[wassenaar10]

The performance overhead of multiprocessing is pretty high, to the point that you really have to take care to ensure that whatever problem you're solving with multiprocessing is large and parallel enough to justify it, otherwise your multiprocessing solution may very well be slower than your single-process one.

That's not to say it's useless, it's a nice tool to have in the standard library, but if you're coming from one of the many mainstream programming languages with lightweight threading libraries which make it much easier to take advantage of parallelism it's easy to get frustrated at both python's standard threading and multiprocessing libraries for their respective shortcomings, at least in their CPython implementations.