linux-kernel - Re: [PATCH] sched/fair: update comments in enqueue/dequeue

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Message-ID: <CAKfTPtAa9efmNq29KJgV46c-ncN866UViHuhJMdUrQYyhiNtzw@mail.gmail.com>
Date:   Fri, 3 Jun 2022 14:08:32 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: update comments in enqueue/dequeue_entity()

On Wed, 1 Jun 2022 at 05:55, Chengming Zhou <zhouchengming@...edance.com> wrote:
>
> When reading the sched_avg related code, I found the comments in
> enqueue/dequeue_entity() are not updated with the current code.
>
> We don't add/subtract entity's runnable_avg from cfs_rq->runnable_avg
> during enqueue/dequeue_entity(), those are done only for attach/detach.
>
> This patch updates the comments to reflect the current code working.
>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>

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

> ---
>  kernel/sched/fair.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index b3371fa40548..e0cd4052e32f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4348,7 +4348,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
>         /*
>          * When enqueuing a sched_entity, we must:
>          *   - Update loads to have both entity and cfs_rq synced with now.
> -        *   - Add its load to cfs_rq->runnable_avg
> +        *   - For group_entity, update its runnable_weight to reflect the new
> +        *     h_nr_running of its group cfs_rq.
>          *   - For group_entity, update its weight to reflect the new share of
>          *     its group cfs_rq
>          *   - Add its new weight to cfs_rq->load.weight
> @@ -4433,7 +4434,8 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
>         /*
>          * When dequeuing a sched_entity, we must:
>          *   - Update loads to have both entity and cfs_rq synced with now.
> -        *   - Subtract its load from the cfs_rq->runnable_avg.
> +        *   - For group_entity, update its runnable_weight to reflect the new
> +        *     h_nr_running of its group cfs_rq.
>          *   - Subtract its previous weight from cfs_rq->load.weight.
>          *   - For group entity, update its weight to reflect the new share
>          *     of its group cfs_rq.
> --
> 2.36.1
>