On Sat, Jul 08, 2023, Benjamin Drung wrote: > On Sat, 2023-07-08 at 03:49 +0200, Benjamin Drung wrote: > > On Sat, 2023-07-08 at 01:25 +0100, Dimitri John Ledkov wrote: > > > On Sat, 8 Jul 2023 at 01:19, Benjamin Drung <bdr...@ubuntu.com> wrote: > > > > > > > > Hi all, > > > > > > > > a year ago we changed the default compression and level for the > > > > initramfs to zstd -1. This fixed the very slow creation times on > > > > development boards (see bug #1958148), but that leads to bigger > > > > initramfs sizes that triggered other bugs (like bug #1842320). > > > > Big initramfs sizes can also fill up small sized /boot partitions easily > > > > (grooming the 850 initramfs-tools bugs revealed several such reports). > > > > > > > > Using xz -9 would give very good compression, but it takes very long > > > > (especially on slow development boards) and a lot of memory (good luck > > > > on Raspberry Pis with small memory like Pi Zeros). > > > > > > > > I propose following approach to address the drawback: Create cpio > > > > archives (compressed with xz -9) for the kernel modules and firmware > > > > files when building the kernel/firmware Debian package. Then ship those > > > > cpio archives in the package (or in a separate binary package). Then the > > > > CPU load it put on the builders. The cpio archives would contain the > > > > modules for MODULES=most. > > > > > > > > mkinitramfs will then look for those cpio archives and uses those in > > > > case they are present. Such a initramfs would look like this: > > > > > > > > * AMD/Intel microcode cpio archive (on amd64) > > > > * main cpio archive compressed with zstd -1 > > > > * kernel modules from the Debian package compressed with xz -9 > > > > * firmware files from the Debian package compressed with xz -9 > > > > > > > > > > Majority of our instances boot without initrd, and there too they > > > don't load most of the modules. > > > Creating xz -9 compressed archive of all modules, still pays the > > > penalty to decompress most of them, and then not modprobe them. > > > I was hoping to achieve a similar in spirit approach, but didn't quite > > > have the time to implement is: > > > > > > 1) change linux-modules and linux-firmware to ship .ko.zst > > > firmware.bin.zst compressed with zstd -19 at .deb build time > > > 2) this saves install size of the packages, with only slightly > > > increased download size > > > 3) modify initramfs-tools to include compressed files into a separate > > > initrd, which is not compressed (i.e. exclude .zst files from the > > > default main compressed cpio archive, and append them in the second > > > main cpio archive that is uncompressed) > > > 4) this should achieve quick initrd creation, which will be smaller in > > > size that current status, and will boot faster as it will only > > > decompress modules/firmware it actually needs at boot > > > > > > For experimentation locally, you can recompress .ko with zstd in place > > > in /lib/modules/; and rerun depmod. To then test initramfs-tools > > > changes that skip over .zst compressed files and add them as is in an > > > uncompressed appended cpio. > > > > That is a very good idea. I created a draft for point 3 in [2]. It moves > > the compressed files into a separate directory and creates a separate > > cpio archive for that directory without compressing it: > > > > * AMD/Intel microcode cpio archive (on amd64) > > * main cpio archive (compressed) > > * compressed kernel modules / firmware (not compressed) > > > > Sadly this does not work (yet). cpio complains with "premature end of > > archive" when looking at it and the kernel fails to extract the last > > cpio part. I am heading to bed now leaving that bug for another day. > > > > [2] > > https://code.launchpad.net/~bdrung/ubuntu/+source/initramfs-tools/+git/initramfs-tools/+ref/ubuntu/compressed > > Okay. It works now. The not-compressed cpio archive must not be the last > one. So the order is now: > > * AMD/Intel microcode cpio archive (on amd64) > * compressed kernel modules / firmware (not compressed) > * main cpio archive (compressed) > > I'll really stop now. For a first comparison, the firmware files need to > be converted correctly. There are symlinks in /lib/firmware. So running > following was not correct/enough: > > find /lib/firmware -name '*.bin' | while read -r fw; do > sudo zstd -19 -z -o "${fw}.zst" "$fw" > sudo rm "$fw" > done > > If you want to help, hand me a correct conversion script.
Some filenames in /lib/firmware contain spaces. There are many more files than .bin ones. A number of the files are readmes. Recent changes in linux-firmware.git add "install-xz" and "install-zstd" targets to make than will do what you want I guess. I haven't checked that this was actually merged; it was discussed at least on 2023-03-01 on the mailing-list. It's probably the best path forward in any case. In case it isn't merged, you can have a look at https://lore.kernel.org/linux-firmware/20230301-fixes-and-compression-v2-0-e2b71974e...@gmail.com/T/ -- Adrien -- ubuntu-devel mailing list ubuntu-devel@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel
