On Tue, Jan 24, 2012 at 01:40:54PM -0500, Christoph Hellwig wrote: > On Tue, Jan 24, 2012 at 01:05:50PM -0500, Jeff Moyer wrote: > > - buffered writes and buffered O_SYNC writes, all 1MB block size show 4k > > I/Os passed down to the I/O scheduler > > - buffered 1MB reads are a little better, typically in the 128k-256k > > range when they hit the I/O scheduler. > > > > ext4: > > - buffered writes: 512K I/Os show up at the elevator > > - buffered O_SYNC writes: data is again 512KB, journal writes are 4K > > - buffered 1MB reads get down to the scheduler in 128KB chunks > > > > xfs: > > - buffered writes: 1MB I/Os show up at the elevator > > - buffered O_SYNC writes: 1MB I/Os > > - buffered 1MB reads: 128KB chunks show up at the I/O scheduler > > > > So, ext4 is doing better than ext3, but still not perfect. xfs is > > kicking ass for writes, but reads are still split up. > > All three filesystems use the generic mpages code for reads, so they > all get the same (bad) I/O patterns. Looks like we need to fix this up > ASAP. Can you easily run btrfs through the same rig? We don't use mpages and I'm curious. -chris -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
