I was discussing this recently and the view was put that really this level of scalability was probably not worth the various sacrifices associated with the approach (our load balancing leaves something to be desired, for example). So as far as I know, most VMs these days just rely on posix style threads. Of course in that case your scalability will largely depend on your underlying kernel threads implementation.
Whether or not it's worth it depends on your needs. The lack of a highly scalable threading model in the current popular VMs is the reason why we have to use alternative architectures (like SEDA) to make truly scalable servers. Some of us would find it very valuable. ;-)
It seems apparent that directly mapping to the underlying thread system results in a VM that doesn't scale very well on any of the common architectures including both MS and Linux, perhaps a different approach would be better?
Craig
--Steve
