From: Arun Sharma <asharma@fb.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <linux-kernel@vger.kernel.org>,
Arnaldo Carvalho de Melo <acme@infradead.org>,
Andrew Vagin <avagin@openvz.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH] trace: reset sleep/block start time on task switch
Date: Tue, 24 Jan 2012 13:46:52 -0800 [thread overview]
Message-ID: <4F1F26CC.4040109@fb.com> (raw)
In-Reply-To: <1327415255.2614.33.camel@laptop>
On 1/24/12 6:27 AM, Peter Zijlstra wrote:
> Bah, you're right. Also yes your proposal is too intrusive, but that can
> be fixed, I actually did, but then I noticed its broken too, it doesn't
> matter if the schedule that schedules a task back in preempted another
> task or not, what matters is if the task we're scheduling back in was
> itself preempted or recently woken. And we simply don't know.
Yes - we'd need an extra bit in the task_struct to do this right.
> I'm tempted to revert 1ac9bc69 for now, userspace will simply have to
> correlate trace_sched_switch() and trace_sched_stat_{sleep,blocked}(),
> which shouldn't be too hard.
We tried it and it didn't work very well. Especially when used with perf
record -g. There are too many uninteresting trace_sched_switch() events.
Other possibilites: make a copy of {sleep,block}_start somewhere else in
the perf_events subsystem in the sleep/wakeup path and leave
sched_statistics untouched.
-Arun
next prev parent reply other threads:[~2012-01-24 21:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 2:20 [PATCH] trace: reset sleep/block start time on task switch Arun Sharma
2012-01-23 11:34 ` Peter Zijlstra
2012-01-23 18:41 ` Arun Sharma
2012-01-23 21:03 ` Peter Zijlstra
2012-01-23 23:02 ` Arun Sharma
2012-01-24 14:27 ` Peter Zijlstra
2012-01-24 21:46 ` Arun Sharma [this message]
2012-01-25 9:20 ` Frederic Weisbecker
2012-01-25 19:50 ` Arun Sharma
2012-01-25 20:15 ` Steven Rostedt
2012-01-25 22:29 ` Arun Sharma
2012-01-26 2:27 ` Frederic Weisbecker
2012-01-26 19:13 ` Arun Sharma
2012-01-26 2:21 ` Frederic Weisbecker
2012-02-10 18:43 ` Peter Zijlstra
2012-02-10 20:07 ` Arun Sharma
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