Ad
related to: virtual memory is needed because one
Search results
Results From The WOW.Com Content Network
Virtual memory makes application programming easier by hiding fragmentation of physical memory; by delegating to the kernel the burden of managing the memory hierarchy (eliminating the need for the program to handle overlays explicitly); and, when each process is run in its own dedicated address space, by obviating the need to relocate program code or to access memory with relative addressing.
In effect, physical main memory becomes a cache for virtual memory, which is in general stored on disk in memory pages. Programs are allocated a certain number of pages as needed by the operating system. Active memory pages exist in both RAM and on disk. Inactive pages are removed from the cache and written to disk when the main memory becomes ...
One of the main driving factors for the development of hardware assists for the System/370 was virtual memory itself. When the guest was an operating system that itself implemented virtual memory, even non-privileged instructions could experience longer execution times - a penalty imposed by the requirement to access translation tables not used ...
The address is checked against the contents of the bounds register to prevent a process from accessing memory beyond its assigned segment. The operating system is not constrained by the hardware and can access all of physical memory. This technique protects memory used by one process against access or modification by another.
Virtual memory can be backed by physical RAM, a disk file via mmap (on Unix-derivatives) or MapViewOfFile (on Windows), or swap space, and the operating system can move virtual memory pages around as it needs. Because virtual memory does not need to be backed by physical memory, exhaustion of it is rare, and usually there are other limits ...
Programs which use the same library have virtual addresses that map to the same pages (which contain the library's code and data). When programs want to modify the library's code, they use copy-on-write, so memory is only allocated when needed. Shared memory is an efficient means of communication between programs.
Single-level storage (SLS) or single-level memory is a computer storage term which has had two meanings. The two meanings are related in that in both, pages of memory may be in primary storage or in secondary storage (disk), and that the physical location of a page is unimportant to a process.
Memory virtualization technology follows from memory management architectures and virtual memory techniques. In both fields, the path of innovation has moved from tightly coupled relationships between logical and physical resources to more flexible, abstracted relationships where physical resources are allocated as needed.