linux-kernel - Re: [PATCH v3] sched/fair: simplfy the work when reweighting entity

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Message-ID: <CAKfTPtBReSax0AK9sanzcSzBMJzx7jK-K8Umc3kfH_n11N7f3A@mail.gmail.com>
Date:   Tue, 18 Aug 2020 11:07:37 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Jiang Biao <benbjiang@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jiang Biao <benbjiang@...cent.com>
Subject: Re: [PATCH v3] sched/fair: simplfy the work when reweighting entity

On Tue, 11 Aug 2020 at 13:32, Jiang Biao <benbjiang@...il.com> wrote:
>
> From: Jiang Biao <benbjiang@...cent.com>
>
> 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 <benbjiang@...cent.com>

Minor typo of the subject: s/simplfy/simplify/

Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>

> ---
> v3<-v2: Amend commit log taking Dietmar's advice. Thx.
> 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);
>
>  }
>
> --
> 2.21.0
>