Joint scheduling of distributed complex periodic and hard aperiodic tasks in statically scheduled systems

In this paper we present algorithms for the joint scheduling of periodic and aperiodic tasks in statically scheduled distributed real-time systems. Periodic tasks are precedence constrained, distributed, and communicating over the nodes of the systems. Both soft and hard aperiodic tasks are handled. After a static schedule has been created in a first step, the algorithms determine the amount and distribution of unused resources and leeway in it. These are then used to incorporate aperiodic tasks into the schedule by shifting the periodic tasks' execution, without violating their feasibility. Run-time mechanisms are simple and require only little memory. Processors and communication nodes can be utilized fully. The algorithm performs on optimal online guarantee algorithm for hard aperiodic tasks of O(N). An extensive simulation study exhibits very high guarantee ratios for various load and deadline scenarios, which underlines the efficiency of our method.

[1]  John A. Stankovic,et al.  Dynamic end-to-end guarantees in distributed real time systems , 1994, 1994 Proceedings Real-Time Systems Symposium.

[2]  Krithi Ramamritham,et al.  Allocation and scheduling of complex periodic tasks , 1990, Proceedings.,10th International Conference on Distributed Computing Systems.

[3]  Alan Burns,et al.  Mode changes in priority preemptively scheduled systems , 1992, [1992] Proceedings Real-Time Systems Symposium.

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

[5]  Alan Burns,et al.  Mechanisms for enhancing the flexibility and utility of hard real-time systems , 1994, 1994 Proceedings Real-Time Systems Symposium.

[6]  Marco Spuri,et al.  Efficient aperiodic service under earliest deadline scheduling , 1994, 1994 Proceedings Real-Time Systems Symposium.

[7]  Aloysius Ka-Lau Mok,et al.  Fundamental design problems of distributed systems for the hard-real-time environment , 1983 .

[8]  Krithi Ramamritham,et al.  Evaluation of a flexible task scheduling algorithm for distributed hard real-time systems , 1985, IEEE Transactions on Computers.

[9]  John P. Lehoczky,et al.  On-line scheduling of hard deadline aperiodic tasks in fixed-priority systems , 1993, 1993 Proceedings Real-Time Systems Symposium.

[10]  Kevin Jeffay,et al.  Scheduling sporadic tasks with shared resources in hard-real-time systems , 1992, [1992] Proceedings Real-Time Systems Symposium.

[11]  G. Fohler,et al.  Realizing Changes of Operational Modes with a Pre Run-Time Scheduled Hard Real-Time System , 1993 .

[12]  Lui Sha,et al.  Priority Inheritance Protocols: An Approach to Real-Time Synchronization , 1990, IEEE Trans. Computers.

[13]  Chung Laung Liu,et al.  Scheduling Algorithms for Multiprogramming in a Hard-Real-Time Environment , 1989, JACM.

[14]  Hermann Kopetz,et al.  Sparse time versus dense time in distributed real-time systems , 1992, [1992] Proceedings of the 12th International Conference on Distributed Computing Systems.

[15]  Gerhard Fohler Analyzing a Pre Run-Time Scheduling Algorithm and Precedence Graphs , 1992 .

[16]  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.

[17]  Gerhard Fohler Flexibility in Statically Scheduled Real-Time Systems , 1994 .

[18]  Maryline Chetto,et al.  Some Results of the Earliest Deadline Scheduling Algorithm , 1989, IEEE Transactions on Software Engineering.

[19]  Sanjoy K. Baruah,et al.  Preemptively scheduling hard-real-time sporadic tasks on one processor , 1990, [1990] Proceedings 11th Real-Time Systems Symposium.

[20]  Jay K. Strosnider,et al.  ENHANCED APERIODIC RESPONSIVENESS IN HARD REAL-TIME ENVIRONMENTS. , 1987, RTSS 1987.

[21]  Maryline Chetto,et al.  Scheduling Periodic and Sporadic Tasks in a Real-Time System , 1989, Inf. Process. Lett..

[22]  Robert E. Tarjan,et al.  Scheduling Unit-Time Tasks with Arbitrary Release Times and Deadlines , 1981, SIAM J. Comput..

[23]  Gerhard Fohler,et al.  Issues in the static allocation and scheduling of complex periodic tasks , 1993 .

[24]  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.