Scheduling algorithms
HW#2:
1) Given that main memory is composed of only three page frames for public use and that a
seven-page program (with pages a, b, c, d, e, f, g) that requests pages in the following
order:
a, b, c, b, d, a, e, f, b, e, d, f
a. Using the FIFO page removal algorithm, indicate the movement of the pages into and out of the available page frames (called a page trace analysis) indicating each page fault with an asterisk (*). Then compute the failure ratio and success ratio.
b. Using FIFO again, increase the size of memory so it contains four page frames for public use. Using the same page requests as above, do another page trace analysis and compute the failure and success ratios.
2. Given the following Segment Map Tables for two jobs:
SMT for Job 1
Segment Number Memory Location
0 4096
1 6144
2 9216
3 2048
4 7168
SMT for Job 2
Segment Number Memory Location
0 2048
1 6144
2 9216
a. Which segments, if any, are shared between the two jobs?
b. If the segment now located at 7168 is swapped out and later reloaded at 8192, and the segment now at 2048 is swapped out and reloaded at 1024, what would the new segment tables look like?
3) Five jobs arrive nearly simultaneously for processing and their estimated CPU cycles are,
respectively: Job A = 2 ms, Job B = 12 ms, Job C = 15 ms, Job D = 7 ms, and Job E = 3 ms.
a. Using FCFS, in what order would they be processed? What is the total time required to
process all five jobs? What is the average turnaround time for each of these five jobs?
b. Using SJN, and assuming that all jobs are present when the algorithm begins, in what
order would they be processed? What is the total time required to process all five jobs? What is the average turnaround time for all five jobs?
c. Using SJN, and assuming that all jobs are present when the algorithm begins, what is the average turnaround time for all five jobs using these speeds: Job A = 12 ms, Job B = 2 ms, Job C = 15 ms, Job D = 7 ms, and Job E = 3 ms.
4. Given the following information:
Job Arrival
Time
CPU
Cycle
A 0 15
B 2 2
C 3 14
D 6 10
E 10 2
a) Calculate which jobs will have arrived ready for processing by the time the first job is finished or is first interrupted. Do your calculation using each of the following scheduling algorithms.
1. FCFS
2. SJN
3. SRT
4. Round Robin (use a time quantum of 5, but ignore the time required for context switching and natural wait).
b) compute the turnaround time for every job using each of the following scheduling algorithms (ignoring context switching overhead times).
a. FCFS
b. SJN
c. SRT
d. Round robin (using a time quantum of 5)
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