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

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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 <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jaroslav Skarvada <[email protected]>
Cc: Jeremy Eder <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
This commit is contained in:
Arnaldo Carvalho de Melo 2015-07-27 17:13:21 -03:00
commit 58b32c1b53
1 changed files with 11 additions and 1 deletions
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12
tools/perf/python/twatch.py
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@ -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)