Virtual Memory and Page Replacement Virtual memory is a memory management technique used by operating systems to address the limitations of physical memory (...
Virtual memory is a memory management technique used by operating systems to address the limitations of physical memory (RAM). It provides a larger address space than physically available, allowing programs to operate without exceeding RAM constraints. This is achieved by dividing physical memory into smaller units called pages.
Page replacement is a mechanism used by operating systems to swap out inactive or less recently used pages from physical memory to secondary storage (e.g., hard drive) when the system needs more memory. This is done to make space for more active processes and allows the system to run programs with larger memory requirements.
Benefits of virtual memory and page replacement:
Increased memory availability: Provides access to more memory than physically available.
Improved performance: Allows programs to run faster by accessing memory faster.
Reduced memory fragmentation: Pages are allocated in contiguous memory units, eliminating memory gaps.
How page replacement works:
Identification: Pages are identified and stored in a memory management table (MMT).
Replacement: When physical memory is full, pages are swapped out to secondary storage.
Loading: When a page is needed, it is loaded back into physical memory from secondary storage.
Mapping: The process of mapping virtual memory addresses to physical memory addresses is also maintained.
Example:
Imagine a program requiring 10 pages of memory. Instead of directly accessing 10 pages in physical memory, the operating system creates 4 pages and keeps the other pages in secondary storage. When the program needs a page, it is loaded from secondary storage into one of the virtual memory pages