The MM library is a 2-layer abstraction library, which simplifies the usage of shared memory between forked and, in this example, strongly related processes under Unix platforms. On the first layer it hides all platform dependent implementation details; allocation and locking, when dealing with shared memory segments, and on the second layer it provides a high-level malloc(3)-style API for a convenient and well known way to work with data-structures inside those shared memory segments.

The library is released under the term of an open-source, BSD-style license, because it was originally written as a proposal for use inside the next version of the Apache web server as a base library for providing shared memory pools to Apache modules, Currently Apache modules can only use heap-allocated memory, which isn't shared across the pre-forked server processes. The requirement actually comes from comprehensive modules like mod_ssl, mod_perl and mod_php, which would benefit a lot from easy to use shared memory pools.