An analytic model of the HASP execution task monitor

Abstract

The HASP Execution Task Monitor periodically rearranges the OS/360 dispatching chain to give tasks preemptive execution priority in inverse order to that of their cpu utilization history. The effect is to keep the I/O bound tasks active and to prevent cpu bound tasks from locking out other tasks. This paper develops a simple model of the Execution Task Monitor and employs it to study the effectiveness of the monitor in improving system performance. A modified strategy for monitor control is investigated for the case of task execution in a memory heirarchy of varying speeds.