On top of that, even giving it back via free() may not make much of a difference. For any Linux process, even after doing free() in a memory block, there is no guarantee that libc will return the memory to the operating system, and in most practical cases most likely does not, but rather keep it as a free chunk in their own pool for the next malloc request. For libc to return it it probably has to fulfill a bunch of requirements (full page 4k returned etc) which are rarely, if ever, met.