3 files changed, 44 insertions, 2 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b674625762c4..3b13d3914176 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -43,6 +43,7 @@
 #include <linux/mempolicy.h>
 #include <linux/memremap.h>
 #include <linux/stop_machine.h>
+#include <linux/random.h>
 #include <linux/sort.h>
 #include <linux/pfn.h>
 #include <linux/backing-dev.h>
@@ -958,7 +959,8 @@ done_merging:
 	 * so it's less likely to be used soon and more likely to be merged
 	 * as a higher order page
 	 */
-	if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn)) {
+	if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn)
+			&& !is_shuffle_order(order)) {
 		struct page *higher_page, *higher_buddy;
 		combined_pfn = buddy_pfn & pfn;
 		higher_page = page + (combined_pfn - pfn);
@@ -972,7 +974,12 @@ done_merging:
 		}
 	}
 
-	add_to_free_area(page, &zone->free_area[order], migratetype);
+	if (is_shuffle_order(order))
+		add_to_free_area_random(page, &zone->free_area[order],
+				migratetype);
+	else
+		add_to_free_area(page, &zone->free_area[order], migratetype);
+
 }
 
 /*
diff --git a/mm/shuffle.c b/mm/shuffle.c
index bc0419a61fbe..3ce12481b1dc 100644
--- a/mm/shuffle.c
+++ b/mm/shuffle.c
@@ -182,3 +182,26 @@ void __meminit __shuffle_free_memory(pg_data_t *pgdat)
 	for (z = pgdat->node_zones; z < pgdat->node_zones + MAX_NR_ZONES; z++)
 		shuffle_zone(z);
 }
+
+void add_to_free_area_random(struct page *page, struct free_area *area,
+		int migratetype)
+{
+	static u64 rand;
+	static u8 rand_bits;
+
+	/*
+	 * The lack of locking is deliberate. If 2 threads race to
+	 * update the rand state it just adds to the entropy.
+	 */
+	if (rand_bits == 0) {
+		rand_bits = 64;
+		rand = get_random_u64();
+	}
+
+	if (rand & 1)
+		add_to_free_area(page, area, migratetype);
+	else
+		add_to_free_area_tail(page, area, migratetype);
+	rand_bits--;
+	rand >>= 1;
+}
diff --git a/mm/shuffle.h b/mm/shuffle.h
index 644c8ee97b9e..777a257a0d2f 100644
--- a/mm/shuffle.h
+++ b/mm/shuffle.h
@@ -36,6 +36,13 @@ static inline void shuffle_zone(struct zone *z)
 		return;
 	__shuffle_zone(z);
 }
+
+static inline bool is_shuffle_order(int order)
+{
+	if (!static_branch_unlikely(&page_alloc_shuffle_key))
+		return false;
+	return order >= SHUFFLE_ORDER;
+}
 #else
 static inline void shuffle_free_memory(pg_data_t *pgdat)
 {
@@ -48,5 +55,10 @@ static inline void shuffle_zone(struct zone *z)
 static inline void page_alloc_shuffle(enum mm_shuffle_ctl ctl)
 {
 }
+
+static inline bool is_shuffle_order(int order)
+{
+	return false;
+}
 #endif
 #endif /* _MM_SHUFFLE_H */