linux-kernel - [PATCH v4 10/15] sched: Add task enqueue/dequeue trace points

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Message-ID: <20260116123911.130300-11-gmonaco@redhat.com>
Date: Fri, 16 Jan 2026 13:39:06 +0100
From: Gabriele Monaco <gmonaco@...hat.com>
To: linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Nam Cao <namcao@...utronix.de>,
	Juri Lelli <jlelli@...hat.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-trace-kernel@...r.kernel.org
Cc: Gabriele Monaco <gmonaco@...hat.com>,
	Tomas Glozar <tglozar@...hat.com>,
	Clark Williams <williams@...hat.com>,
	John Kacur <jkacur@...hat.com>
Subject: [PATCH v4 10/15] sched: Add task enqueue/dequeue trace points

From: Nam Cao <namcao@...utronix.de>

Add trace points into enqueue_task() and dequeue_task().

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Nam Cao <namcao@...utronix.de>
Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
---
 include/trace/events/sched.h | 13 +++++++++++++
 kernel/sched/core.c          |  9 ++++++++-
 kernel/sched/sched.h         |  2 ++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 366b2e8ec40c..f4e1d3554e3e 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -912,6 +912,19 @@ DECLARE_TRACE(sched_dl_server_stop,
 	TP_PROTO(struct sched_dl_entity *dl_se, int cpu),
 	TP_ARGS(dl_se, cpu));
 
+/*
+ * The two trace points below may not work as expected for fair tasks due
+ * to delayed dequeue. See:
+ * https://lore.kernel.org/lkml/179674c6-f82a-4718-ace2-67b5e672fdee@amd.com/
+ */
+DECLARE_TRACE(sched_enqueue,
+	TP_PROTO(struct task_struct *tsk, int cpu),
+	TP_ARGS(tsk, cpu));
+
+DECLARE_TRACE(sched_dequeue,
+	TP_PROTO(struct task_struct *tsk, int cpu),
+	TP_ARGS(tsk, cpu));
+
 #endif /* _TRACE_SCHED_H */
 
 /* This part must be outside protection */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f6293fa02fb7..8958c013fb2c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2087,6 +2087,8 @@ unsigned long get_wchan(struct task_struct *p)
 
 void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
 {
+	trace_sched_enqueue_tp(p, rq->cpu);
+
 	if (!(flags & ENQUEUE_NOCLOCK))
 		update_rq_clock(rq);
 
@@ -2114,6 +2116,8 @@ void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
  */
 inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 {
+	int ret;
+
 	if (sched_core_enabled(rq))
 		sched_core_dequeue(rq, p, flags);
 
@@ -2131,7 +2135,10 @@ inline bool dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 	 */
 	uclamp_rq_dec(rq, p);
 	rq->queue_mask |= p->sched_class->queue_mask;
-	return p->sched_class->dequeue_task(rq, p, flags);
+	ret = p->sched_class->dequeue_task(rq, p, flags);
+	if (trace_sched_dequeue_tp_enabled() && !(flags & DEQUEUE_SLEEP))
+		trace_sched_dequeue_tp(p, rq->cpu);
+	return ret;
 }
 
 void activate_task(struct rq *rq, struct task_struct *p, int flags)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e885a935b716..8465472b40fa 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2918,6 +2918,8 @@ static inline void sub_nr_running(struct rq *rq, unsigned count)
 
 static inline void __block_task(struct rq *rq, struct task_struct *p)
 {
+	trace_sched_dequeue_tp(p, rq->cpu);
+
 	if (p->sched_contributes_to_load)
 		rq->nr_uninterruptible++;
 
-- 
2.52.0