linux-kernel - Re: [PATCH 0/4 v4] sched/rt: track rt rq utilization

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Date:   Sat, 14 Apr 2018 13:42:04 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, rjw@...ysocki.net,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        viresh kumar <viresh.kumar@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>
Subject: Re: [PATCH 0/4 v4] sched/rt: track rt rq utilization

On 14 April 2018 at 12:07, Peter Zijlstra <peterz@...radead.org> wrote:
>
>
> What I don't see in this patch-set is removal of the current rt_avg
> stuff.

This RT load tracking doesn't replace current rt_avg because they are
not using same period and providing same function
current rt_avg uses sysctl_sched_time_avg to define the averaging
period and it's default period is 1 second. But PELT uses a fixed
period
current rt_avg is tracking irq accounting which this patch doesn't do.
This is probably doable but will need more complex changes

Replacing current rt_avg by this new RT utilization tracking would
require more complex changes so I didn't want to add them this 1st
step.

>
> And I didn't look closely enough; but are the root cfs and rt pelt
> windows aligned? They really should be; otherwise you can't combine them
> sanely.

No They are not aligned.
I agree that this could generate some variation on the sum. I'm going
to fix this point