linux-kernel - Re: [PATCH 09/15] perf_counter tools: optionally scale counter values in perfstat mode

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Message-ID: <20090401093942.GB27865@elte.hu>
Date:	Wed, 1 Apr 2009 11:39:42 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 09/15] perf_counter tools: optionally scale counter
	values in perfstat mode


* Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:

> From: Paul Mackerras <paulus@...ba.org>
> 
> Impact: new functionality
> 
> This adds add an option to the perfstat mode of kerneltop to scale 
> the reported counter values according to the fraction of time that 
> each counter gets to count.  This is invoked with the -l option (I 
> used 'l' because s, c, a and e were all taken already.)  This uses 
> the new PERF_RECORD_TOTAL_TIME_{ENABLED,RUNNING} read format 
> options.
> 
> With this, we get output like this:
> 
> $ ./perfstat -l -e 0:0,0:1,0:2,0:3,0:4,0:5 ./spin
> 
>  Performance counter stats for './spin':
> 
>      4016072055  CPU cycles           (events)  (scaled from 66.53%)
>      2005887318  instructions         (events)  (scaled from 66.53%)
>         1762849  cache references     (events)  (scaled from 66.69%)
>          165229  cache misses         (events)  (scaled from 66.85%)
>      1001298009  branches             (events)  (scaled from 66.78%)
>           41566  branch misses        (events)  (scaled from 66.61%)
> 
>  Wall-clock time elapsed:  2438.227446 msecs
> 
> This also lets us detect when a counter is zero because the 
> counter never got to go on the CPU at all.  In that case we print 
> <not counted> rather than 0.

Nice! Shouldnt this be the default mode of output?

I think we want to make users aware of the fact when output is 
sampled due to over-commit, rather than precise, agreed?

	Ingo
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