New Optimal Solutions for Real-Time Reconfigurable Periodic Asynchronous OS Tasks with Minimizations of Response Times
New Optimal Solutions for Real-Time Reconfigurable Periodic Asynchronous OS Tasks with Minimizations of Response Times
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DOI：
10.4018/978-1-4666-3922-5.ch012
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发表时间：
2013
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影响因子：
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通讯作者：
H. Gharsellaoui;Atef Gharbi;O. Mosbahi;M. Khalgui;A. Valentini
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作者：
H. Gharsellaoui;Atef Gharbi;O. Mosbahi;M. Khalgui;A. Valentini
本研究工作涉及可重构单处理器嵌入式实时系统的经典实现不同的操作系统任务，我们假设独立的，异步的和周期性的，以满足功能和时间属性描述的用户需求。我们在书的章节中定义了一个可抢占的，异步的和周期性的可重构的任务系统的任意相对的最后期限，调度在单处理器上的EDF原则和动态重构的基础上的最优调度算法的可扩展性算法。假设在运行时应用的两种形式的自动重新配置：添加-删除任务或仅修改其时间参数：WCET和/或Periods。然而，当这样的场景被应用于保存系统在发生硬件软件故障，或提高其性能，一些实时属性可能会被违反。我们定义了一个新的语义的重新配置，其中一个重要的标准是考虑自动改善系统的可行性在运行时，通过使用智能代理，自动检查系统的可行性后，任何重新配置的情况下，以验证是否所有的任务满足所需的最后期限。实际上，如果在运行时应用重新配置场景，则智能代理动态地为用户提供其他宝贵的技术解决方案，以根据预定义的启发式方法删除某些任务（基于软任务或硬任务），或者通过修改违反相应约束的任务的最坏情况执行时间（WCET）、周期和/或最后期限，以满足最后期限并尽量缩短响应时间。为了处理所有可能的重新配置解决方案，我们提出了一个基于代理的架构，应用自动重新配置，以重新获得系统的可行性，并满足用户的需求。因此，我们开发了工具RT-重新配置来支持这些贡献，我们将其应用于Blackberry Bold 9700和Volvo系统作为运行示例系统，并应用实时模拟器Cheddar来检查整个系统行为并评估算法的性能（详细描述可在网站上获得：http://beru.univ-brest.fr/~singhoff/ cheddar）。我们提出了这种架构的模拟，我们评估我们实现的代理。此外，我们提出并讨论了实验的结果，比较我们的算法的准确性和性能与他人。引言实时系统在我们的社会中发挥着至关重要的作用，在过去的二十年里，在我们的日常生活和工业生产中使用的实时系统的数量出现了爆炸性的增长。诸如化学和核工厂控制、空间任务、飞行控制系统、军事系统、电信、多媒体系统等系统都使用实时技术。实时系统最重要的属性是，这种系统的正确性不仅取决于计算结果，而且还取决于产生结果的时间。换句话说，实时系统具有必须保证的时序要求。调度和可重复性分析使这些保证得以提供。
This research work deals with Reconfigurable Uniprocessor embedded Real-Time Systems to be classically implemented by different OS tasks that we suppose independent, asynchronous and periodic in order to meet functional and temporal properties described in user requirements. We define in the book chapter a schedulability algorithm for preemptable, asynchronous and periodic reconfigurable task systems with arbitrary relative deadlines, scheduled on a uniprocessor by an optimal scheduling algorithm based on the EDF principles and on the dynamic reconfiguration. Two forms of automatic reconfigurations which are assumed to be applied at run-time: Addition-Remove of tasks or just modifications of their temporal parameters: WCET and/or Periods. Nevertheless, when such a scenario is applied to save the system at the occurrence of hardwaresoftware faults, or to improve its performance, some real-time properties can be violated. We define a new semantic of the reconfiguration where a crucial criterion to consider is the automatic improvement of the system's feasibility at run-time by using an Intelligent Agent that automatically checks the system's feasibility after any reconfiguration scenario to verify if all tasks meet the required deadlines. Indeed, if a reconfiguration scenario is applied at run-time, then the Intelligent Agent dynamically provides otherwise precious technical solutions for users to remove some tasks according to predefined heuristic (based on soft or hard task), or by modifying the worst case execution times (WCETs), periods, and/or deadlines of tasks, that violate corresponding constraints by new ones, in order to meet deadlines and to minimize their response time. To handle all possible reconfiguration solutions, we propose an agent-based architecture that applies automatic reconfigurations in order to re-obtain the system’s feasibility and to satisfy user requirements. Therefore, we developed the tool RT-Reconfiguration to support these contributions that we apply to a Blackberry Bold 9700 and to a Volvo system as running example systems and we apply the Real-Time Simulator Cheddar to check the whole system behavior and to evaluate the performance of the algorithm (detailed descriptions are available at the website: http://beru.univ-brest.fr/~singhoff/ cheddar). We present simulations of this architecture where we evaluate the agent that we implemented. Also, we present and discuss the results of experiments that compare the accuracy and the performance of our algorithm with others. INTRODUCTION Real-Time systems are playing a crucial role in our society, and in the last two decades, there has been an explosive growth in the number of real-time systems being used in our daily lives and in industry production. Systems such as chemical and nuclear plant control, space missions, flight control systems, military systems, telecommunications, multimedia systems, and so on all make use of real-time technologies. The most important attribute of real-time systems is that the correctness of such systems depends on not only the computed results but also on the time at which results are produced. In other words, real-time systems have timing requirements that must be guaranteed. Scheduling and schedulability analysis enables these guarantees to be provided.