Abstract
Exact feasibility conditions for real-time system under preemptive fixed-priority systems are NP-hard and attempts have been made to lower the computation cost of such tests by restricting the set of scheduling points or applying lowest priority first approach. Under feasibility tests based on scheduling points, feasibility of a system is tested at all scheduling points starting with the lowest task period. However, it has been observed that it is very unlikely that the cumulative demand of a lower priority is addressed at such smaller points. Consequently, feasibility is tested at a huge number of scheduling points before the schedulability of a task is concluded. In this work, we show that it is more appropriate to test schedulability of a task at larger potential scheduling points instead of starting with smallest point. Since there is a logical OR involved in feasibility analysis at task level, schedulability of a task is affirmative when the CPU demand is fulfilled at any scheduling point or else the task is declared unschedulable. The complexity of our proposed solution is pseudo-polynomial, but our results are promising when the system utilization is low or when task periods vary largely.