From: Yang Jihong <yangjihong@bytedance.com>
To: peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
namhyung@kernel.org, mark.rutland@arm.com,
alexander.shishkin@linux.intel.com, jolsa@kernel.org,
irogers@google.com, adrian.hunter@intel.com,
kan.liang@linux.intel.com, james.clark@arm.com,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: yangjihong@bytedance.com
Subject: [PATCH v2] perf sched timehist: Fixed timestamp error when unable to confirm event sched_in time
Date: Mon, 19 Aug 2024 10:47:20 +0800 [thread overview]
Message-ID: <20240819024720.2405244-1-yangjihong@bytedance.com> (raw)
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: 853b74071110 ("perf sched timehist: Add option to specify time window of interest")
Signed-off-by: Yang Jihong <yangjihong@bytedance.com>
---
Changes since v1:
- Simplify conditional judgment. (suggested-by Namhyung)
tools/perf/builtin-sched.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 9c1276dc8ef6..1c386ebe4b98 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -2683,9 +2683,12 @@ static int timehist_sched_change_event(const 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)
--
2.25.1
next reply other threads:[~2024-08-19 2:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-19 2:47 Yang Jihong [this message]
2024-08-19 20:08 ` [PATCH v2] perf sched timehist: Fixed timestamp error when unable to confirm event sched_in time Namhyung Kim
2024-08-30 13:32 ` Arnaldo Carvalho de Melo
2024-08-20 18:00 ` Madadi Vineeth Reddy
[not found] ` <CAPePreJCahzH0LwfXN_X+UdxU54_UMRPZgDgGqt7+PC+ky997Q@mail.gmail.com>
2024-08-21 10:28 ` Madadi Vineeth Reddy
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