linux-kernel - Re: [PATCH 2/2] sched/fair: Delete useless condition in tg_unthrottle

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Message-ID: <xm26pmlsvcah.fsf@bsegall-linux.svl.corp.google.com>
Date:   Thu, 07 Apr 2022 14:00:54 -0700
From:   Benjamin Segall <bsegall@...gle.com>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, mgorman@...e.de, bristot@...hat.com,
        linux-kernel@...r.kernel.org, duanxiongchun@...edance.com,
        songmuchun@...edance.com
Subject: Re: [PATCH 2/2] sched/fair: Delete useless condition in
 tg_unthrottle_up()

Chengming Zhou <zhouchengming@...edance.com> writes:

> Fully decayed cfs_rq is impossible to have queued entities,
> the first condition "!cfs_rq_is_decayed(cfs_rq)" is enough
> to cover.

In particular, cfs_rq->load.weight is part of cfs_rq_is_decayed.

Reviewed-by: Ben Segall <bsegall@...gle.com>

>
> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
> ---
>  kernel/sched/fair.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e6fa5d1141b4..17c13c38b1c2 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4850,7 +4850,7 @@ static int tg_unthrottle_up(struct task_group *tg, void *data)
>  					     cfs_rq->throttled_clock_task;
>  
>  		/* Add cfs_rq with load or one or more already running entities to the list */
> -		if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
> +		if (!cfs_rq_is_decayed(cfs_rq))
>  			list_add_leaf_cfs_rq(cfs_rq);
>  	}