linux-kernel - Re: [PATCH RFC -tip 0/6] perf: IRQ-bound performance events

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Message-ID: <20130604093802.GK8923@twins.programming.kicks-ass.net>
Date:	Tue, 4 Jun 2013 11:38:02 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Jiri Olsa <jolsa@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH RFC -tip 0/6] perf: IRQ-bound performance events

On Mon, Jun 03, 2013 at 03:36:19PM +0200, Alexander Gordeev wrote:
> On Mon, Jun 03, 2013 at 11:41:32AM +0200, Alexander Gordeev wrote:
> > # ./tools/perf/perf stat -I 8 -a -e L1-dcache-load-misses:k sleep 1
> > 
> >  Performance counter stats for process id '8':
> > 
> >                  0 L1-dcache-load-misses                                       
> > 
> >        1.001235781 seconds time elapsed
> > 
> > # ./tools/perf/perf stat -I 8 -a -e L1-dcache-load-misses:k hwclock --test
> > Mon 03 Jun 2013 04:42:59 AM EDT  -0.891274 seconds
> > 
> >  Performance counter stats for process id '8':
> 
> Oops, the most interesting part did not make it in. Very sorry :) Here:
> 
> # ./tools/perf/perf stat -I 8 -a -e L1-dcache-load-misses:k hwclock --test
> Mon 03 Jun 2013 09:32:49 AM EDT  -0.719514 seconds
> 
>  Performance counter stats for process id '8':
> 
>                447 L1-dcache-load-misses                                       

I think that is very much expected; except in the case where you spend
_all_ your time in IRQ handlers, they'll pretty much always miss l1
cache.
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