How does Spacy's multiprocessing work?

I'm working on a project that uses spacy's coreference library neuralcoref, which is really slow. I haven't been able to figure out how to put it on GPUs yet, so I've been trying to use spacy's multiprocessing functionality by creating a pipe with n_process >1. This doesn't seem to speed things up at all though. Why might that be? And what can I do to speed things up?

languagetechnology multiprocessing spacy work