linux-kernel - [RFC PATCH v4 6/7] perf sched: prefer to use prev_state_char introduced in sched

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Date:   Wed,  2 Aug 2023 08:10:01 -0400
From:   Ze Gao <zegao2021@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org, Ze Gao <zegao@...cent.com>
Subject: [RFC PATCH v4 6/7] perf sched: prefer to use prev_state_char introduced in sched_switch

Since the sched_switch tracepoint introduces a new variable to
report sched-out task state in symbolic char, we prefer to use
it to spare from knowing internal implementations in kernel.

Also we keep the old parsing logic intact but sync the state char
array with the latest kernel.

Signed-off-by: Ze Gao <zegao@...cent.com>
---
 tools/perf/builtin-sched.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index eb310d1a7625..7f76ba51e36d 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -837,7 +837,7 @@ replay_wakeup_event(struct perf_sched *sched,
 
 static inline char task_state_char(int state)
 {
-	static const char state_to_char[] = "RSDTtXZPI";
+	static const char state_to_char[] = "RSDTtXZPIp";
 	unsigned bit = state ? ffs(state) : 0;
 	return bit < sizeof(state_to_char) - 1 ? state_to_char[bit] : '?';
 }
@@ -845,8 +845,20 @@ static inline char task_state_char(int state)
 static inline char get_task_prev_state(struct evsel *evsel,
 				       struct perf_sample *sample)
 {
-	const int prev_state = evsel__intval(evsel, sample, "prev_state");
-	return task_state_char(prev_state);
+	char prev_state_char;
+	int prev_state;
+
+	//prefer to use prev_state_char
+	if (evsel__field(evsel, "prev_state_char"))
+		prev_state_char = (char) evsel__intval(evsel,
+				sample, "prev_state_char");
+	else {
+		prev_state = (int) evsel__intval(evsel,
+				sample, "prev_state");
+		prev_state_char = task_state_char(prev_state);
+	}
+
+	return prev_state_char;
 }
 
 static int replay_switch_event(struct perf_sched *sched,
@@ -2143,7 +2155,7 @@ static void timehist_update_runtime_stats(struct thread_runtime *r,
 		else if (r->last_time) {
 			u64 dt_wait = tprev - r->last_time;
 
-			if (r->last_state == 'R')
+			if (r->last_state == 'R' || r->last_state == 'p')
 				r->dt_preempt = dt_wait;
 			else if (r->last_state == 'D')
 				r->dt_iowait = dt_wait;
-- 
2.41.0