Module 4 - Set 2
Reference: Operating Systems:
Internals and Design principles by
William Stallings
, Replacement policy
• When all the frames in main memory are occupied, a
page fault is generated when a new page has to be
brought into the main memory
• The page that has to be replaced is decided by the
replacement policy (algorithm)
• Algorithms
– Optimal
– Least Recently Used (LRU)
– First in First out (FIFO)
– Clock
, Optimal
• Replaces that page for which the time to the
next reference is the longest
• Results in fewest number of page faults
• Difficult to implement – knowledge of the
future events is required
Reference: Operating Systems:
Internals and Design principles by
William Stallings
, Replacement policy
• When all the frames in main memory are occupied, a
page fault is generated when a new page has to be
brought into the main memory
• The page that has to be replaced is decided by the
replacement policy (algorithm)
• Algorithms
– Optimal
– Least Recently Used (LRU)
– First in First out (FIFO)
– Clock
, Optimal
• Replaces that page for which the time to the
next reference is the longest
• Results in fewest number of page faults
• Difficult to implement – knowledge of the
future events is required
