If we have infinite memory, then do we still be needing paging?

Question

Paging creates illusion that each process has infinite RAM by moving pages to and from disk. So if we have infinite memory(in some hypothetical situation), do we still need Paging? If yes, then why? I faced this question in an interview.

Answer 1

Assuming that "infinite memory" means infinite randomly accessable memory, or RAM, we will still need paging. Although paging is often associated with the ability to swap pages in and out of RAM to a hard disk to conserve memory, this is merely one aspect of paging. Here are some other reasons to have paging:

• Security. Paging is a method to enforce operating system security and memory protection by ensuring that a processes cannot access the memory of another process and that it cannot modify the resident kernel.
• Multitasking. Paging aids in multitasking by virtualizing the memory space, that is, address 0xFOO in Process A can be something completely different than 0xFOO in Process B
• Memory Allocation. Paging aids in memory allocation by reducing fragmentation and ensuring RAM is only allocated when accessed. What this means is that although a process needs, suppose, 100MB of continuous RAM space, this need not be continuous physically. Additionally, when a program requests 100MB of space, the operating system will tell the program it's safe to use that 100MB of space, yet it will not be actually allocated until the program uses that space to its fullest.

Admittedly, the latter would not be entirely necessary if one had infinite RAM, nonetheless; it is always good practice to be eifficient even when we are not resource constrained. It also demonstrates a use for paging that is sometimes not considered.