操作系统英文教学课件：Chapter 4 Threads

1、4.2Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nOverviewnMultithreading ModelsnThreading IssuesnPthreads4.3Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nA thread is a basic unit of CPU utilization;lit comprises a thre

2、ad ID, a program counter, a register set，and a stack.lIt shares with other threads belonging to the same process： the code section, the data section, and other OS resources，such as open files, signals, etcnA traditional process has a single thread of control: lheavyweight process.4.4Silberschatz, Ga

3、lvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 20054.5Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nOn modern desktop PC, many APPs are multithreaded.la seperate process with several threadslExample 1: A web browser4one for displaying image

4、s or text;4another for retrieving data from networklExample 2: A word processor4one for displaying graphics;4another for responding to keystrokes from the user;4and a third for performing spelling & grammer checking in the background4.6Silberschatz, Galvin and Gagne 2005Operating System Concepts

5、 7th edition, Jan 23, 2005nIn certain situations, a single application may be required to perform several similar tasks. Example: a web servernAllow a server to service several concurrent requests. Example: an RPC servernThe OS itself needs to perform some specific tasks in kernel, such as managing

6、devices or interrupt handling.lPARTICULAR, many OS systems are now multithreaded.lExample: Solaris, Linux4.7Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nResponsivenesslExample: an interactive application such as web browser. while one thread loading an image

7、, another thread allowing user interactionnResource Sharinglmemory, and other resourcesnEconomy (e.g. save memory) lSolaris:creating a process is about 30 times slower then creating a thread;context switching is about 5 times slowernUtilization of MP Architectureslparallelism and concurrency 4.8Silb

8、erschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nTwo methods to support threadslUser threads VS. Kernel threadsnUser ThreadslThread management done by user-level threads library without kernel supportnKernel threadslSupported by the Kernel， usually may be slower the

9、n user threadlExamples4Windows XP/20004Solaris4Linux4Tru64 UNIX4Mac OS X4.9Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nThe relationship between user threads and kernel threadslMany-to-OnelOne-to-OnelMany-to-Many4.10Silberschatz, Galvin and Gagne 2005Operati

10、ng System Concepts 7th edition, Jan 23, 2005nMany user-level threads mapped to single kernel threadnExamples:lSolaris Green ThreadslGNU Portable Threads4.11Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 20054.12Silberschatz, Galvin and Gagne 2005Operating System Co

11、ncepts 7th edition, Jan 23, 2005nEach user-level thread maps to kernel threadnExampleslWindows NT/XP/2000lLinuxlSolaris 9 and later4.13Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 20054.14Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, J

12、an 23, 2005nAllows many user level threads to be mapped to many kernel threadsnAllows the operating system to create a sufficient number of kernel threadsnSolaris prior to version 9nWindows NT/2000 with the ThreadFiber package4.15Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th editi

13、on, Jan 23, 20054.16Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nSimilar to M:M, except that it allows a user thread to be bound to kernel threadnExampleslIRIXlHP-UXlTru64 UNIXlSolaris 8 and earlier4.17Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 20054.18Silberschatz, Galvin and Gagne 2005Operating System Concepts 7th edition, Jan 23, 2005nA thread library provides an API for creating and managing threads.nTwo primary ways