
7746 interval
= get_sd_balance_interval(sd
, 0);
7747 next
= sd
->last_balance
+ interval
;
7749 if (time_after(*next_balance
, next
))
7750 *next_balance
= next
;
7754 * idle_balance is called by schedule() if this_cpu is about to become
7755 * idle. Attempts to pull tasks from other CPUs.
7757 static int idle_balance(struct rq
*this_rq
)
7759 unsigned long next_balance
= jiffies
+ HZ
;
7760 int this_cpu
= this_rq
->cpu
;
7761 struct sched_domain
*sd
;
7762 int pulled_task
= 0;
7766 * We must set idle_stamp _before_ calling idle_balance(), such that we
7767 * measure the duration of idle_balance() as idle time.
7769 this_rq
->idle_stamp
= rq_clock(this_rq
);
7771 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
||
7772 !this_rq
->rd
->overload
) {
7774 sd
= rcu_dereference_check_sched_domain(this_rq
->sd
);
7776 update_next_balance(sd
, &next_balance
);
7782 raw_spin_unlock(&this_rq
->lock
);
7784 update_blocked_averages(this_cpu
);
7786 for_each_domain(this_cpu
, sd
) {
7787 int continue_balancing
= 1;
7788 u64 t0
, domain_cost
;
7790 if (!(sd
->flags
& SD_LOAD_BALANCE
))
7793 if (this_rq
->avg_idle
< curr_cost
+ sd
->max_newidle_lb_cost
) {
7794 update_next_balance(sd
, &next_balance
);
7798 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
7799 t0
= sched_clock_cpu(this_cpu
);
7801 pulled_task
= load_balance(this_cpu
, this_rq
,
7803 &continue_balancing
);
7805 domain_cost
= sched_clock_cpu(this_cpu
) - t0
;
7806 if (domain_cost
> sd
->max_newidle_lb_cost
)
7807 sd
->max_newidle_lb_cost
= domain_cost
;
7809 curr_cost
+= domain_cost
;
7812 update_next_balance(sd
, &next_balance
);
7815 * Stop searching for tasks to pull if there are
7816 * now runnable tasks on this rq.
7818 if (pulled_task
|| this_rq
->nr_running
> 0)
7823 raw_spin_lock(&this_rq
->lock
);
7825 if (curr_cost
> this_rq
->max_idle_balance_cost
)
7826 this_rq
->max_idle_balance_cost
= curr_cost
;
7829 * While browsing the domains, we released the rq lock, a task could
7830 * have been enqueued in the meantime. Since we're not going idle,
7831 * pretend we pulled a task.
7833 if (this_rq
->cfs
.h_nr_running
&& !pulled_task
)
7837 /* Move the next balance forward */
7838 if (time_after(this_rq
->next_balance
, next_balance
))
7839 this_rq
->next_balance
= next_balance
;
7841 /* Is there a task of a high priority class? */
7842 if (this_rq
->nr_running
!= this_rq
->cfs
.h_nr_running
)
7846 this_rq
->idle_stamp
= 0;
7852 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
7853 * running tasks off the busiest CPU onto idle CPUs. It requires at
7854 * least 1 task to be running on each physical CPU where possible, and
7855 * avoids physical / logical imbalances.
7857 static int active_load_balance_cpu_stop(void *data
)
7859 struct rq
*busiest_rq
= data
;
7860 int busiest_cpu
= cpu_of(busiest_rq
);
7861 int target_cpu
= busiest_rq
->push_cpu
;
7862 struct rq
*target_rq
= cpu_rq(target_cpu
);
7863 struct sched_domain
*sd
;
7864 struct task_struct
*p
= NULL
;
7866 raw_spin_lock_irq(&busiest_rq
->lock
);
7868 /* make sure the requested cpu hasn't gone down in the meantime */
7869 if (unlikely(busiest_cpu
!= smp_processor_id() ||
7870 !busiest_rq
->active_balance
))
7873 /* Is there any task to move? */
7874 if (busiest_rq
->nr_running
<= 1)
7878 * This condition is "impossible", if it occurs
7879 * we need to fix it. Originally reported by
7880 * Bjorn Helgaas on a 128-cpu setup.
7882 BUG_ON(busiest_rq
== target_rq
);
7884 /* Search for an sd spanning us and the target CPU. */
7886 for_each_domain(target_cpu
, sd
) {
7887 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
7888 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
7893 struct lb_env env
= {
7895 .dst_cpu
= target_cpu
,
7896 .dst_rq
= target_rq
,
7897 .src_cpu
= busiest_rq
->cpu
,
7898 .src_rq
= busiest_rq
,
7902 schedstat_inc(sd
->alb_count
);
7904 p
= detach_one_task(&env
);
7906 schedstat_inc(sd
->alb_pushed
);
7907 /* Active balancing done, reset the failure counter. */
7908 sd
->nr_balance_failed
= 0;
7910 schedstat_inc(sd
->alb_failed
);
7915 busiest_rq
->active_balance
= 0;
7916 raw_spin_unlock(&busiest_rq
->lock
);
7919 attach_one_task(target_rq
, p
);
7926 static inline int on_null_domain(struct rq
*rq
)
7928 return unlikely(!rcu_dereference_sched(rq
->sd
));
7931 #ifdef CONFIG_NO_HZ_COMMON
7933 * idle load balancing details
7934 * - When one of the busy CPUs notice that there may be an idle rebalancing
7935 * needed, they will kick the idle load balancer, which then does idle
7936 * load balancing for all the idle CPUs.
7939 cpumask_var_t idle_cpus_mask
;
7941 unsigned long next_balance
; /* in jiffy units */
7942 } nohz ____cacheline_aligned
;
7944 static inline int find_new_ilb(void)
7946 int ilb
= cpumask_first(nohz
.idle_cpus_mask
);
7948 if (ilb
< nr_cpu_ids
&& idle_cpu(ilb
))
7955 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
7956 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
7957 * CPU (if there is one).
7959 static void nohz_balancer_kick(void)
7963 nohz
.next_balance
++;
7965 ilb_cpu
= find_new_ilb();
7967 if (ilb_cpu
>= nr_cpu_ids
)
7970 if (test_and_set_bit(NOHZ_BALANCE_KICK
, nohz_flags(ilb_cpu
)))
7973 * Use smp_send_reschedule() instead of resched_cpu().
7974 * This way we generate a sched IPI on the target cpu which
7975 * is idle. And the softirq performing nohz idle load balance
7976 * will be run before returning from the IPI.
7978 smp_send_reschedule(ilb_cpu
);
7982 void nohz_balance_exit_idle(unsigned int cpu
)
7984 if (unlikely(test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))) {
7986 * Completely isolated CPUs don't ever set, so we must test.
7988 if (likely(cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))) {
7989 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
7990 atomic_dec(&nohz
.nr_cpus
);
7992 clear_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
7996 static inline void set_cpu_sd_state_busy(void)
7998 struct sched_domain
*sd
;
7999 int cpu
= smp_processor_id();
8002 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8004 if (!sd
|| !sd
->nohz_idle
)
8008 atomic_inc(&sd
->groups
->sgc
->nr_busy_cpus
);
8013 void set_cpu_sd_state_idle(void)
8015 struct sched_domain
*sd
;
8016 int cpu
= smp_processor_id();
8019 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8021 if (!sd
|| sd
->nohz_idle
)
8025 atomic_dec(&sd
->groups
->sgc
->nr_busy_cpus
);
8031 * This routine will record that the cpu is going idle with tick stopped.
8032 * This info will be used in performing idle load balancing in the future.
8034 void nohz_balance_enter_idle(int cpu
)
8037 * If this cpu is going down, then nothing needs to be done.
8039 if (!cpu_active(cpu
))
8042 if (test_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
)))
8046 * If we're a completely isolated CPU, we don't play.
8048 if (on_null_domain(cpu_rq(cpu
)))
8051 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
8052 atomic_inc(&nohz
.nr_cpus
);
8053 set_bit(NOHZ_TICK_STOPPED
, nohz_flags(cpu
));
8057 static DEFINE_SPINLOCK(balancing
);
8060 * Scale the max load_balance interval with the number of CPUs in the system.
8061 * This trades load-balance latency on larger machines for less cross talk.
8063 void update_max_interval(void)
8065 max_load_balance_interval
= HZ
*num_online_cpus()/10;
8069 * It checks each scheduling domain to see if it is due to be balanced,
8070 * and initiates a balancing operation if so.
8072 * Balancing parameters are set up in init_sched_domains.
8074 static void rebalance_domains(struct rq
*rq
, enum cpu_idle_type idle
)
8076 int continue_balancing
= 1;
8078 unsigned long interval
;
8079 struct sched_domain
*sd
;
8080 /* Earliest time when we have to do rebalance again */
8081 unsigned long next_balance
= jiffies
+ 60*HZ
;
8082 int update_next_balance
= 0;
8083 int need_serialize
, need_decay
= 0;
8086 update_blocked_averages(cpu
);
8089 for_each_domain(cpu
, sd
) {
8091 * Decay the newidle max times here because this is a regular
8092 * visit to all the domains. Decay ~1% per second.
8094 if (time_after(jiffies
, sd
->next_decay_max_lb_cost
)) {
8095 sd
->max_newidle_lb_cost
=
8096 (sd
->max_newidle_lb_cost
* 253) / 256;
8097 sd
->next_decay_max_lb_cost
= jiffies
+ HZ
;
8100 max_cost
+= sd
->max_newidle_lb_cost
;
8102 if (!(sd
->flags
& SD_LOAD_BALANCE
))
8106 * Stop the load balance at this level. There is another
8107 * CPU in our sched group which is doing load balancing more
8110 if (!continue_balancing
) {
8116 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8118 need_serialize
= sd
->flags
& SD_SERIALIZE
;
8119 if (need_serialize
) {
8120 if (!spin_trylock(&balancing
))
8124 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
8125 if (load_balance(cpu
, rq
, sd
, idle
, &continue_balancing
)) {
8127 * The LBF_DST_PINNED logic could have changed
8128 * env->dst_cpu, so we can't know our idle
8129 * state even if we migrated tasks. Update it.
8131 idle
= idle_cpu(cpu
) ? CPU_IDLE
: CPU_NOT_IDLE
;
8133 sd
->last_balance
= jiffies
;
8134 interval
= get_sd_balance_interval(sd
, idle
!= CPU_IDLE
);
8137 spin_unlock(&balancing
);
8139 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
8140 next_balance
= sd
->last_balance
+ interval
;
8141 update_next_balance
= 1;
8146 * Ensure the rq-wide value also decays but keep it at a
8147 * reasonable floor to avoid funnies with rq->avg_idle.
8149 rq
->max_idle_balance_cost
=
8150 max((u64
)sysctl_sched_migration_cost
, max_cost
);
8155 * next_balance will be updated only when there is a need.
8156 * When the cpu is attached to null domain for ex, it will not be
8159 if (likely(update_next_balance
)) {
8160 rq
->next_balance
= next_balance
;
8162 #ifdef CONFIG_NO_HZ_COMMON
8164 * If this CPU has been elected to perform the nohz idle
8165 * balance. Other idle CPUs have already rebalanced with
8166 * nohz_idle_balance() and nohz.next_balance has been
8167 * updated accordingly. This CPU is now running the idle load
8168 * balance for itself and we need to update the
8169 * nohz.next_balance accordingly.
8171 if ((idle
== CPU_IDLE
) && time_after(nohz
.next_balance
, rq
->next_balance
))
8172 nohz
.next_balance
= rq
->next_balance
;
8177 #ifdef CONFIG_NO_HZ_COMMON
8179 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8180 * rebalancing for all the cpus for whom scheduler ticks are stopped.
8182 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
)
8184 int this_cpu
= this_rq
->cpu
;
8187 /* Earliest time when we have to do rebalance again */
8188 unsigned long next_balance
= jiffies
+ 60*HZ
;
8189 int update_next_balance
= 0;
8191 if (idle
!= CPU_IDLE
||
8192 !test_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
)))
8195 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
8196 if (balance_cpu
== this_cpu
|| !idle_cpu(balance_cpu
))
8200 * If this cpu gets work to do, stop the load balancing
8201 * work being done for other cpus. Next load
8202 * balancing owner will pick it up.
8207 rq
= cpu_rq(balance_cpu
);
8210 * If time for next balance is due,
8213 if (time_after_eq(jiffies
, rq
->next_balance
)) {
8214 raw_spin_lock_irq(&rq
->lock
);
8215 update_rq_clock(rq
);
8216 cpu_load_update_idle(rq
);
8217 raw_spin_unlock_irq(&rq
->lock
);
8218 rebalance_domains(rq
, CPU_IDLE
);
8221 if (time_after(next_balance
, rq
->next_balance
)) {
8222 next_balance
= rq
->next_balance
;
8223 update_next_balance
= 1;
8228 * next_balance will be updated only when there is a need.
8229 * When the CPU is attached to null domain for ex, it will not be
8232 if (likely(update_next_balance
))
8233 nohz
.next_balance
= next_balance
;
8235 clear_bit(NOHZ_BALANCE_KICK
, nohz_flags(this_cpu
));
8239 * Current heuristic for kicking the idle load balancer in the presence
8240 * of an idle cpu in the system.
8241 * - This rq has more than one task.
8242 * - This rq has at least one CFS task and the capacity of the CPU is
8243 * significantly reduced because of RT tasks or IRQs.
8244 * - At parent of LLC scheduler domain level, this cpu's scheduler group has
8245 * multiple busy cpu.
8246 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
8247 * domain span are idle.
8249 static inline bool nohz_kick_needed(struct rq
*rq
)
8251 unsigned long now
= jiffies
;
8252 struct sched_domain
*sd
;
8253 struct sched_group_capacity
*sgc
;
8254 int nr_busy
, cpu
= rq
->cpu
;
8257 if (unlikely(rq
->idle_balance
))
8261 * We may be recently in ticked or tickless idle mode. At the first
8262 * busy tick after returning from idle, we will update the busy stats.
8264 set_cpu_sd_state_busy();
8265 nohz_balance_exit_idle(cpu
);
8268 * None are in tickless mode and hence no need for NOHZ idle load
8271 if (likely(!atomic_read(&nohz
.nr_cpus
)))
8274 if (time_before(now
, nohz
.next_balance
))
8277 if (rq
->nr_running
>= 2)
8281 sd
= rcu_dereference(per_cpu(sd_busy
, cpu
));
8283 sgc
= sd
->groups
->sgc
;
8284 nr_busy
= atomic_read(&sgc
->nr_busy_cpus
);
8293 sd
= rcu_dereference(rq
->sd
);
8295 if ((rq
->cfs
.h_nr_running
>= 1) &&
8296 check_cpu_capacity(rq
, sd
)) {
8302 sd
= rcu_dereference(per_cpu(sd_asym
, cpu
));
8303 if (sd
&& (cpumask_first_and(nohz
.idle_cpus_mask
,
8304 sched_domain_span(sd
)) < cpu
)) {
8314 static void nohz_idle_balance(struct rq
*this_rq
, enum cpu_idle_type idle
) { }
8318 * run_rebalance_domains is triggered when needed from the scheduler tick.
8319 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
8321 static __latent_entropy
void run_rebalance_domains(struct softirq_action
*h
)
8323 struct rq
*this_rq
= this_rq();
8324 enum cpu_idle_type idle
= this_rq
->idle_balance
?
8325 CPU_IDLE
: CPU_NOT_IDLE
;
8328 * If this cpu has a pending nohz_balance_kick, then do the
8329 * balancing on behalf of the other idle cpus whose ticks are
8330 * stopped. Do nohz_idle_balance *before* rebalance_domains to
8331 * give the idle cpus a chance to load balance. Else we may
8332 * load balance only within the local sched_domain hierarchy
8333 * and abort nohz_idle_balance altogether if we pull some load.
8335 nohz_idle_balance(this_rq
, idle
);
8336 rebalance_domains(this_rq
, idle
);
8340 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
8342 void trigger_load_balance(struct rq
*rq
)
8344 /* Don't need to rebalance while attached to NULL domain */
8345 if (unlikely(on_null_domain(rq
)))
8348 if (time_after_eq(jiffies
, rq
->next_balance
))
8349 raise_softirq(SCHED_SOFTIRQ
);
8350 #ifdef CONFIG_NO_HZ_COMMON
8351 if (nohz_kick_needed(rq
))
8352 nohz_balancer_kick();
8356 static void rq_online_fair(struct rq
*rq
)
8360 update_runtime_enabled(rq
);
8363 static void rq_offline_fair(struct rq
*rq
)
8367 /* Ensure any throttled groups are reachable by pick_next_task */
8368 unthrottle_offline_cfs_rqs(rq
);
8371 #endif /* CONFIG_SMP */
8374 * scheduler tick hitting a task of our scheduling class:
8376 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
8378 struct cfs_rq
*cfs_rq
;
8379 struct sched_entity
*se
= &curr
->se
;
8381 for_each_sched_entity(se
) {
8382 cfs_rq
= cfs_rq_of(se
);
8383 entity_tick(cfs_rq
, se
, queued
);
8386 if (static_branch_unlikely(&sched_numa_balancing
))
8387 task_tick_numa(rq
, curr
);
8391 * called on fork with the child task as argument from the parent's context
8392 * - child not yet on the tasklist
8393 * - preemption disabled
8395 static void task_fork_fair(struct task_struct
*p
)
8397 struct cfs_rq
*cfs_rq
;
8398 struct sched_entity
*se
= &p
->se
, *curr
;
8399 struct rq
*rq
= this_rq();
8401 raw_spin_lock(&rq
->lock
);
8402 update_rq_clock(rq
);
8404 cfs_rq
= task_cfs_rq(current
);
8405 curr
= cfs_rq
->curr
;
8407 update_curr(cfs_rq
);
8408 se
->vruntime
= curr
->vruntime
;
8410 place_entity(cfs_rq
, se
, 1);
8412 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
8414 * Upon rescheduling, sched_class::put_prev_task() will place
8415 * 'current' within the tree based on its new key value.
8417 swap(curr
->vruntime
, se
->vruntime
);
8421 se
->vruntime
-= cfs_rq
->min_vruntime
;
8422 raw_spin_unlock(&rq
->lock
);
8426 * Priority of the task has changed. Check to see if we preempt
8430 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
8432 if (!task_on_rq_queued(p
))
8436 * Reschedule if we are currently running on this runqueue and
8437 * our priority decreased, or if we are not currently running on
8438 * this runqueue and our priority is higher than the current's
8440 if (rq
->curr
== p
) {
8441 if (p
->prio
> oldprio
)
8444 check_preempt_curr(rq
, p
, 0);
8447 static inline bool vruntime_normalized(struct task_struct
*p
)
8449 struct sched_entity
*se
= &p
->se
;
8452 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
8453 * the dequeue_entity(.flags=0) will already have normalized the
8460 * When !on_rq, vruntime of the task has usually NOT been normalized.
8461 * But there are some cases where it has already been normalized:
8463 * - A forked child which is waiting for being woken up by
8464 * wake_up_new_task().
8465 * - A task which has been woken up by try_to_wake_up() and
8466 * waiting for actually being woken up by sched_ttwu_pending().
8468 if (!se
->sum_exec_runtime
|| p
->state
== TASK_WAKING
)
8474 static void detach_task_cfs_rq(struct task_struct
*p
)
8476 struct sched_entity
*se
= &p
->se
;
8477 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8478 u64 now
= cfs_rq_clock_task(cfs_rq
);
8480 if (!vruntime_normalized(p
)) {
8482 * Fix up our vruntime so that the current sleep doesn't
8483 * cause 'unlimited' sleep bonus.
8485 place_entity(cfs_rq
, se
, 0);
8486 se
->vruntime
-= cfs_rq
->min_vruntime
;
8489 /* Catch up with the cfs_rq and remove our load when we leave */
8490 update_cfs_rq_load_avg(now
, cfs_rq
, false);
8491 detach_entity_load_avg(cfs_rq
, se
);
8492 update_tg_load_avg(cfs_rq
, false);
8495 static void attach_task_cfs_rq(struct task_struct
*p
)
8497 struct sched_entity
*se
= &p
->se
;
8498 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8499 u64 now
= cfs_rq_clock_task(cfs_rq
);
8501 #ifdef CONFIG_FAIR_GROUP_SCHED
8503 * Since the real-depth could have been changed (only FAIR
8504 * class maintain depth value), reset depth properly.
8506 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8509 /* Synchronize task with its cfs_rq */
8510 update_cfs_rq_load_avg(now
, cfs_rq
, false);
8511 attach_entity_load_avg(cfs_rq
, se
);
8512 update_tg_load_avg(cfs_rq
, false);
8514 if (!vruntime_normalized(p
))
8515 se
->vruntime
+= cfs_rq
->min_vruntime
;
8518 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
8520 detach_task_cfs_rq(p
);
8523 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
8525 attach_task_cfs_rq(p
);
8527 if (task_on_rq_queued(p
)) {
8529 * We were most likely switched from sched_rt, so
8530 * kick off the schedule if running, otherwise just see
8531 * if we can still preempt the current task.
8536 check_preempt_curr(rq
, p
, 0);
8540 /* Account for a task changing its policy or group.
8542 * This routine is mostly called to set cfs_rq->curr field when a task
8543 * migrates between groups/classes.
8545 static void set_curr_task_fair(struct rq
*rq
)
8547 struct sched_entity
*se
= &rq
->curr
->se
;
8549 for_each_sched_entity(se
) {
8550 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
8552 set_next_entity(cfs_rq
, se
);
8553 /* ensure bandwidth has been allocated on our new cfs_rq */
8554 account_cfs_rq_runtime(cfs_rq
, 0);
8558 void init_cfs_rq(struct cfs_rq
*cfs_rq
)
8560 cfs_rq
->tasks_timeline
= RB_ROOT
;
8561 cfs_rq
->min_vruntime
= (u64
)(-(1LL << 20));
8562 #ifndef CONFIG_64BIT
8563 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
8566 atomic_long_set(&cfs_rq
->removed_load_avg
, 0);
8567 atomic_long_set(&cfs_rq
->removed_util_avg
, 0);
8571 #ifdef CONFIG_FAIR_GROUP_SCHED
8572 static void task_set_group_fair(struct task_struct
*p
)
8574 struct sched_entity
*se
= &p
->se
;
8576 set_task_rq(p
, task_cpu(p
));
8577 se
->depth
= se
->parent
? se
->parent
->depth
+ 1 : 0;
8580 static void task_move_group_fair(struct task_struct
*p
)
8582 detach_task_cfs_rq(p
);
8583 set_task_rq(p
, task_cpu(p
));
8586 /* Tell se's cfs_rq has been changed -- migrated */
8587 p
->se
.avg
.last_update_time
= 0;
8589 attach_task_cfs_rq(p
);
8592 static void task_change_group_fair(struct task_struct
*p
, int type
)
8595 case TASK_SET_GROUP
:
8596 task_set_group_fair(p
);
8599 case TASK_MOVE_GROUP
:
8600 task_move_group_fair(p
);
8605 void free_fair_sched_group(struct task_group
*tg
)
8609 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8611 for_each_possible_cpu(i
) {
8613 kfree(tg
->cfs_rq
[i
]);
8622 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8624 struct sched_entity
*se
;
8625 struct cfs_rq
*cfs_rq
;
8629 tg
->cfs_rq
= kzalloc(sizeof(cfs_rq
) * nr_cpu_ids
, GFP_KERNEL
);
8632 tg
->se
= kzalloc(sizeof(se
) * nr_cpu_ids
, GFP_KERNEL
);
8636 tg
->shares
= NICE_0_LOAD
;
8638 init_cfs_bandwidth(tg_cfs_bandwidth(tg
));
8640 for_each_possible_cpu(i
) {
8643 cfs_rq
= kzalloc_node(sizeof(struct cfs_rq
),
8644 GFP_KERNEL
, cpu_to_node(i
));
8648 se
= kzalloc_node(sizeof(struct sched_entity
),
8649 GFP_KERNEL
, cpu_to_node(i
));
8653 init_cfs_rq(cfs_rq
);
8654 init_tg_cfs_entry(tg
, cfs_rq
, se
, i
, parent
->se
[i
]);
8655 init_entity_runnable_average(se
);
8666 void online_fair_sched_group(struct task_group
*tg
)
8668 struct sched_entity
*se
;
8672 for_each_possible_cpu(i
) {
8676 raw_spin_lock_irq(&rq
->lock
);
8677 post_init_entity_util_avg(se
);
8678 sync_throttle(tg
, i
);
8679 raw_spin_unlock_irq(&rq
->lock
);
8683 void unregister_fair_sched_group(struct task_group
*tg
)
8685 unsigned long flags
;
8689 for_each_possible_cpu(cpu
) {
8691 remove_entity_load_avg(tg
->se
[cpu
]);
8694 * Only empty task groups can be destroyed; so we can speculatively
8695 * check on_list without danger of it being re-added.
8697 if (!tg
->cfs_rq
[cpu
]->on_list
)
8702 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8703 list_del_leaf_cfs_rq(tg
->cfs_rq
[cpu
]);
8704 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8708 void init_tg_cfs_entry(struct task_group
*tg
, struct cfs_rq
*cfs_rq
,
8709 struct sched_entity
*se
, int cpu
,
8710 struct sched_entity
*parent
)
8712 struct rq
*rq
= cpu_rq(cpu
);
8716 init_cfs_rq_runtime(cfs_rq
);
8718 tg
->cfs_rq
[cpu
] = cfs_rq
;
8721 /* se could be NULL for root_task_group */
8726 se
->cfs_rq
= &rq
->cfs
;
8729 se
->cfs_rq
= parent
->my_q
;
8730 se
->depth
= parent
->depth
+ 1;
8734 /* guarantee group entities always have weight */
8735 update_load_set(&se
->load
, NICE_0_LOAD
);
8736 se
->parent
= parent
;
8739 static DEFINE_MUTEX(shares_mutex
);
8741 int sched_group_set_shares(struct task_group
*tg
, unsigned long shares
)
8744 unsigned long flags
;
8747 * We can't change the weight of the root cgroup.
8752 shares
= clamp(shares
, scale_load(MIN_SHARES
), scale_load(MAX_SHARES
));
8754 mutex_lock(&shares_mutex
);
8755 if (tg
->shares
== shares
)
8758 tg
->shares
= shares
;
8759 for_each_possible_cpu(i
) {
8760 struct rq
*rq
= cpu_rq(i
);
8761 struct sched_entity
*se
;
8764 /* Propagate contribution to hierarchy */
8765 raw_spin_lock_irqsave(&rq
->lock
, flags
);
8767 /* Possible calls to update_curr() need rq clock */
8768 update_rq_clock(rq
);
8769 for_each_sched_entity(se
)
8770 update_cfs_shares(group_cfs_rq(se
));
8771 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
8775 mutex_unlock(&shares_mutex
);
8778 #else /* CONFIG_FAIR_GROUP_SCHED */
8780 void free_fair_sched_group(struct task_group
*tg
) { }
8782 int alloc_fair_sched_group(struct task_group
*tg
, struct task_group
*parent
)
8787 void online_fair_sched_group(struct task_group
*tg
) { }
8789 void unregister_fair_sched_group(struct task_group
*tg
) { }
8791 #endif /* CONFIG_FAIR_GROUP_SCHED */
8794 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
8796 struct sched_entity
*se
= &task
->se
;
8797 unsigned int rr_interval
= 0;
8800 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
8803 if (rq
->cfs
.load
.weight
)
8804 rr_interval
= NS_TO_JIFFIES(sched_slice(cfs_rq_of(se
), se
));
8810 * All the scheduling class methods:
8812 const struct sched_class fair_sched_class
= {
8813 .next
= &idle_sched_class
,
8814 .enqueue_task
= enqueue_task_fair
,
8815 .dequeue_task
= dequeue_task_fair
,
8816 .yield_task
= yield_task_fair
,
8817 .yield_to_task
= yield_to_task_fair
,
8819 .check_preempt_curr
= check_preempt_wakeup
,
8821 .pick_next_task
= pick_next_task_fair
,
8822 .put_prev_task
= put_prev_task_fair
,
8825 .select_task_rq
= select_task_rq_fair
,
8826 .migrate_task_rq
= migrate_task_rq_fair
,
8828 .rq_online
= rq_online_fair
,
8829 .rq_offline
= rq_offline_fair
,
8831 .task_dead
= task_dead_fair
,
8832 .set_cpus_allowed
= set_cpus_allowed_common
,
8835 .set_curr_task
= set_curr_task_fair
,
8836 .task_tick
= task_tick_fair
,
8837 .task_fork
= task_fork_fair
,
8839 .prio_changed
= prio_changed_fair
,
8840 .switched_from
= switched_from_fair
,
8841 .switched_to
= switched_to_fair
,
8843 .get_rr_interval
= get_rr_interval_fair
,
8845 .update_curr
= update_curr_fair
,
8847 #ifdef CONFIG_FAIR_GROUP_SCHED
8848 .task_change_group
= task_change_group_fair
,
8852 #ifdef CONFIG_SCHED_DEBUG
8853 void print_cfs_stats(struct seq_file
*m
, int cpu
)
8855 struct cfs_rq
*cfs_rq
;
8858 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
8859 print_cfs_rq(m
, cpu
, cfs_rq
);
8863 #ifdef CONFIG_NUMA_BALANCING
8864 void show_numa_stats(struct task_struct
*p
, struct seq_file
*m
)
8867 unsigned long tsf
= 0, tpf
= 0, gsf
= 0, gpf
= 0;
8869 for_each_online_node(node
) {
8870 if (p
->numa_faults
) {
8871 tsf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 0)];
8872 tpf
= p
->numa_faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8874 if (p
->numa_group
) {
8875 gsf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 0)],
8876 gpf
= p
->numa_group
->faults
[task_faults_idx(NUMA_MEM
, node
, 1)];
8878 print_numa_stats(m
, node
, tsf
, tpf
, gsf
, gpf
);
8881 #endif /* CONFIG_NUMA_BALANCING */
8882 #endif /* CONFIG_SCHED_DEBUG */
8884 __init
void init_sched_fair_class(void)
8887 open_softirq(SCHED_SOFTIRQ
, run_rebalance_domains
);
8889 #ifdef CONFIG_NO_HZ_COMMON
8890 nohz
.next_balance
= jiffies
;
8891 zalloc_cpumask_var(&nohz
.idle_cpus_mask
, GFP_NOWAIT
);