diff options
| author | Vlastimil Babka <vbabka@suse.cz> | 2014-10-09 15:27:07 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-10-09 22:25:54 -0400 |
| commit | f8224aa5a0a4627926019bba7511926393fbee3b (patch) | |
| tree | ca92929dcf6b8d84382a9e2ccbe3ed2eb7800b25 /mm/compaction.c | |
| parent | 98dd3b48a7b8e8277f14c2b7d879477efc1ed0d0 (diff) | |
mm, compaction: do not recheck suitable_migration_target under lock
isolate_freepages_block() rechecks if the pageblock is suitable to be a
target for migration after it has taken the zone->lock. However, the
check has been optimized to occur only once per pageblock, and
compact_checklock_irqsave() might be dropping and reacquiring lock, which
means somebody else might have changed the pageblock's migratetype
meanwhile.
Furthermore, nothing prevents the migratetype to change right after
isolate_freepages_block() has finished isolating. Given how imperfect
this is, it's simpler to just rely on the check done in
isolate_freepages() without lock, and not pretend that the recheck under
lock guarantees anything. It is just a heuristic after all.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 13 |
1 files changed, 0 insertions, 13 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 1c7195d42e83..7bf150d4e1c8 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -276,7 +276,6 @@ 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); @@ -307,18 +306,6 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, if (!locked) break; - /* Recheck this is a suitable migration target under lock */ - 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)) goto isolate_fail; |