[Users] Curious about ploop performance results.

[Kir Kolyshkin]

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 
> <mailto: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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