\input{configpres}

\title{Linux Kernel}
\maketitle

\subsection{Basics}

\subsubsection{Facts}
\begin{frame}
\frametitle{Facts}
\begin{itemize}
\item Free Software (GPL Version 2)
\item Many different HW architectures and platforms are supported
\item Scales from supercomputers to embedded devices
\item Huge number of drivers
\item It's easy to add own drivers
\item Codequality is high
\item Quality is ensured by Code-Review of independent persons/organizations
\item Rapid development speed
\item Excellent network capabilities / performance
\item Simple Real-time concept
\end{itemize}
\end{frame}

\subsubsection{Linux 4.16-rc5 (03/2018)}

\begin{frame}[fragile]
\frametitle{Lines of code by language}
\begin{verbatim}
ansic:    16.686.769 (97.83%)
asm:         295.663  (1.73%)
perl:         26.424  (0.15%)
sh:           19.168  (0.11%)
python:       15.685  (0.09%)
cpp:           4.919  (0.03%)
yacc:          4.600  (0.03%)
lex:           2.478  (0.01%)
awk:           1.387  (0.01%)
pascal:          231  (0.00%)
sed:               5  (0.00%)
\end{verbatim}
\end{frame}

\begin{frame}[fragile]
\frametitle{Lines of code per folder}
\begin{verbatim}
11.134.588  drivers  66%  c=11.124.729 asm=  2.744
 2.073.368  arch     11%  c= 1.778.733 asm=290.614
   869.993  fs        5%  c=   869.993
   775.712  sound     5%  c=   775.712
   712.404  net       5%  c=   712.404
   540.702  include   3%  c=   538.568
   286.340  tools     2%  c=   253.768
                     python=    12.196
                         sh=    11.354
                       perl=     4.012
   191.741  kernel    2%  c=   191.741
   101.006  lib       1%  c=   100.874
    83.858  mm        1%  c=    83.858
    81.386  crypto    1%  c=    81.386
    59.271  security  1%  c=    59.271
\end{verbatim}
\end{frame}


\subsubsection{Architecture}

\begin{frame}
\frametitle{Subsystems}
\centering
\includegraphics[width=\textwidth]{images/linux-kernel-map.png}
\end{frame}


\begin{frame}
\frametitle{Drivers}
\centering
\includegraphics[width=0.8\textwidth]{images/Subsystems.png}
\end{frame}



\subsubsection{Maintainer}
\begin{frame}
\frametitle{Kernel Maintainer}
\begin{itemize}
\item Responsible for a driver, filesystem or subsystem
\pause
\item This includes new developments and bugfixes
\pause
\item Review of change requests
\pause
\item Accept/decline of change requests
\pause
\item Transfer of accepted changes / patches
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Made by real people}
\begin{itemize}
\item Meet developers / maintainers on conferences
\pause
\item Technical communication via email / mailinglists
\pause
\item Everyone can see who has developed the code
\pause
\item Code of Conduct
\end{itemize}
\end{frame}


\begin{frame}
\frametitle{Linus Torvalds}
\includegraphics[height=5cm]{images/linus7.jpg}

Maintains: THE REST

Company: linuxfoundation
\end{frame}

\begin{frame}
\frametitle{Alan Cox}
\includegraphics[height=5cm]{images/alan.png}

Credits: NET2Debugged/NET3 author, Network layer debugging, Initial AX.25 and
IPX releases, Original Linux netatalk patches, Current 3c501 hacker, Watchdog
timer drivers, Linux/SMP

Company: intel
\end{frame}

\begin{frame}
\frametitle{Andrew Morton}
\includegraphics[height=5cm]{images/morton.jpg}

Maintains: EXT3, JOURNALLING LAYER FOR BLOCK DEVICES (JBD)

Credits: Linux Quality Management

Company: Google
\end{frame}

\begin{frame}
\frametitle{Greg Kroah-Hartmann}
\includegraphics[height=5cm]{images/greg.jpg}

Maintains: SERIAL DRIVER, DRIVER CORE, KOBJECTS, DEBUGFS AND SYSFS, STABLE
BRANCH, STAGING SUBSYSTEM, TTY LAYER, USB SERIAL DRIVER, USB SUBSYSTEM,
USERSPACE I/O

Company: SuSE
\end{frame}

\begin{frame}
\frametitle{Christoph Hellwig}
\includegraphics[height=5cm]{images/hch.jpg}

Maintains: FREEVXFS FILESYSTEM, PERSONALITY HANDLING, SYSV FILESYSTEM, XFS
FILESYSTEM
Company: ??
\end{frame}

\begin{frame}
\frametitle{Thomas Gleixner}
\includegraphics[height=5cm]{images/tglx.jpg}

Maintains: HIGH-RESOLUTION TIMERS, CLOCKEVENTS, DYNTICKS, POSIX CLOCKS and
TIMERS, X86 ARCHITECTURE (32-BIT AND 64-BIT), PREEMPT RT

Company: linutronix
\end{frame}

\subsubsection{Development Process}
\begin{frame}
\frametitle{Development Process}
\begin{itemize}
\item Change requests are formulated as source-code patches
\pause
\item Review / technical discussion on Mailinglists
\item There are ML for the hole kernel and for several subsystems.
\pause
\item Documented and checkable Coding Style
\pause
\item Guidelines and tooling for checking and transfering patches
\item e.g. scripts/checkpatch.pl
\pause
\item Only technical arguments count.
\pause
\item MAINTAINER file in the source tree describes responsibilites
\end{itemize}
\end{frame}

\subsubsection{Versioning}
\begin{frame}
\frametitle{Versionierung (5.x)}
\begin{itemize}
\item 5.8.2 or 5.9-rc1
\pause
\item 5. - Historical defined (successor of 4.20, 3.19, 2.6.39)
\pause
\item .8 - Current version
\pause
\item .1 OR -rc1 - Security Fix OR Release Candidate
\end{itemize}
\end{frame}


\begin{frame}
\frametitle{Versioning (0.x \dots 1.3.x)}
\begin{itemize}
\item 09.91-02.94: 0.01\dots0.99 Follows no schema
\item 03.94-03.94: 1.0 1st stable kernel
\item 04.94-03.95: 1.1.x Developer Version
\item 03.95-08.95: 1.2.x Stable Kernel (added Alpha, MIPS, SPARC)
\item 06.95-05.96: 1.3.x Developer Version (added MP Support)
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Versionierung (2.0.x \dots 4.x)}
\begin{itemize}
\item 06.96-02.04: 2.0.x SMP Support
\item 09.96-01.99: 2.1.x Developer Version
\item 01.99-02.04: 2.2.x Stable Kernel, IPv6
\item 05.99-05.00: 2.3.x Developer Version
\item 01.01-12.08: 2.4.x Stable Kernel, USB, ACPI, iptables
\item 11.01-07.03: 2.5.x Developer Version
\item 12.03-TODAY: 2.6.x, 3.x, 4.x, 5.x New schema
\end{itemize}
Version Boundaries
\begin{itemize}
\item 05.11: 2.6.39\dots3.0
\item 02.15: 3.19\dots4.0
\item 01.19: 4.20\dots5.0
\end{itemize}
\end{frame}

\begin{frame}
\includegraphics[height=6cm]{images/kernelversions.png}

Source: http://article.sapub.org
\end{frame}


\subsubsection{Development Speed}
\begin{frame}
\frametitle{Linux 5.x}
\begin{itemize}
\item 8 \dots 10 weeks release cycle
\item \dots about 14,000 patches each cycle
\item \dots from about 1500 developers
\item \dots about 200 companies
\end{itemize}
\end{frame}

\begin{frame}
\includegraphics[height=6cm]{images/patches_per_hour.png}

Source: https://github.com/gregkh/kernel-development
\end{frame}

\begin{frame}
\includegraphics[height=6cm]{images/linux-kernel-development-companies.png}

Source: https://fossbytes.com
\end{frame}


\subsubsection{staging and next}
\begin{frame}
\frametitle{staging}
\begin{itemize}
\item Directory inside the Kernel source tree
\pause
\item Allows development in 'Mainline'
\pause
\item Mainly used for driver development
\pause
\item Requirement: active development
\end{itemize}
\end{frame}

\begin{frame}[fragile]
\frametitle{next}
\begin{itemize}
\item Changes considered to be merged into the next Kernel version
\item Tracks several git trees and quilt queues
\end{itemize}
\begin{lstlisting}
Feb-2008, Stephen Rothwell:
I hope to recreate this tree every day automatically.
In order to do this, any tree that has a conflict will
be dropped from that days tree.
The maintainer will be notified. I hope to provide some
clue as to what the conflict is with, but probably not
initially. I will attempt to build the tree between each
merge (and a failed build will again cause the offending
tree to be dropped). These builds will be necessarily
restricted to probably one architecture/config.
\end{lstlisting}
\end{frame}

\subsubsection{Configuration}
\begin{frame}[fragile]
\frametitle{Kernel configuration}
\begin{itemize}
\item Huge number of configuration options
\pause
\item Stored in a .config file
\pause
\item Changing configuration: make menuconfig
\pause
\item Information about options are stored in Kconfig files
\end{itemize}
\end{frame}

\input{tailpres}
