]> git.karo-electronics.de Git - karo-tx-linux.git/commitdiff
mm: __rmqueue_fallback() should respect pageblock type
authorKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Tue, 5 Nov 2013 05:55:55 +0000 (16:55 +1100)
committerStephen Rothwell <sfr@canb.auug.org.au>
Tue, 5 Nov 2013 05:55:55 +0000 (16:55 +1100)
When __rmqueue_fallback() doesn't find a free block with the required size
it splits a larger page and puts the rest of the page onto the free list.

But it has one serious mistake.  When putting back, __rmqueue_fallback()
always use start_migratetype if type is not CMA.  However,
__rmqueue_fallback() is only called when all of the start_migratetype
queue is empty.  That said, __rmqueue_fallback always puts back memory to
the wrong queue except try_to_steal_freepages() changed pageblock type
(i.e.  requested size is smaller than half of page block).  The end result
is that the antifragmentation framework increases fragmenation instead of
decreasing it.

Mel's original anti fragmentation does the right thing.  But commit
47118af076 ("mm: mmzone: MIGRATE_CMA migration type added") broke it.

This patch restores sane and old behavior.  And also it remvoe an
incorrect comment which introduced at commit fef903efcf (mm/page_alloc.c:
restructure free-page stealing code and fix a bug).

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
mm/page_alloc.c

index 4fb74a8294b001316982a148d4f90f335c3fd2dc..3dc034f842abc6c3d528754a7a0ff8770c6daee1 100644 (file)
@@ -1027,6 +1027,10 @@ static int try_to_steal_freepages(struct zone *zone, struct page *page,
 {
        int current_order = page_order(page);
 
+       /*
+        * When borrowing from MIGRATE_CMA, we need to release the excess
+        * buddy pages to CMA itself.
+        */
        if (is_migrate_cma(fallback_type))
                return fallback_type;
 
@@ -1091,17 +1095,8 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
                        list_del(&page->lru);
                        rmv_page_order(page);
 
-                       /*
-                        * Borrow the excess buddy pages as well, irrespective
-                        * of whether we stole freepages, or took ownership of
-                        * the pageblock or not.
-                        *
-                        * Exception: When borrowing from MIGRATE_CMA, release
-                        * the excess buddy pages to CMA itself.
-                        */
                        expand(zone, page, order, current_order, area,
-                              is_migrate_cma(migratetype)
-                            ? migratetype : start_migratetype);
+                              new_type);
 
                        trace_mm_page_alloc_extfrag(page, order, current_order,
                                start_migratetype, migratetype, new_type);