Software versus hardware shared-memory implementation: a case study

We compare the performance of software-supported shared memory on a general-purpose network to hardware-supported shared memory on a dedicated interconnect. Up to eight processors, our results are based on the execution of a set of application programs on a SGI 4D/480 multiprocessor and on TreadMarks, a distributed shared memory system that runs on a Fore ATM LAN of DECstation-5000/240s. Since the DECstation and the 4D/480 use the same processor, primary cache, and compiler, the shared-memory implementation is the principal difference between the systems. Our results show that TreadMarks performs comparably to the 4D/480 for applications with moderate amounts of synchronization, but the difference in performance grows as the synchronization frequency increases. For applications that require a large amount of memory bandwidth, TreadMarks can perform better than the SGI 4D/480. Beyond eight processors, our results are based on execution-driven simulation. Specifically, we compare a softw...