[libvirt-users] poor network performance to one of two guests
Philip Nelson
philip at whatsbeef.net
Sun Jan 31 04:14:52 UTC 2010
G'day, I have a host running two kvm guests. One of them gets very poor network
performance, testing with iperf I get ~10MBit/sec to guest A, >400MBit/sec to
guest B (running iperf between the host/guest). Both guests are using the same
bridge:
Guest A:
<interface type='bridge'>
<mac address='54:52:00:75:24:91'/>
<source bridge='br0'/>
</interface>
Guest B:
<interface type='bridge'>
<mac address='54:52:00:3b:13:2a'/>
<source bridge='br0'/>
</interface>
The host and guests are debian lenny, the host I have updated with some packages
from backports.org. The host is running 2.6.30 with qemu-kvm 0.12.2 and libvirt
0.7.5. The host has 8gig ram and a quad core xeon cpu. Each guest is given one
vcpu, guest A has 3gig memory, guest B 1gig.
I have tried starting them in a different order so that one gets vnet0 and one
gets vnet1, it doesn't make a difference, it's always guest A that is slow.
I'm a bit stuck here, I don't know what else to try. Below is some information
for the host/guests, not sure what might be helpful:
ifconfig eth1/br0/vnet0/1 output from the host:
eth1 Link encap:Ethernet HWaddr 00:25:64:3b:65:de
inet6 addr: fe80::225:64ff:fe3b:65de/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:7828 errors:0 dropped:0 overruns:0 frame:0
TX packets:6664 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4034843 (3.8 MiB) TX bytes:466838 (455.8 KiB)
Interrupt:17
br0 Link encap:Ethernet HWaddr 00:25:64:3b:65:de
inet addr:192.168.108.1 Bcast:192.168.108.255 Mask:255.255.255.0
inet6 addr: fe80::225:64ff:fe3b:65de/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:110047 errors:0 dropped:0 overruns:0 frame:0
TX packets:111420 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:5744145 (5.4 MiB) TX bytes:870431296 (830.1 MiB)
vnet0 Link encap:Ethernet HWaddr 72:48:bc:10:45:d4
inet6 addr: fe80::7048:bcff:fe10:45d4/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:107881 errors:0 dropped:0 overruns:0 frame:0
TX packets:581468 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:7129781 (6.7 MiB) TX bytes:873414210 (832.9 MiB)
vnet1 Link encap:Ethernet HWaddr 36:20:fc:df:52:66
inet6 addr: fe80::3420:fcff:fedf:5266/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:7918 errors:0 dropped:0 overruns:0 frame:0
TX packets:21692 errors:0 dropped:0 overruns:16236 carrier:0
collisions:0 txqueuelen:500
RX bytes:534843 (522.3 KiB) TX bytes:32575099 (31.0 MiB)
# brctl show:
bridge name bridge id STP enabled interfaces
br0 8000.0025643b65de no eth1
vnet0
vnet1
# lsmod | grep kvm
kvm_intel 47336 6
kvm 159032 1 kvm_intel
ifconfig output from guest A:
eth0 Link encap:Ethernet HWaddr 54:52:00:75:24:91
inet addr:192.168.108.100 Bcast:192.168.108.0 Mask:255.255.255.0
inet6 addr: fe80::5652:ff:fe75:2491/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:21708 errors:0 dropped:0 overruns:0 frame:0
TX packets:8155 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:32576795 (31.0 MiB) TX bytes:553329 (540.3 KiB)
Interrupt:10
ifconfig output from guest B:
eth0 Link encap:Ethernet HWaddr 54:52:00:3b:13:2a
inet addr:192.168.108.101 Bcast:192.168.108.0 Mask:255.255.255.0
inet6 addr: fe80::5652:ff:fe3b:132a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:582733 errors:0 dropped:18 overruns:0 frame:0
TX packets:109328 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:865856730 (825.7 MiB) TX bytes:7230359 (6.8 MiB)
Interrupt:10 Base address:0xe000
Here is the guest A definition:
<domain type='kvm'>
<name>guestA</name>
<uuid>a32a9d3b-e5ae-5943-c6db-52bc118f99c6</uuid>
<memory>3145728</memory>
<currentMemory>3145728</currentMemory>
<vcpu>1</vcpu>
<os>
<type arch='x86_64' machine='pc'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/bin/kvm</emulator>
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/guestA'/>
<target dev='vda' bus='virtio'/>
</disk>
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/guestA-data.img'/>
<target dev='vdb' bus='virtio'/>
</disk>
<interface type='bridge'>
<mac address='54:52:00:75:24:91'/>
<source bridge='br0'/>
</interface>
<serial type='pty'>
<target port='0'/>
</serial>
<console type='pty'>
<target port='0'/>
</console>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/>
</devices>
</domain>
And guest B:
<domain type='kvm'>
<name>guestB</name>
<uuid>1816a68e-929c-0b36-41ac-a380a4062298</uuid>
<memory>1048576</memory>
<currentMemory>1048576</currentMemory>
<vcpu>1</vcpu>
<os>
<type arch='x86_64' machine='pc'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/bin/kvm</emulator>
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/guestB'/>
<target dev='vda' bus='virtio'/>
</disk>
<disk type='file' device='disk'>
<source file='/var/lib/libvirt/images/guestB-data.img'/>
<target dev='vdb' bus='virtio'/>
</disk>
<interface type='bridge'>
<mac address='54:52:00:3b:13:2a'/>
<source bridge='br0'/>
</interface>
<serial type='pty'>
<target port='0'/>
</serial>
<console type='pty'>
<target port='0'/>
</console>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='-1' autoport='yes' keymap='en-us'/>
</devices>
</domain>
Any help would be greatly appreciated.
-- Philip
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