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Light-weight Process
In computer operating systems, a light-weight process (LWP) is a means of achieving multitasking. In the traditional meaning of the term, as used in Unix System V and Solaris, a LWP runs in user space on top of a single kernel thread and shares its address space and system resources with other LWPs within the same process. Multiple user-level threads, managed by a thread library, can be placed on top of one or many LWPs - allowing multitasking to be done at the user level, which can have some performance benefits. In some operating systems, there is no separate LWP layer between kernel threads and user threads. This means that user threads are implemented directly on top of kernel threads. In those contexts, the term "light-weight process" typically refers to kernel threads and the term "threads" can refer to user threads. On Linux, user threads are implemented by allowing certain processes to share resources, which sometimes leads to these processes to be called "light wei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, peripherals, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computerfrom cellular phones and video game consoles to web servers and supercomputers. , Android (operating system), Android is the most popular operating system with a 46% market share, followed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UNIX System V
Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, and 4. System V Release 4 (SVR4) was commercially the most successful version, being the result of an effort, marketed as ''Unix System Unification'', which solicited the collaboration of the major Unix vendors. It was the source of several common commercial Unix features. System V is sometimes abbreviated to SysV. , the AT&T-derived Unix market is divided between four System V variants: IBM's AIX, Hewlett Packard Enterprise's HP-UX and Oracle's Solaris, plus the free-software illumos forked from OpenSolaris. Overview Introduction System V was the successor to 1982's UNIX System III. While AT&T developed and sold hardware that ran System V, most customers ran a version from a reseller, based on AT&T's reference implementation. A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Futures And Promises
In computer science, futures, promises, delays, and deferreds are constructs used for synchronization (computer science), synchronizing program execution (computing), execution in some concurrent programming languages. Each is an object that acts as a proxy for a result that is initially unknown, usually because the computation of its value is not yet complete. The term ''promise'' was proposed in 1976 by Daniel P. Friedman and David Wise, and Peter Hibbard called it ''eventual''. A somewhat similar concept ''future'' was introduced in 1977 in a paper by Henry Baker (computer scientist), Henry Baker and Carl Hewitt. The terms ''future'', ''promise'', ''delay'', and ''deferred'' are often used interchangeably, although some differences in usage between ''future'' and ''promise'' are treated below. Specifically, when usage is distinguished, a future is a ''read-only'' placeholder view of a variable, while a promise is a writable, single assignment container which sets the value of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Task Parallelism
Task parallelism (also known as function parallelism and control parallelism) is a form of parallelization of computer code across multiple processors in parallel computing environments. Task parallelism focuses on distributing tasks—concurrently performed by processes or threads—across different processors. In contrast to data parallelism which involves running the same task on different components of data, task parallelism is distinguished by running many different tasks at the same time on the same data. A common type of task parallelism is pipelining, which consists of moving a single set of data through a series of separate tasks where each task can execute independently of the others. Description In a multiprocessor system, task parallelism is achieved when each processor executes a different thread (or process) on the same or different data. The threads may execute the same or different code. In the general case, different execution threads communicate with one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Task (computing)
In computers, computing, a task is a unit of execution (computing), execution or a unit of work. The term is ambiguous; precise alternative terms include ''process (computing), process'', light-weight process, ''thread (computing), thread'' (for execution), ''step'', ''request–response, request'', or ''query'' (for work). In the adjacent diagram, there are task queue, queues of incoming work to do and outgoing completed work, and a thread pool of threads to perform this work. Either the work units themselves or the threads that perform the work can be referred to as "tasks", and these can be referred to respectively as requests/responses/threads, incoming tasks/completed tasks/threads (as illustrated), or requests/responses/tasks. Terminology In the sense of "unit of execution", in some operating systems, a task is synonymous with a process (computing), process, and in others with a thread (computing), thread. In non-interactive execution (batch processing), a task is a unit o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiber (computer Science)
In computer science, a fiber is a particularly lightweight thread of execution. Like threads, fibers share address space. However, fibers use cooperative multitasking while threads use preemptive multitasking. Threads often depend on the kernel's thread scheduler to preempt a busy thread and resume another thread; fibers yield themselves to run another fiber while executing. Threads, fibers and coroutines The key difference between fibers and kernel threads is that fibers use cooperative context switching, instead of preemptive time-slicing. In effect, fibers extend the concurrency taxonomy: * on a single computer, multiple processes can run * within a single process, multiple threads can run * within a single thread, multiple fibers can run Fibers (sometimes called stackful coroutines or user mode cooperatively scheduled threads) and stackless coroutines (compiler synthesized state machines) represent two distinct programming facilities with vast performance and funct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Weight Kernel Threads
Light Weight Kernel Threads (LWKT) is a computer science term and from DragonFly BSD in particular. LWKTs differ from normal kernel threads in that they can preempt normal kernel threads. According to Matt Dillon, DragonFlyBSD creator: See also * Light-weight process *Thread (computing) 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. In many cases, a thread is a component of a pr ... Sources Matt Dillon's post about the LWKT scheduler* * * * * * * * * Threads (computing) DragonFly BSD {{Operating-system-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Green Threads
In computer programming, a green thread is a thread that is scheduled by a runtime library or virtual machine (VM) instead of natively by the underlying operating system (OS). Green threads emulate multithreaded environments without relying on any native OS abilities, and they are managed in user space instead of kernel space, enabling them to work in environments that do not have native thread support. Etymology Green threads refers to the name of the original thread library for Java programming language (that was released in version 1.1 and then Green threads were abandoned in version 1.3 to native threads). It was designed by ''The Green Team'' at Sun Microsystems. History Green threads were briefly available in Java between 1997 and 2000. Green threads share a single operating system thread through co-operative concurrency and can therefore not achieve parallelism performance gains like operating system threads. The main benefit of coroutines and green threads is ease ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU Portable Threads
GNU Pth (Portable Threads) is a POSIX/ANSI- C based user space thread library for UNIX platforms that provides priority-based scheduling for multithreading applications. GNU Pth targets for a high degree of portability. It is part of the GNU Project. Pth also provides API emulation for POSIX threads for backward compatibility. GNU Pth uses an N:1 mapping to kernel-space threads, i.e., the scheduling is done completely by the GNU Pth library and the kernel itself is not aware of the N threads in user-space. Because of this there is no possibility to utilize SMP as kernel dispatching would be necessary. See also *Fiber Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often inco ... References External links *Downloads {{DEFAULTSORT:Gnu Portable Threads Application programming interf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallel Extensions
Parallel Extensions was the development name for a managed concurrency library developed by a collaboration between Microsoft Research and the CLR team at Microsoft. The library was released in version 4.0 of the .NET Framework. It is composed of two parts: ''Parallel LINQ'' (PLINQ) and ''Task Parallel Library'' (TPL). It also consists of a set of ''coordination data structures'' (CDS) – sets of data structures used to synchronize and co-ordinate the execution of concurrent tasks. Parallel LINQ PLINQ, or Parallel LINQ, parallelizing the execution of queries on objects (LINQ to Objects) and XML data (LINQ to XML). PLINQ is intended for exposing data parallelism by use of queries. Any computation on objects that has been implemented as queries can be parallelized by PLINQ. However, the objects need to implement the IParallelEnumerable interface, which is defined by PLINQ itself. Internally it uses TPL for execution. Task Parallel Library The Task Parallel Library (TPL) is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NetBSD
NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was fork (software development), forked. It continues to be actively developed and is available for many platforms, including servers, desktops, handheld devices, and embedded systems. The NetBSD project focuses on code clarity, careful design, and portability across many computer architectures. Its source code is publicly available and Permissive free software licence, permissively licensed. History NetBSD was originally derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, Berkeley, via its Net/2 source code release and the 386BSD project. The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM AIX
AIX (pronounced ) is a series of Proprietary software, proprietary Unix operating systems developed and sold by IBM since 1986. The name stands for "Advanced Interactive eXecutive". Current versions are designed to work with Power ISA based Server (computing), server and workstation computers such as IBM's IBM Power Systems, Power line. Background Originally released for the IBM RT PC Reduced instruction set computer, RISC workstation in 1986, AIX has supported a wide range of hardware platforms, including the IBM IBM RS/6000, RS/6000 series and later IBM Power microprocessors, Power and PowerPC-based systems, IBM System i, System/370 mainframes, IBM PS/2, PS/2 personal computers, and the Apple Network Server. Currently, it is supported on IBM Power Systems alongside IBM i and Linux. AIX is based on UNIX System V with 4.3BSD-compatible extensions. It is certified to the UNIX 03 and UNIX V7 specifications of the Single UNIX Specification, beginning with AIX versions 5.3 an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
