linux-kernel - Re: [PATCH v11 10/24] perf config: Document variables for 'call-graph' section in man page

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Message-ID: <20151118025104.GI7062@sejong>
Date:	Wed, 18 Nov 2015 11:51:04 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Taeung Song <treeze.taeung@...il.com>
CC:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH v11 10/24] perf config: Document variables for
 'call-graph' section in man page

On Tue, Nov 17, 2015 at 10:53:30PM +0900, Taeung Song wrote:
> Explain 'call-graph' section and its variables.
> 
> 'record-mode', 'dump-size', 'print-type', 'order',
> 'sort-key', 'threshold' and 'print-limit'.
> 
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Signed-off-by: Taeung Song <treeze.taeung@...il.com>
> ---
>  tools/perf/Documentation/perf-config.txt | 65 ++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/tools/perf/Documentation/perf-config.txt b/tools/perf/Documentation/perf-config.txt
> index 7d386d4..dc659d6 100644
> --- a/tools/perf/Documentation/perf-config.txt
> +++ b/tools/perf/Documentation/perf-config.txt
> @@ -285,6 +285,71 @@ ui.*::
>  		There're columns as header 'Overhead', 'Children', 'Shared Object', 'Symbol', 'self'.
>  		If this option is false, they are hiden. This option is only applied to TUI.
>  
> +call-graph.*::
> +	When sub-commands 'top' and 'report' work with -g/—-children
> +	there're options in control of call-graph.
> +
> +	call-graph.record-mode::
> +		The record-mode can be 'fp' (frame pointer) and 'dwarf'.

Also 'lbr' can be used, but it only work for recent intel cpus.


> +		The value of 'dwarf' is effective only if perf detect needed library
> +		(libunwind or a recent version of libdw).  Also it doesn't *require*
> +		the dump-size option since it can use the default value of 8192 if
> +		missing.

I think the last sentence can be omitted.


> +
> +	call-graph.dump-size::
> +		The size of stack to dump in order to do post-unwinding. Default is 8192 (byte).
> +		When using dwarf into record-mode this option should have a value.

This contradicts the above, it'll use the default size if omitted.


> +
> +	call-graph.print-type::
> +		The print-types can be graph (graph absolute), fractal (graph relative), flat.
> +		This option controls a way to show overhead for each callchain entry.
> +		Suppose a following example.
> +
> +		Overhead  Symbols
> +		........  .......
> +		  40.00%  foo
> +		      |
> +		      --- foo
> +		      |
> +		      |--50.00%-- bar
> +		      |           main
> +		      |
> +		      --50.00%-- baz
> +		                 main

                      ^
		      it needs one more whitespace


> +
> +		This output is a 'fractal' format. The 'foo' came from 'bar' and 'baz' exactly
> +		half and half so 'fractal' shows 50.00% for each
> +		(meaning that it assumes 100% total overhead of 'foo').
> +
> +		The 'graph' uses absolute overhead value of 'foo' as total so each of
> +		'bar' and 'baz' callchain will have 20.00% of overhead.
> +
> +	call-graph.order::
> +		This option controls print order of callchains. The default is
> +		'callee' which means callee is printed at top and then followed by its
> +		caller and so on. The 'caller' prints it in reverse order.
> +
> +		If this option is not set and report.children or top.children is
> +		set to true (or the equivalent command line option is given),
> +		the default value of this option is changed to 'caller' for the
> +		execution of 'perf report' or 'perf top'. Other commands will
> +		still default to 'callee'.
> +
> +	call-graph.sort-key::
> +		The callchains are merged if they contain same information.
> +		The sort-key option determines a way to compare the callchains.
> +		A value of 'sort-key' can be 'function' or 'address'.
> +		The default is 'function'.
> +
> +	call-graph.threshold::
> +		When there're many callchains it'd print tons of lines.  So perf omits
> +		small callchains under a certain overhead (threshold) and this option
> +		control the threashold. Default is 0.5 (%).

s/threashold/threshold/

Also it'd be better to mention that the overhead is calculated by
value depends on call-graph.print-type.


> +
> +	call-graph.print-limit::
> +		This is another way to control the number of callchains printed for a
> +		single entry. Default is 0 which means no limitation.

This is a maximum number of lines of callchain printed for a single
histogram entry.

Thanks,
Namhyung


> +
>  SEE ALSO
>  --------
>  linkperf:perf[1]
> -- 
> 1.9.1
> 
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