Computer Architecture Questions Medium
Virtual memory is a memory management technique used in computer architecture that allows the operating system to use a combination of physical memory (RAM) and secondary storage (usually a hard disk) to effectively increase the available memory for running programs.
The concept of virtual memory is based on the principle of dividing the logical memory space of a process into smaller units called pages. These pages are typically of fixed size and are stored in secondary storage. The physical memory is also divided into fixed-sized blocks called frames.
When a program is executed, only a portion of it is loaded into the physical memory, specifically the pages that are currently needed. The operating system keeps track of the mapping between the logical addresses used by the program and the physical addresses in the memory. This mapping is maintained in a data structure called the page table.
When a program accesses a memory location, the processor first checks if the corresponding page is present in the physical memory. If it is, the processor directly accesses the data. However, if the required page is not present in the physical memory, a page fault occurs.
In the event of a page fault, the operating system retrieves the required page from the secondary storage and replaces a less frequently used page in the physical memory with the new page. This process is known as page swapping or page replacement. The page table is updated accordingly to reflect the new mapping.
Virtual memory provides several benefits. Firstly, it allows programs to utilize more memory than physically available, enabling the execution of larger and more complex applications. It also provides memory protection, as each process has its own virtual address space, preventing one process from accessing or modifying the memory of another process. Additionally, virtual memory allows for efficient memory management, as the operating system can dynamically allocate and deallocate memory pages as needed.
In summary, virtual memory is a technique that allows the operating system to use a combination of physical memory and secondary storage to provide an illusion of a larger memory space to running programs. It enhances the overall performance and efficiency of the system by effectively managing memory resources.