memorymapping

Memory mapping is a technique that allows a region of a process’s virtual address space to be mapped directly to a file or other object in memory. Once mapped, the program can access the contents through normal memory reads and writes instead of using explicit I/O system calls. The operating system maintains a mapping from virtual addresses to physical memory objects, typically via page tables and a translation lookaside buffer (TLB). When a mapped page is accessed, a page fault may occur to load data on demand, a mechanism known as demand paging.

Mappings can be file-backed, where the memory region corresponds to a file’s contents, or anonymous, where the region is initialized to zero and used for dynamic memory. Memory regions can also be shared between processes (shared mappings) or private (copy-on-write mappings). Access protections such as read, write, and execute are enforced by the mapping, and changes to shared mappings may be written back to disk or visible to other processes depending on the mapping type.

Common uses include memory-mapped files for large data processing, where random access to big datasets is efficient, and interprocess communication via shared memory. In many operating systems, APIs such as POSIX mmap/munmap or Windows MapViewOfFile/CreateFileMapping implement memory mappings. Advantages include simplified I/O semantics, potential zero-copy data transfer, and reduced system-call overhead. Drawbacks include dependence on OS and hardware behavior, potential paging latency, and complexity in synchronization and cache coherence. Proper use requires consideration of file lifetime, cache effects, and address-space fragmentation.