What is Page fault?

Page fault in the explanations

• A page fault is an exception raised when the accessed page's page-table entry is invalid, meaning it is not mapped to physical memory (it was paged out or never loaded), or when the access is not permitted, such as writing a read-only page.

  When does a page fault occur?

• For a page fault from a legitimate access, the OS finds a free physical page (evicting another if needed), reads the contents from disk and marks the page-table entry valid.

  When a page fault occurs on a page that was evicted to disk…

• When too-deep recursion pushes the stack into that page, a page fault occurs and the OS stops the program (a segmentation fault).

  When recursion goes so deep that it exceeds the stack limit…

Questions that mention Page fault (10)

1. When does a page fault occur?
2. When a page fault occurs on a page that was evicted to disk, what does the OS do?
3. Memory access time is 100 ns and handling a page fault takes 8 ms. If a page fault occurs once per million accesses, what is the average access time approximately?
4. When recursion goes so deep that it exceeds the stack limit, what generally happens on Linux and similar systems?
5. Which is the usual distinction between interrupts and exceptions?
6. What is the advantage of using copy-on-write when duplicating a process?
7. Which describes demand paging?
8. What generally happens when a program accesses an address the OS has not allocated?
9. In a mechanism that maps a file into memory (such as mmap), what happens when the file's contents are read?
10. Under the first-touch policy common on Linux NUMA systems (a page is placed in the memory of the node where the thread first writing it runs), what should programmers watch out for?

Related terms

Demand paging TLB (translation lookaside buffer) Copy-on-write System call Non-uniform memory access (NUMA) ASID Context switch Device driver Hypervisor Interrupt handler