Abstract
Cache-Related Preemption Delays (CRPD) can significantly increase tasks’ execution time in preemptive real-time scheduling, potentially jeopardising the system schedulability. In order to reduce the cumulative CRPD, Limited Preemptive Scheduling (LPS) has emerged as a scheduling approach which limits the maximum number of preemptions encountered by real-time tasks, thus decreasing CRPD compared to fully preemptive scheduling. Furthermore, an instance of LPS, called Fixed Preemption Point Scheduling (LP-FPP), defines the exact points where the preemptions are permitted within a task, which enables a more precise CRPD estimation. The majority of the research, in the domain of LP-FPP, estimates CRPD with pessimistic upper bounds, without considering the possible sources of over-approximation: (1) accounting for the infeasible preemption combinations, and (2) accounting for the infeasible cache block reloads. In this paper, we improve the analysis by accounting for those two cases towards a more precise estimation of the CRPD upper bounds. The evaluation of the approach on synthetic tasksets reveals a significant reduction of the pessimism in the calculation of the CRPD upper bounds, compared to the existing approaches.
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Notes
- 1.
In the original definition, Altmeyer used must to eliminate the cases where the useful cache block eviction is accounted by both: WCET and CRPD analysis, while it should be accounted only by the CRPD analysis. However, a useful cache block still may be cached, but its eviction will not be accounted by both analysis.
- 2.
Refers only to self-eviction by \(\tau _i\).
- 3.
We extracted a few of the most time-consuming (more than 40 s) cases from the evaluation, and with IBM CPLEX [14] they were solved in less than 200 ms.
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Marković, F., Carlson, J., Dobrin, R. (2018). Improved Cache-Related Preemption Delay Estimation for Fixed Preemption Point Scheduling. In: Casimiro, A., Ferreira, P. (eds) Reliable Software Technologies – Ada-Europe 2018. Ada-Europe 2018. Lecture Notes in Computer Science(), vol 10873. Springer, Cham. https://doi.org/10.1007/978-3-319-92432-8_6
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