Chapter 4: Threads
Operating System Concepts – 9th Edition Silberschatz, Galvin and Gagne
Chapter 4: Threads
Operating System Concepts – 9th Edition 4.2 Silberschatz, Galvin and Gagne
Understanding Threads
Threads, also known as lightweight processes, are
independent sequences of execution within a process.
Unlike traditional processes, threads share the same
memory space and resources within a process context,
allowing for faster communication and synchronization.
Threads can execute concurrently, providing advantages
such as improved responsiveness and better utilization of
multiprocessor systems.
Operating System Concepts – 9th Edition 4.3 Silberschatz, Galvin and Gagne
Thread Creation and Management
The operating system provides mechanisms for creating,
managing, and scheduling threads within a process.
Thread creation involves allocating resources and initializing
thread-specific data structures.
Thread management tasks include scheduling threads for
execution, handling thread states (such as running, ready,
blocked), and managing thread termination.
Operating systems typically offer APIs or libraries for thread
management, providing developers with the necessary tools
to create and control threads effectively.
Operating System Concepts – 9th Edition 4.4 Silberschatz, Galvin and Gagne
Motivation
Most modern applications are multithreaded
Threads run within 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
Operating System Concepts – 9th Edition 4.5 Silberschatz, Galvin and Gagne
Multithreaded Server Architecture
Operating System Concepts – 9th Edition 4.6 Silberschatz, Galvin and Gagne
Benefits
Responsiveness – may allow continued execution if
part of process is blocked, especially important for
user interfaces
Resource Sharing – threads share resources of
process, easier than shared memory or message
passing
Economy – cheaper than process creation, thread
switching lower overhead than context switching
Scalability – process can take advantage of
multiprocessor architectures
Operating System Concepts – 9th Edition 4.7 Silberschatz, Galvin and Gagne
Continue…
Multithreading offers various benefits, including improved
responsiveness, enhanced throughput, better resource
utilization, and increased scalability.
By allowing concurrent execution of multiple tasks,
multithreading enables applications to better utilize modern
multicore processors and exploit parallelism.
Multithreading is widely used in diverse domains, including
operating systems, database systems, web servers, and
multimedia applications, to achieve better performance and
responsiveness.
Operating System Concepts – 9th Edition 4.8 Silberschatz, Galvin and Gagne
Single and Multithreaded Processes
Operating System Concepts – 9th Edition 4.9 Silberschatz, Galvin and Gagne
Concurrency vs. Parallelism
Concurrent execution on single-core system:
Parallelism on a multi-core system:
Operating System Concepts – 9th Edition 4.10 Silberschatz, Galvin and Gagne
User Threads and Kernel Threads
User threads - management done by user-level threads library
Three primary thread libraries:
POSIX Pthreads
Windows threads
Java threads
Kernel threads - Supported by the Kernel
Examples – virtually all general purpose operating systems,
including:
Windows
Solaris
Linux
Tru64 UNIX
Mac OS X
Operating System Concepts – 9th Edition 4.11 Silberschatz, Galvin and Gagne
Multithreading Models
Many-to-One
One-to-One
Many-to-Many
Operating System Concepts – 9th Edition 4.12 Silberschatz, Galvin and Gagne
Many-to-One
Many user-level threads mapped
to single kernel thread
One thread blocking causes all
to block
Multiple threads may not run in
parallel on muticore system
because only one may be in
kernel at a time
Few systems currently use this
model
Examples:
Solaris Green Threads
GNU Portable Threads
Operating System Concepts – 9th Edition 4.13 Silberschatz, Galvin and Gagne
One-to-One
Each user-level thread maps to kernel
thread
Creating a user-level thread creates a
kernel thread
More concurrency than many-to-one
Number of threads per process
sometimes restricted due to overhead
Examples
Windows
Linux
Solaris 9 and later
Operating System Concepts – 9th Edition 4.14 Silberschatz, Galvin and Gagne
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 with the ThreadFiber
package
Operating System Concepts – 9th Edition 4.15 Silberschatz, Galvin and Gagne
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 – 9th Edition 4.16 Silberschatz, Galvin and Gagne
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 – 9th Edition 4.17 Silberschatz, Galvin and Gagne
END
Operating System Concepts – 9th Edition 4.18 Silberschatz, Galvin and Gagne
