1 files changed, 14 insertions, 4 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7c44b49cec40..8d52ab18fe0d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1123,10 +1123,19 @@ static void change_pageblock_range(struct page *pageblock_page,
 }
 
 /*
- * If breaking a large block of pages, move all free pages to the preferred
- * allocation list. If falling back for a reclaimable kernel allocation, be
- * more aggressive about taking ownership of free pages. If we claim more than
- * half of the pageblock, change pageblock's migratetype as well.
+ * When we are falling back to another migratetype during allocation, try to
+ * steal extra free pages from the same pageblocks to satisfy further
+ * allocations, instead of polluting multiple pageblocks.
+ *
+ * If we are stealing a relatively large buddy page, it is likely there will
+ * be more free pages in the pageblock, so try to steal them all. For
+ * reclaimable and unmovable allocations, we steal regardless of page size,
+ * as fragmentation caused by those allocations polluting movable pageblocks
+ * is worse than movable allocations stealing from unmovable and reclaimable
+ * pageblocks.
+ *
+ * If we claim more than half of the pageblock, change pageblock's migratetype
+ * as well.
  */
 static void try_to_steal_freepages(struct zone *zone, struct page *page,
                                   int start_type, int fallback_type)
@@ -1141,6 +1150,7 @@ static void try_to_steal_freepages(struct zone *zone, struct page *page,
 
         if (current_order >= pageblock_order / 2 ||
             start_type == MIGRATE_RECLAIMABLE ||
+            start_type == MIGRATE_UNMOVABLE ||
             page_group_by_mobility_disabled) {
                 int pages;