linux-kernel - Re: [RFC PATCH v4 0/2] cpuidle: teo: Introduce util-awareness

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Date:   Mon, 21 Nov 2022 13:50:34 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Kajetan Puchalski <kajetan.puchalski@....com>
Cc:     rafael@...nel.org, daniel.lezcano@...aro.org, lukasz.luba@....com,
        Dietmar.Eggemann@....com, dsmythies@...us.net,
        yu.chen.surf@...il.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v4 0/2] cpuidle: teo: Introduce util-awareness

On Mon, Nov 21, 2022 at 1:23 PM Kajetan Puchalski
<kajetan.puchalski@....com> wrote:
>
> Hi Rafael,
>
> On Wed, Nov 02, 2022 at 03:28:06PM +0000, Kajetan Puchalski wrote:
>
> [...]
>
> > v3 -> v4:
> > - remove the chunk of code skipping metrics updates when the CPU was utilized
> > - include new test results and more benchmarks in the cover letter
>
> [...]
>
> It's been some time so I just wanted to bump this, what do you think
> about this v4? Doug has already tested it, resuls for his machine are
> attached to the v3 thread.

I have some comments, but it's being pushed down by more urgent things, sorry.

First off, I think that the information from your cover letter should
go into the patch changelog (at least the majority of it), as it's
relevant for the motivation part.

Also I think that this optimization is really trading energy for
performance and that should be emphasized.  IOW, it is not about
improving the prediction accuracy (which is what the cover letter and
changelog seem to be claiming), but about reducing the expected CPU
wakeup latency in some cases.

I'll send more comments later today if I have the time or later this
week otherwise.