CIS3360_HW7_Solution-4-28-09

# CIS3360_HW7_Solution-4-28-09 - CIS 3360 Security in...

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CIS 3360 – Security in Computing Spring 2010 Solution for Assignment 7 (100 points) 1. Given five memory partitions of 500 KB, 100 KB, 300 KB, 200 KB, and 600 KB (in order), how would each of the first-ft, best-fit and worst-fit algorithms place processes of 350 KB, 450 KB, 300 KB and 200 KB (in order) ? Assume that once a partition is used, the unused part cannot be assigned to any other process. Which algorithms make the most efficient use of memory? [15 points] Answer: Size of Partition First Fit Best Fit Worst Fit 500KB 350 KB 350 KB 450 KB 100KB 300KB 300 KB 300 KB 300 KB 200KB 200 KB 200 KB 200 KB 600KB 450 KB 450 KB 350 KB If we calculate the percentage of the memory that is not effectively utilized, we can see: First Fit: 1-(350+300+200+450)/(500+100+300+200+600)=0.24 Best Fit: 1-(350+300+200+450)/(500+100+300+200+600)=0.24 Worst Fit: 1-(350+300+200+450)/(500+100+300+200+600)=0.24 In this particular scenario, all three algorithms perform the same in terms of memory efficiency. 2. Consider a segmented paging system with the segment table and the page table within a segment stored in memory. First part of the address is segment number, second part is the page number within a segment and the third part is the offset within a page. [40 points] a) If a memory reference takes 200 nano seconds, how long does a segmented page memory

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## This note was uploaded on 10/05/2010 for the course CIS CIS 3360 taught by Professor Guha during the Spring '10 term at University of Central Florida.

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CIS3360_HW7_Solution-4-28-09 - CIS 3360 Security in...

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