I think this is related to the sync issues. You could try the josef's git
tree:
git://git.kernel.org/pub/scm/linux/kernel/git/josef/btrfs-work.git
Since yesterday I'm using it in our ceph cluster and it seems to do a
better job.
Regards,
Christian
2011/10/9 Martin Mailand <martin@tuxadero.com>:> Hi,
> I have high IO-Wait on the ods (ceph), the osd are running a v3.1-rc9
> kernel.
> I also experience high IO-rates, around 500IO/s reported via iostat.
>
> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz
> avgqu-sz await r_await w_await svctm %util
> sda 0.00 0.00 0.00 6.80 0.00 62.40 18.35
> 0.04 5.29 0.00 5.29 5.29 3.60
> sdb 0.00 249.80 0.40 669.60 1.60 4118.40 12.30
87.47
> 130.56 15.00 130.63 1.01 67.40
>
> In comparison, the same workload, but the osd uses ext4 as a backing fs.
>
> Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz
> avgqu-sz await r_await w_await svctm %util
> sda 0.00 0.00 0.00 10.00 0.00 128.00 25.60
> 0.03 3.40 0.00 3.40 3.40 3.40
> sdb 0.00 27.80 0.00 48.20 0.00 318.40 13.21 0.43
> 8.84 0.00 8.84 1.99 9.60
>
> iodump shows similar results, where sdb is the data disk, sda7 the journal
> and sda5 the root.
>
> btrfs
>
> root@s-brick-003:~# echo 1 > /proc/sys/vm/block_dump
> root@s-brick-003:~# while true; do sleep 1; dmesg -c; done | perl
> /usr/local/bin/iodump
> ^C# Caught SIGINT.
> TASK PID TOTAL READ WRITE DIRTY
> DEVICES
> btrfs-submit-0 8321 28040 0 28040 0 sdb
> ceph-osd 8514 158 0 158 0 sda7
> kswapd0 46 81 0 81 0 sda1
> bash 10709 35 35 0 0 sda1
> flush-8:0 962 12 0 12 0 sda5
> kworker/0:1 8897 6 0 6 0 sdb
> kworker/1:1 10354 3 0 3 0 sdb
> kjournald 266 3 0 3 0 sda5
> ceph-osd 8523 2 2 0 0 sda1
> ceph-osd 8531 1 1 0 0 sda1
> dmesg 10712 1 1 0 0 sda5
>
>
> ext4
>
> root@s-brick-002:~# echo 1 > /proc/sys/vm/block_dump
> root@s-brick-002:~# while true; do sleep 1; dmesg -c; done | perl
> /usr/local/bin/iodump
> ^C# Caught SIGINT.
> TASK PID TOTAL READ WRITE DIRTY
> DEVICES
> ceph-osd 3115 847 0 847 0 sdb
> jbd2/sdb-8 2897 784 0 784 0 sdb
> ceph-osd 3112 728 0 728 0
sda5,
> sdb
> ceph-osd 3110 191 0 191 0 sda7
> perl 3628 13 13 0 0 sda5
> flush-8:16 2901 8 0 8 0 sdb
> kjournald 272 3 0 3 0 sda5
> dmesg 3630 1 1 0 0 sda5
> sleep 3629 1 1 0 0 sda5
>
>
> I think that is the same problem as in
> http://marc.info/?l=ceph-devel&m=131158049117139&w=2
>
> I also did a latencytop as Chris recommended in the above thread.
>
> Best Regards,
> martin
>
>
>
>
>
>
>