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

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Date:	Wed, 07 Oct 2015 05:59:56 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Doug Smythies <dsmythies@...us.net>
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>
Subject: Re: [PATCH] cpufreq, intel_pstate, set max_sysfs_pct and min_sysfs_pct
 on governor switch



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

P.
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