No mention of several other languages, like Erlang, which more or less scales up with available hardware threads. However, it doesn't even mention that just ha

No mention of several other languages, like Erlang, which more or less scales up with available hardware threads. However, it doesn't even mention that just having multiple cores on a chip isn't the same thing as having 2 chips, you still have shared memory and the bus, so having 2 cores is not going to be as fast as having 2 chips and 2 sets of memory in most cases, so adding cores is never going to be a linear increase. I believe right now that intel's hyperthreading needs to be turned off for some compile scenarios, as the collisions are too high either for memory or something else (at least 2 people I know who have to do huge compiles disable some of the hyperthreads). In short, I don't believe it's easy to just scale up on multi-core systems, regardless of language. Threads are a pretty dangerous way to do things, processes are much safer, but not all problems fall easily into a parallel model.