linux-kernel - RE: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs

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Date:	Wed, 7 Oct 2015 07:04:20 -0700
From:	"Doug Smythies" <dsmythies@...us.net>
To:	"'Prarit Bhargava'" <prarit@...hat.com>
Cc:	"'Kristen Carlson Accardi'" <kristen@...ux.intel.com>,
	<linux-kernel@...r.kernel.org>,
	"'Viresh Kumar'" <viresh.kumar@...aro.org>,
	<linux-pm@...r.kernel.org>,
	"'Rafael J. Wysocki'" <rjw@...ysocki.net>,
	"Doug Smythies" <dsmythies@...us.net>
Subject: RE: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct on governor switch

On 2015.10.07 03:00 Prarit Bhargava wrote:
> On 10/07/2015 02:51 AM, Doug Smythies wrote:
>> 
>> And before patch I get, using primitives and not cpupower:
>> Executive Summary: Everything works fine (or at least as I thought it was supposed to).
>> 
>> root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
>> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor:powersave
>> ...
>> /sys/devices/system/cpu/cpu7/cpufreq/scaling_governor:powersave
>> root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
>> /sys/devices/system/cpu/intel_pstate/max_perf_pct:100
>> /sys/devices/system/cpu/intel_pstate/min_perf_pct:42
>> root@s15:/home/doug/temp# echo 50 > /sys/devices/system/cpu/intel_pstate/min_perf_pct
>> root@s15:/home/doug/temp# echo 80 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
>> root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
>> /sys/devices/system/cpu/intel_pstate/max_perf_pct:80
>> /sys/devices/system/cpu/intel_pstate/min_perf_pct:50
>> root@s15:/home/doug/temp# for file in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do echo "performance" > $file; done
>> root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
>> /sys/devices/system/cpu/intel_pstate/max_perf_pct:100
>> /sys/devices/system/cpu/intel_pstate/min_perf_pct:100
>> root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
>> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor:performance
>
> The switch has to be from performance to powersave.  Switch again and you'll see
> the problem.

Yes, of course, and I did.
The first "powersave" listing was just to show the setup.
Continue reading my original reply, also added back below:
The "..." stuff is just where I deleted 6 of the 8 CPUs saying the same thing.

root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:100
/sys/devices/system/cpu/intel_pstate/min_perf_pct:100
root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor:performance
...
/sys/devices/system/cpu/cpu7/cpufreq/scaling_governor:performance
root@s15:/home/doug/temp# for file in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do echo "powersave" > $file; done
root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor:powersave
...
/sys/devices/system/cpu/cpu7/cpufreq/scaling_governor:powersave
root@s15:/home/doug/temp# grep . /sys/devices/system/cpu/intel_pstate/*_perf_*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:80
/sys/devices/system/cpu/intel_pstate/min_perf_pct:50

> I can also reproduce this without using 'cpupower'.

Interesting. Then maybe it is a difference between legacy mode
and Hardware P state (HWP) mode. I do not have an HWP capable processor
to test.

I compiled cpupower, but get the same results as I get using primitives,
meaning things work properly before the patch and resort to defaults
after the patch.

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