Operating System Questions Medium
Paging is a memory management technique used in virtual memory systems to efficiently allocate and manage memory resources. It allows the operating system to divide the physical memory into fixed-size blocks called pages and the logical memory into equal-sized blocks called page frames.
In the concept of paging, the virtual memory is divided into fixed-size pages, typically 4KB in size. These pages are then mapped to corresponding physical memory frames. The mapping is maintained in a data structure called the page table, which keeps track of the virtual-to-physical address translations.
When a process requests memory, the operating system allocates a contiguous block of virtual memory pages for the process. However, these pages do not need to be physically contiguous in the physical memory. Instead, they can be scattered across different physical memory frames.
When a process accesses a virtual memory address, the operating system translates the virtual address to a physical address using the page table. If the page is not currently present in the physical memory, a page fault occurs. The operating system then retrieves the required page from the secondary storage (usually the hard disk) and brings it into the physical memory. This process is known as page swapping or page replacement.
Paging provides several benefits in virtual memory systems. It allows efficient memory allocation by dividing the memory into fixed-size pages, which can be easily managed and allocated to processes. It also enables memory protection by assigning different access permissions to different pages, preventing unauthorized access to memory regions. Paging also facilitates memory sharing between processes, as multiple processes can map the same page to their virtual memory space, reducing memory duplication.
Overall, paging in virtual memory systems plays a crucial role in optimizing memory utilization, providing memory protection, and enabling efficient memory management in modern operating systems.