Date: Thu, 18 Nov 2010 14:32:26 +0200 From: Andriy Gapon <avg@freebsd.org> To: George Neville-Neil <gnn@neville-neil.com> Cc: freebsd-acpi@freebsd.org, freebsd-current@freebsd.org Subject: Re: aperf/mperf Message-ID: <4CE51CDA.6010202@freebsd.org> In-Reply-To: <D1DB20AD-779E-469B-BFFA-C0BA1A249858@neville-neil.com> References: <4CE29718.2050508@freebsd.org> <D1DB20AD-779E-469B-BFFA-C0BA1A249858@neville-neil.com>
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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. -- Andriy Gapon
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