Page "Page replacement algorithm" Paragraph 51

The main problem with NFU is that it keeps track of the frequency of use without regard to the time span of use.

Thus, in a multi-pass compiler, pages which were heavily used during the first pass, but are not needed in the second pass will be favoured over pages which are comparably lightly used in the second pass, as they have higher frequency counters.

This results in poor performance.

Other common scenarios exist where NFU will perform similarly, such as an OS boot-up.

Thankfully, a similar and better algorithm exists, and its description follows.