Page fault handling in Operating Systems - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What happens immediately after a page fault is detected?

When a program tries to access a page not currently in physical memory, a page fault occurs. What is the very first action the operating system takes after detecting this page fault?

A The OS locates the page on disk and loads it into a free frame in physical memory.

B The OS terminates the program immediately due to illegal memory access.

C The OS swaps out a page from physical memory without checking which page to remove.

D The OS ignores the fault and lets the program continue running.

💡 Hint

Think about what the OS must do to make the requested data available to the program.

When a page fault occurs, the OS must bring the missing page from disk into physical memory before the program can continue. It does not terminate the program immediately or ignore the fault. Also, it chooses which page to swap out carefully, not randomly.

📋 Factual

intermediate

Which component is responsible for detecting a page fault?

In a computer system, which hardware or software component detects that a page fault has occurred?

A The Central Processing Unit (CPU) arithmetic logic unit

B The Memory Management Unit (MMU)

C The Disk Controller

D The Network Interface Card (NIC)

💡 Hint

Consider which part handles virtual to physical address translation.

The MMU translates virtual addresses to physical addresses. If the page is not in memory, the MMU triggers a page fault. The CPU ALU handles calculations, the disk controller manages disk operations, and the NIC handles network communication.

🔍 Analysis

advanced

Analyzing page fault handling sequence

Consider the following sequence of steps in handling a page fault. Which step correctly follows the previous one?

1. Page fault is detected by the MMU.
2. Operating system saves the state of the interrupted process.
3. ?
4. Page is loaded into physical memory.

A The OS clears the page table entry without loading the page.

B The OS sends an interrupt to the network controller.

C The OS immediately resumes the interrupted process without loading the page.

D The OS selects a victim page to swap out if no free frame is available.

💡 Hint

Think about what the OS must do if there is no free space in memory.

If no free frame is available, the OS must choose a page to remove (victim page) to free space before loading the requested page. Resuming the process without loading the page or clearing the page table entry would cause errors. Sending an interrupt to the network controller is unrelated.

❓ Comparison

advanced

Difference between minor and major page faults

Which statement correctly distinguishes a minor page fault from a major page fault?

A A minor page fault causes the program to terminate; a major page fault does not.

B A minor page fault requires disk access; a major page fault does not.

C A minor page fault occurs when the page is in memory but not mapped; a major page fault requires loading the page from disk.

D A minor page fault happens only in virtual memory systems without paging.

💡 Hint

Consider whether disk access is needed in each case.

A minor page fault happens when the page is already in physical memory but not yet mapped to the process's page table, so no disk access is needed. A major page fault requires loading the page from disk into memory. The other options are incorrect descriptions.

❓ Reasoning

expert

Why does excessive page faulting degrade system performance?

Excessive page faults can cause a system to slow down drastically, a condition known as thrashing. Why does this happen?

A Because the CPU spends most of its time waiting for pages to be loaded from disk instead of executing instructions.

B Because the system runs out of disk space and cannot save pages.

C Because the network bandwidth is saturated by page fault interrupts.

D Because the operating system disables multitasking during page faults.

💡 Hint

Think about the speed difference between memory and disk.

Page faults require loading data from disk, which is much slower than memory. If page faults happen too often, the CPU waits a lot for disk I/O, reducing overall performance. Disk space or network bandwidth are not the main causes, and multitasking is not disabled during page faults.