[PATCH 1/2] delay creation of initrd until end of rootfs install

["'Felix Moessbauer' via isar-users" <isar-users@googlegroups.com>]

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. We further unify the initrd generation in the
rootfs and in the initramfs class.

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 a test build of the RPi4b target with a detached initramfs and a
distro kernel, this patch set reduced the build time form ~50min to
~15min.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
---
 meta/classes/image.bbclass                    | 17 ++---
 meta/classes/initramfs.bbclass                | 39 +----------
 meta/classes/rootfs.bbclass                   | 66 ++++++++++++++++++-
 .../sbuild-chroot/sbuild-chroot.inc           |  1 +
 4 files changed, 72 insertions(+), 51 deletions(-)

diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index ff3cd737..8523a662 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -67,6 +67,8 @@ 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 ?= "${DEPLOY_DIR_IMAGE}"
@@ -341,17 +343,6 @@ do_copy_boot_files() {
         sudo cat "$kernel" > "${DEPLOYDIR}/${KERNEL_IMAGE}"
     fi
 
-    if [ -z "${INITRD_IMAGE}" ]; then
-        # deploy default initrd if no custom one is build
-        initrd="$(realpath -q '${IMAGE_ROOTFS}/initrd.img')"
-        if [ ! -f "$initrd" ]; then
-            initrd="$(realpath -q '${IMAGE_ROOTFS}/boot/initrd.img')"
-        fi
-        if [ -f "$initrd" ]; then
-            cp -f "$initrd" '${DEPLOYDIR}/${INITRD_DEPLOY_FILE}'
-        fi
-    fi
-
     for file in ${DTB_FILES}; do
         dtb="$(find '${IMAGE_ROOTFS}/usr/lib' -type f \
                     -iwholename '*linux-image-*/'${file} | head -1)"
@@ -450,7 +441,7 @@ EOSUDO
         -exec touch '{}' -h -d@${SOURCE_DATE_EPOCH} ';'
 }
 do_rootfs_finalize[network] = "${TASK_USE_SUDO}"
-addtask rootfs_finalize before do_rootfs after do_rootfs_postprocess
+addtask rootfs_finalize before do_rootfs after do_rootfs_postprocess do_generate_initramfs
 
 ROOTFS_QA_FIND_ARGS ?= ""
 
@@ -461,6 +452,8 @@ 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/initramfs.bbclass b/meta/classes/initramfs.bbclass
index 0197a60b..3a996f78 100644
--- a/meta/classes/initramfs.bbclass
+++ b/meta/classes/initramfs.bbclass
@@ -6,14 +6,11 @@ DEPLOYDIR = "${WORKDIR}/deploy"
 STAMP = "${STAMPS_DIR}/${DISTRO}-${DISTRO_ARCH}/${PN}-${MACHINE}/${PV}-${PR}"
 STAMPCLEAN = "${STAMPS_DIR}/${DISTRO}-${DISTRO_ARCH}/${PN}-${MACHINE}/*-*"
 
-# Sstate also needs to be machine-specific
-SSTATE_MANIFESTS = "${TMPDIR}/sstate-control/${MACHINE}-${DISTRO}-${DISTRO_ARCH}"
-SSTATETASKS += "do_generate_initramfs"
-
 INITRAMFS_INSTALL ?= ""
 INITRAMFS_PREINSTALL ?= ""
 INITRAMFS_ROOTFS ?= "${WORKDIR}/rootfs"
 INITRAMFS_IMAGE_NAME = "${INITRAMFS_FULLNAME}.initrd.img"
+INITRD_DEPLOY_FILE = "${INITRAMFS_IMAGE_NAME}"
 
 # Install proper kernel
 INITRAMFS_INSTALL += "${@ ("linux-image-" + d.getVar("KERNEL_NAME")) if d.getVar("KERNEL_NAME") else ""}"
@@ -28,37 +25,3 @@ ROOTFS_FEATURES = ""
 ROOTFS_PACKAGES = "initramfs-tools ${INITRAMFS_PREINSTALL} ${INITRAMFS_INSTALL}"
 
 inherit rootfs
-
-do_generate_initramfs[network] = "${TASK_USE_SUDO}"
-do_generate_initramfs[cleandirs] += "${DEPLOYDIR}"
-do_generate_initramfs[sstate-inputdirs] = "${DEPLOYDIR}"
-do_generate_initramfs[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"
-do_generate_initramfs() {
-    rootfs_do_mounts
-
-    trap 'exit 1' INT HUP QUIT TERM ALRM USR1
-    trap 'rootfs_do_umounts' EXIT
-
-    rootfs_do_qemu
-
-    sudo -E chroot "${INITRAMFS_ROOTFS}" sh -c '\
-        export kernel_version=$(basename /boot/vmlinu[xz]* | cut -d'-' -f2-); \
-        if [ -n "$kernel_version" ]; then \
-          update-initramfs -u -v -k "$kernel_version"; \
-        else \
-          update-initramfs -u -v ;  \
-        fi'
-
-    rootfs_do_umounts
-
-    if [ ! -e "${INITRAMFS_ROOTFS}/initrd.img" ]; then
-        bberror "No initramfs was found after generation!"
-    fi
-    cp ${INITRAMFS_ROOTFS}/initrd.img ${DEPLOYDIR}/${INITRAMFS_IMAGE_NAME}
-}
-addtask generate_initramfs after do_rootfs before do_build
-
-python do_generate_initramfs_setscene () {
-    sstate_setscene(d)
-}
-addtask do_generate_initramfs_setscene
diff --git a/meta/classes/rootfs.bbclass b/meta/classes/rootfs.bbclass
index 446d92d6..d49cd1ef 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"
@@ -22,6 +23,9 @@ ROOTFS_CLEAN_FILES="/etc/hostname /etc/resolv.conf"
 
 ROOTFS_PACKAGE_SUFFIX ?= "${PN}-${DISTRO}-${DISTRO_ARCH}"
 
+# path to deploy stubbed versions of initrd update scripts during do_rootfs_install
+ROOTFS_STUBS_DIR = "/usr/local/isar-sbin"
+
 # Useful environment variables:
 export E = "${@ isar_export_proxies(d)}"
 export DEBIAN_FRONTEND = "noninteractive"
@@ -165,6 +169,13 @@ 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
+    sudo mkdir -p "${ROOTFSDIR}${ROOTFS_STUBS_DIR}"
+    sudo cp -a ${ROOTFSDIR}/usr/bin/true ${ROOTFSDIR}${ROOTFS_STUBS_DIR}/update-initramfs
+}
 
 ROOTFS_INSTALL_COMMAND += "rootfs_install_pkgs_update"
 rootfs_install_pkgs_update[weight] = "5"
@@ -227,7 +238,21 @@ rootfs_install_pkgs_install[progress] = "custom:rootfs_progress.PkgsInstallProgr
 rootfs_install_pkgs_install[network] = "${TASK_USE_SUDO}"
 rootfs_install_pkgs_install() {
     sudo -E chroot "${ROOTFSDIR}" \
-        /usr/bin/apt-get ${ROOTFS_APT_ARGS} ${ROOTFS_PACKAGES}
+        /usr/bin/apt-get ${ROOTFS_APT_ARGS} \
+            -o DPkg::Path='${ROOTFS_STUBS_DIR}:/usr/sbin:/usr/bin:/sbin:/bin' \
+            ${ROOTFS_PACKAGES}
+}
+
+ROOTFS_INSTALL_COMMAND += "rootfs_restore_initrd_tooling"
+rootfs_restore_initrd_tooling[weight] = "1"
+rootfs_restore_initrd_tooling() {
+    sudo rm -rf "${ROOTFSDIR}${ROOTFS_STUBS_DIR}"
+}
+
+ROOTFS_INSTALL_COMMAND += "${@bb.utils.contains('ROOTFS_FEATURES', 'no-generate-initrd', 'rootfs_clear_initrd_symlinks', '', d)}"
+rootfs_clear_initrd_symlinks() {
+    sudo rm -f ${ROOTFSDIR}/initrd.img
+    sudo rm -f ${ROOTFSDIR}/initrd.img.old
 }
 
 do_rootfs_install[root_cleandirs] = "${ROOTFSDIR}"
@@ -421,6 +446,45 @@ python do_rootfs_postprocess() {
 }
 addtask rootfs_postprocess before do_rootfs after do_unpack
 
+SSTATETASKS += "do_generate_initramfs"
+do_generate_initramfs[network] = "${TASK_USE_SUDO}"
+do_generate_initramfs[cleandirs] += "${DEPLOYDIR}"
+do_generate_initramfs[sstate-inputdirs] = "${DEPLOYDIR}"
+do_generate_initramfs[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"
+python do_generate_initramfs() {
+    bb.build.exec_func('rootfs_do_mounts', d)
+    bb.build.exec_func('rootfs_do_qemu', d)
+    try:
+        bb.build.exec_func('rootfs_generate_initramfs', d)
+    finally:
+        bb.build.exec_func('rootfs_do_umounts', d)
+}
+
+python do_generate_initramfs_setscene () {
+    sstate_setscene(d)
+}
+
+rootfs_generate_initramfs[progress] = "custom:rootfs_progress.InitrdProgressHandler"
+rootfs_generate_initramfs() {
+    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-); \
+            echo "Generating initrd"; \
+            update-initramfs -u -v -k "$kernel_version";'
+        if [ -n "${INITRD_DEPLOY_FILE}" ]; then
+            cp ${ROOTFSDIR}/initrd.img ${DEPLOYDIR}/${INITRD_DEPLOY_FILE}
+        fi
+    else
+        echo "no kernel in this rootfs, do not generate initrd"
+    fi
+}
+
+python() {
+    if 'no-generate-initrd' not in d.getVar('ROOTFS_FEATURES', True).split():
+        bb.build.addtask('do_generate_initramfs', 'do_rootfs', 'do_rootfs_postprocess', d)
+        bb.build.addtask('do_generate_initramfs_setscene', None, None, d)
+}
+
 python do_rootfs() {
     """Virtual task"""
     pass
diff --git a/meta/recipes-devtools/sbuild-chroot/sbuild-chroot.inc b/meta/recipes-devtools/sbuild-chroot/sbuild-chroot.inc
index 6478d3a6..98e427e5 100644
--- a/meta/recipes-devtools/sbuild-chroot/sbuild-chroot.inc
+++ b/meta/recipes-devtools/sbuild-chroot/sbuild-chroot.inc
@@ -55,6 +55,7 @@ SBUILD_CHROOT_PREINSTALL_COMMON = " \
 SBUILD_CHROOT_DIR = "${WORKDIR}/rootfs"
 ROOTFSDIR = "${SBUILD_CHROOT_DIR}"
 ROOTFS_PACKAGES = "${SBUILD_CHROOT_PREINSTALL}"
+ROOTFS_FEATURES += "no-generate-initrd"
 
 ROOTFS_POSTPROCESS_COMMAND:remove = "rootfs_cleanup_isar_apt"
 
-- 
2.39.5

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