DESH: overhead reduction algorithms for deferrable scheduling

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.