Q$2.($a$)$ Suppose that we have a multi$-$programming uni$-$processor computer in which

each job has identical characteristics. In one computation period, $T,$ for a job,

the first and third quarters of the time are spent in processor and the second

quarter and fourth quarter in I$/$O activity, respectively. Each job runs for a total

of four periods. Assume that simple round$-$robin scheduling is used, and that

I$/$O operations can overlap with processor operation. Assume there are three

concurrent jobs arrive at $t=0.$

$($i$)$ Compute the turnaround time of each job.

$(6$ marks$)$

$($ii$)$ Compute the average throughput of three jobs.

$(2$ marks$)$

$($iii$)$ Compute the percentage of processor utilization.

$(2$ marks$)$

$($b$)$ This question is about the Completely Fair Scheduler $($CFS$)$ found in Linux

kernel. Assume that the system has a uni$-$processor with a red$-$black tree. There

are three CPU$-$bound processes in Ready state; $A,B,$ and $C$ with the following

parameters in Table $1$:

Table $1$

The minimum virtual runtime of the red$-$black tree is $2,297,543$ nanoseconds,

the period is set at $20$ milliseconds and the scheduler needs to decide which

process to execute. Using the guide provided in Appendix $1,$ answer the

following questions:

$($i$)$ Briefly describe the main objective that CFS tries to achieve. $(3$ marks$)$

$($ii$)$ In what order processes $A,B,$ and $C$ will execute within a period? Briefly

provide your reason.

$(4$ marks$)$

$($iii$)$ What are the virtual runtimes of processes $A,B,$ and $C$ after they execute

for one period?

$(6$ marks$)$

$($iv$)$ What nice value shall you set if you were to make Process A the highest

priority among Process $A,B$ and $C?$

$(2$ marks$)$help