N I C K M A T H E W

Scheduling Algorithms for Real-Time Multiprocessor Systems

Outline

Multiprocessor Real-Time Systems

Scheduling Algorithms

Multiprocessor Scheduling

P-Fair Scheduling Algorithm

Multiprocessor Real-Time Systems

High computational demands

Telemedicine, Tracking Systems

Traditional Scheduling Assumptions

Single Processor

Scheduling Algorithms

Fixed-Priority Algorithm Rate Monotonic Scheduling (RMS)

Optimal fixed priority algorithm

At least 0.693 system utilization

Dynamic Priority Algorithm Earliest Deadline First (EDF)

Optimal dynamic-priority algorithm

* Liu & Layland, 1978

Multiprocessor Scheduling

"Schedule ji jobs with length li over

m processors such that none overlap“

Traditional Scheduling Algorithms

EDF, RMS – low processor utilization

Multiprocessor Scheduling

Approaches Partitioning

Uniprocessor

Low processor utilization

Bin Packing

NP-hard problem

Global Scheduling

Single priority-ordered queue

Low processor utlization

* J. Carpenter, S. Funk, et al [2]

P-Fair Scheduling Algorithm

Proportionate-Fair Scheduling * Baruah et al.

Global Scheduling Algorithm

Each task executes at uniform rate

P-Fair Scheduling Algorithm

Each task with weight w would receive w.L units of processor time over interval L

Each task allocated resource for x.e time units in each interval

Advantages

Avoids bin-packing problem

Handle dynamic events

task leaving & joining a system

Optimal

* J. Carpenter, S. Funk, et al [2]

Disadvantages

Degraded processor affinity

Preemption, Migration limit effectiveness

* J. Carpenter, S. Funk, et al [2]

Conclusion

Only known optimal approach (Srinivasan, 2003)

Basis for PD & PF algorithms

Other scheduling algorithms

Genetic Algorithms

Approximation Algorithms

Memetic Algorithms

References

[1] K. Ramamritham, J.A. Stankovic, and P.-F. Shiah, "Efficient Scheduling Algorithms for Real-Time Multiprocessor Systems," IEEE Trans. Parallel and Distributed Systems, vol. 1, no. 2, pp. 184194, Apr. 1990.

[2] J. Carpenter, S. Funk, et al. A categorization of real-time multiprocessor scheduling problems and algorithms. In J. Y. Leung, editor, Handbook on Scheduling Algorithms, Methods, and Models, page 30.130.19 , 2004.

[3] S. Baruah, N. Cohen, C. Plaxton and D. Varvel, "Proportionate Progress: A Notion of Fairness in Resource Allocation", Algorithmica15(6), pgs. 600-625, 1996.

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