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Towards a Tractable Exact Test for Global Multiprocessor fixed priority scheduling

IEEE TRANSACTIONS ON COMPUTERS 2022年第11期71卷 2955-2967页

作者： Burmyakov, Artem Bini, Enrico Lee, Chang-Gun Innopolis Univ Innopolis 420500 Russia Univ Turin I-10124 Turin Italy Seoul Natl Univ Seoul 08826 South Korea

scheduling algorithms are called "global" if they can migrate tasks between cores. Global scheduling algorithms are the de-facto standard practice for general purpose Operating Systems, to balance the workload between cores. However, the exact schedulability analysis of real-time applications for these algorithms is proven to be weakly NP-hard. Despite such a hardness, the research community keeps investigating the methods for an exact schedulability analysis for its relevance and to tightly estimate the execution requirements of real-time systems. Due to the NP-hardness, the available exact tests are very time and memory demanding even for sets of a few tasks. On another hand, the available sufficient tests are very pessimistic, despite consuming less resources. Motivated by these observations, we propose an exact schedulability test for constrained-deadline sporadic tasks under global multiprocessor fixed-priority scheduling scheduler, which is significantly faster and consumes less memory, compared to any other available exact test. To derive a faster test, we exploit the idea of a state-space pruning, aiming at reducing the number of feasible system states to be examined by the test. The resulted test is multiple orders of magnitude faster with respect to other state-of-the-art exact tests. Our C++ implementation is publicly available.

关键词： Task analysis Processor scheduling Program processors Memory management Real-time systems scheduling Sun Real-time systems multiprocessor scheduling exact schedulability test fixed-priority scheduling

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Improved Schedulability Analysis Using Carry-In Limitation for Non-Preemptive fixed-priority Multiprocessor scheduling

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IEEE TRANSACTIONS ON COMPUTERS 2017年第10期66卷 1816-1823页

作者： Lee, Jinkyu Sungkyunkwan Univ SKKU Dept Comp Sci & Engn Suwon 16419 Gyeonggi Do South Korea

A time instant is said to be a critical instant for a task, if the task's arrival at the instant makes the duration between the task's arrival and completion the longest. Critical instants for a task, once revealed, make it possible to check the task's schedulability by investigating situations associated with the critical instants. This potentially results in efficient and tight schedulability tests, which is important in real-time systems. For example, existing studies have discovered critical instants under preemptive fixed-priority scheduling (P-FP), which limit interference from carry-in jobs, yielding the state-of-the-art schedulability tests on both uniprocessor and multiprocessor platforms. However, studies on schedulability tests associated with critical instants have not matured yet for non-preemptive scheduling, especially on a multiprocessor platform. In this paper, we find necessary conditions for critical instants for non-preemptive global fixed-priority scheduling (NP-FP) on a multiprocessor platform, and develop a new schedulability test that takes advantage of the finding for reducing carry-in jobs' interference. Evaluation results show that the proposed schedulability test finds up to 14.3 percent additional task sets schedulable by NP-FP, which are not deemed schedulable by the state-of-the-art NP-FP schedulability test.

关键词： Real-time scheduling critical instants non-preemptive scheduling fixed-priority scheduling multiprocessor platform

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

Towards best-case response times of real-time tasks under fi...

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IEEE International Conference on Emerging Technologies and Factory Automation

作者： Hector J. Rivera-Verduzco Reinder J. Bril Technische Universiteit Eindhoven (TU/e) Eindhoven The Netherlands

fixed-priority scheduling with preemption thresholds (FPTS) is supported by the AUTOSAR and OSEK standards as a scheduling policy. Since FPTS is a generalization of fixed-priority preemptive scheduling (FPPS) and fixed-priority non-preemptive scheduling (FPNS), it aims to improve schedulability. In this paper, we prove, as an intermediate step towards the exact best-case response time analysis for FPTS, that the best-case computation time of a non-preemptive task scheduled under FPTS or FPNS is a tight lower bound for its response time. In addition, we illustrate by means of an example that the best-case response time analysis for FPTS is most likely not a straight forward extension of the current best-case analysis for FPPS.

关键词： real-time tasks fixed-priority scheduling preemption thresholds

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fixed-priority global scheduling for mixed-criticality real-time systems

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INTERNATIONAL JOURNAL OF EMBEDDED SYSTEMS 2014年第2-3期6卷 266-276页

作者： Kelly, Owen R. Aydin, Hakan George Mason Univ Dept Comp Sci Fairfax VA 22030 USA

There has been a growing interest in recent years in mixed-criticality real-time systems in which tasks are attributed different levels of criticality based on the degree to which their deadlines must be assured. While most of the initial efforts on mixed-criticality systems targeted single-processor systems, the research community has recently started to investigate multiprocessor mixed-criticality real-time systems. In this paper we investigate how global, fixed-priority algorithms can be applied in the context of multiprocessor mixed-criticality systems. We identify the two key dimensions of the problem - priority assignment and schedulability testing, and consider candidate algorithms for each dimension. We also propose a new and simple priority assignment policy called CPRatio that considers both task criticality and timing constraints to improve the schedulability of mixed-criticality task sets. We experimentally evaluate the performance of priority assignment strategies and schedulability tests in the global multiprocessor mixed-criticality scheduling context.

关键词： mixed-criticality real-time scheduling global scheduling fixed-priority scheduling multiprocessor scheduling schedulability tests

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Analysis of cache-related preemption delay in fixed-priority preemptive scheduling

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IEEE TRANSACTIONS ON COMPUTERS 1998年第6期47卷 700-713页

作者： Lee, CG Hahn, J Seo, YM Min, SL Ha, R Hong, S Park, CY Lee, M Kim, CS Seoul Natl Univ Dept Comp Engn Seoul 151742 South Korea Seoul Natl Univ Sch Elect Engn Seoul 151742 South Korea Hongik Univ Dept Comp Engn Seoul 121791 South Korea Chung Ang Univ Dept Comp Engn Seoul 156756 South Korea Han Sung Univ Dept Comp Engn Seoul 136792 South Korea

We propose a technique for analyzing cache-related preemption delays of tasks that cause unpredictable variation in task execution time in the context of fixed-priority preemptive scheduling. The proposed technique consists of two steps. The first step performs a per-task analysis to estimate cache-related preemption cost for each execution point in a given task. The second step computes the worst case response time of each task that includes the cache-related preemption delay using a response time equation and a linear programming technique. This step takes as its input the preemption cost information of tasks obtained in the first step. This paper also compares the proposed approach with previous approaches. The results show that the proposed approach gives a prediction of the worst case cache-related preemption delay that is up to 60 percent tighter than those obtained from the previous approaches.

关键词： real-time system fixed-priority scheduling cache memory preemption schedulability analysis

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Integrating Cache-Related Pre-emption Delays into Analysis of fixed priority scheduling with Pre-emption Thresholds 35

Integrating Cache-Related Pre-emption Delays into Analysis o...

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35th IEEE Real-Time Systems Symposium (RTSS)

作者： Brin, Reinder J. Altmeyer, Sebastian van den Heuvel, Martijn M. H. P. Davis, Robert, I Behnam, Moris Malardalen Univ MDH Vasteras Sweden Tech Univ Eindhoven TU E Eindhoven Netherlands Univ Amsterdam Amsterdam Netherlands Univ York York N Yorkshire England

ISBN: (纸本)9781479972876

Cache-related pre-emption delays (CRPD) have been integrated into the schedulability analysis of sporadic tasks with constrained deadlines for fixed-priority pre-emptive scheduling (FPPS). This paper generalizes that work by integrating CRPD into the schedulability analysis of tasks with arbitrary deadlines for fixed-priority pre-emption threshold scheduling (FPTS). The analysis is complemented by an optimal threshold assignment algorithm that minimizes CRPD. The paper includes a comparative evaluation of the schedulability ratios of FPPS and FPTS, for constrained-deadline tasks, taking CRPD into account.

关键词： cache-related pre-emption delay CRPD fixed-priority scheduling pre-emption thresholds

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Efficient Optimal priority Assignment for fixed priority Preemption Threshold scheduling

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JOURNAL OF INFORMATION SCIENCE AND ENGINEERING 2018年第2期34卷 319-335页

作者： Kim, Saehwa Hankuk Univ Foreign Studies Dept Informat Commun Engn Gyeonggi Do 449791 South Korea

This paper proposes an efficient priority assignment algorithm for fixed priority preemption threshold scheduling (PTS), which we named FAST-TRAVERSE. It is optimal in the sense that it always finds a feasible priority assignment if one exists. While there are existing optimal algorithms, they are inefficient to be used in practice. The key ideas of FAST-TRAVERSE are to prune sibling traverses and preemption threshold assignments if possible based on the notion of the effective blocking task. The empirical evaluation results clearly show that FAST-TRAVERSE achieves the largest feasibility and can be employed as an on-line priority assignment algorithm for PTS.

关键词： real-time systems and embedded systems system integration and implementation real-time feasibility scalability fixed-priority scheduling

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On Energy-Optimal Voltage scheduling for fixed-priority Hard Real-Time Systems

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ACM Transactions on Embedded Computing Systems 2003年第3期2卷 393-430页

作者： Yun, Han-Saem Kim, Jihong School of Computer Science and Engineering Seoul National University Seoul Shilim-dong Kwanak-ku 151-742 South Korea

We address the problem of energy-optimal voltage scheduling for fixed-priority hard real-time systems, on which we present a complete treatment both theoretically and practically. Although most practical real-time systems are based on fixed-priority scheduling, there have been few research results known on the energy-optimal fixed-priority scheduling problem. First, we prove that the problem is NP-hard. Then, we present a fully polynomial time approximation scheme (FPTAS) for the problem. For any ɛ>0, the proposed approximation scheme computes a voltage schedule whose energy consumption is at most (1+ɛ) times that of the optimal voltage schedule. Furthermore, the running time of the proposed approximation scheme is bounded by a polynomial function of the number of input jobs and 1/ɛ. Given the NP-hardness of the problem, the proposed approximation scheme is practically the best solution because it can compute a near-optimal voltage schedule (i.e., provably arbitrarily close to the optimal schedule) in polynomial time. Experimental results show that the approximation scheme finds more efficient (almost optimal) voltage schedules faster than the best existing heuristic. © 2003, ACM. All rights reserved.

关键词： Algorithms approximation algorithms dynamic voltage scaling fixed-priority scheduling fully polynomial time approximation scheme real-time systems variable voltage processor

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On Partitioned scheduling of fixed-priority Mixed-Criticality Task Sets

On Partitioned Scheduling of Fixed-Priority Mixed-Criticalit...

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Int Joint Conference of 10th IEEE Int Conf on Trust, Security and Privacy in Computing and Communications (TrustCom) / 8th IEEE Int Conf on Embedded Software and Systems (ICESS) / 6th Int Conf on Frontier of Computer Science and Technology (FCST)

作者： Kelly, Owen R. Aydin, Hakan Zhao, Baoxian George Mason Univ Dept Comp Sci Fairfax VA 22030 USA

ISBN: (纸本)9780769546001

Mixed-criticality real-time systems, where tasks may be associated with different criticality and assurance levels, have attracted much attention in the recent past. In this paper, we consider partitioning-based multiprocessor scheduling of mixed-criticality real-time task sets. Guaranteeing feasibility in this setting is shown to be NP-Hard. With a focus on fixed-priority preemptive scheduling on each processor, we identify the two main aspects of the problem, namely the task allocation and priority assignment dimensions. For the task allocation dimension, we propose and compare bin-packing-inspired heuristics, based on offline task ordering according to utilization and criticality. For the priority assignment dimension, we compare the wellknown Rate Monotonic priority assignment policy with Audsley's priority assignment algorithm. Through simulations, we also assess and discuss the relative importance of these two primary dimensions on the overall mixed-criticality feasibility problem for multiprocessor platforms.

关键词： real-time scheduling multiprocessor systems mixed-criticality partitioning-based scheduling fixed-priority scheduling

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Hybrid-priority real-time scheduling

Hybrid-priority real-time scheduling

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10th Workshop on Advances in Parallel and Distributed Computational Models/22nd IEEE International Parallel and Distributed Processing Symposium

作者： Baruah, Sanjoy Fisher, Nathan Univ N Carolina Chapel Hill NC 27515 USA Wayne State Univ Detroit MI 48202 USA

ISBN: (纸本)9781424416936

A hybrid scheduling algorithm is proposed, which integrates features of the fixed priority (FP) and Earliest Deadline First (EDF) scheduling policies. It is shown that this hybrid scheduling algorithm is a generalization of both FP and EDF, and tends to retain most of the desirable properties and features of both individual policies. Two exact (i.e., necessary and sufficient) tests are derived for sporadic task systems scheduled by the hybrid scheduling algorithm.

关键词： earliest-deadline first fixed-priority scheduling hybrid scheduling schedulability analysis sporadic tasks

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