端到端实时CORBA系统调度模型及其可调度性研究

Research on End-to-End Scheduling Model for Real-Time CORBA System and Its Schedulability

实时CORBA系统中的基本问题是如何合理分配有限的计算资源和通信资源以保证各个实时任务的时间需求 .该文以固定优先级方式调度的、周期性任务的硬实时系统为研究对象 ,提出了端到端实时CORBA系统调度模型 ,该模型综合考虑了客户端系统的处理、服务对象处理、网络传输等几大主要因素 ,而且可以描述服务对象间的嵌套调用关系 ,因而能全面描述实时CORBA系统中客户调用过程 .在此基础上 ,该文基于非连续工作型同步协议 ,应用时间需求分析方法 。

The essential problem of Real-Time CORBA system is how to allocate limited computing and communication resources to real-time tasks so as to meet the time demand of every task. This paper, in terms of periodic hard real-time systems with fixed-priority, proposes an end-to-end scheduling model for Real-Time CORBA system. Compared with other Real-Time CORBA scheduling models, the model considers the costs of client processing, network transmission and server processing. So it can describe client invocation procedure of real-time CORBA systems more precisely. Besides it can model nested invocation of CORBA servers. Therefore, it is suitable for analysis of periodic hard real-time systems with fixed-priority. Based on non-greedy synchronization protocol and the time demand analysis method, the schedulability of the model is studied. According to the priorities of subtasks and the relationships between them, the interference function of subtasks on the same processor can be calculated. Then the time demand functions with respect to subtasks on both preemptive processor and non-preemptive one are deduced respectively. Hence the worst-case end-to-end response time of each task can be calculated. Finally, a schedulability analysis algorithm is proposed.