Report Number: CSL-TR-94-632
Institution: Stanford University, Computer Systems Laboratory
Title: The Benefits of Clustering in Shared Address Space Multiprocessors: An Applications-Driven Investigation
Author: Erlichson, Andrew
Author: Nayfeh, Basem A.
Author: Singh, Jaswinder Pal
Author: Olukotun, Kunle
Date: October 1994
Abstract: Clustering processors together at a level of the memory hierarchy in shared address space multiprocessors appears to be an attractive technique from several standpoints: Resources are shared, packaging technologies are exploited, and processors within a cluster can share data more effectively. We investigate the performance benefits that can be obtained by clustering on a range of important scientific and engineering applications. We find that in general clustering is not very effective in reducing the inherent communication to computation ratios. Clustering is more useful in reducing working set requirements in unstructured applications, and can improve performance substantially when small first level caches are clustered in these cases. This suggests that clustering at the first level cache might be useful in highly-integrated, relatively fine-grained environments. For less integrated machines such as current distributed shared memory multiprocessors, our results suggest that clustering is not very useful in improving application performance, and the decision about whether or not to cluster should be made on the basis of engineering and packaging constraints.