[PATCH 6/7] mm/page_alloc: store freelist migratetype to the page on buddy properly

[Joonsoo Kim]

To maintain freelist migratetype information on buddy pages, migratetype
should be set again whenever the page order is changed. set_page_order()
is the best place to do, because it is called whenever the page order is
changed, so this patch adds set_buddy_migratetype() to set_page_order().

And this patch makes set/get_buddy_migratetype() only enabled if it is
really needed, because it has some overhead.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2733e0b..046e09f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -258,6 +258,12 @@ struct inode;
 #define set_page_private(page, v)	((page)->private = (v))
 
 /*
+ * This is for tracking the type of the list on buddy.
+ * It imposes some performance overhead to the buddy allocator,
+ * so we make it enabled only if it is needed.
+ */
+#if defined(CONFIG_MEMORY_ISOLATION) || defined(CONFIG_CMA)
+/*
  * It's valid only if the page is on buddy. It represents
  * which freelist the page is linked.
  */
@@ -270,6 +276,10 @@ static inline int get_buddy_migratetype(struct page *page)
 {
 	return page->index;
 }
+#else
+static inline void set_buddy_migratetype(struct page *page, int migratetype) {}
+static inline int get_buddy_migratetype(struct page *page) { return 0; }
+#endif
 
 /*
  * It's valid only if the page is on pcp list. It represents
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c9e6622..2548b42 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -446,9 +446,11 @@ static inline void set_page_guard_flag(struct page *page) { }
 static inline void clear_page_guard_flag(struct page *page) { }
 #endif
 
-static inline void set_page_order(struct page *page, int order)
+static inline void set_page_order(struct page *page, int order,
+						int migratetype)
 {
 	set_page_private(page, order);
+	set_buddy_migratetype(page, migratetype);
 	__SetPageBuddy(page);
 }
 
@@ -588,7 +590,7 @@ static inline void __free_one_page(struct page *page,
 		page_idx = combined_idx;
 		order++;
 	}
-	set_page_order(page, order);
+	set_page_order(page, order, migratetype);
 
 	/*
 	 * If this is not the largest possible page, check if the buddy
@@ -745,7 +747,6 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 	local_irq_save(flags);
 	__count_vm_events(PGFREE, 1 << order);
 	migratetype = get_pageblock_migratetype(page);
-	set_buddy_migratetype(page, migratetype);
 	free_one_page(page_zone(page), page, order, migratetype);
 	local_irq_restore(flags);
 }
@@ -834,7 +835,7 @@ static inline void expand(struct zone *zone, struct page *page,
 #endif
 		list_add(&page[size].lru, &area->free_list[migratetype]);
 		area->nr_free++;
-		set_page_order(&page[size], high);
+		set_page_order(&page[size], high, migratetype);
 	}
 }
 
-- 
1.7.9.5

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