Outline. Operating Systems Design and Implementation. Chap 1 - Overview. What is an OS? 28/10/2014. Introduction

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Operating Systems

Operating Systems - Winter 2012

Andrew S. Tanenbaum

Melanie Rieback

Arno Bakker

Design and Implementation

Vrije Universiteit Amsterdam

Outline

Vrije Universiteit Amsterdam Slide 4

• Introduction

• What is an OS?

• Concepts

• Processes and Threads

• Memory Management

• File Systems

Operating Systems 2012

Chap 1 - Overview

• What is an Operating System?

• Concepts

• System Calls

• Structure

What is an OS?

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2 Views on OSes

• OS as a Virtual Machine

• Extending the HW functionality

• Hides the messy details of programming the HW

• OS as a Resource Manager

• Protects against simultaneous usage of resources

• Fair sharing of resources (scheduling)

• Resource accounting

How to View an OS

OS

Program

System calls

Concept: Processes

Multiple Processes

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System Calls

Hardware

Operating System

System Calls

Libraries

Library functions

Applications / Processes

Instruction Set Architecture

•System Callsare the interface the Operating System offers to applications.

•Problem:Mechanics of issuing a system call are highly machine dependent

•Solution:Provide a library to allow system calls from C programs: libc

Bash

libc

Linux kernel

x86_64

System Calls: Process

Management (1/2)

System Calls: Process

Management (2/2)

System Calls: Signals

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Concept: Mounting (1/2)

File System Mounting (2/2)

Special Files (1/2)

Storage devices are mapped into the file tree via mounting. Idea: do this for all devices.

Mechanism: Special files in /dev

Two types:

Special Files (2/2)

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System Calls: Files

System Calls: Directories

System Calls: Implementation

OS Structure: UNIX

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OS Structure: Linux

Operating Systems

Operating Systems - Winter 2012

Chapter 2 - Processes

Vrije Universiteit Amsterdam

Chap 2 - Overview

Operating Systems 2012

• Scheduling Processes

• Threads

Recall: Process

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One CPU, Many Processes

Vrije Universiteit Amsterdam Slide 3

• Processes share the CPU(s)

• A

scheduler

determines which process to run next

• Keeps track of the

process state

• Following some

scheduling policy

(random robin, shortest

job first, etc).

Process States

Context Switching

Process Implementation

Process

Table:

ps -ef

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Threads

Threads: Minimal Support

Threads – Some Problems

Mutual Exclusion

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Operating Systems

Chapter 4 – Memory Management

Chap 4 - Overview

• Memory Management

• Paged Memory

• Virtual Memory

• Segmentation

Memory Management – Simple

Memory Management - Complex

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Paged Memory Systems (1/2)

Paged Memory Systems (2/2)

Virtual Memory

• Idea

: Not all virtual pages have to be in physical memory

• Instead stored on

disk

-> cheap storage

• In

swap

partition

• Much more memory available

• Works if not all pages are used at the same time

Segmentation

Stack

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Operating Systems

Chapter 5 – File Systems

Chap 5 - Overview

• Files

• Directories

• File system implementation

• UNIX/MINIX filesystem

Directories

i-node

File Attributes

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Directories – Pathnames

File System Design

File Storage: Disk Layout

File Storage – Inodes

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File Storage – UNIX

File Storage – Name Resolution

Disk Space Management (1/2)

File System Consistency

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Buffer Cache

Log-Structured File Systems

MINIX Filesystem

MINIX Superblock