Conference: Proceedings of the International Conference on Embedded Systems and Applications, ESA '04 & Proceedings of the International Conference on VLSI, VLSI '04, June 21-24, 2004, Las Vegas, Nevada, USA
"Real-Time Syst in HH, the validity constraints of the corresponding real-time data objects can also be guaranteed. Similarly to HH, More-Less (ML) (Xiong and Ramamritham 2004; Lam et al. 2004; Chen and Mok 2004) is another periodic approach in which update transactions are scheduled based on the deadline monotonic algorithm (Leung and Whitehead 1982). Compared to HH, ML can guarantee the validity of real-time data objects with less update transaction workload. "
[Show abstract][Hide abstract] ABSTRACT: Although the deferrable scheduling algorithm for fixed priority transactions (DS-FP) has been shown to be a very effective approach for minimizing real-time update transaction workload, it suffers from its
on-line scheduling overhead. In this work, we propose two extensions of DS-FP to minimize the on-line scheduling overhead. The proposed algorithms produce a hyperperiod from DS-FP so that the schedule generated by repeating the hyperperiod infinitely satisfies the temporal validity constraint of the
real-time data. The first algorithm, named DEferrable Scheduling with Hyperperiod by Schedule Construction (DESH-SC), searches the DS-FP schedule for a hyperperiod. The second algorithm, named DEferrable Scheduling with Hyperperiod by Schedule Adjustment (DESH-SA), adjusts the DS-FP schedule in an interval to form a hyperperiod. Our experimental results demonstrate that while both DESH-SC and DESH-SA can reduce the scheduling overhead of DS-FP, DESH-SA outperforms DESH-SC by accommodating significantly more update transactions in the system. Moreover, DESH-SA can also achieve near-optimal update workload.
Real-Time Systems 01/2010; 44:1-25. DOI:10.1007/s11241-009-9087-4 · 1.00 Impact Factor
"Most of the work in update transaction scheduling assumes a periodic transaction model. For example, a periodic update transaction model is adopted in the more-less (ML) scheme   . ML can guarantee the validity of real-time data objects. "
[Show abstract][Hide abstract] ABSTRACT: The schedulability testing for the deferrable scheduling algorithm for fixed priority transactions (DS-FP) remainsan open problem since its introduction. In this paper, wetake the first step towards investigating necessary and sufficient conditions for the DS-FP schedulability. We propose a necessary and sufficient schedulability condition for the algorithm in discrete time systems, and prove its correctness. Based on this condition, we propose a schedulability test algorithm that is more accurate than the existing test that is only based on a sufficient condition. Our algorithm exploits the fact that there is always a repeating pattern in a DS-FP schedule in discrete time systems. We demonstrate through examples that our schedulability test algorithm outperforms the existing algorithm in terms of accuracy.
"The deferrable scheduling algorithm is proposed in . ML is studied in   , which reduces update workload compared to the Half-Half approach [17, 12] while guaranteeing the validity constraint. Compared to ML, DS-FP reduces update workload further by adaptively adjusting the separation of two consecutive jobs while satisfying the validity constraint. "
[Show abstract][Hide abstract] ABSTRACT: The deferrable scheduling algorithm for fixed priority transactions (DS-FP) (23) is demonstrated to be a very effective approach for minimizing real-time update trans- action workload while maintaining temporal validity of real-time data. This paper examines the schedulability of deferrable scheduling and presents a sufficient condition. While its on-line scheduling overhead is a concern, we pro- pose a hyperperiod based DS-FP approach satisfying the temporal validity constraint with low overhead. The al- gorithm, namely DEferrable Scheduling with Hyperperiod by Schedule Adjustment (DESH-SA), adjusts the DS-FP schedule in an interval so that the adjusted schedule in the interval can be repeated infinitely. Our experiments demon- strate that DESH-SA can reduce scheduling overhead of DS-FP and also achieve update workload near optimal.
12th IEEE Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2006), 16-18 August 2006, Sydney, Australia; 01/2006
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