linux-kernel - [RFC PATCH V2 12/13] trace/kscand: Add tracing of scanning and migration

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Message-ID: <20250624055617.1291159-13-raghavendra.kt@amd.com>
Date: Tue, 24 Jun 2025 05:56:16 +0000
From: Raghavendra K T <raghavendra.kt@....com>
To: <raghavendra.kt@....com>
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Subject: [RFC PATCH V2 12/13] trace/kscand: Add tracing of scanning and migration

Add tracing support to track
 - start and end of scanning.
 - migration.

CC: Steven Rostedt <rostedt@...dmis.org>
CC: Masami Hiramatsu <mhiramat@...nel.org>
CC: linux-trace-kernel@...r.kernel.org

Signed-off-by: Raghavendra K T <raghavendra.kt@....com>
---
 include/trace/events/kmem.h | 90 +++++++++++++++++++++++++++++++++++++
 mm/kscand.c                 |  8 ++++
 2 files changed, 98 insertions(+)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index f74925a6cf69..682c4015414f 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -9,6 +9,96 @@
 #include <linux/tracepoint.h>
 #include <trace/events/mmflags.h>
 
+DECLARE_EVENT_CLASS(kmem_mm_class,
+
+	TP_PROTO(struct mm_struct *mm),
+
+	TP_ARGS(mm),
+
+	TP_STRUCT__entry(
+		__field(	struct mm_struct *, mm		)
+	),
+
+	TP_fast_assign(
+		__entry->mm = mm;
+	),
+
+	TP_printk("mm = %p", __entry->mm)
+);
+
+DEFINE_EVENT(kmem_mm_class, kmem_mm_enter,
+	TP_PROTO(struct mm_struct *mm),
+	TP_ARGS(mm)
+);
+
+DEFINE_EVENT(kmem_mm_class, kmem_mm_exit,
+	TP_PROTO(struct mm_struct *mm),
+	TP_ARGS(mm)
+);
+
+DEFINE_EVENT(kmem_mm_class, kmem_scan_mm_start,
+	TP_PROTO(struct mm_struct *mm),
+	TP_ARGS(mm)
+);
+
+TRACE_EVENT(kmem_scan_mm_end,
+
+	TP_PROTO( struct mm_struct *mm,
+		 unsigned long start,
+		 unsigned long total,
+		 unsigned long scan_period,
+		 unsigned long scan_size,
+		 int target_node),
+
+	TP_ARGS(mm, start, total, scan_period, scan_size, target_node),
+
+	TP_STRUCT__entry(
+		__field(	struct mm_struct *, mm		)
+		__field(	unsigned long,   start		)
+		__field(	unsigned long,   total		)
+		__field(	unsigned long,   scan_period	)
+		__field(	unsigned long,   scan_size	)
+		__field(	int,		 target_node	)
+	),
+
+	TP_fast_assign(
+		__entry->mm = mm;
+		__entry->start = start;
+		__entry->total = total;
+		__entry->scan_period  = scan_period;
+		__entry->scan_size    = scan_size;
+		__entry->target_node  = target_node;
+	),
+
+	TP_printk("mm=%p, start = %ld, total = %ld, scan_period = %ld, scan_size = %ld node = %d",
+		__entry->mm, __entry->start, __entry->total, __entry->scan_period,
+		__entry->scan_size, __entry->target_node)
+);
+
+TRACE_EVENT(kmem_scan_mm_migrate,
+
+	TP_PROTO(struct mm_struct *mm,
+		 int rc,
+		 int target_node),
+
+	TP_ARGS(mm, rc, target_node),
+
+	TP_STRUCT__entry(
+		__field(	struct mm_struct *, mm		)
+		__field(	int,   rc			)
+		__field(	int,   target_node		)
+	),
+
+	TP_fast_assign(
+		__entry->mm = mm;
+		__entry->rc = rc;
+		__entry->target_node = target_node;
+	),
+
+	TP_printk("mm = %p rc = %d node = %d",
+		__entry->mm, __entry->rc, __entry->target_node)
+);
+
 TRACE_EVENT(kmem_cache_alloc,
 
 	TP_PROTO(unsigned long call_site,
diff --git a/mm/kscand.c b/mm/kscand.c
index db7b2f940f36..029d6d2bedc3 100644
--- a/mm/kscand.c
+++ b/mm/kscand.c
@@ -1035,6 +1035,7 @@ static void kmigrated_migrate_mm(struct kmigrated_mm_slot *mm_slot)
 			}
 
 			ret = kmigrated_promote_folio(info, mm, dest);
+			trace_kmem_scan_mm_migrate(mm, ret, dest);
 
 			/* TBD: encode migrated count here, currently assume folio_nr_pages */
 			if (!ret)
@@ -1230,6 +1231,9 @@ static unsigned long kscand_scan_mm_slot(void)
 	mm_target_node = READ_ONCE(mm->target_node);
 	if (mm_target_node != mm_slot_target_node)
 		WRITE_ONCE(mm->target_node, mm_slot_target_node);
+
+	trace_kmem_scan_mm_start(mm);
+
 	now = jiffies;
 
 	if (mm_slot_next_scan && time_before(now, mm_slot_next_scan))
@@ -1300,6 +1304,8 @@ static unsigned long kscand_scan_mm_slot(void)
 		kscand_update_mmslot_info(mm_slot, total, target_node);
 	}
 
+	trace_kmem_scan_mm_end(mm, address, total, mm_slot_scan_period,
+			mm_slot_scan_size, target_node);
 
 outerloop:
 	/* exit_mmap will destroy ptes after this */
@@ -1453,6 +1459,7 @@ void __kscand_enter(struct mm_struct *mm)
 	spin_unlock(&kscand_mm_lock);
 
 	mmgrab(mm);
+	trace_kmem_mm_enter(mm);
 	if (wakeup)
 		wake_up_interruptible(&kscand_wait);
 }
@@ -1463,6 +1470,7 @@ void __kscand_exit(struct mm_struct *mm)
 	struct mm_slot *slot;
 	int free = 0, serialize = 1;
 
+	trace_kmem_mm_exit(mm);
 	spin_lock(&kscand_mm_lock);
 	slot = mm_slot_lookup(kscand_slots_hash, mm);
 	mm_slot = mm_slot_entry(slot, struct kscand_mm_slot, slot);
-- 
2.34.1