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

Ingo Molnar
2013-11-06T11:47:07Z

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

> On Wed, 6 Nov 2013 09:30:46 +0100, Ingo Molnar wrote:
> > * Namhyung Kim <namhyung@kernel.org> wrote:
> >
> >> Hi Ingo,
> >>
> >> On Tue, 5 Nov 2013 12:58:02 +0100, Ingo Molnar wrote:
> >> > * Namhyung Kim <namhyung@kernel.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