Page Replacement Algorithms
The page replacement algorithm determines which page currently in memory should be replaced when the frames in main memory are full.
- Page removed should be the page least likely to be referenced in the near future
- Most policies predict the future behavior on the basis of past behavior
Optimal policy
- Selects for replacement that page for which the time to the next reference is the longest
- Impossible to have perfect knowledge of future events
LRU Policy (see page)
FIFO policy
- Page that has been in memory the longest is replaced
- Bases on the assumption that an ‘old’ page will not be referenced soon again.
- Treats page frames allocated to a process as a circular buffer
- Pages are removed in round-robin style
- Simplest replacement policy to implement
