Re: [Qemu-devel] Is IOThread for virtio-net a good idea?

[Jason Wang <jasowang@redhat.com>]

On 2019/2/12 下午2:48, Jason Wang wrote:
>
> On 2019/2/11 下午9:40, Anton Kuchin wrote:
>> As far as I can see currently IOThread offloading is used only for 
>> block devices and all others are emulated by main thread.
>>
>> I expect that network devices can also benefit from processing in 
>> separate thread but I couldn't find any recent work in this 
>> direction. I'm going to implement a PoC but I want to ask if you know 
>> any previous attempts and do you know why it can be a total waste of 
>> time. Are there fundamental obstacles that prevent network emulation 
>> handling in IOThread?
>>
>
> I think there're no obstacles.
>
> The only question is whether or not you need to support legacy 
> networking backends. If the answer is yes, you need to convert them 
> not to assume context of Main Loop. But I don't think it's worth to 
> support them. We should focus on high speed solution like linking dpdk.
>
> Another issue is the virtio implementation. Dpdk has virtio library 
> which is pretty optimized, we should consider to use it. But last time 
> I check the code, it was tightly coupled with AF_UNIX transport of 
> vhost-user. We may want to decouple it out of dpdk. Of course we can 
> do it our own as well. (Yes I know there's a vhost-user 
> implementation, but it was not optimized for performance).
>
> I do have some prototype that is based on vhost-scsi-dataplane with a 
> TAP backend. I can send it to you if you wish.
>

Note, what I did is a vhost implementation inside IOThread. It doesn't 
use qemu memory core (which is slow for e.g 10Mpps) but vhost memory table.

Thanks


> Thanks
>
>