Re: [PATCH v4] sched/fair: Correctly insert cfs_rq's to list on unthrottle

From: "Michal Koutný" <mkoutny@suse.com>
To: Odin Ugedal <odin@uged.al>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	Giovanni Gherdovich <ggherdovich@suse.cz>
Subject: Re: [PATCH v4] sched/fair: Correctly insert cfs_rq's to list on unthrottle
Date: Tue, 8 Jun 2021 18:39:42 +0200	[thread overview]
Message-ID: <YL+dTtsCtZjMeZWn@blackbook> (raw)
In-Reply-To: <20210604102314.697749-1-odin@uged.al>

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Hello.

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