[livueta]

Probably fits your requirements. One interesting thing to remember about FreeBSD is that a lot of commercial users of it use it as a base for enterprise appliances (think storage arrays, proxies, DPI boxes, etc). This means that the project as a whole is fairly beholden to these users, who provide a nice chunk of the project's funding and many of its professional committers.

As a result, the project is less focused on desktop use cases and free software/security at any cost ideology than on a) not breaking all the complicated crap built on top of it and b) providing drop-in perf and stability enhancements.

So, yeah, if you want a performant network stack and a consolidated kernel/userland that values stability (both in the "years of uptime" and the no "hey guys, we're jumping to systemd!" senses of the word) FreeBSD is a good option. As a bonus, FreeBSD's manpages are really really nice and give you basically everything you need to get down and do some serious systems programming or box-tuning. Go check out `man 7 tuning`.

Anecdotally, during my years as a sysadmin I ran a bunch of FreeBSD boxes alongside a bunch of Linux boxes - similar hardware, similar tasks. The FreeBSD boxes would routinely run for literal years without a hiccup, while we never got a similar level of stability from any other OS.