[abraininavat]

Maybe I'm missing something, but I'm not getting the point. It seems to me there's no fundamental difference between multiprocess with shared-memory regions for anything that needs to be shared and multithreaded with mostly thread-local storage plus some shared data. The kernel is going to multiplex your single-threaded processes among the available cores just the same as it will multiplex your multiple threads among the available cores.

Multi-threaded techniques, like mutexes, don’t scale on multi-core. Conversely, as Snort demonstrates, you can split a problem across multiple processes instead of threads, and still have multi-core code.

Synchronization is synchronization. There are inter-process synchronization primitives, including mutexes. And you can use lock-free synchronization in a single-process multi-threaded scenario.