Hi, > On Aug 11, 2020, at 5:50 PM, Dietmar Eggemann <dietmar.eggem...@arm.com> > wrote: > > On 06/08/2020 18:14, Jiang Biao wrote: >> From: Jiang Biao <benbji...@tencent.com> >> >> If a se is on_rq when reweighting entity, all we need should be >> updating the load of cfs_rq, other dequeue/enqueue work could be >> redundant, such as, >> * nr_running--/nr_running++ >> >> Even though the following dequeue/enqueue path would never be reached >> * account_numa_dequeue/account_numa_enqueue >> * list_del/list_add from/into cfs_tasks >> but it could be a little confusing. >> >> Simplifying the logic could be helpful to reduce a litte overhead for >> hot path, and make it cleaner and more readable. > > LGTM. I guess you have to resend it w/o the RFC tag. Will do soon. > > Maybe you can rework the patch header a little? > > Something like this: > > The code in reweight_entity() can be simplified. > > For a sched entity on the rq, the entity accounting can be replaced by > cfs_rq instantaneous load updates currently called from within the > entity accounting. > > Even though an entity on the rq can't represent a task in > reweight_entity() (a task is always dequeued before calling this > function) and so the numa task accounting and the rq->cfs_tasks list > management of the entity accounting are never called, the redundant > cfs_rq->nr_running decrement/increment will be avoided. That’s a much better. I’ll pick the header if you don’t mind. :)
Thanks a lot for your kindly reply and detailed explanation. Regards, Jiang > >> >> Signed-off-by: Jiang Biao <benbji...@tencent.com> >> --- >> v2<-v1: >> - Amend the commit log. >> >> 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); >> >> }
