On 07/06/2009 12:34 PM, Martin Petermann wrote:
I'm currently looking at the network performance between two KVM guests
running on the same host. The host system is applied with two quad core
Xeons each 3GHz and 32G memory. 2G memory is assigned to the guests,
enough that swap is not used. I'm using RHEL 5.3 (2.6.18-128.1.10.el5)
on all the three systems:
____________________ ____________________
| | | |
| KVM guest | | KVM guest |
| ic01vn08man | | ic01vn09man |
|____________________| |____________________|
\ /
\ /
\ /
\ /
\ /
____\________/______
| |
| KVM host |
|ethernet bridge: br3|
|____________________|
On the host I've created a network bridge in the following way
[root@ic01in01man ~]# cat /etc/sysconfig/network-scripts/ifcfg-br3
DEVICE=br3
TYPE=Bridge
ONBOOT=yes
and installed the bridge with the commands
brctl addbr br3
ifconfig br3 up
Within the configuration files of the KVM guests I added the following
sections:
ic01vn08man.xml;
...
<interface type='bridge'>
<source bridge='br3'/>
<model type='virtio' />
<mac address="00:ad:be:ef:99:08"/>
</interface>
...
ic01vn09man.xml
...
<interface type='bridge'>
<source bridge='br3'/>
<model type='virtio' />
<mac address="00:ad:be:ef:99:09"/>
</interface>
...
Within the guests I have configured the network in the following way:
[root@ic01vn08man ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth3
# Virtio Network Device
DEVICE=eth3
BOOTPROTO=static
IPADDR=192.168.100.8
NETMASK=255.255.255.0
HWADDR=00:AD:BE:EF:99:08
ONBOOT=yes
[root@ic01vn09man ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth3
# Virtio Network Device
DEVICE=eth3
BOOTPROTO=static
IPADDR=192.168.100.9
NETMASK=255.255.255.0
HWADDR=00:AD:BE:EF:99:09
ONBOOT=yes
If I now test the network performance using the iperf tool
(http://sourceforge.net/projects/iperf/)
performance between two guests (iperf server is running on other guest
ic01vn08man/192.168.100.8: ic01vn09man<-> ic01vn08man):
[root@ic01vn09man ~]# nice -20 iperf -c 192.168.100.8 -t 60 -P 2 -l 2m
-w 131072
------------------------------------------------------------
Client connecting to 192.168.100.8, TCP port 5001
TCP window size: 256 KByte (WARNING: requested 128 KByte)
------------------------------------------------------------
[ 4] local 192.168.100.9 port 34171 connected with 192.168.100.8 port
5001
[ 3] local 192.168.100.9 port 34170 connected with 192.168.100.8 port
5001
[ 4] 0.0-60.1 sec 2.54 GBytes 363 Mbits/sec
[ 3] 0.0-60.1 sec 2.53 GBytes 361 Mbits/sec
[SUM] 0.0-60.1 sec 5.06 GBytes 724 Mbits/sec
results within the same guest (iperf server is running on the same
system: ic01vn08man<-> ic01vn08man):
[root@ic01vn08man ~]# nice -20 iperf -c 192.168.100.8 -t 60 -P 2 -l 2m
-w 131072
If you'll drop the -w 131072 you'll get over a 1G performance. Because
of bad buffering config you get lots of idle time (check your cpu
consumption).
Using netperf is more recommended. You can check one of vmware's
performance documents and check the huge difference of message size and
socket sizes.
------------------------------------------------------------
Client connecting to 192.168.100.8, TCP port 5001
TCP window size: 256 KByte (WARNING: requested 128 KByte)
------------------------------------------------------------
[ 4] local 192.168.100.8 port 55418 connected with 192.168.100.8 port
5001
[ 3] local 192.168.100.8 port 55417 connected with 192.168.100.8 port
5001
[ 3] 0.0-60.0 sec 46.2 GBytes 6.62 Gbits/sec
[ 4] 0.0-60.0 sec 45.2 GBytes 6.47 Gbits/sec
[SUM] 0.0-60.0 sec 91.4 GBytes 13.1 Gbits/sec
724 Mbits/sec is far away from what I have assumed. The host system is
connected with 10G ethernet and it would be necessary to have a similar
performance.
Regards
Martin
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