2014-05-01 9:45 GMT+09:00 David Rientjes <rientjes@xxxxxxxxxx>: > Synchronous memory compaction can be very expensive: it can iterate an enormous > amount of memory without aborting and it can wait on page locks and writeback to > complete if a pageblock cannot be defragmented. > Unfortunately, it's too expensive for pagefault for transparent hugepages and > it's much better to simply fallback to pages. On 128GB machines, we find that > synchronous memory compaction can take O(seconds) for a single thp fault. Hello, AFAIK, synchronous compaction doesn't wait the page on writeback. sync compaction pass MIGRATE_SYNC_LIGHT for migrate_mode, instead of MIGRATE_SYNC. It results in skipping the page on writeback. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>