[PATCH 3/3] mm: page_alloc: batch vmstat updates in expand()

[Johannes Weiner]

expand() currently updates vmstat for every subpage. This is
unnecessary, since they're all of the same zone and migratetype.

Count added pages locally, then do a single vmstat update.

Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
 mm/page_alloc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8987e8869f6d..13fe5c612fbe 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1341,6 +1341,7 @@ static inline void expand(struct zone *zone, struct page *page,
 	int low, int high, int migratetype)
 {
 	unsigned long size = 1 << high;
+	unsigned long nr_added = 0;
 
 	while (high > low) {
 		high--;
@@ -1356,9 +1357,11 @@ static inline void expand(struct zone *zone, struct page *page,
 		if (set_page_guard(zone, &page[size], high))
 			continue;
 
-		add_to_free_list(&page[size], zone, high, migratetype, false);
+		__add_to_free_list(&page[size], zone, high, migratetype, false);
 		set_buddy_order(&page[size], high);
+		nr_added += size;
 	}
+	account_freepages(zone, nr_added, migratetype);
 }
 
 static void check_new_page_bad(struct page *page)
-- 
2.44.0