[RFC PATCH] mm: handle simple case in free_pcppages_bulk()

[Namhyung Kim]

Now I'm seeing that there are some cases to free all pages in a
pcp lists. In that case, just frees all pages in the lists instead
of being bothered with round-robin lists traversal.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxx>
---
 mm/page_alloc.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e8b02771ccea..959c54450ddf 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -596,6 +596,28 @@ static void free_pcppages_bulk(struct zone *zone, int count,
 	zone->all_unreclaimable = 0;
 	zone->pages_scanned = 0;
 
+	/* Simple case: Free all */
+	if (to_free == pcp->count) {
+		LIST_HEAD(freelist);
+
+		for (; migratetype < MIGRATE_PCPTYPES; migratetype++)
+			if (!list_empty(&pcp->lists[migratetype]))
+				list_move(&pcp->lists[migratetype], &freelist);
+
+		while (!list_empty(&freelist)) {
+			struct page *page;
+
+			page = list_first_entry(&freelist, struct page, lru);
+			/* must delete as __free_one_page list manipulates */
+			list_del(&page->lru);
+			/* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
+			__free_one_page(page, zone, 0, page_private(page));
+			trace_mm_page_pcpu_drain(page, 0, page_private(page));
+			to_free--;
+		}
+		VM_BUG_ON(to_free);
+	}
+
 	while (to_free) {
 		struct page *page;
 		struct list_head *list;
-- 
1.7.4

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