Rt-corba-based Task Running Time Prediction

Distributed real-time systems play a vital role in many areas, such as national defense, flight control systems, space shuttle and aircraft avionics. Predictability is one of the most important characteristics. Based on RT-CORBA system prototype, latency and jitter factors are analyzed and tested, which affect the system predictability. For periodic tasks in a distributed real-time system, a number of static allocation algorithms have been developed which solve the problem of assigning and scheduling tasks effectively under some determined conditions. The principal limitation of these approached is that the attributes of the tasks have to be known. Sometimes the execution time or the number of subtasks of a periodic task might be a stochastic process obeying some rule, thus the performance of the static schemes will decrease greatly. On the basis of the static allocation algorithms, a predicting algorithm is presented for the scheduling of multitasks in RT-CORBA systems. With the predicting algorithm, we can predict the task parameters reasonably and implement dynamic allocation of the tasks, so that the system can meet the timing requirements more efficiently. This paper makes three contributions to the design of RT-CORBA system. First, the paper defines the architecture of RT-CORBA. Second, under the analysis of distributed middleware applications, the paper presents a task model. Finally, the paper presents a RT-CORBA system model based on ACE/TAO and experiments show the efficiency of the predictability of tasks execution time in RT-CORBA systems.