During my tests, my server was able to process 3,500,000 SYN packets per second on one listener and still had available cpu cycles. That is about 2 to 3 order of magnitude what we had with older kernels.

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c3fc7ac9a0b978ee8538058743d21feef25f7b33