Parallel Shared-Memory Simulator Performance for Large ATM Networks

A performance comparison between an optimistic and a conservative parallel simulation kernel is presented. Performance of the parallel kernels is also compared to a central-event-list sequential kernel. A spectrum of ATM network and traffic scenarios representative of those used by ATM networking researchers are used for the comparison. Experiments are conducted with a cell-level ATM network simulator and an 18-processor SGI Power Challenge shared-memory multiprocessor. The results show the performance advantages of parallel simulation over sequential simulation for ATM networks. Speedups of 4-5 relative to a fast sequential kernel are achieved on 16 processors for several large irregular ATM benchmark scenarios and the optimistic kernel achieves 2 to 5 times speedup on all 7 benchmarks. However, the relative performance of the two parallel simulation kernels is dependent on the size of the ATM network, the number of traffic sources, and the traffic source types used in the simulation. For some benchmarks the best single point performance is provided by the conservative kernel even on a single processor. Unfortunately, the conservative kernel performance is susceptible to small changes in the modeling code and is outperformed by the optimistic kernel on 5 of the 7 benchmarks. The optimistic parallel simulation kernel thus provides more robust performance, but its speedup is limited by the overheads of its implementation, which make it approximately half the speed of the sequential kernel on one processor. These performance results represent the first comparative analysis of parallel simulation for a spectrum of realistic, irregular, low-granularity, communication network models.