replace - When does FIFO win over LRU replacement algorithm?

Question

I need a sequence of numbers when FIFO wins over LRU. Let's say under 15 numbers and number of pages are 3. I want FIFO to get fewer page faults than LRU. Is it possible?

question from:https://stackoverflow.com/questions/66047001/when-does-fifo-win-over-lru-replacement-algorithm

Answer 1

For a three-page cache, the sequence 1, 2, 3, 1, 4, 2 will do the trick. Evolution of the caches:

FIFO    LRU
1       1
12      12
123     123 [three misses for both as the cache fills]
123     231 [LRU moves 1 to the back]
234     314
234     142 [LRU but not FIFO misses on 2]