[tip: perf/core] perf: Only dump the throttle log for the leader

["tip-bot2 for Kan Liang" <tip-bot2@linutronix.de>]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     e800ac51202f053018f3d6acb1819ecec4d75a2c
Gitweb:        https://git.kernel.org/tip/e800ac51202f053018f3d6acb1819ecec4d75a2c
Author:        Kan Liang <kan.liang@linux.intel.com>
AuthorDate:    Tue, 20 May 2025 11:16:30 -07:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 21 May 2025 13:57:43 +02:00

perf: Only dump the throttle log for the leader

The PERF_RECORD_THROTTLE records are dumped for all throttled events.
It's not necessary for group events, which are throttled altogether.

Optimize it by only dump the throttle log for the leader.

The sample right after the THROTTLE record must be generated by the
actual target event. It is good enough for the perf tool to locate the
actual target event.

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250520181644.2673067-3-kan.liang@linux.intel.com
---
 kernel/events/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8327ab0..f34c99f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2650,14 +2650,16 @@ static void perf_event_unthrottle(struct perf_event *event, bool start)
 	event->hw.interrupts = 0;
 	if (start)
 		event->pmu->start(event, 0);
-	perf_log_throttle(event, 1);
+	if (event == event->group_leader)
+		perf_log_throttle(event, 1);
 }
 
 static void perf_event_throttle(struct perf_event *event)
 {
 	event->pmu->stop(event, 0);
 	event->hw.interrupts = MAX_INTERRUPTS;
-	perf_log_throttle(event, 0);
+	if (event == event->group_leader)
+		perf_log_throttle(event, 0);
 }
 
 static void perf_event_unthrottle_group(struct perf_event *event, bool skip_start_event)