On Wed, May 20 2009, Christoph Hellwig wrote: > On Wed, May 20, 2009 at 02:16:30PM +0200, Jens Axboe wrote: > > It's a fine rule, I agree ;-) > > > > I'll take another look at this when splitting the sync paths. > > Btw, there has been quite a bit of work on the higher level sync code in > the VFS tree, and I have some TODO list items for the lower level sync > code. The most important one would be splitting data and metadata > writeback. > > Currently __sync_single_inode first calls do_writepages to write back > the data, then write_inode to potentially write the metadata and then > finally filemap_fdatawait to wait for the inode to be completed. > > Now for one thing doing the data wait after the metadata writeout is > wrong for all those filesystems performing some kind of metadata updates > in the I/O completion handler, and e.g. XFS has to work around this > by doing a wait by itself in it's write_inode handler. > > Second inodes are usually clustered together, so if a filesystem can > issue multiple dirty inodes at the same time performance will be much > better. > > So an optimal sync could would first issue data I/O for all inodes it > wants to write back, then wait for the data I/O to finish and finally > write out the inodes in big clusters. > > I'm not quite sure when we'll get to that, just making sure we don't > work against this direction anywhere. > > And yeah, I really need to take a detailed look at the current > incarnation of your patchset :) Please do, I'm particularly interested in the possibility of having multiple inode placements. Would it be feasible to have the inode backing be differentiated by type (eg data or meta-data)? -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
