linux-kernel - Re: [PATCH 3/4] trace: add ability to collect call chain of non-current task.

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Message-ID: <4EEA8DB1.6060505@fb.com>
Date:	Thu, 15 Dec 2011 16:15:45 -0800
From:	Arun Sharma <asharma@...com>
To:	<avagin@...il.com>
CC:	<avagin@...nvz.org>, Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	<linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH 3/4] trace: add ability to collect call chain of non-current
 task.

On 12/15/11 11:08 AM, Arun Sharma wrote:

> I still need to investigate why per-process mode (command line without
> -a) doesn't work. Will send an updated patch once that's fixed.
>

The per-process mode works fine after moving the trace point to be after:

         perf_event_task_sched_in(prev, current);

App developers using this feature here say they're fine not having the 
block vs sleep distinction because they intend to use it with "-g" and 
the callstack makes it obvious which one it was.

If we really need this info, we should be able to derive it in user 
space via perf inject.

  -Arun
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