linux-kernel - [RFC PATCH 12/12] mm/cma: add CMA balance VM event counter

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Message-ID: <20250915195153.462039-13-fvdl@google.com>
Date: Mon, 15 Sep 2025 19:51:53 +0000
From: Frank van der Linden <fvdl@...gle.com>
To: akpm@...ux-foundation.org, muchun.song@...ux.dev, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Cc: hannes@...xchg.org, david@...hat.com, roman.gushchin@...ux.dev, 
	Frank van der Linden <fvdl@...gle.com>
Subject: [RFC PATCH 12/12] mm/cma: add CMA balance VM event counter

Add VM counters that record the number of migration
success / failures during CMA rebalancing. This is
similar to other migrate counters.

Signed-off-by: Frank van der Linden <fvdl@...gle.com>
---
 include/linux/vm_event_item.h | 3 +++
 mm/migrate.c                  | 8 ++++++++
 mm/vmstat.c                   | 2 ++
 3 files changed, 13 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 9e15a088ba38..1711ff85a02f 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -87,6 +87,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		CMA_ALLOC_SUCCESS,
 		CMA_ALLOC_FAIL,
 #endif
+		CMA_BALANCE_MIGRATE_SUCCESS,
+		CMA_BALANCE_MIGRATE_FAIL,
+
 		UNEVICTABLE_PGCULLED,	/* culled to noreclaim list */
 		UNEVICTABLE_PGSCANNED,	/* scanned for reclaimability */
 		UNEVICTABLE_PGRESCUED,	/* rescued from noreclaim list */
diff --git a/mm/migrate.c b/mm/migrate.c
index 9e5ef39ce73a..63d771daa3bc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2144,6 +2144,14 @@ int migrate_pages(struct list_head *from, new_folio_t get_new_folio,
 	count_vm_events(THP_MIGRATION_SUCCESS, stats.nr_thp_succeeded);
 	count_vm_events(THP_MIGRATION_FAIL, stats.nr_thp_failed);
 	count_vm_events(THP_MIGRATION_SPLIT, stats.nr_thp_split);
+
+	if (reason == MR_CMA_BALANCE) {
+		count_vm_events(CMA_BALANCE_MIGRATE_SUCCESS,
+				stats.nr_succeeded);
+		count_vm_events(CMA_BALANCE_MIGRATE_FAIL,
+				stats.nr_failed_pages);
+	}
+
 	trace_mm_migrate_pages(stats.nr_succeeded, stats.nr_failed_pages,
 			       stats.nr_thp_succeeded, stats.nr_thp_failed,
 			       stats.nr_thp_split, stats.nr_split, mode,
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 71cd1ceba191..af811328db09 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1392,6 +1392,8 @@ const char * const vmstat_text[] = {
 #ifdef CONFIG_CMA
 	[I(CMA_ALLOC_SUCCESS)]			= "cma_alloc_success",
 	[I(CMA_ALLOC_FAIL)]			= "cma_alloc_fail",
+	[I(CMA_BALANCE_MIGRATE_SUCCESS)]	= "cma_balance_migrate_success",
+	[I(CMA_BALANCE_MIGRATE_FAIL)]		= "cma_balance_migrate_fail",
 #endif
 	[I(UNEVICTABLE_PGCULLED)]		= "unevictable_pgs_culled",
 	[I(UNEVICTABLE_PGSCANNED)]		= "unevictable_pgs_scanned",
-- 
2.51.0.384.g4c02a37b29-goog