Re: [PATCH v2] linux-custom: Speedup build of target specific linux-kbuild package

[Jan Kiszka <jan.kiszka@siemens.com>]

On 07.06.24 16:11, Stefan Koch wrote:
> Avoids time expensive QEMU-emulated merging of kernel config by using
> the existing kernel config for the target specific linux-kbuild
> 
> Using DEPENDS instead of RDEPENDS ensures creation of
> kernel (including config) before build of target specific linux-kbuild
> 
> Signed-off-by: Stefan Koch <stefan-koch@siemens.com>
> ---
>  .../linux/files/debian/isar/configure.tmpl     | 18 ++++++++++++++----
>  meta/recipes-kernel/linux/linux-custom.inc     | 10 +++++++---
>  2 files changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/meta/recipes-kernel/linux/files/debian/isar/configure.tmpl b/meta/recipes-kernel/linux/files/debian/isar/configure.tmpl
> index 389c9a85..72eae448 100644
> --- a/meta/recipes-kernel/linux/files/debian/isar/configure.tmpl
> +++ b/meta/recipes-kernel/linux/files/debian/isar/configure.tmpl
> @@ -10,10 +10,20 @@ do_configure() {
>      # Trace what we do here
>      set -x
>  
> -    # Process kernel config target and fragments
> -    ${MAKE} O=${KERNEL_BUILD_DIR} ${KERNEL_CONFIG_TARGET}
> -    ./scripts/kconfig/merge_config.sh -O ${KERNEL_BUILD_DIR}/ \
> -        ${KERNEL_BUILD_DIR}/.config ${KERNEL_CONFIG_FRAGMENTS}
> +    kernelconfig="$(find /boot -maxdepth 1 -name "config-${PV}*" -print -quit)"

Can we additionally limit this to the case were we expect the config
there (kbuild && !kernel)? Just to reduce the risk that some "this
should never be there" config is ever silently pulled by the base
package build. Only if our dependency is installed, that rather generic
config-<version> file is from there, or we failed on installing the
dependency.

> +    if [ -e "${kernelconfig}" ]; then
> +        # Prefer existing kernel config
> +        # So, very expensive QEMU-emulated merge_config.sh
> +        # can be skipped for target specific linux-kbuild package
> +        mkdir -p ${KERNEL_BUILD_DIR}
> +        cp "${kernelconfig}" ${KERNEL_BUILD_DIR}/.config
> +        ${MAKE} O=${KERNEL_BUILD_DIR} olddefconfig
> +    else
> +        # Process kernel config target and fragments
> +        ${MAKE} O=${KERNEL_BUILD_DIR} ${KERNEL_CONFIG_TARGET}
> +        ./scripts/kconfig/merge_config.sh -O ${KERNEL_BUILD_DIR}/ \
> +            ${KERNEL_BUILD_DIR}/.config ${KERNEL_CONFIG_FRAGMENTS}
> +    fi
>  
>      # Stop tracing
>      set +x
> diff --git a/meta/recipes-kernel/linux/linux-custom.inc b/meta/recipes-kernel/linux/linux-custom.inc
> index 647f09dd..dc354e13 100644
> --- a/meta/recipes-kernel/linux/linux-custom.inc
> +++ b/meta/recipes-kernel/linux/linux-custom.inc
> @@ -25,6 +25,7 @@ KBUILD_DEPENDS ?= "build-essential:native, \
>                     flex, \
>                     git, \
>                     kmod, \
> +                   linux-image-${KERNEL_NAME_PROVIDED}:${DISTRO_ARCH} <kbuild !kernel>, \
>                     rsync,"
>  
>  KERNEL_DEBIAN_DEPENDS ?= "initramfs-tools | linux-initramfs-tool, \
> @@ -112,7 +113,7 @@ BUILD_PROFILES = "kernel kbuild"
>  BBCLASSEXTEND:append:cross-profile = " kbuildtarget"
>  
>  # When cross-profile is active:
> -# build only kernel with the default variant of the recipe
> +# build only kernel (including config) with the default variant of the recipe
>  BUILD_PROFILES:cross-profile = "kernel"
>  
>  # -native: kbuild package for host
> @@ -122,14 +123,17 @@ RECIPE_PROVIDES:class-native = " \
>      linux-kbuild-${KERNEL_NAME_PROVIDED}"
>  # Use pseudo target to pull in the base variant of the recipe.
>  # Will be auto-extended with -native by multiarch.bbclass.
> -RDEPENDS:class-native += "${BPN}-pseudo"
> +# Using DEPENDS, see below
> +DEPENDS:class-native += "${BPN}-pseudo"

Need to help me with remember my own code: Why do we also need this
build dependency? I thought you are only optimizing the kbuildtarget case.

>  
>  # -kbuildtarget: kbuild package for target, enforcing non-cross-build
>  BUILD_PROFILES:class-kbuildtarget = "kbuild"
>  RECIPE_PROVIDES:class-kbuildtarget = " \
>      linux-headers-${KERNEL_NAME_PROVIDED} \
>      linux-kbuild-${KERNEL_NAME_PROVIDED}"
> -RDEPENDS:class-kbuildtarget = "${BPN}"
> +# Using DEPENDS instead of RDEPENDS to ensure creation of kernel including
> +# pregenerated kernel config before target specific linux-kbuild package build
> +DEPENDS:class-kbuildtarget = "${BPN}"
>  ISAR_CROSS_COMPILE:class-kbuildtarget = "0"
>  
>  # Make bitbake know we will be producing linux-image and linux-headers packages

Fine-tuning - this generally looks like a nice optimization now!

Jan

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