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39th IEEE/ACM International Conference On Computer Aided Design (ICCAD)

作者： Dai, Xiaotian Zhao, Shuai Jiang, Yu Jiao, Xun Hu, Xiaobo Sharon Chang, Wanli Univ York York N Yorkshire England Tsinghua Univ Beijing Peoples R China Villanova Univ Villanova PA 19085 USA Univ Notre Dame Notre Dame IN 46556 USA

ISBN: (纸本)9781665423243

Time-sensitive networking (TSN) is a set of standardised communication protocols developed under the IEEE 802.1 working group. TSN aims to support deterministic communication based on network schedules that are distributively configured. It is widely considered as the future in-vehicle network solution for highly automated driving, where the requirement on timing guarantee is alongside the demand of high communication bandwidth. In this work, we study a setting of periodic control and non-control packets, with implicit and arbitrary deadlines, respectively. As the FIFO (first-in, first-out) queues in the 802.1Qbv switch incur long delay in the worst case, which prevents the control tasks from achieving short sampling periods and thus impedes control performance optimisation, we propose the first fixed-priority scheduling (FPS) approach for TSN by leveraging its gate control features. In this context, we develop a finer-grained frame-level response time analysis, which provides a tighter bound than the conventional packet-level analysis. Building upon FPS and the above analysis, we formulate a co-design optimisation problem to decide the sampling periods and poles of real-time controllers with settling time as the objective to minimise, whilst satisfying the schedulability constraint.

关键词： Time-sensitive networks real-time communication fixed-priority scheduling scheduling-controller co-design

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Worst-case response time analysis of real-time tasks under fixed-priority scheduling with deferred preemption

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REAL-TIME SYSTEMS 2009年第1-3期42卷 63-119页

作者： Bril, Reinder J. Lukkien, Johan J. Verhaegh, Wim F. J. Tech Univ Eindhoven Dept Math & Comp Sci NL-5600 AZ Eindhoven Netherlands Philips Res Labs NL-5656 AE Eindhoven Netherlands

fixed-priority scheduling with deferred preemption (FPDS) has been proposed in the literature as a viable alternative to fixed-priority pre-emptive scheduling (FPPS), that obviates the need for non-trivial resource access protocols and reduces the cost of arbitrary preemptions. This paper shows that existing worst-case response time analysis of hard real-time tasks under FPDS, arbitrary phasing and relative deadlines at most equal to periods is pessimistic and/or optimistic. The same problem also arises for fixed-priority non-preemptive scheduling (FPNS), being a special case of FPDS. This paper provides a revised analysis, resolving the problems with the existing approaches. The analysis is based on known concepts of critical instant and busy period for FPPS. To accommodate for our scheduling model for FPDS, we need to slightly modify existing definitions of these concepts. The analysis assumes a continuous scheduling model, which is based on a partitioning of the timeline in a set of non-empty, right semi-open intervals. It is shown that the critical instant, longest busy period, and worst-case response time for a task are suprema rather than maxima for all tasks, except for the lowest priority task. Hence, that instant, period, and response time cannot be assumed for any task, except for the lowest priority task. Moreover, it is shown that the analysis is not uniform for all tasks, i.e. the analysis for the lowest priority tanalysis of the other tasks. These anomalies for the lowest priority task are an immediate consequence of the fact that only the lowest priority task cannot be blocked. To build on earlier work, the worst-case response time analysis for FPDS is expressed in terms of known worst-case analysis results for FPPS. The paper includes pessimistic variants of the analysis, which are uniform for all tasks, illustrates the revised analysis for an advanced model for FPDS, where tasks are structured as flow graphs of subjobs rather than sequences, and sho

关键词： Level-i active period Level-i busy period Worst-case response time Worst-case occupied time Periodic tasks fixed-priority scheduling Deferred preemption Real-time systems

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Preference-oriented fixed-priority scheduling for periodic real-time tasks

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JOURNAL OF SYSTEMS ARCHITECTURE 2016年第0期69卷 1-14页

作者： Begam, Rehana Xia, Qin Zhu, Dakai Aydin, Hakan Univ Texas San Antonio Dept Comp Sci San Antonio TX 78249 USA Xi An Jiao Tong Univ Sch Elect & Informat Engn Xian 710049 Shaanxi Peoples R China George Mason Univ Dept Comp Sci Fairfax VA 22030 USA

Traditionally, real-time scheduling algorithms prioritize tasks solely based on their timing parameters and cannot effectively handle tasks that have different execution preferences. In this paper, for a set of periodic real-time tasks running on a single processor, where some tasks are preferably executed as soon as possible (ASAP) and others as late as possible (ALAP), we investigate Preference-Oriented fixed-priority (POFP) scheduling techniques. First, based on Audsley's Optimal priority Assignment (OPA), we study a Preference priority Assignment (PPA) scheme that attempts to assign ALAP (ASAP) tasks lower (higher) priorities, whenever possible. Then, by considering the non-work-conserving strategy, we exploit the promotion times of ALAP tasks and devise an online dual-queue based POFP scheduling algorithm. Basically, with the objective of fulfilling the execution preferences of all tasks, the POFP scheduler retains ALAP tasks in the delay queue until their promotion times while putting ASAP tasks into the ready queue right after their arrivals. In addition, to further expedite (delay) the executions of ASAP (ALAP) tasks using system slack, runtime techniques based on dummy and wrapper tasks are investigated. The proposed schemes are evaluated through extensive simulations. The results show that, compared to the classical fixed-priority Rate Monotonic scheduling (RMS) algorithm, the proposed priority assignment scheme and POFP scheduler can achieve significant improvement in terms of fulfilling the execution preferences of both ASAP and ALAP tasks, which can be further enhanced at runtime with the wrapper-task based slack management technique. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Real-time systems Periodic tasks fixed-priority scheduling Preference-oriented executions

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The Concept of Unschedulability Core for Optimizing Real-Time Systems with fixed-priority scheduling

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IEEE TRANSACTIONS ON COMPUTERS 2019年第6期68卷 926-938页

作者： Zhao, Yecheng Zeng, Haibo Virginia Tech Dept ECE Blacksburg VA 24060 USA

In the design optimization of real-time systems scheduled with fixed priority, schedulability analysis is used to define the feasibility region within which tasks meet their deadlines, so that optimization algorithms can find the best solution within the region. However, the complexity of schedulability analysis techniques often makes it difficult to leverage existing optimization frameworks and scale to large designs. In this paper, we propose the concept of unschedulability core, a compact representation of the schedulability conditions, and develop efficient algorithms for its calculation. We present a new optimization framework that leverages such a concept. We show that this concept is applicable to a range of optimization problems, for example, when the decision variables include the task priority assignment and the selection of mechanisms protecting shared buffers. Experimental results on two case studies demonstrate that the new optimization procedure maintains the optimality of the solutions, but is a few orders of magnitude faster than other exact algorithms (branch-and-bound, integer linear programming).

关键词： Real-time systems fixed-priority scheduling design optimization audsley's algorithm unschedulability core

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Generalizing fixed-priority scheduling for better schedulability in mixed-criticality systems

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INFORMATION PROCESSING LETTERS 2016年第8期116卷 508-512页

作者： Chen, Yao Shin, Kang G. Xiong, Huagang Beihang Univ Sch Elect & Informat Engn Beijing 100191 Peoples R China Univ Michigan EECS Real Time Comp Lab Ann Arbor MI 48109 USA

The design of mixed-criticality systems is often subject to mandatory certification and has been drawing considerable attention over the past few years, This letter studies fixed-priority scheduling of mixed-criticality systems on a uniprocessor platform but in a more general way, using different priority orderings in different execution phases and considering them collectively. Then a sufficient response-time analysis is developed and a new priority assignment scheme is proposed. This generalized approach has potential in better schedulability performance for mixed-criticality systems. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Real-time systems Mixed-criticality fixed-priority scheduling Schedulability analysis priority assignment algorithm

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ON THE COMPLEXITY OF fixed-priority scheduling OF PERIODIC, REAL-TIME TASKS

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PERFORMANCE EVALUATION 1982年第4期2卷 237-250页

作者： LEUNG, JYT WHITEHEAD, J CUNY QUEENS COLL DEPT COMP SCIFLUSHINGNY 11367

We consider the complexity of determining whether a set of periodic, real-time tasks can be scheduled on m ? 1 identical processors with respect to fixed-priority scheduling. It is shown that the problem is NP-hard in... 详细信息

关键词： Periodic Real-time Task fixed-priority scheduling Optimal scheduling Algorithms Multiprocessors System NP-completeness

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Optimal utilization bounds for the fixed-priority scheduling of periodic task systems on identical multiprocessors

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IEEE TRANSACTIONS ON COMPUTERS 2004年第6期53卷 781-784页

作者： Baruah, SK Univ N Carolina Dept Comp Sci Chapel Hill NC 27599 USA

In fixed-priority scheduling, the priority of a job, once assigned, may not change. A new fixed-priority algorthm for scheduling systems of periodic tasks upon identical multiprocessors is proposed. This algorithm has an achievable utilization of (m + 1)/2 upon m unit-capacity processors. It is proven that this algorithm is optimal from the perspective of achievable utilization in the sense that no fixed-priority algorithm for scheduling periodic task systems upon identical multiprocessors may have an achievable utilization greater than (m + 1)/2.

关键词： 65 Real-time systems fixed-priority scheduling identical multiprocessors periodic task systems utilization bounds.

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Energy-Aware Partitioned fixed-priority scheduling for Chip Multi-Processors

Energy-Aware Partitioned Fixed-Priority Scheduling for Chip ...

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1st International Workshop on Cyber-Physical Systems, Networks, and Applications (CPSNA) held during 17th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA)

作者： Kandhalu, Arvind Kim, Junsung Lakshmanan, Karthik Rajkumar, Ragunathan (Raj) Carnegie Mellon Univ Dept Elect & Comp Engn Pittsburgh PA 15213 USA

ISBN: (纸本)9780769545028

Energy management is becoming an increasingly important problem in application domains ranging from embedded devices to data centers. In many such systems, multi-core processors are projected as a promising technology to achieve improved performance with a lower power envelope. Managing the application power consumption under timing constraints poses significant challenges in these emerging platforms. In this paper, we study the energy-efficient scheduling of periodic realtime tasks with implicit deadlines on chip multi-core processors (CMPs). We specifically consider processors with a single voltage and clock frequency domain, such as the state-of-the-art embedded multi-core NVIDIA Tegra 2 processor and enterprise-class processors such as Intel's Itanium 2, i5, i7 and IBM's Power 6 and Power 7 series. The major contributions of this work are (i) we prove that Worst-Fit-Decreasing (WFD) task partitioning when Rate-Monotonic scheduling (RMS) is used has an approximation ratio of 1.71 for the problem of minimizing the schedulable operating frequency with partitioned fixed-priority scheduling, (ii) we illustrate the major shortcoming of WFD with RMS resulting from not considering task periods during allocation, and (iii) we propose a Single-clock domain multi-processor Frequency Assignment Algorithm (SFAA) that determines a globally energy-efficient frequency while including task period relationships. Our evaluation results show that SFAA provides significant energy gains when compared to WFD. In fact SFAA is shown to save up to 55% more power compared to WFD for an octa-core processor.

关键词： Chip Multi-Processors Energy Management fixed-priority scheduling Energy management Water Framework Directive fixed priority priority scheduling PROCESSOR Energy efficiency partitions Root mean square Embedded device Multi-core processors data center

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Preference-Oriented fixed-priority scheduling for Real-Time Systems 12

Preference-Oriented Fixed-Priority Scheduling for Real-Time ...

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IEEE 12th International Conference on Dependable, Autonomic and Secure Computing (DASC)

作者： Begam, Rehana Zhu, Dakai Aydin, Hakan Univ Texas San Antonio San Antonio TX 78249 USA George Mason Univ Fairfax VA 22030 USA

ISBN: (纸本)9781479950799

Most real-time scheduling algorithms prioritize tasks solely based on their timing parameters and cannot effectively handle them when they have different execution preferences. In this paper, for a set of periodic tasks, where some tasks are preferably executed as soon as possible (ASAP) and others as late as possible (ALAP), we investigate preference-oriented fixedpriority scheduling algorithms. Specifically, following the idea in dual-priority scheduling, we derive promotion times for ALAP tasks (only). Then, we devise a dual-queue based fixed-priority scheduling algorithm that retains ALAP tasks in the waiting queue until their promotion times to delay their executions while putting ASAP tasks into the ready queue immediately once they arrive for early execution. We also investigate online techniques to further expedite (delay) the executions of ASAP (ALAP) tasks, respectively. Our evaluation results show that the dual-queue technique with ALAP tasks' promotion times can effectively address the execution preferences of both ASAP and ALAP tasks, which can be further improved at runtime with wrapper-task based slack management. Our technique is shown to yield clear advantages over a simple technique that periodically inserts idle intervals to the schedule before ALAP tasks are executed.

关键词： Real-Time Systems fixed-priority scheduling Preference-Oriented Execution

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Some Practical Results About fixed-priority scheduling and Offsets

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IFAC Proceedings Volumes 2000年第7期33卷 103-108页

作者： J.M. López J.L. Díaz M. García D.F. García University of Oviedo Department of Computer Science Campus de Viesques 33204 Gijón Spain

This paper focuses on schedulability tests of periodic task sets using fixed- priority scheduling, from a practical point of view. For the special case of task sets with offsets equal to zero (synchronous case), we compare different sufficient schedulability tests for Deadline-Monotonic (DM) scheduling, in terms of complexity and processor utilization. Finally, we consider the general case in which the offsets are arbitrary (asynchronous case). We show by simulation that the DM priority assignment is nearly optimal for asynchronous task sets. In addition, we compare the schedulability improvement of asynchronous task sets over their synchronous versions. Unfortunately, no practical improvement in schedulability is obtained by using the optimal offsets and priorities.

关键词： Real-time tasks schedulability test synchronous task sets asynchronous task sets fixed-priority scheduling uniprocessor systems

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