Energy-Aware Task Scheduling for Real-Time Systems with Discrete Frequencies

Dejun QIAN  Zhe ZHANG  Chen HU  Xincun JI  

IEICE TRANSACTIONS on Information and Systems   Vol.E94-D   No.4   pp.822-832
Publication Date: 2011/04/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E94.D.822
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Software System
real-time system,  low power design,  dynamic voltage scaling,  stochastic speed scheduling,  

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Power-aware scheduling of periodic tasks in real-time systems has been extensively studied to save energy while still meeting the performance requirement. Many previous studies use the probability information of tasks' execution cycles to assist the scheduling. However, most of these approaches adopt heuristic algorithms to cope with realistic CPU models with discrete frequencies and cannot achieve the globally optimal solution. Sometimes they even show worse results than non-stochastic DVS schemes. This paper presents an optimal DVS scheme for frame-based real-time systems under realistic power models in which the processor provides only a limited number of speeds and no assumption is made on power/frequency relation. A suboptimal DVS scheme is also presented in this paper to work out a solution near enough to the optimal one with only polynomial time expense. Experiment results show that the proposed algorithm can save at most 40% more energy compared with previous ones.