RE: Slow network performance with KVM
> -----Original Message-----
> From: Bob Proulx [mailto:bob@proulx.com]
> Sent: Monday, December 17, 2012 8:15 PM
> To: debian-user@lists.debian.org
> Subject: Re: Slow network performance with KVM
>
> I forgot that this module is only available in later kernels! Sorry.
> It does not appear in Squeeze. It does exist in 2.6.39 because I did
> find it there. Here is data from a Sid machine that routinely gets
> updated and has a lot of history.
>
> $ locate vhost_net.ko
> /lib/modules/2.6.39-2-amd64/kernel/drivers/vhost/vhost_net.ko
> /lib/modules/3.0.0-2-amd64/kernel/drivers/vhost/vhost_net.ko
> /lib/modules/3.1.0-1-amd64/kernel/drivers/vhost/vhost_net.ko
> /lib/modules/3.2.0-1-amd64/kernel/drivers/vhost/vhost_net.ko
> /lib/modules/3.2.0-2-amd64/kernel/drivers/vhost/vhost_net.ko
> /lib/modules/3.2.0-3-amd64/kernel/drivers/vhost/vhost_net.ko
> /lib/modules/3.2.0-4-amd64/kernel/drivers/vhost/vhost_net.ko
>
> On Squeeze you would want to use a backported 3.2 kernel. It would be
> worthwhile to try it if you are suffering from this performance
> problem. Here are instructions:
I installed the backported 3.2.0 kernel and forced vhost-net module load @boot in /etc/modules. However, the VMs still suffer the same network issue and I don't see any vhost option for the kvm processes:
root@vmhost:~# ps -ef | grep '/usr/bin/kvm ' | head -1
105 2131 1 2 Dec17 ? 00:27:27 /usr/bin/kvm -S -M pc-0.12 -enable-kvm -m 256 -smp 1,sockets=1,cores=1,threads=1 -name hg -uuid 52f804ba-2371-8f8a-4956-01692dfce3f9 -nographic -nodefaults -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/hg.monitor,server,nowait -mon chardev=monitor,mode=readline -rtc base=utc -boot c -drive file=/dev/rootvg/virt-hg,if=none,id=drive-virtio-disk0,boot=on,format=raw -device virtio-blk-pci,bus=pci.0,addr=0x3,drive=drive-virtio-disk0,id=virtio-disk0 -device virtio-net-pci,vlan=0,id=net0,mac=52:54:00:4c:41:e5,bus=pci.0,addr=0x2 -net tap,fd=28,vlan=0,name=hostnet0 -chardev pty,id=serial0 -device isa-serial,chardev=serial0 -usb -device usb-tablet,id=input0 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4
> You might also want to try the backported newer versions of libvirt-bin
> kvm packages. There have been several improvements.
> However the internal PCI device numbering did change and this will
> prevent some VMs from starting due to conflicts until their xml
> configuration file has been updated. Either update the xml or recreate
> the VM. If you hit this problem I can clue you in as to the xml edit
> to make. It is simple but I forget off the top of my head at this
> moment.
>
> Bob
I will follow your advice and also try a newer version of kvm and libvirt. Since this is a development system, I'll have to schedule some downtime before I proceed with the upgrade. I'll write the effects here to the group as soon as I get a long enough time slot for the upgrade.
Thank you very much for the help.
Best regards
Bogdan Katynski
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