On Thu, Sep 13, 2007 at 03:23:21AM +1000, Nick Piggin wrote: > On Thursday 13 September 2007 11:49, David Chinner wrote: > > On Wed, Sep 12, 2007 at 01:27:33AM +1000, Nick Piggin wrote: > > > > I just gave 4 things which combined might easily reduce xfs vmap overhead > > > by several orders of magnitude, all without changing much code at all. > > > > Patches would be greatly appreciately. You obviously understand this > > vm code much better than I do, so if it's easy to fix by adding some > > generic vmap cache thingy, please do. > > Well, it may not be easy to _fix_, but it's easy to try a few improvements ;) > > How do I make an image and run a workload that will coerce XFS into > doing a significant number of vmaps?
# mkfs.xfs -n size=16384 <dev> to create a filesystem with a 16k directory block size on a 4k page machine. Then just do operations on directories with lots of files in them (tens of thousands). Every directory operation will require at least one vmap in this situation - e.g. a traversal will result in lots and lots of blocks being read that will require vmap() for every directory block read from disk and an unmap almost immediately afterwards when the reference is dropped.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
