From: Giovanni Gherdovich <ggherdovich@suse.cz>
To: Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
Viresh Kumar <viresh.kumar@linaro.org>
Cc: Jon Grimm <Jon.Grimm@amd.com>,
Nathan Fontenot <Nathan.Fontenot@amd.com>,
Yazen Ghannam <Yazen.Ghannam@amd.com>,
Thomas Lendacky <Thomas.Lendacky@amd.com>,
Suthikulpanit Suravee <Suravee.Suthikulpanit@amd.com>,
Mel Gorman <mgorman@techsingularity.net>, Pu Wen <puwen@hygon.cn>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
x86@kernel.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org
Subject: Re: [PATCH] x86,sched: On AMD EPYC set freq_max = max_boost in schedutil invariant formula
Date: Thu, 21 Jan 2021 02:09:14 +0100 [thread overview]
Message-ID: <1611191354.18842.7.camel@suse.cz> (raw)
In-Reply-To: <20210121003550.20415-1-ggherdovich@suse.cz>
On Thu, 2021-01-21 at 01:35 +0100, Giovanni Gherdovich wrote:
> Phoronix.com discovered a severe performance regression on AMD APYC
> introduced on schedutil [see link 1] by the following commits from v5.11-rc1
>
> commit 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems")
> commit 976df7e5730e ("x86, sched: Use midpoint of max_boost and max_P for frequency invariance on AMD EPYC")
>
> Furthermore commit db865272d9c4 ("cpufreq: Avoid configuring old governors as
> default with intel_pstate") from v5.10 made it extremely easy to default to
> schedutil even if the preferred driver is acpi_cpufreq. Distros are likely to
> build both intel_pstate and acpi_cpufreq on x86, and the presence of the
> former removes ondemand from the defaults. This situation amplifies the
> visibility of the bug we're addressing.
>
> [link 1] https://www.phoronix.com/scan.php?page=article&item=linux511-amd-schedutil&num=1
>
> 1. PROBLEM DESCRIPTION : over-utilization and schedutil
> 2. PROPOSED SOLUTION : raise freq_max in schedutil formula
> 3. DATA TABLE : image processing benchmark
> 4. ANALYSIS AND COMMENTS : with over-utilization, freq-invariance is lost
I've sent this patch twice by mistake, sorry about that.
In case it is of interest, I've shared some plots made while studying this
regression in a bugzilla entry:
https://bugzilla.kernel.org/show_bug.cgi?id=211305
Thanks,
Giovanni
next prev parent reply other threads:[~2021-01-21 1:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-21 0:35 [PATCH] x86,sched: On AMD EPYC set freq_max = max_boost in schedutil invariant formula Giovanni Gherdovich
2021-01-21 1:09 ` Giovanni Gherdovich [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-01-21 0:32 Giovanni Gherdovich
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