Abstract
Utilization-based admission control policies for processors executing aperiodic tasks are often favored due to their low overhead. This paper investigates utilization-based admission control for uniprocessor systems executing aperiodic tasks following the earliest deadline first priority assignment. We first propose a new constant time utilization-based admission control policy, CTAC. We prove that CTAC is safe and will admit any task instance that can be admitted by the best existing utilization-based admission control policy, ASL, given the same processor state. We also introduce an optimal utilization-based admission control policy, OPAC. It is proved that given the same processor state, a newly arriving task instance that can be admitted by any other safe utilization-based admission control policy can also be admitted by OPAC. We also show that OPAC cannot be implemented in constant time. Simulation results show that CTAC indeed outperforms ASL with constant time complexity and achieves performance close to OPAC in terms of various metrics.
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Notes
A related task model, acyclic task model, is introduced in Abdelzaher et al. (2004) and shown to be equivalent to the aperiodic task model when considering schedulability. Since any admission control policy for aperiodic tasks can also be applied to acyclic tasks and the aperiodic task model is better known, we use the aperiodic task model.
Unless explicitly stated, optimality always refers to optimality in the sense of maximum admission capability.
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Acknowledgments
This work is supported by the National Key Basic Research Program of China (973 Program, Grant No. 2013CB 329305), National Science Foundation of China (Grant No. 61232013), Institute of Software, Chinese Academy of Sciences (Grant No. ISCAS2009-JQ03) and National Key Technology R&D program (Grant No. 2013AA040701). The work of Hu is supported in part by U.S. NSF under grant number CNS-1319904.
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Leng, C., Qiao, Y., Hu, X.S. et al. Utilization-based admission control for aperiodic tasks under EDF scheduling. Real-Time Syst 51, 36–76 (2015). https://doi.org/10.1007/s11241-014-9216-6
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DOI: https://doi.org/10.1007/s11241-014-9216-6