mmap: will the mapped file be loaded into memory immediately?

Question

From the manual, I just know that mmap() maps a file to a virtual address space, so the file can be randomly accessed. But, it is unclear to me that whether the mapped file

Answer 1

Yes. The whole point of mmap is that is manages memory more efficiently than just slurping everything into memory.

Of course, any given implementation may in some situations decide that it's more efficient to read in the whole file in one go, but that should be transparent to the program calling mmap.