High Priority Jobs Research Articles

On the Tradeoff Between Response and Preemption Costs in a Foreground-Background Computer Service Discipline

In computer operating systems where background jobs must occasionally be preempted in order to run high priority jobs, it is generally the case that efficient operation and rapid response to the high priority jobs are conflicting objectives. In this short paper a preemption scheme in which a delay is introduced is shown to provide the designer with the ability to trade off these two performance measures to any desired degree. A mathematical model is developed and results are derived for the mean high priority waiting time and a measure of operating efficiency. The paper concludes with a discussion of examples designed to illustrate how the above performance measures interact as a function of system parameters.

A method of using a general-purpose computer in an on-line time sharing application

When a computer is coupled to a real time operation as in process control, the work load on the machine may fluctuate widely depending on operating conditions. External phenomena demanding action will occur essentially at random with respect to the machine. To cope with peak conditions the machine must be adequately fast, and thus will have idle time when activity is low. The use of time sharing techniques or more properly equipment sharing, allows the computer to utilize any idle time by having alternative jobs of lower priority, higher priority jobs having an interrupt facility on the machine. An engineering and programming method has been evolved of applying a computer to a process control system for on-line applications.