Schedulability and optimization analysis for non-preemptive static priority scheduling based on task utilization and blocking factors

Brüggen, Georg von der; Chen, Jian-Jia; Huang, Wen-Hung

doi:10.1109/ecrts.2015.16

Cited by 17 publications

(17 citation statements)

References 15 publications

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“…These bounds are S = 1/Ω and S = 2 respectively for all three classes of task set (implicit, constrained and arbitrary deadline). von der Bruggen et al (2015) proved upper bounds of S = 1/Ω for the implicit and constrained deadline cases, thus along with the prior results, showing that these values are exact. Davis et al (2015a) also completed the exact characterization of the speedup factors required to guarantee schedulability under FP-NP of all EDF-NP feasible task sets by showing that the exact speedup factor for the arbitrary deadline case is S = 2 (the same as in the preemptive case for FP-P v. EDF-P).…”

Section: Introductionsupporting

confidence: 53%

Exact speedup factors and sub-optimality for non-preemptive scheduling

et al. 2017

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Fixed priority scheduling is used in many real-time systems; however, both preemptive and non-preemptive variants (FP-P and FP-NP) are known to be sub-optimal when compared to an optimal uniprocessor scheduling algorithm such as preemptive earliest deadline first (EDF-P). In this paper, we investigate the suboptimality of fixed priority non-preemptive scheduling. Specifically, we derive the exact processor speed-up factor required to guarantee the feasibility under FP-NP (i.e.Preliminary publication: This paper extends initial research into speedup factors for preemptive versus non-preemptive uniprocessor scheduling published in RTSS 2015 (Davis et al. 2015c). The main extension is the proof of the exact speedup factor required to guarantee the FP-P feasibility of any FP-NP feasible constrained-deadline task set. Real-Time Syst (2018) 54:208-246 209 schedulability assuming an optimal priority assignment) of any task set that is feasible under EDF-P. As a consequence of this work, we also derive a lower bound on the sub-optimality of non-preemptive EDF (EDF-NP). As this lower bound matches a recently published upper bound for the same quantity, it closes the exact sub-optimality for EDF-NP. It is known that neither preemptive, nor non-preemptive fixed priority scheduling dominates the other, in other words, there are task sets that are feasible on a processor of unit speed under FP-P that are not feasible under FP-NP and viceversa. Hence comparing these two algorithms, there are non-trivial speedup factors in both directions. We derive the exact speed-up factor required to guarantee the FP-NP feasibility of any FP-P feasible task set. Further, we derive the exact speed-up factor required to guarantee FP-P feasibility of any constrained-deadline FP-NP feasible task set.

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Section: Introductionsupporting

confidence: 53%

Exact speedup factors and sub-optimality for non-preemptive scheduling

et al. 2017

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“…As this article was going to press, further work on speedup factors for the case of FP-NP v. EDF-NP with implicit and constrained deadlines was published by von der Brüggen et al (2015). They tightened the upper bounds in these cases from 2 to   / 1 1.76322.…”

Section: Proofmentioning

confidence: 99%

Exact comparison of fixed priority and EDF scheduling based on speedup factors for both pre-emptive and non-pre-emptive paradigms

et al. 2015

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“…These bounds are S = 1/Ω and S = 2 respectively for all three classes of task set (implicit, constrained and arbitrary deadline). In 2015, von der Brüggen et al [38] proved upper bounds of S = 1/Ω for the implicit and constrained deadline cases, thus along with the prior results, showing that these values are exact. Later in 2015, Davis et al [15] also completed the exact characterization of the speedup factors required to guarantee FP-NP feasibility of EDF-NP feasible task sets by showing that the exact speedup factor for the arbitrary deadline case is S = 2 (the same as in the preemptive case for FP-P v. EDF-P).…”

Section: A Speedup Factorsmentioning

confidence: 80%

Quantifying the Exact Sub-optimality of Non-preemptive Scheduling

Davis¹,

Thekkilakattil²,

Gettings³

et al. 2015

2015 IEEE Real-Time Systems Symposium

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Abstract-Fixed priority scheduling is used in many real-time systems; however, both preemptive and non-preemptive variants (FP-P and FP-NP) are known to be sub-optimal when compared to an optimal uniprocessor scheduling algorithm such as preemptive Earliest Deadline First (EDF-P). In this paper, we investigate the sub-optimality of fixed priority non-preemptive scheduling. Specifically, we derive the exact processor speed-up factor required to guarantee the feasibility under FP-NP (i.e. schedulablability assuming an optimal priority assignment) of any task set that is feasible under EDF-P. As a consequence of this work, we also derive a lower bound on the sub-optimality of non-preemptive EDF (EDF-NP), which since it matches a recently published upper bound gives the exact sub-optimality for EDF-NP.It is known that neither preemptive, nor non-preemptive fixed priority scheduling dominates the other, i.e., there are task sets that are feasible on a processor of unit speed under FP-P that are not feasible under FP-NP and vice-versa. Hence comparing these two algorithms, there are non-trivial speedup factors in both directions. We derive the exact speed-up factor required to guarantee the FP-NP feasibility of any FP-P feasible task set. Further, we derive upper and lower bounds on the speed-up factor required to guarantee FP-P feasibility of any FP-NP feasible task set. Empirical evidence suggests that the lower bound may be tight, and hence equate to the exact speed-up factor in this case.

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Schedulability and optimization analysis for non-preemptive static priority scheduling based on task utilization and blocking factors

Cited by 17 publications

References 15 publications

Exact speedup factors and sub-optimality for non-preemptive scheduling

Exact speedup factors and sub-optimality for non-preemptive scheduling

Exact comparison of fixed priority and EDF scheduling based on speedup factors for both pre-emptive and non-pre-emptive paradigms

Quantifying the Exact Sub-optimality of Non-preemptive Scheduling

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