LRU Clock (Not Recently Used)
Basic idea is to reflect the passage of time in the actual data structures and sweeping method.
Arrange all of physical pages in a big circle (a clock).
A clock hand is used to select a good LRU candidate:
- sweep through the pages in circular order like a clock.
- if the ref bit is off, it’s a good page.
- else, turn the ref bit off and try next page.
Arm moves quickly when pages are needed.
Low overhead when plenty of memory
If memory is big, “accuracy” of information degrades.