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\documentclass[10pt,a4paper]{article}
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\title{Operating Systems - assignment 7}
\author{Camil Staps\\\small{s4498062}}
\begin{document}
\maketitle
\thispagestyle{fancy}
\section*{9.1}
\begin{enumerate}
\item See Table \ref{tab:91a}.
\begin{table}[h]
\centering
\footnotesize
\begin{tabular}{| r | *{21}{c|}} \hline
ms & 0 & 2 & 4 & 6 & 8 & 10 & 12 & 14 & 16 & 18 & 20 & 22 & 24 & 26 & 28 & 30 & 32 & 34 & 36 & 38 \\\hline
SPN & P1 & P1 & P2 & P2 & P2 & P2 & P2 & P2 & P4 & P4 & P4 & P3 & P3 & P3 & P3 & P5 & P5 & P5 & P5 & P5 \\\hline
SRT & P1 & P1 & P2 & P3 & P3 & P3 & P3 & P2 & P4 & P4 & P4 & P2 & P2 & P2 & P2 & P5 & P5 & P5 & P5 & P5 \\\hline
\end{tabular}
\caption{Applying the SPN and SRT algorithms to five processes}
\label{tab:91a}
\end{table}
\item See Table \ref{tab:91b}.
\begin{table}[h]
\centering
\footnotesize
\begin{tabular}{| r | *{4}{>{$}C{10mm}<{$} |}} \hline
& \multicolumn{2}{c|}{SPN} & \multicolumn{2}{c|}{SRT} \\\hline
Process & T_r & T_r/T_s & T_r & T_r/T_s \\\hline
P1 & 4 & 1 & 4 & 1 \\
P2 & 14 & 1.167 & 28 & 2.333 \\
P3 & 24 & 3 & 8 & 1 \\
P4 & 6 & 1 & 6 & 1 \\
P5 & 20 & 2 & 20 & 2 \\\hline
Mean & 13.2 & 1.633 & 13.2 & 1.467 \\\hline
\end{tabular}
\caption{TAT and relative delay for the processes from Table \ref{tab:91a}}
\label{tab:91b}
\end{table}
\end{enumerate}
\section*{9.6}
The diagram shows the situation where processes only move down to a lower priority queue when preempted. The first two time units allocated to A are actually two dispatches, each with time unit $2^0=1$. Then the process is preempted because of B and moves down the priority queues.
However, if we move a process down the priority queues any time it finishes a time unit, A will continue running for three consecutive time units. First, one time unit in RQ0, and then two in RQ1.
\section*{9.7}
A steep line typically corresponds to a low service time, while a more gentle line corresponds to a high service time. The response ratio of a process with a low service time increases faster than that of a process with a high service time. Therefore, we should schedule the processes with a high service time last. If we schedule them earlier, the response times of other jobs increase rapidly and over a long time (that is, the service time of the running job). If we first schedule processes with a short service time however, the other response ratios don't increase that rapidly (because they belong to processes with a higher service time), and not for such a long time.
\end{document}
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