ITPEC FE Morning October 2018 Question 21

LRU Page Replacement — identify the criterion used by the Least Recently Used algorithm.

LRU replaces the page with the oldest last-referenced time — the page that has gone the longest without being accessed.

• •LRU — tracks last referenced time (when was this page used most recently?)
• •LFU — tracks frequency of references (how often is this page used?)
• •FIFO — tracks first referenced time (when was this page first loaded?)

Why not others:
- (a) Cumulative total number of references — this is the criterion for LFU, not LRU
- (b) The first referenced time — this is the criterion for FIFO
- (c) Frequency of references per unit of time — this is another form of LFU

Key rule: LRU = "when last used"; LFU = "how often used"; FIFO = "when first loaded."

AI-generated — may contain errors