Implementation of processes in minix3

Organization of minix3 source code

Full path to C Language source code on standard intel based platform is "/usr/src/"

Makefile controls the compilation of files in its directory and also directs compilation of files in one or more subdirectories. Make manages efficient compilation of programs involving multiple source files. It also tests previously compiled modules to see if they are up to date and re-compiles whose source files have been modified.

All part of "/src/" tree can be relocated since makefile in each directory uses a relative path to C directories.

During compilation every makefile expects to find header files in "/usr/include". "/usr/src/tools/Makefile" expects to find master copy of header files in "/usr/src/include". Before recompiling the system, the entire "/usr/include" directory is deleted and "/usr/src/include" is copied to "/usr/include". This is done to keep all files needed in development of minix3 in one place.

include/ contains a number of posix standard files. Following are the subdirectories of include/:

• sys/ - Additional posix header.
• minix/ - Header files used by MINIX3 operating system.
• ibm/ - Header files with ibm-pc specific definitions
• arpa/ and net/ - Support network extensions. Not necessary for compiling basic MINIX3 system.

src/ directory also contains following subdirectories:

• kernel/ - Layer1 (Scheduling, messages, clock and system tasks)
• drivers/ - Layer2 (Device driver for disk, console printer etc)
• servers/ - Layer3 (process manager, file system and other servers)
• lib/ - Source code for library procedures (open, read etc)
• tools/ - Makefile and scripts for building MINIX3 system.
• boot/ - Code for booting and installing MINIX3

/src/servers contains following subdirectories:

• pm/ - Process manager
• mfs/ - Main file system
• Init Program
• rs/ - Reincarnation Server
• inet/ - Network server source code

src/test/ - is used to test a newly compiled MINIX3 System.

src/command/ - contains source code for programs like cat, cp, date, ls, pwd etc.

src/kernel/const.h - Defines the constants used in the Kernel

src/servers/pm/const.h - Defines constants used by process manager

Memory layout after MINIX3 has been loaded from disk into memory

The kernel, drivers and servers are independently compiled and linked programs as listed on the left in following image.

Minix 3 consists of totally independent programs that communicate only by message passing. The procedures that the three pieces of os have in common are in /src/lib. The modular structure helps in making changes in any part of the operating system without having to make change in any other part.

A detailed explanation about implementation of process manager is given in the book "Operating system design and Implementation", Section - 2.

Reference:

Operating System Design and Implementation, Third Edition By Andrew S. Tanenbaum and Albert S. Woodhull