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Issue No. 04 - April (2014 vol. 63)
ISSN: 0018-9340
pp: 979-994
Song Han , Dept. of Comput. Sci. & Eng., Univ. of Connecticut, Storrs, CT, USA
Deji Chen , Emerson Process Manage., Round Rock, TX, USA
Ming Xiong , Google, Inc., New York, NY, USA
Kam-Yiu Lam , Dept. of Comput. Sci., City Univ. of Hong Kong, Kowloon, China
Aloysius K. Mok , Dept. of Comput. Sci., Univ. of Texas at Austin, Austin, TX, USA
Krithi Ramamritham , Dept. of Comput. Sci. & Eng., Indian Inst. of Technol., Mumbai, Mumbai, India
Although the deferrable scheduling algorithm for fixed priority transactions ( DS-FP) has been shown to provide a better performance compared with the More-Less (ML) method, there is still a lack of any comprehensive studies on the necessary and sufficient conditions for the schedulability of DS-FP. In this paper, we first analyze the necessary and sufficient schedulability conditions for DS-FP, and then propose a schedulability test algorithm for DS-FP by exploiting the fact that there always exists a repeating pattern in a DS-FP schedule. To resolve the limitation of fixed priority scheduling in DS-FP, we then extend the deferrable scheduling to a dynamic priority scheduling algorithm called DS-EDF by applying the earliest deadline first (EDF) policy to schedule update jobs. We also propose a schedulability test for DS-EDF and compare its performance with DS-FP and ML through extensive simulation experiments. The results show that the schedulability tests are effective. Although the schedulability of DS-EDF is lower than DS-FP and the repeating patterns in DS-EDF schedules are longer than those in DS-FP due to the use of dynamic priority scheduling, the performance of DS-EDF is better than both DS-FP and ML in terms of CPU utilization and impact on lower priority application transactions.
Schedules, Real-time systems, Dynamic scheduling, Scheduling algorithms, Discrete time systems

Song Han, Deji Chen, Ming Xiong, Kam-Yiu Lam, A. K. Mok and K. Ramamritham, "Schedulability Analysis of DeferrableScheduling Algorithms for MaintainingReal-Time Data Freshness," in IEEE Transactions on Computers, vol. 63, no. 4, pp. 979-994, 2014.
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