Investigating Split Locks on x86-64

Cool investigation. This part perplexes me, though:

> Games have apparently been using split locks for quite a while, and have not created issues even on AMD’s Zen 2 and Zen 5.

For the life of me I don't understand why you'd ever want to do an atomic operation that's not naturally aligned, let alone one split across cache lines....

Split locks are weird. It’s never been obvious to me why you’d want to do them unless you are on a small core count system. When split lock detection rolled out for linux, it massacred perf for some games (which were probably min-maxing single core perf and didn’t care about noisy neighbor effects).

Frankly, I’m surprised split lock detection is enabled anywhere outside of multi-tenant clouds.