I'm not sure overcommitment is the same thing: https://www.kernel.org/doc/Documentation/vm/overcommit-accounting https://www.kernel.org/doc/Documentation/vm/ove

I'm not sure overcommitment is the same thing: https://www.kernel.org/doc/Documentation/vm/overcommit-accounting https://www.kernel.org/doc/Documentation/vm/overcommit-accou... Reading that, I think overcommitment is to determine the kernel's behavior when you try to allocate more virtual memory than physical memory that is present on the system. That is a different (but related) concern from the fact that mmap() will allocate virtual memory but not physical memory. (That is, mmap() reserves locations in the address space, but you don't have any physical memory backing it until you use that memory.)