Research And Implementation Of Real-Time Linux

In recent years, real-time operating system has been widely used in the defense, Industri- al control, communications and other fields, and it is also a research focus and emphasis. But the commercial real-time operating system has been greatly restricted in the application beca- use its price is high and the source code does not make it opening up.Since Linux is launched, Linux has been rapid development and wide application becau- se of its open source and other characteristics. Linux2.6 improves the capacity for real time tasks by the use of preemptive kernel, O (1) scheduling algorithm and so on. However, it is still not a real time kernel. Hence Linux2.6 is needed to improve real-time, and improve the real-time performance to meet application under a variety of real-time environment. The prin- cipal method of Linux real-time is refining the system clock granularity, to improving the scheduling performance of the kernel scheduler, and enhancing kernel preemption performan- ce.On the basis of in-depth study of Linux2.6 kernel code, This paper conducts a detailed analysis and summary focusing on the Linux clock mechanism and scheduling mechanism and improve the disadvantage in real time applications. In terms of refinement-clock granula- rity, it draws on the UTIME mechanism of KURT-Linux system, introduces the one shot clock mode into the 2.6 kernel, achieves a mixed clock mode, reaches a microsecond timing accuracy, and solve the problem of clock accuracy. Scheduling algorithm for real time process is simple in Linux2.6, but Linux2.6 can not meet the timing- requirements of real time tasks. This paper combined of the performance on different scheduling algorithms under different system loads and proposed classification scheduling algorithm (CSBOT) based on threshold, when the system is light load, scheduling algorithm based on thresholds LSF is adopted ;the sheduling algorithm of the Criticality / Emergency degrees is adopted when the system is overload, it taked into account the system efficiency during light load and the implementation of the important tasks when overloaded.Finally, the test showed that the modified kernel can get microsecond timing accuracy. Classification scheduling algorithm which is based on threshold-based has the same system utilization with the classical EDF algorithm in the light load , it can guarantee the implement- ation of important tasks in the overload and achieve the elegance of the performance degrade- ation, effectively enhance real-time scheduling capabilities of the Linux system.