Annals of Operations Research
On-line scheduling in the presence of overload
SFCS '91 Proceedings of the 32nd annual symposium on Foundations of computer science
On the competitiveness of on-line real-time task scheduling
Real-Time Systems
Dover: An Optimal On-Line Scheduling Algorithm for Overloaded Uniprocessor Real-Time Systems
SIAM Journal on Computing
The design, implementation and evaluation of SMART: a scheduler for multimedia applications
Proceedings of the sixteenth ACM symposium on Operating systems principles
CPU reservations and time constraints: efficient, predictable scheduling of independent activities
Proceedings of the sixteenth ACM symposium on Operating systems principles
Adaptive rate controlled, robust video communication over packet wireless networks
Mobile Networks and Applications - Special issue: mobile multimedia communications
Adaptive source rate control for real-time wireless video transmission
Mobile Networks and Applications - Special issue: mobile multimedia communications
Approximating the throughput of multiple machines under real-time scheduling
STOC '99 Proceedings of the thirty-first annual ACM symposium on Theory of computing
SODA '94 Proceedings of the fifth annual ACM-SIAM symposium on Discrete algorithms
Flow and stretch metrics for scheduling continuous job streams
Proceedings of the ninth annual ACM-SIAM symposium on Discrete algorithms
Algorithms for Scheduling Independent Tasks
Journal of the ACM (JACM)
Improvements in throughout maximization for real-time scheduling
STOC '00 Proceedings of the thirty-second annual ACM symposium on Theory of computing
A unified approach to approximating resource allocation and scheduling
STOC '00 Proceedings of the thirty-second annual ACM symposium on Theory of computing
Scheduling to minimize average stretch without migration
SODA '00 Proceedings of the eleventh annual ACM-SIAM symposium on Discrete algorithms
An overview of the Rialto real-time architecture
EW 7 Proceedings of the 7th workshop on ACM SIGOPS European workshop: Systems support for worldwide applications
Approximating an Interval Scheduling Problem
APPROX '98 Proceedings of the International Workshop on Approximation Algorithms for Combinatorial Optimization
Integrated Processors Scheduling for Multimedia
NOSSDAV '95 Proceedings of the 5th International Workshop on Network and Operating System Support for Digital Audio and Video
Online Scheduling to Minimize Average Stretch
FOCS '99 Proceedings of the 40th Annual Symposium on Foundations of Computer Science
Realizing a Soft Real-Time Framework for Supporting Distributed Multimedia Applications
FTDCS '95 Proceedings of the 5th IEEE Workshop on Future Trends of Distributed Computing Systems
On-Line Deadline Scheduling on Multiple Resources
COCOON '01 Proceedings of the 7th Annual International Conference on Computing and Combinatorics
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In this paper, we derive bounds on performance guarantees of online algorithms for real-time preemptive scheduling of jobs with deadlines on K machines when jobs are characterized in terms of their minimum stretch factor α (or, equivalently, their maximum execution rate r = 1/α). We consider two well known preemptive models that are of interest from practical applications: the hard real-time scheduling model in which a job must be completed if it was admitted for execution by the online scheduler, and the firm real-time scheduling model in which the scheduler is allowed not to complete a job even if it was admitted for execution by the online scheduler. In both models, the objective is to maximize the sum of execution times of the jobs that were executed to completion, preemption is allowed, and the online scheduler must immediately decide, whenever a job arrives, whether to admit it for execution or reject it. We measure the competitive ratio of any online algorithm as the ratio of the value of the objective function obtained by this algorithm to that of the best possible offline algorithm. We show that no online algorithm can have a competitive ratio greater than 1-(1/α)+Ɛ for hard real-time scheduling with K ≥ 1 machines and greater than 1 - (3/(4⌈α⌉)) + Ɛ for firm real-time scheduling on a single machine, where Ɛ 0 may be arbitrarily small, even if the algorithm is allowed to know the value of α in advance. On the other hand, we exhibit a simple online scheduler that achieves a competitive ratio of at least 1-(1/α) in either of these models with K machines. The performance guarantee of our simple scheduler shows that it is in fact an optimal scheduler for hard real-time scheduling with K machines. We also describe an alternative scheduler for firm real-time scheduling on a single machine in which the competitive ratio does not go to zero as a approaches 1. Both of our schedulers do not know the value of α in advance.