In computer science, the term "Least Frequently Used" (LFU) refers to a cache algorithm for memory management. The expiration policy removes entities from the cache that are used the least. If the use frequency of each entity is the same, then they are expired by the Least Recently Used (LRU) algorithm.

Variations

There are variations of the LFU algorithm.

LFU*

A revised version of the LFU policy proposed by M. Arlitt. This policy only considers documents whose reference counts are one when it needs to be removed. If the total size of documents whose reference counts are one is not enough to give room for the in-coming document, then the document is not cached and no document is removed.

LFU-Aging

This LFU policy addresses the problem of cache pollution

Cache pollution

Cache pollution describes situations where an executing computer program loads data into CPU cache unnecessarily, thus causing other needed data to be evicted from the cache into lower levels of the memory hierarchy, potentially all the way down to main memory, thus causing a performance...

. The aging policy is applied at interval to bring down the reference counts of such pages and ultimately make them candidates for replacement.

LFU*-Aging

This is the LFU* algorithm with LFU-Aging applied.

Window-LFU

An LFU algorithm that uses windows of time to estimate the frequency of usage over the cached population.