Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Thu, 2015-05-28 at 01:36 +0100, Alasdair G Kergon wrote: > On Wed, May 27, 2015 at 04:42:44PM -0700, Ming Lin wrote: > > Here are fio results of XFS on a DM stripped target with 2 SSDs + 1 HDD. > > Does it make sense? > > To stripe across devices with different characteristics? > > Some suggestions. > > Prepare 3 kernels. > O - Old kernel. > M - Old kernel with merge_bvec_fn disabled. > N - New kernel. > > You're trying to search for counter-examples to the hypothesis that > "Kernel N always outperforms Kernel O". Then if you find any, trying > to show either that the performance impediment is small enough that > it doesn't matter or that the cases are sufficiently rare or obscure > that they may be ignored because of the greater benefits of N in much more > common cases. > > (1) You're looking to set up configurations where kernel O performs noticeably > better than M. Then you're comparing the performance of O and N in those > situations. > > (2) You're looking at other sensible configurations where O and M have > similar performance, and comparing that with the performance of N. I didn't find case (1). But the important thing for this series is to simplify block layer based on immutable biovecs. I don't expect performance improvement. Here is the changes statistics. "68 files changed, 336 insertions(+), 1331 deletions(-)" I run below 3 test cases to make sure it didn't bring any regressions. Test environment: 2 NVMe drives on 2 sockets server. Each case run for 30 minutes. 2) btrfs radi0 mkfs.btrfs -f -d raid0 /dev/nvme0n1 /dev/nvme1n1 mount /dev/nvme0n1 /mnt Then run 8K read. [global] ioengine=libaio iodepth=64 direct=1 runtime=1800 time_based group_reporting numjobs=4 rw=read [job1] bs=8K directory=/mnt size=1G 2) ext4 on MD raid5 mdadm --create /dev/md0 --level=5 --raid-devices=2 /dev/nvme0n1 /dev/nvme1n1 mkfs.ext4 /dev/md0 mount /dev/md0 /mnt fio script same as btrfs test 3) xfs on DM stripped target pvcreate /dev/nvme0n1 /dev/nvme1n1 vgcreate striped_vol_group /dev/nvme0n1 /dev/nvme1n1 lvcreate -i2 -I4 -L250G -nstriped_logical_volume striped_vol_group mkfs.xfs -f /dev/striped_vol_group/striped_logical_volume mount /dev/striped_vol_group/striped_logical_volume /mnt fio script same as btrfs test ------ Results: 4.1-rc4 4.1-rc4-patched btrfs 1818.6MB/s 1874.1MB/s ext4 717307KB/s 714030KB/s xfs 1396.6MB/s 1398.6MB/s