Research On Predictability Of End-to-End Response Time Of The Tasks Based On TAO

With rapid development of computer network, the applications of distributed real-time systems become more and more popular. Real-time requirement exists in many fields such as information appliance, medical instrument, intelligent vehicle, process control in industry and communication device. How to meet the demands of the real-time quality of service (RT-QoS) becomes a hot spot which researchers concern. The response time of real-time tasks is an important factor which affects system design, task scheduling and resource allocation. It has much practical significance to know it in advance and make it to satisfy timing constraint. But since there are the factors such as task preemption, resource competition, timer interrupt, I/O collision, some real-time tasks with random behavior and so on, it is very difficult for the systems to predict the response time of the tasks by traditional methods.The purpose of the paper provides the guide for system design, the basis for system scheduling and the guarantee for task execution by predicting end-to-end response time of real-time tasks. Real-time CORBA extends the components which meet the real-time requirement in the original CORBA frame, so that it supports the operation of end-to-end predictability of the system, and guarantees the real-time application. Based on this real situation, the paper presents a series of strategies and mechanisms to guarantee the predictability of the response time of these tasks, including periodic tasks, aperiodic tasks and sporadic tasks.Research on end-to-end response time is started from the presumed code of real-time CORBA application. According to the end-to-end scheduling method, the prediction analysis of end-to-end response time of the tasks in the distributed real-time systems is localized, and through establishing a node model, the response time is decomposed into several parts, and then using the methods, such as two levels' scheduling scheme, time-demand analysis, queuing theory and so on, each part of the response time is analyzed. Finally, the predicting result based on the above is compared with the real result based on the TAO, the comparing result shows thelightness of the work, the result has the good reference significance for the design and the task scheduling of real-time CORBA application system.