You can go fast if you don't do anything fancy with the interface. If you say, want bridged networking for your VMs and add your 10G interface to virbr0, poof,

You can go fast if you don't do anything fancy with the interface. If you say, want bridged networking for your VMs and add your 10G interface to virbr0, poof, a good chunk of your acceleration vanishes right there. Routing and firewalling also cost you a lot. There are ways to deal with this with eg, virtual functions, but the point is that even on modern hardware, 10G can be no longer a foolproof thing to have working at full capacity. You may need to actually do a fair amount of tweaking to have things perform well.