Re: [Qemu-devel] virtio-net performance on mach-virt.

[Giridhar Maruthy]

Hi Paolo,

Many apologies to you, I did not reply to you earlier. I somehow
missed your email.

The command I used was

sudo qemu-system-arm -enable-kvm -kernel zImage -machine type=virt
-display none -cpu cortex-a15 -m 512 -append 'console=ttyAMA0
root=/dev/vda ip=192.168.42.24:192.168.42.1:192.168.42.1:255.255.255.0:::off
rw' -serial stdio -drive file=/dev/sdb2,if=none,cache=writeback,id=foo
-device virtio-blk-device,drive=foo -netdev tap,id=br0,vhost=on
-device virtio-net-device,netdev=br0

Also, I had missed out on this important message among the huge kernel logs
"qemu-system-arm: unable to start vhost net: 38: falling back on
userspace virtio"

I observed that the cause is that set_guest_notifiers is not
implemented in virtio-mmio in qemu.
So I guess either this has to be implemented in virtio-mmio or to use
virtio-pci to move further.

Thanks,
Giridhar


On 31 October 2013 15:19, Paolo Bonzini <address@hidden> wrote:
> Il 31/10/2013 04:32, Giridhar Maruthy ha scritto:
>> On 30 October 2013 22:12, Paolo Bonzini <address@hidden> wrote:
>>> Il 30/10/2013 15:40, Giridhar Maruthy ha scritto:
>>>> Hi All,
>>>>
>>>> I tried to measure the network performance of guest (mach-virt) with
>>>> virtio-net on an ARM host platform (Samsung exynos). The qemu version
>>>> is 1.6.50.
>>>>
>>>> I found that with 1GbE NIC on the host, the host iperf gave a speed of
>>>> 847Mbits/sec when a local dhcp server was used as a iperf server.
>>>>
>>>> But the guest gave a speed of 478Mbits/sec which is around 56% compared to 
>>>> host.
>>>>
>>>> What is the typical guest network efficiency compared to host with 
>>>> virtio-net?
>>>> Any ideas would be helpful.
>>>
>>> Were you using vhost?
>>
>> Yes, I did use vhost in the host kernel configuration and passed
>> vhost=on in qemu, but there is no difference in the performance of
>> guest.
>
> What's your command line?
>
> Paolo
>