Comparative Performance Evaluation of Hot Spot Contention Between MIN-Based and Ring-Based Shared-Memory Architectures

Hot spot content ion on a network-based sharedmemory architecture occurs when a large number of processors try to access a globally shared variable across the network. While Multistage Interconnection Network (MIN) and Hierarchical Ring (HR) structures are two important bases on which to build large scale shared-memory multiprocessors, the different interconnection networks and cache/memory systems of the two archltectures respond very differently to network bottleneck situations. In this paper, we present a comparative performance evaluation of hot spot effects on the MIN-based and HR-based sharedmemory architectures. Both nonblocking MIN-based and HRbased architectures are classified, and analytical models are described for understanding network differences and for evaluating hot spot performance on both architectures. The analytical comparisons indicate that HR-based architectures have the potential to handle various contentions caused by hot spots more efficiently than MIN-based architectures. Intensive performance measurements on hot spots have been conducted on the BBN TC2000 (MIN-based) and the KSRl (HR-based) machines. Performance experiments were also conducted on the practical experience of hot spots with respect to synchronization lock algorithms. The experimental results are consistent with the analytical models, and present practical observations and an evaluation of hot spots on the two types of architectures.