On 06/08/2020 18:14, Jiang Biao wrote: > From: Jiang Biao <[email protected]> > > 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. 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. > > Signed-off-by: Jiang Biao <[email protected]> > --- > 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); > > }
