Research And Implementation Of Embedded Real-time System Based On Linux

With the vigorous development of embedded systems, embedded products has beenaround us everywhere. Embedded products become more complex, the Linux system hasits source code completely open, good stability and compatibility, support for many kindsof processor architectures, the excellent characteristics has attracted the eyes of manyembedded developers. Linux was originally designed in consideration to the desktoptime-sharing system, so its real-time support is not perfect. The design principle is tomaximize the average real-time response and processing speed. Although Linux2.6andlater versions also joined some real-time supports, including the O (1) algorithm andkernel preemption, it still has some drawbacks. So Linux used in embedded real-timesystem still needs some improvement.In this paper, detailed analysis of real-time code of the Linux kernel are made,including the Linux process scheduling mechanism and interrupt mechanism, modernoperating systems commonly used process scheduling algorithm analysis and comparisonof scheduling algorithm in some versions of Linux, and the preemptive kernelmechanism is studied. To overcome the weaknesses of the Linux kernel to supportreal-time improvement, improvements mainly lie in the following aspects: First, addingperiodic scheduling algorithm to solve the lack of support of periodic tasks, and improvingwaiting queuing mechanism, adding a class of the process of scheduling; and then inresponse to high system load, high interrupt load, the interrupt thread transformation ismade; and improvement of the system clock mechanism is made. Then verification andanalysis of the effectiveness of these improvements, especially in the case of heavy loadis made, and the improvements are proved effective. Finally, the improved Linux system istransplanted to the ARM9processor based mini2440, thus a Linux-based embeddedreal-time systems is implemented.The outcome of this study can be used for embedded applications which requireshigh real-time performance. And the real-time performance of this system can be in10microseconds level, and it can meet the requirements of most embedded real-timesystems.