On Tue, Jun 08, 2010 at 05:08:11AM -0400, Christoph Hellwig wrote: > On Tue, Jun 08, 2010 at 10:02:19AM +0100, Mel Gorman wrote: > > seeky patterns. The second is that direct reclaim calling the filesystem > > splices two potentially deep call paths together and potentially overflows > > the stack on complex storage or filesystems. This series is an early draft > > at tackling both of these problems and is in three stages. > > Btw, one more thing came up when I discussed the issue again with Dave > recently: > > - we also need to care about ->releasepage. At least for XFS it > can end up in the same deep allocator chain as ->writepage because > it does all the extent state conversions, even if it doesn't > start I/O. Dang. > I haven't managed yet to decode the ext4/btrfs codepaths > for ->releasepage yet to figure out how they release a page that > covers a delayed allocated or unwritten range. > If ext4/btrfs are also very deep call-chains and this series is going more or less the right direction, then avoiding calling ->releasepage from direct reclaim is one, somewhat unfortunate, option. The second is to avoid it on a per-filesystem basis for direct reclaim using PF_MEMALLOC to detect reclaimers and PF_KSWAPD to tell the difference between direct reclaimers and kswapd. Either way, these pages could be treated similar to dirty pages on the dirty_pages list. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>