Editing Memory paging (section)

=== Anticipatory paging ===
Some systems use only [[demand paging]]—waiting until a page is actually requested before loading it into RAM.

Other systems attempt to reduce latency by guessing which pages not in RAM are likely to be needed soon, and pre-loading such pages into RAM, before that page is requested. (This is often in combination with pre-cleaning, which guesses which pages currently in RAM are not likely to be needed soon, and pre-writing them out to storage).

When a page fault occurs, anticipatory paging systems will not only bring in the referenced page, but also other pages that are likely to be referenced soon.  A simple anticipatory paging algorithm will bring in the next few consecutive pages even though they are not yet needed (a prediction using [[locality of reference]]); this is analogous to a [[prefetch input queue]] in a CPU.  Swap prefetching will prefetch recently swapped-out pages if there are enough free pages for them.<ref>{{cite web|url=https://lwn.net/Articles/153353/|title=Swap prefetching|website=[[Linux Weekly News]]|date=September 27, 2005}}</ref>

If a program ends, the operating system may delay freeing its pages, in case the user runs the same program again.

Some systems allow application hints; the application may request that a page be made available and continue without delay.