Operating System - Threads

Threads

A thread (or lightweight process) is a basic unit of CPU utilization; it consists of:
program counter
register set
stack space
A thread shares with its peer threads its:
code section
data section
operating-system resources
collectively know as a task.
A traditional or heavyweight process is equal to a task with one thread

Example:Several Threads in Word Processor
1- Interactive thread.
2- Formatting thread in background.
3- Auto-saving thread in background.


In a multiple threaded task, while one server thread is blocked and waiting, a second thread in the same task can run.
Cooperation of multiple threads in same job confers higher throughput and improved performance.
Applications that require sharing a common buffer (i.e., producer-consumer) benefit from thread utilization.
Threads provide a mechanism that allows sequential processes to make blocking system calls while also achieving parallelism.
Kernel-supported threads (Mach and OS/2).
User-level threads; supported above the kernel, via a set of library calls at the user level.
Hybrid approach implements both user-level and kernel-supported threads (Solaris 2).