On Mon, 31 Jul 2023 at 20:41, Benjamin Drung <bdr...@ubuntu.com> wrote: > > On Thu, 2023-07-27 at 11:51 +1200, Michael Hudson-Doyle wrote: > > > > > > On Thu, 27 Jul 2023 at 09:21, Benjamin Drung <bdr...@ubuntu.com> > > wrote: > > > On Wed, 2023-07-26 at 17:53 +0200, Benjamin Drung wrote: > > > > Hi all, > > > > > > > > A few weeks ago, I posted an idea how to reduce the initramfs size > > > > and > > > > speed up the generation: > > > > > > > > https://lists.ubuntu.com/archives/ubuntu-devel/2023-July/042652.html > > > > > > > > This post sparked a lively discussion. The initial idea was > > > > ditched for > > > > a better solution: mkinitramfs will put all compressed files > > > > (kernel > > > > modules and firmware files) into a cpio archive that is not > > > > compressed > > > > (because compressing compressed files makes no sense). All other > > > > files > > > > will be added to a cpio archive that gets compressed. As next > > > > steps, the > > > > kernel modules and firmware files need to be shipped compressed. > > > > > > > > After several iterations for the implementation and review by > > > > Daves > > > > Jones, I just uploaded initramfs-tools 0.142ubuntu8 to mantic that > > > > puts > > > > compressed kernel modules and firmware files in an uncompressed > > > > cpio > > > > (https://launchpad.net/bugs/2028567). > > > > > > > > I created/updated the follow-up tickets and added my patches to > > > > them: > > > > > > > > Ship kernel modules Zstd compressed > > > > https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2028568 > > > > > > > > compress firmware in /lib/firmware > > > > https://bugs.launchpad.net/ubuntu/+source/linux-firmware/+bug/1942260 > > > > > > > > And without further ado, here come the benchmark results: > > > > > > > > The benchmarks were done either on an AMD Ryzen 7 5700G with > > > > schroot and > > > > overlay on tmpfs or on the hardware mentioned. All tests were > > > > running > > > > the latest Ubuntu mantic development release. > > > > > > > > * minimal: schroot with linux-image-generic initramfs-tools zstd > > > > * full: minimal + busybox-initramfs cryptsetup-initramfs > > > > isc-dhcp-client kbd lvm2 mdadm ntfs-3g plymouth plymouth-theme- > > > > spinner > > > > * nvidia: full + linux-headers-generic nvidia-driver-525 > > > > * nvidia fw: nvidia + compressed /lib/firmware/nvidia/525.125.06/ > > > > * VisionFive 2: VisionFive 2 RISC-V board > > > > * RPi Zero 2: Raspberry Pi Zero 2 ARM board (running armhf) > > > > > > > > "next" means using kernel/firmware/initramfs from ppa:bdrung/ppa > > > > i.e. > > > > * initramfs-tools 0.142ubuntu7bd4 > > > > * linux 6.3.0-7.7bd2 > > > > * linux-firmware 20230629.gitee91452d-0ubuntu1bd1 > > > > > > > > > | | build | size | uncompressed > > > > > size | > > > > > | test | time | in bytes | in MiB | in bytes | in > > > > > MiB | > > > > > |----------------|---------|-----------|--------|--------------- > > > > > -----| > > > > > | minimal | 4.30 s | 66701818 | 63.6 | 224087608 | > > > > > 213.7 | > > > > > | minimal next | 4.54 s | 59935186 | 57.2 | 67738810 | > > > > > 64.6 | > > > > > | full | 7.15 s | 118007038 | 112.5 | 387976843 | > > > > > 370.0 | > > > > > | full next | 7.29 s | 106937908 | 102.0 | 128610985 | > > > > > 122.7 | > > > > > | nvidia | 7.04 s | 209200523 | 199.5 | 513554279 | > > > > > 489.8 | > > > > > | nvidia next | 7.21 s | 195246287 | 186.2 | 235288174 | > > > > > 224.4 | > > > > > | nvidia fw next | 7.16 s | 191329102 | 182.5 | 213078234 | > > > > > 203.2 | > > > > > | VisionFive 2 | 142.9 s | 121895035 | 116.2 | 411160836 | > > > > > 392.1 | > > > > > | VF 2 next | 126.7 s | 111651453 | 106.5 | 134120804 | > > > > > 127.9 | > > > > > | RPi Zero 2 | 109.5 s | 39803044 | 40.0 | 69592789 | > > > > > 66.4 | > > > > > | RPi Zero 2 ² | 103.5 s | 39804499 | 40.0 | 69592789 | > > > > > 66.4 | > > > > > | RPi Zero 2 next| 101.2 s | 31463352 | 30.0 | 41145762 | > > > > > 39.2 | > > > > > > > > ² Updated initramfs-tools (but no compressed modules or firmware) > > > > > > > > The build time was averaged over five runs. > > > > > > > > > | improvement | build time | size | uncompressed size | > > > > > |--------------|------------|--------|-------------------| > > > > > | minimal | 105.6 % | 89.9 % | 30.2 % | > > > > > | full | 102.0 % | 90.6 % | 33.1 % | > > > > > | nvidia | 101.7 % | 91.5 % | 41.5 % | > > > > > | VisionFive 2 | 88.7 % | 91.6 % | 32.6 % | > > > > > | RPi Zero 2 | 92.4 % | 79.0 % | 59.1 % | > > > > > > > > Building the initramfs takes more CPU cycles (see tests on tmpfs), > > > > but > > > > saves time on disk IO. Daves Jones saw much bigger time savings on > > > > his > > > > Raspberry Pis but his tests were on lunar. > > > > > > > > Build time influence: > > > > + add_directories plus uniq take several milliseconds > > > > + depmod on compressed kernel modules take hundreds of > > > > milliseconds longer > > > > - copying smaller kernel modules (due to compression) is faster > > > > - cpio archive that needs to be compressed is smaller > > > > - not storing intermediate cpio archives saves time > > > > > > > > Saving 10 to 20 percent on the initramfs size and only needing > > > > half or a > > > > third of the size when unpacked (i.e. needed memory during boot) > > > > is a > > > > good improvement. > > > > > > The smaller initramfs overall size (less to load into memory and > > > unpack) > > > and the smaller compressed cpio (less to decompress) have a positive > > > effect on the boot speed, especially on systems with slow CPU and/or > > > slow IO. > > > > > > When looking at the "kernel" time from systemd-analyze, the > > > improvement > > > ranges from 1.62s - 1.36s = 0.26s in a VM on my desktop to a heavily > > > noticeable 37.9s - 16.5s = 21.4s on the VisionFive 2 RISC-V board. > > > > > > > > > This is good stuff. It's a bit of a shame that the build time for the > > initramfs hasn't improved much. I guess it's not as dominated by > > compression time as I thought? > > > > Do you have any thoughts about making it faster? I know I once ran > > 'strace -ff mkinitramfs' and ended up with tens or hundreds of > > thousands of trace files so not having everything done by a billion > > tiny shell scripts would help, but I don't know how much. > > Good questions. I sprinkled mkinitramfs with "date -Ins" to see where > most time is spent. I ran the "full next" test case in a chroot on my > laptop. mkinitramfs took 19.71 seconds. The most time consuming parts: > > * 10.13 s (51.4%) auto_add_modules > * 7.20 s (36.5%) run_scripts_optional /usr/share/initramfs-tools/hooks > * 1.27 s (6.4%) final { cat; cpio; cpio|compress } > $outfile > > The remaining 1.11 seconds are spread over the remaining parts. > > Following hooks in /usr/share/initramfs-tools/hooks took the longest: > > * 4.56s (63.3%) framebuffer > * 0.87s (12.1%) plymouth > * 0.81s (11.3%) cryptroot > * 0.23s (3.2%) lvm2 > * 0.18s (2.5%) udev > * 0.17s (2.4%) mdadm > > The remaining 0.38 seconds are spread over the remaining dozen of hooks. > > So we should focus on auto_add_modules and the slowest scripts in > /usr/share/initramfs-tools/hooks to improve the execution time. > > The framebuffer hook just calls copy_modules_dir and manual_add_modules > multiple times. auto_add_modules calls copy_modules_dir multiple times > and manual_add_modules. copy_modules_dir calls find and then > manual_add_modules. > > So most time will be spent in manual_add_modules. This function calls > modprobe on the modules, copies the modules, and add_firmware on the > firmwares from a "modinfo -F firmware" call. > > Any ideas to cut that time down? Using a cache for the modprobe/modinfo > calls?
In core-initrd, the above shell script functions are not used, instead /usr/lib/dracut/dracut-install is used which can resolve individual modules, subtrees, and wildcards with firmware pretty quickly. Was not benchmarked. I wonder if you can experiment to assemble a long list of requested modules / patterns / module dirs, and do a single call to dracut-install to do them all in one go, and see if that helps things? -- okurrr, Dimitri -- ubuntu-devel mailing list ubuntu-devel@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel
