To schedule or to execute: Decision support and performance implications

This paper addresses a fundamental trade-off in dynamic scheduling between the cost of scheduling and the quality of the resulting schedules. The time allocated to scheduling must be controlled explicitly, in order to obtain good-quality schedules in reasonable times. As task constraints are relaxed , the algorithms proposed in this paper increase scheduling complexity to o ptimize longer and obtain high-quality schedules. When task constraints are tightened, the algorithms adjust scheduling complexity to reduce the adver se effect of long scheduling times on the schedule quality. We show that ta king into account the scheduling time is crucial for honoring the deadlines of scheduled tasks. We investigate the performance of our algorithms in tw o scheduling models: one that allows idle-time intervals to exist in the sc hedule and another that does not. The model with idle-time intervals has im portant implications for dynamic scheduling which are discussed in the pape r. Experimental evaluation of the proposed algorithms shows that our algori thms outperform other candidate algorithms in several parameter configurati ons.