commit d34c5fa06fade08a689fc171bf756fba2858ae73 upstream. 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 <[email protected]> Acked-by: Johannes Weiner <[email protected]> Acked-by: Rik van Riel <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Jan Kara <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Theodore Ts'o <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Mel Gorman <[email protected]> --- 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 fd2752a..2e7ec3c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -505,16 +505,26 @@ 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_count(buddy) != 0); + + if (page_zone_id(page) != page_zone_id(buddy)) + return 0; + return 1; } if (PageBuddy(buddy) && page_order(buddy) == order) { VM_BUG_ON(page_count(buddy) != 0); + + /* + * 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
