Messages in this thread Patch in this message | | | From | Chengming Zhou <> | Subject | [PATCH 7/8] sched/fair: delete superfluous set_task_rq_fair() | Date | Sat, 9 Jul 2022 23:13:52 +0800 |
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set_task_rq() is used when move task across CPUs/groups to change its cfs_rq and parent entity, and it will call set_task_rq_fair() to sync blocked task load_avg just before change its cfs_rq.
1. task migrate CPU: will detach/remove from prev cfs_rq and reset its sched_avg last_update_time to 0, so don't need to sync again.
2. task migrate cgroup: will detach from prev cfs_rq and reset its sched_avg last_update_time to 0, so don't need to sync too.
3. !fair task migrate CPU/cgroup: we stop load tracking for !fair task, reset sched_avg last_update_time to 0 when switched_from_fair(), so don't need it too.
So set_task_rq_fair() is not needed anymore, this patch delete it.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> --- kernel/sched/fair.c | 31 ------------------------------- kernel/sched/sched.h | 8 -------- 2 files changed, 39 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ca714eedeec5..b0bde895ba96 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3430,37 +3430,6 @@ static inline void update_tg_load_avg(struct cfs_rq *cfs_rq) } } -/* - * Called within set_task_rq() right before setting a task's CPU. The - * caller only guarantees p->pi_lock is held; no other assumptions, - * including the state of rq->lock, should be made. - */ -void set_task_rq_fair(struct sched_entity *se, - struct cfs_rq *prev, struct cfs_rq *next) -{ - u64 p_last_update_time; - u64 n_last_update_time; - - if (!sched_feat(ATTACH_AGE_LOAD)) - return; - - /* - * We are supposed to update the task to "current" time, then its up to - * date and ready to go to new CPU/cfs_rq. But we have difficulty in - * getting what current time is, so simply throw away the out-of-date - * time. This will result in the wakee task is less decayed, but giving - * the wakee more load sounds not bad. - */ - if (!(se->avg.last_update_time && prev)) - return; - - p_last_update_time = cfs_rq_last_update_time(prev); - n_last_update_time = cfs_rq_last_update_time(next); - - __update_load_avg_blocked_se(p_last_update_time, se); - se->avg.last_update_time = n_last_update_time; -} - /* * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to * propagate its contribution. The key to this propagation is the invariant diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 19e0076e4245..a8ec7af4bd51 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -505,13 +505,6 @@ extern int sched_group_set_shares(struct task_group *tg, unsigned long shares); extern int sched_group_set_idle(struct task_group *tg, long idle); -#ifdef CONFIG_SMP -extern void set_task_rq_fair(struct sched_entity *se, - struct cfs_rq *prev, struct cfs_rq *next); -#else /* !CONFIG_SMP */ -static inline void set_task_rq_fair(struct sched_entity *se, - struct cfs_rq *prev, struct cfs_rq *next) { } -#endif /* CONFIG_SMP */ #endif /* CONFIG_FAIR_GROUP_SCHED */ #else /* CONFIG_CGROUP_SCHED */ @@ -1937,7 +1930,6 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu) #endif #ifdef CONFIG_FAIR_GROUP_SCHED - set_task_rq_fair(&p->se, p->se.cfs_rq, tg->cfs_rq[cpu]); p->se.cfs_rq = tg->cfs_rq[cpu]; p->se.parent = tg->se[cpu]; p->se.depth = tg->se[cpu] ? tg->se[cpu]->depth + 1 : 0; -- 2.36.1
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