From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Giovanni Gherdovich <ggherdovich@suse.cz>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@suse.de>, Len Brown <lenb@kernel.org>,
x86@kernel.org, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org,
Mel Gorman <mgorman@techsingularity.net>,
Matt Fleming <matt@codeblueprint.co.uk>,
Viresh Kumar <viresh.kumar@linaro.org>,
Juri Lelli <juri.lelli@redhat.com>, Paul Turner <pjt@google.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Quentin Perret <qperret@qperret.net>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Doug Smythies <dsmythies@telus.net>
Subject: Re: [PATCH v2 2/2] cpufreq: intel_pstate: Conditional frequency invariant accounting
Date: Thu, 03 Oct 2019 20:05:40 +0200 [thread overview]
Message-ID: <13106850.QMtCbivBLn@kreacher> (raw)
In-Reply-To: <20191002122926.385-3-ggherdovich@suse.cz>
On Wednesday, October 2, 2019 2:29:26 PM CEST Giovanni Gherdovich wrote:
> From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
>
> intel_pstate has two operating modes: active and passive. In "active"
> mode, the in-built scaling governor is used and in "passive" mode,
> the driver can be used with any governor like "schedutil". In "active"
> mode the utilization values from schedutil is not used and there is
> a requirement from high performance computing use cases, not to read
> any APERF/MPERF MSRs.
Well, this isn't quite convincing.
In particular, I don't see why the "don't read APERF/MPERF MSRs" argument
applies *only* to intel_pstate in the "active" mode. What about intel_pstate
in the "passive" mode combined with the "performance" governor? Or any other
governor different from "schedutil" for that matter?
And what about acpi_cpufreq combined with any governor different from
"schedutil"?
Scale invariance is not really needed in all of those cases right now AFAICS,
or is it?
So is the real concern that intel_pstate in the "active" mode reads the MPERF
and APERF MSRs by itself and that kind of duplicates what the scale invariance
code does and is redundant etc?
next prev parent reply other threads:[~2019-10-03 18:05 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 12:29 [PATCH v2 0/2] Add support for frequency invariance for (some) x86 Giovanni Gherdovich
2019-10-02 12:29 ` [PATCH v2 1/2] x86,sched: Add support for frequency invariance Giovanni Gherdovich
2019-10-02 15:23 ` kbuild test robot
2019-10-02 15:49 ` Giovanni Gherdovich
2019-10-02 16:43 ` kbuild test robot
2019-10-02 18:27 ` Peter Zijlstra
2019-10-03 10:27 ` Rafael J. Wysocki
2019-10-03 12:15 ` Peter Zijlstra
2019-10-03 17:36 ` Srinivas Pandruvada
2019-10-03 17:53 ` Rafael J. Wysocki
2019-10-04 11:48 ` Peter Zijlstra
2019-10-08 7:48 ` Giovanni Gherdovich
2019-10-08 9:32 ` Rafael J. Wysocki
2019-10-02 12:29 ` [PATCH v2 2/2] cpufreq: intel_pstate: Conditional frequency invariant accounting Giovanni Gherdovich
2019-10-03 18:05 ` Rafael J. Wysocki [this message]
2019-10-04 3:31 ` Srinivas Pandruvada
2019-10-04 8:08 ` Rafael J. Wysocki
2019-10-04 8:29 ` Giovanni Gherdovich
2019-10-04 8:28 ` Vincent Guittot
2019-10-04 8:33 ` Rafael J. Wysocki
2019-10-04 8:29 ` Rafael J. Wysocki
2019-10-04 8:57 ` Giovanni Gherdovich
2019-10-04 9:17 ` Rafael J. Wysocki
2019-10-04 15:17 ` Srinivas Pandruvada
2019-10-07 8:33 ` Giovanni Gherdovich
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