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

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Message-ID: <20200508112609.GA5298@hirez.programming.kicks-ass.net>
Date:   Fri, 8 May 2020 13:26:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Quentin Perret <qperret@...gle.com>, 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,
        rafael@...nel.org, viresh.kumar@...aro.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
Subject: Re: [PATCH 00/14] Modularize schedutil

On Fri, May 08, 2020 at 12:37:21PM +0200, Greg KH wrote:
> On Fri, May 08, 2020 at 10:11:28AM +0200, Peter Zijlstra wrote:
> > On Thu, May 07, 2020 at 07:09:58PM +0100, Quentin Perret wrote:
> > > One challenge to implement GKI is to avoid bloating the kernel by
> > > compiling too many things in, especially given that different devices
> > > need different things. As such, anything that can be turned into a
> > > module helps GKI, by offering an alternative to having that component
> > > built-in. This is true for pretty much anything that can be made
> > > modular, including drivers as well as other kernel components, such as
> > > CPUFreq governors.
> > 
> > The idea is to move to 1 governor, schedutil. Also, I abhor all the
> > exports this thing does. Modules have no business touching most of that.
> > 
> > Look at every EXPORT you do and wonder ask yourself how you can abuse
> > it. Modules are not a good thing, they're horrible pieces of crap.
> 
> Quentin, what is missing from schedutil that warrants the need for a
> totally different governor?  Is there specific problems with the
> existing ones or is this just an instance of "we wrote our own a long
> time ago and never pushed it upstream" from various SoC companies?

At the very least there's that interactive governor that's really
popular with Android. But IIRC there's a whole scala of home-brew
governors and tweaks out there.

And instead of enabling that crap, we should be discouraging it.
Consolidate and kill the governor interface.