linux-kernel - Re: [PATCH 1/4] perf tools: Split -g and --call-graph for record command

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Date:	Mon, 28 Oct 2013 15:46:13 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andi Kleen <andi@...stfloor.org>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 1/4] perf tools: Split -g and --call-graph for record
 command

Em Sun, Oct 27, 2013 at 09:30:06AM -0600, David Ahern escreveu:
> On 10/26/13 8:25 AM, Jiri Olsa wrote:
> >diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> >index f10ab63..7be62770 100644
> >--- a/tools/perf/Documentation/perf-record.txt
> >+++ b/tools/perf/Documentation/perf-record.txt
> >@@ -92,8 +92,12 @@ OPTIONS
> >  	size is rounded up to have nearest pages power of two value.
> >
> >  -g::
> >+	Enables call-graph (stack chain/backtrace) recording.
> >+
> >  --call-graph::
> >-	Do call-graph (stack chain/backtrace) recording.
> >+	Setup and enable call-graph (stack chain/backtrace) recording,
> >+	implies -g.
> >+
> 
> This needs some more words as to why it is used over -g. It is also
> missing the options that can be given (fp or dwarf).

Added this:

--call-graph::
        Setup and enable call-graph (stack chain/backtrace) recording,
        implies -g.

        Allows specifying "fp" (frame pointer) or "dwarf"
        (DWARF's CFI - Call Frame Information) as the method to collect
        the information used to show the call graphs.

        In some systems, where binaries are build wit gcc
        --fomit-frame-pointer, using the "fp" method will produce bogus
        call graphs, using "dwarf", if available (perf tools linked to
        the libunwind library) should be used instead.

 
> ---8<---
> 
> >@@ -825,9 +851,12 @@ const struct option record_options[] = {
> >  		     perf_evlist__parse_mmap_pages),
> >  	OPT_BOOLEAN(0, "group", &record.opts.group,
> >  		    "put the counters into a counter group"),
> >-	OPT_CALLBACK_DEFAULT('g', "call-graph", &record.opts,
> >-			     "mode[,dump_size]", record_callchain_help,
> >-			     &record_parse_callchain_opt, "fp"),
> >+	OPT_CALLBACK(0, "call-graph", &record.opts,
> >+		     "mode[,dump_size]", record_callchain_help,
> >+		     &record_parse_callchain_opt),
> >+	OPT_CALLBACK_NOOPT('g', NULL, &record.opts,
> >+			   NULL, "enables call-graph recording" ,
> >+			   &record_callchain_opt),
> 
> From a user/readability perspective I would prefer the order to be
> -g then --call-graph especially since --call-graph is like an
> advanced -g where you get more control over the method used.

Reordered as suggested.
 
> Other than that:
> 
> Tested-Reviewed-by: David Ahern <dsahern@...il.com>

Thanks, adding those two.

And reworking it to make it apply against my perf/urgent branch, trying to fix
this annoyance on this merge window, as suggested by Ingo.

- Arnaldo
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