Open Stack

2014-11-10 13:45 GMT+01:00 Akilesh K <akilesh1597 at gmail.com>:

> Hi Alberto,
> May I know the flavor and image you were using to do this test. TSO seems
> to be a method that moves the process of tcp segmentation off to the nic
> card.
>
>
Hi Akilesh,

I was using m1.tiny flavor with 512MiB of RAM and 1 vCPU for all the
previous tests.

Testing now with m1.smaill (2048 MiB of RAM and 1 vCPU) there is a slight
increase in the bandwidth between the instance and its router: ~
300Kbits/sec. The increase is more evident using m1.medium (4096 MiB of RAM
and 2 vCPUs) where a bandwidth ~ 700 Kbits/sec is achieved.

In both cases bandwidth of 700-800 Mbits/sec are measured turning off TSO:

ubuntu at test4g:~$ iperf -c 10.0.0.1
------------------------------------------------------------
Client connecting to 10.0.0.1, TCP port 5001
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[  3] local 10.0.0.17 port 50855 connected with 10.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-11.9 sec  1.00 MBytes   704 Kbits/sec

ubuntu at test4g:~$ sudo ethtool -K eth0 tso off

ubuntu at test4g:~$ iperf -c 10.0.0.1
------------------------------------------------------------
Client connecting to 10.0.0.1, TCP port 5001
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[  3] local 10.0.0.17 port 50856 connected with 10.0.0.1 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   938 MBytes   786 Mbits/sec



> I believe in OpenStack the nic is a tap interface that kvm attaches your
> instance to and hence you have offloaded the task of segmenting to the host
> cpu now ( I am only guessing, not sure).
>
>
Yes. KVM is using tap interfaces with virtio driver.

I would like to know if this is the case and using a better flavor and
> image would offer you better results without tinkering with the interface.
>
>
Images used are Ubuntu Trusty downloaded from
http://images.ubuntu.com/trusty/current and a Debian Wheezy tested
previously in another private cloud. No significant differences were found
using Ubuntu or Debian images.

Thanks Akilesh!

Alberto
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