Research On Exokernel System Scheduling

The Operating System (OS) is the basic computer software which provides management and control for computer resources, thus, the performance of the software running on an OS is depending on the OS architecture to a great extent.Exokemel differs from traditional kernel, the latter one achieves the protection and management of hardware resources in kernel mode, while Exokernel separates them. In an Exokernel, the kernel protects hardware resources and unprivileged users manage them. Exokernel presents as few hardware abstractions as possible to programmers, therefore they could customize the library operating system to access hardware resources, thus both improves the flexibility and performance of the implementations, and simplifies the kernel itself.The main topic in this thesis is an exokernel-like OS, JOS, focusing on its architecture, which includes system booting, process management, memory management and IPC.The main contribution in this thesis is JOS’s scheduler. We have designed and implemented JOS’s scheduler based on Multiple Level Feedback Queue (MLFQ). By adding process-priority-policy and period-scheduling-policy into ordinary MLFQ, JOS’s scheduler has a high performance in short-job-interaction and avoids starvation efficiently. To improve the safety and reliability of JOS’s scheduler, a formal model has been built using finite state automata and the SPIN model checker. Finally, we test the scheduler by compared with RR to indicate it has a better performance than RR, a test on period-scheduling-policy also has been done to prove its starvation avoidance.