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

[Gonglei (Arei)]

> 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
 
> 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