linux-kernel - Re: [PATCH] trace: reset sleep/block start time on task switch

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Message-ID: <1328899383.25989.40.camel@laptop>
Date:	Fri, 10 Feb 2012 19:43:03 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Arun Sharma <asharma@...com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Andrew Vagin <avagin@...nvz.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] trace: reset sleep/block start time on task switch

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.

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