linux-kernel - Re: [PATCH] perf stat: Pass PERF_STAT_RUN environment variable for each run

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Message-ID: <87d2d3l0hr.fsf@sejong.aot.lge.com>
Date:	Fri, 18 Jul 2014 14:06:08 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>, Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH] perf stat: Pass PERF_STAT_RUN environment variable for each run

Hi Arnaldo and Peter,

On Thu, 17 Jul 2014 10:09:43 -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jul 17, 2014 at 10:40:11AM +0200, Peter Zijlstra escreveu:
>> On Thu, Jul 17, 2014 at 05:31:14PM +0900, Namhyung Kim wrote:
>> > On Thu, Jul 17, 2014 at 5:26 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> > > On Thu, Jul 17, 2014 at 05:21:06PM +0900, Namhyung Kim wrote:
>> > >> When perf stat runs multiple times via -r option, it's sometimes
>> > >> useful for a workload to know which run it executing.  So pass new
>> > >> PERF_STAT_RUN environment variable to the workload for each run
>> > >> (starting from 1).
>
>> > > This seems counter intuitive, runs should be _identical_ otherwise
>> > > there's no point. That means the workload should very much _not_ know
>> > > these things.
>
>> > But I think it can be useful if a workload wants to save logfiles
>> > based on the iteration number for example.  If it doesn't want, it can
>> > just ignore. :)
>
>> That's the wrong way around. Also, there's --pre and --post hooks to
>> preserve logfiles if you really have to do that kind of thing.
>
> Agreed, one can script this using --pre or --post if needed.

Hmm... okay, I'll drop this then.

Thanks,
Namhyung
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