linux-kernel - Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist periods (v2)

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Date:	Wed, 6 Nov 2013 12:47:01 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Pekka Enberg <penberg@...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>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Stephane Eranian <eranian@...gle.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Rodrigo Campos <rodrigo@...g.com.ar>,
	Arun Sharma <asharma@...com>
Subject: Re: [RFC/PATCHSET 00/14] perf report: Add support to accumulate hist
 periods (v2)


* Namhyung Kim <namhyung@...nel.org> wrote:

> On Wed, 6 Nov 2013 09:30:46 +0100, Ingo Molnar wrote:
> > * Namhyung Kim <namhyung@...nel.org> wrote:
> >
> >> Hi Ingo,
> >> 
> >> On Tue, 5 Nov 2013 12:58:02 +0100, Ingo Molnar wrote:
> >> > * Namhyung Kim <namhyung@...nel.org> wrote:
> >> >> But the 'cumulative' (btw, I feel a bit hard to type this word..) is 
> >> >> different in that it *generates* entries didn't get sampled originally. 
> >> >> And as it requires callchains, total field will not work if callchains 
> >> >> are missing.
> >> >
> >> > Well, 'total' should disappear if it's not available.
> >> 
> >> But what if it's the only sort key user gave?
> >
> > Do you mean something like:
> >
> >   -F self,name -s total
> >
> > i.e. if a sort key not displayed?
> 
> What I worry is when no -F option was given at all.

In that case the default list applied, plus whatever new fields are 
mentioned in -s would also be added (appended or prepended).

The display order of columns should _probably_ be something like:

  key1 key2 ... non-key1 non-key2

there's not much point in sorting and then displaying the key not in 
front, right?

> > I think sort keys should be automatically added to the displayed 
> > fields list.
> 
> Agreed.

> > This problem should be solved if all -s fields are displayed - i.e. 
> > they are added to the -F list, right?
> 
> But old users might not aware of the new -F option, and use -s option 
> only.  If so, she will get output like the first example, right?

Well, there's a default -F list that applies - so this shouldn't be a 
problem, agreed? So output should be like the second (expected) example.

> > Basically there's just a single concept: the -F list. The -s option 
> > simply modifies and extends the -F list but internally perf report 
> > would not know anything about '-s', it only knows about fields to 
> > display and it would know which of those fields are to be sorted and 
> > in what order.
> >
> > Does that make sense to you? Does it cover everything needed?
> 
> I like the concept.  I'm just looking for a way to add it without 
> upsetting old users. :)

If the default -F list matches our current displayed fields list then 
there should not be much change in behavior (beyond the addition of total 
for call-graph outputs - which can be kept completely separate).

I'm not too worried about call-graph 'legacies': it generates such huge 
perf.data files which is parsed so slowly at the moment that there's very 
little user base ... Anyone who absolutely needs call-graph profiling uses 
SysProf which performs well.

Thanks,

	Ingo
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