Handout 8 - Operating Systems

Handout 8 - Operating Systems - CIS 3360 Security in...

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CIS 3360 Security in Computing Spring 2010 Handout – Security in Operating System Scheduling Algorithms When a process arrives, it is allocated some memory as dictated by a scheduling algorithm. First Fit: The scheduler allocates the first hole that is big enough, so searching is fast and only in the worst case does the scheduler need to search the entire list of holes. Best Fit: The scheduler allocates the smallest hole that is big enough in order to minimize the unused space in each partition. In each case, the scheduler needs to look at the entire list of holes. Worst Fit: The scheduler allocates the largest available hole to the first process that arrives. Example: Given five memory partitions of 300 KB, 500 KB, 350 KB, 600 KB, and 200 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, 200 KB and 300KB (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? Answer: Size of Partition First Fit Best Fit Worst Fit 300KB 300 KB 300 KB 200 KB 500KB 350 KB 450 KB 450 KB 350KB 200 KB 350 KB 300 KB 600KB 450 KB 300 KB 350 KB 200KB 200 KB If we calculate the percentage of the memory that is not effectively utilized, we can see:
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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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Handout 8 - Operating Systems - CIS 3360 Security in...

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