When you're doing packet capture that normally costs one system call per packet, Netmap/DPDK/PF_RING are a clear win. But with TCP a single system call can send or receive many packets and TSO/LRO offloads help even more. I haven't seen any numbers about the benefits of kernel bypass for TCP; maybe SolarFlare has some.
I was about to point out solarflare's openonload. Its only compatible with an sfc nic though. With onload, i've seen about a 20% throughput increase when turning onload on.
No I don't think you are, at least for open source production grade. Intending to do some work on this when I get a chance. There is a talk at Eurobsdcon this year on using the FreeBSD network stack in userspace and Netbsd also an option, fixing locking and interrupts are issues with using these stacks out of kernel to get good performance as the environment is rather different.
