Admission Control with Immediate Notification

When admission control is used, an online scheduler chooses whether or not to complete each individual job successfully by its deadline. An important consideration is at what point in time the scheduler determines if a job request will be satissed, and thus at what point the scheduler is able to provide notiication to the job owner as to the fate of the request. In the loosest model, often seen in real-time systems, such a decision can be deferred up until the job's deadline passes. In the strictest model, more suitable for customer-based applications, a scheduler would be required to give notiication at the instant that a job request arrives. Unfortunately there seems to be little existing research which explicitly studies the eeect of the notiication model on the performance guarantees of a scheduler. We undertake such a study by reexamining a problem from the literature. Speciically, we study the eeect of the notiication model on the non-preemptive scheduling of a single resource in order to maximize utilization. At rst glance, it appears severely more restrictive to compare a scheduler required to give immediate notiication to one which need not give any notiication. Yet we are able to present alternate algorithms which provide immediate notiication, while matching most of the performance guarantees which are possible by schedulers which provide no such notiication. In only one case are we able to give evidence that providing immediate notiication may be more diicult.