Research And Improvement Of Real-Time Capability Of Embedded Linux System

In today, embedded technology is popularizing rapidly. Linux, as its open source, high stability, low cost and some other characteristics, is so fit for embedded system developments and has become the fastest developing operating system in this field. Improving general Linux's real-time capability to make it more fit for embedded system applications is in great practical significance and has become one of hot research directions in domestic and foreign computer fields.On the basis of reading and research of Linux 2.6 kernel resource codes and lots of documents and materials, the paper gives the deep analyses and summaries of Linux 2.6 kernel's task scheduler mechanism, timer mechanism, virtual memory mechanism and resource preemption technology. As the improvement solution, as to the problem of Linux 2.6 kernel lacking in real-time scheduling algorithms and policies in the scheduler mechanism, the "laxity" notion is introduced from the good dynamic real-time scheduling algorithm LSF(laxity small first). Combination of the laxity and the new task scheduler data structure in Linux2.6 enhances the system's real-time scheduler capability as well as maintains the original O (1) scheduling characteristic;As to the problem of Linux 2.6 kernel's too large timer granularity in timer mechanism, One-shot Mode is introduced in Linux timers from the principle of timer mechanism improvement in Kurt-Linux. For the more, using of real-time task's "laxity" attribute in the improved dynamic real-time scheduler system, the new timer mechanism is implemented skillfully. The new timer mechanism makes the system reached the microsecond level timer precision and maintains its original load capability.In the part of real-time capability testing, Linux 2.4 kernel, Linux 2.6 kernel and the improved system are compared on interrupt response time and context-switching time which are two key criterions of real-time testing. From the testing results, we can see that the improvedLinux system which uses the real-time task's "laxity" as the connection to make the combination of the real-time dynamic scheduler mechanism and one-shot minute granularity timer mechanism has the stronger real-time capability than Linux 2.6 kernel. It is more fit for the high real-time application in embedded fields.In addition, as the prospect of Linux system's real-time capability research, on the base of the kernel preemption implementation, the research and implementation of preemption mechanism as to the system resources besides CPU (e.g. memory, disk) is a more valuable research direction.