linux-kernel - Re: [PATCH v2 1/2] sched/fair: Fix task utilization accountability in compute

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Date:   Thu, 25 Feb 2021 11:58:27 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     vincent.donnefort@....com, peterz@...radead.org, mingo@...hat.com,
        vincent.guittot@...aro.org, linux-kernel@...r.kernel.org,
        patrick.bellasi@...bug.net, valentin.schneider@....com
Subject: Re: [PATCH v2 1/2] sched/fair: Fix task utilization accountability
 in compute_energy()

On Thursday 25 Feb 2021 at 12:45:06 (+0100), Dietmar Eggemann wrote:
> I.e. since _task_util_est is always >= task_util during wakeup, cpu_util
> must be > cpu_util_est (by more than _task_util_est - task_util).
> 
> I can see it for a CPU whose cpu_util has a fair amount of contributions
> from blocked tasks which cpu_util_est wouldn't have.

Yes I think this can manifest itself if there are tasks changing
behaviour, or on an idle CPU as its ue.enqueued will be 0 and we'll be
left with blocked util only.

Thanks,
Quentin