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

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Date:	Mon, 2 Nov 2015 18:30:21 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Brendan Gregg <brendan.d.gregg@...il.com>
Cc:	Namhyung Kim <namhyung@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jiri Olsa <jolsa@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Kan Liang <kan.liang@...el.com>
Subject: Re: [RFC/PATCH 0/4] perf report: Support folded callchain output (v2)

Em Mon, Nov 02, 2015 at 12:37:28PM -0800, Brendan Gregg escreveu:
> G'Day Namhyung,
> 
> On Mon, Nov 2, 2015 at 4:57 AM, Namhyung Kim <namhyung@...nel.org> wrote:
> > Hello,
> >
> > This is what Brendan requested on the perf-users mailing list [1] to
> > support FlameGraphs [2] more efficiently.  This patchset adds a few
> > more callchain options to adjust the output for it.
> >
> > At first, 'folded' output mode was added.  The folded output puts all
> > calchain nodes in a line separated by semicolons, a space and the
> > value.  Now it only supports --stdio as other UI provides some way of
> > folding/expanding callchains dynamically.
> >
> > The value is now can be one of 'percent', 'period', or 'count'.  The
> > percent is current default output and the period is the raw number of
> > sample periods.  The count is the number of samples for each callchain.
> >
> > Here's an example:
> >
> >   $ perf report --no-children --show-nr-samples --stdio -g folded,count
> >   ...
> >     39.93%     80  swapper  [kernel.vmlinux]  [k] intel_idel
> >   intel_idle;cpuidle_enter_state;cpuidle_enter;call_cpuidle;cpu_startup_entry;start_secondary 57
> >   intel_idle;cpuidle_enter_state;cpuidle_enter;call_cpuidle;cpu_startup_entry;rest_init;... 23
> 
> Thanks!
> 
> So for the folded output I don't need the summary line (the row of
> columns printed by hist_entry__snprintf()), and don't need anything
> except folded stacks and the counts. If working with the existing
> stdio interface is making it harder than it needs to be, might it be

I don't think it so, just add some flag asking for that
hist_entry__snprintf() to be supressed, ideas for a long option name?

Having it as Namhyung did may have value for some people as a more
compact way to show the callchains together with the hist_entry line.

With this in mind, do you have any other issues with Namhyung's
patchkit? An acked-by/tested-by you would be nice to have, and then we
could work out the new option to suppress that hist_entry__snprintf()
in a follow up patch.

> easier to make it a separate interface (ui/folded), that just emitted
> the folded output? Just an idea. This existing patchset is working for
> me, I'd just be filtering the output.
> 
> Having the option for percentages and periods is nice. I can envisage
> using periods (for latency flame graphs).

You mean in the callchain lines?

- Arnaldo
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