On Wed, Feb 03, 2010 at 05:44:24PM -0600, Ben Myers wrote: > The following series is adds a 'wsync' export option to nfsd. It is intended > to be used on XFS with the wsync mount option. When you already have a > synchronous log there is no need to sync metadata separately. You don't need the xfs wsync option, as the existing write_inode calls or your new fsync calls are doing the same as the wsync mount option, just from a higher layer. The wsync option causes the log to be synchronously forced up to the log sequence number of the commit for the metadata operation, that is make all the operations affected by it synchronous. That's exactly what we'll do using fsync (actually right now we force the whole log, but I have a patch to optimize it to only force nuntil the last commit lsn), and approqimately the same as we do using write_inode, just a lot less efficiently. > This is barely tested, YMMV, I could have this all wrong, etc, etc. Here are > some very unscientific measurements taken over gigabit ethernet. > > # time tar -xvf /mnt2/quilt-0.47.tar > /dev/null > > No XFS wsync, no NFS wsync: > 0m13.177s 0m13.301s 0m13.528s > > XFS wsync set, no NFS wsync: > 0m13.019s 0m13.232s 0m13.094s > > XFS wsync set, NFS wsync set: > 0m8.361s 0m8.400s 0m8.301s > > Curious to hear if this is a reasonable thing to do. Suggestions welcome. I think it's reasonable. What might be even better it to have an export operation call out into the filesystem so that we can force wsync and not let nfsd deal with it at all. There is a fair chance that the filesystem can do the sync more efficiently. And btw, not directly related to your patch, but getting rid of this write_inode call defintively makes the usage of ->write_inode more regular. From generic code we mostly use it for full inode writeback in writeback_single_inode, and one other special case in generic_detach_inode if a filesystem is unmounting. Only having writeback_single_inode and fs code use it will make this call much more predictable for the filesystem. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
