perf stat: Fix event grouping on forked task

When event group is enabled for forked task (i.e. no target task was
specified) all events were disabled and marked ->enable_on_exec.
However they are not counted at all since only group leader will be
enabled on exec actually. So the result looked like below:

 $ ./perf stat --group -- sleep 1

 Performance counter stats for 'sleep 1':

          0.554926 task-clock                #    0.001 CPUs utilized
     <not counted> context-switches
     <not counted> CPU-migrations
     <not counted> page-faults
     <not counted> cycles
   <not supported> stalled-cycles-frontend
   <not supported> stalled-cycles-backend
     <not counted> instructions
     <not counted> branches
     <not counted> branch-misses

       1.001228093 seconds time elapsed

Fix it by disabling group leader only.

Cc: Ingo Molnar <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index ea40e4e8b2271f0a7a53ee25d8154cdcee4b19bd..c941bb640f4990f8590f8fb410dfaa0247bcc3b8 100644 (file)
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -296,7 +296,7 @@ static int create_perf_stat_counter(struct perf_evsel *evsel,
        if (system_wide)
                return perf_evsel__open_per_cpu(evsel, evsel_list->cpus,
                                                group, group_fd);
-       if (!target_pid && !target_tid) {
+       if (!target_pid && !target_tid && (!group || evsel == first)) {
                attr->disabled = 1;
                attr->enable_on_exec = 1;
        }