Improvements Based On The Linux Real-time Scheduling Policy

The Realtime operating systems are wide used in every fields, and they are taken more seriously. In numerous realtime operating systems , operating systems base on linux are produce a favourable response from the public for opened source codes and stable. But linux is not real realtime operating system,so we should improve realtime capability of the linux . Improving realtime capability of the linux is hot at national and international. For the present, to enhance the realtime capability of Linux , The realtime support of Linux kernel is studied and implemented through four spects:Compliant Kernel Approach , DualK ernelA pproach, Core Kernel Approach and Resource Kernel Approach and so on .The means of Core Kernel Approach are fine-grain timer of Linux ,improving preemption of kernel, improving the schedule policiese of real time scheduler . Scheduling algorithm is the most important factor. So in this article ,we adopt improving the schedule policiese of real time scheduler to enhance the realtime capability.In this article ,the last day Linux kernel(2.6.18 ) is analyzed here,in cluding the structures , functions and inner dependence, More work is given to the newly added process status in Linux header sched.h and the policies defined in task_struct.In this article,the kernel's schedule system is analyzed here,for example: FIFO(First Come First Serve) and RR(round-robin) scheduler. By the research of the design of Linux kernel scheduler and interrupt system compounded with the kernel idea of RM(Rate Monotonic Analysis) Algorithm and EDF (earliest dead line first) Algorithm.In this article,we add RM Scheduler and EDF scheduler in Linux kernel.RMS scheduler let shot period task have a high priority, EDF scheduler optimize schedulable load.These scheduler substitute FIFO and RR scheduler.We also adopt fine-grain timer scheme , minish the time of the system clock's granularity , to enhance the realtime capability of Linux .Realizing enhance the realtime capability of Linux need compiling the kernel of linux. In this article , we config the kernel , ensure the reliability of the system.At last we prove the improved kernel has realtime capability.