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Issue No.06 - June (2013 vol.62)
pp: 1255-1268
Jianjun Li , Huazhong University of Science and Technology, Wuhan
Ming Xiong , Google Inc., New York
Victor C.S. Lee , City University of Hong Kong, Hong Kong
LihChyun Shu , National Cheng Kung University, Taiwan
Guohui Li , Huazhong University of Science and Technology, Wuhan
Deriving deadlines and periods for update transactions so as to maintain timeliness and data freshness while minimizing imposed workload has long been recognized an important problem in real-time database research. Despite years of active research, the state-of-the-art still has much room for improvement, particularly for periodic transactions scheduled by the Earliest Deadline First (EDF) algorithm. In this paper, we propose a practical and efficient two-phase algorithm, GEneral EDF ($({\cal G}{\cal E}_{EDF})$), for assigning periods and deadlines to EDF-scheduled update transactions. Phase 1 of $({\cal G}{\cal E}_{EDF})$ aims at finding solutions for most inputs in linear time, based on the observation that the execution times of update transactions are relatively small compared to the validity interval lengths of real-time data objects in many real-time applications. In the remaining cases for which Phase 1 fails to derive solutions, Phase 2 is invoked by employing an existing deadline-monotonic-based algorithm, which we show is also applicable to our problem. Meanwhile, we have devised several techniques which significantly reduce the cost of schedulability test, and hence greatly improve time efficiency. Our experimental results demonstrate that $({\cal G}{\cal E}_{EDF})$ outperforms existing approaches in terms of generated workloads. Although Phase 2 has a pseudopolynomial time complexity, our experimental study shows that it runs much faster than other solutions with comparable quality.
Real time systems, Delta modulation, Complexity theory, Databases, Electronic mail, Educational institutions, Engines, earliest deadline first, Real-time databases, temporal consistency, update transaction, periods and deadlines
Jianjun Li, Ming Xiong, Victor C.S. Lee, LihChyun Shu, Guohui Li, "Workload-Efficient Deadline and Period Assignment for Maintaining Temporal Consistency under EDF", IEEE Transactions on Computers, vol.62, no. 6, pp. 1255-1268, June 2013, doi:10.1109/TC.2012.69
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