Re: perf record of multiple events: disable callgraph for some events

[Milian Wolff <milian.wolff@kdab.com>]

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On Sonntag, 4. Oktober 2015 17:40:59 CEST Arnaldo Carvalho de Melo wrote:
> Em Sun, Oct 04, 2015 at 01:48:21PM +0200, Milian Wolff escreveu:
> > Hey all,
> > 
> > would it be possible to add a feature to perf to only grab callgraphs for
> > a
> > certain selection of events? E.g. thinking about a lock contention profile
> > of a Qt application, I'd listen to
> > 
> > -e syscalls:sys_enter_futex,syscalls:sys_exit_futex
> > 
> > Now, with the dwarf unwinder this easily produces huge data files in the
> > order of gigabytes. This cost could easily be reduced by a factor of two,
> > as one only needs the callgraphs for syscalls:sys_enter_futex - the TID
> > should be enough to find the callgraph for the enter event from the exit
> > trace point.
> > 
> > Could someone guide me in implementing such a feature to make it possible
> > to filter the events which trigger the collection of a callgraph? Or is
> > that already possible somehow?
> 
> Can you please check if this suits you, it is already in the tree:
> 
> commit e637d17757a10732fa5d573c18f20b3cd4d31245
> Author: He Kuang <hekuang@huawei.com>
> Date:   Mon Sep 28 03:52:16 2015 +0000

<snip>

Perfect, Thanks Arnaldo for pointing me in that direction, and many thanks to 
He for implementing it! Works like a charm.

Does anyone have a suggestion on where to put documentation for this? I'll try 
to add that then next week, together with the other stuff I've noticed and 
couldn't find before. Otherwise, I'll put it into the docs for `perf record`'s 
`--call-graph`.

Cheers

-- 
Milian Wolff | milian.wolff@kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts

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