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From:   Joel Fernandes <joelaf@google.com>
Date:   Tue, 12 May 2020 11:49:32 -0400
Message-ID: <CAJWu+oqVc16B8nf-317Yyf9befPsjBohfG=GOdoBZyuVz==bmQ@mail.gmail.com>
Subject: Re: [PATCH 00/14] Modularize schedutil
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Quentin Perret <qperret@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Benjamin Segall <bsegall@google.com>,
        Mel Gorman <mgorman@suse.de>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Todd Kjos <tkjos@google.com>,
        "Cc: Android Kernel" <kernel-team@android.com>
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On Tue, May 12, 2020 at 11:30 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
[...]
> > The end goal with GKI is the following: Google will release a single
> > binary kernel image (signed, etc etc) that all devices using a given
> > Android version will be required to use. That image is however going to
> > be only for the core of the kernel (no drivers or anything of the sort).
> > Vendors and OEMs, on their end, will be responsible to build and ship
> > GKI-compatible modules for their respective devices. So, Android devices
> > will eventually ship with a Google-issued GKI, plus a bunch of
> > vendor-provided modules loaded during boot.
>
> If that is the case, then I absolutely think that schedutil should be
> part of the GKI.
>
> Moreover, that would have been my opinion even if it had been modular
> in the first place.
>
> > This is a significant shift from the current model where vendors
> > completely own the kernel, and are largely free to use the kernel config
> > they want. Today, those who don't use schedutil are free to turn the
> > config off, for example.
>
> So why is this regarded as a good thing?
>
> > But GKI changes that. The 'core' GKI config is effectively imposed to
> > the entire ecosystem. As of now, because it is 'bool' we have no choice
> > but to compile schedutil in the core GKI as some (most) partners use it.
> > But as you can imagine, that is not the preferred option of those who
> > _don't_ use schedutil.
>
> OTOH, it may as well be an incentive for them to switch over and
> report problems with it that they see.
>
> I absolutely would like to make schedutil the clearly preferred option
> and IMO avoiding to use it, especially for non-technical reasons,
> should be clearly less attractive.

Also, does this series make it easier for vendors / oems / whoever to
carry out-of-tree schedutil hacks saying that's "Ok" because that's
not part of the core GKI? That would definitely be a bad thing to
encourage as well. schedutil should pretty much be considered a part
of the core GKI if the goal is to encourage everyone to move to it,
IMO.

- Joel