ONSET OF HOT SPOT CONTENTION.

Abstract

Nonuniform traffic distributions in a multistage network characterized by hot spots--destinations getting more than their share of traffic--can cause large reductions in the maximum throughput of the network. An analytical model is developed to predict how long a hot spot must be persist in shuffle/exchange networks before its full effect is felt. The model predicts that hot spots can disrupt network traffic severely in a very short time: 10 to 50 instruction execution times in a shared-memory machine. This result, verified by simulation, leads to the conclusion that if stringent measures are not taken to ensure uniformity, the performance of large multistage networks will be substantially worse than has been previously predicted.