Multi threading models
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Multithreading allows an operating system to execute multiple tasks simultaneously by using threads. It improves responsiveness, enables resource sharing, and improves scalability. There are three main multithreading models: many-to-one maps many user threads to a single kernel thread; one-to-one uses a one-to-one mapping; many-to-many multiplexes user threads to kernel threads, combining advantages of the other models.
Multi threading models
- 1. ADVANCE OPERATING SYSTEM Darakhshan Nayab MSc(IT) MS(Computer Science) Dept of Computer Science
- 2. Content ■ Multi-threading ■ Example ■ Architecture ■ RPC ■ Advantages ■ Multi-threading models
- 3. Multi-threading ■ Multithreading allows operating system to execute different threads simultaneously. ■ It perform multiple tasks at the same time.
- 4. Example ■ Many software packages that run on modern desktop PCs are multithreaded. A word processor may have: ■ A thread for displaying graphics, another thread for responding to keystrokes from the user, and a third thread for performing spelling and grammar checking in the background. ■ A Web Browser can use one thread to display images and a second thread to retrieve data from the network.
- 5. Architecture ■ A web server receives requests for web pages, images and sounds etc. Many client may be accessing the server at the same time. The web server can service only one client at a time if it runs as a single- threaded process. The clients may have to wait for the service of the requests.
- 6. RPC RPC is a protocol in which one program can be used to send the service to the program located in another server in a network without having the network detail.
- 7. Advantages ■ Responsiveness ■ Resource sharing ■ Economy ■ Scalability ■ Context Switching is smooth
- 8. Multi-Threading Models ■ The user threads must be mapped to kernel threads, by one of the following strategies: ■ Many to One Model ■ One to One Model ■ Many to Many Model
- 9. One to One Model ■ One to One model creates a separate kernel thread to handle each and every user thread. ■ Most implementations of this model place a limit on how many threads can be created. ■ This model provides more concurrency, Efficient performance. Example ■ Linux ■ Window XP
- 10. Many to One ■ In the many to one model, many user-level threads are all mapped onto a single kernel thread. ■ Thread management done in user space. ■ If a thread makes a blocking calls entire process is blocked. ■ Only one thread can access the kernel at a time, So it cannot run in parallel on multiprocessor.
- 11. Many to Many ■ Multiplexes any number of user threads onto an equal or smaller number of kernel threads, combining the best features of the one-to- one and many-to-one models. ■ Users can create any number of threads. ■ Blocking the kernel system calls does not block the entire process. ■ Processes can be split across multiple processors.