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authorMel Gorman <mgorman@suse.de>2014-06-05 03:10:10 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-05 03:54:08 +0400
commitd34c5fa06fade08a689fc171bf756fba2858ae73 (patch)
tree68e67f14ce1a98d11bed2a105d6c7047aedfab71 /mm/page_alloc.c
parent664eeddeef6539247691197c1ac124d4aa872ab6 (diff)
downloadlinux-d34c5fa06fade08a689fc171bf756fba2858ae73.tar.xz
mm: page_alloc: only check the zone id check if pages are buddies
A node/zone index is used to check if pages are compatible for merging but this happens unconditionally even if the buddy page is not free. Defer the calculation as long as possible. Ideally we would check the zone boundary but nodes can overlap. Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Rik van Riel <riel@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Jan Kara <jack@suse.cz> Cc: Michal Hocko <mhocko@suse.cz> Cc: Hugh Dickins <hughd@google.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Theodore Ts'o <tytso@mit.edu> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a2955e101715..da526905b4a5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -509,16 +509,26 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
if (!pfn_valid_within(page_to_pfn(buddy)))
return 0;
- if (page_zone_id(page) != page_zone_id(buddy))
- return 0;
-
if (page_is_guard(buddy) && page_order(buddy) == order) {
VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
+
+ if (page_zone_id(page) != page_zone_id(buddy))
+ return 0;
+
return 1;
}
if (PageBuddy(buddy) && page_order(buddy) == order) {
VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
+
+ /*
+ * zone check is done late to avoid uselessly
+ * calculating zone/node ids for pages that could
+ * never merge.
+ */
+ if (page_zone_id(page) != page_zone_id(buddy))
+ return 0;
+
return 1;
}
return 0;