Messages in this thread Patch in this message | | | From | Mel Gorman <> | Subject | [PATCH 05/17] mm: page_alloc: Only check the zone id check if pages are buddies | Date | Thu, 1 May 2014 09:44:36 +0100 |
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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> --- mm/page_alloc.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3b6ae9d..8971953 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -508,16 +508,26 @@ 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; -- 1.8.4.5
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