The following commit has been merged into the sched/core branch of tip:
Commit-ID: e1f078f50478a51849453341e7356cb298df00cf
Gitweb: https://git.kernel.org/tip/e1f078f50478a51849453341e7356cb298df00cf
Author: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
AuthorDate: Thu, 18 Aug 2022 20:48:01 +08:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 23 Aug 2022 11:01:18 +02:00
sched/fair: Combine detach into dequeue when migrating task
When we are migrating task out of the CPU, we can combine detach and
propagation into dequeue_entity() to save the detach_entity_cfs_rq()
in migrate_task_rq_fair().
This optimization is like combining DO_ATTACH in the enqueue_entity()
when migrating task to the CPU. So we don't have to traverse the CFS tree
extra time to do the detach_entity_cfs_rq() -> propagate_entity_cfs_rq(),
which wouldn't be called anymore with this patch's change.
detach_task()
deactivate_task()
dequeue_task_fair()
for_each_sched_entity(se)
dequeue_entity()
update_load_avg() /* (1) */
detach_entity_load_avg()
set_task_cpu()
migrate_task_rq_fair()
detach_entity_cfs_rq() /* (2) */
update_load_avg();
detach_entity_load_avg();
propagate_entity_cfs_rq();
for_each_sched_entity()
update_load_avg()
This patch save the detach_entity_cfs_rq() called in (2) by doing
the detach_entity_load_avg() for a CPU migrating task inside (1)
(the task being the first se in the loop)
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220818124805.601-6-zhouchengming@xxxxxxxxxxxxx
---
kernel/sched/fair.c | 28 ++++++++++++++++------------
1 file changed, 16 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 52de830..f52e7dc 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4003,6 +4003,7 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
#define UPDATE_TG 0x1
#define SKIP_AGE_LOAD 0x2
#define DO_ATTACH 0x4
+#define DO_DETACH 0x8
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
@@ -4032,6 +4033,13 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
attach_entity_load_avg(cfs_rq, se);
update_tg_load_avg(cfs_rq);
+ } else if (flags & DO_DETACH) {
+ /*
+ * DO_DETACH means we're here from dequeue_entity()
+ * and we are migrating task out of the CPU.
+ */
+ detach_entity_load_avg(cfs_rq, se);
+ update_tg_load_avg(cfs_rq);
} else if (decayed) {
cfs_rq_util_change(cfs_rq, 0);
@@ -4292,6 +4300,7 @@ static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
#define UPDATE_TG 0x0
#define SKIP_AGE_LOAD 0x0
#define DO_ATTACH 0x0
+#define DO_DETACH 0x0
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
{
@@ -4512,6 +4521,11 @@ static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
+ int action = UPDATE_TG;
+
+ if (entity_is_task(se) && task_on_rq_migrating(task_of(se)))
+ action |= DO_DETACH;
+
/*
* Update run-time statistics of the 'current'.
*/
@@ -4526,7 +4540,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
* - For group entity, update its weight to reflect the new share
* of its group cfs_rq.
*/
- update_load_avg(cfs_rq, se, UPDATE_TG);
+ update_load_avg(cfs_rq, se, action);
se_update_runnable(se);
update_stats_dequeue_fair(cfs_rq, se, flags);
@@ -7078,8 +7092,6 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
return new_cpu;
}
-static void detach_entity_cfs_rq(struct sched_entity *se);
-
/*
* Called immediately before a task is migrated to a new CPU; task_cpu(p) and
* cfs_rq_of(p) references at time of call are still valid and identify the
@@ -7101,15 +7113,7 @@ static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
se->vruntime -= u64_u32_load(cfs_rq->min_vruntime);
}
- if (p->on_rq == TASK_ON_RQ_MIGRATING) {
- /*
- * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
- * rq->lock and can modify state directly.
- */
- lockdep_assert_rq_held(task_rq(p));
- detach_entity_cfs_rq(se);
-
- } else {
+ if (!task_on_rq_migrating(p)) {
remove_entity_load_avg(se);
/*
|