Research On Weakly Hard Real-Time Linux System Supporting QoS

With the development of computer technology, in particular the development of network multimedia technology, it will be more and more popular that applications of real-time and unreal-time application coexist in one real-time system. Real-time systems to support QoS (Quality of Service) will be often encountered.In real-time operating system, Linux will become more and more popular because of its open source code and there will be many real-time systems to adopt Linux as operating system. Therefore, it is urgent work to establish a open real-time system based on Linux. The research and development of open real-time Linux system will greatly improve the applied ability of Linux, which adapt to the development of modern computer systems and real-time system.On the basis of the definition of WHRT (Weakly Hard Real-Time), this dissertation summarizes the constraint qualifications of the existing WHRT and scheduling algorithms, places emphasis on the discussion of DBP algorithm and E-DBP algorithm. Two concepts are proposed according to the deficiencies of the two algorithms, namely total distance of entering invalidation and total distance of aborting invalidation, and the distance calculation equation is presented. TDBP (Total Distance Based Priority) extends the priority setting methods of DBP and E-DBP further more which solve the problem of the 0 /1 state distributing information ignored in both algorithms.In the basis of weakly hard scheduling algorithm, this paper make a further research combined with open real-time Linux system. In the process of research, it is found that the scheduling algorithm of the open real-time Linux system has the deficiency on scheduling fairness, which can not meet the QoS requirements of real-time network when the system is overloaded. However, TDBP can solve the problem above well. So, this dissertation presented the WHRT-Linux system model, which makes Linux system more flexible and suitable for real-time network multimedia applications.Finally, based on the study of the principle and structure of OPNET, the E-DBP and TDBP algorithms are realized on OPNET 10.0.A_PL1Modeler platform. The simulation results show that TDBP is better on dynamic failure rate, time-delay and fairness of scheduling compared with E-DBP.