This is a note to let you know that I've just added the patch titled
perf sched timehist: Fixed timestamp error when unable to confirm event sched_in time
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-sched-timehist-fixed-timestamp-error-when-unabl.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 9488e25cbecacbcf7a90b4f16720333cd9a8871f
Author: Yang Jihong <yangjihong@xxxxxxxxxxxxx>
Date: Mon Aug 19 10:47:20 2024 +0800
perf sched timehist: Fixed timestamp error when unable to confirm event sched_in time
[ Upstream commit 39c243411bdb8fb35777adf49ee32549633c4e12 ]
If sched_in event for current task is not recorded, sched_in timestamp
will be set to end_time of time window interest, causing an error in
timestamp show. In this case, we choose to ignore this event.
Test scenario:
perf[1229608] does not record the first sched_in event, run time and sch delay are both 0
# perf sched timehist
Samples of sched_switch event do not have callchains.
time cpu task name wait time sch delay run time
[tid/pid] (msec) (msec) (msec)
--------------- ------ ------------------------------ --------- --------- ---------
2090450.763231 [0000] perf[1229608] 0.000 0.000 0.000
2090450.763235 [0000] migration/0[15] 0.000 0.001 0.003
2090450.763263 [0001] perf[1229608] 0.000 0.000 0.000
2090450.763268 [0001] migration/1[21] 0.000 0.001 0.004
2090450.763302 [0002] perf[1229608] 0.000 0.000 0.000
2090450.763309 [0002] migration/2[27] 0.000 0.001 0.007
2090450.763338 [0003] perf[1229608] 0.000 0.000 0.000
2090450.763343 [0003] migration/3[33] 0.000 0.001 0.004
Before:
arbitrarily specify a time window of interest, timestamp will be set to an incorrect value
# perf sched timehist --time 100,200
Samples of sched_switch event do not have callchains.
time cpu task name wait time sch delay run time
[tid/pid] (msec) (msec) (msec)
--------------- ------ ------------------------------ --------- --------- ---------
200.000000 [0000] perf[1229608] 0.000 0.000 0.000
200.000000 [0001] perf[1229608] 0.000 0.000 0.000
200.000000 [0002] perf[1229608] 0.000 0.000 0.000
200.000000 [0003] perf[1229608] 0.000 0.000 0.000
200.000000 [0004] perf[1229608] 0.000 0.000 0.000
200.000000 [0005] perf[1229608] 0.000 0.000 0.000
200.000000 [0006] perf[1229608] 0.000 0.000 0.000
200.000000 [0007] perf[1229608] 0.000 0.000 0.000
After:
# perf sched timehist --time 100,200
Samples of sched_switch event do not have callchains.
time cpu task name wait time sch delay run time
[tid/pid] (msec) (msec) (msec)
--------------- ------ ------------------------------ --------- --------- ---------
Fixes: 853b74071110bed3 ("perf sched timehist: Add option to specify time window of interest")
Signed-off-by: Yang Jihong <yangjihong@xxxxxxxxxxxxx>
Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: David Ahern <dsa@xxxxxxxxxxxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: James Clark <james.clark@xxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240819024720.2405244-1-yangjihong@xxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 1c9e06c1d0089..cf8dc3910ef21 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -2553,9 +2553,12 @@ static int timehist_sched_change_event(struct perf_tool *tool,
* - previous sched event is out of window - we are done
* - sample time is beyond window user cares about - reset it
* to close out stats for time window interest
+ * - If tprev is 0, that is, sched_in event for current task is
+ * not recorded, cannot determine whether sched_in event is
+ * within time window interest - ignore it
*/
if (ptime->end) {
- if (tprev > ptime->end)
+ if (!tprev || tprev > ptime->end)
goto out;
if (t > ptime->end)
