2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
6 * Interactivity improvements by Mike Galbraith
7 * (C) 2007 Mike Galbraith <efault@gmx.de>
9 * Various enhancements by Dmitry Adamushko.
10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
12 * Group scheduling enhancements by Srivatsa Vaddagiri
13 * Copyright IBM Corporation, 2007
14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
16 * Scaled math optimizations by Thomas Gleixner
17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra
20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
23 #include <linux/latencytop.h>
24 #include <linux/sched.h>
25 #include <linux/cpumask.h>
28 * Targeted preemption latency for CPU-bound tasks:
29 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
31 * NOTE: this latency value is not the same as the concept of
32 * 'timeslice length' - timeslices in CFS are of variable length
33 * and have no persistent notion like in traditional, time-slice
34 * based scheduling concepts.
36 * (to see the precise effective timeslice length of your workload,
37 * run vmstat and monitor the context-switches (cs) field)
39 unsigned int sysctl_sched_latency
= 6000000ULL;
40 unsigned int normalized_sysctl_sched_latency
= 6000000ULL;
43 * The initial- and re-scaling of tunables is configurable
44 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
47 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
48 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
49 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
51 enum sched_tunable_scaling sysctl_sched_tunable_scaling
52 = SCHED_TUNABLESCALING_LOG
;
55 * Minimal preemption granularity for CPU-bound tasks:
56 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
58 unsigned int sysctl_sched_min_granularity
= 750000ULL;
59 unsigned int normalized_sysctl_sched_min_granularity
= 750000ULL;
62 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
64 static unsigned int sched_nr_latency
= 8;
67 * After fork, child runs first. If set to 0 (default) then
68 * parent will (try to) run first.
70 unsigned int sysctl_sched_child_runs_first __read_mostly
;
73 * SCHED_OTHER wake-up granularity.
74 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
76 * This option delays the preemption effects of decoupled workloads
77 * and reduces their over-scheduling. Synchronous workloads will still
78 * have immediate wakeup/sleep latencies.
80 unsigned int sysctl_sched_wakeup_granularity
= 1000000UL;
81 unsigned int normalized_sysctl_sched_wakeup_granularity
= 1000000UL;
83 const_debug
unsigned int sysctl_sched_migration_cost
= 500000UL;
86 * The exponential sliding window over which load is averaged for shares
90 unsigned int __read_mostly sysctl_sched_shares_window
= 10000000UL;
92 #ifdef CONFIG_CFS_BANDWIDTH
94 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
95 * each time a cfs_rq requests quota.
97 * Note: in the case that the slice exceeds the runtime remaining (either due
98 * to consumption or the quota being specified to be smaller than the slice)
99 * we will always only issue the remaining available time.
101 * default: 5 msec, units: microseconds
103 unsigned int sysctl_sched_cfs_bandwidth_slice
= 5000UL;
106 static const struct sched_class fair_sched_class
;
108 /**************************************************************
109 * CFS operations on generic schedulable entities:
112 #ifdef CONFIG_FAIR_GROUP_SCHED
114 /* cpu runqueue to which this cfs_rq is attached */
115 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
120 /* An entity is a task if it doesn't "own" a runqueue */
121 #define entity_is_task(se) (!se->my_q)
123 static inline struct task_struct
*task_of(struct sched_entity
*se
)
125 #ifdef CONFIG_SCHED_DEBUG
126 WARN_ON_ONCE(!entity_is_task(se
));
128 return container_of(se
, struct task_struct
, se
);
131 /* Walk up scheduling entities hierarchy */
132 #define for_each_sched_entity(se) \
133 for (; se; se = se->parent)
135 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
140 /* runqueue on which this entity is (to be) queued */
141 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
146 /* runqueue "owned" by this group */
147 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
152 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
154 if (!cfs_rq
->on_list
) {
156 * Ensure we either appear before our parent (if already
157 * enqueued) or force our parent to appear after us when it is
158 * enqueued. The fact that we always enqueue bottom-up
159 * reduces this to two cases.
161 if (cfs_rq
->tg
->parent
&&
162 cfs_rq
->tg
->parent
->cfs_rq
[cpu_of(rq_of(cfs_rq
))]->on_list
) {
163 list_add_rcu(&cfs_rq
->leaf_cfs_rq_list
,
164 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
166 list_add_tail_rcu(&cfs_rq
->leaf_cfs_rq_list
,
167 &rq_of(cfs_rq
)->leaf_cfs_rq_list
);
174 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
176 if (cfs_rq
->on_list
) {
177 list_del_rcu(&cfs_rq
->leaf_cfs_rq_list
);
182 /* Iterate thr' all leaf cfs_rq's on a runqueue */
183 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
184 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
186 /* Do the two (enqueued) entities belong to the same group ? */
188 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
190 if (se
->cfs_rq
== pse
->cfs_rq
)
196 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
201 /* return depth at which a sched entity is present in the hierarchy */
202 static inline int depth_se(struct sched_entity
*se
)
206 for_each_sched_entity(se
)
213 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
215 int se_depth
, pse_depth
;
218 * preemption test can be made between sibling entities who are in the
219 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
220 * both tasks until we find their ancestors who are siblings of common
224 /* First walk up until both entities are at same depth */
225 se_depth
= depth_se(*se
);
226 pse_depth
= depth_se(*pse
);
228 while (se_depth
> pse_depth
) {
230 *se
= parent_entity(*se
);
233 while (pse_depth
> se_depth
) {
235 *pse
= parent_entity(*pse
);
238 while (!is_same_group(*se
, *pse
)) {
239 *se
= parent_entity(*se
);
240 *pse
= parent_entity(*pse
);
244 #else /* !CONFIG_FAIR_GROUP_SCHED */
246 static inline struct task_struct
*task_of(struct sched_entity
*se
)
248 return container_of(se
, struct task_struct
, se
);
251 static inline struct rq
*rq_of(struct cfs_rq
*cfs_rq
)
253 return container_of(cfs_rq
, struct rq
, cfs
);
256 #define entity_is_task(se) 1
258 #define for_each_sched_entity(se) \
259 for (; se; se = NULL)
261 static inline struct cfs_rq
*task_cfs_rq(struct task_struct
*p
)
263 return &task_rq(p
)->cfs
;
266 static inline struct cfs_rq
*cfs_rq_of(struct sched_entity
*se
)
268 struct task_struct
*p
= task_of(se
);
269 struct rq
*rq
= task_rq(p
);
274 /* runqueue "owned" by this group */
275 static inline struct cfs_rq
*group_cfs_rq(struct sched_entity
*grp
)
280 static inline void list_add_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
284 static inline void list_del_leaf_cfs_rq(struct cfs_rq
*cfs_rq
)
288 #define for_each_leaf_cfs_rq(rq, cfs_rq) \
289 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
292 is_same_group(struct sched_entity
*se
, struct sched_entity
*pse
)
297 static inline struct sched_entity
*parent_entity(struct sched_entity
*se
)
303 find_matching_se(struct sched_entity
**se
, struct sched_entity
**pse
)
307 #endif /* CONFIG_FAIR_GROUP_SCHED */
309 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
,
310 unsigned long delta_exec
);
312 /**************************************************************
313 * Scheduling class tree data structure manipulation methods:
316 static inline u64
max_vruntime(u64 min_vruntime
, u64 vruntime
)
318 s64 delta
= (s64
)(vruntime
- min_vruntime
);
320 min_vruntime
= vruntime
;
325 static inline u64
min_vruntime(u64 min_vruntime
, u64 vruntime
)
327 s64 delta
= (s64
)(vruntime
- min_vruntime
);
329 min_vruntime
= vruntime
;
334 static inline int entity_before(struct sched_entity
*a
,
335 struct sched_entity
*b
)
337 return (s64
)(a
->vruntime
- b
->vruntime
) < 0;
340 static void update_min_vruntime(struct cfs_rq
*cfs_rq
)
342 u64 vruntime
= cfs_rq
->min_vruntime
;
345 vruntime
= cfs_rq
->curr
->vruntime
;
347 if (cfs_rq
->rb_leftmost
) {
348 struct sched_entity
*se
= rb_entry(cfs_rq
->rb_leftmost
,
353 vruntime
= se
->vruntime
;
355 vruntime
= min_vruntime(vruntime
, se
->vruntime
);
358 cfs_rq
->min_vruntime
= max_vruntime(cfs_rq
->min_vruntime
, vruntime
);
361 cfs_rq
->min_vruntime_copy
= cfs_rq
->min_vruntime
;
366 * Enqueue an entity into the rb-tree:
368 static void __enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
370 struct rb_node
**link
= &cfs_rq
->tasks_timeline
.rb_node
;
371 struct rb_node
*parent
= NULL
;
372 struct sched_entity
*entry
;
376 * Find the right place in the rbtree:
380 entry
= rb_entry(parent
, struct sched_entity
, run_node
);
382 * We dont care about collisions. Nodes with
383 * the same key stay together.
385 if (entity_before(se
, entry
)) {
386 link
= &parent
->rb_left
;
388 link
= &parent
->rb_right
;
394 * Maintain a cache of leftmost tree entries (it is frequently
398 cfs_rq
->rb_leftmost
= &se
->run_node
;
400 rb_link_node(&se
->run_node
, parent
, link
);
401 rb_insert_color(&se
->run_node
, &cfs_rq
->tasks_timeline
);
404 static void __dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
406 if (cfs_rq
->rb_leftmost
== &se
->run_node
) {
407 struct rb_node
*next_node
;
409 next_node
= rb_next(&se
->run_node
);
410 cfs_rq
->rb_leftmost
= next_node
;
413 rb_erase(&se
->run_node
, &cfs_rq
->tasks_timeline
);
416 static struct sched_entity
*__pick_first_entity(struct cfs_rq
*cfs_rq
)
418 struct rb_node
*left
= cfs_rq
->rb_leftmost
;
423 return rb_entry(left
, struct sched_entity
, run_node
);
426 static struct sched_entity
*__pick_next_entity(struct sched_entity
*se
)
428 struct rb_node
*next
= rb_next(&se
->run_node
);
433 return rb_entry(next
, struct sched_entity
, run_node
);
436 #ifdef CONFIG_SCHED_DEBUG
437 static struct sched_entity
*__pick_last_entity(struct cfs_rq
*cfs_rq
)
439 struct rb_node
*last
= rb_last(&cfs_rq
->tasks_timeline
);
444 return rb_entry(last
, struct sched_entity
, run_node
);
447 /**************************************************************
448 * Scheduling class statistics methods:
451 int sched_proc_update_handler(struct ctl_table
*table
, int write
,
452 void __user
*buffer
, size_t *lenp
,
455 int ret
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
456 int factor
= get_update_sysctl_factor();
461 sched_nr_latency
= DIV_ROUND_UP(sysctl_sched_latency
,
462 sysctl_sched_min_granularity
);
464 #define WRT_SYSCTL(name) \
465 (normalized_sysctl_##name = sysctl_##name / (factor))
466 WRT_SYSCTL(sched_min_granularity
);
467 WRT_SYSCTL(sched_latency
);
468 WRT_SYSCTL(sched_wakeup_granularity
);
478 static inline unsigned long
479 calc_delta_fair(unsigned long delta
, struct sched_entity
*se
)
481 if (unlikely(se
->load
.weight
!= NICE_0_LOAD
))
482 delta
= calc_delta_mine(delta
, NICE_0_LOAD
, &se
->load
);
488 * The idea is to set a period in which each task runs once.
490 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
491 * this period because otherwise the slices get too small.
493 * p = (nr <= nl) ? l : l*nr/nl
495 static u64
__sched_period(unsigned long nr_running
)
497 u64 period
= sysctl_sched_latency
;
498 unsigned long nr_latency
= sched_nr_latency
;
500 if (unlikely(nr_running
> nr_latency
)) {
501 period
= sysctl_sched_min_granularity
;
502 period
*= nr_running
;
509 * We calculate the wall-time slice from the period by taking a part
510 * proportional to the weight.
514 static u64
sched_slice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
516 u64 slice
= __sched_period(cfs_rq
->nr_running
+ !se
->on_rq
);
518 for_each_sched_entity(se
) {
519 struct load_weight
*load
;
520 struct load_weight lw
;
522 cfs_rq
= cfs_rq_of(se
);
523 load
= &cfs_rq
->load
;
525 if (unlikely(!se
->on_rq
)) {
528 update_load_add(&lw
, se
->load
.weight
);
531 slice
= calc_delta_mine(slice
, se
->load
.weight
, load
);
537 * We calculate the vruntime slice of a to be inserted task
541 static u64
sched_vslice(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
543 return calc_delta_fair(sched_slice(cfs_rq
, se
), se
);
546 static void update_cfs_load(struct cfs_rq
*cfs_rq
, int global_update
);
547 static void update_cfs_shares(struct cfs_rq
*cfs_rq
);
550 * Update the current task's runtime statistics. Skip current tasks that
551 * are not in our scheduling class.
554 __update_curr(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
,
555 unsigned long delta_exec
)
557 unsigned long delta_exec_weighted
;
559 schedstat_set(curr
->statistics
.exec_max
,
560 max((u64
)delta_exec
, curr
->statistics
.exec_max
));
562 curr
->sum_exec_runtime
+= delta_exec
;
563 schedstat_add(cfs_rq
, exec_clock
, delta_exec
);
564 delta_exec_weighted
= calc_delta_fair(delta_exec
, curr
);
566 curr
->vruntime
+= delta_exec_weighted
;
567 update_min_vruntime(cfs_rq
);
569 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
570 cfs_rq
->load_unacc_exec_time
+= delta_exec
;
574 static void update_curr(struct cfs_rq
*cfs_rq
)
576 struct sched_entity
*curr
= cfs_rq
->curr
;
577 u64 now
= rq_of(cfs_rq
)->clock_task
;
578 unsigned long delta_exec
;
584 * Get the amount of time the current task was running
585 * since the last time we changed load (this cannot
586 * overflow on 32 bits):
588 delta_exec
= (unsigned long)(now
- curr
->exec_start
);
592 __update_curr(cfs_rq
, curr
, delta_exec
);
593 curr
->exec_start
= now
;
595 if (entity_is_task(curr
)) {
596 struct task_struct
*curtask
= task_of(curr
);
598 trace_sched_stat_runtime(curtask
, delta_exec
, curr
->vruntime
);
599 cpuacct_charge(curtask
, delta_exec
);
600 account_group_exec_runtime(curtask
, delta_exec
);
603 account_cfs_rq_runtime(cfs_rq
, delta_exec
);
607 update_stats_wait_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
609 schedstat_set(se
->statistics
.wait_start
, rq_of(cfs_rq
)->clock
);
613 * Task is being enqueued - update stats:
615 static void update_stats_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
618 * Are we enqueueing a waiting task? (for current tasks
619 * a dequeue/enqueue event is a NOP)
621 if (se
!= cfs_rq
->curr
)
622 update_stats_wait_start(cfs_rq
, se
);
626 update_stats_wait_end(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
628 schedstat_set(se
->statistics
.wait_max
, max(se
->statistics
.wait_max
,
629 rq_of(cfs_rq
)->clock
- se
->statistics
.wait_start
));
630 schedstat_set(se
->statistics
.wait_count
, se
->statistics
.wait_count
+ 1);
631 schedstat_set(se
->statistics
.wait_sum
, se
->statistics
.wait_sum
+
632 rq_of(cfs_rq
)->clock
- se
->statistics
.wait_start
);
633 #ifdef CONFIG_SCHEDSTATS
634 if (entity_is_task(se
)) {
635 trace_sched_stat_wait(task_of(se
),
636 rq_of(cfs_rq
)->clock
- se
->statistics
.wait_start
);
639 schedstat_set(se
->statistics
.wait_start
, 0);
643 update_stats_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
646 * Mark the end of the wait period if dequeueing a
649 if (se
!= cfs_rq
->curr
)
650 update_stats_wait_end(cfs_rq
, se
);
654 * We are picking a new current task - update its stats:
657 update_stats_curr_start(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
660 * We are starting a new run period:
662 se
->exec_start
= rq_of(cfs_rq
)->clock_task
;
665 /**************************************************
666 * Scheduling class queueing methods:
669 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
671 add_cfs_task_weight(struct cfs_rq
*cfs_rq
, unsigned long weight
)
673 cfs_rq
->task_weight
+= weight
;
677 add_cfs_task_weight(struct cfs_rq
*cfs_rq
, unsigned long weight
)
683 account_entity_enqueue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
685 update_load_add(&cfs_rq
->load
, se
->load
.weight
);
686 if (!parent_entity(se
))
687 inc_cpu_load(rq_of(cfs_rq
), se
->load
.weight
);
688 if (entity_is_task(se
)) {
689 add_cfs_task_weight(cfs_rq
, se
->load
.weight
);
690 list_add(&se
->group_node
, &cfs_rq
->tasks
);
692 cfs_rq
->nr_running
++;
696 account_entity_dequeue(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
698 update_load_sub(&cfs_rq
->load
, se
->load
.weight
);
699 if (!parent_entity(se
))
700 dec_cpu_load(rq_of(cfs_rq
), se
->load
.weight
);
701 if (entity_is_task(se
)) {
702 add_cfs_task_weight(cfs_rq
, -se
->load
.weight
);
703 list_del_init(&se
->group_node
);
705 cfs_rq
->nr_running
--;
708 #ifdef CONFIG_FAIR_GROUP_SCHED
710 static void update_cfs_rq_load_contribution(struct cfs_rq
*cfs_rq
,
713 struct task_group
*tg
= cfs_rq
->tg
;
716 load_avg
= div64_u64(cfs_rq
->load_avg
, cfs_rq
->load_period
+1);
717 load_avg
-= cfs_rq
->load_contribution
;
719 if (global_update
|| abs(load_avg
) > cfs_rq
->load_contribution
/ 8) {
720 atomic_add(load_avg
, &tg
->load_weight
);
721 cfs_rq
->load_contribution
+= load_avg
;
725 static void update_cfs_load(struct cfs_rq
*cfs_rq
, int global_update
)
727 u64 period
= sysctl_sched_shares_window
;
729 unsigned long load
= cfs_rq
->load
.weight
;
731 if (cfs_rq
->tg
== &root_task_group
)
734 now
= rq_of(cfs_rq
)->clock_task
;
735 delta
= now
- cfs_rq
->load_stamp
;
737 /* truncate load history at 4 idle periods */
738 if (cfs_rq
->load_stamp
> cfs_rq
->load_last
&&
739 now
- cfs_rq
->load_last
> 4 * period
) {
740 cfs_rq
->load_period
= 0;
741 cfs_rq
->load_avg
= 0;
745 cfs_rq
->load_stamp
= now
;
746 cfs_rq
->load_unacc_exec_time
= 0;
747 cfs_rq
->load_period
+= delta
;
749 cfs_rq
->load_last
= now
;
750 cfs_rq
->load_avg
+= delta
* load
;
753 /* consider updating load contribution on each fold or truncate */
754 if (global_update
|| cfs_rq
->load_period
> period
755 || !cfs_rq
->load_period
)
756 update_cfs_rq_load_contribution(cfs_rq
, global_update
);
758 while (cfs_rq
->load_period
> period
) {
760 * Inline assembly required to prevent the compiler
761 * optimising this loop into a divmod call.
762 * See __iter_div_u64_rem() for another example of this.
764 asm("" : "+rm" (cfs_rq
->load_period
));
765 cfs_rq
->load_period
/= 2;
766 cfs_rq
->load_avg
/= 2;
769 if (!cfs_rq
->curr
&& !cfs_rq
->nr_running
&& !cfs_rq
->load_avg
)
770 list_del_leaf_cfs_rq(cfs_rq
);
773 static long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
775 long load_weight
, load
, shares
;
777 load
= cfs_rq
->load
.weight
;
779 load_weight
= atomic_read(&tg
->load_weight
);
781 load_weight
-= cfs_rq
->load_contribution
;
783 shares
= (tg
->shares
* load
);
785 shares
/= load_weight
;
787 if (shares
< MIN_SHARES
)
789 if (shares
> tg
->shares
)
795 static void update_entity_shares_tick(struct cfs_rq
*cfs_rq
)
797 if (cfs_rq
->load_unacc_exec_time
> sysctl_sched_shares_window
) {
798 update_cfs_load(cfs_rq
, 0);
799 update_cfs_shares(cfs_rq
);
802 # else /* CONFIG_SMP */
803 static void update_cfs_load(struct cfs_rq
*cfs_rq
, int global_update
)
807 static inline long calc_cfs_shares(struct cfs_rq
*cfs_rq
, struct task_group
*tg
)
812 static inline void update_entity_shares_tick(struct cfs_rq
*cfs_rq
)
815 # endif /* CONFIG_SMP */
816 static void reweight_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
,
817 unsigned long weight
)
820 /* commit outstanding execution time */
821 if (cfs_rq
->curr
== se
)
823 account_entity_dequeue(cfs_rq
, se
);
826 update_load_set(&se
->load
, weight
);
829 account_entity_enqueue(cfs_rq
, se
);
832 static void update_cfs_shares(struct cfs_rq
*cfs_rq
)
834 struct task_group
*tg
;
835 struct sched_entity
*se
;
839 se
= tg
->se
[cpu_of(rq_of(cfs_rq
))];
843 if (likely(se
->load
.weight
== tg
->shares
))
846 shares
= calc_cfs_shares(cfs_rq
, tg
);
848 reweight_entity(cfs_rq_of(se
), se
, shares
);
850 #else /* CONFIG_FAIR_GROUP_SCHED */
851 static void update_cfs_load(struct cfs_rq
*cfs_rq
, int global_update
)
855 static inline void update_cfs_shares(struct cfs_rq
*cfs_rq
)
859 static inline void update_entity_shares_tick(struct cfs_rq
*cfs_rq
)
862 #endif /* CONFIG_FAIR_GROUP_SCHED */
864 static void enqueue_sleeper(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
866 #ifdef CONFIG_SCHEDSTATS
867 struct task_struct
*tsk
= NULL
;
869 if (entity_is_task(se
))
872 if (se
->statistics
.sleep_start
) {
873 u64 delta
= rq_of(cfs_rq
)->clock
- se
->statistics
.sleep_start
;
878 if (unlikely(delta
> se
->statistics
.sleep_max
))
879 se
->statistics
.sleep_max
= delta
;
881 se
->statistics
.sleep_start
= 0;
882 se
->statistics
.sum_sleep_runtime
+= delta
;
885 account_scheduler_latency(tsk
, delta
>> 10, 1);
886 trace_sched_stat_sleep(tsk
, delta
);
889 if (se
->statistics
.block_start
) {
890 u64 delta
= rq_of(cfs_rq
)->clock
- se
->statistics
.block_start
;
895 if (unlikely(delta
> se
->statistics
.block_max
))
896 se
->statistics
.block_max
= delta
;
898 se
->statistics
.block_start
= 0;
899 se
->statistics
.sum_sleep_runtime
+= delta
;
902 if (tsk
->in_iowait
) {
903 se
->statistics
.iowait_sum
+= delta
;
904 se
->statistics
.iowait_count
++;
905 trace_sched_stat_iowait(tsk
, delta
);
909 * Blocking time is in units of nanosecs, so shift by
910 * 20 to get a milliseconds-range estimation of the
911 * amount of time that the task spent sleeping:
913 if (unlikely(prof_on
== SLEEP_PROFILING
)) {
914 profile_hits(SLEEP_PROFILING
,
915 (void *)get_wchan(tsk
),
918 account_scheduler_latency(tsk
, delta
>> 10, 0);
924 static void check_spread(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
926 #ifdef CONFIG_SCHED_DEBUG
927 s64 d
= se
->vruntime
- cfs_rq
->min_vruntime
;
932 if (d
> 3*sysctl_sched_latency
)
933 schedstat_inc(cfs_rq
, nr_spread_over
);
938 place_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int initial
)
940 u64 vruntime
= cfs_rq
->min_vruntime
;
943 * The 'current' period is already promised to the current tasks,
944 * however the extra weight of the new task will slow them down a
945 * little, place the new task so that it fits in the slot that
946 * stays open at the end.
948 if (initial
&& sched_feat(START_DEBIT
))
949 vruntime
+= sched_vslice(cfs_rq
, se
);
951 /* sleeps up to a single latency don't count. */
953 unsigned long thresh
= sysctl_sched_latency
;
956 * Halve their sleep time's effect, to allow
957 * for a gentler effect of sleepers:
959 if (sched_feat(GENTLE_FAIR_SLEEPERS
))
965 /* ensure we never gain time by being placed backwards. */
966 vruntime
= max_vruntime(se
->vruntime
, vruntime
);
968 se
->vruntime
= vruntime
;
972 enqueue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
975 * Update the normalized vruntime before updating min_vruntime
976 * through callig update_curr().
978 if (!(flags
& ENQUEUE_WAKEUP
) || (flags
& ENQUEUE_WAKING
))
979 se
->vruntime
+= cfs_rq
->min_vruntime
;
982 * Update run-time statistics of the 'current'.
985 update_cfs_load(cfs_rq
, 0);
986 account_entity_enqueue(cfs_rq
, se
);
987 update_cfs_shares(cfs_rq
);
989 if (flags
& ENQUEUE_WAKEUP
) {
990 place_entity(cfs_rq
, se
, 0);
991 enqueue_sleeper(cfs_rq
, se
);
994 update_stats_enqueue(cfs_rq
, se
);
995 check_spread(cfs_rq
, se
);
996 if (se
!= cfs_rq
->curr
)
997 __enqueue_entity(cfs_rq
, se
);
1000 if (cfs_rq
->nr_running
== 1)
1001 list_add_leaf_cfs_rq(cfs_rq
);
1004 static void __clear_buddies_last(struct sched_entity
*se
)
1006 for_each_sched_entity(se
) {
1007 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
1008 if (cfs_rq
->last
== se
)
1009 cfs_rq
->last
= NULL
;
1015 static void __clear_buddies_next(struct sched_entity
*se
)
1017 for_each_sched_entity(se
) {
1018 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
1019 if (cfs_rq
->next
== se
)
1020 cfs_rq
->next
= NULL
;
1026 static void __clear_buddies_skip(struct sched_entity
*se
)
1028 for_each_sched_entity(se
) {
1029 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
1030 if (cfs_rq
->skip
== se
)
1031 cfs_rq
->skip
= NULL
;
1037 static void clear_buddies(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
1039 if (cfs_rq
->last
== se
)
1040 __clear_buddies_last(se
);
1042 if (cfs_rq
->next
== se
)
1043 __clear_buddies_next(se
);
1045 if (cfs_rq
->skip
== se
)
1046 __clear_buddies_skip(se
);
1050 dequeue_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
, int flags
)
1053 * Update run-time statistics of the 'current'.
1055 update_curr(cfs_rq
);
1057 update_stats_dequeue(cfs_rq
, se
);
1058 if (flags
& DEQUEUE_SLEEP
) {
1059 #ifdef CONFIG_SCHEDSTATS
1060 if (entity_is_task(se
)) {
1061 struct task_struct
*tsk
= task_of(se
);
1063 if (tsk
->state
& TASK_INTERRUPTIBLE
)
1064 se
->statistics
.sleep_start
= rq_of(cfs_rq
)->clock
;
1065 if (tsk
->state
& TASK_UNINTERRUPTIBLE
)
1066 se
->statistics
.block_start
= rq_of(cfs_rq
)->clock
;
1071 clear_buddies(cfs_rq
, se
);
1073 if (se
!= cfs_rq
->curr
)
1074 __dequeue_entity(cfs_rq
, se
);
1076 update_cfs_load(cfs_rq
, 0);
1077 account_entity_dequeue(cfs_rq
, se
);
1080 * Normalize the entity after updating the min_vruntime because the
1081 * update can refer to the ->curr item and we need to reflect this
1082 * movement in our normalized position.
1084 if (!(flags
& DEQUEUE_SLEEP
))
1085 se
->vruntime
-= cfs_rq
->min_vruntime
;
1087 update_min_vruntime(cfs_rq
);
1088 update_cfs_shares(cfs_rq
);
1092 * Preempt the current task with a newly woken task if needed:
1095 check_preempt_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
)
1097 unsigned long ideal_runtime
, delta_exec
;
1099 ideal_runtime
= sched_slice(cfs_rq
, curr
);
1100 delta_exec
= curr
->sum_exec_runtime
- curr
->prev_sum_exec_runtime
;
1101 if (delta_exec
> ideal_runtime
) {
1102 resched_task(rq_of(cfs_rq
)->curr
);
1104 * The current task ran long enough, ensure it doesn't get
1105 * re-elected due to buddy favours.
1107 clear_buddies(cfs_rq
, curr
);
1112 * Ensure that a task that missed wakeup preemption by a
1113 * narrow margin doesn't have to wait for a full slice.
1114 * This also mitigates buddy induced latencies under load.
1116 if (delta_exec
< sysctl_sched_min_granularity
)
1119 if (cfs_rq
->nr_running
> 1) {
1120 struct sched_entity
*se
= __pick_first_entity(cfs_rq
);
1121 s64 delta
= curr
->vruntime
- se
->vruntime
;
1126 if (delta
> ideal_runtime
)
1127 resched_task(rq_of(cfs_rq
)->curr
);
1132 set_next_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*se
)
1134 /* 'current' is not kept within the tree. */
1137 * Any task has to be enqueued before it get to execute on
1138 * a CPU. So account for the time it spent waiting on the
1141 update_stats_wait_end(cfs_rq
, se
);
1142 __dequeue_entity(cfs_rq
, se
);
1145 update_stats_curr_start(cfs_rq
, se
);
1147 #ifdef CONFIG_SCHEDSTATS
1149 * Track our maximum slice length, if the CPU's load is at
1150 * least twice that of our own weight (i.e. dont track it
1151 * when there are only lesser-weight tasks around):
1153 if (rq_of(cfs_rq
)->load
.weight
>= 2*se
->load
.weight
) {
1154 se
->statistics
.slice_max
= max(se
->statistics
.slice_max
,
1155 se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
);
1158 se
->prev_sum_exec_runtime
= se
->sum_exec_runtime
;
1162 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
);
1165 * Pick the next process, keeping these things in mind, in this order:
1166 * 1) keep things fair between processes/task groups
1167 * 2) pick the "next" process, since someone really wants that to run
1168 * 3) pick the "last" process, for cache locality
1169 * 4) do not run the "skip" process, if something else is available
1171 static struct sched_entity
*pick_next_entity(struct cfs_rq
*cfs_rq
)
1173 struct sched_entity
*se
= __pick_first_entity(cfs_rq
);
1174 struct sched_entity
*left
= se
;
1177 * Avoid running the skip buddy, if running something else can
1178 * be done without getting too unfair.
1180 if (cfs_rq
->skip
== se
) {
1181 struct sched_entity
*second
= __pick_next_entity(se
);
1182 if (second
&& wakeup_preempt_entity(second
, left
) < 1)
1187 * Prefer last buddy, try to return the CPU to a preempted task.
1189 if (cfs_rq
->last
&& wakeup_preempt_entity(cfs_rq
->last
, left
) < 1)
1193 * Someone really wants this to run. If it's not unfair, run it.
1195 if (cfs_rq
->next
&& wakeup_preempt_entity(cfs_rq
->next
, left
) < 1)
1198 clear_buddies(cfs_rq
, se
);
1203 static void put_prev_entity(struct cfs_rq
*cfs_rq
, struct sched_entity
*prev
)
1206 * If still on the runqueue then deactivate_task()
1207 * was not called and update_curr() has to be done:
1210 update_curr(cfs_rq
);
1212 check_spread(cfs_rq
, prev
);
1214 update_stats_wait_start(cfs_rq
, prev
);
1215 /* Put 'current' back into the tree. */
1216 __enqueue_entity(cfs_rq
, prev
);
1218 cfs_rq
->curr
= NULL
;
1222 entity_tick(struct cfs_rq
*cfs_rq
, struct sched_entity
*curr
, int queued
)
1225 * Update run-time statistics of the 'current'.
1227 update_curr(cfs_rq
);
1230 * Update share accounting for long-running entities.
1232 update_entity_shares_tick(cfs_rq
);
1234 #ifdef CONFIG_SCHED_HRTICK
1236 * queued ticks are scheduled to match the slice, so don't bother
1237 * validating it and just reschedule.
1240 resched_task(rq_of(cfs_rq
)->curr
);
1244 * don't let the period tick interfere with the hrtick preemption
1246 if (!sched_feat(DOUBLE_TICK
) &&
1247 hrtimer_active(&rq_of(cfs_rq
)->hrtick_timer
))
1251 if (cfs_rq
->nr_running
> 1)
1252 check_preempt_tick(cfs_rq
, curr
);
1256 /**************************************************
1257 * CFS bandwidth control machinery
1260 #ifdef CONFIG_CFS_BANDWIDTH
1262 * default period for cfs group bandwidth.
1263 * default: 0.1s, units: nanoseconds
1265 static inline u64
default_cfs_period(void)
1267 return 100000000ULL;
1270 static inline u64
sched_cfs_bandwidth_slice(void)
1272 return (u64
)sysctl_sched_cfs_bandwidth_slice
* NSEC_PER_USEC
;
1276 * Replenish runtime according to assigned quota and update expiration time.
1277 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
1278 * additional synchronization around rq->lock.
1280 * requires cfs_b->lock
1282 static void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth
*cfs_b
)
1286 if (cfs_b
->quota
== RUNTIME_INF
)
1289 now
= sched_clock_cpu(smp_processor_id());
1290 cfs_b
->runtime
= cfs_b
->quota
;
1291 cfs_b
->runtime_expires
= now
+ ktime_to_ns(cfs_b
->period
);
1294 /* returns 0 on failure to allocate runtime */
1295 static int assign_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
1297 struct task_group
*tg
= cfs_rq
->tg
;
1298 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(tg
);
1299 u64 amount
= 0, min_amount
, expires
;
1301 /* note: this is a positive sum as runtime_remaining <= 0 */
1302 min_amount
= sched_cfs_bandwidth_slice() - cfs_rq
->runtime_remaining
;
1304 raw_spin_lock(&cfs_b
->lock
);
1305 if (cfs_b
->quota
== RUNTIME_INF
)
1306 amount
= min_amount
;
1309 * If the bandwidth pool has become inactive, then at least one
1310 * period must have elapsed since the last consumption.
1311 * Refresh the global state and ensure bandwidth timer becomes
1314 if (!cfs_b
->timer_active
) {
1315 __refill_cfs_bandwidth_runtime(cfs_b
);
1316 __start_cfs_bandwidth(cfs_b
);
1319 if (cfs_b
->runtime
> 0) {
1320 amount
= min(cfs_b
->runtime
, min_amount
);
1321 cfs_b
->runtime
-= amount
;
1325 expires
= cfs_b
->runtime_expires
;
1326 raw_spin_unlock(&cfs_b
->lock
);
1328 cfs_rq
->runtime_remaining
+= amount
;
1330 * we may have advanced our local expiration to account for allowed
1331 * spread between our sched_clock and the one on which runtime was
1334 if ((s64
)(expires
- cfs_rq
->runtime_expires
) > 0)
1335 cfs_rq
->runtime_expires
= expires
;
1337 return cfs_rq
->runtime_remaining
> 0;
1341 * Note: This depends on the synchronization provided by sched_clock and the
1342 * fact that rq->clock snapshots this value.
1344 static void expire_cfs_rq_runtime(struct cfs_rq
*cfs_rq
)
1346 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
1347 struct rq
*rq
= rq_of(cfs_rq
);
1349 /* if the deadline is ahead of our clock, nothing to do */
1350 if (likely((s64
)(rq
->clock
- cfs_rq
->runtime_expires
) < 0))
1353 if (cfs_rq
->runtime_remaining
< 0)
1357 * If the local deadline has passed we have to consider the
1358 * possibility that our sched_clock is 'fast' and the global deadline
1359 * has not truly expired.
1361 * Fortunately we can check determine whether this the case by checking
1362 * whether the global deadline has advanced.
1365 if ((s64
)(cfs_rq
->runtime_expires
- cfs_b
->runtime_expires
) >= 0) {
1366 /* extend local deadline, drift is bounded above by 2 ticks */
1367 cfs_rq
->runtime_expires
+= TICK_NSEC
;
1369 /* global deadline is ahead, expiration has passed */
1370 cfs_rq
->runtime_remaining
= 0;
1374 static void __account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
,
1375 unsigned long delta_exec
)
1377 /* dock delta_exec before expiring quota (as it could span periods) */
1378 cfs_rq
->runtime_remaining
-= delta_exec
;
1379 expire_cfs_rq_runtime(cfs_rq
);
1381 if (likely(cfs_rq
->runtime_remaining
> 0))
1385 * if we're unable to extend our runtime we resched so that the active
1386 * hierarchy can be throttled
1388 if (!assign_cfs_rq_runtime(cfs_rq
) && likely(cfs_rq
->curr
))
1389 resched_task(rq_of(cfs_rq
)->curr
);
1392 static __always_inline
void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
,
1393 unsigned long delta_exec
)
1395 if (!cfs_rq
->runtime_enabled
)
1398 __account_cfs_rq_runtime(cfs_rq
, delta_exec
);
1401 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
1403 return cfs_rq
->throttled
;
1406 static __used
void throttle_cfs_rq(struct cfs_rq
*cfs_rq
)
1408 struct rq
*rq
= rq_of(cfs_rq
);
1409 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
1410 struct sched_entity
*se
;
1411 long task_delta
, dequeue
= 1;
1413 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
1415 /* account load preceding throttle */
1416 update_cfs_load(cfs_rq
, 0);
1418 task_delta
= cfs_rq
->h_nr_running
;
1419 for_each_sched_entity(se
) {
1420 struct cfs_rq
*qcfs_rq
= cfs_rq_of(se
);
1421 /* throttled entity or throttle-on-deactivate */
1426 dequeue_entity(qcfs_rq
, se
, DEQUEUE_SLEEP
);
1427 qcfs_rq
->h_nr_running
-= task_delta
;
1429 if (qcfs_rq
->load
.weight
)
1434 rq
->nr_running
-= task_delta
;
1436 cfs_rq
->throttled
= 1;
1437 raw_spin_lock(&cfs_b
->lock
);
1438 list_add_tail_rcu(&cfs_rq
->throttled_list
, &cfs_b
->throttled_cfs_rq
);
1439 raw_spin_unlock(&cfs_b
->lock
);
1442 static void unthrottle_cfs_rq(struct cfs_rq
*cfs_rq
)
1444 struct rq
*rq
= rq_of(cfs_rq
);
1445 struct cfs_bandwidth
*cfs_b
= tg_cfs_bandwidth(cfs_rq
->tg
);
1446 struct sched_entity
*se
;
1450 se
= cfs_rq
->tg
->se
[cpu_of(rq_of(cfs_rq
))];
1452 cfs_rq
->throttled
= 0;
1453 raw_spin_lock(&cfs_b
->lock
);
1454 list_del_rcu(&cfs_rq
->throttled_list
);
1455 raw_spin_unlock(&cfs_b
->lock
);
1457 if (!cfs_rq
->load
.weight
)
1460 task_delta
= cfs_rq
->h_nr_running
;
1461 for_each_sched_entity(se
) {
1465 cfs_rq
= cfs_rq_of(se
);
1467 enqueue_entity(cfs_rq
, se
, ENQUEUE_WAKEUP
);
1468 cfs_rq
->h_nr_running
+= task_delta
;
1470 if (cfs_rq_throttled(cfs_rq
))
1475 rq
->nr_running
+= task_delta
;
1477 /* determine whether we need to wake up potentially idle cpu */
1478 if (rq
->curr
== rq
->idle
&& rq
->cfs
.nr_running
)
1479 resched_task(rq
->curr
);
1482 static u64
distribute_cfs_runtime(struct cfs_bandwidth
*cfs_b
,
1483 u64 remaining
, u64 expires
)
1485 struct cfs_rq
*cfs_rq
;
1486 u64 runtime
= remaining
;
1489 list_for_each_entry_rcu(cfs_rq
, &cfs_b
->throttled_cfs_rq
,
1491 struct rq
*rq
= rq_of(cfs_rq
);
1493 raw_spin_lock(&rq
->lock
);
1494 if (!cfs_rq_throttled(cfs_rq
))
1497 runtime
= -cfs_rq
->runtime_remaining
+ 1;
1498 if (runtime
> remaining
)
1499 runtime
= remaining
;
1500 remaining
-= runtime
;
1502 cfs_rq
->runtime_remaining
+= runtime
;
1503 cfs_rq
->runtime_expires
= expires
;
1505 /* we check whether we're throttled above */
1506 if (cfs_rq
->runtime_remaining
> 0)
1507 unthrottle_cfs_rq(cfs_rq
);
1510 raw_spin_unlock(&rq
->lock
);
1521 * Responsible for refilling a task_group's bandwidth and unthrottling its
1522 * cfs_rqs as appropriate. If there has been no activity within the last
1523 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
1524 * used to track this state.
1526 static int do_sched_cfs_period_timer(struct cfs_bandwidth
*cfs_b
, int overrun
)
1528 u64 runtime
, runtime_expires
;
1529 int idle
= 1, throttled
;
1531 raw_spin_lock(&cfs_b
->lock
);
1532 /* no need to continue the timer with no bandwidth constraint */
1533 if (cfs_b
->quota
== RUNTIME_INF
)
1536 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
1537 /* idle depends on !throttled (for the case of a large deficit) */
1538 idle
= cfs_b
->idle
&& !throttled
;
1540 /* if we're going inactive then everything else can be deferred */
1544 __refill_cfs_bandwidth_runtime(cfs_b
);
1547 /* mark as potentially idle for the upcoming period */
1553 * There are throttled entities so we must first use the new bandwidth
1554 * to unthrottle them before making it generally available. This
1555 * ensures that all existing debts will be paid before a new cfs_rq is
1558 runtime
= cfs_b
->runtime
;
1559 runtime_expires
= cfs_b
->runtime_expires
;
1563 * This check is repeated as we are holding onto the new bandwidth
1564 * while we unthrottle. This can potentially race with an unthrottled
1565 * group trying to acquire new bandwidth from the global pool.
1567 while (throttled
&& runtime
> 0) {
1568 raw_spin_unlock(&cfs_b
->lock
);
1569 /* we can't nest cfs_b->lock while distributing bandwidth */
1570 runtime
= distribute_cfs_runtime(cfs_b
, runtime
,
1572 raw_spin_lock(&cfs_b
->lock
);
1574 throttled
= !list_empty(&cfs_b
->throttled_cfs_rq
);
1577 /* return (any) remaining runtime */
1578 cfs_b
->runtime
= runtime
;
1580 * While we are ensured activity in the period following an
1581 * unthrottle, this also covers the case in which the new bandwidth is
1582 * insufficient to cover the existing bandwidth deficit. (Forcing the
1583 * timer to remain active while there are any throttled entities.)
1588 cfs_b
->timer_active
= 0;
1589 raw_spin_unlock(&cfs_b
->lock
);
1594 static void account_cfs_rq_runtime(struct cfs_rq
*cfs_rq
,
1595 unsigned long delta_exec
) {}
1597 static inline int cfs_rq_throttled(struct cfs_rq
*cfs_rq
)
1603 /**************************************************
1604 * CFS operations on tasks:
1607 #ifdef CONFIG_SCHED_HRTICK
1608 static void hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
1610 struct sched_entity
*se
= &p
->se
;
1611 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
1613 WARN_ON(task_rq(p
) != rq
);
1615 if (hrtick_enabled(rq
) && cfs_rq
->nr_running
> 1) {
1616 u64 slice
= sched_slice(cfs_rq
, se
);
1617 u64 ran
= se
->sum_exec_runtime
- se
->prev_sum_exec_runtime
;
1618 s64 delta
= slice
- ran
;
1627 * Don't schedule slices shorter than 10000ns, that just
1628 * doesn't make sense. Rely on vruntime for fairness.
1631 delta
= max_t(s64
, 10000LL, delta
);
1633 hrtick_start(rq
, delta
);
1638 * called from enqueue/dequeue and updates the hrtick when the
1639 * current task is from our class and nr_running is low enough
1642 static void hrtick_update(struct rq
*rq
)
1644 struct task_struct
*curr
= rq
->curr
;
1646 if (curr
->sched_class
!= &fair_sched_class
)
1649 if (cfs_rq_of(&curr
->se
)->nr_running
< sched_nr_latency
)
1650 hrtick_start_fair(rq
, curr
);
1652 #else /* !CONFIG_SCHED_HRTICK */
1654 hrtick_start_fair(struct rq
*rq
, struct task_struct
*p
)
1658 static inline void hrtick_update(struct rq
*rq
)
1664 * The enqueue_task method is called before nr_running is
1665 * increased. Here we update the fair scheduling stats and
1666 * then put the task into the rbtree:
1669 enqueue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
1671 struct cfs_rq
*cfs_rq
;
1672 struct sched_entity
*se
= &p
->se
;
1674 for_each_sched_entity(se
) {
1677 cfs_rq
= cfs_rq_of(se
);
1678 enqueue_entity(cfs_rq
, se
, flags
);
1681 * end evaluation on encountering a throttled cfs_rq
1683 * note: in the case of encountering a throttled cfs_rq we will
1684 * post the final h_nr_running increment below.
1686 if (cfs_rq_throttled(cfs_rq
))
1688 cfs_rq
->h_nr_running
++;
1690 flags
= ENQUEUE_WAKEUP
;
1693 for_each_sched_entity(se
) {
1694 cfs_rq
= cfs_rq_of(se
);
1695 cfs_rq
->h_nr_running
++;
1697 if (cfs_rq_throttled(cfs_rq
))
1700 update_cfs_load(cfs_rq
, 0);
1701 update_cfs_shares(cfs_rq
);
1709 static void set_next_buddy(struct sched_entity
*se
);
1712 * The dequeue_task method is called before nr_running is
1713 * decreased. We remove the task from the rbtree and
1714 * update the fair scheduling stats:
1716 static void dequeue_task_fair(struct rq
*rq
, struct task_struct
*p
, int flags
)
1718 struct cfs_rq
*cfs_rq
;
1719 struct sched_entity
*se
= &p
->se
;
1720 int task_sleep
= flags
& DEQUEUE_SLEEP
;
1722 for_each_sched_entity(se
) {
1723 cfs_rq
= cfs_rq_of(se
);
1724 dequeue_entity(cfs_rq
, se
, flags
);
1727 * end evaluation on encountering a throttled cfs_rq
1729 * note: in the case of encountering a throttled cfs_rq we will
1730 * post the final h_nr_running decrement below.
1732 if (cfs_rq_throttled(cfs_rq
))
1734 cfs_rq
->h_nr_running
--;
1736 /* Don't dequeue parent if it has other entities besides us */
1737 if (cfs_rq
->load
.weight
) {
1739 * Bias pick_next to pick a task from this cfs_rq, as
1740 * p is sleeping when it is within its sched_slice.
1742 if (task_sleep
&& parent_entity(se
))
1743 set_next_buddy(parent_entity(se
));
1745 /* avoid re-evaluating load for this entity */
1746 se
= parent_entity(se
);
1749 flags
|= DEQUEUE_SLEEP
;
1752 for_each_sched_entity(se
) {
1753 cfs_rq
= cfs_rq_of(se
);
1754 cfs_rq
->h_nr_running
--;
1756 if (cfs_rq_throttled(cfs_rq
))
1759 update_cfs_load(cfs_rq
, 0);
1760 update_cfs_shares(cfs_rq
);
1770 static void task_waking_fair(struct task_struct
*p
)
1772 struct sched_entity
*se
= &p
->se
;
1773 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
1776 #ifndef CONFIG_64BIT
1777 u64 min_vruntime_copy
;
1780 min_vruntime_copy
= cfs_rq
->min_vruntime_copy
;
1782 min_vruntime
= cfs_rq
->min_vruntime
;
1783 } while (min_vruntime
!= min_vruntime_copy
);
1785 min_vruntime
= cfs_rq
->min_vruntime
;
1788 se
->vruntime
-= min_vruntime
;
1791 #ifdef CONFIG_FAIR_GROUP_SCHED
1793 * effective_load() calculates the load change as seen from the root_task_group
1795 * Adding load to a group doesn't make a group heavier, but can cause movement
1796 * of group shares between cpus. Assuming the shares were perfectly aligned one
1797 * can calculate the shift in shares.
1799 static long effective_load(struct task_group
*tg
, int cpu
, long wl
, long wg
)
1801 struct sched_entity
*se
= tg
->se
[cpu
];
1806 for_each_sched_entity(se
) {
1810 w
= se
->my_q
->load
.weight
;
1812 /* use this cpu's instantaneous contribution */
1813 lw
= atomic_read(&tg
->load_weight
);
1814 lw
-= se
->my_q
->load_contribution
;
1819 if (lw
> 0 && wl
< lw
)
1820 wl
= (wl
* tg
->shares
) / lw
;
1824 /* zero point is MIN_SHARES */
1825 if (wl
< MIN_SHARES
)
1827 wl
-= se
->load
.weight
;
1835 static inline unsigned long effective_load(struct task_group
*tg
, int cpu
,
1836 unsigned long wl
, unsigned long wg
)
1843 static int wake_affine(struct sched_domain
*sd
, struct task_struct
*p
, int sync
)
1845 s64 this_load
, load
;
1846 int idx
, this_cpu
, prev_cpu
;
1847 unsigned long tl_per_task
;
1848 struct task_group
*tg
;
1849 unsigned long weight
;
1853 this_cpu
= smp_processor_id();
1854 prev_cpu
= task_cpu(p
);
1855 load
= source_load(prev_cpu
, idx
);
1856 this_load
= target_load(this_cpu
, idx
);
1859 * If sync wakeup then subtract the (maximum possible)
1860 * effect of the currently running task from the load
1861 * of the current CPU:
1864 tg
= task_group(current
);
1865 weight
= current
->se
.load
.weight
;
1867 this_load
+= effective_load(tg
, this_cpu
, -weight
, -weight
);
1868 load
+= effective_load(tg
, prev_cpu
, 0, -weight
);
1872 weight
= p
->se
.load
.weight
;
1875 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1876 * due to the sync cause above having dropped this_load to 0, we'll
1877 * always have an imbalance, but there's really nothing you can do
1878 * about that, so that's good too.
1880 * Otherwise check if either cpus are near enough in load to allow this
1881 * task to be woken on this_cpu.
1883 if (this_load
> 0) {
1884 s64 this_eff_load
, prev_eff_load
;
1886 this_eff_load
= 100;
1887 this_eff_load
*= power_of(prev_cpu
);
1888 this_eff_load
*= this_load
+
1889 effective_load(tg
, this_cpu
, weight
, weight
);
1891 prev_eff_load
= 100 + (sd
->imbalance_pct
- 100) / 2;
1892 prev_eff_load
*= power_of(this_cpu
);
1893 prev_eff_load
*= load
+ effective_load(tg
, prev_cpu
, 0, weight
);
1895 balanced
= this_eff_load
<= prev_eff_load
;
1900 * If the currently running task will sleep within
1901 * a reasonable amount of time then attract this newly
1904 if (sync
&& balanced
)
1907 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine_attempts
);
1908 tl_per_task
= cpu_avg_load_per_task(this_cpu
);
1911 (this_load
<= load
&&
1912 this_load
+ target_load(prev_cpu
, idx
) <= tl_per_task
)) {
1914 * This domain has SD_WAKE_AFFINE and
1915 * p is cache cold in this domain, and
1916 * there is no bad imbalance.
1918 schedstat_inc(sd
, ttwu_move_affine
);
1919 schedstat_inc(p
, se
.statistics
.nr_wakeups_affine
);
1927 * find_idlest_group finds and returns the least busy CPU group within the
1930 static struct sched_group
*
1931 find_idlest_group(struct sched_domain
*sd
, struct task_struct
*p
,
1932 int this_cpu
, int load_idx
)
1934 struct sched_group
*idlest
= NULL
, *group
= sd
->groups
;
1935 unsigned long min_load
= ULONG_MAX
, this_load
= 0;
1936 int imbalance
= 100 + (sd
->imbalance_pct
-100)/2;
1939 unsigned long load
, avg_load
;
1943 /* Skip over this group if it has no CPUs allowed */
1944 if (!cpumask_intersects(sched_group_cpus(group
),
1948 local_group
= cpumask_test_cpu(this_cpu
,
1949 sched_group_cpus(group
));
1951 /* Tally up the load of all CPUs in the group */
1954 for_each_cpu(i
, sched_group_cpus(group
)) {
1955 /* Bias balancing toward cpus of our domain */
1957 load
= source_load(i
, load_idx
);
1959 load
= target_load(i
, load_idx
);
1964 /* Adjust by relative CPU power of the group */
1965 avg_load
= (avg_load
* SCHED_POWER_SCALE
) / group
->sgp
->power
;
1968 this_load
= avg_load
;
1969 } else if (avg_load
< min_load
) {
1970 min_load
= avg_load
;
1973 } while (group
= group
->next
, group
!= sd
->groups
);
1975 if (!idlest
|| 100*this_load
< imbalance
*min_load
)
1981 * find_idlest_cpu - find the idlest cpu among the cpus in group.
1984 find_idlest_cpu(struct sched_group
*group
, struct task_struct
*p
, int this_cpu
)
1986 unsigned long load
, min_load
= ULONG_MAX
;
1990 /* Traverse only the allowed CPUs */
1991 for_each_cpu_and(i
, sched_group_cpus(group
), &p
->cpus_allowed
) {
1992 load
= weighted_cpuload(i
);
1994 if (load
< min_load
|| (load
== min_load
&& i
== this_cpu
)) {
2004 * Try and locate an idle CPU in the sched_domain.
2006 static int select_idle_sibling(struct task_struct
*p
, int target
)
2008 int cpu
= smp_processor_id();
2009 int prev_cpu
= task_cpu(p
);
2010 struct sched_domain
*sd
;
2014 * If the task is going to be woken-up on this cpu and if it is
2015 * already idle, then it is the right target.
2017 if (target
== cpu
&& idle_cpu(cpu
))
2021 * If the task is going to be woken-up on the cpu where it previously
2022 * ran and if it is currently idle, then it the right target.
2024 if (target
== prev_cpu
&& idle_cpu(prev_cpu
))
2028 * Otherwise, iterate the domains and find an elegible idle cpu.
2031 for_each_domain(target
, sd
) {
2032 if (!(sd
->flags
& SD_SHARE_PKG_RESOURCES
))
2035 for_each_cpu_and(i
, sched_domain_span(sd
), &p
->cpus_allowed
) {
2043 * Lets stop looking for an idle sibling when we reached
2044 * the domain that spans the current cpu and prev_cpu.
2046 if (cpumask_test_cpu(cpu
, sched_domain_span(sd
)) &&
2047 cpumask_test_cpu(prev_cpu
, sched_domain_span(sd
)))
2056 * sched_balance_self: balance the current task (running on cpu) in domains
2057 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
2060 * Balance, ie. select the least loaded group.
2062 * Returns the target CPU number, or the same CPU if no balancing is needed.
2064 * preempt must be disabled.
2067 select_task_rq_fair(struct task_struct
*p
, int sd_flag
, int wake_flags
)
2069 struct sched_domain
*tmp
, *affine_sd
= NULL
, *sd
= NULL
;
2070 int cpu
= smp_processor_id();
2071 int prev_cpu
= task_cpu(p
);
2073 int want_affine
= 0;
2075 int sync
= wake_flags
& WF_SYNC
;
2077 if (sd_flag
& SD_BALANCE_WAKE
) {
2078 if (cpumask_test_cpu(cpu
, &p
->cpus_allowed
))
2084 for_each_domain(cpu
, tmp
) {
2085 if (!(tmp
->flags
& SD_LOAD_BALANCE
))
2089 * If power savings logic is enabled for a domain, see if we
2090 * are not overloaded, if so, don't balance wider.
2092 if (tmp
->flags
& (SD_POWERSAVINGS_BALANCE
|SD_PREFER_LOCAL
)) {
2093 unsigned long power
= 0;
2094 unsigned long nr_running
= 0;
2095 unsigned long capacity
;
2098 for_each_cpu(i
, sched_domain_span(tmp
)) {
2099 power
+= power_of(i
);
2100 nr_running
+= cpu_rq(i
)->cfs
.nr_running
;
2103 capacity
= DIV_ROUND_CLOSEST(power
, SCHED_POWER_SCALE
);
2105 if (tmp
->flags
& SD_POWERSAVINGS_BALANCE
)
2108 if (nr_running
< capacity
)
2113 * If both cpu and prev_cpu are part of this domain,
2114 * cpu is a valid SD_WAKE_AFFINE target.
2116 if (want_affine
&& (tmp
->flags
& SD_WAKE_AFFINE
) &&
2117 cpumask_test_cpu(prev_cpu
, sched_domain_span(tmp
))) {
2122 if (!want_sd
&& !want_affine
)
2125 if (!(tmp
->flags
& sd_flag
))
2133 if (cpu
== prev_cpu
|| wake_affine(affine_sd
, p
, sync
))
2136 new_cpu
= select_idle_sibling(p
, prev_cpu
);
2141 int load_idx
= sd
->forkexec_idx
;
2142 struct sched_group
*group
;
2145 if (!(sd
->flags
& sd_flag
)) {
2150 if (sd_flag
& SD_BALANCE_WAKE
)
2151 load_idx
= sd
->wake_idx
;
2153 group
= find_idlest_group(sd
, p
, cpu
, load_idx
);
2159 new_cpu
= find_idlest_cpu(group
, p
, cpu
);
2160 if (new_cpu
== -1 || new_cpu
== cpu
) {
2161 /* Now try balancing at a lower domain level of cpu */
2166 /* Now try balancing at a lower domain level of new_cpu */
2168 weight
= sd
->span_weight
;
2170 for_each_domain(cpu
, tmp
) {
2171 if (weight
<= tmp
->span_weight
)
2173 if (tmp
->flags
& sd_flag
)
2176 /* while loop will break here if sd == NULL */
2183 #endif /* CONFIG_SMP */
2185 static unsigned long
2186 wakeup_gran(struct sched_entity
*curr
, struct sched_entity
*se
)
2188 unsigned long gran
= sysctl_sched_wakeup_granularity
;
2191 * Since its curr running now, convert the gran from real-time
2192 * to virtual-time in his units.
2194 * By using 'se' instead of 'curr' we penalize light tasks, so
2195 * they get preempted easier. That is, if 'se' < 'curr' then
2196 * the resulting gran will be larger, therefore penalizing the
2197 * lighter, if otoh 'se' > 'curr' then the resulting gran will
2198 * be smaller, again penalizing the lighter task.
2200 * This is especially important for buddies when the leftmost
2201 * task is higher priority than the buddy.
2203 return calc_delta_fair(gran
, se
);
2207 * Should 'se' preempt 'curr'.
2221 wakeup_preempt_entity(struct sched_entity
*curr
, struct sched_entity
*se
)
2223 s64 gran
, vdiff
= curr
->vruntime
- se
->vruntime
;
2228 gran
= wakeup_gran(curr
, se
);
2235 static void set_last_buddy(struct sched_entity
*se
)
2237 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
2240 for_each_sched_entity(se
)
2241 cfs_rq_of(se
)->last
= se
;
2244 static void set_next_buddy(struct sched_entity
*se
)
2246 if (entity_is_task(se
) && unlikely(task_of(se
)->policy
== SCHED_IDLE
))
2249 for_each_sched_entity(se
)
2250 cfs_rq_of(se
)->next
= se
;
2253 static void set_skip_buddy(struct sched_entity
*se
)
2255 for_each_sched_entity(se
)
2256 cfs_rq_of(se
)->skip
= se
;
2260 * Preempt the current task with a newly woken task if needed:
2262 static void check_preempt_wakeup(struct rq
*rq
, struct task_struct
*p
, int wake_flags
)
2264 struct task_struct
*curr
= rq
->curr
;
2265 struct sched_entity
*se
= &curr
->se
, *pse
= &p
->se
;
2266 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
2267 int scale
= cfs_rq
->nr_running
>= sched_nr_latency
;
2268 int next_buddy_marked
= 0;
2270 if (unlikely(se
== pse
))
2273 if (sched_feat(NEXT_BUDDY
) && scale
&& !(wake_flags
& WF_FORK
)) {
2274 set_next_buddy(pse
);
2275 next_buddy_marked
= 1;
2279 * We can come here with TIF_NEED_RESCHED already set from new task
2282 if (test_tsk_need_resched(curr
))
2285 /* Idle tasks are by definition preempted by non-idle tasks. */
2286 if (unlikely(curr
->policy
== SCHED_IDLE
) &&
2287 likely(p
->policy
!= SCHED_IDLE
))
2291 * Batch and idle tasks do not preempt non-idle tasks (their preemption
2292 * is driven by the tick):
2294 if (unlikely(p
->policy
!= SCHED_NORMAL
))
2297 find_matching_se(&se
, &pse
);
2298 update_curr(cfs_rq_of(se
));
2300 if (wakeup_preempt_entity(se
, pse
) == 1) {
2302 * Bias pick_next to pick the sched entity that is
2303 * triggering this preemption.
2305 if (!next_buddy_marked
)
2306 set_next_buddy(pse
);
2315 * Only set the backward buddy when the current task is still
2316 * on the rq. This can happen when a wakeup gets interleaved
2317 * with schedule on the ->pre_schedule() or idle_balance()
2318 * point, either of which can * drop the rq lock.
2320 * Also, during early boot the idle thread is in the fair class,
2321 * for obvious reasons its a bad idea to schedule back to it.
2323 if (unlikely(!se
->on_rq
|| curr
== rq
->idle
))
2326 if (sched_feat(LAST_BUDDY
) && scale
&& entity_is_task(se
))
2330 static struct task_struct
*pick_next_task_fair(struct rq
*rq
)
2332 struct task_struct
*p
;
2333 struct cfs_rq
*cfs_rq
= &rq
->cfs
;
2334 struct sched_entity
*se
;
2336 if (!cfs_rq
->nr_running
)
2340 se
= pick_next_entity(cfs_rq
);
2341 set_next_entity(cfs_rq
, se
);
2342 cfs_rq
= group_cfs_rq(se
);
2346 hrtick_start_fair(rq
, p
);
2352 * Account for a descheduled task:
2354 static void put_prev_task_fair(struct rq
*rq
, struct task_struct
*prev
)
2356 struct sched_entity
*se
= &prev
->se
;
2357 struct cfs_rq
*cfs_rq
;
2359 for_each_sched_entity(se
) {
2360 cfs_rq
= cfs_rq_of(se
);
2361 put_prev_entity(cfs_rq
, se
);
2366 * sched_yield() is very simple
2368 * The magic of dealing with the ->skip buddy is in pick_next_entity.
2370 static void yield_task_fair(struct rq
*rq
)
2372 struct task_struct
*curr
= rq
->curr
;
2373 struct cfs_rq
*cfs_rq
= task_cfs_rq(curr
);
2374 struct sched_entity
*se
= &curr
->se
;
2377 * Are we the only task in the tree?
2379 if (unlikely(rq
->nr_running
== 1))
2382 clear_buddies(cfs_rq
, se
);
2384 if (curr
->policy
!= SCHED_BATCH
) {
2385 update_rq_clock(rq
);
2387 * Update run-time statistics of the 'current'.
2389 update_curr(cfs_rq
);
2395 static bool yield_to_task_fair(struct rq
*rq
, struct task_struct
*p
, bool preempt
)
2397 struct sched_entity
*se
= &p
->se
;
2402 /* Tell the scheduler that we'd really like pse to run next. */
2405 yield_task_fair(rq
);
2411 /**************************************************
2412 * Fair scheduling class load-balancing methods:
2416 * pull_task - move a task from a remote runqueue to the local runqueue.
2417 * Both runqueues must be locked.
2419 static void pull_task(struct rq
*src_rq
, struct task_struct
*p
,
2420 struct rq
*this_rq
, int this_cpu
)
2422 deactivate_task(src_rq
, p
, 0);
2423 set_task_cpu(p
, this_cpu
);
2424 activate_task(this_rq
, p
, 0);
2425 check_preempt_curr(this_rq
, p
, 0);
2429 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
2432 int can_migrate_task(struct task_struct
*p
, struct rq
*rq
, int this_cpu
,
2433 struct sched_domain
*sd
, enum cpu_idle_type idle
,
2436 int tsk_cache_hot
= 0;
2438 * We do not migrate tasks that are:
2439 * 1) running (obviously), or
2440 * 2) cannot be migrated to this CPU due to cpus_allowed, or
2441 * 3) are cache-hot on their current CPU.
2443 if (!cpumask_test_cpu(this_cpu
, &p
->cpus_allowed
)) {
2444 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_affine
);
2449 if (task_running(rq
, p
)) {
2450 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_running
);
2455 * Aggressive migration if:
2456 * 1) task is cache cold, or
2457 * 2) too many balance attempts have failed.
2460 tsk_cache_hot
= task_hot(p
, rq
->clock_task
, sd
);
2461 if (!tsk_cache_hot
||
2462 sd
->nr_balance_failed
> sd
->cache_nice_tries
) {
2463 #ifdef CONFIG_SCHEDSTATS
2464 if (tsk_cache_hot
) {
2465 schedstat_inc(sd
, lb_hot_gained
[idle
]);
2466 schedstat_inc(p
, se
.statistics
.nr_forced_migrations
);
2472 if (tsk_cache_hot
) {
2473 schedstat_inc(p
, se
.statistics
.nr_failed_migrations_hot
);
2480 * move_one_task tries to move exactly one task from busiest to this_rq, as
2481 * part of active balancing operations within "domain".
2482 * Returns 1 if successful and 0 otherwise.
2484 * Called with both runqueues locked.
2487 move_one_task(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
2488 struct sched_domain
*sd
, enum cpu_idle_type idle
)
2490 struct task_struct
*p
, *n
;
2491 struct cfs_rq
*cfs_rq
;
2494 for_each_leaf_cfs_rq(busiest
, cfs_rq
) {
2495 list_for_each_entry_safe(p
, n
, &cfs_rq
->tasks
, se
.group_node
) {
2497 if (!can_migrate_task(p
, busiest
, this_cpu
,
2501 pull_task(busiest
, p
, this_rq
, this_cpu
);
2503 * Right now, this is only the second place pull_task()
2504 * is called, so we can safely collect pull_task()
2505 * stats here rather than inside pull_task().
2507 schedstat_inc(sd
, lb_gained
[idle
]);
2515 static unsigned long
2516 balance_tasks(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
2517 unsigned long max_load_move
, struct sched_domain
*sd
,
2518 enum cpu_idle_type idle
, int *all_pinned
,
2519 struct cfs_rq
*busiest_cfs_rq
)
2521 int loops
= 0, pulled
= 0;
2522 long rem_load_move
= max_load_move
;
2523 struct task_struct
*p
, *n
;
2525 if (max_load_move
== 0)
2528 list_for_each_entry_safe(p
, n
, &busiest_cfs_rq
->tasks
, se
.group_node
) {
2529 if (loops
++ > sysctl_sched_nr_migrate
)
2532 if ((p
->se
.load
.weight
>> 1) > rem_load_move
||
2533 !can_migrate_task(p
, busiest
, this_cpu
, sd
, idle
,
2537 pull_task(busiest
, p
, this_rq
, this_cpu
);
2539 rem_load_move
-= p
->se
.load
.weight
;
2541 #ifdef CONFIG_PREEMPT
2543 * NEWIDLE balancing is a source of latency, so preemptible
2544 * kernels will stop after the first task is pulled to minimize
2545 * the critical section.
2547 if (idle
== CPU_NEWLY_IDLE
)
2552 * We only want to steal up to the prescribed amount of
2555 if (rem_load_move
<= 0)
2560 * Right now, this is one of only two places pull_task() is called,
2561 * so we can safely collect pull_task() stats here rather than
2562 * inside pull_task().
2564 schedstat_add(sd
, lb_gained
[idle
], pulled
);
2566 return max_load_move
- rem_load_move
;
2569 #ifdef CONFIG_FAIR_GROUP_SCHED
2571 * update tg->load_weight by folding this cpu's load_avg
2573 static int update_shares_cpu(struct task_group
*tg
, int cpu
)
2575 struct cfs_rq
*cfs_rq
;
2576 unsigned long flags
;
2583 cfs_rq
= tg
->cfs_rq
[cpu
];
2585 raw_spin_lock_irqsave(&rq
->lock
, flags
);
2587 update_rq_clock(rq
);
2588 update_cfs_load(cfs_rq
, 1);
2591 * We need to update shares after updating tg->load_weight in
2592 * order to adjust the weight of groups with long running tasks.
2594 update_cfs_shares(cfs_rq
);
2596 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
2601 static void update_shares(int cpu
)
2603 struct cfs_rq
*cfs_rq
;
2604 struct rq
*rq
= cpu_rq(cpu
);
2608 * Iterates the task_group tree in a bottom up fashion, see
2609 * list_add_leaf_cfs_rq() for details.
2611 for_each_leaf_cfs_rq(rq
, cfs_rq
)
2612 update_shares_cpu(cfs_rq
->tg
, cpu
);
2617 * Compute the cpu's hierarchical load factor for each task group.
2618 * This needs to be done in a top-down fashion because the load of a child
2619 * group is a fraction of its parents load.
2621 static int tg_load_down(struct task_group
*tg
, void *data
)
2624 long cpu
= (long)data
;
2627 load
= cpu_rq(cpu
)->load
.weight
;
2629 load
= tg
->parent
->cfs_rq
[cpu
]->h_load
;
2630 load
*= tg
->se
[cpu
]->load
.weight
;
2631 load
/= tg
->parent
->cfs_rq
[cpu
]->load
.weight
+ 1;
2634 tg
->cfs_rq
[cpu
]->h_load
= load
;
2639 static void update_h_load(long cpu
)
2641 walk_tg_tree(tg_load_down
, tg_nop
, (void *)cpu
);
2644 static unsigned long
2645 load_balance_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
2646 unsigned long max_load_move
,
2647 struct sched_domain
*sd
, enum cpu_idle_type idle
,
2650 long rem_load_move
= max_load_move
;
2651 struct cfs_rq
*busiest_cfs_rq
;
2654 update_h_load(cpu_of(busiest
));
2656 for_each_leaf_cfs_rq(busiest
, busiest_cfs_rq
) {
2657 unsigned long busiest_h_load
= busiest_cfs_rq
->h_load
;
2658 unsigned long busiest_weight
= busiest_cfs_rq
->load
.weight
;
2659 u64 rem_load
, moved_load
;
2664 if (!busiest_cfs_rq
->task_weight
)
2667 rem_load
= (u64
)rem_load_move
* busiest_weight
;
2668 rem_load
= div_u64(rem_load
, busiest_h_load
+ 1);
2670 moved_load
= balance_tasks(this_rq
, this_cpu
, busiest
,
2671 rem_load
, sd
, idle
, all_pinned
,
2677 moved_load
*= busiest_h_load
;
2678 moved_load
= div_u64(moved_load
, busiest_weight
+ 1);
2680 rem_load_move
-= moved_load
;
2681 if (rem_load_move
< 0)
2686 return max_load_move
- rem_load_move
;
2689 static inline void update_shares(int cpu
)
2693 static unsigned long
2694 load_balance_fair(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
2695 unsigned long max_load_move
,
2696 struct sched_domain
*sd
, enum cpu_idle_type idle
,
2699 return balance_tasks(this_rq
, this_cpu
, busiest
,
2700 max_load_move
, sd
, idle
, all_pinned
,
2706 * move_tasks tries to move up to max_load_move weighted load from busiest to
2707 * this_rq, as part of a balancing operation within domain "sd".
2708 * Returns 1 if successful and 0 otherwise.
2710 * Called with both runqueues locked.
2712 static int move_tasks(struct rq
*this_rq
, int this_cpu
, struct rq
*busiest
,
2713 unsigned long max_load_move
,
2714 struct sched_domain
*sd
, enum cpu_idle_type idle
,
2717 unsigned long total_load_moved
= 0, load_moved
;
2720 load_moved
= load_balance_fair(this_rq
, this_cpu
, busiest
,
2721 max_load_move
- total_load_moved
,
2722 sd
, idle
, all_pinned
);
2724 total_load_moved
+= load_moved
;
2726 #ifdef CONFIG_PREEMPT
2728 * NEWIDLE balancing is a source of latency, so preemptible
2729 * kernels will stop after the first task is pulled to minimize
2730 * the critical section.
2732 if (idle
== CPU_NEWLY_IDLE
&& this_rq
->nr_running
)
2735 if (raw_spin_is_contended(&this_rq
->lock
) ||
2736 raw_spin_is_contended(&busiest
->lock
))
2739 } while (load_moved
&& max_load_move
> total_load_moved
);
2741 return total_load_moved
> 0;
2744 /********** Helpers for find_busiest_group ************************/
2746 * sd_lb_stats - Structure to store the statistics of a sched_domain
2747 * during load balancing.
2749 struct sd_lb_stats
{
2750 struct sched_group
*busiest
; /* Busiest group in this sd */
2751 struct sched_group
*this; /* Local group in this sd */
2752 unsigned long total_load
; /* Total load of all groups in sd */
2753 unsigned long total_pwr
; /* Total power of all groups in sd */
2754 unsigned long avg_load
; /* Average load across all groups in sd */
2756 /** Statistics of this group */
2757 unsigned long this_load
;
2758 unsigned long this_load_per_task
;
2759 unsigned long this_nr_running
;
2760 unsigned long this_has_capacity
;
2761 unsigned int this_idle_cpus
;
2763 /* Statistics of the busiest group */
2764 unsigned int busiest_idle_cpus
;
2765 unsigned long max_load
;
2766 unsigned long busiest_load_per_task
;
2767 unsigned long busiest_nr_running
;
2768 unsigned long busiest_group_capacity
;
2769 unsigned long busiest_has_capacity
;
2770 unsigned int busiest_group_weight
;
2772 int group_imb
; /* Is there imbalance in this sd */
2773 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
2774 int power_savings_balance
; /* Is powersave balance needed for this sd */
2775 struct sched_group
*group_min
; /* Least loaded group in sd */
2776 struct sched_group
*group_leader
; /* Group which relieves group_min */
2777 unsigned long min_load_per_task
; /* load_per_task in group_min */
2778 unsigned long leader_nr_running
; /* Nr running of group_leader */
2779 unsigned long min_nr_running
; /* Nr running of group_min */
2784 * sg_lb_stats - stats of a sched_group required for load_balancing
2786 struct sg_lb_stats
{
2787 unsigned long avg_load
; /*Avg load across the CPUs of the group */
2788 unsigned long group_load
; /* Total load over the CPUs of the group */
2789 unsigned long sum_nr_running
; /* Nr tasks running in the group */
2790 unsigned long sum_weighted_load
; /* Weighted load of group's tasks */
2791 unsigned long group_capacity
;
2792 unsigned long idle_cpus
;
2793 unsigned long group_weight
;
2794 int group_imb
; /* Is there an imbalance in the group ? */
2795 int group_has_capacity
; /* Is there extra capacity in the group? */
2799 * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
2800 * @group: The group whose first cpu is to be returned.
2802 static inline unsigned int group_first_cpu(struct sched_group
*group
)
2804 return cpumask_first(sched_group_cpus(group
));
2808 * get_sd_load_idx - Obtain the load index for a given sched domain.
2809 * @sd: The sched_domain whose load_idx is to be obtained.
2810 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
2812 static inline int get_sd_load_idx(struct sched_domain
*sd
,
2813 enum cpu_idle_type idle
)
2819 load_idx
= sd
->busy_idx
;
2822 case CPU_NEWLY_IDLE
:
2823 load_idx
= sd
->newidle_idx
;
2826 load_idx
= sd
->idle_idx
;
2834 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
2836 * init_sd_power_savings_stats - Initialize power savings statistics for
2837 * the given sched_domain, during load balancing.
2839 * @sd: Sched domain whose power-savings statistics are to be initialized.
2840 * @sds: Variable containing the statistics for sd.
2841 * @idle: Idle status of the CPU at which we're performing load-balancing.
2843 static inline void init_sd_power_savings_stats(struct sched_domain
*sd
,
2844 struct sd_lb_stats
*sds
, enum cpu_idle_type idle
)
2847 * Busy processors will not participate in power savings
2850 if (idle
== CPU_NOT_IDLE
|| !(sd
->flags
& SD_POWERSAVINGS_BALANCE
))
2851 sds
->power_savings_balance
= 0;
2853 sds
->power_savings_balance
= 1;
2854 sds
->min_nr_running
= ULONG_MAX
;
2855 sds
->leader_nr_running
= 0;
2860 * update_sd_power_savings_stats - Update the power saving stats for a
2861 * sched_domain while performing load balancing.
2863 * @group: sched_group belonging to the sched_domain under consideration.
2864 * @sds: Variable containing the statistics of the sched_domain
2865 * @local_group: Does group contain the CPU for which we're performing
2867 * @sgs: Variable containing the statistics of the group.
2869 static inline void update_sd_power_savings_stats(struct sched_group
*group
,
2870 struct sd_lb_stats
*sds
, int local_group
, struct sg_lb_stats
*sgs
)
2873 if (!sds
->power_savings_balance
)
2877 * If the local group is idle or completely loaded
2878 * no need to do power savings balance at this domain
2880 if (local_group
&& (sds
->this_nr_running
>= sgs
->group_capacity
||
2881 !sds
->this_nr_running
))
2882 sds
->power_savings_balance
= 0;
2885 * If a group is already running at full capacity or idle,
2886 * don't include that group in power savings calculations
2888 if (!sds
->power_savings_balance
||
2889 sgs
->sum_nr_running
>= sgs
->group_capacity
||
2890 !sgs
->sum_nr_running
)
2894 * Calculate the group which has the least non-idle load.
2895 * This is the group from where we need to pick up the load
2898 if ((sgs
->sum_nr_running
< sds
->min_nr_running
) ||
2899 (sgs
->sum_nr_running
== sds
->min_nr_running
&&
2900 group_first_cpu(group
) > group_first_cpu(sds
->group_min
))) {
2901 sds
->group_min
= group
;
2902 sds
->min_nr_running
= sgs
->sum_nr_running
;
2903 sds
->min_load_per_task
= sgs
->sum_weighted_load
/
2904 sgs
->sum_nr_running
;
2908 * Calculate the group which is almost near its
2909 * capacity but still has some space to pick up some load
2910 * from other group and save more power
2912 if (sgs
->sum_nr_running
+ 1 > sgs
->group_capacity
)
2915 if (sgs
->sum_nr_running
> sds
->leader_nr_running
||
2916 (sgs
->sum_nr_running
== sds
->leader_nr_running
&&
2917 group_first_cpu(group
) < group_first_cpu(sds
->group_leader
))) {
2918 sds
->group_leader
= group
;
2919 sds
->leader_nr_running
= sgs
->sum_nr_running
;
2924 * check_power_save_busiest_group - see if there is potential for some power-savings balance
2925 * @sds: Variable containing the statistics of the sched_domain
2926 * under consideration.
2927 * @this_cpu: Cpu at which we're currently performing load-balancing.
2928 * @imbalance: Variable to store the imbalance.
2931 * Check if we have potential to perform some power-savings balance.
2932 * If yes, set the busiest group to be the least loaded group in the
2933 * sched_domain, so that it's CPUs can be put to idle.
2935 * Returns 1 if there is potential to perform power-savings balance.
2938 static inline int check_power_save_busiest_group(struct sd_lb_stats
*sds
,
2939 int this_cpu
, unsigned long *imbalance
)
2941 if (!sds
->power_savings_balance
)
2944 if (sds
->this != sds
->group_leader
||
2945 sds
->group_leader
== sds
->group_min
)
2948 *imbalance
= sds
->min_load_per_task
;
2949 sds
->busiest
= sds
->group_min
;
2954 #else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
2955 static inline void init_sd_power_savings_stats(struct sched_domain
*sd
,
2956 struct sd_lb_stats
*sds
, enum cpu_idle_type idle
)
2961 static inline void update_sd_power_savings_stats(struct sched_group
*group
,
2962 struct sd_lb_stats
*sds
, int local_group
, struct sg_lb_stats
*sgs
)
2967 static inline int check_power_save_busiest_group(struct sd_lb_stats
*sds
,
2968 int this_cpu
, unsigned long *imbalance
)
2972 #endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
2975 unsigned long default_scale_freq_power(struct sched_domain
*sd
, int cpu
)
2977 return SCHED_POWER_SCALE
;
2980 unsigned long __weak
arch_scale_freq_power(struct sched_domain
*sd
, int cpu
)
2982 return default_scale_freq_power(sd
, cpu
);
2985 unsigned long default_scale_smt_power(struct sched_domain
*sd
, int cpu
)
2987 unsigned long weight
= sd
->span_weight
;
2988 unsigned long smt_gain
= sd
->smt_gain
;
2995 unsigned long __weak
arch_scale_smt_power(struct sched_domain
*sd
, int cpu
)
2997 return default_scale_smt_power(sd
, cpu
);
3000 unsigned long scale_rt_power(int cpu
)
3002 struct rq
*rq
= cpu_rq(cpu
);
3003 u64 total
, available
;
3005 total
= sched_avg_period() + (rq
->clock
- rq
->age_stamp
);
3007 if (unlikely(total
< rq
->rt_avg
)) {
3008 /* Ensures that power won't end up being negative */
3011 available
= total
- rq
->rt_avg
;
3014 if (unlikely((s64
)total
< SCHED_POWER_SCALE
))
3015 total
= SCHED_POWER_SCALE
;
3017 total
>>= SCHED_POWER_SHIFT
;
3019 return div_u64(available
, total
);
3022 static void update_cpu_power(struct sched_domain
*sd
, int cpu
)
3024 unsigned long weight
= sd
->span_weight
;
3025 unsigned long power
= SCHED_POWER_SCALE
;
3026 struct sched_group
*sdg
= sd
->groups
;
3028 if ((sd
->flags
& SD_SHARE_CPUPOWER
) && weight
> 1) {
3029 if (sched_feat(ARCH_POWER
))
3030 power
*= arch_scale_smt_power(sd
, cpu
);
3032 power
*= default_scale_smt_power(sd
, cpu
);
3034 power
>>= SCHED_POWER_SHIFT
;
3037 sdg
->sgp
->power_orig
= power
;
3039 if (sched_feat(ARCH_POWER
))
3040 power
*= arch_scale_freq_power(sd
, cpu
);
3042 power
*= default_scale_freq_power(sd
, cpu
);
3044 power
>>= SCHED_POWER_SHIFT
;
3046 power
*= scale_rt_power(cpu
);
3047 power
>>= SCHED_POWER_SHIFT
;
3052 cpu_rq(cpu
)->cpu_power
= power
;
3053 sdg
->sgp
->power
= power
;
3056 static void update_group_power(struct sched_domain
*sd
, int cpu
)
3058 struct sched_domain
*child
= sd
->child
;
3059 struct sched_group
*group
, *sdg
= sd
->groups
;
3060 unsigned long power
;
3063 update_cpu_power(sd
, cpu
);
3069 group
= child
->groups
;
3071 power
+= group
->sgp
->power
;
3072 group
= group
->next
;
3073 } while (group
!= child
->groups
);
3075 sdg
->sgp
->power
= power
;
3079 * Try and fix up capacity for tiny siblings, this is needed when
3080 * things like SD_ASYM_PACKING need f_b_g to select another sibling
3081 * which on its own isn't powerful enough.
3083 * See update_sd_pick_busiest() and check_asym_packing().
3086 fix_small_capacity(struct sched_domain
*sd
, struct sched_group
*group
)
3089 * Only siblings can have significantly less than SCHED_POWER_SCALE
3091 if (!(sd
->flags
& SD_SHARE_CPUPOWER
))
3095 * If ~90% of the cpu_power is still there, we're good.
3097 if (group
->sgp
->power
* 32 > group
->sgp
->power_orig
* 29)
3104 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
3105 * @sd: The sched_domain whose statistics are to be updated.
3106 * @group: sched_group whose statistics are to be updated.
3107 * @this_cpu: Cpu for which load balance is currently performed.
3108 * @idle: Idle status of this_cpu
3109 * @load_idx: Load index of sched_domain of this_cpu for load calc.
3110 * @local_group: Does group contain this_cpu.
3111 * @cpus: Set of cpus considered for load balancing.
3112 * @balance: Should we balance.
3113 * @sgs: variable to hold the statistics for this group.
3115 static inline void update_sg_lb_stats(struct sched_domain
*sd
,
3116 struct sched_group
*group
, int this_cpu
,
3117 enum cpu_idle_type idle
, int load_idx
,
3118 int local_group
, const struct cpumask
*cpus
,
3119 int *balance
, struct sg_lb_stats
*sgs
)
3121 unsigned long load
, max_cpu_load
, min_cpu_load
, max_nr_running
;
3123 unsigned int balance_cpu
= -1, first_idle_cpu
= 0;
3124 unsigned long avg_load_per_task
= 0;
3127 balance_cpu
= group_first_cpu(group
);
3129 /* Tally up the load of all CPUs in the group */
3131 min_cpu_load
= ~0UL;
3134 for_each_cpu_and(i
, sched_group_cpus(group
), cpus
) {
3135 struct rq
*rq
= cpu_rq(i
);
3137 /* Bias balancing toward cpus of our domain */
3139 if (idle_cpu(i
) && !first_idle_cpu
) {
3144 load
= target_load(i
, load_idx
);
3146 load
= source_load(i
, load_idx
);
3147 if (load
> max_cpu_load
) {
3148 max_cpu_load
= load
;
3149 max_nr_running
= rq
->nr_running
;
3151 if (min_cpu_load
> load
)
3152 min_cpu_load
= load
;
3155 sgs
->group_load
+= load
;
3156 sgs
->sum_nr_running
+= rq
->nr_running
;
3157 sgs
->sum_weighted_load
+= weighted_cpuload(i
);
3163 * First idle cpu or the first cpu(busiest) in this sched group
3164 * is eligible for doing load balancing at this and above
3165 * domains. In the newly idle case, we will allow all the cpu's
3166 * to do the newly idle load balance.
3168 if (idle
!= CPU_NEWLY_IDLE
&& local_group
) {
3169 if (balance_cpu
!= this_cpu
) {
3173 update_group_power(sd
, this_cpu
);
3176 /* Adjust by relative CPU power of the group */
3177 sgs
->avg_load
= (sgs
->group_load
*SCHED_POWER_SCALE
) / group
->sgp
->power
;
3180 * Consider the group unbalanced when the imbalance is larger
3181 * than the average weight of a task.
3183 * APZ: with cgroup the avg task weight can vary wildly and
3184 * might not be a suitable number - should we keep a
3185 * normalized nr_running number somewhere that negates
3188 if (sgs
->sum_nr_running
)
3189 avg_load_per_task
= sgs
->sum_weighted_load
/ sgs
->sum_nr_running
;
3191 if ((max_cpu_load
- min_cpu_load
) >= avg_load_per_task
&& max_nr_running
> 1)
3194 sgs
->group_capacity
= DIV_ROUND_CLOSEST(group
->sgp
->power
,
3196 if (!sgs
->group_capacity
)
3197 sgs
->group_capacity
= fix_small_capacity(sd
, group
);
3198 sgs
->group_weight
= group
->group_weight
;
3200 if (sgs
->group_capacity
> sgs
->sum_nr_running
)
3201 sgs
->group_has_capacity
= 1;
3205 * update_sd_pick_busiest - return 1 on busiest group
3206 * @sd: sched_domain whose statistics are to be checked
3207 * @sds: sched_domain statistics
3208 * @sg: sched_group candidate to be checked for being the busiest
3209 * @sgs: sched_group statistics
3210 * @this_cpu: the current cpu
3212 * Determine if @sg is a busier group than the previously selected
3215 static bool update_sd_pick_busiest(struct sched_domain
*sd
,
3216 struct sd_lb_stats
*sds
,
3217 struct sched_group
*sg
,
3218 struct sg_lb_stats
*sgs
,
3221 if (sgs
->avg_load
<= sds
->max_load
)
3224 if (sgs
->sum_nr_running
> sgs
->group_capacity
)
3231 * ASYM_PACKING needs to move all the work to the lowest
3232 * numbered CPUs in the group, therefore mark all groups
3233 * higher than ourself as busy.
3235 if ((sd
->flags
& SD_ASYM_PACKING
) && sgs
->sum_nr_running
&&
3236 this_cpu
< group_first_cpu(sg
)) {
3240 if (group_first_cpu(sds
->busiest
) > group_first_cpu(sg
))
3248 * update_sd_lb_stats - Update sched_group's statistics for load balancing.
3249 * @sd: sched_domain whose statistics are to be updated.
3250 * @this_cpu: Cpu for which load balance is currently performed.
3251 * @idle: Idle status of this_cpu
3252 * @cpus: Set of cpus considered for load balancing.
3253 * @balance: Should we balance.
3254 * @sds: variable to hold the statistics for this sched_domain.
3256 static inline void update_sd_lb_stats(struct sched_domain
*sd
, int this_cpu
,
3257 enum cpu_idle_type idle
, const struct cpumask
*cpus
,
3258 int *balance
, struct sd_lb_stats
*sds
)
3260 struct sched_domain
*child
= sd
->child
;
3261 struct sched_group
*sg
= sd
->groups
;
3262 struct sg_lb_stats sgs
;
3263 int load_idx
, prefer_sibling
= 0;
3265 if (child
&& child
->flags
& SD_PREFER_SIBLING
)
3268 init_sd_power_savings_stats(sd
, sds
, idle
);
3269 load_idx
= get_sd_load_idx(sd
, idle
);
3274 local_group
= cpumask_test_cpu(this_cpu
, sched_group_cpus(sg
));
3275 memset(&sgs
, 0, sizeof(sgs
));
3276 update_sg_lb_stats(sd
, sg
, this_cpu
, idle
, load_idx
,
3277 local_group
, cpus
, balance
, &sgs
);
3279 if (local_group
&& !(*balance
))
3282 sds
->total_load
+= sgs
.group_load
;
3283 sds
->total_pwr
+= sg
->sgp
->power
;
3286 * In case the child domain prefers tasks go to siblings
3287 * first, lower the sg capacity to one so that we'll try
3288 * and move all the excess tasks away. We lower the capacity
3289 * of a group only if the local group has the capacity to fit
3290 * these excess tasks, i.e. nr_running < group_capacity. The
3291 * extra check prevents the case where you always pull from the
3292 * heaviest group when it is already under-utilized (possible
3293 * with a large weight task outweighs the tasks on the system).
3295 if (prefer_sibling
&& !local_group
&& sds
->this_has_capacity
)
3296 sgs
.group_capacity
= min(sgs
.group_capacity
, 1UL);
3299 sds
->this_load
= sgs
.avg_load
;
3301 sds
->this_nr_running
= sgs
.sum_nr_running
;
3302 sds
->this_load_per_task
= sgs
.sum_weighted_load
;
3303 sds
->this_has_capacity
= sgs
.group_has_capacity
;
3304 sds
->this_idle_cpus
= sgs
.idle_cpus
;
3305 } else if (update_sd_pick_busiest(sd
, sds
, sg
, &sgs
, this_cpu
)) {
3306 sds
->max_load
= sgs
.avg_load
;
3308 sds
->busiest_nr_running
= sgs
.sum_nr_running
;
3309 sds
->busiest_idle_cpus
= sgs
.idle_cpus
;
3310 sds
->busiest_group_capacity
= sgs
.group_capacity
;
3311 sds
->busiest_load_per_task
= sgs
.sum_weighted_load
;
3312 sds
->busiest_has_capacity
= sgs
.group_has_capacity
;
3313 sds
->busiest_group_weight
= sgs
.group_weight
;
3314 sds
->group_imb
= sgs
.group_imb
;
3317 update_sd_power_savings_stats(sg
, sds
, local_group
, &sgs
);
3319 } while (sg
!= sd
->groups
);
3322 int __weak
arch_sd_sibling_asym_packing(void)
3324 return 0*SD_ASYM_PACKING
;
3328 * check_asym_packing - Check to see if the group is packed into the
3331 * This is primarily intended to used at the sibling level. Some
3332 * cores like POWER7 prefer to use lower numbered SMT threads. In the
3333 * case of POWER7, it can move to lower SMT modes only when higher
3334 * threads are idle. When in lower SMT modes, the threads will
3335 * perform better since they share less core resources. Hence when we
3336 * have idle threads, we want them to be the higher ones.
3338 * This packing function is run on idle threads. It checks to see if
3339 * the busiest CPU in this domain (core in the P7 case) has a higher
3340 * CPU number than the packing function is being run on. Here we are
3341 * assuming lower CPU number will be equivalent to lower a SMT thread
3344 * Returns 1 when packing is required and a task should be moved to
3345 * this CPU. The amount of the imbalance is returned in *imbalance.
3347 * @sd: The sched_domain whose packing is to be checked.
3348 * @sds: Statistics of the sched_domain which is to be packed
3349 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
3350 * @imbalance: returns amount of imbalanced due to packing.
3352 static int check_asym_packing(struct sched_domain
*sd
,
3353 struct sd_lb_stats
*sds
,
3354 int this_cpu
, unsigned long *imbalance
)
3358 if (!(sd
->flags
& SD_ASYM_PACKING
))
3364 busiest_cpu
= group_first_cpu(sds
->busiest
);
3365 if (this_cpu
> busiest_cpu
)
3368 *imbalance
= DIV_ROUND_CLOSEST(sds
->max_load
* sds
->busiest
->sgp
->power
,
3374 * fix_small_imbalance - Calculate the minor imbalance that exists
3375 * amongst the groups of a sched_domain, during
3377 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
3378 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
3379 * @imbalance: Variable to store the imbalance.
3381 static inline void fix_small_imbalance(struct sd_lb_stats
*sds
,
3382 int this_cpu
, unsigned long *imbalance
)
3384 unsigned long tmp
, pwr_now
= 0, pwr_move
= 0;
3385 unsigned int imbn
= 2;
3386 unsigned long scaled_busy_load_per_task
;
3388 if (sds
->this_nr_running
) {
3389 sds
->this_load_per_task
/= sds
->this_nr_running
;
3390 if (sds
->busiest_load_per_task
>
3391 sds
->this_load_per_task
)
3394 sds
->this_load_per_task
=
3395 cpu_avg_load_per_task(this_cpu
);
3397 scaled_busy_load_per_task
= sds
->busiest_load_per_task
3398 * SCHED_POWER_SCALE
;
3399 scaled_busy_load_per_task
/= sds
->busiest
->sgp
->power
;
3401 if (sds
->max_load
- sds
->this_load
+ scaled_busy_load_per_task
>=
3402 (scaled_busy_load_per_task
* imbn
)) {
3403 *imbalance
= sds
->busiest_load_per_task
;
3408 * OK, we don't have enough imbalance to justify moving tasks,
3409 * however we may be able to increase total CPU power used by
3413 pwr_now
+= sds
->busiest
->sgp
->power
*
3414 min(sds
->busiest_load_per_task
, sds
->max_load
);
3415 pwr_now
+= sds
->this->sgp
->power
*
3416 min(sds
->this_load_per_task
, sds
->this_load
);
3417 pwr_now
/= SCHED_POWER_SCALE
;
3419 /* Amount of load we'd subtract */
3420 tmp
= (sds
->busiest_load_per_task
* SCHED_POWER_SCALE
) /
3421 sds
->busiest
->sgp
->power
;
3422 if (sds
->max_load
> tmp
)
3423 pwr_move
+= sds
->busiest
->sgp
->power
*
3424 min(sds
->busiest_load_per_task
, sds
->max_load
- tmp
);
3426 /* Amount of load we'd add */
3427 if (sds
->max_load
* sds
->busiest
->sgp
->power
<
3428 sds
->busiest_load_per_task
* SCHED_POWER_SCALE
)
3429 tmp
= (sds
->max_load
* sds
->busiest
->sgp
->power
) /
3430 sds
->this->sgp
->power
;
3432 tmp
= (sds
->busiest_load_per_task
* SCHED_POWER_SCALE
) /
3433 sds
->this->sgp
->power
;
3434 pwr_move
+= sds
->this->sgp
->power
*
3435 min(sds
->this_load_per_task
, sds
->this_load
+ tmp
);
3436 pwr_move
/= SCHED_POWER_SCALE
;
3438 /* Move if we gain throughput */
3439 if (pwr_move
> pwr_now
)
3440 *imbalance
= sds
->busiest_load_per_task
;
3444 * calculate_imbalance - Calculate the amount of imbalance present within the
3445 * groups of a given sched_domain during load balance.
3446 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
3447 * @this_cpu: Cpu for which currently load balance is being performed.
3448 * @imbalance: The variable to store the imbalance.
3450 static inline void calculate_imbalance(struct sd_lb_stats
*sds
, int this_cpu
,
3451 unsigned long *imbalance
)
3453 unsigned long max_pull
, load_above_capacity
= ~0UL;
3455 sds
->busiest_load_per_task
/= sds
->busiest_nr_running
;
3456 if (sds
->group_imb
) {
3457 sds
->busiest_load_per_task
=
3458 min(sds
->busiest_load_per_task
, sds
->avg_load
);
3462 * In the presence of smp nice balancing, certain scenarios can have
3463 * max load less than avg load(as we skip the groups at or below
3464 * its cpu_power, while calculating max_load..)
3466 if (sds
->max_load
< sds
->avg_load
) {
3468 return fix_small_imbalance(sds
, this_cpu
, imbalance
);
3471 if (!sds
->group_imb
) {
3473 * Don't want to pull so many tasks that a group would go idle.
3475 load_above_capacity
= (sds
->busiest_nr_running
-
3476 sds
->busiest_group_capacity
);
3478 load_above_capacity
*= (SCHED_LOAD_SCALE
* SCHED_POWER_SCALE
);
3480 load_above_capacity
/= sds
->busiest
->sgp
->power
;
3484 * We're trying to get all the cpus to the average_load, so we don't
3485 * want to push ourselves above the average load, nor do we wish to
3486 * reduce the max loaded cpu below the average load. At the same time,
3487 * we also don't want to reduce the group load below the group capacity
3488 * (so that we can implement power-savings policies etc). Thus we look
3489 * for the minimum possible imbalance.
3490 * Be careful of negative numbers as they'll appear as very large values
3491 * with unsigned longs.
3493 max_pull
= min(sds
->max_load
- sds
->avg_load
, load_above_capacity
);
3495 /* How much load to actually move to equalise the imbalance */
3496 *imbalance
= min(max_pull
* sds
->busiest
->sgp
->power
,
3497 (sds
->avg_load
- sds
->this_load
) * sds
->this->sgp
->power
)
3498 / SCHED_POWER_SCALE
;
3501 * if *imbalance is less than the average load per runnable task
3502 * there is no guarantee that any tasks will be moved so we'll have
3503 * a think about bumping its value to force at least one task to be
3506 if (*imbalance
< sds
->busiest_load_per_task
)
3507 return fix_small_imbalance(sds
, this_cpu
, imbalance
);
3511 /******* find_busiest_group() helpers end here *********************/
3514 * find_busiest_group - Returns the busiest group within the sched_domain
3515 * if there is an imbalance. If there isn't an imbalance, and
3516 * the user has opted for power-savings, it returns a group whose
3517 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
3518 * such a group exists.
3520 * Also calculates the amount of weighted load which should be moved
3521 * to restore balance.
3523 * @sd: The sched_domain whose busiest group is to be returned.
3524 * @this_cpu: The cpu for which load balancing is currently being performed.
3525 * @imbalance: Variable which stores amount of weighted load which should
3526 * be moved to restore balance/put a group to idle.
3527 * @idle: The idle status of this_cpu.
3528 * @cpus: The set of CPUs under consideration for load-balancing.
3529 * @balance: Pointer to a variable indicating if this_cpu
3530 * is the appropriate cpu to perform load balancing at this_level.
3532 * Returns: - the busiest group if imbalance exists.
3533 * - If no imbalance and user has opted for power-savings balance,
3534 * return the least loaded group whose CPUs can be
3535 * put to idle by rebalancing its tasks onto our group.
3537 static struct sched_group
*
3538 find_busiest_group(struct sched_domain
*sd
, int this_cpu
,
3539 unsigned long *imbalance
, enum cpu_idle_type idle
,
3540 const struct cpumask
*cpus
, int *balance
)
3542 struct sd_lb_stats sds
;
3544 memset(&sds
, 0, sizeof(sds
));
3547 * Compute the various statistics relavent for load balancing at
3550 update_sd_lb_stats(sd
, this_cpu
, idle
, cpus
, balance
, &sds
);
3553 * this_cpu is not the appropriate cpu to perform load balancing at
3559 if ((idle
== CPU_IDLE
|| idle
== CPU_NEWLY_IDLE
) &&
3560 check_asym_packing(sd
, &sds
, this_cpu
, imbalance
))
3563 /* There is no busy sibling group to pull tasks from */
3564 if (!sds
.busiest
|| sds
.busiest_nr_running
== 0)
3567 sds
.avg_load
= (SCHED_POWER_SCALE
* sds
.total_load
) / sds
.total_pwr
;
3570 * If the busiest group is imbalanced the below checks don't
3571 * work because they assumes all things are equal, which typically
3572 * isn't true due to cpus_allowed constraints and the like.
3577 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
3578 if (idle
== CPU_NEWLY_IDLE
&& sds
.this_has_capacity
&&
3579 !sds
.busiest_has_capacity
)
3583 * If the local group is more busy than the selected busiest group
3584 * don't try and pull any tasks.
3586 if (sds
.this_load
>= sds
.max_load
)
3590 * Don't pull any tasks if this group is already above the domain
3593 if (sds
.this_load
>= sds
.avg_load
)
3596 if (idle
== CPU_IDLE
) {
3598 * This cpu is idle. If the busiest group load doesn't
3599 * have more tasks than the number of available cpu's and
3600 * there is no imbalance between this and busiest group
3601 * wrt to idle cpu's, it is balanced.
3603 if ((sds
.this_idle_cpus
<= sds
.busiest_idle_cpus
+ 1) &&
3604 sds
.busiest_nr_running
<= sds
.busiest_group_weight
)
3608 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
3609 * imbalance_pct to be conservative.
3611 if (100 * sds
.max_load
<= sd
->imbalance_pct
* sds
.this_load
)
3616 /* Looks like there is an imbalance. Compute it */
3617 calculate_imbalance(&sds
, this_cpu
, imbalance
);
3622 * There is no obvious imbalance. But check if we can do some balancing
3625 if (check_power_save_busiest_group(&sds
, this_cpu
, imbalance
))
3633 * find_busiest_queue - find the busiest runqueue among the cpus in group.
3636 find_busiest_queue(struct sched_domain
*sd
, struct sched_group
*group
,
3637 enum cpu_idle_type idle
, unsigned long imbalance
,
3638 const struct cpumask
*cpus
)
3640 struct rq
*busiest
= NULL
, *rq
;
3641 unsigned long max_load
= 0;
3644 for_each_cpu(i
, sched_group_cpus(group
)) {
3645 unsigned long power
= power_of(i
);
3646 unsigned long capacity
= DIV_ROUND_CLOSEST(power
,
3651 capacity
= fix_small_capacity(sd
, group
);
3653 if (!cpumask_test_cpu(i
, cpus
))
3657 wl
= weighted_cpuload(i
);
3660 * When comparing with imbalance, use weighted_cpuload()
3661 * which is not scaled with the cpu power.
3663 if (capacity
&& rq
->nr_running
== 1 && wl
> imbalance
)
3667 * For the load comparisons with the other cpu's, consider
3668 * the weighted_cpuload() scaled with the cpu power, so that
3669 * the load can be moved away from the cpu that is potentially
3670 * running at a lower capacity.
3672 wl
= (wl
* SCHED_POWER_SCALE
) / power
;
3674 if (wl
> max_load
) {
3684 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
3685 * so long as it is large enough.
3687 #define MAX_PINNED_INTERVAL 512
3689 /* Working cpumask for load_balance and load_balance_newidle. */
3690 static DEFINE_PER_CPU(cpumask_var_t
, load_balance_tmpmask
);
3692 static int need_active_balance(struct sched_domain
*sd
, int idle
,
3693 int busiest_cpu
, int this_cpu
)
3695 if (idle
== CPU_NEWLY_IDLE
) {
3698 * ASYM_PACKING needs to force migrate tasks from busy but
3699 * higher numbered CPUs in order to pack all tasks in the
3700 * lowest numbered CPUs.
3702 if ((sd
->flags
& SD_ASYM_PACKING
) && busiest_cpu
> this_cpu
)
3706 * The only task running in a non-idle cpu can be moved to this
3707 * cpu in an attempt to completely freeup the other CPU
3710 * The package power saving logic comes from
3711 * find_busiest_group(). If there are no imbalance, then
3712 * f_b_g() will return NULL. However when sched_mc={1,2} then
3713 * f_b_g() will select a group from which a running task may be
3714 * pulled to this cpu in order to make the other package idle.
3715 * If there is no opportunity to make a package idle and if
3716 * there are no imbalance, then f_b_g() will return NULL and no
3717 * action will be taken in load_balance_newidle().
3719 * Under normal task pull operation due to imbalance, there
3720 * will be more than one task in the source run queue and
3721 * move_tasks() will succeed. ld_moved will be true and this
3722 * active balance code will not be triggered.
3724 if (sched_mc_power_savings
< POWERSAVINGS_BALANCE_WAKEUP
)
3728 return unlikely(sd
->nr_balance_failed
> sd
->cache_nice_tries
+2);
3731 static int active_load_balance_cpu_stop(void *data
);
3734 * Check this_cpu to ensure it is balanced within domain. Attempt to move
3735 * tasks if there is an imbalance.
3737 static int load_balance(int this_cpu
, struct rq
*this_rq
,
3738 struct sched_domain
*sd
, enum cpu_idle_type idle
,
3741 int ld_moved
, all_pinned
= 0, active_balance
= 0;
3742 struct sched_group
*group
;
3743 unsigned long imbalance
;
3745 unsigned long flags
;
3746 struct cpumask
*cpus
= __get_cpu_var(load_balance_tmpmask
);
3748 cpumask_copy(cpus
, cpu_active_mask
);
3750 schedstat_inc(sd
, lb_count
[idle
]);
3753 group
= find_busiest_group(sd
, this_cpu
, &imbalance
, idle
,
3760 schedstat_inc(sd
, lb_nobusyg
[idle
]);
3764 busiest
= find_busiest_queue(sd
, group
, idle
, imbalance
, cpus
);
3766 schedstat_inc(sd
, lb_nobusyq
[idle
]);
3770 BUG_ON(busiest
== this_rq
);
3772 schedstat_add(sd
, lb_imbalance
[idle
], imbalance
);
3775 if (busiest
->nr_running
> 1) {
3777 * Attempt to move tasks. If find_busiest_group has found
3778 * an imbalance but busiest->nr_running <= 1, the group is
3779 * still unbalanced. ld_moved simply stays zero, so it is
3780 * correctly treated as an imbalance.
3783 local_irq_save(flags
);
3784 double_rq_lock(this_rq
, busiest
);
3785 ld_moved
= move_tasks(this_rq
, this_cpu
, busiest
,
3786 imbalance
, sd
, idle
, &all_pinned
);
3787 double_rq_unlock(this_rq
, busiest
);
3788 local_irq_restore(flags
);
3791 * some other cpu did the load balance for us.
3793 if (ld_moved
&& this_cpu
!= smp_processor_id())
3794 resched_cpu(this_cpu
);
3796 /* All tasks on this runqueue were pinned by CPU affinity */
3797 if (unlikely(all_pinned
)) {
3798 cpumask_clear_cpu(cpu_of(busiest
), cpus
);
3799 if (!cpumask_empty(cpus
))
3806 schedstat_inc(sd
, lb_failed
[idle
]);
3808 * Increment the failure counter only on periodic balance.
3809 * We do not want newidle balance, which can be very
3810 * frequent, pollute the failure counter causing
3811 * excessive cache_hot migrations and active balances.
3813 if (idle
!= CPU_NEWLY_IDLE
)
3814 sd
->nr_balance_failed
++;
3816 if (need_active_balance(sd
, idle
, cpu_of(busiest
), this_cpu
)) {
3817 raw_spin_lock_irqsave(&busiest
->lock
, flags
);
3819 /* don't kick the active_load_balance_cpu_stop,
3820 * if the curr task on busiest cpu can't be
3823 if (!cpumask_test_cpu(this_cpu
,
3824 &busiest
->curr
->cpus_allowed
)) {
3825 raw_spin_unlock_irqrestore(&busiest
->lock
,
3828 goto out_one_pinned
;
3832 * ->active_balance synchronizes accesses to
3833 * ->active_balance_work. Once set, it's cleared
3834 * only after active load balance is finished.
3836 if (!busiest
->active_balance
) {
3837 busiest
->active_balance
= 1;
3838 busiest
->push_cpu
= this_cpu
;
3841 raw_spin_unlock_irqrestore(&busiest
->lock
, flags
);
3844 stop_one_cpu_nowait(cpu_of(busiest
),
3845 active_load_balance_cpu_stop
, busiest
,
3846 &busiest
->active_balance_work
);
3849 * We've kicked active balancing, reset the failure
3852 sd
->nr_balance_failed
= sd
->cache_nice_tries
+1;
3855 sd
->nr_balance_failed
= 0;
3857 if (likely(!active_balance
)) {
3858 /* We were unbalanced, so reset the balancing interval */
3859 sd
->balance_interval
= sd
->min_interval
;
3862 * If we've begun active balancing, start to back off. This
3863 * case may not be covered by the all_pinned logic if there
3864 * is only 1 task on the busy runqueue (because we don't call
3867 if (sd
->balance_interval
< sd
->max_interval
)
3868 sd
->balance_interval
*= 2;
3874 schedstat_inc(sd
, lb_balanced
[idle
]);
3876 sd
->nr_balance_failed
= 0;
3879 /* tune up the balancing interval */
3880 if ((all_pinned
&& sd
->balance_interval
< MAX_PINNED_INTERVAL
) ||
3881 (sd
->balance_interval
< sd
->max_interval
))
3882 sd
->balance_interval
*= 2;
3890 * idle_balance is called by schedule() if this_cpu is about to become
3891 * idle. Attempts to pull tasks from other CPUs.
3893 static void idle_balance(int this_cpu
, struct rq
*this_rq
)
3895 struct sched_domain
*sd
;
3896 int pulled_task
= 0;
3897 unsigned long next_balance
= jiffies
+ HZ
;
3899 this_rq
->idle_stamp
= this_rq
->clock
;
3901 if (this_rq
->avg_idle
< sysctl_sched_migration_cost
)
3905 * Drop the rq->lock, but keep IRQ/preempt disabled.
3907 raw_spin_unlock(&this_rq
->lock
);
3909 update_shares(this_cpu
);
3911 for_each_domain(this_cpu
, sd
) {
3912 unsigned long interval
;
3915 if (!(sd
->flags
& SD_LOAD_BALANCE
))
3918 if (sd
->flags
& SD_BALANCE_NEWIDLE
) {
3919 /* If we've pulled tasks over stop searching: */
3920 pulled_task
= load_balance(this_cpu
, this_rq
,
3921 sd
, CPU_NEWLY_IDLE
, &balance
);
3924 interval
= msecs_to_jiffies(sd
->balance_interval
);
3925 if (time_after(next_balance
, sd
->last_balance
+ interval
))
3926 next_balance
= sd
->last_balance
+ interval
;
3928 this_rq
->idle_stamp
= 0;
3934 raw_spin_lock(&this_rq
->lock
);
3936 if (pulled_task
|| time_after(jiffies
, this_rq
->next_balance
)) {
3938 * We are going idle. next_balance may be set based on
3939 * a busy processor. So reset next_balance.
3941 this_rq
->next_balance
= next_balance
;
3946 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
3947 * running tasks off the busiest CPU onto idle CPUs. It requires at
3948 * least 1 task to be running on each physical CPU where possible, and
3949 * avoids physical / logical imbalances.
3951 static int active_load_balance_cpu_stop(void *data
)
3953 struct rq
*busiest_rq
= data
;
3954 int busiest_cpu
= cpu_of(busiest_rq
);
3955 int target_cpu
= busiest_rq
->push_cpu
;
3956 struct rq
*target_rq
= cpu_rq(target_cpu
);
3957 struct sched_domain
*sd
;
3959 raw_spin_lock_irq(&busiest_rq
->lock
);
3961 /* make sure the requested cpu hasn't gone down in the meantime */
3962 if (unlikely(busiest_cpu
!= smp_processor_id() ||
3963 !busiest_rq
->active_balance
))
3966 /* Is there any task to move? */
3967 if (busiest_rq
->nr_running
<= 1)
3971 * This condition is "impossible", if it occurs
3972 * we need to fix it. Originally reported by
3973 * Bjorn Helgaas on a 128-cpu setup.
3975 BUG_ON(busiest_rq
== target_rq
);
3977 /* move a task from busiest_rq to target_rq */
3978 double_lock_balance(busiest_rq
, target_rq
);
3980 /* Search for an sd spanning us and the target CPU. */
3982 for_each_domain(target_cpu
, sd
) {
3983 if ((sd
->flags
& SD_LOAD_BALANCE
) &&
3984 cpumask_test_cpu(busiest_cpu
, sched_domain_span(sd
)))
3989 schedstat_inc(sd
, alb_count
);
3991 if (move_one_task(target_rq
, target_cpu
, busiest_rq
,
3993 schedstat_inc(sd
, alb_pushed
);
3995 schedstat_inc(sd
, alb_failed
);
3998 double_unlock_balance(busiest_rq
, target_rq
);
4000 busiest_rq
->active_balance
= 0;
4001 raw_spin_unlock_irq(&busiest_rq
->lock
);
4007 static DEFINE_PER_CPU(struct call_single_data
, remote_sched_softirq_cb
);
4009 static void trigger_sched_softirq(void *data
)
4011 raise_softirq_irqoff(SCHED_SOFTIRQ
);
4014 static inline void init_sched_softirq_csd(struct call_single_data
*csd
)
4016 csd
->func
= trigger_sched_softirq
;
4023 * idle load balancing details
4024 * - One of the idle CPUs nominates itself as idle load_balancer, while
4026 * - This idle load balancer CPU will also go into tickless mode when
4027 * it is idle, just like all other idle CPUs
4028 * - When one of the busy CPUs notice that there may be an idle rebalancing
4029 * needed, they will kick the idle load balancer, which then does idle
4030 * load balancing for all the idle CPUs.
4033 atomic_t load_balancer
;
4034 atomic_t first_pick_cpu
;
4035 atomic_t second_pick_cpu
;
4036 cpumask_var_t idle_cpus_mask
;
4037 cpumask_var_t grp_idle_mask
;
4038 unsigned long next_balance
; /* in jiffy units */
4039 } nohz ____cacheline_aligned
;
4041 int get_nohz_load_balancer(void)
4043 return atomic_read(&nohz
.load_balancer
);
4046 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
4048 * lowest_flag_domain - Return lowest sched_domain containing flag.
4049 * @cpu: The cpu whose lowest level of sched domain is to
4051 * @flag: The flag to check for the lowest sched_domain
4052 * for the given cpu.
4054 * Returns the lowest sched_domain of a cpu which contains the given flag.
4056 static inline struct sched_domain
*lowest_flag_domain(int cpu
, int flag
)
4058 struct sched_domain
*sd
;
4060 for_each_domain(cpu
, sd
)
4061 if (sd
->flags
& flag
)
4068 * for_each_flag_domain - Iterates over sched_domains containing the flag.
4069 * @cpu: The cpu whose domains we're iterating over.
4070 * @sd: variable holding the value of the power_savings_sd
4072 * @flag: The flag to filter the sched_domains to be iterated.
4074 * Iterates over all the scheduler domains for a given cpu that has the 'flag'
4075 * set, starting from the lowest sched_domain to the highest.
4077 #define for_each_flag_domain(cpu, sd, flag) \
4078 for (sd = lowest_flag_domain(cpu, flag); \
4079 (sd && (sd->flags & flag)); sd = sd->parent)
4082 * is_semi_idle_group - Checks if the given sched_group is semi-idle.
4083 * @ilb_group: group to be checked for semi-idleness
4085 * Returns: 1 if the group is semi-idle. 0 otherwise.
4087 * We define a sched_group to be semi idle if it has atleast one idle-CPU
4088 * and atleast one non-idle CPU. This helper function checks if the given
4089 * sched_group is semi-idle or not.
4091 static inline int is_semi_idle_group(struct sched_group
*ilb_group
)
4093 cpumask_and(nohz
.grp_idle_mask
, nohz
.idle_cpus_mask
,
4094 sched_group_cpus(ilb_group
));
4097 * A sched_group is semi-idle when it has atleast one busy cpu
4098 * and atleast one idle cpu.
4100 if (cpumask_empty(nohz
.grp_idle_mask
))
4103 if (cpumask_equal(nohz
.grp_idle_mask
, sched_group_cpus(ilb_group
)))
4109 * find_new_ilb - Finds the optimum idle load balancer for nomination.
4110 * @cpu: The cpu which is nominating a new idle_load_balancer.
4112 * Returns: Returns the id of the idle load balancer if it exists,
4113 * Else, returns >= nr_cpu_ids.
4115 * This algorithm picks the idle load balancer such that it belongs to a
4116 * semi-idle powersavings sched_domain. The idea is to try and avoid
4117 * completely idle packages/cores just for the purpose of idle load balancing
4118 * when there are other idle cpu's which are better suited for that job.
4120 static int find_new_ilb(int cpu
)
4122 struct sched_domain
*sd
;
4123 struct sched_group
*ilb_group
;
4124 int ilb
= nr_cpu_ids
;
4127 * Have idle load balancer selection from semi-idle packages only
4128 * when power-aware load balancing is enabled
4130 if (!(sched_smt_power_savings
|| sched_mc_power_savings
))
4134 * Optimize for the case when we have no idle CPUs or only one
4135 * idle CPU. Don't walk the sched_domain hierarchy in such cases
4137 if (cpumask_weight(nohz
.idle_cpus_mask
) < 2)
4141 for_each_flag_domain(cpu
, sd
, SD_POWERSAVINGS_BALANCE
) {
4142 ilb_group
= sd
->groups
;
4145 if (is_semi_idle_group(ilb_group
)) {
4146 ilb
= cpumask_first(nohz
.grp_idle_mask
);
4150 ilb_group
= ilb_group
->next
;
4152 } while (ilb_group
!= sd
->groups
);
4160 #else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
4161 static inline int find_new_ilb(int call_cpu
)
4168 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
4169 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
4170 * CPU (if there is one).
4172 static void nohz_balancer_kick(int cpu
)
4176 nohz
.next_balance
++;
4178 ilb_cpu
= get_nohz_load_balancer();
4180 if (ilb_cpu
>= nr_cpu_ids
) {
4181 ilb_cpu
= cpumask_first(nohz
.idle_cpus_mask
);
4182 if (ilb_cpu
>= nr_cpu_ids
)
4186 if (!cpu_rq(ilb_cpu
)->nohz_balance_kick
) {
4187 struct call_single_data
*cp
;
4189 cpu_rq(ilb_cpu
)->nohz_balance_kick
= 1;
4190 cp
= &per_cpu(remote_sched_softirq_cb
, cpu
);
4191 __smp_call_function_single(ilb_cpu
, cp
, 0);
4197 * This routine will try to nominate the ilb (idle load balancing)
4198 * owner among the cpus whose ticks are stopped. ilb owner will do the idle
4199 * load balancing on behalf of all those cpus.
4201 * When the ilb owner becomes busy, we will not have new ilb owner until some
4202 * idle CPU wakes up and goes back to idle or some busy CPU tries to kick
4203 * idle load balancing by kicking one of the idle CPUs.
4205 * Ticks are stopped for the ilb owner as well, with busy CPU kicking this
4206 * ilb owner CPU in future (when there is a need for idle load balancing on
4207 * behalf of all idle CPUs).
4209 void select_nohz_load_balancer(int stop_tick
)
4211 int cpu
= smp_processor_id();
4214 if (!cpu_active(cpu
)) {
4215 if (atomic_read(&nohz
.load_balancer
) != cpu
)
4219 * If we are going offline and still the leader,
4222 if (atomic_cmpxchg(&nohz
.load_balancer
, cpu
,
4229 cpumask_set_cpu(cpu
, nohz
.idle_cpus_mask
);
4231 if (atomic_read(&nohz
.first_pick_cpu
) == cpu
)
4232 atomic_cmpxchg(&nohz
.first_pick_cpu
, cpu
, nr_cpu_ids
);
4233 if (atomic_read(&nohz
.second_pick_cpu
) == cpu
)
4234 atomic_cmpxchg(&nohz
.second_pick_cpu
, cpu
, nr_cpu_ids
);
4236 if (atomic_read(&nohz
.load_balancer
) >= nr_cpu_ids
) {
4239 /* make me the ilb owner */
4240 if (atomic_cmpxchg(&nohz
.load_balancer
, nr_cpu_ids
,
4245 * Check to see if there is a more power-efficient
4248 new_ilb
= find_new_ilb(cpu
);
4249 if (new_ilb
< nr_cpu_ids
&& new_ilb
!= cpu
) {
4250 atomic_set(&nohz
.load_balancer
, nr_cpu_ids
);
4251 resched_cpu(new_ilb
);
4257 if (!cpumask_test_cpu(cpu
, nohz
.idle_cpus_mask
))
4260 cpumask_clear_cpu(cpu
, nohz
.idle_cpus_mask
);
4262 if (atomic_read(&nohz
.load_balancer
) == cpu
)
4263 if (atomic_cmpxchg(&nohz
.load_balancer
, cpu
,
4271 static DEFINE_SPINLOCK(balancing
);
4273 static unsigned long __read_mostly max_load_balance_interval
= HZ
/10;
4276 * Scale the max load_balance interval with the number of CPUs in the system.
4277 * This trades load-balance latency on larger machines for less cross talk.
4279 static void update_max_interval(void)
4281 max_load_balance_interval
= HZ
*num_online_cpus()/10;
4285 * It checks each scheduling domain to see if it is due to be balanced,
4286 * and initiates a balancing operation if so.
4288 * Balancing parameters are set up in arch_init_sched_domains.
4290 static void rebalance_domains(int cpu
, enum cpu_idle_type idle
)
4293 struct rq
*rq
= cpu_rq(cpu
);
4294 unsigned long interval
;
4295 struct sched_domain
*sd
;
4296 /* Earliest time when we have to do rebalance again */
4297 unsigned long next_balance
= jiffies
+ 60*HZ
;
4298 int update_next_balance
= 0;
4304 for_each_domain(cpu
, sd
) {
4305 if (!(sd
->flags
& SD_LOAD_BALANCE
))
4308 interval
= sd
->balance_interval
;
4309 if (idle
!= CPU_IDLE
)
4310 interval
*= sd
->busy_factor
;
4312 /* scale ms to jiffies */
4313 interval
= msecs_to_jiffies(interval
);
4314 interval
= clamp(interval
, 1UL, max_load_balance_interval
);
4316 need_serialize
= sd
->flags
& SD_SERIALIZE
;
4318 if (need_serialize
) {
4319 if (!spin_trylock(&balancing
))
4323 if (time_after_eq(jiffies
, sd
->last_balance
+ interval
)) {
4324 if (load_balance(cpu
, rq
, sd
, idle
, &balance
)) {
4326 * We've pulled tasks over so either we're no
4329 idle
= CPU_NOT_IDLE
;
4331 sd
->last_balance
= jiffies
;
4334 spin_unlock(&balancing
);
4336 if (time_after(next_balance
, sd
->last_balance
+ interval
)) {
4337 next_balance
= sd
->last_balance
+ interval
;
4338 update_next_balance
= 1;
4342 * Stop the load balance at this level. There is another
4343 * CPU in our sched group which is doing load balancing more
4352 * next_balance will be updated only when there is a need.
4353 * When the cpu is attached to null domain for ex, it will not be
4356 if (likely(update_next_balance
))
4357 rq
->next_balance
= next_balance
;
4362 * In CONFIG_NO_HZ case, the idle balance kickee will do the
4363 * rebalancing for all the cpus for whom scheduler ticks are stopped.
4365 static void nohz_idle_balance(int this_cpu
, enum cpu_idle_type idle
)
4367 struct rq
*this_rq
= cpu_rq(this_cpu
);
4371 if (idle
!= CPU_IDLE
|| !this_rq
->nohz_balance_kick
)
4374 for_each_cpu(balance_cpu
, nohz
.idle_cpus_mask
) {
4375 if (balance_cpu
== this_cpu
)
4379 * If this cpu gets work to do, stop the load balancing
4380 * work being done for other cpus. Next load
4381 * balancing owner will pick it up.
4383 if (need_resched()) {
4384 this_rq
->nohz_balance_kick
= 0;
4388 raw_spin_lock_irq(&this_rq
->lock
);
4389 update_rq_clock(this_rq
);
4390 update_cpu_load(this_rq
);
4391 raw_spin_unlock_irq(&this_rq
->lock
);
4393 rebalance_domains(balance_cpu
, CPU_IDLE
);
4395 rq
= cpu_rq(balance_cpu
);
4396 if (time_after(this_rq
->next_balance
, rq
->next_balance
))
4397 this_rq
->next_balance
= rq
->next_balance
;
4399 nohz
.next_balance
= this_rq
->next_balance
;
4400 this_rq
->nohz_balance_kick
= 0;
4404 * Current heuristic for kicking the idle load balancer
4405 * - first_pick_cpu is the one of the busy CPUs. It will kick
4406 * idle load balancer when it has more than one process active. This
4407 * eliminates the need for idle load balancing altogether when we have
4408 * only one running process in the system (common case).
4409 * - If there are more than one busy CPU, idle load balancer may have
4410 * to run for active_load_balance to happen (i.e., two busy CPUs are
4411 * SMT or core siblings and can run better if they move to different
4412 * physical CPUs). So, second_pick_cpu is the second of the busy CPUs
4413 * which will kick idle load balancer as soon as it has any load.
4415 static inline int nohz_kick_needed(struct rq
*rq
, int cpu
)
4417 unsigned long now
= jiffies
;
4419 int first_pick_cpu
, second_pick_cpu
;
4421 if (time_before(now
, nohz
.next_balance
))
4424 if (rq
->idle_at_tick
)
4427 first_pick_cpu
= atomic_read(&nohz
.first_pick_cpu
);
4428 second_pick_cpu
= atomic_read(&nohz
.second_pick_cpu
);
4430 if (first_pick_cpu
< nr_cpu_ids
&& first_pick_cpu
!= cpu
&&
4431 second_pick_cpu
< nr_cpu_ids
&& second_pick_cpu
!= cpu
)
4434 ret
= atomic_cmpxchg(&nohz
.first_pick_cpu
, nr_cpu_ids
, cpu
);
4435 if (ret
== nr_cpu_ids
|| ret
== cpu
) {
4436 atomic_cmpxchg(&nohz
.second_pick_cpu
, cpu
, nr_cpu_ids
);
4437 if (rq
->nr_running
> 1)
4440 ret
= atomic_cmpxchg(&nohz
.second_pick_cpu
, nr_cpu_ids
, cpu
);
4441 if (ret
== nr_cpu_ids
|| ret
== cpu
) {
4449 static void nohz_idle_balance(int this_cpu
, enum cpu_idle_type idle
) { }
4453 * run_rebalance_domains is triggered when needed from the scheduler tick.
4454 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
4456 static void run_rebalance_domains(struct softirq_action
*h
)
4458 int this_cpu
= smp_processor_id();
4459 struct rq
*this_rq
= cpu_rq(this_cpu
);
4460 enum cpu_idle_type idle
= this_rq
->idle_at_tick
?
4461 CPU_IDLE
: CPU_NOT_IDLE
;
4463 rebalance_domains(this_cpu
, idle
);
4466 * If this cpu has a pending nohz_balance_kick, then do the
4467 * balancing on behalf of the other idle cpus whose ticks are
4470 nohz_idle_balance(this_cpu
, idle
);
4473 static inline int on_null_domain(int cpu
)
4475 return !rcu_dereference_sched(cpu_rq(cpu
)->sd
);
4479 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
4481 static inline void trigger_load_balance(struct rq
*rq
, int cpu
)
4483 /* Don't need to rebalance while attached to NULL domain */
4484 if (time_after_eq(jiffies
, rq
->next_balance
) &&
4485 likely(!on_null_domain(cpu
)))
4486 raise_softirq(SCHED_SOFTIRQ
);
4488 else if (nohz_kick_needed(rq
, cpu
) && likely(!on_null_domain(cpu
)))
4489 nohz_balancer_kick(cpu
);
4493 static void rq_online_fair(struct rq
*rq
)
4498 static void rq_offline_fair(struct rq
*rq
)
4503 #else /* CONFIG_SMP */
4506 * on UP we do not need to balance between CPUs:
4508 static inline void idle_balance(int cpu
, struct rq
*rq
)
4512 #endif /* CONFIG_SMP */
4515 * scheduler tick hitting a task of our scheduling class:
4517 static void task_tick_fair(struct rq
*rq
, struct task_struct
*curr
, int queued
)
4519 struct cfs_rq
*cfs_rq
;
4520 struct sched_entity
*se
= &curr
->se
;
4522 for_each_sched_entity(se
) {
4523 cfs_rq
= cfs_rq_of(se
);
4524 entity_tick(cfs_rq
, se
, queued
);
4529 * called on fork with the child task as argument from the parent's context
4530 * - child not yet on the tasklist
4531 * - preemption disabled
4533 static void task_fork_fair(struct task_struct
*p
)
4535 struct cfs_rq
*cfs_rq
= task_cfs_rq(current
);
4536 struct sched_entity
*se
= &p
->se
, *curr
= cfs_rq
->curr
;
4537 int this_cpu
= smp_processor_id();
4538 struct rq
*rq
= this_rq();
4539 unsigned long flags
;
4541 raw_spin_lock_irqsave(&rq
->lock
, flags
);
4543 update_rq_clock(rq
);
4545 if (unlikely(task_cpu(p
) != this_cpu
)) {
4547 __set_task_cpu(p
, this_cpu
);
4551 update_curr(cfs_rq
);
4554 se
->vruntime
= curr
->vruntime
;
4555 place_entity(cfs_rq
, se
, 1);
4557 if (sysctl_sched_child_runs_first
&& curr
&& entity_before(curr
, se
)) {
4559 * Upon rescheduling, sched_class::put_prev_task() will place
4560 * 'current' within the tree based on its new key value.
4562 swap(curr
->vruntime
, se
->vruntime
);
4563 resched_task(rq
->curr
);
4566 se
->vruntime
-= cfs_rq
->min_vruntime
;
4568 raw_spin_unlock_irqrestore(&rq
->lock
, flags
);
4572 * Priority of the task has changed. Check to see if we preempt
4576 prio_changed_fair(struct rq
*rq
, struct task_struct
*p
, int oldprio
)
4582 * Reschedule if we are currently running on this runqueue and
4583 * our priority decreased, or if we are not currently running on
4584 * this runqueue and our priority is higher than the current's
4586 if (rq
->curr
== p
) {
4587 if (p
->prio
> oldprio
)
4588 resched_task(rq
->curr
);
4590 check_preempt_curr(rq
, p
, 0);
4593 static void switched_from_fair(struct rq
*rq
, struct task_struct
*p
)
4595 struct sched_entity
*se
= &p
->se
;
4596 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4599 * Ensure the task's vruntime is normalized, so that when its
4600 * switched back to the fair class the enqueue_entity(.flags=0) will
4601 * do the right thing.
4603 * If it was on_rq, then the dequeue_entity(.flags=0) will already
4604 * have normalized the vruntime, if it was !on_rq, then only when
4605 * the task is sleeping will it still have non-normalized vruntime.
4607 if (!se
->on_rq
&& p
->state
!= TASK_RUNNING
) {
4609 * Fix up our vruntime so that the current sleep doesn't
4610 * cause 'unlimited' sleep bonus.
4612 place_entity(cfs_rq
, se
, 0);
4613 se
->vruntime
-= cfs_rq
->min_vruntime
;
4618 * We switched to the sched_fair class.
4620 static void switched_to_fair(struct rq
*rq
, struct task_struct
*p
)
4626 * We were most likely switched from sched_rt, so
4627 * kick off the schedule if running, otherwise just see
4628 * if we can still preempt the current task.
4631 resched_task(rq
->curr
);
4633 check_preempt_curr(rq
, p
, 0);
4636 /* Account for a task changing its policy or group.
4638 * This routine is mostly called to set cfs_rq->curr field when a task
4639 * migrates between groups/classes.
4641 static void set_curr_task_fair(struct rq
*rq
)
4643 struct sched_entity
*se
= &rq
->curr
->se
;
4645 for_each_sched_entity(se
) {
4646 struct cfs_rq
*cfs_rq
= cfs_rq_of(se
);
4648 set_next_entity(cfs_rq
, se
);
4649 /* ensure bandwidth has been allocated on our new cfs_rq */
4650 account_cfs_rq_runtime(cfs_rq
, 0);
4654 #ifdef CONFIG_FAIR_GROUP_SCHED
4655 static void task_move_group_fair(struct task_struct
*p
, int on_rq
)
4658 * If the task was not on the rq at the time of this cgroup movement
4659 * it must have been asleep, sleeping tasks keep their ->vruntime
4660 * absolute on their old rq until wakeup (needed for the fair sleeper
4661 * bonus in place_entity()).
4663 * If it was on the rq, we've just 'preempted' it, which does convert
4664 * ->vruntime to a relative base.
4666 * Make sure both cases convert their relative position when migrating
4667 * to another cgroup's rq. This does somewhat interfere with the
4668 * fair sleeper stuff for the first placement, but who cares.
4671 p
->se
.vruntime
-= cfs_rq_of(&p
->se
)->min_vruntime
;
4672 set_task_rq(p
, task_cpu(p
));
4674 p
->se
.vruntime
+= cfs_rq_of(&p
->se
)->min_vruntime
;
4678 static unsigned int get_rr_interval_fair(struct rq
*rq
, struct task_struct
*task
)
4680 struct sched_entity
*se
= &task
->se
;
4681 unsigned int rr_interval
= 0;
4684 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
4687 if (rq
->cfs
.load
.weight
)
4688 rr_interval
= NS_TO_JIFFIES(sched_slice(&rq
->cfs
, se
));
4694 * All the scheduling class methods:
4696 static const struct sched_class fair_sched_class
= {
4697 .next
= &idle_sched_class
,
4698 .enqueue_task
= enqueue_task_fair
,
4699 .dequeue_task
= dequeue_task_fair
,
4700 .yield_task
= yield_task_fair
,
4701 .yield_to_task
= yield_to_task_fair
,
4703 .check_preempt_curr
= check_preempt_wakeup
,
4705 .pick_next_task
= pick_next_task_fair
,
4706 .put_prev_task
= put_prev_task_fair
,
4709 .select_task_rq
= select_task_rq_fair
,
4711 .rq_online
= rq_online_fair
,
4712 .rq_offline
= rq_offline_fair
,
4714 .task_waking
= task_waking_fair
,
4717 .set_curr_task
= set_curr_task_fair
,
4718 .task_tick
= task_tick_fair
,
4719 .task_fork
= task_fork_fair
,
4721 .prio_changed
= prio_changed_fair
,
4722 .switched_from
= switched_from_fair
,
4723 .switched_to
= switched_to_fair
,
4725 .get_rr_interval
= get_rr_interval_fair
,
4727 #ifdef CONFIG_FAIR_GROUP_SCHED
4728 .task_move_group
= task_move_group_fair
,
4732 #ifdef CONFIG_SCHED_DEBUG
4733 static void print_cfs_stats(struct seq_file
*m
, int cpu
)
4735 struct cfs_rq
*cfs_rq
;
4738 for_each_leaf_cfs_rq(cpu_rq(cpu
), cfs_rq
)
4739 print_cfs_rq(m
, cpu
, cfs_rq
);