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

From: Brendan Gregg
Date: Mon Nov 02 2015 - 15:38:07 EST

G'Day Namhyung,

On Mon, Nov 2, 2015 at 4:57 AM, Namhyung Kim <namhyung@xxxxxxxxxx> 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


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
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).

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