Thread Placement on the Intel Paragon: Experimentation and Modeling

In multicomputer architectures where communication latency is distance independent, thread placement is expected to have a limited impact on an application's performance. However, contention for network links may significantly increase communication latency. In this paper, the impact of thread placement on application performance is demonstrated on a wormhole routed multicomputer, the Intel Paragon, in the presence of link contention. A communication intensive synthetic workload is used to stress test the effects of contention on communication latency induced by thread placement. It is shown by means of experimentation and modeling that appropriate thread placement patterns minimize contention in the system's interconnection network and improve performance. The results obtained with the synthetic workload are then applied to an actual matrix transposition application. Performance comparisons under two operating systems, OSF/1 release 1.2 and SUNMOS, are presented. The relevance of stra..