32
$\begingroup$

WP has an adequate discussion of paging, which I think I understand.. However I am confused by the articles repeated use of the term Page Frame.

I thought frames and pages were different things. Could someone please clarify the difference.

Improve this question
$\endgroup$

3 Answers 3

Reset to default
47
$\begingroup$

Short version: "page" means "virtual page" (i.e. a chunk of virtual address space) and "page frame" means "physical page" (i.e. a chunk of physical memory).

That's it, pretty much. It's important to keep the two concepts distinct because at any given time, a page may not be backed by a page frame (it could be a zero-fill page which hasn't been accessed, or paged out to secondary memory), and a page frame may back multiple pages (sometimes in different address spaces, e.g. shared memory or memory-mapped files).

Improve this answer
$\endgroup$
4
  • 5
    $\begingroup$ Also multiple virtual address pages may be mapped to the same physical page frame (often with Copy On Write) and in a NUMA system a single virtual address page may map to multiple physical page frames (to exploit locality). $\endgroup$
    – user4577
    Apr 30, 2013 at 12:06
  • $\begingroup$ I think I covered the first point you made, but the second point is also well-made. Distributed-memory architectures complicate things a lot. $\endgroup$
    – Pseudonym ♦
    May 3, 2013 at 5:10
  • $\begingroup$ Yes, reading comprehension failure! :-( $\endgroup$
    – user4577
    May 3, 2013 at 11:55
  • $\begingroup$ Could you answer the followings? What does "be backed by" mean? What should be understood? $\endgroup$
    – Soner from The Ottoman Empire
    Apr 15, 2019 at 10:42
6
$\begingroup$

Physical memory is organized into frames and virtual memory into pages. The "page frame" term is a bit confusing and in my opinion wikipedia shouldn't use it. What they really mean by "page frame" is a block/group/segment of physical memory, which is equivalent to a frame. So they should instead use the term "frame", not "page frame".

In short remember:

  • page = block of consecutive virtual memory
  • frame = block of consecutive physical memory

That is how i use it.

Improve this answer
$\endgroup$
-2
$\begingroup$

A page frame is a storage unit within the main memory, while a page is the contents in the frame.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.