mmap() tricks you into thinking you can directly access the disk. What really happens when you access the mapped data is that the CPU generates a page fault, th

mmap() tricks you into thinking you can directly access the disk. What really happens when you access the mapped data is that the CPU generates a page fault, the OS takes control, copies the data from disk to physical memory and maps the page in your address space. So essentially it is a convient way to do read(). The mmap() model is good. The current page fault mechanism, not so much.