[RFC PATCH V0 09/10] trace/kmmscand: Add tracing of scanning and migration

[Raghavendra K T]

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

CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
CC: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
CC: linux-trace-kernel@xxxxxxxxxxxxxxx

Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxx>
---
 include/trace/events/kmem.h | 99 +++++++++++++++++++++++++++++++++++++
 mm/kmmscand.c               | 12 ++++-
 2 files changed, 110 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index b37eb0a7060f..80978d85300d 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -9,6 +9,105 @@
 #include <linux/tracepoint.h>
 #include <trace/events/mmflags.h>
 
+TRACE_EVENT(kmem_mm_enter,
+
+	TP_PROTO(struct task_struct *t,
+		 struct mm_struct *mm),
+
+	TP_ARGS(t, mm),
+
+	TP_STRUCT__entry(
+		__array(	char, comm, TASK_COMM_LEN	)
+		__field(	struct mm_struct *, mm		)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->comm, t->comm, TASK_COMM_LEN);
+		__entry->mm = mm;
+	),
+
+	TP_printk("kmmscand: mm_enter comm =%s mm=%p", __entry->comm, __entry->mm)
+);
+
+TRACE_EVENT(kmem_scan_mm_start,
+
+	TP_PROTO(struct task_struct *t,
+		 struct mm_struct *mm),
+
+	TP_ARGS(t, mm),
+
+	TP_STRUCT__entry(
+		__array(	char, comm, TASK_COMM_LEN	)
+		__field(	struct mm_struct *, mm		)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->comm, t->comm, TASK_COMM_LEN);
+		__entry->mm = mm;
+	),
+
+	TP_printk("kmmscand: scan_mm_start comm =%s mm=%p", __entry->comm, __entry->mm)
+);
+
+TRACE_EVENT(kmem_scan_mm_end,
+
+	TP_PROTO(struct task_struct *t,
+		 struct mm_struct *mm,
+		 unsigned long start,
+		 unsigned long total,
+		 unsigned long scan_size,
+		 unsigned long scan_period),
+
+	TP_ARGS(t, mm, start, total, scan_period, scan_size),
+
+	TP_STRUCT__entry(
+		__array(	char, comm, TASK_COMM_LEN	)
+		__field(	struct mm_struct *, mm		)
+		__field(	unsigned long,   start		)
+		__field(	unsigned long,   total		)
+		__field(	unsigned long,   scan_period	)
+		__field(	unsigned long,   scan_size	)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->comm, t->comm, TASK_COMM_LEN);
+		__entry->mm = mm;
+		__entry->start = start;
+		__entry->total = total;
+		__entry->scan_period = scan_period;
+		__entry->scan_size = scan_size;
+	),
+
+	TP_printk("kmmscand: scan_mm_end comm =%s mm=%p, start = %ld, total = %ld, scan_period = %ld, scan_size = %ld",
+			__entry->comm, __entry->mm, __entry->start,
+			__entry->total, __entry->scan_period, __entry->scan_size)
+);
+
+TRACE_EVENT(kmem_scan_mm_migrate,
+
+	TP_PROTO(struct task_struct *t,
+		 struct mm_struct *mm,
+		 int rc),
+
+	TP_ARGS(t, mm, rc),
+
+	TP_STRUCT__entry(
+		__array(	char, comm, TASK_COMM_LEN	)
+		__field(	struct mm_struct *, mm		)
+		__field(	int,   rc			)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->comm, t->comm, TASK_COMM_LEN);
+		__entry->mm = mm;
+		__entry->rc = rc;
+	),
+
+	TP_printk("kmmscand: scan_mm_migrate comm =%s mm=%p rc=%d", __entry->comm,
+			__entry->mm, __entry->rc)
+);
+
+
 TRACE_EVENT(kmem_cache_alloc,
 
 	TP_PROTO(unsigned long call_site,
diff --git a/mm/kmmscand.c b/mm/kmmscand.c
index 682c0523c0b4..70f588a210dd 100644
--- a/mm/kmmscand.c
+++ b/mm/kmmscand.c
@@ -668,8 +668,10 @@ static void kmmscand_migrate_folio(void)
 			WRITE_ONCE(kmmscand_cur_migrate_mm, info->mm);
 			spin_unlock(&kmmscand_migrate_lock);
 
-			if (info->mm)
+			if (info->mm) {
 				ret = kmmscand_promote_folio(info);
+				trace_kmem_scan_mm_migrate(info->mm->owner, info->mm, ret);
+			}
 
 			/* TBD: encode migrated count here, currently assume folio_nr_pages */
 			if (!ret)
@@ -828,6 +830,9 @@ static unsigned long kmmscand_scan_mm_slot(void)
 		goto outerloop;
 	}
 
+	if (mm->owner)
+		trace_kmem_scan_mm_start(mm->owner, mm);
+
 	now = jiffies;
 	/*
 	 * Dont scan if :
@@ -868,6 +873,10 @@ static unsigned long kmmscand_scan_mm_slot(void)
 
 	update_mmslot_info = true;
 
+	if (mm->owner)
+		trace_kmem_scan_mm_end(mm->owner, mm, address, total,
+					mm_slot_scan_period, mm_slot_scan_size);
+
 	count_kmmscand_mm_scans();
 
 outerloop:
@@ -1020,6 +1029,7 @@ void __kmmscand_enter(struct mm_struct *mm)
 	spin_unlock(&kmmscand_mm_lock);
 
 	mmgrab(mm);
+	trace_kmem_mm_enter(mm->owner, mm);
 	if (wakeup)
 		wake_up_interruptible(&kmmscand_wait);
 }
-- 
2.39.3