linux-kernel - Re: [PATCH v1 0/2] perf,x86: add Intel RAPL PMU support

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Date:	Mon, 7 Oct 2013 18:24:18 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>,
	"Yan, Zheng" <zheng.z.yan@...el.com>
Subject: Re: [PATCH v1 0/2] perf,x86: add Intel RAPL PMU support

On Mon, Oct 7, 2013 at 6:19 PM, Borislav Petkov <bp@...en8.de> wrote:
> On Mon, Oct 07, 2013 at 06:09:15PM +0200, Stephane Eranian wrote:
>> The counters all count in the same unit. The perf_events API
>> exposes all RAPL counters as 64-bit integers counting in unit
>> of 1/2^32 Joules (or 0.23 nJ). User level tools must convert
>> the counts by multiplying them by 0.23 and divide 10^9 to
>> obtain Joules.  The reason for this is that the kernel avoids
>> doing floating point math whenever possible because it is
>> expensive (user floating-point state must be saved). The method
>> used avoids kernel floating-point and minimizes the loss of
>> precision (bits). Thanks to PeterZ for suggesting this approach.
>>
>> To convert the raw count in Watt: W = C * 0.23 / (1e9 * time)
>
> ...
>
>> $ perf stat -a -e rapl/rapl-energy-cores/,rapl/rapl-energy-pkg/ -I 1000 sleep 10
>>             time             counts events
>>      1.000345931        772 278 493 rapl/rapl-energy-cores/
>>      1.000345931     55 539 138 560 rapl/rapl-energy-pkg/
>>      2.000836387        771 751 936 rapl/rapl-energy-cores/
>>      2.000836387     55 326 015 488 rapl/rapl-energy-pkg/
>
> So can we do the Watt conversion in perf tool and make that "counts"
> output more human-friendly like what those numbers are, to which
> core/LLC they belong, etc, etc?
>
We could but that means we would need to special case the events in perf.
I was trying to avoid that.

> Thanks.
>
> --
> Regards/Gruss,
>     Boris.
>
> Sent from a fat crate under my desk. Formatting is fine.
> --
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