ManRiX
THE DESIGN OF ROBUST AND EFFICIENT MICROKERNEL

ManRiX is a microkernel based Operating System. Microkernel contains just few basic components of an Operating System. Those components that are not required inside the microkernel are implemented as user process. The components implemented inside microkernel are:

•  Thread manager:

•  IPC mechanism (using message passing).

•  Memory manager (caches and pagers are external processes).

•  Signals, timers. (To support POSIX semantics because user mode emulation of UNIX is very expensive as we have seen with Mach).

•  Exception and IRQ handling (redirection only).
• Kernel-preemption and SMP

You will notice that the code (implementation) is slightly heavier than expected. This is because we are trying to give POSIX interface. Emulation of POSIX semantics is quite expensive as we have seen with Mach Microkernel from Carnegie Mellon University .

In ManRix threads are the basic unit of execution. So the threads are scheduled independently. Process is an inactive entity. It encapsulates the threads and just gives an address space. A process with a single thread acts as a UNIX process. IPC is the heart of ManRix. Message Passing is the method of exchanging messages between threads. Message passing is the fastest way of Client Server communication in ManRix. The memory manager is based on Mach's VM design. POSIX Signals and Timers are implemented inside Microkernel. The Architecture dependent Exception and IRQ are handled inside microkernel. Only redirection is done inside microkernel. The ISR is implemented in User Process.

All other components are external processes. Some of them to mention are:

• C- Library (POSIX, ANSI support)
• File system manager
• Console manager
• Device driver (i.e. Bus manager, ATA manager, floppy etc)
• Network manager
• High availability manager
• X -windows

The FS subsystem is based on SVR4's VNODE/VFS architecture with few 4.4BSD style implementations. The Console server handles the terminals. The name space server provides the name space for IPC (message passing). Network Managet manages the TCP/IPC stack. High availability manager manages the fault diagnosis in the servers.