Research And Improvement Of A Micro-Kernel System MINIX3Disseetation

Micro-kernel is a concept which is different with Macro-kernel. With the rapiddeveloping of hardware, Operating System is becoming larger and larger. Besides somefundamental mechanism, such as interrupt, clock, scheduling and messaging, there are also alot of other services in Macro-kernel, including file system, memory management and variousof drivers, which are famous for poor security.There are huge gaps between Micro-kernel and Macro-kernel on architecture. There areonly some inevitable functions implemented in Micro-kernel. A lot of other services areimplemented as independent processes in user mode. These services together with theMicro-kernel serve as the previous Macro-kernel.The differences on architecture show impact on the communication mechanism. InMacro-kernel, services are all in the some address space, they can communicate with directfunction call, which is really efficient but vulnerable. In order to serve a user’s request,services in user mode have to cooperate in Micro-kernel systems. They communicate with themessage mechanism provided by micro-kernel, which is robust but slow.MINIX3is a micro-kernel system. Messaging is the fundamental communicationmechanism in MINIX3.Messaging has two characteristics. First is that it’s bound to fall intothe kernel when messaging no matter sending or receiving messages. Another is that there isno existing way to avoid message copying. However, falling into the kernel is necessary insome cases but sometimes it’s not, and the same with message copying. Re-designing themessage communication mechanism of MINIX3will improve system efficiency.1. Eliminating unnecessary context switchingEntering kernel mode or not in messaging is determined by whether scheduling isnecessary. Actually, scheduling is not necessary in some scenarios. Taking some memory areain the user mode address spaces of processes and then mapping some messaging-relatedstructures to it will definitely eliminate the unnecessary context switching. Messaging takes place among different types of processes. But some defects ofimplementing fast context switching messaging (FCSM) with all of these processes should beserious considered. Applying FCSM among system services will be enough.2. Zero-copingZero-coping of messages will be realized by making the best use of the sharing memoryarea, which contains a messages pool shared by all system services.