linux-kernel - Re: Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq

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Message-ID: <CAJZ5v0ivJiPhuh7Gk3KpujKjvFGAY6EYQrNdu8=kao59xqsgHw@mail.gmail.com>
Date:   Tue, 17 Jul 2018 11:06:29 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andreas Herrmann <aherrmann@...e.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Commit 554c8aa8ecad causing severe performance degression with pcc-cpufreq

On Tue, Jul 17, 2018 at 10:50 AM, Andreas Herrmann <aherrmann@...e.com> wrote:

[cut]

>
> On balance before this commit users could use pcc-cpufreq but had
> already suboptimal performance (compared to say intel_pstate driver
> which can be used changing BIOS options).

BTW, I wonder why you need to change the BIOS options for intel_pstate to load.

It should be initialized before pcc-cpufreq (according to their
respective initcall levels), so in theory intel_pstate should be used
by default on the affected systems anyway.

What BIOS settings need to be changed for that?