Feasibility analysis of hard real-time periodic tasks
The problem of determining the feasibility of hard real-time periodic tasks is known to be co-NP-complete when there exists a task with relative deadline shorter than its period. Thus Processor Demand Approach (PDA) for synchronous task sets has been considered as a practical tool to solve the feasibility problem. PDA determines the feasibility of a task set by checking whether there exists a task whose deadline is missed by a certain time which is computed based on the characteristic of the task set. In this paper, we present a new method for feasibility test by combining PDA with the analysis methods for aperiodic scheduling. It is shown that the number of tests required of the new method to determine the feasibility is never greater than the smallest number of tests the existing algorithm requires. Although our method has pseudo-polynomial time complexity, experimental results show that the new method requires significantly less computation to determine feasibility.
feasibility processor demand schedulability real-time scheduling slack time