Minnessmappning

Minnessmappning, or memory mapping, is a technique used in computer programming where a file or a device is directly associated with a region of the process's virtual address space. Instead of performing explicit read and write operations through system calls, the program can access the file or device content as if it were an array in memory. This allows for very efficient data access, especially for large files, as the operating system handles the loading and unloading of data between physical memory and secondary storage.

The primary benefit of memory mapping is performance. When a file is memory-mapped, the operating system can load portions of the file into RAM only when they are accessed. This avoids the overhead of traditional file I/O operations, such as `read()` and `write()`, which often involve copying data between user space and kernel space buffers. Memory mapping also facilitates sharing memory between processes. Multiple processes can map the same file into their respective address spaces, allowing them to access and modify the same data directly. This is a common mechanism for inter-process communication (IPC).

There are different types of memory mapping. File-backed mapping associates a region of memory with a specific file on disk. Anonymous mapping, on the other hand, creates a region of memory that is not associated with any file; it is typically used for dynamically allocated memory. The operating system manages the swapping of pages between memory and disk, ensuring that only the actively used parts of the mapped region reside in physical RAM.