THE NEXUS APPROACH TO INTEGRATING MULTITHREADING AND COMMUNICATION

Lightweight threads have an important role to play in parallel systems : they can be used to exploit shared-memory parallelism, to mask commu nication and I/O latencies, to implement remote memory access, and to support task-parallel and irregular applications. In this paper, we ad dress the question of how to integrate threads and communication in hi gh-performance distributed-memory systems. We propose an approach base d on global pointer and remote service request mechanisms, and explain how these mechanisms support dynamic communication structures, asynch ronous messaging, dynamic thread creation and destruction, and a globa l memory model via interprocessor references. We also explain how thes e mechanisms can be implemented in various environments. Our global po inter and remote service request mechanisms have been incorporated in a runtime system called Nexus that is used as a compiler target for pa rallel languages and as a substrate for higher-level communication lib raries. We report the results of performance studies conducted using a Nexus implementation; these results indicate that Nexus mechanisms ca n be implemented efficiently on commodity hardware and software system s. (C) 1996 Academic Press, Inc.