[pve-devel] bad virtio nic performance on kvm smp guests with debian squeeze kernel

[Martin Maurer]

Hi,

we have significant network performance with issue with virtio_net in Debian Squeeze KVM guests, with more than one core assigned.

I test:
> wget -O /dev/null http://mirror/proxmox-ve_2 .2-7f9cfa4c-28.iso

KVM guest (4 core) with e1000 Squeeze (amd64): 64.3 MB/s
KVM guest (4 core) with virtio Squeeze (amd64): 7.34 MB/s
KVM guest (1 core) with virtio Squeeze (amd64): 75.3 MB/s

Kernel used in KVM guest: 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64 GNU/Linux
modinfo virtio_net
 
filename:       /lib/modules/2.6.32-5-amd64/kernel/drivers/net/virtio_net.ko
license:        GPL
description:    Virtio network driver
alias:          virtio:d00000001v*
depends:        virtio
vermagic:       2.6.32-5-amd64 SMP mod_unload modversions
parm:           napi_weight:int
parm:           csum:bool
parm:           gso:bool

Proxmox VE as KVM guest is not affected, also newer Debian Kernel (e.g. Wheezy) are working without problems. 

Any ideas?

Martin