15 threads
- 1. Understand Process Management • Threads 1
- 2. HOME PREVIOUS TOPIC NEXT PREVIOUS QUESTION PAPERS FOR OS CPP TUTORIALS 2
- 3. Recap In the last class, you have learnt • Relationship between Processes • Reasons for providing an environment that allows Process cooperation 3
- 4. Objectives On completion of this class, you would be able to know • Definition of Thread • Benefits of Multithread programming • Multithreading Models 4
- 5. Thread Structure • A thread is a light weight process (LWP) • Basic unit of CPU utilization • Shares other threads belonging to the same process its code section, data section and other resources • Threads created for a particular process are known as sibling threads 5
- 6. Thread Structure Thread comprises of • Thread id • Program counter • Register counter • Register set • Stack 6
- 7. Thread Structure • Process having multiple threads of control, can perform more than one task at a time • Threads operate, in many respects, in the same manner as processes • Like processes threads can share CPU, but only one thread at a time is active • Thread can create child threads • Threads are not independent of one another • This structure does not provide protection between threads as they can read or write over any other thread 7
- 8. Thread States Thread states • New • Ready • Blocked • Running • Terminated 8
- 9. Threads Single threaded process • A traditional (or heavy weight) Process that has a single thread of control Multi threaded process • A process which has several threads of control • It can do more than one task at a time 9
- 10. Single and Multi Thread Process Thread Single Thread Process Multi Thread Process Fig.1 10
- 11. Benefits of Multithreading Programming Responsiveness • Allows a program to continue even if a part of it is blocked or performing a lengthy operation Resource sharing • Threads share the memory and the resources of the process to which they belong • Allows an application to have several different threads of activity within the same address space 11
- 12. Benefits of Multithreading Programming Economy • Threads share resources of the process to which they belong • Hence it is more economical to create and conduct switch threads 12
- 13. Benefits of Multithreading Programming Utilization of multiprocessor architectures • Benefits of multithreading can be greatly increased in a multiprocessor architecture where threads may be running in parallel on different processors • Multithreading increases concurrency on a multi- CPU machine 13
- 14. Multi Threading Model • An operating system support multiple threads of execution in one process • Support for threads may be provided at either the user level or by the kernel • User threads are supported above the kernel and are managed without kernel support • Kernel threads are supported and managed directly by operating system • Windows XP. Solaris, True64 UNIX - support kernel threads 14
- 15. One process one thread One process multiple thread Fig.1 (a) Fig.2 (b) Multiple process, one thread per process Multiple process, multiple threads per process Fig.3 (c) Fig.4 (d) Fig: multithreading model 15
- 16. Multithreading Models Many-to-one Model • Maps many user-level threads to one kernel thread • Green threads-a thread library available for Solaris users this model Fig.2 16
- 17. Multithreading Models One-to-One Model • Maps each user thread to a kernel thread • Windows 95/98/NT/2000/XP implement the one-to-one model User thread Kernel thread Fig.3 17
- 18. Multithreading Models Many-to-Many Model • Multiplexes many user level threads to a smaller or equal number of kernel threads. User thread Kernel thread Fig.4 18
- 19. Summary In this class, you have learnt • A thread is a basic unit of CPU utilization • A thread is a light weight process • A thread shares with peer threads its code section data section and other resources • Extensive sharing makes CPU switching among peer threads and thread creation inexpensive 19
- 20. Frequently Asked Questions 1. Write short notes on threads 2. Explain the different multithreading models 20
- 21. Other subject materials • Web designing • Micro processors • C++ tutorials • java home
- 22. Quiz State whether the following statements are true or false 1. Thread is a light weight process a) True b) False 2. Threads can communicate with each other a) True b) False 3. A thread needs __________________ Less no. of resources 4. A single process _____________________ Supports multiple threads 22