Parallel Performance Project Research Paper

Research Paper

Communication in the KSR1 MPP: Performance Evaluation Using Synthetic Workload Experiments
Eric L. Boyd and Edward S. Davidson
Proceedings of the International Conference on Supercomputing, pp 166-175.

Abstract

We have developed an automatic technique for evaluating the communication performance of massively parallel processors (MPPs). Both communication latency and the amount of communication are investigated as a function of a few basic parameters that characterize an application workload. Parameter values are captured in an automatically generated sparse matrix that multiplies a dense vector in the synthetic workload. Our approach is capable of explaining the degradation of processor performance caused by communication.

Using the Kendall Square Research KSR1 MPP as a case study, we demonstrate the effectiveness of the technique through a series of experiments used to characterize the communication performance. We show that read and write communication latencies vary from 150 to 180 and from 80 to 100 processor cycles, respectively. We show that the read communication latency approximates a linear function of the total system communication (in subpages), write communication approximates a linear function of the number of distinct shared subpages, and that KSRUs automatic update feature is effective in reducing the number of read communications given careful binding of threads to processors.