A Research On Scheduling For Open Hybrid Real-Time Systems

Real-time systems are mainly designed to satisfy the timing requirements from the real world applications. They are widely adopted in many areas, such as industrial controls, aerospace electronics, military equipments, and so on. A real-time system concerns not only the logic correctness of the computing results, but also the time when the results come out. With the development of real-time system applications, the cases that different kinds of hard real-time, soft real-time and non-real-time applications coexist in one system become more and more popular. This situation makes the application requirements become more complex and causes the proposition of the open hybrid real-time system.In this thesis, the scheduling problems for open hybrid real-time systems are discussed. A new integrated scheduling framework, named RPDS (Rigorously Proportional Dispatching Server), is presented. For the popular imprecise real-time environments, this thesis presents a feedback control real-time scheduling algorithm, NF-QoS (Normalized Fair QoS). Basing on the concrete operating system platform (MiniCore), this thesis discusses the design and implementation of integrating RPDS and NF-QoS, and constructs a prototype real-time operating system, RT-MiniCore.In hybrid real-time systems, schedulers must guarantee that all of hard real-time tasks will be finished by their deadlines as well as the improvement of QoS of soft real-time tasks and non-real-time tasks as greatly as possible. RPDS is presented for resolving this problem, and a hierarchical scheduling framework is constructed based on it. RPDS isolates different kinds of real-time tasks to schedule them with different schedulers, and dispatches time slice to them consolidatedly. RPDS partitions CPU time flow into continuous segments, and in each segment RPDS will forcibly assign one time slice to non-hard real-time tasks. This results in the minimization of the deadline miss ratio (DMR) of soft real-time tasks.QoS fairness is an important problem in multi-QoS-level adjustable dynamic real-time scheduling systems. In this thesis, a concept named normalized QoS fairness is presented to add task importance factor to fairness. The NF-QoS real-time...