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However, if the page size is increased to 32 KiB (2 15 bytes), only 2 17 pages are required. A multi-level paging algorithm can decrease the memory cost of allocating a large page table for each process by further dividing the page table up into smaller tables, effectively paging the page table.
The required disk space may be easily allocated on systems with more recent specifications (i.e. a system with 3 GB of memory having a 6 GB fixed-size page file on a 750 GB disk drive, or a system with 6 GB of memory and a 16 GB fixed-size page file and 2 TB of disk space).
By reducing the I/O activity caused by paging requests, virtual memory compression can produce overall performance improvements. The degree of performance improvement depends on a variety of factors, including the availability of any compression co-processors, spare bandwidth on the CPU, speed of the I/O channel, speed of the physical memory, and the compressibility of the physical memory ...
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".
A similar mechanism is used for memory-mapped files, which are mapped to virtual memory and loaded to physical memory on demand. When physical memory is not full this is a simple operation; the page is written back into physical memory, the page table and TLB are updated, and the instruction is restarted.
In computing, commit charge is a term used in Microsoft Windows operating systems to describe the total amount of virtual memory of all processes that must be backed by either physical memory or the page file. [1] Through the process of paging, the contents of this virtual memory may move between physical memory and the page file, but it cannot ...
The memory mapping process is handled by the virtual memory manager, which is the same subsystem responsible for dealing with the page file. Memory mapped files are loaded into memory one entire page at a time. The page size is selected by the operating system for maximum performance. Since page file management is one of the most critical ...
It is also helpful to use large pages in the host page tables to reduce the number of levels (e.g., in x86-64, using 2 MB pages removes one level in the page table). Since memory is typically allocated to virtual machines at coarse granularity, using large pages for guest-physical translation is an obvious optimization, reducing the depth of ...