In
computer science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, ...
, resource contention is a conflict over access to a
shared resource
In computing, a shared resource, or network share, is a computer resource made available from one host to other hosts on a computer network.
It is a device or piece of information on a computer that can be remotely accessed from another compu ...
such as
random access memory
Random-access memory (RAM; ) is a form of electronic computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written ...
,
disk storage
Disc or disk may refer to:
* Disk (mathematics)
In geometry, a disk (Spelling of disc, also spelled disc) is the region in a plane (geometry), plane bounded by a circle. A disk is said to be ''closed'' if it contains the circle that constitut ...
,
cache memory
In computing, a cache ( ) is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsew ...
, internal
bus
A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a motor vehicle that carries significantly more passengers than an average car or van, but fewer than the average rail transport. It is most commonly used ...
es or external network devices. A resource experiencing ongoing contention can be described as oversubscribed.
Resolving resource contention problems is one of the basic functions of
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 ...
s. Various low-level mechanisms can be used to aid this, including
lock
Lock(s) or Locked may refer to:
Common meanings
*Lock and key, a mechanical device used to secure items of importance
*Lock (water navigation), a device for boats to transit between different levels of water, as in a canal
Arts and entertainme ...
s,
semaphore
Semaphore (; ) is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arra ...
s,
mutexes and
queues. The other techniques that can be applied by the operating systems include intelligent scheduling, application mapping decisions, and
page coloring.
Access to resources is also sometimes regulated by queuing; in the case of computing time on a
CPU the controlling
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...
of the
task queue is called a
scheduler
A schedule (, ) or a timetable, as a basic time-management tool, consists of a list of times at which possible tasks, events, or actions are intended to take place, or of a sequence of events in the chronological order in which such things ...
.
Failure to properly resolve resource contention problems may result in a number of problems, including
deadlock,
livelock
In concurrent computing, deadlock is any situation in which no member of some group of entities can proceed because each waits for another member, including itself, to take action, such as sending a message or, more commonly, releasing a lock. ...
, and
thrashing.
Resource contention results when multiple processes attempt to use the same shared resource. Access to memory areas is often controlled by semaphores, which allows a pathological situation called a deadlock, when different
threads or
processes try to allocate resources already allocated by each other. A deadlock usually leads to a program becoming partially or completely unresponsive.
In recent years, research on the contention is focused more on the resources in the
memory hierarchy
In computer architecture, the memory hierarchy separates computer storage into a hierarchy based on response time. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and contr ...
, e.g., last-level caches, front-side bus, and memory socket connection.
See also
*
Bus contention
Bus contention is an undesirable state in computer design where more than one device on a bus attempts to place values on it at the same time.
Bus contention is the kind of telecommunication contention that occurs when all communicating de ...
*
Cache coherence
In computer architecture, cache coherence is the uniformity of shared resource data that is stored in multiple local caches. In a cache coherent system, if multiple clients have a cached copy of the same region of a shared memory resource, all ...
*
Collision avoidance (networking)
*
Resource allocation
In economics, resource allocation is the assignment of available resources to various uses. In the context of an entire economy, resources can be allocated by various means, such as markets, or planning.
In project management, resource allocatio ...
References
Computational resources
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