linux-kernel - Re: [PATCH 00/14] Modularize schedutil

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Message-ID: <20200508131508.GB10541@google.com>
Date:   Fri, 8 May 2020 14:15:08 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, sudeep.holla@....com, gregkh@...uxfoundation.org,
        rafael@...nel.org, viresh.kumar@...aro.org, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, mcgrof@...nel.org, keescook@...omium.org,
        yzaikin@...gle.com, fweisbec@...il.com, tkjos@...gle.com,
        kernel-team@...roid.com, Ionela Voinescu <ionela.voinescu@....com>
Subject: Re: [PATCH 00/14] Modularize schedutil

Hey Valentin,

On Thursday 07 May 2020 at 22:34:17 (+0100), Valentin Schneider wrote:
> I'm curious; why would some Android device not want to roll with schedutil?
> 
> When it comes to dynamic policies (i.e. forget performance / powersave, and
> put userspace in a corner), I'd be willing to take a stand and say you
> should only really be using schedutil nowadays - alignment with the
> scheduler, uclamp, yadda yadda.
> 
> AFAIA the only schedutil-related quirk we oughta fix for arm/arm64 is that
> arch_scale_freq_invariant() thingie, and FWIW I'm hoping to get something
> regarding this out sometime soonish. After that, I'd actually want to make
> schedutil the default governor for arm/arm64.

As in setting CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL=y in the arm64
defconfig? If so, you have my Acked-by already :)

> I'm not opiniated on the modularization, but if you can, could you please
> share some more details as to why schedutil cannot fulfill its role of holy
> messiah of governors for GKI?

I guess I answered some of that in the other thread with Peter, but all
in all I'm definitely not trying to make an argument that schedutil
isn't good enough here. I'm trying to say that mandating it in *GKI* is
just likely to cause unnecessary friction, and trust me there is already
enough of that with other topics. Giving the option of having sugov as a
module doesn't prevent us from making it a default for a few arches, so
I think there is ground for an agreement!

Cheers,
Quentin