What is a page fault handler and what steps are typically performed to bring a page into memory?

• A. Page fault handler resolves missing pages by selecting a victim page, evicting if needed, reading the required page from disk into a free frame, updating page tables and TLB, and resuming execution.
• B. Page fault handler terminates the process.
• C. Page fault handler clears the entire memory.
• D. Page fault handler ignores the fault and resumes execution.

Answer: (A)

Demand paging relies on a page fault handler. When a program references a page that isn’t currently in physical memory, control transfers to the OS, and the handler must determine the faulting address and whether the access is valid. If the page is valid but not present, the handler may need to free a frame by selecting a victim page and evicting it, writing it back to disk if it’s dirty. Then it reads the required page from disk into that frame. The page table is updated to reflect the new frame and the page as present, and the TLB is updated (or flushed) so future translations use the new mapping. Finally, the instructions that were interrupted are resumed. This sequence is exactly how a page fault is resolved in a system that uses demand paging.