Re: [RFC 0/3] Experimental patchset for CPPC

From: Len Brown
Date: Fri Aug 15 2014 - 18:22:16 EST

> I verified that CPU freq requests were taken by reading out the PERF_STATUS register.

Don't use the x86 PERF_STATUS register -- it will not tell you what
you want to know.

If you want to see the actual frequency, you need to watch how many
cycles elapse per a known time interval,
which is how intel_pstate and the turbostat utility do it.

Len Brown
Intel Open Source Technology Center
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