c3bb9d18dc
On systems with a large number of devices, usually multipath devices,
dracut can spend a lot of time stat'ing the devices to collect the
major/minor numbers, leading to huge slowness rebuilding the initramfs
when stat'ing devices is slow (seen with oracleasm file systems in
particular).
This commit implements a basic cache stored in a file under
DRACUT_TMPDIR storing the major:minor corresponding to the specified
device.
Reproducer: create N loopback devices used as a LVM extension to volume
group hosting the root file system
# LVMVG="rhel"
# NDEVICES=200
# mkdir devices; for i in $(seq 1 $NDEVICES); do
truncate -s 10m devices/$i; losetup loop$i devices/$i
done
# vgextend $LVMVG $(/bin/ls -1 /dev/loop[0-9]*)
With standard code (tested with RHEL8.3 dracut):
# dracut -f --debug /tmp/initramfs.img $(uname -r) >/tmp/debug 2>&1
# grep -c "stat -L -c" /tmp/debug
2440
With this code:
# dracut -f --debug /tmp/initramfs.img $(uname -r) >/tmp/debug_optim 2>&1
# grep -c "stat -L -c" /tmp/debug_optim
205
Signed-off-by: Renaud Métrich <rmetrich@redhat.com>
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| .github | ||
| docs | ||
| dracut.conf.d | ||
| install | ||
| install.d | ||
| man | ||
| modules.d | ||
| pkgbuild | ||
| shell-completion/bash | ||
| src | ||
| test | ||
| tools | ||
| .astylerc | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .gitignore | ||
| .kateconfig | ||
| .kateproject | ||
| .mailmap | ||
| .packit.yml | ||
| .shellcheckrc | ||
| .vimrc | ||
| AUTHORS | ||
| COPYING | ||
| Makefile | ||
| NEWS.md | ||
| README.md | ||
| configure | ||
| dracut-catimages.sh | ||
| dracut-functions.sh | ||
| dracut-init.sh | ||
| dracut-initramfs-restore.sh | ||
| dracut-logger.sh | ||
| dracut.conf | ||
| dracut.css | ||
| dracut.png | ||
| dracut.sh | ||
| dracut.svg | ||
| lsinitrd.sh | ||
README.md
dracut
dracut is an event driven initramfs infrastructure.
dracut (the tool) is used to create an initramfs image by copying tools and files from an installed system and combining it with the dracut framework, usually found in /usr/lib/dracut/modules.d.
Unlike other implementations, dracut hard-codes as little as possible into the initramfs. The initramfs has (basically) one purpose in life -- getting the rootfs mounted so that we can transition to the real rootfs. This is all driven off of device availability. Therefore, instead of scripts hard-coded to do various things, we depend on udev to create device nodes for us and then when we have the rootfs's device node, we mount and carry on. This helps to keep the time required in the initramfs as little as possible so that things like a 5 second boot aren't made impossible as a result of the very existence of an initramfs.
Most of the initramfs generation functionality in dracut is provided by a bunch of generator modules that are sourced by the main dracut script to install specific functionality into the initramfs. They live in the modules.d subdirectory, and use functionality provided by dracut-functions to do their work.
Currently dracut lives on github.com and kernel.org.
The tarballs can be found here: http://www.kernel.org/pub/linux/utils/boot/dracut/ ftp://ftp.kernel.org/pub/linux/utils/boot/dracut/
Git: https://github.com/dracutdevs/dracut.git http://git.kernel.org/?p=boot/dracut/dracut.git
Project Documentation: http://www.kernel.org/pub/linux/utils/boot/dracut/dracut.html
Project Wiki: http://dracut.wiki.kernel.org
See the github issue tracker for things which still need to be done and HACKING.md for some instructions on how to get started. There is also a mailing list that is being used for the discussion -- initramfs@vger.kernel.org. It is a typical vger list, send mail to majordomo@vger.kernel.org with body of 'subscribe initramfs email@host.com'
Licensed under the GPLv2