linux-kernel - Re: [PATCHSET 0/8] perf tools: Fix scalability problem on callchain merging (v5)

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Date:	Fri, 11 Oct 2013 17:24:59 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCHSET 0/8] perf tools: Fix scalability problem on callchain merging (v5)

Hi Jiri,

On Fri, 11 Oct 2013 09:34:48 +0200, Jiri Olsa wrote:
> On Fri, Oct 11, 2013 at 07:58:29AM +0200, Ingo Molnar wrote:
>> 
>> * Namhyung Kim <namhyung@...nel.org> wrote:
>> 
>> > Hello,
>> > 
>> > This is a new version of callchain improvement patchset.  Basically
>> > it's almost same as v4 but rebased on current acme/perf/core and some
>> > functions are renamed as Frederic requested.
>> > 
>> > Now I'm hunting down a bug in 'perf report -s sym' which was found
>> > during the test, but I think it's not related to this change as it can
>> > be reproduced in earlier versions too.
>> > 
>> > I put this series on 'perf/callchain-v5' branch in my tree
>> > 
>> >   git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
>> > 
>> > Any comments are welcome, thanks.
>> 
>> One thing I noticed about call-graph profiling:
>> 
>>   comet:~/tip/tools/perf> ./perf record -g ~/hackbench 10
>>   callchain: Unknown -g option value: /home/mingo/hackbench
>> 
>> I think a naked -g used to work just fine in the past. Even if such an 
>> error is displayed the output is very unhelpful, it does does a full 
>> perf-record options dump (unnecessary), the bit that is helpful is hidden 
>> amongst many other options:
>> 
>>     -g, --call-graph <mode[,dump_size]>
>>                           do call-graph (stack chain/backtrace) recording: [fp] dwarf
>> 
>> and it took me two reads to see that I should specify 'fp'. The '[fp]' 
>> indicates that fp is the default - but that does not appear to be working.
>
> '-g' takes optional parameter, so having it in front of
> non option string is causing the error, you could use:
>
> ./perf record -g -- ~/hackbench 10

Yes, I think this is an unfortunate change to break some user's
scripts.  It'd be great if it detect whether the next argument belongs
to the option, or if not, pass it to next normally - but it seems to be
not so simple IMHO.

>
> maybe we could display just only help string of the option
> we failed to process in this case

Right, I think it's more helpful in most cases.

Thanks,
Namhyung
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