[FE training-materials-updates] Boot time slides: benchmark data about initramfs compression

[Michael Opdenacker]

Repository : git://git.free-electrons.com/training-materials.git

On branch  : master
Link       : http://git.free-electrons.com/training-materials/commit/?id=4e0c4e6c5d23d5f8d877521b048502f908db3508

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

commit 4e0c4e6c5d23d5f8d877521b048502f908db3508
Author: Michael Opdenacker <michael.opdenacker at free-electrons.com>
Date:   Wed Jan 1 07:56:42 2014 +0100

    Boot time slides: benchmark data about initramfs compression
    
    Signed-off-by: Michael Opdenacker <michael.opdenacker at free-electrons.com>


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4e0c4e6c5d23d5f8d877521b048502f908db3508
 .../boottime-init-scripts3.tex                     |   20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/slides/boottime-init-scripts3/boottime-init-scripts3.tex b/slides/boottime-init-scripts3/boottime-init-scripts3.tex
index 9c9ac93..328333b 100644
--- a/slides/boottime-init-scripts3/boottime-init-scripts3.tex
+++ b/slides/boottime-init-scripts3/boottime-init-scripts3.tex
@@ -11,8 +11,6 @@ application and then switch to the final root filesystem with
 \item Use statically linked applications (less CPU overhead, less
       libraries to load, smaller initramfs if no libraries at all).
       \code{BR2_PREFER_STATIC_LIB} in Buildroot.
-\item Don't compress your initramfs if your kernel is already
-      compressed.
 \end{itemize}
 \end{frame}
 
@@ -43,6 +41,24 @@ application and then switch to the final root filesystem with
 \end{frame}
 
 \begin{frame}
+\frametitle{Do not compress your initramfs}
+\begin{itemize}
+\item If you ship your initramfs inside a compressed kernel image, don't compress
+      it \\
+      (enable \code{CONFIG_INITRAMFS_COMPRESSION_NONE}).
+\item Otherwise, your initramfs data will be compressed twice, and
+      the kernel will be slightly bigger and will take a little more time to uncompress. 
+\item Tests on Linux 3.13-rc4, measuring the penalty of having a
+      \code{gzip} compressed initramfs in a \code{gzip} compressed kernel: 
+      \begin{itemize}
+      \item CALAO USB-A9263 (Atmel AT91SAM9263): +18 ms
+      \item Beagle Bone Black (TI AM3359): +11 ms
+      \end{itemize}
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}
 \frametitle{Results: after switch to initramfs}
 Before: 9.67s
 \begin{center}