linux-kernel - Re: [PATCH] intel_pstate: track and export frequency residency stats via sysfs.

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Message-ID: <CAKohpo=GWbWNFg7=w-Lw5w4fWk1+okRwv0rQwX82XMTg8s_9Lw@mail.gmail.com>
Date:	Wed, 10 Sep 2014 12:19:51 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Anup Chenthamarakshan <anupc@...omium.org>
Cc:	Dirk Brandewie <dirk.j.brandewie@...el.com>,
	Sameer Nanda <snanda@...omium.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] intel_pstate: track and export frequency residency stats
 via sysfs.

On 10 September 2014 05:01, Anup Chenthamarakshan <anupc@...omium.org> wrote:
> Here's a comparison of time taken to run intel_pstate_set_pstate() using
> different approaches:
>                                   average time for a transition
> no stats                                      4.7us
> intel_pstate-stats                            5.7us
> direct call to cpufreq_stat_notifier_trans    8.1us
> cpufreq-notifier-event                       10.6us
>
>
> I was wrong about the 5x increase (got tripped by calls to
> intel_pstate_set_pstate where no change in P-state actually happened)

Okay, lets see if this is the right thing to do or not first. So
finish your discussion with
Dirk and then we will see what's the best way to do it.
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