Embedded Operating System Support Layer Scheduling Management Of The Design And Realization

Embedded systems are widely used as the control part of network devices. With the rapid growth of the network application, network devices, which carry the net load, are required to be faster, support multi-media and varied protocols. These increase the complexity of the embedded system of modern network devices. Embedded operation system support layer (EOSSL) is introduced into the network devices to reduce the difficulty of their software development. EOSSL is an extension of embedded operating system, which supports the application software development of network devices.We studied the embedded system, embedded operating system and VxWorks. And then, the dissertation briefly describes the embedded operating system support layer. Based on these, the mainly part of the dissertation describe the design and implement of schedule management of EOSSL in detail. First, we discuss the architecture of the schedule management module. Then, the dissertation describes the design and organization of the core data of the schedule management module. In the end, the dissertation describes the design and implement of process queue operation sub-module, process communication sub-module, process schedule sub-module and process control sub-module.Schedule management of EOSSL implements a two-stage schedule system. The first-stage is task schedule using preempt schedule based on task priority implement by VxWorks and the second-stage is process schedule using FIFO schedule drive by message implement by schedule management of EOSSL. Process is a smaller granularity schedule unit carries by VxWorks task and can be regarded as sub-task.In the design of core data, we introduce a logical mutual exclusion method to access the core data. This method ensures core data consistency not by using mutual exclusion semaphore. In process communication sub-module, we introduce and implement a zero message copy mechanism to transfer message. This mechanism can greatly increase the efficiency of message transfer. In process schedule sub-module, we introduce and implement a message driven FIFO process schedule mechanism. This mechanism is as simply as FIFO and can assure justify and fast response to the process in the system.