Commit 58b32c1b authored Jul 27, 2015 by Arnaldo Carvalho de Melo

perf python: Make twatch.py use soft dummy event, freq=0



To not sample, what we want are just the PERF_RECORD_ lifetime events
for threads, using the default, PERF_TYPE_HARDWARE +
PERF_COUNT_HW_CYCLES and freq=1 (the default), makes perf reenable
irq_vectors:local_timer_entry, disabling nohz, not good for some use
cases where all we want is to get notifications when threads comes and
goes...

Fix it by using PERF_TYPE_SOFTWARE (no counter rotation) and
PERF_COUNT_SW_DUMMY (created by Adrian so that we could have access to
those PERF_RECORD_ goodies).

Reported-by: Luiz Fernando Capitulino <lcapitulino@redhat.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jaroslav Skarvada <jskarvad@redhat.com>
Cc: Jeremy Eder <jeder@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-kfsijirfrs6xfhkcdxeoen06@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 84576da2

tools/perf/python/twatch.py

+11 −1

Original line number	Diff line number	Diff line
		@@ -18,10 +18,20 @@ import perf
		def main():
		cpus = perf.cpu_map()
		threads = perf.thread_map()
		evsel = perf.evsel(task = 1, comm = 1, mmap = 0,
		evsel = perf.evsel(type = perf.TYPE_SOFTWARE,
		config = perf.COUNT_SW_DUMMY,
		task = 1, comm = 1, mmap = 0, freq = 0,
		wakeup_events = 1, watermark = 1,
		sample_id_all = 1,
		sample_type = perf.SAMPLE_PERIOD \| perf.SAMPLE_TID \| perf.SAMPLE_CPU)

		"""What we want are just the PERF_RECORD_ lifetime events for threads,
		using the default, PERF_TYPE_HARDWARE + PERF_COUNT_HW_CYCLES & freq=1
		(the default), makes perf reenable irq_vectors:local_timer_entry, when
		disabling nohz, not good for some use cases where all we want is to get
		threads comes and goes... So use (perf.TYPE_SOFTWARE, perf_COUNT_SW_DUMMY,
		freq=0) instead."""

		evsel.open(cpus = cpus, threads = threads);
		evlist = perf.evlist(cpus, threads)
		evlist.add(evsel)

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