Improvement Of EDF Scheduling Algorithm For Embedded Real-time Operating System ARTs-OS

With the constant growing demand for real-time processing in people's production and life, Embedded Real-Time Operating System (ERTOS) is used more and more widely. Real-Time Scheduling algorithms have an important effect on the real-time performance of ERTOS, is the key to improve the real-time performance.ARTs-OS is an embedded real-time operating system which is designed and developed by ourselves laboratory. The system uses micro-kernel structure, the size of the kernel is small and user can load modules dynamically. The task management module uses process/thread model, has memory protection among processes which makes the system more stable. Object Oriented Programming is introduced into the designing of scheduling module. User can develop a new scheduling object to change the scheduling way instead of changing most modules of the system.The essence of scheduling is the allocation and use of processor resources. As an optimal dynamic priority scheduling algorithm, EDF algorithm has low running cost and high processor utilization. But the scheduling cost of EDF algorithm is large, and the priority decision mechanism is too simple can't reflect the importance of the tasks. When the system overloads, EDF algorithm will have a"domino effect", causing most of the tasks miss their deadline. Using a factor which reflects the importance of task and deadline to decide the priority of task, the application requirement can be better met. Selecting important tasks to scheduling can avoid the"domino effect".Apply the improved EDF algorithm to Arts-OS, schedule tasks under different system environment. The experimental results show that when the system is overloading the improved EDF algorithm can assure the requirement of important tasks firstly.