Chapter 4: Threads
Operating System Concepts – 8th Edition Silberschatz, Galvin and Gagne ©2009
Thread
A lightweight process
A flow of execution through the process code
It comprises a thread ID, a PC, a register set, a stack
Shares code section, data section, other OS resources
Operating System Concepts – 8th Edition 4.2 Silberschatz, Galvin and Gagne ©2009
Single and Multithreaded Processes
Operating System Concepts – 8th Edition 4.3 Silberschatz, Galvin and Gagne ©2009
Motivation
Threads run within an application
Multiple tasks with the application can be implemented by
separate threads
Update display
Fetch data
Spell checking
Answer a network request
Process creation is heavy-weight while thread creation is light-
weight
Can simplify code, increase efficiency
Kernels are generally multithreaded
Operating System Concepts – 8th Edition 4.4 Silberschatz, Galvin and Gagne ©2009
Benefits
Responsiveness
Resource Sharing
Economy
Scalability
Operating System Concepts – 8th Edition 4.5 Silberschatz, Galvin and Gagne ©2009
Multicore Programming
Multicore systems putting pressure on programmers -
Challenges include:
Dividing activities
Balance
Data splitting
Data dependency
Testing and debugging
Operating System Concepts – 8th Edition 4.6 Silberschatz, Galvin and Gagne ©2009
Concurrent Execution on a
Single-core System
Operating System Concepts – 8th Edition 4.7 Silberschatz, Galvin and Gagne ©2009
Parallel Execution on a
Multicore System
Operating System Concepts – 8th Edition 4.8 Silberschatz, Galvin and Gagne ©2009
User Threads
Thread management done by user-level threads library
Three primary thread libraries:
POSIX Pthreads
Win32 threads
Java threads
Operating System Concepts – 8th Edition 4.9 Silberschatz, Galvin and Gagne ©2009
Kernel Threads
Supported by the Kernel
Examples
Windows XP/2000
Solaris
Linux
Tru64 UNIX
Mac OS X
Operating System Concepts – 8th Edition 4.10 Silberschatz, Galvin and Gagne ©2009
Multithreading Models
Many-to-One
One-to-One
Many-to-Many
Operating System Concepts – 8th Edition 4.11 Silberschatz, Galvin and Gagne ©2009
Many-to-One
Many user-level threads mapped to single kernel thread
Examples:
Solaris Green Threads
GNU Portable Threads
Operating System Concepts – 8th Edition 4.12 Silberschatz, Galvin and Gagne ©2009
Many-to-One Model
Operating System Concepts – 8th Edition 4.13 Silberschatz, Galvin and Gagne ©2009
One-to-One
Each user-level thread maps to kernel thread
Examples
Windows NT/XP/2000
Linux
Solaris 9 and later
Operating System Concepts – 8th Edition 4.14 Silberschatz, Galvin and Gagne ©2009
One-to-one Model
Operating System Concepts – 8th Edition 4.15 Silberschatz, Galvin and Gagne ©2009
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
Operating System Concepts – 8th Edition 4.16 Silberschatz, Galvin and Gagne ©2009
Many-to-Many Model
Operating System Concepts – 8th Edition 4.17 Silberschatz, Galvin and Gagne ©2009
Two-level Model
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
Operating System Concepts – 8th Edition 4.18 Silberschatz, Galvin and Gagne ©2009
Two-level Model
Operating System Concepts – 8th Edition 4.19 Silberschatz, Galvin and Gagne ©2009
Thread Libraries
Thread library provides programmer with API for creating
and managing threads
Two primary ways of implementing
Library entirely in user space
Kernel-level library supported by the OS
Operating System Concepts – 8th Edition 4.20 Silberschatz, Galvin and Gagne ©2009
Pthreads
May be provided either as user-level or kernel-level
A POSIX standard (IEEE 1003.1c) API for thread creation
and synchronization
API specifies behavior of the thread library, implementation
is up to development of the library
Common in UNIX operating systems (Solaris, Linux, Mac
OS X)
Operating System Concepts – 8th Edition 4.21 Silberschatz, Galvin and Gagne ©2009
Pthreads Example
Operating System Concepts – 8th Edition 4.22 Silberschatz, Galvin and Gagne ©2009
Pthreads Example (Cont.)
Operating System Concepts – 8th Edition 4.23 Silberschatz, Galvin and Gagne ©2009
End of Chapter 4
Operating System Concepts – 8th Edition Silberschatz, Galvin and Gagne ©2009
