From 39c243411bdb8fb35777adf49ee32549633c4e12 Mon Sep 17 00:00:00 2001 From: Yang Jihong Date: Mon, 19 Aug 2024 10:47:20 +0800 Subject: [PATCH] perf sched timehist: Fixed timestamp error when unable to confirm event sched_in time 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 Acked-by: Namhyung Kim Cc: Adrian Hunter Cc: Alexander Shishkin Cc: David Ahern Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jiri Olsa Cc: Kan Liang Cc: Mark Rutland Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20240819024720.2405244-1-yangjihong@bytedance.com Signed-off-by: Arnaldo Carvalho de Melo --- 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) -- 2.50.1