linux-kernel - Re: [PATCH v4 2/2] sched/fair: update scale invariance of PELT

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Message-ID: <20181023100057.GJ3109@worktop.c.hoisthospitality.com>
Date:   Tue, 23 Oct 2018 12:00:57 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        dietmar.eggemann@....com, Morten.Rasmussen@....com,
        patrick.bellasi@....com, pjt@...gle.com, bsegall@...gle.com,
        thara.gopinath@...aro.org
Subject: Re: [PATCH v4 2/2] sched/fair: update scale invariance of PELT

On Fri, Oct 19, 2018 at 06:17:51PM +0200, Vincent Guittot wrote:
> In order to achieve this time scaling, a new clock_pelt is created per rq.


> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 3990818..d987f50 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -848,6 +848,8 @@ struct rq {
>  	unsigned int		clock_update_flags;
>  	u64			clock;
>  	u64			clock_task;
> +	u64			clock_pelt;
> +	unsigned long		lost_idle_time;

Very clever that. Seems to work out nicely. We should maybe look at
ensuring all these clock fields are indeed on the same cacheline.