Re: [RFC 1/1] delay creation of initrd until end of rootfs install

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

On 18.01.24 17:44, Moessbauer, Felix (T CED OES-DE) wrote:
> On Fri, 2023-12-08 at 10:46 +0000, 'MOESSBAUER, Felix' via isar-users
> wrote:
>> On Wed, 2023-12-06 at 09:04 +0900, Jan Kiszka wrote:
>>> On 04.12.23 10:36, Felix Moessbauer wrote:
>>>> This patch solves major performance issues around the initramfs
>>>> creation by ensuring that the initrd is only created once. This
>>>> is
>>>> implemented by stubbing the update-initramfs call during the
>>>> package
>>>> installing. After all apt operations are completed, we manually
>>>> trigger the initrd creation. In case a custom initramfs is used,
>>>> the
>>>> creation is completely skipped in the image rootfs, as this would
>>>> anyways not be used.
>>>>
>>>> Before that, each package install that made a initrd relevant
>>>> change
>>>> triggered the update of the initrd. As we have multiple apt calls
>>>> during
>>>> the build, this step was sometimes executed multiple times. In
>>>> addition,
>>>> the apt install step is emulated, further slowing down the initrd
>>>> generation. On some layers on non native architecutes, this
>>>> summed
>>>> up to
>>>> over 10 minutes of initrd generation time.
>>>>
>>>> Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
>>>> ---
>>>>  meta/classes/image.bbclass                    |  4 +++
>>>>  meta/classes/rootfs.bbclass                   | 32
>>>> +++++++++++++++++++
>>>>  .../isar-bootstrap/isar-bootstrap.inc         |  2 ++
>>>>  3 files changed, 38 insertions(+)
>>>>
>>>> diff --git a/meta/classes/image.bbclass
>>>> b/meta/classes/image.bbclass
>>>> index 73f1d52c..39addc59 100644
>>>> --- a/meta/classes/image.bbclass
>>>> +++ b/meta/classes/image.bbclass
>>>> @@ -72,6 +72,8 @@ inherit essential
>>>>  
>>>>  ROOTFSDIR = "${IMAGE_ROOTFS}"
>>>>  ROOTFS_FEATURES += "clean-package-cache clean-pycache generate-
>>>> manifest export-dpkg-status clean-log-files clean-debconf-cache"
>>>> +# when using a custom initrd, do not generate one as part of the
>>>> image rootfs
>>>> +ROOTFS_FEATURES += "${@ '' if d.getVar('INITRD_IMAGE') == ''
>>>> else
>>>> 'no-generate-initrd'}"
>>>>  ROOTFS_PACKAGES += "${IMAGE_PREINSTALL}
>>>> ${@isar_multiarch_packages('IMAGE_INSTALL', d)}"
>>>>  ROOTFS_MANIFEST_DEPLOY_DIR ?= "${DEPLOY_DIR_IMAGE}"
>>>>  ROOTFS_DPKGSTATUS_DEPLOY_DIR ?= "${DEPLOY_DIR_IMAGE}"
>>>> @@ -488,6 +490,8 @@ do_rootfs_quality_check() {
>>>>      args="${ROOTFS_QA_FIND_ARGS}"
>>>>      # rootfs_finalize chroot-setup.sh
>>>>      args="${args} ! -path ${ROOTFSDIR}/var/lib/dpkg/diversions"
>>>> +    # initramfs is generated outside of the image rootfs
>>>> +    args="${args} ! -path ${ROOTFSDIR}/boot/initrd.img*"
>>>>      for cmd in ${ROOTFS_POSTPROCESS_COMMAND}; do
>>>>          case "${cmd}" in
>>>>             image_postprocess_mark)
>>>> diff --git a/meta/classes/rootfs.bbclass
>>>> b/meta/classes/rootfs.bbclass
>>>> index 1b95115a..69e38dac 100644
>>>> --- a/meta/classes/rootfs.bbclass
>>>> +++ b/meta/classes/rootfs.bbclass
>>>> @@ -14,6 +14,7 @@ ROOTFS_BASE_DISTRO ?= "${BASE_DISTRO}"
>>>>  # 'generate-manifest' - generate a package manifest of the
>>>> rootfs
>>>> into ${ROOTFS_MANIFEST_DEPLOY_DIR}
>>>>  # 'export-dpkg-status' - exports /var/lib/dpkg/status file to
>>>> ${ROOTFS_DPKGSTATUS_DEPLOY_DIR}
>>>>  # 'clean-log-files' - delete log files that are not owned by
>>>> packages
>>>> +# 'no-generate-initrd' - do not generate debian default initrd
>>>>  ROOTFS_FEATURES ?= ""
>>>>  
>>>>  ROOTFS_APT_ARGS="install --yes -o Debug::pkgProblemResolver=yes"
>>>> @@ -117,6 +118,16 @@ rootfs_configure_apt() {
>>>>  EOSUDO
>>>>  }
>>>>  
>>>> +ROOTFS_CONFIGURE_COMMAND += "rootfs_disable_initrd_generation"
>>>> +rootfs_disable_initrd_generation[weight] = "1"
>>>> +rootfs_disable_initrd_generation() {
>>>> +    # fully disable initrd generation
>>>> +    echo "replace update-initramfs with stub"
>>>> +    sudo mv "${ROOTFSDIR}/usr/sbin/update-initramfs" \
>>>> +            "${ROOTFSDIR}/usr/sbin/update-initramfs.isar"
>>>> +    sudo chroot "${ROOTFSDIR}" ln -s "/usr/bin/true"
>>>> "/usr/sbin/update-initramfs"
>>>> +}
>>>> +
>>>>  
>>>>  ROOTFS_INSTALL_COMMAND += "rootfs_install_pkgs_update"
>>>>  rootfs_install_pkgs_update[weight] = "5"
>>>> @@ -310,6 +321,27 @@ rootfs_cleanup_isar_apt() {
>>>>  EOSUDO
>>>>  }
>>>>  
>>>> +ROOTFS_POSTPROCESS_COMMAND += "rootfs_restore_initrd_tooling"
>>>> +rootfs_generate_initrd[weight] = "1"
>>>> +rootfs_restore_initrd_tooling() {
>>>> +    if [ -e "${ROOTFSDIR}/usr/sbin/update-initramfs.isar" ];
>>>> then
>>>> +        sudo mv -f "${ROOTFSDIR}/usr/sbin/update-initramfs.isar"
>>>> \
>>>> +            "${ROOTFSDIR}/usr/sbin/update-initramfs"
>>>> +    fi
>>>> +}
>>>> +
>>>> +ROOTFS_POSTPROCESS_COMMAND +=
>>>> "${@bb.utils.contains('ROOTFS_FEATURES', 'no-generate-initrd',
>>>> '',
>>>> 'rootfs_generate_initrd', d)}"
>>>> +rootfs_generate_initrd[weight] = "10"
>>>> +rootfs_generate_initrd() {
>>>> +    if [ -n "$(sudo find '${ROOTFSDIR}/boot' -type f -name
>>>> 'vmlinu[xz]*')" ]; then
>>>> +        sudo -E chroot "${ROOTFSDIR}" sh -c '\
>>>> +            export kernel_version=$(basename /boot/vmlinu[xz]* |
>>>> cut -d'-' -f2-); \
>>>> +            update-initramfs -u -v -k "$kernel_version";'
>>>> +    else
>>>> +        echo "no kernel in this rootfs, do not generate initrd"
>>>> +    fi
>>>> +}
>>>> +
>>>>  do_rootfs_postprocess[vardeps] = "${ROOTFS_POSTPROCESS_COMMAND}"
>>>>  do_rootfs_postprocess[network] = "${TASK_USE_SUDO}"
>>>>  python do_rootfs_postprocess() {
>>>> diff --git a/meta/recipes-core/isar-bootstrap/isar-bootstrap.inc
>>>> b/meta/recipes-core/isar-bootstrap/isar-bootstrap.inc
>>>> index 3477c2fb..4c6011bc 100644
>>>> --- a/meta/recipes-core/isar-bootstrap/isar-bootstrap.inc
>>>> +++ b/meta/recipes-core/isar-bootstrap/isar-bootstrap.inc
>>>> @@ -24,6 +24,8 @@ DISTRO_BOOTSTRAP_KEYFILES = ""
>>>>  THIRD_PARTY_APT_KEYFILES = ""
>>>>  DEPLOY_ISAR_BOOTSTRAP ?= ""
>>>>  DISTRO_BOOTSTRAP_BASE_PACKAGES = "locales"
>>>> +# install early, so we can stub the update-initramfs script
>>>> before
>>>> rootfs install
>>>> +DISTRO_BOOTSTRAP_BASE_PACKAGES:append = ",initramfs-tools"
>>>>  DISTRO_BOOTSTRAP_BASE_PACKAGES:append:gnupg = ",gnupg"
>>>>  DISTRO_BOOTSTRAP_BASE_PACKAGES:append:https-support = ",ca-
>>>> certificates"
>>>>  DISTRO_VARS_PREFIX ?= "${@'HOST_' if
>>>> d.getVar('BOOTSTRAP_FOR_HOST') == '1' else ''}"
>>>
>>> The idea is quite nice for us in Isar, though I'd also eventually
>>> like
>>> to improve Debian itself in this regard. The building blocks are
>>> there
>>> in upstream but they do not fully work.
>>
>> Yes, definitely. I reported this on the debian-kernel ML as well:
>> https://lists.debian.org/debian-kernel/2023/12/msg00097.html
>>
>> Anyways, are there more objections against this patch?
> 
> Any news on this? This is on the ML for quite some time without
> objections. If required, I can send a rebased version.
> 

I assume this is held back now by the current -rc cycle. Likely an
improvement after 0.10.

Jan

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