linux-kernel - Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes

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Message-ID: <20161019113329.GM3102@twins.programming.kicks-ass.net>
Date:   Wed, 19 Oct 2016 13:33:29 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Joseph Salisbury <joseph.salisbury@...onical.com>,
        Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Mike Galbraith <efault@....de>, omer.akram@...onical.com
Subject: Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes

On Tue, Oct 18, 2016 at 01:56:51PM +0200, Vincent Guittot wrote:

> ---
>  kernel/sched/fair.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 8b03fb5..89776ac 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -690,7 +690,14 @@ void init_entity_runnable_average(struct sched_entity *se)
>  	 * will definitely be update (after enqueue).
>  	 */
>  	sa->period_contrib = 1023;
> -	sa->load_avg = scale_load_down(se->load.weight);
> +	/*
> +	 * Tasks are intialized with full load to be seen as heavy task until
> +	 * they get a chance to stabilize to their real load level.
> +	 * group entity are intialized with null load to reflect the fact that
> +	 * nothing has been attached yet to the task group.
> +	 */
> +	if (entity_is_task(se))
> +		sa->load_avg = scale_load_down(se->load.weight);
>  	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
>  	/*
>  	 * At this point, util_avg won't be used in select_task_rq_fair anyway
> 

Vince, could you post a proper version of this patch with changelogs and
tags so that we can get that merged into Linus' tree and stable for 4.8?