Exact response-time analysis for fixed-priority preemption-threshold scheduling

Keskin, Ugur; Bril, Reinder J.; Lukkien, Johan J.

doi:10.1109/etfa.2010.5640984

Cited by 32 publications

(36 citation statements)

References 3 publications

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“…A preemption will take place only if the preempting task has a nominal priority greater than the preemption threshold of the executing task. An exact schedulability analysis for FP with preemption thresholds has been presented in [22] 1 . Although the number of preemptions is reduced with this method, a preemption can still occur at any time and position, so that timing analysis techniques cannot take advantage of additional information to simplify the estimation of the WCETs.…”

Section: Related Workmentioning

confidence: 99%

Optimal Selection of Preemption Points to Minimize Preemption Overhead

Bertogna

Xhani

Marinoni

et al. 2011

2011 23rd Euromicro Conference on Real-Time Systems

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Abstract-A central issue for verifying the schedulability of hard realtime systems is the correct evaluation of task execution times. These values are significantly influenced by the preemption overhead, which mainly includes the cache related delays and the context switch times introduced by each preemption. Since such an overhead significantly depends on the particular point in the code where preemption takes place, this paper proposes a method for placing suitable preemption points in each task in order to maximize the chances of finding a schedulable solution.In a previous work, we presented a method for the optimal selection of preemption points under the restrictive assumption of a fixed preemption cost, identical for each preemption point. In this paper, we remove such an assumption, exploring a more realistic and complex scenario where the preemption cost varies throughout the task code. Instead of modeling the problem with an integer programming formulation, with exponential worst-case complexity, we derive an optimal algorithm that has a linear time and space complexity. This somewhat surprising result allows selecting the best preemption points even in complex scenarios with a large number of potential preemption locations. Experimental results are also presented to show the effectiveness of the proposed approach in increasing the system schedulability.

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Section: Related Workmentioning

confidence: 99%

Optimal Selection of Preemption Points to Minimize Preemption Overhead

Bertogna

Xhani

Marinoni

et al. 2011

2011 23rd Euromicro Conference on Real-Time Systems

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“…This section starts with a recapitulation of the exact schedulability analysis for FPTS, as presented in Keskin et al (2010). Next, that analysis is specialized for FPPS with constrained deadlines, i.e.…”

Section: Recap Of Response Time Analysis For Fpps and Fptsmentioning

confidence: 99%

“…In particular, fixed-priority scheduling with deferred pre-emption (FPDS) (Burns 1994;Bril et al 2009;Davis and Bertogna 2012), also called cooperative scheduling, and fixed-priority scheduling with pre-emption thresholds (FPTS) (Wang and Saksena 1999;Saksena and Wang 2000;Regehr 2002;Keskin et al 2010) are considered viable alternatives between the extremes of fully pre-emptive and non-pre-emptive scheduling. Compared to fully pre-emptive scheduling, limited preemptive schemes can (i) reduce memory requirements (Saksena and Wang 2000;Gai et al 2001;Davis et al 2000) and (ii) reduce the cost of arbitrary pre-emptions (Burns 1994;Bril et al 2009;Bertogna et al 2011b).…”

Section: Limited Pre-emptive Schedulingmentioning

confidence: 99%

Fixed priority scheduling with pre-emption thresholds and cache-related pre-emption delays: integrated analysis and evaluation

et al. 2017

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Commercial off-the-shelf programmable platforms for real-time systems typically contain a cache to bridge the gap between the processor speed and main memory speed. Because cache-related pre-emption delays (CRPD) can have a significant influence on the computation times of tasks, CRPD have been integrated in the response time analysis for fixed-priority pre-emptive scheduling (FPPS). This paper presents CRPD aware response-time analysis of sporadic tasks with arbitrary deadlines for fixed-priority pre-emption threshold scheduling (FPTS), generalizing earlier work. The analysis is complemented by an optimal (pre-emption) threshold assignment algorithm, assuming the priorities of tasks are given. We further improve upon these results by presenting an algorithm that searches for a layout of tasks in memory that makes a task set schedulable. The paper includes an extensive comparative evaluation of the schedulability ratios of FPPS and FPTS, taking CRPD into account. The practical relevance of our work stems from FPTS support in AUTOSAR, a standardized development model for the automotive industry. Keywords Fixed-priority pre-emptive scheduling · Fixed-priority scheduling with pre-emption thresholds · Cache-related pre-emption delay · Response-time analysis B Reinder J. Bril

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“…In this section, we recapitulate on the exact worst-case response time analysis for FPTS given in [10]. Similar to FPPS, in order to determine the worst-case response time of a task τ i using FPTS scheduling, it is necessary to consider all the jobs that occur in the level-i active period after a critical instant.…”

Section: Worst-case Response Time Analysis For Fptsmentioning

confidence: 99%

Best-case response times of real-time tasks under fixed-priority scheduling with preemption thresholds

Rivera-Verduzco

Bril

2017

Proceedings of the 25th International Conference on Real-Time Networks and Systems

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DisclaimerThis document contains a student thesis (bachelor's or master's), as authored by a student at Eindhoven University of Technology. Student theses are made available in the TU/e repository upon obtaining the required degree. The grade received is not published on the document as presented in the repository. The required complexity or quality of research of student theses may vary by program, and the required minimum study period may vary in duration. General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain AbstractNowadays, real-time systems are found in a wide range of applications, from small consumer electronic devices to large critical application in the area of robotics, aeronautics, automotive, etc. The main purpose of a real-time system is to provide a correct response within certain time bounds. Therefore, it is imperative to determine bounds on the response time of real-time tasks to guarantee that they meet the timing constraints imposed by the system.Since in a processor normally a set of tasks execute concurrently, the order in which the tasks are scheduled has an impact on the response time of real-time tasks. There exists many scheduling approaches to determine the order in which tasks execute on a processor. One of the most well known is fixed-priority preemptive scheduling (FPPS) that is supported by most real-time operating systems. However, fixed-priority scheduling with preemption thresholds (FPTS) has been viewed as a potential successor to FPPS as a de facto standard in industry, where it is already supported by both OSEK and AUTOSAR compliant operating systems. Compared to FPPS, FPTS reduces memory requirements, the cost of arbitrary preemptions, and it has been shown to improve the ratio of the task-sets that can meet their upper timing constraints.In this thesis, we present and prove a novel exact best-case response time analysis for independent real-time periodic tasks scheduled using FPTS. As an initial step towards the best-case analysis for FPTS, we first prove that the best-case response time of non-preemptive tasks is equal to their best-case computation times. Next, we formalize the exact analysis based on facts derived from experimentation related with the best-case behaviour of a task scheduled using FPTS.Unlike FPPS, the exact analysis for FPTS that we propose has exponential time complexity. Therefore, we also propose and prove a novel lower bound for the best-case response time of a task that provides a tractable schedulability test for tasks. In addition, we present an evaluation of our exact analysis for FPT...

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Exact response-time analysis for fixed-priority preemption-threshold scheduling

Cited by 32 publications

References 3 publications

Optimal Selection of Preemption Points to Minimize Preemption Overhead

Optimal Selection of Preemption Points to Minimize Preemption Overhead

Fixed priority scheduling with pre-emption thresholds and cache-related pre-emption delays: integrated analysis and evaluation

Best-case response times of real-time tasks under fixed-priority scheduling with preemption thresholds

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