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From: George Neville-Neil <gnn@neville-neil.com>
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Date: Thu, 18 Nov 2010 09:15:52 -0500
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To: Andriy Gapon <avg@FreeBSD.org>
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Subject: Re: aperf/mperf
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On Nov 18, 2010, at 07:32 , Andriy Gapon wrote:

> on 18/11/2010 05:53 George Neville-Neil said the following:
>>=20
>> On Nov 16, 2010, at 09:37 , Andriy Gapon wrote:
>>=20
>>>=20
>>> Many modern processors provide APERF and MPERF MSRs which allow to =
easily and
>>> reliable calculate average CPU performance level over some interval =
of time.
>>> This also allows to notice things like performance boost, which is =
generally
>>> hidden from software.
>>> What would be a proper place to add code that would measure =
APERF/MPERF ratio?
>>> When should trigger such a measurement and over what interval?
>>> Ideas?
>>=20
>> Can you point me at documentation for this?   This sounds a lot like
>> hwpmc(4) and I wonder if we can make these available in the same way.
>=20
> Actually it feels more cpufreq-ish to me.
> This feature is documented in, e.g., Intel Software Developer's Manual =
volume 3A,
> section 14.2 P-STATE HARDWARE COORDINATION.

Ah, yes, quite right on cpufreq etc.  Thanks for the documentation =
pointer though.

Best,
George