linux-kernel - Re: [PATCH v3] perf/rapl: support per domain energy unit

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Date:	Mon, 15 Jun 2015 13:32:01 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Stephane Eranian <eranian@...gle.com>,
	Paul Mackerras <paulus@...ba.org>,
	Andi Kleen <andi.kleen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v3] perf/rapl: support per domain energy unit

On Thu, 26 Mar 2015, Jacob Pan wrote:

> RAPL energy hardware unit can vary within a single CPU package, e.g.
> HSW server DRAM has a fixed energy unit of 15.3 uJ (2^-16) whereas
> the unit on other domains can be enumerated from power unit MSR.
> There might be other variations in the future, this patch adds
> per cpu model quirk to allow special handling of certain cpus.

So I have a Desktop Haswell machine (model 60) that is instrumented to 
measure actual DRAM power at the DIMM (with a sense resistor).

We are consistently getting RAPL results roughly a factor of 2 smaller 
than the actual, measured results.

Does desktop Haswell have a similar units issue to Haswell-EP?

I wasted a bunch of time trying to decode the 
DRAM_ENERGY_SCALEFACTOR_MCHBAR values described in the
Desktop 4th Generation Intel Core Processor Family
datasheet but possibly that value in the MCHBAR is unrelated to the one 
exported by the RAPL interface.

Vince
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