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

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Date:	Wed, 07 Oct 2015 10:10:33 -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 10:04 AM, Doug Smythies wrote:
> 
> 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 have intel_pstate=no_hwp so that doesn't explain things.  I will send you a
printk debug patch shortly to figure out why your system doesn't see this
problem.  I have _6_ different variants of intel processors that see this same
issue.

What is your model #?

P.


> 
> 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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