linux-kernel - Re: [PATCH 1/4 v4] sched/pelt: Move pelt related code in a dedicated file

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Message-ID: <95f22502-16e6-555c-fb61-e1a9e88f1163@arm.com>
Date:   Sun, 15 Apr 2018 13:58:13 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>, peterz@...radead.org,
        mingo@...nel.org, linux-kernel@...r.kernel.org, rjw@...ysocki.net
Cc:     juri.lelli@...hat.com, Morten.Rasmussen@....com,
        viresh.kumar@...aro.org, valentin.schneider@....com
Subject: Re: [PATCH 1/4 v4] sched/pelt: Move pelt related code in a dedicated
 file

On 03/16/2018 12:25 PM, Vincent Guittot wrote:
> We want to track rt_rq's utilization as a part of the estimation of the
> whole rq's utilization. This is necessary because rt tasks can steal
> utilization to cfs tasks and make them lighter than they are.
> As we want to use the same load tracking mecanism for both and prevent
> useless dependency between cfs and rt code, pelt code is moved in a
> dedicated file.

This would mean that we introduce function calls into the cfs scheduler 
fast-path, something we avoided so far (e.g. the cpu and frequency 
invariance hooks). Are we OK with that?

Quentin mentioned this already during v3 review back in December.

[...]