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

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

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

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
>