I am continuing to do testing as time allows. Lat night I ran sysbench
fileio tests, and again, the ploop CT yielded better performance then
either then simfs CT or the vzhost. It wasn't as drastic a difference as
the dbench results, but the difference was there. I'll continue in this
vein with freshly created CTs. The machine was just built a few days ago,
it's quiescent, it's doing nothing except hosting a few vanilla CTs.
As for the rules of thumb, I can tell you that the results are 100%
repeatable. But explainable, ah, that's the thing. still working on that.
Regards,
J J
On Sat, May 3, 2014 at 11:31 AM, Kir Kolyshkin <k...@openvz.org> wrote:
> On 05/02/2014 04:38 PM, jjs - mainphrame wrote:
>
> 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.
>
>
> You can use a real file on tmpfs.
>
> Also, in general, there are very many factors that influence test results.
> Starting from the cron jobs and other stuff (say, network activity) that
> runs periodically or sporadically and spoils your results, to the cache
> state (you need to use vm_drop_caches, or yet better, reboot between
> tests), to the physical place on disk where your data is placed (rotating
> hdds tend to be faster at the first sectors compared to the last sectors,
> so ideally you need to do this on a clean freshly formatted filesystem).
> There is much more to it, can be some other factors, too. The rule of thumb
> is results need to be reproducible and explainable.
>
> Kir.
>
>
>
> 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 <k...@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@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@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@vzhost ~]#
>>
>>
>> PLOOP CT
>> ----------------
>> root@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@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@vz101:~#
>>
>>
>> SIMFS CT
>> ----------------
>> root@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@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@vz102:~#
>>
>> Regards,
>>
>> J J
>>
>>
>>
>>
>> On Fri, May 2, 2014 at 2:10 PM, jjs - mainphrame <j...@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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