linux-kernel - [PATCH 6/6] perf lock: Carefully combine lock stats for discarded entries

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Date:   Wed, 26 Jan 2022 16:00:50 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 6/6] perf lock: Carefully combine lock stats for discarded entries

Stats from discarded entries should be omitted.  But a lock class may
have both good and bad entries.  If the first entry was bad, we can
zero-fill the stats and only add good stats if any.  The entry can
remove the discard state if it finds a good entry later.

Acked-by: Jiri Olsa <jolsa@...hat.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-lock.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index bbfeba79426a..57b9ebd7118a 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -295,6 +295,9 @@ static void combine_lock_stats(struct lock_stat *st)
 			ret = !!st->name - !!p->name;
 
 		if (ret == 0) {
+			if (st->discard)
+				goto out;
+
 			p->nr_acquired += st->nr_acquired;
 			p->nr_contended += st->nr_contended;
 			p->wait_time_total += st->wait_time_total;
@@ -307,6 +310,10 @@ static void combine_lock_stats(struct lock_stat *st)
 			if (p->wait_time_max < st->wait_time_max)
 				p->wait_time_max = st->wait_time_max;
 
+			/* now it got a new !discard record */
+			p->discard = 0;
+
+out:
 			st->combined = 1;
 			return;
 		}
@@ -319,6 +326,15 @@ static void combine_lock_stats(struct lock_stat *st)
 
 	rb_link_node(&st->rb, parent, rb);
 	rb_insert_color(&st->rb, &sorted);
+
+	if (st->discard) {
+		st->nr_acquired = 0;
+		st->nr_contended = 0;
+		st->wait_time_total = 0;
+		st->avg_wait_time = 0;
+		st->wait_time_min = ULLONG_MAX;
+		st->wait_time_max = 0;
+	}
 }
 
 static void insert_to_result(struct lock_stat *st,
-- 
2.35.0.rc0.227.g00780c9af4-goog