mm/compaction: do not call suitable_migration_target() on every page

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@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index 9a03fdb1fd84..3a1828541dc0 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -244,6 +244,7 @@ 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);
 
@@ -275,8 +276,16 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
                         break;
 
                 /* 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))