Re: [Qemu-devel] [question] virtio-net-device and multi-queue option

[Eric Auger <eric.auger@linaro.org>]

On 09/19/2014 04:30 AM, Gonglei (Arei) wrote:
>> From: Eric Auger [mailto:eric.auger@linaro.org]
>> Sent: Friday, September 19, 2014 10:23 AM
>> To: Gonglei (Arei); qemu list; Michael S. Tsirkin
>> Subject: Re: [Qemu-devel] [question] virtio-net-device and multi-queue option
>>
>> On 09/19/2014 03:42 AM, Gonglei (Arei) wrote:
>>>> Subject: [Qemu-devel] [question] virtio-net-device and multi-queue option
>>>>
>>>> Hi,
>>>>
>>>>
>>>> I am currently doing some benchmarks using virtio-net-device using
>>>> virtio-mmio (non PCI) with qemu_system_arm with KVM. Purpose is to
>>>> compare with device passthrough performance.
>>>>
>>>> I heard about the availability of a multi-queue option that greatly
>>>> improves the performance but I currently fail in enabling it.
>>>>
>>>> Please could someone explain me how to turn that feature on? My current
>>>> virtio-net options simply are:
>>>>
>>>>         -netdev tap,id=tap0,ifname="tap0" \
>>>>         -device virtio-net-device,netdev=tap0
>>>>
>>>
>>> There are some steps:
>>>
>>>  1. create multi-queue netdev device, such as tap device (you can
>>>    use "ip tuntap" command, or libvirt), something like as below:
>>>     ip tuntap add tap_1 mode tap multi_queue
>>>  2. pass corresponding parameters in QEMU command line:
>>>    -netdev
>> type=tap,ifname=tap_q,id=net1,vhost=on,vhostforce=on,queues=4,script= \
>>>    -device virtio-net-device,netdev=net1,mq=on,vectors=9
>>
>> Hi Gonglei,
>>
>> Thanks for your quick reply.
>>
>> Definitively I have not gone through step 1! Nethertheless I am a but
>> dubious about the fact the mq property does not seem to exist for my
>> virtio-net-device. I get
>>
>> qemu-system-arm: -device
>> virtio-net-device,netdev=tap0,mq=on,mac=52:54:00:12:34:56: Property
>> '.mq' not found
>>
> Sorry, my typo. :(
> 
> It should be "virtio-net-pci", not "virtio-net-devcie" 
> 
> BTW, You can use help command to get a devices properties:
> 
> # ./qemu-system-x86_64 -device virtio-net-pci,? 
> [...] 
> virtio-net-pci.mq=on/off
> [...]
Hi Gonglei,

I fear I can only use virtio-net-device since I only have VIRTIO-MMIO in
my machine file and no PCI bus.

The mq property does not seem to be supported for virtio-net-device as
reported by

sudo arm-softmmu/qemu-system-arm -M virt -device virtio-net-device,?
virtio-net-device.tx=str
virtio-net-device.x-txburst=int32
virtio-net-device.x-txtimer=uint32
virtio-net-device.bootindex=int32
virtio-net-device.netdev=netdev
virtio-net-device.vlan=vlan
virtio-net-device.mac=macaddr

Thanks

Best Regards

Eric

> 
> Best regards,
> -Gonglei
> 
>> Best Regards
>>
>> Eric
>>>
>>>> Also are there any "easy" tunings I can play with to try to reach the
>>>> best performance.
>>>>
>>>
>>> You can consider that using irq binding, core binding, vhost-net? etc..
>>>
>>> Best regards,
>>> -Gonglei
>>>
>>>> Thank you in advance
>>>>
>>>> Best Regards
>>>>
>>>> Eric
>>>
>