1. Chapter 4: Multithreaded Programming

2. Chapter 4: Threads Overview Multithreading Models Thread Libraries
Threading Issues
Operating System Examples
Windows XP Threads
Linux Threads

3. Objectives
To introduce the notion of a thread — a fundamental unit of CPU utilization that forms the basis of multithreaded computer systems
To discuss the APIs for the Pthreads, Win32, and Java thread libraries
To examine issues related to multithreaded programming

4. Single and Multithreaded Processes

5. Benefits
Responsiveness
Resource Sharing
Economy
Scalability

6. Multithreaded Server Architecture

7. Multicore Programming
Recent trand is to place multiple computing cores on a chip.
Multicore systems putting pressure on programmers, challenges include
Dividing computing activities for multicore
Balance
Data splitting
Data dependency
Testing and debugging are more difficult.

8. Concurrent Execution on a Single-core System

9. Parallel Execution on a Multicore System

10. User Threads
There are two kinds thread – 1) user thread, 2) kernel thread
Thread management done by user-level threads library
- Only CPU computation with own data.
Three primary thread libraries:
POSIX Pthreads – POSIX installed computer
Win32 threads – 32 bit Windows only
Java threads – run on any machine which is installed JVM.

11. Kernel Threads Supported by the Kernel
Can execute system services & access IO devices.
Examples
Windows XP/2000
Solaris
Linux
Tru64 UNIX
Mac OS X

12. Multithreading Models
User computations are done in user threads.
system call & IO are done in kernel threads.
User thread : Kernel thread ratio.
Many-to-One (One kernel thread is in charge of all system service)
One-to-One (1:1)
Many-to-Many (M:N)

13. Many-to-One Many user-level threads mapped to single kernel thread
Examples:
Solaris Green Threads
GNU Portable Threads

14. Many-to-One Model

15. One-to-One Each user-level thread maps to kernel thread Examples
Windows NT/XP/2000
Linux
Solaris 9 and later

16. One-to-one Model

17. 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
Solaris prior to version 9
Windows NT/2000 with the ThreadFiber package

18. Many-to-Many Model

19. Two-level Model (X)
Similar to M:M, except that it allows a user thread to be bound to kernel thread
Examples
IRIX
HP-UX
Tru64 UNIX
Solaris 8 and earlier

20. Two-level Model (X)

21. Java Threads Java threads are managed by the JVM
Typically implemented using the threads model provided by underlying OS
Java threads may be created by:
Extending Thread class
Implementing the Runnable interface

22. Windows XP Threads X Implements the one-to-one mapping, kernel-level
Each thread contains ( thread specific data )
A thread id
Register set
Separate user and kernel stacks
Private data storage area
The register set, stacks, and private storage area are known as the context of the threads
The primary data structures of a thread include: (X)
ETHREAD (executive thread block)
KTHREAD (kernel thread block)
TEB (thread environment block)

23. Linux Threads X Linux refers to them as tasks rather than threads
Thread creation is done through clone() system call
clone() allows a child task to share the address space of the parent task (process) – compare with fork()

24. End of Chapter 14