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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".
Virtual memory systems abstract between physical RAM and virtual addresses, assigning virtual memory addresses both to physical RAM and to disk-based storage, expanding addressable memory, but at the cost of speed. NUMA and SMP architectures optimize memory allocation within multi-processor systems. While these technologies dynamically manage ...
A modern computer operating system usually uses virtual memory to provide separate address spaces or separate regions of a single address space, called user space and kernel space. [1] [a] Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour.
A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in a page table.It is the smallest unit of data for memory management in an operating system that uses virtual memory.
Virtual memory is a system where physical memory is managed by the operating system typically with assistance from a memory management unit, which is part of many modern CPUs. It allows multiple types of memory to be used.
In virtual memory systems the operating system limits how a process can access the memory. This feature, called memory protection , can be used to disallow a process to read or write to memory that is not allocated to it, preventing malicious or malfunctioning code in one program from interfering with the operation of another.
In computing, a virtual address space (VAS) or address space is the set of ranges of virtual addresses that an operating system makes available to a process. [1] The range of virtual addresses usually starts at a low address and can extend to the highest address allowed by the computer's instruction set architecture and supported by the operating system's pointer size implementation, which can ...
Hardware-assisted virtualization first appeared on the IBM System/370 in 1972, for use with VM/370, the first virtual machine operating system. IBM added virtual memory hardware to the System/370 series in 1972 which is not the same as Intel VT-x Rings providing a higher privilege level for Hypervisor to properly control Virtual Machines ...