[RFC PATCH V1 12/13] trace/kmmscand: Add tracing of scanning and migration

[Raghavendra K T <raghavendra.kt@amd.com>]

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

CC: Steven Rostedt <rostedt@goodmis.org>
CC: Masami Hiramatsu <mhiramat@kernel.org>
CC: linux-trace-kernel@vger.kernel.org

Signed-off-by: Raghavendra K T <raghavendra.kt@amd.com>
---
 Changes done based Steves feedback:
 1) Using EVENT class for similar traces
 2) Dropping task_comm
 3) remove unnecessary module name in print

 include/trace/events/kmem.h | 90 +++++++++++++++++++++++++++++++++++++
 mm/kmmscand.c               |  8 ++++
 2 files changed, 98 insertions(+)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index b37eb0a7060f..cef527ef9d79 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/kmmscand.c b/mm/kmmscand.c
index c88b30e0fc7d..38d7825c0d62 100644
--- a/mm/kmmscand.c
+++ b/mm/kmmscand.c
@@ -945,6 +945,7 @@ static void kmmscand_migrate_folio(void)
 				}
 
 				ret = kmmscand_promote_folio(info, dest);
+				trace_kmem_scan_mm_migrate(info->mm, ret, dest);
 			}
 
 			/* TBD: encode migrated count here, currently assume folio_nr_pages */
@@ -1115,6 +1116,9 @@ static unsigned long kmmscand_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))
@@ -1172,6 +1176,8 @@ static unsigned long kmmscand_scan_mm_slot(void)
 		kmmscand_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 */
@@ -1323,6 +1329,7 @@ void __kmmscand_enter(struct mm_struct *mm)
 	spin_unlock(&kmmscand_mm_lock);
 
 	mmgrab(mm);
+	trace_kmem_mm_enter(mm);
 	if (wakeup)
 		wake_up_interruptible(&kmmscand_wait);
 }
@@ -1333,6 +1340,7 @@ void __kmmscand_exit(struct mm_struct *mm)
 	struct mm_slot *slot;
 	int free = 0, serialize = 1;
 
+	trace_kmem_mm_exit(mm);
 	spin_lock(&kmmscand_mm_lock);
 	slot = mm_slot_lookup(kmmscand_slots_hash, mm);
 	mm_slot = mm_slot_entry(slot, struct kmmscand_mm_slot, slot);
-- 
2.34.1