mm: batch-free pcp list if possible

free_pcppages_bulk() frees pages from pcp lists in a round-robin fashion
by keeping batch_free counter.  But it doesn't need to spin if there is
only one non-empty list.  This can be checked by batch_free ==
MIGRATE_PCPTYPES.

[akpm@linux-foundation.org: fix comment]
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 36a168e..426056a 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -614,6 +614,10 @@ static void free_pcppages_bulk(struct zone *zone, int count,
                        list = &pcp->lists[migratetype];
                } while (list_empty(list));
 
+               /* This is the only non-empty list. Free them all. */
+               if (batch_free == MIGRATE_PCPTYPES)
+                       batch_free = to_free;
+
                do {
                        page = list_entry(list->prev, struct page, lru);
                        /* must delete as __free_one_page list manipulates */