Research On Timing Analysis Of Distributed Real-time Systems

The accuracy of a real-time system depends not only on the correct operation of the system but also the timeliness of the system. And it is closely related with the real-time scheduling strategy, which is the centre point of the resource allocation. Then, the allocation of resources is reflected as the execution sequence between tasks in the system. In a distributed real-time system, this problem is particularly important. On this basis, the focus of this thesis is on the use of analytical methods in a distributed real-time system.Timing analysis models for modern applications involving distributed systems are prone to being holistic, i.e., it is difficult or impossible to analyze the timing behavior of parts of the system in isolation from other parts. This problem occurs due to the combined impact of functional dependencies and physical inter-dependencies between tasks, giving rise to cyclic inter- dependencies within the timing model.Based on the above problems, this paper introduces the concepts first, then describes some classical scheduling algorithms in different classifications, and makes some discussion on their respective scope. After that, some suitable means of partitioning the timing analysis model is proposed and discussed, following by introduction of the timing analysis method specifically, which can be used in distributed real-time systems, also referred to as reservation-based timing analysis.For the above approach, the timing characteristics of a distributed real-time system are represented in terms of compound transaction model, which with the hierarchical structure. In order to determine the end-to-end timing characteristics of the transactions in the system, firstly, applying the business process modeling theory, a software process timing model of the real-time system is constructed, and end-to-end timing model of a single transaction is established. Secondly, the various types of precedence and nesting relationships in the transaction model are discussed, and the timing properties under these relationships are analyzed. Then, based on some localized timing analysis model, from the perspective of single activity resource requirements, a study of the relationships between response times, execution rate and resource requirements are built up. Finally, through an GAP example used by the basic cyclic scheduling strategy, the feasibility of the proposed timing analysis method is verified, and a conclusion about relevant results is given.