linux-kernel - Re: [PATCH 2/4 v2] x86: use common aperfmperf_khz_on

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Message-ID: <CAJZ5v0j2m-tQz0CkrX9uPiNbivkXhiF-orEGqRAAa-euUqXqNQ@mail.gmail.com>
Date:   Sat, 24 Jun 2017 14:03:41 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 2/4 v2] x86: use common aperfmperf_khz_on_cpu() to
 calculate KHz using APERF/MPERF

On Sat, Jun 24, 2017 at 10:56 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Fri, 23 Jun 2017, Len Brown wrote:
>> This x86 native method to calculate MHz returns a meaningful result
>> no matter if P-states are controlled by hardware or firmware
>> and/or if the Linux cpufreq sub-system is or is-not installed.
>>
>> When this routine is invoked more frequently, the measurement
>> interval becomes shorter.  However, the code limits re-computation
>> to 10ms intervals so that average frequency remains meaningful.
>>
>> Discerning users are encouraged to take advantage of
>> the turbostat(8) utility, which can gracefully handle
>> concurrent measurement intervals of arbitrary length.
>>
>> Signed-off-by: Len Brown <len.brown@...el.com>
>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
>
> Raphael, please take the whole lot through the cpufreq tree.

I will, thanks!

Rafael