linux-kernel - Re: [RFC/PATCHSET 00/17] perf tools: Add support for hierachy view (v2)

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Date:	Wed, 20 Jan 2016 09:56:47 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Wang Nan <wangnan0@...wei.com>,
	Don Zickus <dzickus@...hat.com>,
	Pekka Enberg <penberg@...nel.org>,
	Moinuddin Quadri <moin18@...il.com>
Subject: Re: [RFC/PATCHSET 00/17] perf tools: Add support for hierachy view
 (v2)

On Tue, Jan 19, 2016 at 07:24:49PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jan 19, 2016 at 11:12:04PM +0100, Andi Kleen escreveu:
> > > > Now we only need a better percent-limit that handles all
> > > > leaves correctly...
> > > 
> > > Hmm.. could you tell me where the percent-limit doesn't work
> > > correctly?
> > 
> > It doesn't work well together with call chains.
> 
> Ok, that is the missing piece of info, lemme check... Yeah that seems
> to be the case.

So technically this is a callchain issue not a hist entry, right?  If
so, it should be fixed separately.  Currently --percent-limit option
works only for hist entries, and for callchain, users should use
-g/--call-graph option.  With hierarchy report, we might consider
merging them since it provides continuous interface to callchains..


>  
> > It only considers the hits on the leaf function, but doesn't hide
> > the individual call chains leading to that function which are below
> > the limit.
> > 
> > So if you have a lot of different cold callers you still end up
> > with far too much output.

Could you please be more specific?  Let me try with an example..

  $ perf report
  ...
  +    1.00%  perf  perf  some_function
           some_function
         - common_caller
            - 0.6% caller1
              + 0.4% caller1_1
              + 0.2% caller1_2
            + 0.3% caller2
            + 0.1% caller3

In this case, do you want this?

  $ perf report --percent-limit 0.5
  ...
  +    1.00%  perf  perf  some_function
           some_function
         - common_caller
            - 0.6% caller1


> > 
> > Also would be nice to be able to set it dynamically from the UI.
> 
> To set the mim percent? Yeah, we need to allow setting all those knobs
> from the UI.
> 
> I.e. should be like when we press '/' to set a substring filter.

Yes, how about 'L' key for limit?

Thanks,
Namhyung