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home / developersection / forums / what is virtual memory? how is it implemented?
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Revati S Misra
Revati S Misra

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Skilled in SEO, content writing, and digital marketing. Completed several years of working in many organizations including multinational companies. I love to learn new things in life that keep me motivated.

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Krishnapriya Rajeev
Krishnapriya Rajeev 01 Apr 2023
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Virtual memory is a memory management technique used by modern operating systems to provide a larger address space than the physical memory available on a computer. It allows a process to use more memory than what is physically available by creating a virtual address space for the process, which is mapped to physical memory by the operating system.

The virtual memory system divides the virtual address space into fixed-size blocks called pages. Each page is mapped to a physical page frame in the physical memory. When a process tries to access a memory location in its virtual address space that is not currently in physical memory, a page fault occurs. The operating system then fetches the page from the disk and brings it into a free page frame in physical memory. This process is known as page swapping.

The implementation of virtual memory involves several components, including:

  • Page table: A table maintained by the operating system that maps virtual page numbers to physical page frame numbers.
  • Page fault handler: A software routine that is invoked when a process tries to access a page that is not currently in physical memory.
  • Page replacement algorithm: A strategy used by the operating system to select which page to replace when all physical memory is already in use. Common page replacement algorithms include LRU (Least Recently Used), FIFO (First In First Out), and Optimal.
  • Disk I/O subsystem: The system responsible for transferring pages between the physical memory and the disk.
  • TLB (Translation Lookaside Buffer): A cache that stores recently used page table entries to speed up the translation of virtual addresses to physical addresses.

One advantage of virtual memory is that it enables a computer to run more programs or larger programs than it could otherwise, by using disk space as additional memory. Another advantage is that it provides memory protection, which prevents a program from accessing the memory space of another program.

However, it also causes increased overhead due to page swapping, which slows down the system's performance.

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