my (flawed?) impression is, the OS implementation is heuristic. putting a process on a core is not much different than putting state in swap. it's not that important with nvram disks, but it's not that hard to keep your data out of swap. There's bound to be a way to keep a process on the fast core. Just do some useless work that keeps the process on the fast core. Or cooperate with the os to keep the critical process on the fast core.
