It's possible some of the counters in the group could be disabled when sampling member of the event group is reading the rest via PERF_SAMPLE_READ sample type processing. Disabled counters could then produce wrong numbers.
Fixing that by reading only enabled counters for PERF_SAMPLE_READ sample type processing. Signed-off-by: Jiri Olsa <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Corey Ashford <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Namhyung Kim <[email protected]> --- kernel/events/core.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 32aec40..5220d01 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4012,12 +4012,24 @@ static void perf_output_read_group(struct perf_output_handle *handle, __output_copy(handle, values, n * sizeof(u64)); list_for_each_entry(sub, &leader->sibling_list, group_entry) { + u64 value = 0; n = 0; - if (sub != event) - sub->pmu->read(sub); + /* + * We are NOT interested in disabled counters, + * giving us strange values and keeping us from + * good night sleep!!! + */ + if (sub->state > PERF_EVENT_STATE_OFF) { + + if (sub != event) + sub->pmu->read(sub); + + value = perf_event_count(sub); + } + + values[n++] = value; - values[n++] = perf_event_count(sub); if (read_format & PERF_FORMAT_ID) values[n++] = primary_event_id(sub); -- 1.7.11.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
