linux-kernel - Re: [PATCH 1/1] perf stat: Only auto-merge events that are PMU aliases

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Date:   Fri, 1 Sep 2017 13:20:11 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>, Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf stat: Only auto-merge events that are PMU
 aliases

On Thu, Aug 31, 2017 at 03:41:22PM -0300, Arnaldo Carvalho de Melo wrote:
> Hi Andi, Jiri,
> 
> 	Please check the patch below, would be glad to have your acks,
> 
> - Arnaldo
> 
> Peter reported that when he explicitely asked for multiple events with
> the same name on the command line it got coalesced into just one line,
> i.e.:
> 
>    # perf stat -e cycles -e cycles -e cycles usleep 1
> 
>    Performance counter stats for 'usleep 1':
> 
>          3,269,652      cycles
> 
>        0.000884123 seconds time elapsed
> 
>   #
> 
> And while there is the --no-merges option to disable that auto-merging, this is
> an blunt change in behaviour for such explicit request, so change the code so
> that this auto merging is done only when handling the multi PMU aliases with
> the same name that introduced this coalescing, restoring the previous behaviour
> for explicit case:
> 
>   # perf stat -e cycles -e cycles -e cycles usleep 1
> 
>    Performance counter stats for 'usleep 1':
> 
>          1,472,837      cycles
>          1,472,837      cycles
>          1,472,837      cycles
> 
>        0.001764870 seconds time elapsed
> 
>   #
> 
> Reported-by: Peter Zijlstra <peterz@...radead.org>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Wang Nan <wangnan0@...wei.com>
> Fixes: 430daf2dc7af ("perf stat: Collapse identically named events")
> Link: http://lkml.kernel.org/n/tip-phjedddz2oe8udy9co3alo7d@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

Thanks Arnaldo!