Implementation

Assume that we want to create an operating system using a multi-server approach, similar to how it is done in MINIX 3 [j.mp/minix3] or GNU Hurd [j.mp/gnuhurd]. A multi-server operating system has a minimal kernel, called the microkernel, that runs in privileged mode. All the other services of the system are following a server architecture (driver server, process server, file server, and so forth). Each server belongs to a different memory address space and runs on top of the microkernel in user mode. The pros of this approach are that the operating system can become more fault-tolerant, reliable, and secure. For example, since all drivers are running in user mode on a driver server, a bug in a driver cannot crash the whole system, and neither can it affect the other servers. The cons of this approach are the performance overhead and the complexity of system programming, because the communication between a server and the microkernel, as well as between the independent servers...