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

From: Namhyung Kim
Date: Mon Nov 02 2015 - 22:17:33 EST


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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/