INTEGRATION OF MESSAGE-PASSING AND SHARED-MEMORY IN THE STANFORD FLASH MULTIPROCESSOR

The advantages of using message passing over shared memory for certain types of communication and synchronization have provided an incentive to integrate both models within a single architecture. A key goal of the FLASH (FLexible Architecture for SHared memory) project at Stanfor d is to achieve the integration while maintaining a simple and efficie nt design. This paper presents the hardware and software mechanisms in FLASH to support various message passing protocols. We achieve low ov erhead message passing by delegating protocol functionality to the pro grammable node controllers in FLASH and by providing direct user-level access to this messaging subsystem. In contrast to most earlier work, we provide an integrated solution that handles the interaction of the messaging protocols with virtual memory, protected multiprogramming, and cache coherence. Detailed simulation studies indicate that this sy stem can sustain message-transfers rates of several hundred megabytes per second, effectively utilizing projected network bandwidths for nex t generation multiprocessors.