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The maximum random access memory (RAM) installed in any computer system is limited by hardware, software and economic factors. The hardware may have a limited number of address bus bits, limited by the processor package or design of the system. Some of the address space may be shared between RAM, peripherals, and read-only memory.
The address space in which these MMIO locations appear is the same address space as that used by RAM, and while RAM can exist and be addressable above the 4 GiB point, these MMIO locations decoded by I/O devices cannot be. They are limited by PCI bus specifications to addresses of 0xFFFFFFFF (2 32 − 1) and below. With 4 GiB or more of RAM ...
When used for swap, zram (like zswap) allows Linux to make more efficient use of RAM, since the operating system can then hold more pages of memory in the compressed swap than if the same amount of RAM had been used as application memory or disk cache. This is particularly effective on machines that do not have much memory.
A space–time trade off can be applied to the problem of data storage. If data is stored uncompressed, it takes more space but access takes less time than if the data were stored compressed (since compressing the data reduces the amount of space it takes, but it takes time to run the decompression algorithm). Depending on the particular ...
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 dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed.
The disadvantage of this approach is that memory swap files are slower to read from than 'actual' memory, which can lead to performance drops. [2] Another disadvantage is that, when running out of real memory, the system is relying on the applications to not use the additional memory despite it being allocated to them.
Virtual memory combines active RAM and inactive memory on DASD [a] to form a large range of contiguous addresses.. In computing, virtual memory, or virtual storage, [b] is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" [3] which "creates the illusion to users of a very large (main) memory".
Those machines, and subsequent machines supporting memory paging, use either a set of page address registers or in-memory page tables [d] to allow the processor to operate on arbitrary pages anywhere in RAM as a seemingly contiguous logical address space. These pages became the units exchanged between disk and RAM.