linux-kernel - Re: [PATCH v2 2/2] perf record: Show precise number of samples

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Message-ID: <20141128124426.GE27703@krava.brq.redhat.com>
Date:	Fri, 28 Nov 2014 13:44:26 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Milian Wolff <mail@...ianw.de>
Subject: Re: [PATCH v2 2/2] perf record: Show precise number of samples

On Fri, Nov 28, 2014 at 04:14:19PM +0900, Namhyung Kim wrote:
> After perf record finishes, it prints file size and number of samples
> in the file but this info is wrong since it assumes typical sample
> size of 24 bytes and divides file size by the value.
> 
> However as we post-process recorded samples for build-id, it can show
> correct number like below.  If build-id post-processing is not requested
> just omit the wrong number of samples.
> 
>   $ perf record noploop 1
>   [ perf record: Woken up 1 times to write data ]
>   [ perf record: Captured and wrote 0.159 MB perf.data (3989 samples) ]
> 
>   $ perf report --stdio -n
>   # To display the perf.data header info, please use --header/--header-only options.
>   #
>   # Samples: 3K of event 'cycles'
>   # Event count (approx.): 3771330663
>   #
>   # Overhead       Samples  Command  Shared Object     Symbol
>   # ........  ............  .......  ................  ..........................
>   #
>       99.90%          3982  noploop  noploop           [.] main
>        0.09%             1  noploop  ld-2.17.so        [.] _dl_check_map_versions
>        0.01%             1  noploop  [kernel.vmlinux]  [k] setup_arg_pages
>        0.00%             5  noploop  [kernel.vmlinux]  [k] intel_pmu_enable_all
> 
> Reported-by: Milian Wolff <mail@...ianw.de>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

eeeey great, I mean.. finally ;-) 

Reviewed-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka
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