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

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Message-ID: <20160125183511.GA24981@gmail.com>
Date:	Mon, 25 Jan 2016 19:35:11 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...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


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:

 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