System resource
 | This articleneeds additional citations forverification.(September 2015) |
Incomputing,asystem resource,or simplyresource,is anyphysicalorvirtualcomponent of limited availability that is accessible to acomputer.All connected devices and internal system components are resources. Virtual system resources includefiles(concretelyfile handles),networkconnections (concretelynetwork sockets), andmemoryareas.
Managing resources is referred to asresource management,and includes both preventingresource leaks(not releasing a resource when a process has finished using it) and dealing withresource contention(when multiple processes wish to access a limited resource). Computing resources are used incloud computingto provide services through networks.
Major resource types
[edit]- Interrupt request(IRQ) lines
- Direct memory access(DMA) channels
- Port-mapped I/O
- Memory-mapped I/O
- Locks
- Externaldevices
- External memory or objects, such as memory managed in native code, from Java; or objects in theDocument Object Model(DOM), fromJavaScript
General resources
[edit]- CPU,both time on a single CPU and use of multiple CPUs – seemultitasking
- Random-access memoryandvirtual memory– seememory management
- Hard diskdrives, 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, includingCPU cacheand MMU cache (translation lookaside buffer)
- Networkthroughput
- Electrical power
- Input/outputoperations
- Randomness
Categories
[edit]Some resources, notably memory and storage space, have a notion of "location", and one can distinguishcontiguousallocations fromnon-contiguousallocations. 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 asfragmentation,and often severely impacts performance, socontiguousfree space is a subcategory of the general resource of storage space.
One can also distinguishcompressibleresources fromincompressibleresources.[1]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 tothrashing(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 allowdiscardable memoryfor 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
[edit]References
[edit]- ^The Kubernetes resource model:"Some resources, such as CPU and network bandwidth, are compressible, meaning that their usage can potentially be throttled in a relatively benign manner."