> On Aug 6, 2020, at 12:21 AM, Dietmar Eggemann <dietmar.eggem...@arm.com> > wrote: > > On 04/08/2020 09:12, Jiang Biao wrote: >> If a se is on_rq when reweighting entity, all we need should be >> updating the load of cfs_rq, other dequeue/enqueue works could be >> redundant, such as, >> * account_numa_dequeue/account_numa_enqueue >> * list_del/list_add from/into cfs_tasks >> * nr_running--/nr_running++ > > I think this could make sense. Have you spotted a code path where this > gives you a change? > > I guess only for a task on the rq, so: entity_is_task(se) && se->on_rq Yes, you're right. No other code path I spotted except what you list below.
> >> Just simplfy the work. Could be helpful for the hot path. > > IMHO hotpath is update_cfs_group() -> reweight_entity() but this is only > called for '!entity_is_task(se)'. > > See > > 3290 if (!gcfs_rq) > 3291 return; > > in update_cfs_group(). Yes, It is. But *nr_running--/nr_running++* works are still redundant for ‘!entity_is_task(se)' hot path. :) Besides, I guess we could simplify the logic and make it cleaner and more readable with this patch. If it could make sense to you, would you mind if I resend the patch with the commit log amended? > > The 'entity_is_task(se)' case is > > set_load_weight(struct task_struct *p, ...) -> reweight_task(p, ...) -> > reweight_entity(..., &p->se, ...) > > but here !se->on_rq. Yes, indeed. Thanks a lot for your comments. Regards, Jiang > >> Signed-off-by: Jiang Biao <benbji...@tencent.com> >> --- >> kernel/sched/fair.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 04fa8dbcfa4d..18a8fc7bd0de 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3086,7 +3086,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, >> struct sched_entity *se, >> /* commit outstanding execution time */ >> if (cfs_rq->curr == se) >> update_curr(cfs_rq); >> - account_entity_dequeue(cfs_rq, se); >> + update_load_sub(&cfs_rq->load, se->load.weight); >> } >> dequeue_load_avg(cfs_rq, se); >> >> @@ -3102,7 +3102,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, >> struct sched_entity *se, >> >> enqueue_load_avg(cfs_rq, se); >> if (se->on_rq) >> - account_entity_enqueue(cfs_rq, se); >> + update_load_add(&cfs_rq->load, se->load.weight); >> >> } >
