linux-kernel - [RFC PATCH V2] sched: psi: Add psi events trace point

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Message-ID: <20250820112621.4045-1-xuewen.yan@unisoc.com>
Date: Wed, 20 Aug 2025 19:26:21 +0800
From: Xuewen Yan <xuewen.yan@...soc.com>
To: <hannes@...xchg.org>, <surenb@...gle.com>, <peterz@...radead.org>,
        <mathieu.desnoyers@...icios.com>, <mhiramat@...nel.org>,
        <rostedt@...dmis.org>, <mingo@...hat.com>
CC: <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <dietmar.eggemann@....com>, <bsegall@...gle.com>, <mgorman@...e.de>,
        <vschneid@...hat.com>, <linux-kernel@...r.kernel.org>,
        <linux-trace-kernel@...r.kernel.org>, <ke.wang@...soc.com>,
        <yuming.han@...soc.com>, <xuewen.yan94@...il.com>
Subject: [RFC PATCH V2] sched: psi: Add psi events trace point

Add trace point to psi triggers. This is useful to
observe the psi events in the kernel space.

One use of this is to monitor memory pressure.
When the pressure is too high, we can kill the process
in the kernel space to prevent OOM.

Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
---
v2:
-fix compilation error;
-export the tp;
-add more commit message;
---
 include/trace/events/sched.h | 5 +++++
 kernel/sched/psi.c           | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 7b2645b50e78..d54db5fcbca2 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -896,6 +896,11 @@ DECLARE_TRACE(sched_set_need_resched,
 	TP_PROTO(struct task_struct *tsk, int cpu, int tif),
 	TP_ARGS(tsk, cpu, tif));
 
+struct psi_trigger;
+DECLARE_TRACE(psi_event,
+	TP_PROTO(struct psi_trigger *t),
+	TP_ARGS(t));
+
 #endif /* _TRACE_SCHED_H */
 
 /* This part must be outside protection */
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 59fdb7ebbf22..f06eb91a1250 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -141,6 +141,8 @@
 #include <linux/psi.h>
 #include "sched.h"
 
+EXPORT_TRACEPOINT_SYMBOL_GPL(psi_event_tp);
+
 static int psi_bug __read_mostly;
 
 DEFINE_STATIC_KEY_FALSE(psi_disabled);
@@ -509,6 +511,8 @@ static void update_triggers(struct psi_group *group, u64 now,
 		if (now < t->last_event_time + t->win.size)
 			continue;
 
+		trace_psi_event_tp(t);
+
 		/* Generate an event */
 		if (cmpxchg(&t->event, 0, 1) == 0) {
 			if (t->of)
-- 
2.25.1