Resource reclaiming in hard real-time systems with static and dynamic workloads

The paper addresses resource reclaiming in the context of non-preemptive priority list scheduling for hard real-time systems. Such scheduling is inherently susceptible to multiprocessor timing anomalies. The authors present low overhead run-time stabilization methods for a general tasking model that allows phantom tasks as a mechanism to model processor external events. A family of scheduling algorithms is defined, that guarantees run-time stabilization for systems consisting of tasks with hard and soft deadlines. The later, i.e. soft tasks, may arrive dynamically. Stabilization is addressed in the context of dynamic and static task to processor allocation. Previous stabilization methods, focused on a priori stabilization for static workloads with dynamic task to processor allocation, thus cannot support this general scheduling model. By taking advantage of run-time information, the stabilization algorithms use the scan-window approach to prevent instability from occurring. Mechanisms are introduced that explicitly control the run-time behavior of tasks with hard deadlines. As a consequence, processor resources become available that can be used to improve processor utilization and response time of soft tasks. The resulting scan algorithms are intended for real world applications where low run-time overhead and a realistic task model are needed.

[1]  Gerhard Fohler,et al.  Joint scheduling of distributed complex periodic and hard aperiodic tasks in statically scheduled systems , 1995, Proceedings 16th IEEE Real-Time Systems Symposium.

[2]  Glenn K. Manacher,et al.  Production and Stabilization of Real-Time Task Schedules , 1967, JACM.

[3]  Rami G. Melhem,et al.  Enhancing real-time schedules to tolerate transient faults , 1995, Proceedings 16th IEEE Real-Time Systems Symposium.

[4]  Sang Lyul Min,et al.  An accurate worst case timing analysis technique for RISC processors , 1994, 1994 Proceedings Real-Time Systems Symposium.

[5]  Thomas M. Conte,et al.  The Susceptibility of Programs to Context Switching , 1994, IEEE Trans. Computers.

[6]  Charles U. Martel,et al.  On non-preemptive scheduling of period and sporadic tasks , 1991, [1991] Proceedings Twelfth Real-Time Systems Symposium.

[7]  Krithi Ramamritham,et al.  The Design of the Spring Kernel , 1987, RTSS.

[8]  John P. Lehoczky,et al.  An optimal algorithm for scheduling soft-aperiodic tasks in fixed-priority preemptive systems , 1992, [1992] Proceedings Real-Time Systems Symposium.

[9]  Axel Werner Krings.  Inherently stable priority list scheduling in an extended scheduling environment , 1993 .

[10]  P.L. Shaffer.  A multiprocessor implementation of real-time control for a turbojet engine , 1990, IEEE Control Systems Magazine.

[11]  Chris J. Walter,et al.  The MAFT Architecture for Distributed Fault Tolerance , 1988, IEEE Trans. Computers.

[12]  Krithi Ramamritham,et al.  Resource Reclaiming in Multiprocessor Real-Time Systems , 1993, IEEE Trans. Parallel Distributed Syst..

[13]  Alan Burns,et al.  Scheduling slack time in fixed priority pre-emptive systems , 1993, 1993 Proceedings Real-Time Systems Symposium.

[14]  Ronald L. Graham,et al.  Bounds on Multiprocessing Timing Anomalies , 1969, SIAM Journal of Applied Mathematics.

[15]  Jitender S. Deogun,et al.  Inherently stable real-time priority list dispatchers , 1994, IEEE Parallel & Distributed Technology: Systems & Applications.

[16]  Krithi Ramamritham,et al.  Resource Reclaiming in Real-Time , 1990, RTSS.

[17]  R. M. Kieckhafer,et al.  Inherently stable priority list scheduling in systems with external delays , 1993, [1993] Proceedings of the Twenty-sixth Hawaii International Conference on System Sciences.

[18]  Kevin Driscoll,et al.  ARINC 659 scheduling: problem definition , 1994, 1994 Proceedings Real-Time Systems Symposium.

[19]  John P. Lehoczky,et al.  Algorithms for scheduling hard aperiodic tasks in fixed-priority systems using slack stealing , 1994, 1994 Proceedings Real-Time Systems Symposium.

[20]  Andy J. Wellings,et al.  Dual priority scheduling , 1995, Proceedings 16th IEEE Real-Time Systems Symposium.