Query about swapping etc

[tomjridge]

Just a quick question: how do you ensure that the memory is actually allocated in main RAM? What stops the OS from swapping the memory out? Or pushing it to disk as virtual memory?

[whitis]

It doesn't. The program fails to do what it says on the tin. It only uses up virtual memory not physical memory. It needs to call mlock() or mlockall() to lock those pages into RAM.