linux-kernel - [RFC PATCH V3] sched: psi: Add psi events trace point

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Message-ID: <20250911032823.19064-1-xuewen.yan@unisoc.com>
Date: Thu, 11 Sep 2025 11:28:23 +0800
From: Xuewen Yan <xuewen.yan@...soc.com>
To: <surenb@...gle.com>, <hannes@...xchg.org>,
        <mathieu.desnoyers@...icios.com>, <mhiramat@...nel.org>,
        <peterz@...radead.org>
CC: <rostedt@...dmis.org>, <mingo@...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 V3] 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>
---
V3:
-export it in the tracefs;
---
v2:
-fix compilation error;
-export the tp;
-add more commit message;
---
 include/trace/events/sched.h | 27 +++++++++++++++++++++++++++
 kernel/sched/psi.c           |  4 ++++
 2 files changed, 31 insertions(+)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 7b2645b50e78..db8b8f25466e 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -826,6 +826,33 @@ TRACE_EVENT(sched_wake_idle_without_ipi,
 	TP_printk("cpu=%d", __entry->cpu)
 );
 
+#ifdef CONFIG_PSI
+TRACE_EVENT(psi_event,
+
+	TP_PROTO(int aggregator, int state, u64 threshold, u64 win_size),
+
+	TP_ARGS(aggregator, state, threshold, win_size),
+
+	TP_STRUCT__entry(
+		__field(int,	aggregator)
+		__field(int,	state)
+		__field(u64,	threshold)
+		__field(u64,	win_size)
+	),
+
+	TP_fast_assign(
+		__entry->aggregator	= aggregator;
+		__entry->state		= state;
+		__entry->threshold	= threshold;
+		__entry->win_size	= win_size;
+	),
+
+	TP_printk("aggregator=%d state=%d threshold=%llu window_size=%llu",
+		__entry->aggregator, __entry->state, __entry->threshold,
+		__entry->win_size)
+);
+#endif /* CONFIG_PSI */
+
 /*
  * Following tracepoints are not exported in tracefs and provide hooking
  * mechanisms only for testing and debugging purposes.
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 59fdb7ebbf22..5b7954b653ed 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);
+
 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(aggregator, t->state, t->threshold, t->win.size);
+
 		/* Generate an event */
 		if (cmpxchg(&t->event, 0, 1) == 0) {
 			if (t->of)
-- 
2.25.1