How does mmap work?

Question

I am working on programs in Linux which needs mmap file from harddrive, but i have a question, what can make it fail. Like if all the memories are fragmented, which has only

Answer 1

The short answer is: it depends.

Depending on the amount of memory you have, the environment you're working in, or the way the mapping is accessed, there are a number of ways mmap can fail. Read the manual page for mmap for more details.