linux-kernel - Re: [PATCH 08/15] perf stat: Document --detailed option

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Date:	Tue, 8 Mar 2016 10:10:12 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Borislav Petkov <bp@...e.de>,
	Davidlohr Bueso <dbueso@...e.com>,
	Jiri Olsa <jolsa@...hat.com>, Mel Gorman <mgorman@...e.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 08/15] perf stat: Document --detailed option


* Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> From: Borislav Petkov <bp@...e.de>
> 
> I'm surprised this remained undocumented since at least 2011. And it is
> actually a very useful switch, as Steve and I came to realize recently.
> 
> Add the text from
> 
>   2cba3ffb9a9d ("perf stat: Add -d -d and -d -d -d options to show more CPU events")
> 
> which added the incrementing aspect to -d.

Ah yes, my fault ...

> Signed-off-by: Borislav Petkov <bp@...e.de>
> Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Davidlohr Bueso <dbueso@...e.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Mel Gorman <mgorman@...e.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Fixes: 2cba3ffb9a9d ("perf stat: Add -d -d and -d -d -d options to show more CPU events")
> Link: http://lkml.kernel.org/r/1457347294-32546-1-git-send-email-bp@alien8.de
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/Documentation/perf-stat.txt | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
> index 52ef7a9d50aa..14d9e8ffaff7 100644
> --- a/tools/perf/Documentation/perf-stat.txt
> +++ b/tools/perf/Documentation/perf-stat.txt
> @@ -69,6 +69,14 @@ report::
>  --scale::
>  	scale/normalize counter values
>  
> +-d::
> +--detailed::
> +	print more detailed statistics, can be specified up to 3 times
> +
> +	   -d:          detailed events, L1 and LLC data cache
> +        -d -d:     more detailed events, dTLB and iTLB events
> +     -d -d -d:     very detailed events, adding prefetch events

Btw., something I noticed: it would be really nice if 'perf stat -h -d' printed 
the most detailed documentation available for the option. Right now it prints:

 triton:~/tip/tools/perf> perf stat -h -d

  Usage: perf stat [<options>] [<command>]

    -d, --detailed        detailed run - start a lot of events

The only way to get to the most detailed documentation is the not very obvious 
path of:

 perf help stat

and then searching for '-d'.

Ideally there should only be a single place to document options - but I guess 
unifying the in-code option descriptions and more verbose description in the man 
pages is very non-trivial ...

Thanks,

	Ingo