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In computing, a system resource, or simply resource, is any computer hardware, physical or software, virtual component of limited availability within a Systems analyst, computer system. All connected devices and internal system components are resources. Virtual system resources include Computer file, files (concretely file handles), Computer network, network connections (concretely network sockets), and computer memory, memory areas. Managing resources is referred to as Resource management (computing), resource management, and includes both preventing resource leaks (not releasing a resource when a process has finished using it) and dealing with resource contention (when multiple processes wish to access a limited resource). Computing resources are used in cloud computing to provide services through networks.


Major resource types

* Interrupt request (PC architecture), Interrupt request (IRQ) lines * Direct memory access (DMA) channels * Port-mapped I/O * Memory-mapped I/O * Lock (computer science), Locks * External Peripheral, devices * External memory or objects, such as memory managed in native code, from Java; or objects in the Document Object Model (DOM), from JavaScript


General resources

* Central processing unit, CPU, both time on a single CPU and use of multiple CPUs – see Computer multitasking, multitasking * Random-access memory and virtual memory – see memory management * Hard disk drives, include space generally, contiguous free space (such as for swap space), and use of multiple physical devices ("spindles"), since using multiple devices allows parallelism * Cache space, including CPU cache and MMU cache (translation lookaside buffer) * Computer networking, Network throughput * Power management, Electrical power * Input/output operations * Randomness


Categories

Some resources, notably memory and storage space, have a notion of "location", and one can distinguish ''contiguous'' allocations from ''non-contiguous'' allocations. For example, allocating 1 GB of memory in a single block, versus allocating it in 1,024 blocks each of size 1 MB. The latter is known as fragmentation (computing), fragmentation, and often severely impacts performance, so ''contiguous'' free space is a subcategory of the general resource of storage space. One can also distinguish ''compressible'' resources from ''incompressible'' resources.The Kubernetes resource model
"Some resources, such as CPU and network bandwidth, are compressible, which means that their usage can potentially be throttled in a relatively benign manner." Compressible resources, generally throughput ones such as CPU and network bandwidth, can be throttled benignly: the user will be slowed proportionally to the throttling, but will otherwise proceed normally. Other resources, generally storage ones such as memory, cannot be throttled without either causing failure (if a process cannot allocate enough memory, it typically cannot run) or severe performance degradation, such as due to thrashing (computer science), thrashing (if a working set does not fit into memory and requires frequent paging, progress will slow significantly). The distinction is not always sharp; as mentioned, a paging system can allow main memory (primary storage) to be compressed (by paging to hard drive (secondary storage)), and some systems allow discardable memory for caches, which is compressible without disastrous performance impact. Electrical power is to some degree compressible: without power (or without sufficient voltage) an electrical device cannot run, and will stop or crash, but some devices, notably mobile phones, can allow degraded operation at reduced power consumption, or can allow the device to be suspended but not terminated, with much lower power consumption.


See also

* Computational resource * Linear scheduling method * Sequence step algorithm * System monitor


References

{{reflist Resources Computing terminology