[bootlin/training-materials updates] master: boot-time slides: kernel: add advice slide (a13502ab)

[Michael Opdenacker]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/a13502abf9cbb621b658383f740ea72a6821454e

>---------------------------------------------------------------

commit a13502abf9cbb621b658383f740ea72a6821454e
Author: Michael Opdenacker <michael.opdenacker at bootlin.com>
Date:   Thu Jun 15 11:09:47 2023 +0200

    boot-time slides: kernel: add advice slide
    
    Signed-off-by: Michael Opdenacker <michael.opdenacker at bootlin.com>


>---------------------------------------------------------------

a13502abf9cbb621b658383f740ea72a6821454e
 slides/boot-time-kernel/boot-time-kernel.tex | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/slides/boot-time-kernel/boot-time-kernel.tex b/slides/boot-time-kernel/boot-time-kernel.tex
index cf679d0f..74af2dd8 100644
--- a/slides/boot-time-kernel/boot-time-kernel.tex
+++ b/slides/boot-time-kernel/boot-time-kernel.tex
@@ -1,5 +1,30 @@
 \section{Kernel optimizations}
 
+\begin{frame}
+\frametitle{Advice for kernel optimizations}
+	\small
+	\begin{itemize}
+	\item During these tests, you will make countless kernel updates, and will
+	      have to test them on the hardware to make sure nothing is broken.
+	\item During this phase, we recommend to switch to loading the kernel through
+	      the network (\code{tftp}) if possible. This will save a lot of time
+	      compared to updating the kernel on the SD card, and reduces the risk
+	      to damage your SD card reader.
+	\item Loading the kernel through the network will introduce delays and jitter,
+	      but that won't be an issue:
+	      \begin{itemize}
+	      \item In the cases when what you measure is kernel size reduction, just
+		    making sure each new kernel is still functional.
+	      \item If you want to measure the boot time impact of your changes,
+		    you can still start counting time from the \code{Starting kernel}
+		    message.
+	      \end{itemize}
+	\item Make kernel configuration changes {\bf very progressively} and keep
+	      manual snapshots of each configuration. This will help when a change
+	      breaks a working kernel.
+	\end{itemize}
+\end{frame}
+
 \begin{frame}[fragile]
 \frametitle{Measure - Kernel initialization functions}
 To find out which kernel initialization functions are the longest to