linux-kernel - Re: perf tools miscellaneous questions

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Message-ID: <m2wros3pzf.fsf@gmail.com>
Date:	Fri, 05 Nov 2010 13:38:12 +0100
From:	Francis Moreau <francis.moro@...il.com>
To:	Victor Jimenez <victor.javier@....es>
Cc:	Reid Kleckner <reid.kleckner@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Stephane Eranian <eranian@...gle.com>,
	linux-perf-users@...r.kernel.org
Subject: Re: perf tools miscellaneous questions

Victor Jimenez <victor.javier@....es> writes:

[...]

> If you are measuring last level cache misses, I would recommend you to
> use a memory intensive application/benchmark instead of /bin/true, as
> otherwise there can be a significant variation between two runs.

I agree.

But still with intensive application, I got the same results:


  $ perf stat -r3 -e cache-misses:u gzip -9 -c vmlinux.o >/dev/null

   Performance counter stats for 'gzip -9 -c vmlinux.o' (3 runs):

               950704  cache-misses               ( +-  24.925% )

         82.619412905  seconds time elapsed   ( +-   0.072% )


  $ perf stat -r3 -e llc-load-misses:u,llc-store-misses:u gzip -9 -c vmlinux.o >/dev/null

   Performance counter stats for 'gzip -9 -c vmlinux.o' (3 runs):
  
               317054  LLC-load-misses            ( +-  11.758% )
               162634  LLC-store-misses           ( +-   9.700% )

         82.657099783  seconds time elapsed   ( +-   0.167% )

Thanks
-- 
Francis
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