Using feedback to control tree saturation in multistage interconnection networks

Abstract

In this paper, we propose the use of feedback schemes in multiprocessors which use an interconnection network with distributed routing control. We show that by altering system behavior so as to minimize the occurrence of a performance-degrading situation in the network, the overall throughout of the system can be improved. As an example, we have considered the problem of tree saturation caused by hot spots in multistage interconnection networks. Tree saturation degrades the performance of all processors in a system, including those not participating in the hot spot activity. We see that feedback schemes can be used to control tree saturation, reduce degradation to memory requests that are not to the hot memory module and increase overall system bandwidth. As a companion to feedback schemes, damping schemes are also considered. Simulation studies presented in this paper show that feedback schemes can improve overall system performance significantly in many cases.