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Date: Fri, 10 Feb 2012 12:07:26 -0800
From: Arun Sharma <asharma@fb.com>
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To: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Frederic Weisbecker <fweisbec@gmail.com>, <linux-kernel@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Andrew Vagin <avagin@openvz.org>, Ingo Molnar <mingo@elte.hu>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] trace: reset sleep/block start time on task switch
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On 2/10/12 10:43 AM, Peter Zijlstra wrote:
> On Wed, 2012-01-25 at 11:50 -0800, Arun Sharma wrote:
>> # perf record -agP -e sched:sched_switch --filter "prev_state == 1 ||
>> prev_state == 2" -e  sched:sched_stat_sleep -- sleep 3
>
> Problem with that is it'll try and do a backtrace for all events, not
> only the sched_switch but also sched_stat_sleep, which is completely
> superfluous (and expensive).
>
> Currently perf tool doesn't support individual -g flags though and its
> slightly non-trivial to make it so. Easiest work-around would be two
> records and then merge the two files.

If we have a sequence of:

SL1, SW1, SL2, SW2, SL3, SW3

I think you're suggesting:

perf.data1: SL1, SL2, SL3 (without -g)
perf.data2: SW1, SW2, SW3 (with -g)

and then munge the data to create perf.data. But making sure that all 
matching sleep and switch events are captured seems hard.

  -Arun