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A process with two threads of execution, running on one processor Program vs. Process vs. Thread Scheduling, Preemption, Context Switching. In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. [1]
In computing, a process is the instance of a computer program that is being executed by one or many threads. There are many different process models, some of which are light weight, but almost all processes (even entire virtual machines) are rooted in an operating system (OS) process which comprises the program code, assigned system resources ...
Thread scheduling is also a major problem in multithreading. Merging data from two processes can often incur significantly higher costs compared to processing the same data on a single thread, potentially by two or more orders of magnitude due to overheads such as inter-process communication and synchronization. [2] [3] [4]
The operating systems that run on these architectures make extensive use of this instruction to facilitate process (i.e., system and user tasks) and processor (i.e., central processors) parallelism while eliminating, to the greatest degree possible, the "disabled spinlocks" which had been employed in earlier IBM operating systems.
However, in a multitasking operating system, the operating system switches between processes or threads to allow the execution of multiple processes simultaneously. [2] For every switch, the operating system must save the state of the currently running process, followed by loading the next process state, which will run on the CPU.
The article "Usage share of operating systems" provides a broader, and more general, comparison of operating systems that includes servers, mainframes and supercomputers. Because of the large number and variety of available Linux distributions , they are all grouped under a single entry; see comparison of Linux distributions for a detailed ...
In many modern operating systems, processes can consist of many sub-processes. This introduces the concept of a thread . A thread may be viewed as a sub-process ; that is, a separate, independent sequence of execution within the code of one process.
Task parallelism emphasizes the distributed (parallelized) nature of the processing (i.e. threads), as opposed to the data (data parallelism). Most real programs fall somewhere on a continuum between task parallelism and data parallelism. [3] Thread-level parallelism (TLP) is the parallelism inherent in an application that runs multiple threads ...