Pre-emptive multitasking is fully supported. Its a policy decision above the Mill pay grade whether all threads are first class or some are part of thread groups that are scheduled as a group in the usual way. Task switch on a Mill is very cheap because all the save/restore is done for you by the spiller, but there is still the trip through the ready queue and the priority scheduling etc. The point to portals and stacklets is to have the protection benefits of separate processes without the IPC costs when the IPC is in fact being done co-routine style and so can be replaced by calls, as is the great majority of cases.
Reply To: Security Ivan Godard