Pool (computer science): Difference between revisions
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{{Short description|Collection of ready-to-use resources}} |
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In computer science, a '''pool''' is a set of initialised resources that are kept ready to use, rather than [[Memory allocation|allocated]] and destroyed on demand. A client of the pool will request an object from the pool and perform operations on the returned object. When the client has finished with an object (or resource), it returns it to the pool rather than destroying it. |
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{{Refimprove|date=August 2015}} |
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In [[computer science]], a '''pool''' is a collection of resources that are kept in memory, ready to use, rather than the memory acquired on use or the memory released afterwards. In this context, ''resources'' can refer to [[System resource|system resources]] such as [[file handle]]s, which are external to a process, or internal resources such as [[object (computing)|objects]]. A pool [[Client (computing)|client]] requests a resource from the pool and performs desired operations on the returned resource. When the client finishes its use of the resource, it is returned to the pool rather than released and lost.{{clarify|reason=Are the pool, the client, and the server all part of the same process? Sometimes, never, or always?|date=December 2018}} |
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Pooling of resources can offer a significant performance boost in situations where the cost of initializing a [[class instance]] is high, the rate of instantiation of a class is high, and the number of instances in use at any one time is low. The pooled resource is obtained in predictable time when creation of the new objects (especially over network) may take variable time. |
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The pooling of resources can offer a significant response-time boost in situations that have high cost associated with resource acquiring, high rate of the requests for resources, and a low overall count of simultaneously used resources. Pooling is also useful when the [[Latency (engineering)|latency]] is a concern, because a pool offers predictable times required to obtain resources since they have already been acquired. These benefits are mostly true for system resources that require a [[system call]], or remote resources that require a network communication, such as [[database connection]]s, [[socket connection]]s, [[Thread (computing)|threads]], and [[memory allocation]]. Pooling is also useful for expensive-to-compute data, notably large graphic objects like [[font]]s or [[bitmap]]s, acting essentially as a data [[Cache (computing)|cache]] or a [[memoization]] technique. |
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However, these benefits are mostly true for objects which are expensive with respect to time, such as [[database connection]]s, [[socket connection]]s, [[Thread (computing)|threads]] and large graphic objects like [[font]]s or [[bitmap]]s. In certain situations, simple object pooling (which hold no external resources, but only occupy memory) may not be efficient and could decrease performance.<ref>{{cite web |
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Special cases of pools are [[connection pool]]s, [[thread pool]]s, and [[memory pool]]s. |
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== Object pools == |
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{{Main|Object pool pattern}} |
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Pools can also be used for objects, in which context a ''pool'' refers to a [[design pattern]] for implementing pools in [[object-oriented language]]s, such as in the [[object pool pattern]]. Objects themselves hold no external resources and only occupy memory, although an already created object avoids the memory allocation required on object creation. Object pools are useful when the cost of [[object creation]] is high, but in certain situations this simple object pooling may not be efficient and could in fact decrease performance.<ref>{{cite web |
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| title = Java theory and practice: Urban performance legends, revisited |
| title = Java theory and practice: Urban performance legends, revisited |
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| date = 2005-09-27 | archivedate = 2011-12-29 | accessdate = 2013-10-31 |
| date = 2005-09-27 | archivedate = 2011-12-29 | accessdate = 2013-10-31 |
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| website = ibm.com |
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Special cases are: |
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* [[Connection pool]] |
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* [[Thread pool]] |
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* [[Memory pool]] |
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Pool can also refer to a [[design pattern]] for implementing them in object-oriented languages, such as the [[object pool pattern]]. |
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==References== |
==References== |
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[[Category:Database management systems]] |
[[Category:Database management systems]] |
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[[Category:Memory management]] |
[[Category:Memory management]] |
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{{database-stub}} |
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Latest revision as of 13:09, 1 September 2023
 | This article needs additional citations for verification. (August 2015) |
In computer science, a pool is a collection of resources that are kept in memory, ready to use, rather than the memory acquired on use or the memory released afterwards. In this context, resources can refer to system resources such as file handles, which are external to a process, or internal resources such as objects. A pool client requests a resource from the pool and performs desired operations on the returned resource. When the client finishes its use of the resource, it is returned to the pool rather than released and lost.[clarification needed]
The pooling of resources can offer a significant response-time boost in situations that have high cost associated with resource acquiring, high rate of the requests for resources, and a low overall count of simultaneously used resources. Pooling is also useful when the latency is a concern, because a pool offers predictable times required to obtain resources since they have already been acquired. These benefits are mostly true for system resources that require a system call, or remote resources that require a network communication, such as database connections, socket connections, threads, and memory allocation. Pooling is also useful for expensive-to-compute data, notably large graphic objects like fonts or bitmaps, acting essentially as a data cache or a memoization technique.
Special cases of pools are connection pools, thread pools, and memory pools.
Object pools[edit]
Pools can also be used for objects, in which context a pool refers to a design pattern for implementing pools in object-oriented languages, such as in the object pool pattern. Objects themselves hold no external resources and only occupy memory, although an already created object avoids the memory allocation required on object creation. Object pools are useful when the cost of object creation is high, but in certain situations this simple object pooling may not be efficient and could in fact decrease performance.[1]
References[edit]
- ^ "Java theory and practice: Urban performance legends, revisited". ibm.com. 2005-09-27. Archived from the original on 2011-12-29. Retrieved 2013-10-31.
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