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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 28 Sep 2022 20:54:38 +0200
Message-ID: <CAJZ5v0g8=mqiBC9LwQYOw15UZujaV8XoWoor8z=H+nG_aFc_3g@mail.gmail.com>
Subject: Re: [RFC PATCH 0/1] cpuidle: teo: Introduce optional util-awareness
To:     Kajetan Puchalski <kajetan.puchalski@arm.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Lukasz Luba <lukasz.luba@arm.com>,
        Dietmar Eggemann <Dietmar.Eggemann@arm.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi,

On Wed, Sep 28, 2022 at 2:42 PM Kajetan Puchalski
<kajetan.puchalski@arm.com> wrote:
>
> Hi Rafael,
>
> Just a gentle ping here. Could you please take a look at this
> discussion?

I have seen it, but I haven't thought it through yet.

Overall, this is quite subtle and requires quite a bit of consideration IMV.

> I'd like to address some comments I received, especially on the subject
> of making it reduce the state by one as opposed to going all the way to
> 0 to account for different hardware and how we can accomodate different
> architectures in the implementation of that mechanism.

I need to think more about that.

> Before I send a v2 it'd be great to know your opinions on this and
> whether I should still send it as a TEO patch or fork it into a separate
> governor and make the changes there as both Doug and I seem to prefer.

Well, it is not a super-large patch against TEO, so I'm not sure if
adding a new governor just for this one bit is a good idea.

I surely don't like the #ifdeffery there, so if it can be made part of
the default TEO behavior, it will be much more appealing to me.

Thanks!

> On Thu, Sep 15, 2022 at 05:44:10PM +0100, Kajetan Puchalski wrote:
> > At the very least this approach seems promising so I wanted to discuss it in RFC form first.
> > Thank you for taking your time to read this!
> >
> > [1] https://github.com/mrkajetanp/lisa-notebooks/blob/a2361a5b647629bfbfc676b942c8e6498fb9bd03/idle_util_aware.pdf
> >
> > Kajetan Puchalski (1):
> >   cpuidle: teo: Introduce optional util-awareness
> >
> >  drivers/cpuidle/Kconfig         | 12 +++++
> >  drivers/cpuidle/governors/teo.c | 86 +++++++++++++++++++++++++++++++++
> >  2 files changed, 98 insertions(+)
> >
> > --
> > 2.37.1
> >