On Tue, May 06, 2014 at 07:22:50PM -0700, David Rientjes wrote: > Synchronous memory compaction can be very expensive: it can iterate an enormous > amount of memory without aborting, constantly rescheduling, waiting on page > locks and lru_lock, etc, if a pageblock cannot be defragmented. > > Unfortunately, it's too expensive for transparent hugepage page faults 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. > > Now that async compaction remembers where it left off without strictly relying > on sync compaction, this makes thp allocations best-effort without causing > egregious latency during fault. We still need to retry async compaction after > reclaim, but this won't stall for seconds. > > Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> -- Mel Gorman SUSE Labs -- 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>