RT Journal Article
JF IEEE Transactions on Software Engineering
YR 1997
VO 23
IS
SP 388
TI An Optimal Algorithm for Scheduling Soft Aperiodic Tasks in Dynamic-Priority Preemptive Systems
A1 Alfons Crespo,
A1 Ismael Ripoll,
A1 Ana García-Fornes,
K1 Dynamic scheduling theory
K1 hard real-time
K1 feasibility analysis
K1 slack scheduling
K1 soft aperiodic tasks
K1 dynamic.
AB <p><b>Abstract</b>—This paper addresses the problem of jointly scheduling tasks with both hard and soft real-time constraints. We present a new analysis applicable to systems scheduled using a priority preemptive dispatcher, with priorities assigned dynamically according to the EDF policy. Further, we present a new efficient on-line algorithm (the acceptor algorithm) for servicing aperiodic work load. The acceptor transforms a soft aperiodic task into a hard one by assigning a deadline. Once transformed, aperiodic tasks are handled in exactly the same way as periodic tasks with hard deadlines. The proposed algorithm is shown to be optimal in terms of providing the shortest aperiodic response time among fixed- and dynamic-priority schedulers. It always guarantees the proper execution of periodic hard tasks. The approach is composed of two parts: an off-line analysis and a run-time scheduler. The off-line algorithm runs in pseudopolynomial time <it>O</it>(<it>mn</it>), where <it>n</it> is the number of hard periodic tasks and <it>m</it> is the hyperperiod/min deadline.</p>
PB IEEE Computer Society, [URL:http://www.computer.org]
SN 0098-5589
LA English
DO 10.1109/32.601081
LK http://doi.ieeecomputersociety.org/10.1109/32.601081