Prerequisite – Operating-System-Thread
The benefits of multi threaded programming can be broken down into four major categories:
- Responsiveness –
Multithreading in an interactive application may allow a program to continue running even if a part of it is blocked or is performing a lengthy operation, thereby increasing responsiveness to the user.
In a non multi threaded environment, a server listens to the port for some request and when the request comes, it processes the request and then resume listening to another request. The time taken while processing of request makes other users wait unnecessarily. Instead a better approach would be to pass the request to a worker thread and continue listening to port.
For example, a multi threaded web browser allow user interaction in one thread while an video is being loaded in another thread. So instead of waiting for the whole web-page to load the user can continue viewing some portion of the web-page.
- Resource Sharing –
Processes may share resources only through techniques such as-
- Message Passing
- Shared Memory
Such techniques must be explicitly organized by programmer. However, threads share the memory and the resources of the process to which they belong by default.
The benefit of sharing code and data is that it allows an application to have several threads of activity within same address space.
- Economy –
Allocating memory and resources for process creation is a costly job in terms of time and space.
Since, threads share memory with the process it belongs, it is more economical to create and context switch threads. Generally much more time is consumed in creating and managing processes than in threads.
In Solaris, for example, creating process is 30 times slower than creating threads and context switching is 5 times slower.
- Scalability –
The benefits of multi-programming greatly increase in case of multiprocessor architecture, where threads may be running parallel on multiple processors. If there is only one thread then it is not possible to divide the processes into smaller tasks that different processors can perform.
Single threaded process can run only on one processor regardless of how many processors are available.
Multi-threading on a multiple CPU machine increases parallelism.
References- Operating System concepts by Abraham Silberschatz, Peter B. Galvin& Greg Gagne
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