Mälulehekülgamine

Mälulehekülgamine, also known as memory paging, is a memory management technique used in operating systems. It allows the system to use more main memory (RAM) than is physically available by temporarily transferring data from RAM to secondary storage, such as a hard drive or solid-state drive. This secondary storage space is often referred to as a swap file or swap partition.

The fundamental concept behind mälulehekülgamine is the division of both physical memory and secondary storage into fixed-size blocks called pages. When the CPU needs to access data that is not currently in RAM, a page fault occurs. The operating system's memory manager then handles this fault by locating the required page on the secondary storage. It selects a page in RAM that is least likely to be needed soon and writes it to the swap file. The required page from the swap file is then loaded into the freed space in RAM.

This process enables the execution of programs that require more memory than the system physically possesses. It also contributes to process isolation, as each process can be assigned its own virtual address space, with pages mapped to physical memory as needed. While effective, mälulehekülgamine can introduce performance overhead, especially if frequent swapping occurs, leading to what is commonly known as "thrashing," where the system spends more time managing pages than executing instructions. The efficiency of mälulehekülgamine depends on factors such as the amount of RAM, the size of pages, and the effectiveness of the page replacement algorithm used by the operating system.