linux-kernel - Re: [PATCH 3/3] sched/fair: Consider uclamp for "task fits capacity" checks

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Message-ID: <20191126100638.pbcxnii67fihkb3g@e107158-lin.cambridge.arm.com>
Date:   Tue, 26 Nov 2019 10:06:38 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, patrick.bellasi@...bug.net,
        qperret@...gle.com, morten.rasmussen@....com
Subject: Re: [PATCH 3/3] sched/fair: Consider uclamp for "task fits capacity"
 checks

On 11/25/19 17:33, Valentin Schneider wrote:
> With cgroups, I do recall something about allowing the cgroup *knobs* to be
> inverted, but AFAICT that gets sanitized when it trickles down to the
> scheduler via cpu_util_update_eff():
> 
>     eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);

I missed that we cap here too.

> 
> So I don't see how inversion could happen within uclamp_task_util().
> Patrick, any chance you could light up my torch?

I think I am equally confused now. A clarification that can help improving the
comment would be useful.

Thanks

--
Qais Yousef