[PATCH 29/97] mm/compaction: do not call suitable_migration_target() on every page

From: Mel Gorman
Date: Thu Aug 28 2014 - 15:05:19 EST

From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

commit 01ead5340bcf5f3a1cd2452c75516d0ef4d908d7 upstream.

suitable_migration_target() checks that pageblock is suitable for
migration target. In isolate_freepages_block(), it is called on every
page and this is inefficient. So make it called once per pageblock.

suitable_migration_target() also checks if page is highorder or not, but
it's criteria for highorder is pageblock order. So calling it once
within pageblock range has no problem.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
mm/compaction.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 5e48834..6718a91 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -245,6 +245,7 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
struct page *cursor, *valid_page = NULL;
unsigned long flags;
bool locked = false;
+ bool checked_pageblock = false;

cursor = pfn_to_page(blockpfn);

@@ -276,8 +277,16 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,

/* Recheck this is a suitable migration target under lock */
- if (!strict && !suitable_migration_target(page))
- break;
+ if (!strict && !checked_pageblock) {
+ /*
+ * We need to check suitability of pageblock only once
+ * and this isolate_freepages_block() is called with
+ * pageblock range, so just check once is sufficient.
+ */
+ checked_pageblock = true;
+ if (!suitable_migration_target(page))
+ break;
+ }

/* Recheck this is a buddy page under lock */
if (!PageBuddy(page))

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/