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\begin{document}
\hrule \medskip
\begin{minipage}{0.295\textwidth} 
    \raggedright
    \footnotesize 
    \begin{tabular}{@{}l l}
        Name: & Andrew Hayes \\
        Student ID: & 21321503 \\
        E-mail: & \href{mailto://a.hayes18@universityofgalway.ie}{\texttt{a.hayes18@universityofgalway.ie}} \\
    \end{tabular}
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    \textsc{ct420} \\ 
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    \today
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\begin{center}
    \normalsize
    Assignment 2: POSIX Programming \& Benchmarking
\end{center}
\hrule
\medskip

\section{Host Environment}
For my host environment, I chose to run Ubuntu Server 24.04.2 LTS using a VirtualBox hypervisor.
I chose this operating system as I have sufficient Linux experience to feel confident using an operating system with no graphical interface (as opposed to Ubuntu Desktop), and the absence of a GUI means a smaller ISO file, memory footprint, \& CPU footprint.
I chose Ubuntu specifically because it's a Linux system with which I have previous experience, and is well-document with plenty of packages available to install if needs be.
Ubuntu also makes it easy to install the \verb|PREEMPT_RT| patches, which transform the standard Linux kernel into a fully preemptible, real-time kernel, which I felt was more suitable for this assignment, as the standard Linux kernel is not suitable for a hard real-time system due to its lack of preemption.

\begin{figure}[H]
    \centering
    \includegraphics[width=\textwidth]{./images/hardware.png}
    \caption{Virtual machine hardware configuration}
\end{figure}

I set the virtual machine to have a single CPU and set the amount of RAM to 2048MB which is the recommended minimum for Ubuntu Server\supercite{ubuntu_server_installation}.
I left the hard disk size at the default of 25GB as I saw no reason to change it.
The real-time kernel with the \verb|PREEMPT_RT| patches installed is available with Ubuntu Pro, which is free for personal use.
After setting up an Ubuntu Pro account, I enabled the real-time kernel using the \mintinline{bash}{pro} command.

\begin{figure}[H]
    \centering
    \includegraphics[width=\textwidth]{./images/proenable.png}
    \caption{Enabling the real-time kernel with the \mintinline{bash}{pro} command}
\end{figure}

Finally, I transferred over the following C file (taken from the lecture slides) via \mintinline{shell}{scp} to the virtual machine to get the clock resolution, which is 1 nanosecond:
\begin{code}
\begin{minted}[linenos, breaklines, frame=single]{C}
#include<unistd.h>
#include<time.h>
#include <stdio.h>

int main(){
    struct timespec clock_res;
    int stat;
    stat=clock_getres(CLOCK_REALTIME, &clock_res);
    printf("Clock resolution is %d seconds, %ld nanoseconds\n",clock_res.tv_sec,clock_res.tv_nsec);
    return 0;
}
\end{minted}
\end{code}

\begin{figure}[H]
    \centering
    \includegraphics[width=\textwidth]{./images/clockres.png}
    \caption{Getting the clock resolution of the virtual machine}
\end{figure}

\section{CPU \& Data-Intensive Applications}
To develop my CPU \& data-intensive programs, I chose to use Python for ease of development (and because any Python program will stress your CPU \& memory no matter how simple {\emojifont 😉}).
I chose \mintinline{shell}{htop} as my resource-monitoring tool as I have often used it in the past, it has easy to read \& understand output, and shows you exactly what proportion of the CPU \& memory is in use at that time.
It also allows you to list processes by CPU consumption or memory consumption which is a useful option to have for this assignment.

\begin{code}
\inputminted[linenos, breaklines, frame=single]{python}{../code/stressers/stress_cpu.py}
\caption{\texttt{stress\_cpu.py}}
\end{code}

\begin{figure}[H]
    \centering
    \includegraphics[width=\textwidth]{./images/medcpuload.png}
    \caption{\mintinline{python}{htop} output when running \mintinline{shell}{python3 stress_cpu.py --load medium}}
\end{figure}

\begin{figure}[H]
    \centering
    \includegraphics[width=\textwidth]{./images/highcpuload.png}
    \caption{\mintinline{python}{htop} output when running \mintinline{shell}{python3 stress_cpu.py --load high}}
\end{figure}

\begin{code}
\inputminted[linenos, breaklines, frame=single]{python}{../code/stressers/stress_memory.py}
\caption{\texttt{stress\_memory.py}}
\end{code}

\begin{figure}[H]
    \centering
    \includegraphics[width=\textwidth]{./images/memstress.png}
    \caption{\mintinline{python}{htop} output when running \mintinline{shell}{python3 stress_memory.py --usage 0.85}}
\end{figure}

\printbibliography
\end{document}