[bootlin/training-materials updates] master: Boot time: add slide about Zstd (d9060938)

[Thomas Petazzoni]

Repository : https://github.com/bootlin/training-materials
On branch  : master
Link       : https://github.com/bootlin/training-materials/commit/d9060938ecfb3e2a14dfdd4453f25c68117e519e

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

commit d9060938ecfb3e2a14dfdd4453f25c68117e519e
Author: Michael Opdenacker <michael.opdenacker at bootlin.com>
Date:   Fri Oct 22 12:08:11 2021 +0200

    Boot time: add slide about Zstd
    
    Signed-off-by: Michael Opdenacker <michael.opdenacker at bootlin.com>


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

d9060938ecfb3e2a14dfdd4453f25c68117e519e
 slides/boot-time-kernel/boot-time-kernel.tex | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/slides/boot-time-kernel/boot-time-kernel.tex b/slides/boot-time-kernel/boot-time-kernel.tex
index 3f79407c..ebfc85a3 100644
--- a/slides/boot-time-kernel/boot-time-kernel.tex
+++ b/slides/boot-time-kernel/boot-time-kernel.tex
@@ -147,6 +147,33 @@ Lzo and Gzip seem the best solutions. Always benchmark as the results
 depend on storage and CPU performance.
 \end{frame}
 
+\begin{frame}[fragile]
+\frametitle{Compressing the kernel with Zstandard}
+\begin{itemize}
+  \item Zstandard is a relatively recent compression scheme, implemented
+        by Yann Collet.
+  \item Unfortunately, not available on ARM yet.\\
+        Only on x86, mips and s390 (Linux 5.15 status).
+  \item Compressing better than gzip and decompressing as fast as LZO,
+        it could be the best option.
+  \item See \url{https://en.wikipedia.org/wiki/Zstandard}
+\end{itemize}
+\begin{block}{}
+\small
+\begin{verbatim}
+config KERNEL_ZSTD
+        bool "ZSTD"
+        depends on HAVE_KERNEL_ZSTD
+        help
+          ZSTD is a compression algorithm targeting intermediate compression
+          with fast decompression speed. It will compress better than GZIP and
+          decompress around the same speed as LZO, but slower than LZ4. You
+          will need at least 192 KB RAM or more for booting. The zstd command
+          line tool is required for compression.
+\end{verbatim}
+\end{block}
+\end{frame}
+
 \begin{frame}
 \frametitle{Optimize kernel for size (1)}
 \begin{itemize}