[PATCH 2/2] perf sched timehist: Fix invalid runtime in the idle hist

Namhyung Kim
2016-12-13T08:07:54Z

When --idle-hist option is used, run/wait time and sched delay value
should be shown for idle task only. But due to internal accounting, a
last thread has same value of next idle task's and it was shown.

In the below example, firefox after idle task has same run time of
idle task's.

$ perf sched timehist --idle-hist
Samples do not have callchains.
time cpu task name wait time sch delay run time
[tid/pid] (msec) (msec) (msec)
--------------- ------ -------------------- --------- --------- ---------
197731.754335 [0002] firefox[17773/17739] 0.000 0.000 0.000
197731.754486 [0001] sleep[27470] 0.000 0.000 0.000
197731.754903 [0002] <idle> 0.047 0.000 0.567
197731.754981 [0002] firefox[17773/17739] 0.000 0.000 0.567
197731.755922 [0002] <idle> 0.078 0.000 0.941
197731.755994 [0002] firefox[17773/17739] 0.000 0.000 0.941
<SNIP>

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-sched.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 405a91d0515f..64a0959bccd7 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -2439,6 +2439,15 @@ static int timehist_sched_change_event(struct perf_tool *tool,
goto out;

timehist_update_runtime_stats(last_tr, t, tprev);
+ /*
+ * remove delta time of last thread as it's not updated
+ * and otherwise it will show an invalid value next
+ * time. we only care total run time and run stat.
+ */
+ last_tr->dt_run = 0;
+ last_tr->dt_wait = 0;
+ last_tr->dt_delay = 0;
+
if (itr->cursor.nr)
callchain_append(&itr->callchain, &itr->cursor,
t - tprev);
--
2.10.2