基于嵌入式Linux操作系统的实时性研究

发布时间：2018-12-18 09:41

【摘要】：实时操作系统是嵌入式系统的灵魂，它已经广泛应用在通信、工业控制、军事国防等对实时性要求比较高的嵌入式领域。通用操作系统仅注重系统的平均性能。对于整个系统来说，所有任务的平均响应时间是关键。与通用操作系统相比，实时操作系统的正确性不仅取决于计算的逻辑结果，而且还取决于计算结果产生的时间。作为开源的软件之一，Linux操作系统以其源代码公开、完全免费、兼容Unix、网络功能强、内核可裁剪、支持多种体系结构、性能稳定等优点正顺速地进入嵌入式实时系统领域。虽然Linux2.6提供了一些对实时处理的支持，如O(1)调度器、可抢占式内核等，但是它毕竟是一个分时操作系统，还是不能满足大多数嵌入式实时系统的要求。因此，为了让Linux操作系统满足嵌入式系统对实时性的要求，必须对Linux2.6内核进行实时优化。以Linux2.6内核为研究的基础，，本文对Linux2.6内核的时钟机制、进程调度机制、内核同步机制等进行了深入的分析。为了提高系统的实时性，本文提出了两种改进方案。针对Linux2.6内核的时钟粒度过粗的问题，提出一种基于APIC时钟的Linux实时化改进方案，通过对APIC时钟进行较少的改动，使得系统达到了微秒级的时钟精度。针对Linux2.6内核中存在大量的自旋锁保护的临界区不能被抢占的问题，提出一种在内核中用互斥锁替换自旋锁的方案，使得实时任务可以得到及时的响应，提高了系统的实时性。最后，通过测试，经过两种改进方案后的Linux2.6内核在实时性方面有了较大的提高，更能满足嵌入式系统的实时要求。
[Abstract]:Real-time operating system (RTOS) is the soul of embedded system. It has been widely used in embedded fields such as communication, industrial control, military defense and so on. The general operating system only pays attention to the average performance of the system. The average response time for all tasks is critical for the system as a whole. Compared with the general operating system, the correctness of the real-time operating system depends not only on the logical result of the calculation, but also on the time when the result is generated. As one of the open source software, the Linux operating system has the advantages of open source, free of charge, strong compatibility with Unix, network, clipping kernel, supporting various architectures, stable performance and so on. Although Linux2.6 provides some support for real-time processing, such as O (1) scheduler, preemptive kernel and so on, it is a timesharing operating system and can not meet the requirements of most embedded real-time systems. Therefore, in order for the Linux operating system to meet the real-time requirements of embedded systems, the Linux2.6 kernel must be optimized in real time. Based on the research of Linux2.6 kernel, this paper analyzes the clock mechanism, process scheduling mechanism and kernel synchronization mechanism of Linux2.6 kernel. In order to improve the real-time performance of the system, this paper proposes two improved schemes. In order to solve the problem that the clock granularity of Linux2.6 kernel is too coarse, an improved Linux real-time scheme based on APIC clock is proposed. By making less changes to APIC clock, the system achieves the clock precision of microsecond level. In order to solve the problem that a large number of critical areas of spin lock protection can not be preempted in Linux2.6 kernel, a scheme of replacing spin lock with mutex in kernel is proposed, so that the real-time task can get timely response. The real-time performance of the system is improved. Finally, through the test, the Linux2.6 kernel after two improved schemes has been improved greatly in real time, which can meet the real-time requirements of embedded system.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TP316.81;TP368.1

【参考文献】