A computer has twenty physical page frames which contain pages numbered 101 through 120. Now a program accesses the pages numbered 1, 2, …, 100 in that order, and repeats the access sequence THRICE. Which one of the following page replacement policies experiences the same number of page faults as the optimal page replacement policy for this program?
First of all how many Page Faults are there in optimal PRA?
I'm getting as following -
100 PF in 1st access of 100 pages.
80 PF in 2nd access of 100 pages.
80 PF in 3rd access of 100 pages.
Totally = 100+80+80 = 260 PF are there out of total 300 references of 100 pages.
Is that correct? whereas some people are having like -
100+(100-19)+(100-19) PF and some are going for 4th round. why the need to go to 4th access of 100 pages?