Research And Improvement Of Embedded Linux Real-time Performance

Operating system, an important component in computer system, not only provides users with friendly service environment but also control the computer hardware / software resources to orderly operate. But in the field of embedded system, embedded operating system is commonly with functions of general-purpose operating system as well as with a certain degree of real-time performance. Real-time embedded operating system has become a hot research field. This paper elaborates on the real-time performance of embedded systems and use Linux operating system as object to alter its scheduler for better real-time.Firstly, this paper introduces the background and significance of the study, analyses the reasons for real-time defects of Linux, summarize the research of real-time Linux and methods for transplantation of Linux operating system. After, the papers take kernel of Linux2.6.22 edition for example to illustrate scheduling mechanism, scheduling policy and some data structure scheduling-related of kernel of Linux2.6 edition, and place emphasis on analysis of the classic Linux2.6 kernel scheduling algorithm -O (1) algorithm and three basic scheduling strategy coming with the system.After that , three scheduling strategy shortage in real-time were given. Based on the above, the paper studies two classical real-time scheduling algorithms (RM scheduling algorithm and the LSF scheduling algorithm), studies the schedulability of RM algorithm and gives assumedcondition for applying the RM algorithm. The idea on how to apply RM algorithm into Linux2.6.22 kernel scheduler is proposed. And paper use this idea to achieve altering Linux kernel for better real-time. Another scheduling algorithm (LSF) based on the "margin" is the classic dynamic priority scheduling algorithm. This algorithm could dynamically accomplish scheduling for process according to the process'"margin value". But the algorithm itself has defect which affect the efficiency of the algorithm. In this paper, the shortcoming of traditional LSF algorithm was improved to form new LSF algorithm which is named the jumpphase-based LSF .Then, the new LSF algorithm is put into the kernel of Linux 2.6 edition.After modifications of the kernel scheduler, the paper also analyze the kernel file and the process of the Linux kernel booting, construct a file system, and then complete the work of cutting and transplanting Linux kernel. In the end, the paper use kernel testing tool LTT (Linux Trace Toolkit) to test the parameters of the revised Linux kernel, and design experiment to illustrate the provement of system performance.