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

From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Christian Loehle <christian.loehle@arm.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	linux-kernel@vger.kernel.org, peterz@infradead.org,
	 juri.lelli@redhat.com, mingo@redhat.com,
	dietmar.eggemann@arm.com,  vschneid@redhat.com,
	vincent.guittot@linaro.org, Johannes.Thumshirn@wdc.com,
	 adrian.hunter@intel.com, ulf.hansson@linaro.org,
	andres@anarazel.de,  asml.silence@gmail.com,
	linux-pm@vger.kernel.org, linux-block@vger.kernel.org,
	 io-uring@vger.kernel.org
Subject: Re: [RFC PATCH 2/2] cpufreq/schedutil: Remove iowait boost
Date: Mon, 18 Mar 2024 18:08:44 +0100	[thread overview]
Message-ID: <CAJZ5v0janPrWRkjcLkFeP9gmTC-nVRF-NQCh6CTET6ENy-_knQ@mail.gmail.com> (raw)
In-Reply-To: <5060c335-e90a-430f-bca5-c0ee46a49249@arm.com>

On Mon, Mar 18, 2024 at 5:40 PM Christian Loehle
<christian.loehle@arm.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@arm.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.