On Tue, May 15, 2012 at 04:05:34PM -0400, Josef Bacik wrote: > On Tue, May 15, 2012 at 01:55:33PM -0600, Andreas Dilger wrote: > > It should be fairly straight forward to have a flag set in the ext4 > > superblock (s_state flag?) that indicates that the filesystem has > > been exported via NFS. There might be other optimizations that can > > be done based on this (e.g. avoid some of the directory cookie > > hijinx that are only needed if NFS has exported the filesystem and > > needs to keep persistent cookies across reboots). > > > > I think that the ext4_mark_inode_dirty() performance problem could > > be at least partially fixed by deferring the copy of in-core inode > > to on-disk inode to use a journal commit callback. This is far more > > work than just setting a flag in the superblock, but it has the > > potential to _improve_ performance rather than make it worse. Could you give any more pointers for an ext4 ignoramus? (Where *is* the journal commit code that would need the callback? And where is the copy currently done?) > Yeah Btrfs doesn't have this sort of problem since we delay inode > updating sinc it is so costly, we simply let it hang around in the > in-core inode until we feel like updating it at some point down the > road. I'll put together a feature flag or something to make it be > enabled for always if somebody turns it on. Thanks for looking at this. A feature flag would be an improvement over a mount option. If the flag makes a noticeable difference to performance, then it makes me nervous toggling it automatically. And what will we do if statx starts returning i_version to userspace? --b. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
