linux-kernel - Re: [PATCH v4] sched/fair: Correctly insert cfs

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Message-ID: <YL+dTtsCtZjMeZWn@blackbook>
Date:   Tue, 8 Jun 2021 18:39:42 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Odin Ugedal <odin@...d.al>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Giovanni Gherdovich <ggherdovich@...e.cz>
Subject: Re: [PATCH v4] sched/fair: Correctly insert cfs_rq's to list on
 unthrottle

Hello.

On Fri, Jun 04, 2021 at 12:23:14PM +0200, Odin Ugedal <odin@...d.al> wrote:

> @@ -4719,8 +4738,8 @@ static int tg_unthrottle_up(struct task_group *tg, void *data)
>  		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
>  					     cfs_rq->throttled_clock_task;
>  
> -		/* Add cfs_rq with already running entity in the list */
> -		if (cfs_rq->nr_running >= 1)
> +		/* 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)
>  			list_add_leaf_cfs_rq(cfs_rq);
>  	}

Can there be a decayed cfs_rq with positive nr_running?
I.e. can the condition be simplified to just the decayed check?

(I'm looking at account_entity_enqueue() but I don't know if an entity's
weight can be zero in some singular cases.)

Thanks,
Michal

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