poject manajment

Chapter 4:
Threads

Ch4: Threads

CPIS 222– Principles of Operating Systems -2012– KAU

Dr.Lamiaa Elrefaei

1

Outline
 Overview

 Multithreading Models
 Thread Libraries
 Threading Issues

 Operating System Examples

Ch4: Threads

CPIS 222– Principles of Operating Systems -2012– KAU

Dr.Lamiaa Elrefaei

2

4.1 Overview
 Single-threaded process – multithreaded process:


A thread is a basic unit of CPU utilization.



Traditional process has a single thread of control.



Multithreaded process can perform more than one task at a time.

 Many applications are multithreaded.


A web browser might have one thread displaying images while another thread retrieving data from the network.



A word processor may have a thread for responding to keystrokes from the users, and another thread for performing spelling and grammar checking in the background.  Many operating system kernels are now multithreaded.
 Several threads operate in the kernel.
 Each thread performs a specific task.
 For example, Linux uses a kernel thread for managing the amount of free memory in the system.
Ch4: Threads

CPIS 222– Principles of Operating Systems -2012– KAU

Dr.Lamiaa Elrefaei

3

4.1 Overview (cont’d)
 A thread comprises:


A thread ID.



A program counter.



A register set.



A stack.

 It shares with other threads belonging to the same process:


Code section.



Data section.



Other operating-system resources, such as open files.

Ch4: Threads

CPIS 222– Principles of Operating Systems -2012– KAU

Dr.Lamiaa Elrefaei

4

4.1 Overview (cont’d)
Heavyweight Process= process

Ch4: Threads

Lightweight Process = Thread

CPIS 222– Principles of Operating Systems -2012– KAU

Dr.Lamiaa Elrefaei

5

New Process Description Model

Single-threaded process

multithreaded process
Ch4: Threads

CPIS 222– Principles of Operating Systems