linux-kernel - Re: [PATCH] sched/pelt: simplify load_sum assignment code in attach_entity_load

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Message-ID: <CAKfTPtCgbtKkjA+tU2DFJgKAsXV+kFKipMxTuReaT5QKNvvAGA@mail.gmail.com>
Date:   Wed, 22 Jun 2022 17:20:18 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Zhaoyu Liu <zackary.liu.pro@...il.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,
        kuyo.chang@...iatek.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/pelt: simplify load_sum assignment code in attach_entity_load_avg()

On Tue, 21 Jun 2022 at 17:45, Zhaoyu Liu <zackary.liu.pro@...il.com> wrote:
>
> In commit 40f5aa4c5eae ("sched/pelt: Fix attach_entity_load_avg() corner case"),
> these code was committed:
>         if (se_weight(se) < se->avg.load_sum)
>                 se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
>         else
>                 se->avg.load_sum = 1;
>
> they could be replace with:
>         se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se)) ?: 1;
>
> to make the code cleaner.

This quite subjective as I consider current version cleaner than your proposal

>
> Signed-off-by: Zhaoyu Liu <zackary.liu.pro@...il.com>
> ---
>  kernel/sched/fair.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 78795a997d9c..ed32f66bbd3d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3881,10 +3881,7 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
>         se->avg.runnable_sum = se->avg.runnable_avg * divider;
>
>         se->avg.load_sum = se->avg.load_avg * divider;
> -       if (se_weight(se) < se->avg.load_sum)
> -               se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se));
> -       else
> -               se->avg.load_sum = 1;
> +       se->avg.load_sum = div_u64(se->avg.load_sum, se_weight(se)) ?: 1;
>
>         enqueue_load_avg(cfs_rq, se);
>         cfs_rq->avg.util_avg += se->avg.util_avg;
> --
> 2.17.1
>