linux-kernel - Re: [PATCH 13/16] perf callchain: Switch default to 'graph,0.5,caller'

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Date:	Mon, 12 Oct 2015 17:27:33 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Borislav Petkov <bp@...e.de>,
	Chandler Carruth <chandlerc@...il.com>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH 13/16] perf callchain: Switch default to
 'graph,0.5,caller'

On Mon, Oct 05, 2015 at 06:03:35PM -0300, Arnaldo Carvalho de Melo wrote:
> From: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> Which is the most common default found in other similar tools.
> 
> Requested-by: Ingo Molnar <mingo@...nel.org>
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Chandler Carruth <chandlerc@...il.com>
> Cc: David Ahern <dsahern@...il.com>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Stephane Eranian <eranian@...gle.com>
> Cc: Wang Nan <wangnan0@...wei.com>
> Link: https://www.youtube.com/watch?v=nXaxk27zwlk
> Link: http://lkml.kernel.org/n/tip-v8lq36aispvdwgxdmt9p9jd9@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/Documentation/perf-report.txt | 2 +-
>  tools/perf/builtin-report.c              | 4 ++--
>  tools/perf/util/util.c                   | 4 ++--
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
> index ce499035e6d8..e4fdeeb51123 100644
> --- a/tools/perf/Documentation/perf-report.txt
> +++ b/tools/perf/Documentation/perf-report.txt
> @@ -192,7 +192,7 @@ OPTIONS
>  	when available. Usually more convenient to use --branch-history
>  	for this.
>  
> -	Default: fractal,0.5,callee,function.
> +	Default: graph,0.5,caller
>  
>  --children::
>  	Accumulate callchain of children to parent entry so that then can
> diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> index b5623639f67d..3b23b25d1589 100644
> --- a/tools/perf/builtin-report.c
> +++ b/tools/perf/builtin-report.c
> @@ -633,7 +633,7 @@ int cmd_report(int argc, const char **argv, const char *prefix __maybe_unused)
>  	bool has_br_stack = false;
>  	int branch_mode = -1;
>  	bool branch_call_mode = false;
> -	char callchain_default_opt[] = "fractal,0.5,callee";
> +	char callchain_default_opt[] = "graph,0.5,caller";

I'm a bit worried about that. I find callee order usually useful in most cases.
People tend to run perf to zoom in the culprit of a performance issue.

>  	const char * const report_usage[] = {
>  		"perf report [<options>]",
>  		NULL
> @@ -701,7 +701,7 @@ int cmd_report(int argc, const char **argv, const char *prefix __maybe_unused)
>  		    "Only display entries with parent-match"),
>  	OPT_CALLBACK_DEFAULT('g', "call-graph", &report, "output_type,min_percent[,print_limit],call_order[,branch]",
>  		     "Display callchains using output_type (graph, flat, fractal, or none) , min percent threshold, optional print limit, callchain order, key (function or address), add branches. "
> -		     "Default: fractal,0.5,callee,function", &report_parse_callchain_opt, callchain_default_opt),
> +		     "Default: graph,0.5,caller", &report_parse_callchain_opt, callchain_default_opt),
>  	OPT_BOOLEAN(0, "children", &symbol_conf.cumulate_callchain,
>  		    "Accumulate callchains of children and show total overhead as well"),
>  	OPT_INTEGER(0, "max-stack", &report.max_stack,
> diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
> index ce465b259e52..c1bf9ff210b0 100644
> --- a/tools/perf/util/util.c
> +++ b/tools/perf/util/util.c
> @@ -17,9 +17,9 @@
>  #include "callchain.h"
>  
>  struct callchain_param	callchain_param = {
> -	.mode	= CHAIN_GRAPH_REL,
> +	.mode	= CHAIN_GRAPH_ABS,

And this worries me as well :-)

>  	.min_percent = 0.5,
> -	.order  = ORDER_CALLEE,
> +	.order  = ORDER_CALLER,
>  	.key	= CCKEY_FUNCTION
>  };
>  
> -- 
> 2.1.0
> 
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