[PATCH 3/3] mm: optimize free_area_empty() check using per-migratetype counts

[Hongru Zhang]

From: Hongru Zhang <zhanghongru@xxxxxxxxxx>

Use per-migratetype counts instead of list_empty() helps reduce a
few cpu instructions.

Signed-off-by: Hongru Zhang <zhanghongru@xxxxxxxxxx>
---
 mm/internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/internal.h b/mm/internal.h
index 1561fc2ff5b8..7759f8fdf445 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -954,7 +954,7 @@ int find_suitable_fallback(struct free_area *area, unsigned int order,
 
 static inline bool free_area_empty(struct free_area *area, int migratetype)
 {
-	return list_empty(&area->free_list[migratetype]);
+	return !READ_ONCE(area->mt_nr_free[migratetype]);
 }
 
 /* mm/util.c */
-- 
2.43.0