Intel is quite happy to ship CentOS Linux on its 64-core (256 hardware thread) Xeon Phi Knights landing dev boxes:

http://dap.xeonphi.com/

Here is Linux htop with 288 hardware threads on the higher end KL:

http://www.admin-magazine.com/var/ezflow_site/storage/images...

Linux is already pretty comfy at 48+ cores (and more), probably especially so on a single socket.

> What modifications are required to be made to the linux kernel/tcp stack to take advantage of 48+ cores, in order to achieve a more linear scalability?

https://xkcd.com/619/ isn't a joke.

Linux is the default operating system of huge NUMA systems with hundreds of CPUs / thousands of cores.

They have put quite a bit of work into scaling, but that doesn't mean it's perfect yet.

Yes, if you want to run TCP/IP on it. But if you have bucks for it, it takes just a little bit more cash to get rid of packet IO altogether, and the network stack overhead along with it.