Multithreading

Multithreading is the ability of a program or an operating system process to manage its use by more than one user at a time and to even manage multiple requests by the same user without having to have multiple copies of the programming running in the computer. Central processing units have hardware support to efficiently execute multiple threads. These are distinguished from multiprocessing systems (such as multi-core systems) in that the threads have to share the resources of a single core: the computing units, the CPU caches and the translation lookaside buffer (TLB). Where multiprocessing systems include multiple complete processing units, multithreading aims to increase utilization of a single core by using thread-level as well as instruction-level parallelism. As the two techniques are complementary, they are sometimes combined in systems with multiple multithreading CPUs and in CPUs with multiple multithreading cores.

Single Core: In the case of a computer with a single CPU core, only one task runs at any point in time, meaning that the CPU is actively executing instructions for that task. Multitasking solves this problem by scheduling which task may run at any given time and when another waiting task gets a turn.

Multicore: When running on a multicore system, multitasking OSs can truly execute multiple tasks concurrently. The multiple computing engines work independently on different tasks.

For example, on a dual-core system, four applications - such as word processing, e-mail, Web browsing, and antivirus software - can each access a separate processor core at the same time. You can multitask by checking e-mail and typing a letter simultaneously, thus improving overall performance for applications.

Multithreading

Multithreading extends the idea of multitasking into applications, so you can subdivide specific operations within a single application into individual threads. Each of the threads can run in parallel. The OS divides processing time not only among different applications, but also among each thread within an application.

In a multithreaded National Instruments LabVIEW program, an example application might be divided into four threads - a user interface thread, a data acquisition thread, network communication, and a logging thread. You can prioritize each of these so that they operate independently. Thus, in multithreaded applications, multiple tasks can progress in parallel with other applications that are running on the system.