[Users] Curious about ploop performance results.

jjs - mainphrame jjs at mainphrame.com
Fri May 2 16:38:25 PDT 2014


Thanks Kir, the /dev/zero makes sense I suppose. I tried with /dev/random
but that blocks pretty quickly - /dev/urandom is better, but still seems to
be a bottleneck.

As for the dbench results, I'd love to hear what results others obtain from
the same test, and/or any other testing approaches that would give a more
"acceptable" answer.

Regards,

J J



On Fri, May 2, 2014 at 4:01 PM, Kir Kolyshkin <kir at openvz.org> wrote:

>  On 05/02/2014 03:00 PM, jjs - mainphrame wrote:
>
> Just for kicks, here are the data from the tests. (these were run on a
> rather modest old machine)
>
>
>
>  Here are the raw dbench data:
>
>
>  #clients        vzhost                  simfs CT        ploop CT
> ---------------------------------------------------------------------
> 1               11.1297MB/sec       9.96657MB/sec       19.7214MB/sec
> 2               12.2936MB/sec       14.3138MB/sec       23.5628MB/sec
> 4               17.8909MB/sec       16.0859MB/sec       45.1936MB/sec
> 8               25.8332MB/sec       22.9195MB/sec       84.2607MB/sec
> 16              32.1436MB/sec       28.921MB/sec        155.207MB/sec
> 32              35.5809MB/sec       32.1429MB/sec       206.571MB/sec
> 64              34.3609MB/sec       29.9307MB/sec       221.119MB/sec
>
>
> Well, I can't explain this, but there's probably something wrong with the
> test.
>
>
>
>  Here is the script used to invoke dbench:
>
>  HOST=`uname -n`
> WD=/tmp
>  FILE=/usr/share/dbench/client.txt
>
>  for i in 1 2 4 8 16 32 64
>  do
>     dbench -D $WD -c $FILE $i &>dbench-${HOST}-${i}
> done
>
>  Here are the dd commands and outputs:
>
>  OPENVZ HOST
> ----------------
> [root at vzhost ~]# dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 11.813 s, 45.4 MB/s
> [root at vzhost ~]# df -T
> Filesystem     Type  1K-blocks    Used Available Use% Mounted on
> /dev/sda2      ext4   20642428 2390620  17203232  13% /
> tmpfs          tmpfs    952008       0    952008   0% /dev/shm
> /dev/sda1      ext2     482922   68436    389552  15% /boot
> /dev/sda4      ext4   51633780 3631524  45379332   8% /local
> [root at vzhost ~]#
>
>
>  PLOOP CT
> ----------------
> root at vz101:~# dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 2.50071 s, 215 MB/s
>
>
> This one I can explain :)
>
> This is caused by ploop optimization that was enabled in the kernel
> recently.
> If data block is all zeroes, it is not written to the disk (same thing as
> sparse files,
> just for ploop).
>
> So you need to test it with some real data (anything but not all zeroes).
> I am not sure how fast is /dev/urandom but this is one of the options.
>
>
>  root at vz101:~# df -T
> Filesystem        Type     1K-blocks    Used Available Use% Mounted on
> /dev/ploop11054p1 ext4       4539600 1529316   2804928  36% /
> none              devtmpfs    262144       4    262140   1% /dev
> none              tmpfs        52432      52     52380   1% /run
> none              tmpfs         5120       0      5120   0% /run/lock
> none              tmpfs       262144       0    262144   0% /run/shm
> root at vz101:~#
>
>
>  SIMFS CT
> ----------------
> root at vz102:~# dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 12.6913 s, 42.3 MB/s
> root at vz102:~# df -T
> Filesystem     Type     1K-blocks    Used Available Use% Mounted on
> /dev/simfs     simfs      4194304 1365500   2828804  33% /
> none           devtmpfs    262144       4    262140   1% /dev
> none           tmpfs        52432      52     52380   1% /run
> none           tmpfs         5120       0      5120   0% /run/lock
> none           tmpfs       262144       0    262144   0% /run/shm
> root at vz102:~#
>
>  Regards,
>
>  J J
>
>>
>
> On Fri, May 2, 2014 at 2:10 PM, jjs - mainphrame <jjs at mainphrame.com>wrote:
>
>> You know the saying, "when something seems too good to be true"...
>>
>>  I just installed centos 6.5 and openvz on an older machine, and when I
>> built an ubuntu 12.04 CT I noticed that ploop is now the default layout.
>> Cool. So I built another ubuntu12.04 CT, identical in every way except that
>> I specified smifs, so I could do a quick performance comparison.
>>
>>  First I did a quick timed dd run, then I ran dbench with varying
>> numbers of clients.
>>
>>  The simfs CT showed performance roughly similar to the host, which was
>> not too surprising.
>> What did surprise me was that the ploop CT showed performance which was
>> significantly better than the host, in both the dd test and the dbench
>> tests.
>>
>>  I know someone will tell me "dbench is a terrible benchmark" but it's
>> also a standard. Of course, if anyone knows a "better" benchmark, I'd love
>> to try it.
>>
>>  Regards,
>>
>>  J J
>>
>
>
>
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