Modification and adjustment of real-time tasks with rate monotonic scheduling algorithm

Abstract

Many researches on dynamic scheduling techniques for real-time systems have focused on changes in the number of tasks. We propose a dynamic real-time scheduling technique, called MART, in which it is also possible to change task characteristics. When MART is used in systems where task characteristics need to be and can be modified, it enables the system to be adaptable to changing environments dynamically and flexibly. By using MART, systems can accept on-line requirements such as changing task timing characteristics, and adding or deleting tasks. If a task set becomes unschedulable as a result of such modifications, MART can determine a schedulable task set. Though MART must adjust timing characteristics of other tasks to guarantee the schedulability of all tasks, the need for such adjustments is reduced. We also argue the importance of predictability in real-time computing, then improve the predictability of MART by introducing the notion of importance into each task. MART uses "importance" as a factor for task characteristic adjustment.<>