Page Replacement Algorithm - Anticipatory Paging

Anticipatory Paging

Some systems use 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 the next few consecutive pages (analogous to a prefetch input queue in a CPU).

The swap prefetch mechanism goes even further in loading pages (even if they are not consecutive) that are likely to be needed soon.