Supported by the National High-Tech Research and Development Plan of China under Grant Nos.2001AA113201, 2003AA115440 (国家高技术研究发展计划(863))
开放计算环境下的实时与非实时任务不确定并发,以及多种实时约束混合的复杂约束系统,即开放混合实时系统的需求越来越广泛.通过引入接收控制、调度服务器、自适应调节机制,提出一种开放环境下的自适应实时系统调度架构--OARtS(open adaptive real-time scheduling).它能适应开放计算环境的不确定性,有控制地接受实时任务运行;可根据系统空闲计算带宽变化,自适应地调节任务的实时等级,使得系统运行在最优的实时性能上;对于软实时任务,可根据其计算带宽需求变化,自适应地调节其计算带宽分配,以适应任务执行时间时变引起的实时不确定性.
To meet the system scheduling requirements of open hybrid real-time systems, an open adaptive real-time scheduling framework, called OARtS (open adaptive real-time scheduling), is presented in this paper, which comprises three key components: accept control, scheduling server and adaptive control. To guarantee the schedulability in the open environment, OARtS only accepts the task whose computing bandwidth requirement is no higher than the system's spare one. To schedule multi-constraint tasks, a two-layer scheduling mechanism is introduced. In the mechanism, the scheduling server components provide concurrent scheduling mechanism for multi-constraint tasks, and each of them is assigned to a bandwidth-independent computing bandwidth and has its specific scheduling policy to schedule its own task queue. To adapt to the change in the open environment, the adaptive control tries to tune the real-time service level so as to make full use of the system computing capability; to adapt to the uncertainty of execution time of the soft real-time task, a fuzzy control engine is used to regulate the task's computing bandwidth according to fuzzy rules of the scheduling error so as to eliminate the scheduling error and to get a satisfactory soft real-time performance.