Re: [Qemu-devel] vhost-pci and virtio-vhost-user

[Wei Wang]

On 01/15/2018 04:34 PM, Jason Wang wrote:
> On 2018年01月15日 15:59, Wei Wang wrote:
> > On 01/15/2018 02:56 PM, Jason Wang wrote:
> > > On 2018年01月12日 18:18, Stefan Hajnoczi wrote:
> > > >
> > >
> > > I just fail understand why we can't do software defined network or 
> > > storage with exist virtio device/drivers (or are there any 
> > > shortcomings that force us to invent new infrastructure).
> >
> > Existing virtio-net works with a host central vSwitch, and it has the 
> > following disadvantages:
> > 1) long code/data path;
> > 2) poor scalability; and
> > 3) host CPU sacrifice
>
> Please show me the numbers.

Sure. For 64B packet transmission between two VMs: vhost-user reports 
~6.8Mpps, and vhost-pci reports ~11Mpps, which is ~1.62x faster.


> > Vhost-pci solves the above issues by providing a point-to-point 
> > communication between VMs. No matter how the control path would look 
> > like finally, the key point is that the data path is P2P between VMs.
> >
> > Best,
> > Wei
>
> Well, I think I've pointed out several times in the replies of 
> previous versions. Both vhost-pci-net and virtio-net is an ethernet 
> device, which is not tied to a central vswitch for sure. There're just 
> too many methods or tricks which can be used to build a point to point 
> data path.


Could you please show an existing example that makes virtio-net work 
without a host vswitch/bridge?
Could you also share other p2p data path solutions that you have in 
mind? Thanks.


Best,
Wei