QEMU

Installing libvirt-bin qemu slows host network

Bug #861141 reported by michael imelfort on 2011-09-28

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	QEMU	Invalid	Undecided	Unassigned

Bug Description

Installing the packages needed for qemu-kvm slows don network connectivity between two non-virtual machines. Uninstalling the packages does not restore the previous network speeds.

Hardware:
I have two identical machines (DELL poweredge R815), each with Broadcom NetXtreme II BCM57711 10-Gigabit PCIe connected via a 10G switch.
Each machine runs 4 socket 12 core AMD Opteron(tm) Processor 6174 and 128GB of ram

Software:
Both machines ar running ubuntu server 10.04 lts Kernels are:
Linux whitlam 2.6.32-28-server #55-Ubuntu SMP Mon Jan 10 23:57:16 UTC 2011 x86_64 GNU/Linux
Linux fraser 2.6.32-28-server #55-Ubuntu SMP Mon Jan 10 23:57:16 UTC 2011 x86_64 GNU/Linux

I have installed iperf on both machines and I am trying to install kvm on fraser.

The tests here involve running whitlam as the iperf server and fraser as the client.
On whitlam I run:
bioadmin@whitlam:~# iperf -sm

On fraser I run:
bioadmin@fraser:~# iperf -c whitlam -d

before installation I get:
bioadmin@whitlam:~# iperf -sm
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 5] local 10.168.48.14 port 5001 connected with 10.168.48.13 port 37960
------------------------------------------------------------
Client connecting to 10.168.48.13, TCP port 5001
TCP window size: 110 KByte (default)
------------------------------------------------------------
[ 6] local 10.168.48.14 port 49627 connected with 10.168.48.13 port 5001
Waiting for server threads to complete. Interrupt again to force quit.
[ 5] 0.0-10.0 sec 10.8 GBytes 9.23 Gbits/sec
[ 5] MSS size 1448 bytes (MTU 1500 bytes, ethernet)
[ 6] 0.0-10.0 sec 10.6 GBytes 9.11 Gbits/sec
[ 6] MSS size 1448 bytes (MTU 1500 bytes, ethernet)

Which is nice.

Next I run:

aptitude -y install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils kvm

Which results in:
bioadmin@whitlam:~# iperf -sm
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 4] local 10.168.48.14 port 5001 connected with 10.168.48.13 port 56405
------------------------------------------------------------
Client connecting to 10.168.48.13, TCP port 5001
TCP window size: 1.25 MByte (default)
------------------------------------------------------------
[ 6] local 10.168.48.14 port 57001 connected with 10.168.48.13 port 5001
Waiting for server threads to complete. Interrupt again to force quit.
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.0 sec 10.5 GBytes 9.00 Gbits/sec
[ 4] MSS size 1448 bytes (MTU 1500 bytes, ethernet)
[ 6] 0.0-10.0 sec 2.51 GBytes 2.15 Gbits/sec
[ 6] MSS size 1448 bytes (MTU 1500 bytes, ethernet)

Note that the connection from the machine with KVM installed (fraser) to the other machine (whitlam) is not affected. Only the connection from whitlam to fraser.

Both machines are fresh installs with nfs-common, and iperf installed.

I had problems with qemu version 0.12 and virtio_net so I was using Daniel Baumans ppa for virtualisation. But this problem occurs regardless of whether I do this or not.

I am happy to give versions of software but I have no idea which part could be causing this problem and installing kvm etc installs quite a few dependencies.

Please let me know if you need more information