Determining an Optimal Secondary Storage Service Rate for the PASM Control System

One class of reconfigurable parallel processing systems is based on the use of a large number of processing elements which can be partitioned into multiple virtual machines. Each virtual machine is controlled by one or more control units. The multiple control units in such a system share a common secondary storage for programs. The control units use paging to transfer programs to their primary memories. One design problem is determining the optimal service rate for the secondary storage of the control units, where the "optimal" is characterized by maximum processor utilization. The PASM parallel processing system is used as a example system to study this problem. The implementation of virtual memory on the PASM control system memory hierarchy is discussed and a queueing network model for the memory hierarchy is developed. Based on assumed values for parameters that characterize the expected task environment, an optimal service rate is derived from the model. The values of the parameters in the model can be varied to determine the impact these changes would have on system performance. Simulation results verifying various aspects of the model are presented and the results are generalized.