Meaning
Operating system service links the logical contents of a disk file directly to the virtual address space of a specific software process. Using memory mapped files allows an application to read or modify large binary datasets as if they were residing entirely in RAM. The kernel manages the actual loading of pages from storage only when they are accessed.
This technique minimizes the number of read system calls while maximizing usage of the system cache.
Efficient Paging
Memory handles individual blocks of data on demand rather than loading the full file at startup. When the cpu looks at an unread address, the hardware triggers a transparent fetch from the storage drive. Data transfers happen in the background while the application logic moves forward.
Writing to the specific address eventually triggers a flush back to the permanent disk.
Shared Space
Multiple processes can map the same file to coordinate between themselves using high speed memory triggers. This configuration enables faster communication than standard sockets or pipes. Because the data persists in a file, it survives after the software stops running.
Synchronized updates keep every instance looking at exactly the same version of the information.
Operating Boundary
System performance relies on the amount of physical memory available to hold the active pages. If the dataset exceeds the limits of the cache, performance stalls due to constant disk activity. Handling large maps requires careful attention to 64 bit pointer ranges.
Failure occurs when the disk runs out of space for the swap file.
