# LRU page replacement policy

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Self doubt:

What is the rule or keyb point we should keep in mind while solving problems on LRU page replacement algorithm? Please explain with examples.

My definition about LRU is Replace the page which one is Long-ago Used

given reference string is 1,2,4,5,6,1,2,3..... using demand-paging said  that already two pages brought in main memory 1 ,2 and 1 is brought before 2

then

in the reference string very first 1 and 2 are hits but not the page faults

2) which page is long-ago used

given reference string is 1,2,4,5,6,1,2,3..... think each reference is in different month first 1 is in jan, first 2 is in feb, 4 is in mar, 5 is in apr, 6 is in may, second 1 is June , second 2 is in July etc... if a hit occurs consider the page respective month is updated to new one ( 1 is June and 2 is July in this example ). if a page fault occurs replace the page with which have long-ago referred...

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## Related questions

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if you have 10 Frames and using LRU how many page fault will be there in both below: for (int j = 0; j < 100; j++) for (int i = 0; i < 100; i++) A[i][j] = A[i][j] + A[j][i]; for (int i = 0; i < 100; i++) for (int j = 0; j < 100; j++) A[i][j] = A[i][j] + A[j][i];
Determine the number of page faults when references to pages occur in the following order: $1,2,4,5,2,1,2,4$. Assume that the main memory can accommodate $3$ pages and the main memory already has the pages $1$ and $2$, with page $1$ having been brought earlier than page $2$.(LRU algorithm is used). $3$ $5$ $4$ None of these.