Research On Hardware Implementation Of Task Scheduling Algorithm Of Real-time Operating System

With the rapid development of computer technology, the performance of embedded systems become more and more powerful and have played a crucial role in more and more areas, such as national defense science and technology,production automation, smart mobile terminals. In the real-time operating system, the timely response for real-time tasks is first-line, so many embedded systems regard the real-time operating system as the control kernel. The task scheduling algorithm is the key gist for the real-time operating system to complete the multi-task concurrent scheduling.Currently, task scheduling algorithm based on software has been unable to significantly improve real-time performance of system, and the hardware logic can concurrently run with the central processor, so this paper task explored the potential multi-task concurrency of the real-time system by the hardware implementation of scheduling algorithm. In addition, in the face of the more and more complicated application requirements in the embedded system field, the existing real-time operating systems often exhibit application limitations. In order to improve the real-time operating system adaptability, improving the existing real-time operating system kernel has become a major research focus. In this paper, ?C/OS-II is the object of study. Arming at the limitations of the lack of the same priority task scheduling, the original task scheduling algorithm was improved and implemented in FPGA.In this paper, the improved scheduling algorithm has two level scheduling.Firstly, the highest priority of the ready tasks was selected according to the original ?C/OS-II task scheduling algorithm based on the task priority, and then the scheduling strategy of the same priority tasks was started. In the scheduling ofthe same priority tasks, the fairer round-robin algorithm was adopted for the real-time task group with the same priority tasks, and the less overhead first-come-first-served algorithm was adopted for the non-real-time task group with the same priority tasks.In order to implement the scheduling of the same priority tasks, the task control blocks of ?C/OS-II were modified so that one priority can map many tasks. Then, the priority threshold set by the user was added as the dividing line,which divides all tasks in the system into two parts. The tasks with the priority which is less than the threshold are real-time; the tasks with the priority which is bigger than or equal to the threshold are non-real-time. Finally, the hardware task scheduler based on the algorithm was implemented in FPGA, described in VHDL and simulated in ISE 10.1.