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Operating system: threads(mulithreading,benefits of threads, types of thread)
- 1. Prepared By:- Dhruvi Chapaneriya (150420116008) Palak Dixit (150420116013) Sonali Hiranandani (150420116021) Maitry Jariwala (150420116027) Branch:- B.E. INFORMATION TECHNOLOGY Semester:- 04 (2nd YEAR) Guided By:- Prof. Hiren Vavaiya Topic:Threads
- 2. THREADS• CONCEPT OF MULTITHREADS • BENEFITS OF THREADS • TYPES OF THREADS
- 3. Slide name Slide no. Definition of Threads 4 Diagram of Single and Multithreads 5 Concepts of Multithreads 6 Benefits of Threads 7 Types of Multithreading Models 8 One-To-One 9 Many-To-One 10 Many-To-Many 11 INDEX Note: Click on the slide name to directly land on to particular slide
- 4. DEFINITION OF THREADS • A thread is a basic unit of CPU utilization, consisting of a program counter, a stack, and a set of registers, ( and a thread ID. ) • Traditional ( heavyweight ) processes have a single thread of control - There is one program counter, and one sequence of instructions that can be carried out at any given time. • Threads are very useful in modern programming whenever a process has multiple tasks to perform independently of the others. • This is particularly true when one of the tasks may block, and it is desired to allow the other tasks to proceed without blocking.
- 5. Single and Multithreaded Processes
- 6. CONCEPTS OF MULTITHREADS • There are two types of threads exists • User level thread • Are supported above the kernel • Managed without kernel support • These are the threads that application programmers would put into their programs. • Kernel Thread • Supported directly by OS • All modern OSes support kernel level threads, allowing the kernel to perform multiple simultaneous tasks and/or to service multiple kernel system calls simultaneously. • Windows XP, Linux, Mac OS, Solaris, True64 Unix – support kernel thread • Furthermore, There must exist a relationship between user threads and kernel threads.
- 7. BENEFITS OF THREADS • There are four major categories of benefits to multi-threading: I. Responsiveness - One thread may provide rapid response while other threads are blocked or slowed down doing intensive calculations. II. Resource sharing - By default threads share common code, data, and other resources, which allows multiple tasks to be performed simultaneously in a single address space. III.Economy - Creating and managing threads ( and context switches between them ) is much faster than performing the same tasks for processes. IV.Scalability, i.e. Utilization of multiprocessor architectures - A single threaded process can only run on one CPU, no matter how many may be available, whereas the execution of a multi-threaded application may be split amongst available processors.
- 8. TYPES OF MULTITHREADING MODELS • One-to-One • Many-to-One • Many-to-Many
- 9. ONE-TO-ONE • The one-to-one model creates a separate kernel thread to handle each user thread. • One-to-one model overcomes the problems listed above involving blocking system calls and the splitting of processes across multiple CPUs. • However the overhead of managing the one- to-one model is more significant, involving more overhead and slowing down the system. • Most implementations of this model place a limit on how many threads can be created. • Linux and Windows from 95 to XP implement the one-to-one model for threads. Figure - One-to-one model
- 10. MANY-TO-ONE • In the many-to-one model, many user-level threads are all mapped onto a single kernel thread. • Thread management is handled by the thread library in user space, which is very efficient. • However, if a blocking system call is made, then the entire process blocks, even if the other user threads would otherwise be able to continue. • Because a single kernel thread can operate only on a single CPU, the many-to-one model does not allow individual processes to be split across multiple CPUs. • Green threads for Solaris and GNU Portable Threads implement the many-to-one model in the past, but few systems continue to do so today. Figure - Many-to-one model
- 11. MANY-TO-MANY • The many-to-many model 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 have no restrictions on the number of threads created. • Blocking kernel system calls do not block the entire process. • Processes can be split across multiple processors. • Individual processes may be allocated variable numbers of kernel threads, depending on the number of CPUs present and other factors. • One popular variation of the many-to-many model is the two-tier model, which allows either many-to-many or one- to-one operation. • IRIX, HP-UX, and Tru64 UNIX use the two-tier model, as did Solaris prior to Solaris 9. Figure - Many-to-many model