Question $4$: CPU Scheduling Implementation

Round Robin:

Expectations:

$-$ Average Run Time: Will decrease with more CPUs implemented. This is because multiple processes can be concurrently executed. This reduces the time each process spends waiting for time in CPU.

$-$ Wait Time: High with $1$ CPU, decreases with more implemented. This is because more processes can be handled at the same time.

$-$ Sleep time: With more CPUs, sleep time should increase as I$/$O$-$bound processes will get more frequent access to the CPU.

Testing: SCHEDULER$=$RR $($schedtest$)$

CPUS$=1$: Average run$-$time $=21,$ wait time $=165,$ sleep time $=20$

CPUS$=2$: Average run$-$time $=18,$ wait time $=56,$ sleep time $=79$

CPUS$=3$: Average run$-$time $=15,$ wait time $=35,$ sleep time $=87$

First$-$Come$-$First$-$Served:

Expectations:

$-$ Average Run Time: Will decrease with more CPUs implemented. More processes can be simultaneously scheduled when more CPUs are available.

$-$ Wait Time: High with $1$ CPU, decreases with more implemented. With $1$ CPU, tends to be lower compared with Round Robin.

$-$ Sleep time: Should remain constant, regardless of how many CPUs are available. This is because processes can run without preemption.

Testing: SCHEDULER$=$FCFS $($schedtest$)$

CPUS$=1$: Average run$-$time $=21,$ wait time $=43,$ sleep time $=100$

CPUS$=2$: Average run$-$time $=12,$ wait time $=26,$ sleep time $=100$

CPUS$=3$: Average run$-$time $=10,$ wait time $=20,$ sleep time $=100$

Priority:

Expectations:

$-$ Average Run Time: With more CPUs, should increase as the scheduler can execute many high$-$priority processes simultaneously.

$-$ Wait Time: As more CPUs are implemented, the wait time should decrease. This is because lower$-$priority processes will have more opportunity to be scheduled.

$-$ Sleep time: May show variation with more CPUs as the system can schedule I$/$O$-$bound processes more effectively.

Testing: SCHEDULER$=$PRIORITY $($schedtest$2)$

CPUS$=1$: Average run$-$time $=21,$ wait time $=150,$ sleep time $=100$

CPUS$=2$: Average run$-$time $=13,$ wait time $=66,$ sleep time $=58$

CPUS$=3$: Average run$-$time $=10,$ wait time $=39,$ sleep time $=79$

$($a$)$ Comparing these average timings you have obtained, are they what you would

expect?

$($b$)$ Provide justifications for your answer to $($a$)$ above.