The Real-Time Perfamance Research Of CORBA

CORBA is a kind of specification made by OMG organization. It is used to solve the heterogeneous problem of system. As an object-oriented middleware, CORBA uses standard interface defined by OMG IDL to carry out transparent alternation between client and server through ORB, a middle broker, which implements actual inter-operation among different software and hardware products, with the characters of across-platform, across-language and across-network. Therefore, CORBA plays the role of software bus in a distributed system, and has become typical representative and mainstream technology of distributed object computing technology. It greatly reduces the complexity when developing distributed system.No distributed real-time application requirement, however, is considered in the current CORBA software when designed. It is devoid of support to QoS, real-time programming feature and performance optimization, and has the congenital deficiency in architecture. Theselimitations of CORBA restrict the application of it in real-time domain, and can't satisfy the special demands of distributed real-time application for clock synchronization, time predictability and real-time task scheduling, etc. So some improvements should be made.In this paper, the system architecture and the request calling mode of CORBA are analyzed. They are compared with DCOM of Microsoft. The difference and resemblance between CORBA and DCOM are also pointed out. Because of the deficiency of CORBA in distributed real-time application, some practicable methods are discussed to make CORBA have some real-time characters and fault-tolerant capability, by extending the current CORBA based on the existing operating system. The author mainly studies the real-time performance of VisiBroker, an ORB product of Inprise Corp under C++Builder environment. First, an experiment is designed to analyze some real-time performance of VisiBroker qualitatively, and the delay time of 9 tasks is got, using multithreading to simulate multitask on the CORBA client. Then, MIF - a real-time scheduling algorithm, is introduced and implemented on the client, which makes multitasks be performed with reasonable sequence according to actual need and runtime be predictable. Thus system's QoS is enhanced, and VisiBroker's real-time performance is improved. In the end, the author makes a prospect of the new development of CORBA-Real-Time CORBA, whose architecture is analyzesd and the thread pool strategy, thekernel of which, is expatiated on, including such two architecture models as Half-Sync/Half-Async and Leader/Followers.