【摘要】 在分析Linux实时性的同时,指出了将其应用于实时系统时所存在的不足,提出了一种提高Linux实时性的思想及实现方法.该方法将进入系统的所有任务按实时性要求不同分成硬实时任务、软实时任务和非实时任务三种,依次用task-struct结构中policy属性的取值SCHED-FIFO,SCHED-RR和SCHED-OTHER作为标识,把原Linux的单运行队列改为双运行队列.为严格保证硬实时任务的实时性,将其单独放在一个队列中,由指针数组的元素run-queue[0]指向,采用FIFO调度算法;软实时任务和非实时任务放在一个队列中,由指针数组的元素run-queue[1]指向,采用RR调度算法,通过抢占方式保证软实时任务优先于非实时任务.修改sched()函数的调度流程,使有实时性要求的任务尽可能多的得到调度机会;同时修改中断处理流程,实现可抢占式改造,达到硬实时任务可抢占软实时和非实时任务,软实时任务可抢占非实时任务的目的.更多还原

【Abstract】 This paper focused on the application of Linux in the embedded system. The real-time performance of Linux was analyzed, and its disadvantage was pointed out when applied to the embedded system. An effective method capable of improving the real-time performance of Linux was presented. The tasks entered into the system were divided into hard real-time tasks, soft real-time ones and non real-time ones by their different requirements of the real-time. Each type was noted by its policy value such as SCHED_-FIFO,SCHED_-RR and SCHED_-OTHER in task_-struct accordingly, and a double run queue used instead of the original single run queue. To ensure the requirements of the hard real-time tasks, these tasks were organized in a run queue pointed by run_-queue[0], an element of a point array, and FIFO schedule strategy was used for them. The soft real-time tasks and non real-time tasks were put into the other run queue pointed by run_-queue[1], the other element of the point array, and RR schedule strategy was used for them. One is to modify the procedure of the sched( ) function to schedule more the tasks witch real-time requirements, and the interrupt processing procedure was also modibied, soft real-time tasks and non real-time tasks being occupied by hard real-time tasks and non real-time tasks occupied by soft real-time tasks.更多还原