Question

Sequence the following to compute the effective access time needed to service a page fault.
• [A.] Receive an interrupt from the disk I/O subsystem
• [B.] Trap the operating system and save the user registers and process state
• [C.] Determine that the interrupt was a page fault
• [D.] Correct the page table and other tables to show that the desired page is now in memory
• [E.] Restore the user registers, process state and new page table, and then resume the interrupted instruction
Choose the correct answer from the options given below:

• A. A, B, C, D and E
• B. B, C, D, E and A
• C. A, D, B, C and E
• D. B, C, A, D and E

Hint:

Always remember: Trap → Identify → Fetch → Update → Resume.

Answer 1

The Correct Option is D

Concept: Handling a page fault involves a well-defined sequence of steps executed by the operating system.

Step 1: Trap to OS and save state.
• CPU detects page fault
• Control transfers to OS
• Registers and process state are saved \[ \Rightarrow B \]

Step 2: Identify the interrupt cause.
• OS determines that the interrupt is due to a page fault \[ \Rightarrow C \]

Step 3: Fetch required page from disk.
• Disk I/O is initiated
• On completion, interrupt is received \[ \Rightarrow A \]

Step 4: Update page table.
• Page is loaded into memory
• Page table entries are updated \[ \Rightarrow D \]

Step 5: Restore and resume execution.
• Restore registers
• Resume interrupted instruction \[ \Rightarrow E \] Final Sequence: \[ B \rightarrow C \rightarrow A \rightarrow D \rightarrow E \] \[ \boxed{(4)} \]