1 files changed, 25 insertions, 5 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a6326c7..596180f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -475,6 +475,8 @@ static inline void __free_one_page(struct page *page,
 		int migratetype)
 {
 	unsigned long page_idx;
+	unsigned long combined_idx;
+	struct page *buddy;
 
 	if (unlikely(PageCompound(page)))
 		if (unlikely(destroy_compound_page(page, order)))
@@ -488,9 +490,6 @@ static inline void __free_one_page(struct page *page,
 	VM_BUG_ON(bad_range(zone, page));
 
 	while (order < MAX_ORDER-1) {
-		unsigned long combined_idx;
-		struct page *buddy;
-
 		buddy = __page_find_buddy(page, page_idx, order);
 		if (!page_is_buddy(page, buddy, order))
 			break;
@@ -505,8 +504,29 @@ static inline void __free_one_page(struct page *page,
 		order++;
 	}
 	set_page_order(page, order);
-	list_add(&page->lru,
-		&zone->free_area[order].free_list[migratetype]);
+
+	/*
+	 * If this is not the largest possible page, check if the buddy
+	 * of the next-highest order is free. If it is, it's possible
+	 * that pages are being freed that will coalesce soon. In case,
+	 * that is happening, add the free page to the tail of the list
+	 * so it's less likely to be used soon and more likely to be merged
+	 * as a higher order page
+	 */
+	if ((order < MAX_ORDER-1) && pfn_valid_within(page_to_pfn(buddy))) {
+		struct page *higher_page, *higher_buddy;
+		combined_idx = __find_combined_index(page_idx, order);
+		higher_page = page + combined_idx - page_idx;
+		higher_buddy = __page_find_buddy(higher_page, combined_idx, order + 1);
+		if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
+			list_add_tail(&page->lru,
+				&zone->free_area[order].free_list[migratetype]);
+			goto out;
+		}
+	}
+
+	list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
+out:
 	zone->free_area[order].nr_free++;
 }