linux-kernel - Re: 'perf stat --repeat N' oddity/regression

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Message-ID: <20160125194333.GA22501@kernel.org>
Date:	Mon, 25 Jan 2016 16:43:33 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: 'perf stat --repeat N' oddity/regression

Em Mon, Jan 25, 2016 at 07:35:11PM +0100, Ingo Molnar escreveu:
> 
> So it appears it broke somewhere between v4.0 and v4.1, as the v4.0 install 
> displays:
> 
>     16,244,802,268      instructions               ( +- 23.01% )
> 
>        2.108676769 seconds time elapsed                                          ( +-  0.86% )
> 
> 
> [a few minutes later]
> 
> Bisected it down to:

Mel Gorman reported this and Jiri provided a patch that Mel tested and
verified that it fixed, checking where it is sitting now...

- Arnaldo
 
>  106a94a0f8c207ef4113ce7e32f34a00b3b174e7 is the first bad commit
>  commit 106a94a0f8c207ef4113ce7e32f34a00b3b174e7
>  Author: Jiri Olsa <jolsa@...nel.org>
>  Date:   Fri Jun 26 11:29:19 2015 +0200
> 
>      perf stat: Introduce read_counters function
> 
> So this look like to be a regression.
> 
> Thanks,
> 
> 	Ingo