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, ...

, 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 A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and is exp ...

such as

file handle In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typically ha ...

s, which are external to a process, or internal resources such as objects. A pool

client Client(s) or The Client may refer to: * Client (business) * Client (computing), hardware or software that accesses a remote service on another computer * Customer or client, a recipient of goods or services in return for monetary or other valuable ...

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. 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 In computing, a system call (syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, accessing a hard disk drive ...

, or remote resources that require a network communication, such as

database connection A database connection is a facility in computer science that allows client software to talk to database server software, whether on the same machine or not. A connection is required to send commands and receive answers, usually in the form of a ...

s, socket connections, threads, and

memory allocation Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynam ...

. Pooling is also useful for expensive-to-compute data, notably large graphic objects like

font In metal typesetting, a font is a particular size, weight and style of a ''typeface'', defined as the set of fonts that share an overall design. For instance, the typeface Bauer Bodoni (shown in the figure) includes fonts " Roman" (or "regul ...

s or

bitmap In computing, a bitmap (also called raster) graphic is an image formed from rows of different colored pixels. A GIF is an example of a graphics image file that uses a bitmap. As a noun, the term "bitmap" is very often used to refer to a partic ...

s, acting essentially as a data

cache Cache, caching, or caché may refer to: Science and technology * Cache (computing), a technique used in computer storage for easier data access * Cache (biology) or hoarding, a food storing behavior of animals * Cache (archaeology), artifacts p ...

or a

memoization In computing, memoization or memoisation is an optimization technique used primarily to speed up computer programs by storing the results of expensive function calls to pure functions and returning the cached result when the same inputs occur ag ...

technique. Special cases of pools are

connection pool In software engineering, a connection pool is a cache of reusable database connections managed by the client or middleware. It reduces the overhead of opening and closing connections, improving performance and scalability in database applications. ...

thread pool In computer programming, a thread pool is a software design pattern for achieving concurrency of execution in a computer program. Often also called a replicated workers or worker-crew model, a thread pool maintains multiple threads waiting for ...

s, and

memory pool Memory pools, also called fixed-size blocks allocation, is the use of pools for memory management that allows dynamic memory allocation. Dynamic memory allocation can, and has been achieved through the use of techniques such as malloc and C ...

Object pools

Pools can also be used for objects, in which context a ''pool'' refers to a

design pattern A design pattern is the re-usable form of a solution to a design problem. The idea was introduced by the architect Christopher Alexander and has been adapted for various other disciplines, particularly software engineering. The " Gang of Four" ...

for implementing pools in

object-oriented language Object-oriented programming (OOP) is a programming paradigm based on the concept of '' objects''. Objects can contain data (called fields, attributes or properties) and have actions they can perform (called procedures or methods and impleme ...

s, such as in the

object pool pattern The object pool pattern is a software creational design pattern that uses a set of initialized objects kept ready to use – a "pool" – rather than allocating and destroying them on demand. A client of the pool will request an object from the ...

. 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 Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Object (abstract), an object which does not exist at any particular time or place ** Physical object, an identifiable collection of matter * Goal, an a ...

is high, but in certain situations this simple object pooling may not be efficient and could in fact decrease performance.

References

Database management systems Memory management {{database-stub