I could be wrong but I was under the impression that the four major JVM gc's all had a stop the world phase and while multi-processing is implementation specifi

I could be wrong but I was under the impression that the four major JVM gc's all had a stop the world phase and while multi-processing is implementation specific I'm not aware of a robust pre-emptive multiprocessing model built for the JVM. If you have robust examples that are contrary to this I'd be interested in hearing about them.