Processor Virtualization and Migration for PVM

This paper describes research underway to deene and develop the next generation of PVM (Parallel Virtual Machine). Future versions of PVM will be modular and open so as to allow interoperability with other packages, such as distributed scheduling systems. We concentrate on one aspect of the work: providing virtualization of processors and transparent migration mechanisms within the message-passing programming model. Work migration is a key ingredient to allow good scheduling on a large, busy system. Two migration systems will be described. The rst is Migratable PVM (MPVM), which allows transparent migration at process granularity amongst homogeneous groups of processors. The system is functional and has run realistic applications. The second system is a multi-threaded version of PVM, where threads are disjoint and do not share data spaces. This again allows transparent migration. Local communication speeds and context-switch times are improved over process-level MPVM. Performance gures and semantic restrictions of both packages are given.