linux-kernel - [PATCH 0/3] Add support for frequency invariance to AMD EPYC Zen2

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Date:   Tue, 10 Nov 2020 09:39:33 +0100
From:   Giovanni Gherdovich <ggherdovich@...e.cz>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
Cc:     Jon Grimm <Jon.Grimm@....com>,
        Nathan Fontenot <Nathan.Fontenot@....com>,
        Yazen Ghannam <Yazen.Ghannam@....com>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pu Wen <puwen@...on.cn>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Doug Smythies <dsmythies@...us.net>, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        Giovanni Gherdovich <ggherdovich@...e.cz>
Subject: [PATCH 0/3] Add support for frequency invariance to AMD EPYC Zen2

This series adds support for frequency invariant accounting on AMD EPYC Zen2
(aka "Rome"). The first patch by Nathan lays out the foundation by querying
ACPI infrastructure for the max boost frequency of the system. Specifically,
this value is available via the CPPC machinery; the previous EPYC generation,
namely Zen aka "Naples", doesn't implement that and frequency invariance won't
be supported.

The second patch sets the estimate for freq_max to be the midpoint between
max_boost and max_P, as that works slightly better in practice.

A side effect of this series is to provide, with the invariant schedutil
governor, a suitable baseline to evaluate a (still work-in-progress)
CPPC-based cpufreq driver for the AMD platform (see
https://lore.kernel.org/lkml/cover.1562781484.git.Janakarajan.Natarajan@amd.com
if/when it will resubmitted.

Giovanni Gherdovich (2):
  x86, sched: Use midpoint of max_boost and max_P for frequency
    invariance on AMD EPYC
  x86: Print ratio freq_max/freq_base used in frequency invariance
    calculations

Nathan Fontenot (1):
  x86, sched: Calculate frequency invariance for AMD systems

 arch/x86/include/asm/topology.h |  8 ++++
 arch/x86/kernel/smpboot.c       | 79 +++++++++++++++++++++++++++++----
 drivers/acpi/cppc_acpi.c        |  5 +++
 3 files changed, 84 insertions(+), 8 deletions(-)

-- 
2.26.2