[dm-devel] Re: dm-ioband: Test results.

[Ryo Tsuruta]

Hi Vivek,

> I quickly looked at the xls sheet. Most of the test cases seem to be
> direct IO. Have you done testing with buffered writes/async writes and
> been able to provide service differentiation between cgroups?
> 
> For example, two "dd" threads running in two cgroups doing writes.

Thanks for taking a look at the sheet. I did a buffered write test
with "fio." Only two "dd" threads can't generate enough I/O load to
make dm-ioband start bandwidth control. The following is a script that
I actually used for the test.

  #!/bin/bash
  sync
  echo 1 > /proc/sys/vm/drop_caches
  arg="--size=64m --rw=write --numjobs=50 --group_reporting"
  echo $$ > /cgroup/1/tasks
  fio $arg --name=ioband1 --directory=/mnt1 --output=ioband1.log &
  echo $$ > /cgroup/2/tasks
  fio $arg --name=ioband2 --directory=/mnt2 --output=ioband2.log &
  echo $$ > /cgroup/tasks
  wait

I created two dm-devices to easily monitor the throughput of each
cgroup by iostat, and gave weights of 200 for cgroup1 and 100 for
cgroup2 that means cgroup1 can use twice bandwidth of cgroup2. The
following is a part of the output of iostat. dm-0 and dm-1 corresponds
to ioband1 and ioband2. You can see the bandwidth is according to the
weights.

  avg-cpu:  %user   %nice %system %iowait  %steal   %idle
             0.99    0.00    6.44   92.57    0.00    0.00
  
  Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
  dm-0           3549.00         0.00     28392.00          0      28392
  dm-1           1797.00         0.00     14376.00          0      14376
  
  avg-cpu:  %user   %nice %system %iowait  %steal   %idle
             1.01    0.00    4.02   94.97    0.00    0.00
  
  Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
  dm-0           3919.00         0.00     31352.00          0      31352
  dm-1           1925.00         0.00     15400.00          0      15400
  
  avg-cpu:  %user   %nice %system %iowait  %steal   %idle
             0.00    0.00    5.97   94.03    0.00    0.00
  
  Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
  dm-0           3534.00         0.00     28272.00          0      28272
  dm-1           1773.00         0.00     14184.00          0      14184
  
  avg-cpu:  %user   %nice %system %iowait  %steal   %idle
             0.50    0.00    6.00   93.50    0.00    0.00
  
  Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
  dm-0           4053.00         0.00     32424.00          0      32424
  dm-1           2039.00         8.00     16304.00          8      16304

Thanks,
Ryo Tsuruta