linux-kernel - Re: [RFC PATCH 2/2] cpufreq/schedutil: Remove iowait boost

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Date: Mon, 18 Mar 2024 18:08:44 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Christian Loehle <christian.loehle@....com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org, peterz@...radead.org, 
	juri.lelli@...hat.com, mingo@...hat.com, dietmar.eggemann@....com, 
	vschneid@...hat.com, vincent.guittot@...aro.org, Johannes.Thumshirn@....com, 
	adrian.hunter@...el.com, ulf.hansson@...aro.org, andres@...razel.de, 
	asml.silence@...il.com, linux-pm@...r.kernel.org, linux-block@...r.kernel.org, 
	io-uring@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] cpufreq/schedutil: Remove iowait boost

On Mon, Mar 18, 2024 at 5:40 PM Christian Loehle
<christian.loehle@....com> wrote:
>
> On 18/03/2024 14:07, Rafael J. Wysocki wrote:
> > On Mon, Mar 4, 2024 at 9:17 PM Christian Loehle
> > <christian.loehle@....com> wrote:
> >>
> >> The previous commit provides a new cpu_util_cfs_boost_io interface for
> >> schedutil which uses the io boosted utilization of the per-task
> >> tracking strategy. Schedutil iowait boosting is therefore no longer
> >> necessary so remove it.
> >
> > I'm wondering about the cases when schedutil is used without EAS.
> >
> > Are they still going to be handled as before after this change?
>
> Well they should still get boosted (under the new conditions) and according
> to my tests that does work.

OK

> Anything in particular you're worried about?

It is not particularly clear to me how exactly the boost is taken into
account without EAS.

> So in terms of throughput I see similar results with EAS and CAS+sugov.
> I'm happy including numbers in the cover letter for future versions, too.
> So far my intuition was that nobody would care enough to include them
> (as long as it generally still works).

Well, IMV clear understanding of the changes is more important.