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mm/compaction: disallow high-order page for migration target

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Purpose of compaction is to get a high order page.  Currently, if we
find high-order page while searching migration target page, we break it
to order-0 pages and use them as migration target.  It is contrary to
purpose of compaction, so disallow high-order page to be used for
migration target.

Additionally, clean-up logic in suitable_migration_target() to simplify
the code.  There is no functional changes from this clean-up.

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>
This commit is contained in:
Joonsoo Kim 2014-04-07 15:37:03 -07:00 committed by Linus Torvalds
parent 70ef57e6c2
commit 7d348b9ea6
1 changed files with 3 additions and 12 deletions
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15
mm/compaction.c
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@ -217,21 +217,12 @@ static inline bool compact_trylock_irqsave(spinlock_t *lock,
/* Returns true if the page is within a block suitable for migration to */ /* Returns true if the page is within a block suitable for migration to */
static bool suitable_migration_target(struct page *page) static bool suitable_migration_target(struct page *page)
{ {
int migratetype = get_pageblock_migratetype(page); /* If the page is a large free page, then disallow migration */
/* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
if (migratetype == MIGRATE_RESERVE)
return false;
if (is_migrate_isolate(migratetype))
return false;
/* If the page is a large free page, then allow migration */
if (PageBuddy(page) && page_order(page) >= pageblock_order) if (PageBuddy(page) && page_order(page) >= pageblock_order)
return true; return false;
/* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
if (migrate_async_suitable(migratetype)) if (migrate_async_suitable(get_pageblock_migratetype(page)))
return true; return true;
/* Otherwise skip the block */ /* Otherwise skip the block */