1. Chapter 4: Multithreaded Programming

2. 4.2 Silberschatz, Galvin and Gagne ©2005 Operating System Principles Objectives To introduce a notion of a thread – a fundamental unit of CPU utilization that forms the basis of multithreaded computer systems To discuss the APIs for thread libraries (skip) To examine issues related to multithreaded programming (skip)

3. 4.3 Silberschatz, Galvin and Gagne ©2005 Operating System Principles Chapter 4: Multithreaded Programming Overview Multithreading Models Thread Library (skip) Threading Issues (skip) Linux Threads (skip)

4. 4.4 Silberschatz, Galvin and Gagne ©2005 Operating System Principles 4.1 Overview Single and Multithreaded Processes check Fig. 4.2 in p. 155

5. 4.5 Silberschatz, Galvin and Gagne ©2005 Operating System Principles Benefits Responsiveness: Allow an interactive program to continue running even if part of it is blocked or is performing a lengthy operation Resource Sharing Threads share the memory and the resources of the process Economy It is more economical to create and context-switch threads. For example, in Solaris, creating a process is 30 times slower than creating a thread, and context switching a process is 5 times slower than context switching a thread Scalability Utilization of Multiprocessor Architectures Threads may be running in parallel on different processors Skip 4.1.3

6. 4.6 Silberschatz, Galvin and Gagne ©2005 Operating System Principles 4.2 Multithreading Models How to establish the relationship between user and kernel threads Many-to-One One-to-One Many-to-Many User Threads Thread management done by user-level threads library Three primary thread libraries: POSIX Pthreads, Win32 threads, Java threads Kernel threads Supported by the kernel (operating system) Examples ： Windows XP/2000, Solaris, Linux, Tru64 UNIX, Mac OS X

7. 4.7 Silberschatz, Galvin and Gagne ©2005 Operating System Principles Many-to-One Many user-level threads mapped to single kernel thread Examples: Solaris Green Threads, GNU Portable Threads Thread management is done in user space, so it is efficient. If a thread makes a blocking system call, then the entire process will block

8. 4.8 Silberschatz, Galvin and Gagne ©2005 Operating System PrinciplesOne-to-One Each user-level thread maps to kernel thread Examples Windows NT/XP/2000, Linux, Solaris 9 and later Drawback: creating a user thread requires creating the corresponding kernel thread Restrict the number of threads supported by the system

9. 4.9 Silberschatz, Galvin and Gagne ©2005 Operating System Principles Many-to-Many Model Allows many user level threads to be mapped to many kernel threads Allows the operating system to create a sufficient number of kernel threads Examples: Solaris prior to version 9, Windows NT/2000 with the ThreadFiber package

10. 4.10 Silberschatz, Galvin and Gagne ©2005 Operating System Principles Two-level Model Similar to Many-to-Many, except that it allows a user thread to be bound to kernel thread Examples IRIX, HP-UX, Tru64 UNIX, Solaris 8 and earlier Skip 4.3 – 4.6