Efficient approximation for models of multiprogramming with shared domains

Abstract

Queueing network models of multiprogramming systems with memory constraints and multiple classes of jobs are important in representing large commercial computer systems. Typically, an exact analytical solution of such models is unavailable, and, given the size of their state space, the solution of models of this type is approached through simulation and/or approximation techniques. Recently, a computationally efficient iterative technique has been proposed by Brandwajn, Lazowska and Zahorjan for models of systems in which each job is subject to a separate memory constraint, i.e., has its own memory domain. In some important applications, it is not unusual, however, to have several jobs of different classes share a single memory “domain” (e.g., IBM's Information Management System). We present a simple approximate solution to the shared domain problem. The approach is inspired by the recently proposed technique which is complemented by a few approximations to preserve the conceptual simplicity and computational efficiency of this technique. The accuracy of the results is generally in fair agreement with simulation.