Smmap wraps an interface around mmap and tracks the mapped files as well as the
amount of clients who use it. If the system runs out of resources, or if a
memory limit is reached, it will automatically unload unused maps to allow
continued operation.

To allow processing large files even on 32 bit systems, it allows only portions
of the file to be mapped. Once the user reads beyond the mapped region, smmap
will automatically map the next required region, unloading unused regions using
a LRU algorithm.

WWW: https://github.com/gitpython-developers/smmap