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

Peter Zijlstra
2014-07-17T08:40:26Z

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On Thu, Jul 17, 2014 at 05:31:14PM +0900, Namhyung Kim wrote:
> Hi Peter,
>
> On Thu, Jul 17, 2014 at 5:26 PM, Peter Zijlstra <peterz@infradead.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.

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