>>>>> Andrew Morton (AM) writes: AM> On Fri, 6 Oct 2006 00:41:03 -0600 AM> Andreas Dilger <adilger@xxxxxxxxxxxxx> wrote: >> The big performance win will come with mballoc and delalloc. CFS has >> been using mballoc for a few years already with Lustre, and IBM + Bull >> did a lot of benchmarking on it. The reason it isn't in the first set of >> patches is partly a manageability issue, and partly because it doesn't >> directly affect the on-disk format (outside of much better allocation) >> so it isn't critical to get into the first round of changes. I believe >> Alex is working on a new set of patches right now. AM> Are you sure that these things will improve allocation much? Reservations AM> made a big improvement there. it depends on underlaying storage and workload. mballoc uses buddy internally. it's much simpler and cheaper to find free 2^N blocks compared to bitmap. this is especially important for arrays like DDN and raid5/6 because they require stripe-aligned/-sized requests for good throughput. also, last mballoc takes logical block into account and can preallocate few chunks at different logical offsets for a file. imagine torrent downloading different pieces from few peers. thanks, Alex - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
