基于嵌入式Linux的调度实时化的研究与实现

发布时间：2018-08-12 14:40

【摘要】：进入后PC时代，移动设备成为人们生活的重要工具。嵌入式系统在移动计算领域发挥着越来越重要的作用，其优势在于能够较好的结合微处理器及其专属软件，达到系统操作效率与成本的最大比。但是随着微电子技术发展，一颗芯片所集成的晶体管数达到数亿个，在其上负载的系统越来越复杂以致实时性越来越低，特别是在一些关键领域，如自动控制、核电站等，如果满足不了实时性要求将造成不可挽回的后果。因此，有必要就嵌入式系统实时性进行研究。嵌入式系统实时性主要包括系统对外部事件的响应、任务执行的及时性等。对外部事件响应称之为中断，包括中断延迟、中断响应以及中断处理阶段。对任务及时处理在通用PC里表现为调度。就任务调度而言，涉及调度算法、调度策略。现今比较成熟的调度算法有RM算法和EDF算法，其他调度算法都是基于它演变而来的。RM算法是一个静态的固定优先级调度算法。任务的优先级与任务的周期表现为单调函数关系。EDF算法是一种采用动态调度的具有更高CPU使用率的调度算法。本文通过深入分析Linux内核调度框架，归纳出其面向对象设计思想。通过分析已有的实时调度策略，发现Linux的实时性并不“实时”，因此本文针对嵌入式Linux环境提供调度实时化的保障机制，深入分析RM、EDF和自适应调度算法并将其引入Linux内核，，最后在基于Apollo平台的嵌入式Linux下编码实现这三种调度器，以此为平台通过实验测试数据表明三种调度器能保证任务执行的实时性，特别是在具有反馈机制的应用场合下自适应调度器极大地保证任务的实时性。
[Abstract]:In the post-PC era, mobile devices have become an important tool in people's life. Embedded system is playing a more and more important role in the field of mobile computing. The advantage of embedded system is that it can combine microprocessor and its exclusive software to achieve the maximum ratio of operating efficiency to cost. However, with the development of microelectronics technology, the number of transistors integrated into a chip has reached hundreds of millions, and the system loaded on it is becoming more and more complex and the real-time performance is becoming lower and lower, especially in some key fields, such as automatic control, nuclear power plant, etc. If can not meet the real-time requirements will cause irreparable consequences. Therefore, it is necessary to study the real-time of embedded system. The real-time performance of embedded system mainly includes the response of system to external events, the timeliness of task execution and so on. External event response is called interrupt, which includes interrupt delay, interrupt response and interrupt processing stage. Timely processing of tasks is represented as scheduling in general PC. As far as task scheduling is concerned, it involves scheduling algorithm and scheduling strategy. Nowadays the more mature scheduling algorithms are RM algorithm and EDF algorithm. Other scheduling algorithms are based on the evolution of the. RM algorithm is a static fixed priority scheduling algorithm. The monotone function relation between the priority of the task and the period of the task. EDF algorithm is a scheduling algorithm with higher CPU utilization rate using dynamic scheduling. In this paper, the object-oriented design idea of Linux kernel scheduling framework is summarized by analyzing its kernel scheduling framework in depth. By analyzing the existing real-time scheduling strategy, it is found that the real-time performance of Linux is not "real-time". Therefore, this paper provides a real-time scheduling guarantee mechanism for embedded Linux environment, and deeply analyzes RML-EDF and adaptive scheduling algorithms and introduces them into the Linux kernel. Finally, the three schedulers are coded under embedded Linux based on Apollo platform. The experimental data show that the three schedulers can guarantee the real-time performance of the task. Especially in the application with feedback mechanism, the adaptive scheduler can greatly guarantee the real-time performance of the task.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP368.1;TP316.81

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