Real-time Research Of Embedded Operating System Based On Linux

Among main open source softwares, Linux is quickly entering the real-time control field with open kernel source codes, stable performance, UNIX compatibility, multiple processes applicability, great network capabilities, high security and pruned kernel. In the beginning, Linux is designed as all-purpose operation system on the basis of fundamentals that the average response time is as possible as short and the throughput is as possible as high. Although Linux also supports the real-time process with POSIX compliant real-time function, multithread, multitasks, its real-time capability is very poor. Linux does not ensure the response time of real-time task.Based on the Linux kernel source codes, the interrupt, process scheduling, virtual memory, file system and so on are analyzed. The scheduling latency, interrupt latency, context switch time, the latency caused by virtual memory and file system are also analyzed and measured. Taken decreasing the scheduling latency as a breakthrough, the interrupt and spinlock will be optimize to improve real-time capability of Linux kernel.First, the synchronization and its disadvantage of Linux are discussed. The method that mutex replace spinlock is presented. Then, the interrupt handling and its disadvantage of Linux are analysized. According to the shortage, the improvement of the threaded interrupt is picked out. They reduce the scheduling latnecy, improve the response time of the real-time process in the kernel, meanwhile keep the system consistent. Finally, the implement and testing of the two improvements are presented. The experiment results show that the real-time response capability in Linux has bettered a great deal and the compatibility of operation system has been held very well.