【作者】 邹道生；

【导师】 马溪骏；

【作者基本信息】 合肥工业大学 ， 信息管理与信息系统， 2008， 硕士

【摘要】 实时系统具有及时响应、高可靠性、专用性、少人工干预等特征,最初应用于军事和工业控制领域。而随着计算机技术和互联网技术的高速发展,实时技术被越来越多地应用于实时网络传输、视频传输、多媒体处理等软实时系统中。这类实时系统既不同于硬性规定作业完成时限的硬实时系统,也不同于没有详细规定任务应满足何种约束的软实时系统。这些新的应用都有一定的服务质量(QoS)需求,既有实时性的需求,又有丢失率方面的需求。由于这些新的特点,传统静态硬实时系统和基于公平调度的通用操作系统已经无法满足这类实际应用的需要。同时窗口约束理论由于在描述QoS特性上具有概率约束无法比拟的优点,近年来得到了广大学者的研究和广泛关注。基于上述背景,本文结合开源的Linux系统,通过在其上引入窗口约束描述的QoS机制,采用合适的调度机制来满足弱硬实时系统的需求,与此同时开展了以下的研究:1)在研究基于窗口约束(m,k)模型的实时系统的基础上,给出了一种组合窗口约束(m,k)∧＜(?),k＞的实时系统,并针对其给出了一种新的组合窗口约束的调度算法,该算法充分利用组合约束的特点,考虑本次调度对该窗口的可调度的影响来确定任务的优先级,并以此来提高任务的可调度性、减少组合窗口限制违例。仿真试验表明该算法在组合窗口约束的调度上,优于传统的独立比较两个约束确定优先级的调度算法;2)结合组合窗口约束描述任务QoS更准确和便于调度算法设计的优点,同时针对标准Linux内核只提供三种调度策略:SCHED__RR、SCHED__FIFO、SCHED__OTHER,它们是无法实现具有QoS要求的任务调度的缺陷。本文通过可加载模块的方法,修改schedule()的调度策略,给出了组合窗口约束调度在Linux内核上的具体实现框架。更多还原

【Abstract】 The real-time system has characters such as response in time, high dependability, dedication and less artificial interference, it was used initially applied to the field of military and industrial control. However, with the rapid development of computer and internet technology, real-time technology has been applied more and more to soft real-time system (SRTS), such as real-time network transmission, video transmission and multimedia processing. This SRTS is different from hard real-time systems that mandatory limit the deadline of jobs, and different from some soft real-time systems that don’t make exactly rules for jobs. These new applications have a certain quality of service (QoS) requirements, which need satisfy the deadlines and loss-tolerance for jobs. As a result of these new features, Traditional static real-time systems and common operation system that based on fair scheduling can’t satisfy these new applications. At the same time, window theory of constraints have incomparable advantages than probability constraints in describing QoS, it receives the majority of scholars research andextensive attention in recent years.Based on the above background, this dissertation imports a QoS mechanism which described by window constraints into Linux kernel and uses a suitable scheduler for satisfying weakly hard real-time systems demands. And then contents about this were studied:1) Based on the research of window-constrained real-time system with (m,k) constraints, a non-overlapping assembled window-constrained real-time system with (m, k)(?)<h, k> constraints is proposed. By the research on schedulability of this real-time system, a new assembled window-constrained scheduling (AWCS) algorithm is prompted. The AWCS takes full advantage of the peculiarity of assembled constraints, and allocates the priority considering the affection of this scheduling for the total window, which improves the schedulability and reduces the violations of assembled window constraints. The simulation shows the AWCS is better than general algorithms that allocate priority by comparing these constraints independently.2) Combining the advantages of assembled window-constraints in exactly describing Qos and designing scheduler. And for the bugs of standard Linux kernel only can supply three schedulers: SCHED_RR, SCHED_FIFOandSCHED_OTHER, which can’t satisfy tasks’ QoS. By using the method of lodable kernel model (LKM), this dissertation revised schedule()’s strategy, and give a concrete realization of the framework for AWCS in Linux kernel.更多还原