On Windows multiprocessing is very poor due to lack of forking. This means for example no memory at all is shared; modules, data, external shared libraries etc

On Windows multiprocessing is very poor due to lack of forking. This means for example no memory at all is shared; modules, data, external shared libraries etc are all individually loaded by each subprocess. There are also some Windows-specific oddities that make using it a further pain (can’t remember the details). There is a project to effectively internalise multiprocessing by running separate interpreters inside one process. It’s meant to be cheaper than having separate modules too.