First In First Out Page replacement

FIFO page replacement

First In First Out page replacement is the simplest page replacement. this algorithm associates with each page the time when that page was brought into memory. When a page must be replace, the oldest page is chosen.

Although FIFO is simple and easy, it is not always optimal, or even efficient. An interesting effect that can occur with FIFO is Belady's anomaly, in which increasing the number of frames available can actually increase the number of page faults that occur. Consider, for example, the following reference string ( 1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5 ). The number of page faults for four frames is 10 and the number of page faults for three frames is 9.