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Date: Thu, 26 Jan 2012 03:21:31 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: Arun Sharma <asharma@...com> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>, 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, Jan 25, 2012 at 11:50:53AM -0800, Arun Sharma wrote: > On 1/25/12 1:20 AM, Frederic Weisbecker wrote: > > >>>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. > > > >You mean context switches happening when the prev task doesn't need > >to block or so? As it happens with preemption for example? > > > >In this case you can use filters to drop context switches for > >which the prev state is not S or D. > > We had these filters and still couldn't keep up: > > # perf record -agP -e sched:sched_switch --filter "prev_state == 1 > || prev_state == 2" -e sched:sched_stat_sleep -- sleep 3 > [ perf record: Woken up 107 times to write data ] > [ perf record: Captured and wrote 32.629 MB perf.data (~1425585 samples) ] > Warning: > Processed 104066 events and lost 4 chunks! > > Check IO/CPU overload! Have you tried to tweak the -m options to increase the size of the buffer? > > -Arun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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