linux-kernel - Re: [PATCH v2] sched/fair: fix runnable

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Date:   Thu, 27 Feb 2020 11:17:46 -0800
From:   bsegall@...gle.com
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, linux-kernel@...r.kernel.org, pauld@...hat.com,
        parth@...ux.ibm.com, valentin.schneider@....com, hdanton@...a.com,
        zhout@...aldi.net
Subject: Re: [PATCH v2] sched/fair: fix runnable_avg for throttled cfs

Vincent Guittot <vincent.guittot@...aro.org> writes:

> When a cfs_rq is throttled, its group entity is dequeued and its running
> tasks are removed. We must update runnable_avg with the old h_nr_running
> and update group_se->runnable_weight with the new h_nr_running at each
> level of the hierarchy.

Looks good to me.

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

>
> Fixes: 9f68395333ad ("sched/pelt: Add a new runnable average signal")
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
> This patch applies on top of tip/sched/core
>
> Changes since v1:
> - update commit message
> - add missing {}
>
>  kernel/sched/fair.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fcc968669aea..22d067279269 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4701,8 +4701,13 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
>  		if (!se->on_rq)
>  			break;
>  
> -		if (dequeue)
> +		if (dequeue) {
>  			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
> +		} else {
> +			update_load_avg(qcfs_rq, se, 0);
> +			se_update_runnable(se);
> +		}
> +
>  		qcfs_rq->h_nr_running -= task_delta;
>  		qcfs_rq->idle_h_nr_running -= idle_task_delta;
>  
> @@ -4770,8 +4775,13 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
>  			enqueue = 0;
>  
>  		cfs_rq = cfs_rq_of(se);
> -		if (enqueue)
> +		if (enqueue) {
>  			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
> +		} else {
> +			update_load_avg(cfs_rq, se, 0);
> +			se_update_runnable(se);
> +		}
> +
>  		cfs_rq->h_nr_running += task_delta;
>  		cfs_rq->idle_h_nr_running += idle_task_delta;