On Mon, 2009-11-23 at 13:19 -0500, J. Bruce Fields wrote: > On Mon, Nov 23, 2009 at 01:11:19PM -0500, Trond Myklebust wrote: > > On Mon, 2009-11-23 at 11:44 -0500, J. Bruce Fields wrote: > > > If the side we want to optimize is the modifications, I wonder if we > > > could do all the i_version increments on *read* of i_version?: > > > > > > - writes (and other inode modifications) set an "i_version_dirty" > > > flag. > > > - reads of i_version clear the i_version_dirty flag, increment > > > i_version, and return the result. > > > > > > As long as the reader sees i_version_flag set only after it sees the > > > write that caused it, I think it all works? > > > > That probably won't make much of a difference to performance. Most NFSv4 > > clients will have every WRITE followed by a GETATTR operation in the > > same compound, so your i_version_dirty flag will always immediately get > > cleared. > > I was only thinking about non-NFS performance. I would think that running a high performance database _and_ NFS server on the same machine would tend to be very much of a corner case anyway. In most setups I'm aware of, the database and NFS server tend to be completely separate machines. > > The question is, though, why does the jbd2 machinery need to be engaged > > on _every_ write? > > Is it? See Ted's email. As I read it, his concern was that if they allow people to reduce the a/m/c/time resolution, then the i_version would still force them to dirty the inode on every write... Trond -- 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
