aperf/mperf

[Andriy Gapon]

on 18/11/2010 15:38 Daniel Nebdal said the following:
> Just for the sake of gathering information here:
> What they offer are two (64-bit, wrapping) counters; one that
> increases at a constant rate, and one that increases in proportion to
> the current performance of the CPU, so that APERF/MPERF = fraction of
> max possible performance the CPU has offered since the last time the
> counters were zeroed. Intel specifically suggests multiplying that
> with the observed CPU load over the same time period to get an
> absolute CPU load number, and using that to pick a suitable P-state.
> 
> On a tangent, I wonder if you can get APERF>MPERF if you're using an
> i5/i7 and their dynamic/automatic overclocking kicks in?

Yes, I believe so.
At the very least AMD explicitly documents that to be the case when Core
Performance Boost feature is activated.

> As for what to do with it, it sounds like it would make sense as an
> alternate data source for powerd?

Yes, indeed.

-- 
Andriy Gapon