On Mon, Jan 23, 2017 at 07:50:31PM -0800, Alexei Starovoitov wrote: > On Tue, Jan 24, 2017 at 05:33:37AM +0200, Michael S. Tsirkin wrote: > > On Mon, Jan 23, 2017 at 05:02:02PM -0800, Alexei Starovoitov wrote: > > > Frankly I don't understand the whole virtio nit picking that was > > > happening. > > > imo virtio+xdp by itself is only useful for debugging, development and > > > testing > > > of xdp programs in a VM. The discussion about performance of virtio+xdp > > > will only be meaningful when corresponding host part is done. > > > Likely in the form of vhost extensions and may be driver changes. > > > Trying to optimize virtio+xdp when host is doing traditional skb+vhost > > > isn't going to be impactful. > > > > Well if packets can be dropped without a host/guest > > transition then yes, that will have an impact even > > with traditional skbs. > > I don't think it's worth optimizing for though, since the speed of drop > matters for ddos-like use case
It's not just drops. adjust head + xmit can handle bridging without entering the VM. > and if we let host be flooded with skbs, > we already lost, since the only thing cpu is doing is allocating skbs > and moving them around. Whether drop is happening upon entry into VM > or host does it in some post-vhost layer doesn't change the picture much. > That said, I do like the idea of offloading virto+xdp into host somehow.
