aperf/mperf

[George Neville-Neil]

On Nov 18, 2010, at 07:32 , Andriy Gapon wrote:

> on 18/11/2010 05:53 George Neville-Neil said the following:
>> 
>> On Nov 16, 2010, at 09:37 , Andriy Gapon wrote:
>> 
>>> 
>>> 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?
>> 
>> 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.
> 
> 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