Robert Milkowski writes: > Hello Neil, > > Thursday, August 10, 2006, 7:02:58 PM, you wrote: > > NP> Robert Milkowski wrote: > >> Hello Matthew, > >> > >> Thursday, August 10, 2006, 6:55:41 PM, you wrote: > >> > >> MA> On Thu, Aug 10, 2006 at 06:50:45PM +0200, Robert Milkowski wrote: > >> > >>>>btw: wouldn't it be possible to write block only once (for synchronous > >>>>IO) and than just point to that block instead of copying it again? > >> > >> > >> MA> We actually do exactly that for larger (>32k) blocks. > >> > >> Why such limit (32k)? > > NP> By experimentation that was the cutoff where it was found to be > NP> more efficient. It was recently reduced from 64K with a more > NP> efficient dmu-sync() implementaion. > NP> Feel free to experiment with the dynamically changable tunable: > > NP> ssize_t zfs_immediate_write_sz = 32768; > > > I've just checked using dtrace on one of production nfs servers that > 90% of the time arg5 in zfs_log_write() is exactly 32768 and the rest > is always smaller.
Those should not be O_DSYNC though. Are they ? The I/O should be deferred to a subsequent COMMIT but then I'm not sure how it's handled then. -r _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
