linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Fix setting max_perf

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Date:	Tue, 21 Oct 2014 15:30:52 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Dirk Brandewie <dirk.brandewie@...il.com>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: intel_pstate: Fix setting max_perf_pct in performance policy

On Thursday, October 16, 2014 08:05:44 AM Dirk Brandewie wrote:
> On 10/15/2014 04:16 PM, Pali Rohár wrote:
> > Code which changes policy to powersave changes also max_policy_pct based on
> > max_freq. Code which change max_perf_pct has upper limit base on value
> > max_policy_pct. When policy is changing from powersave back to performance
> > then max_policy_pct is not changed. Which means that changing max_perf_pct is
> > not possible to high values if max_freq was too low in powersave policy.
> >
> > Test case:
> >
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq
> > 800000
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> > 3300000
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> > performance
> > $ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> > 100
> >
> > $ echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> > $ echo 800000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> > $ echo 20 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
> >
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> > powersave
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> > 800000
> > $ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> > 20
> >
> > $ echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> > $ echo 3300000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> > $ echo 100 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
> >
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> > performance
> > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq
> > 3300000
> > $ cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
> > 24
> >
> > And now intel_pstate driver allows to set maximal value for max_perf_pct based
> > on max_policy_pct which is 24 for previous powersave max_freq 800000.
> >
> > This patch will set default value for max_policy_pct when setting policy to
> > performance so it will allow to set also max value for max_perf_pct.
> >
> > Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> 
> Acked-by: Dirk Brandewie <dirk.j.brandewie@...el.com>

Applied, thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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