linux-kernel - Re: [cpufreq] 909c0e9cc1: fwq.fwq.med 210.0% improvement

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Date:   Thu, 5 Mar 2020 10:05:48 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Rong Chen <rong.a.chen@...el.com>
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "open list:ACPI COMPONENT ARCHITECTURE (ACPICA)" <devel@...ica.org>,
        Linux PM <linux-pm@...r.kernel.org>, lkp@...ts.01.org,
        Rafael Wysocki <rafael@...nel.org>
Subject: Re: [cpufreq] 909c0e9cc1: fwq.fwq.med 210.0% improvement

On Thu, Mar 5, 2020 at 9:18 AM Rong Chen <rong.a.chen@...el.com> wrote:
>
>
>
> On 3/5/20 3:50 PM, Rafael J. Wysocki wrote:
> > On 3/5/2020 2:35 AM, kernel test robot wrote:
> >> Greeting,
> >>
> >> FYI, we noticed a 210.0% improvement of fwq.fwq.med due to commit:
> >
> > Well, that sounds impressive. :-)
> >
> >
> >>
> >> commit: 909c0e9cc11ba39fa5a660583b25c2431cf54deb ("cpufreq:
> >> intel_pstate: Use passive mode by default without HWP")
> >> https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git
> >> intel_pstate-passive
> >>
> >> in testcase: fwq
> >> on test machine: 16 threads Intel(R) Xeon(R) CPU D-1541 @ 2.10GHz
> >> with 48G memory
> >> with following parameters:
> >>
> >>     nr_task: 100%
> >>     samples: 100000ss
> >>     iterations: 18x
> >>     cpufreq_governor: powersave
> >
> > The governor should be schedutil, though, unless it is explicitly set
> > to powersave in the test environment.
> >
> > Is that the case?
> >
> >
>
> Hi Rafael,
>
> Yes, we set to powersave for this test.

I wonder why this is done?  Is there any particular technical reason
for doing that?