[bootlin/training-materials updates] master: Boot-time labs: kernel and bootloader optimization updates (7d18c420)
Michael Opdenacker
michael.opdenacker at bootlin.com
Mon May 2 07:24:33 CEST 2022
Repository : https://github.com/bootlin/training-materials
On branch : master
Link : https://github.com/bootlin/training-materials/commit/7d18c4204352586932588122058cc96f9a1ca665
>---------------------------------------------------------------
commit 7d18c4204352586932588122058cc96f9a1ca665
Author: Michael Opdenacker <michael.opdenacker at bootlin.com>
Date: Mon May 2 07:24:33 2022 +0200
Boot-time labs: kernel and bootloader optimization updates
Signed-off-by: Michael Opdenacker <michael.opdenacker at bootlin.com>
>---------------------------------------------------------------
7d18c4204352586932588122058cc96f9a1ca665
labs/boot-time-bootloader/boot-time-bootloader.tex | 64 ++++------------------
labs/boot-time-kernel/boot-time-kernel.tex | 8 ++-
2 files changed, 19 insertions(+), 53 deletions(-)
diff --git a/labs/boot-time-bootloader/boot-time-bootloader.tex b/labs/boot-time-bootloader/boot-time-bootloader.tex
index 643f8b57..f08434e6 100644
--- a/labs/boot-time-bootloader/boot-time-bootloader.tex
+++ b/labs/boot-time-bootloader/boot-time-bootloader.tex
@@ -2,54 +2,15 @@
In this lab, we will run the final stage of boot time reduction:
\begin{itemize}
-\item Improving the efficiency of the bootloader by optimizing its
-usage
-\item Recompiling the bootloader with the minimum set of options,
-and even completely skip the second stage of the bootloader.
+\item Improving the efficiency of the bootloader by using faster storage
+\item Configuring the bootloader so that it's second stage can be
+skipped ({\em Falcon mode} in U-Boot).
\end{itemize}
\section{Optimizing U-Boot usage}
-By following the indications given in the lectures, start by optimizing
-the way U-Boot is used.
-
-At last, you can start by eliminating the infamous 2-second boot delay, something
-you've surely been longing to do.
-
-\section{Recompiling the bootloader}
-
-It's now time to eliminate useless features in U-Boot. Go to
-\code{~/boot-time-labs/bootloader/u-boot/} and run \code{make
-menuconfig} to unselect features that we don't need in our system.
-
-For the moment, don't touch the \code{SPL / TPL} options, as we will try
-to use U-Boot's Falcon mode at the end.
-
-In the same way you did when you reduced the kernel configuration,
-do the changes {\bf progressively}, and even make backup copies of your
-intermediate configurations (\code{.config} file). You will be glad you
-did when you break U-Boot.
-
-Once you have reached the minimum set of features, please measure boot
-time and fill the below table:
-
-\begin{tabular}{| l | l | r |}
- \hline
- Step & Duration & Description \\
- \hline
- \hline
- U-Boot SPL & & Between \code{U-Boot SPL 2022.04} and \code{U-Boot 2022.04} \\
- \hline
- U-Boot & & Between \code{U-Boot 2022.04} and \code{Starting kernel} \\
- \hline
- Kernel + Init scripts & & Between \code{Starting kernel} and \code{Starting ffmpeg} \\
- \hline
- Application & & Between \code{Starting ffmpeg} and \code{First frame decoded} \\
- \hline
- \hline
- Total & & \\
- \hline
-\end{tabular}
+Here, we won't try to optimize U-Boot, because we are ultimately
+going to skip its second stage. We could, but we don't need to.
\section{Using faster storage}
@@ -123,9 +84,8 @@ Copy this \code{uImage} file to your SD card boot partition.
We also need a few features to be enabled in the U-Boot SPL. So start
U-Boot's \code{make menuconfig}:
\begin{itemize}
-\item In the \code{Environment menu}, unselect \code{SPL environment is
- not stored} (\projconfigval{u-boot}{CONFIG_SPL_ENV_IS_NOWHERE}{n}), and
- select \code{SPL Environment is in a FAT filesystem}
+\item In the \code{Environment menu}, make sure that
+ \code{SPL Environment is in a FAT filesystem} is selected
(\projconfigval{u-boot}{CONFIG_SPL_ENV_IS_IN_FAT}{y}). This way, we
can have a \code{boot_os} environment variable that if set to
\code{yes}, will allow to boot Linux directly. See the
@@ -173,20 +133,20 @@ tells you where the exported data were stored in RAM:
\begin{verbatim}
## Booting kernel from Legacy Image at 82000000 ...
- Image Name: Linux-5.11.11-dirty
- Created: 2021-04-13 9:48:35 UTC
+ Image Name: Linux-5.15.34-dirty
+ Created: 2022-04-29 17:47:56 UTC
Image Type: ARM Linux Kernel Image (uncompressed)
- Data Size: 2842016 Bytes = 2.7 MiB
+ Data Size: 3008496 Bytes = 2.9 MiB
Load Address: 80008000
Entry Point: 80008000
Verifying Checksum ... OK
## Flattened Device Tree blob at 88000000
Booting using the fdt blob at 0x88000000
Loading Kernel Image
- Loading Device Tree to 8ffec000, end 8ffff3ff ... OK
+ Loading Device Tree to 8ffec000, end 8ffffce6 ... OK
subcommand not supported
subcommand not supported
- Loading Device Tree to 8ffd5000, end 8ffeb3ff ... OK
+ Loading Device Tree to 8ffd5000, end 8ffebce6 ... OK
Argument image is now in RAM: 0x8ffd5000
WARN: FDT size > CMD_SPL_WRITE_SIZE
\end{verbatim}
diff --git a/labs/boot-time-kernel/boot-time-kernel.tex b/labs/boot-time-kernel/boot-time-kernel.tex
index 87301f2a..518e66d3 100644
--- a/labs/boot-time-kernel/boot-time-kernel.tex
+++ b/labs/boot-time-kernel/boot-time-kernel.tex
@@ -130,6 +130,12 @@ system\footnote{Here we have a very specific system and we don't have
to support programs that could be added in the future and could need
more kernel features}.
+You can even try to remove support for the \code{proc} and \code{sysfs}
+filesystems, as we're not mounting them anyway. Surprisingly, at least
+in our application and kernel, you'll see that the application doesn't
+work if the \code{proc} filesystem is not compiled in. Let's keep that
+one!
+
At the end, you can disable \kconfig{CONFIG_PRINTK}, and observe your
total savings in terms of kernel size and boot time.
@@ -194,7 +200,7 @@ works with \code{zImage} files):
\begin{verbatim}
sudo apt install u-boot-tools
mkimage -A arm -O linux -C none -T kernel -a 80008000 -e 80008000 \
- -n 'Linux-5.11.11' -d arch/arm/boot/Image arch/arm/boot/uImage
+ -n 'Linux-5.15' -d arch/arm/boot/Image arch/arm/boot/uImage
\end{verbatim}
Then, in U-Boot, you will have to boot it with \code{bootm} instead of
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