LINUX System : Lecture 7 Lecture notes acknowledgement : The design of UNIX Operating System

Architecture of the UNIX user programs libraries user Level kernel Level system call interface file subsystem process control subsystem inter-process communication scheduler memory management buffer cache 좌측에 파일서브시스템과 우측에 프로세스 서브시스템이 가장 핵심되는 축이 된다. 3종류의 레벨로 나뉘어져 있다 – user level, kernel level, hardware level device drivers character block hardware control kernel Level hardware Level hardware

System calls & Libraries user programs libraries trap user Level kernel Level system call interface system call interface file subsystem process control subsystem inter-process communication scheduler memory management buffer cache device drivers character block hardware control kernel Level hardware Level hardware

System calls & Libraries System call library OS service in the form of C function call Standard library, User library Linked with the programs at compile time and are part of the user program

File Subsystem (1) process control libraries system call interface user programs libraries trap user Level kernel Level system call interface file subsystem process control subsystem inter-process communication scheduler memory management buffer cache device drivers character block hardware control kernel Level hardware Level hardware

File Subsystem (2) Managing files and structures of file system Allocating file space Administering free space Controlling access to files Retrieving data for users Interact with set of system calls open, close, read, write, state, chown, chmod …

Buffering Mechanism (1) user programs libraries trap user Level kernel Level system call interface file subsystem process control subsystem inter-process communication scheduler memory management buffer cache device drivers character block hardware control kernel Level hardware Level hardware

Buffering Mechanism (2) Interact with block I/O device drivers to initiate data transfer to and from kernel.

Process Control Subsystem (1) user programs libraries trap user Level kernel Level system call interface file subsystem process control subsystem inter-process communication scheduler memory management buffer cache device drivers character block hardware control kernel Level hardware Level hardware

Process Control Subsystem (2) Managing process structures (proc table, u table,…) Process scheduling Interprocess communication (IPC) Memory management Responsible for process synchronization. Communicate with file subsystem Loading a file into memory for execution Interact with set of system calls fork, exec, exit, wait, brk, signal … 파일시스템과 프로세스 컨트롤 시스템간의 서로 연계되는 때는 프로그램 실행을 위해서 메모리에 프로그램을 로딩할 때이다.

Process Control Subsystem (3) Memory management module Control the allocation of memory to a process Scheduler module Allocate the CPU to processes Interprocess communication There are several forms.

Hardware Control (1) process control libraries system call interface user programs libraries trap user Level kernel Level system call interface file subsystem process control subsystem inter-process communication scheduler memory management buffer cache device drivers character block hardware control kernel Level hardware Level hardware

Hardware Control (2) Responsible for handling interrupts and for communicating with the machine. Devices such as disks or terminals may interrupt the CPU while a process is executing

Topics to be covered File subsystem Process control subsystem (Memory Management) Signal IPC (Inter-Process Communication), Synchronization UNIX System Programming (System Calls)

Reference Books The design of the UNIX Operating System, M. J. Bach Advanced Programming in the Unix Environment, 2nd Edition, W. R. Stevens, S. A. Rago