linux-kernel - Re: [RFC/PATCH 0/4] perf report: Support folded callchain output (v2)

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Message-ID: <20151103031701.GE11498@danjae.kornet>
Date:	Tue, 3 Nov 2015 12:17:01 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Brendan Gregg <brendan.d.gregg@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Kan Liang <kan.liang@...el.com>
Subject: Re: [RFC/PATCH 0/4] perf report: Support folded callchain output (v2)

On Mon, Nov 02, 2015 at 10:46:00PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Nov 03, 2015 at 10:35:35AM +0900, Namhyung Kim escreveu:
> > On Mon, Nov 02, 2015 at 09:46:47PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Tue, Nov 03, 2015 at 08:46:06AM +0900, Namhyung Kim escreveu:
> > > > On Mon, Nov 02, 2015 at 08:04:36PM -0300, Arnaldo Carvalho de Melo wrote:
> > > > > I still think that this is a 'perf report' thing, but one that is
> > > > > centered in callchains, and that is to be consumed by scripts, not
> > > > > humans.
> > >  
> > > > Agreed.
> > >  
> > > > I'm just looking for a way to support it with minimal change. :)
> > > 
> > > Hey, me too. A --no-hists flag looks like a quickie, no need to isolate
> > > callchain code, or anything like that, just one long option switch and
> > > we get what we need.
> > 
> > Hmm.. okay.  Let me think about the --no-hists flags then.
> > 
> > What do you want to do if the --no-hists flags is used without folded
> > callchain mode or other than --stdio?
> 
> What the user asked it to, to not show what hist_entry__snprintf()
> produces, i.e. just the callchains.
> 
> Its left to the user to decide if that output is good for whatever
> purpose it has in mind.

OK, will add it in a follow-up patch after checking TUI and GTK.

> 
> We, from this discussion, know that suppressing it when using with
> folded callchains, is useful at least for Brendan's scripts :-)

OK

>  
> > And if you want to print other info in the callchains, what would be
> > the output of non-folded mode?
>  
> > I think the simplest solution would be supporting the folded mode only
> > and error out other cases.  Is it ok to you?
> 
> Well, the other info, if it comes at the end, may even be useful in non
> folded mode, no?

At the end?  Brendan wanted to have it first and I think it'd be
better to show first.

Anyway, this other info depends on the sort keys - IOW it cannot show
task comm name if user gave sort keys without comm like '-s cpu'.  So
how about adding 'info' or 'context' (or whatever name it) option to
-g/--call-graph to show info selected by sort keys.

For example,

  $ perf report --no-children --stdio -s comm,dso -g folded,info --no-hists
  28.63% swapper,[kernel.vmlinux] intel_idle;cpuidle_enter_state;...
  11.30% swapper,[kernel.vmlinux] intel_idle;cpuidle_enter_state;...


  $ perf report --no-children --stdio -s pid,sym -g info
  ...
    39.93%  swapper  [k] intel_idle
            <0:swapper,intel_idle>
	    |
	    |---intel_idel
	        cpuidle_enter_state
		...

What do you think?

Thanks,
Namhyung


> 
> If it is not, then the user will not use it, i.e. some combinations may
> not produce useful results, but if we want to have more flexibility to
> support usecases like Brendan's, and I think we want, without making the
> existing code overly complex, then why not?
> 
> - Arnaldo
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