From: David Rientjes <rientjes@xxxxxxxxxx> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== commit 119d6d59dcc0980dcd581fdadb6b2033b512a473 upstream. Page migration will fail for memory that is pinned in memory with, for example, get_user_pages(). In this case, it is unnecessary to take zone->lru_lock or isolating the page and passing it to page migration which will ultimately fail. This is a racy check, the page can still change from under us, but in that case we'll just fail later when attempting to move the page. This avoids very expensive memory compaction when faulting transparent hugepages after pinning a lot of memory with a Mellanox driver. On a 128GB machine and pinning ~120GB of memory, before this patch we see the enormous disparity in the number of page migration failures because of the pinning (from /proc/vmstat): compact_pages_moved 8450 compact_pagemigrate_failed 15614415 0.05% of pages isolated are successfully migrated and explicitly triggering memory compaction takes 102 seconds. After the patch: compact_pages_moved 9197 compact_pagemigrate_failed 7 99.9% of pages isolated are now successfully migrated in this configuration and memory compaction takes less than one second. Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Greg Thelen <gthelen@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- mm/compaction.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/mm/compaction.c b/mm/compaction.c index ae428e665617..488538783440 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -582,6 +582,15 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, continue; } + /* + * Migration will fail if an anonymous page is pinned in memory, + * so avoid taking lru_lock and isolating it unnecessarily in an + * admittedly racy check. + */ + if (!page_mapping(page) && + page_count(page) > page_mapcount(page)) + continue; + /* Check if it is ok to still hold the lock */ locked = compact_checklock_irqsave(&zone->lru_lock, &flags, locked, cc); -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html