linux-kernel - [PATCH v3] perf sched: Fix sched latency analysis incorrect

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Date:   Fri, 17 Mar 2023 14:32:50 +0800
From:   "Chunxin Zang" <zangchunxin@...iang.com>
To:     <namhyung@...nel.org>, <peterz@...radead.org>, <mingo@...hat.com>,
        <acme@...nel.org>
Cc:     <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...nel.org>, <irogers@...gle.com>,
        <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Chunxin Zang" <zangchunxin@...iang.com>,
        "Jerry Zhou" <zhouchunhua@...iang.com>
Subject: [PATCH v3] perf sched: Fix sched latency analysis incorrect

'perf sched latency' is incorrect to get process schedule latency
when it used 'sched:sched_wakeup' to analysis perf.data.

Because 'perf record' prefer use 'sched:sched_waking' to
'sched:sched_wakeup' since commit d566a9c2d482 ("perf sched: Prefer
sched_waking event when it exists"). It's very reasonable to
evaluate process schedule latency.

Similarly, update sched latency/map/replay to use sched_waking events.

I used 'perf record -e "sched:* "' to record both wakeup and waking events,
and use fixed perf version to analysis them, the result is correct.
Because the function "latency_wakeup_event" will change atom->state to
THREAD_WAIT_CPU at waking event, and judge the 'atom->state !=
THREAD_SLEEPING' is false then returned at wakeup event.

Signed-off-by: Chunxin Zang <zangchunxin@...iang.com>
Signed-off-by: Jerry Zhou <zhouchunhua@...iang.com>
---

	changelogs in v3:
	1) fix non-ASCII characters in commit log.

	changelogs in v2:
	1) fix email address disappearing in 'signed off by'

 tools/perf/builtin-sched.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 86e18575c9be..1af4ec1ac824 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -1819,6 +1819,7 @@ static int perf_sched__read_events(struct perf_sched *sched)
 	const struct evsel_str_handler handlers[] = {
 		{ "sched:sched_switch",	      process_sched_switch_event, },
 		{ "sched:sched_stat_runtime", process_sched_runtime_event, },
+		{ "sched:sched_waking",	      process_sched_wakeup_event, },
 		{ "sched:sched_wakeup",	      process_sched_wakeup_event, },
 		{ "sched:sched_wakeup_new",   process_sched_wakeup_event, },
 		{ "sched:sched_migrate_task", process_sched_migrate_task_event, },
-- 
2.25.1

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