The patch titled Subject: mm, compaction: do not recheck suitable_migration_target under lock has been removed from the -mm tree. Its filename was mm-compaction-do-not-recheck-suitable_migration_target-under-lock.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Vlastimil Babka <vbabka@xxxxxxx> Subject: 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@xxxxxxx> Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx> Acked-by: Minchan Kim <minchan@xxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Michal Nazarewicz <mina86@xxxxxxxxxx> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 13 ------------- 1 file changed, 13 deletions(-) diff -puN mm/compaction.c~mm-compaction-do-not-recheck-suitable_migration_target-under-lock mm/compaction.c --- a/mm/compaction.c~mm-compaction-do-not-recheck-suitable_migration_target-under-lock +++ a/mm/compaction.c @@ -276,7 +276,6 @@ static unsigned long isolate_freepages_b 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_b 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; _ Patches currently in -mm which might be from vbabka@xxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html