Question

Question 7 30 pts Consider the following page reference string: {1,2,3,4,1,5,6,2,1,2,3,7,6,3} Assume that the system has 4 page frames allocated to these 7 pages. Follow the page placement and replacement using the following three replacement algorithms: • LRU replacement • FIFO replacement • Optimal replacement How many page faults will occur for these three algorithms? Assume that all frames are initially empty, so your first unique pages will all cost one fault each USE ENCLOSED TABLES! Show all calculations in submitted file. Create an approximate graph: Number of page faults (Nf) as a function of the page frames allocated (Na) using the obtained values for Na-4. Least Recently Used (LRU) Strategy

Answer 1

Reference String: 1,2,3,4,1,5, 6, 2, 1, 2, 3, 7, 6, 3. Frames=4. LRU: Least Recently used. - We replace a page which was used least recently. Ref string 14 115612 LL23 763 PF1 PF2 PF3 PF4 Fault 1 2 3 4 15 6 2 I Ž LRU I = 1, 2, 3, 4, 6, 5, 6, 3, 7,2 are page faults. 7x7 W Total PF = 10

FIFO: page which came first will be First In First out of the replaced if necessary. Ret String 11 21 314151612412 3116131 NA PFI PF2 PFB РЕЧ Fault Total PF = 11 rt w

page which will not be used mostly in optimal; It'll replace a future. Ref string 11 21 31411 15162 111213171631 PF 1 PE2 РЕ 3 PF 4 Fault TT