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

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Date:	Wed, 20 Jan 2016 02:11:00 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	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 Wed, Jan 20, 2016 at 09:56:47AM +0900, Namhyung Kim wrote:
> 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

Correct.

> 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..

Ideally it should work all modes, not just hierarchy.

> 
> >  
> > > 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

Right. Only call chains whose total percentage is larger than the limit.

> 
> 
> > > 
> > > 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?

Fine for me.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.