Hardware assist for distributed shared memory

The use of software implemented distributed shared memory (SDSM) to provide shared memory programming environments on networks of workstations and message-passing parallel computers has become quite popular. However, the memory reference patterns of many shared memory programs lead to poor performance on such systems. The authors propose hardware assist to improve the performance of SDSM systems faced with problematic reference patterns. An example of such a system is described. Operating system software in Mach is used to provide internode sharing in the example system, but is assisted through hardware support for maintaining update-based coherence of replicated pages. Simulations driven by hardware-collected parallel reference traces are used to provide an indication of the expected performance of the system