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. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
