Approximate Formulas for Characteristics of Multichannel LIFO Preemptive-Resume Priority Queueing System

This paper considers a multichannel preemptive-resume priority queueing system with a Poisson input and an arbitrary service time distribution depending on the priority of job. Jobs of the same priority are serviced according to the LIFO rule. If, at moment of job arrival, all servers are busy, and at least one server is busy with the service of a job of a not higher than the priority of arriving job, then the service of a job is preempted such that the priority of preempted job is lowest from the priorities of the jobs in service. The service of a preempted job is resumed later. The paper proposes approximate formulas for the sojourn time of a prescribed priority job and some other characteristics of the system.