Threads

Threads

•          A thread is some times called as a light weight processes, is a basic unit of CPU utilization.

Thread is made up of:

ü  Thread_id

ü  Program counter

ü  Register set

ü  Stack

Thread share :

ü  Code section

ü  Data section

ü  Other OS resources

ü  A traditional process has a single thread of control.

ü  The idea behind threading is more finer control on CPU utilization.

ü  Eg. Web browser might have one thread for displaying pages, one thread for displaying text, another thread for receiving data from the network.

ü  A word processor program can have one thread for displaying graphics, one threads for reading e-strokes, another thread for checking spelling & grammar.

ü  A single application maybe required to perform several similar task.

•          Benefits of threading:

ü  Responsivness: Multi-threading & interactive

                application may allow a program to continue running even if some parts of it are block or is performing some lengthy operation.

ü  Resource sharing-By default threads share memory and the resources of the process to which-they belong.

ü  Economy: Allocating memory resources for process creation is costly. Alternatively,because thread share resources of the process to which they belong, it is more economical to create and context switch threads.

ü  Utilization of multi-process and architectures:

    The benefits of multi-threading can be greatly increased in a multi-process architecture,where each thread can execute in parallel an a different processor.

•          User threads: User level threads are generally fast to create & manage .But at the same time they have their drawbacks also.

•          Kernel threads: They are directly supported by the OS.

•          Kernel Performs:

ü  Thread creation

ü  Scheduling

ü  Management

•          Its all done by operating systems.

Multi-Threading Models:

1. Many-to-One:

User Thread

2. One-to-one:

Kernel Thread

3.Many-to-many: