Needed a bit of tweaking to get this benchmarked. Had to enable zstd in kmod package and also apply a hack to the kernel package building. (See attachment).
So, the installed compressed kernel modules are 27.1 MB compared to the uncompressed 99.1 MB. The compressed extra modules are 103 MB compared to the uncompressed modules at 296 MB. linux-modules-5.13.0-8-generic installed size: zstd compressed modules: 27.1 MB normal uncompressed: 99.1 MB linux-modules-extra-5.11.0-18-generic installed size: zstd compressed modules: 103.0 MB normal uncompressed: 206.0 MB The downside is that compression for the deb and the initramfs does not do so well. It seems that compressing a lot of uncompressed modules is better than compressing already compressed modules: linux-modules-5.13.0-8-generic deb size: zstd compressed modules: 19.9 MB normal uncompressed: 17.5 MB linux-modules-extra-5.11.0-18-generic deb size: zsd compressed modules: 95.08 MB normal uncompressed: 48.70 MB (I double checked the contents of the deb) The initramfs size: zsd compressed modules: 49.77 MB normal uncompressed: 41.24 MB For boot times, the kernel + zstd modules for ZSD and uncompressed kernel modules is almost the same, zstd is fractionally faster but this is within the margins of measured error. *HOWEVER*, the zstd initramfs does not compress already compressed zstd kernel modules well, so the initramfs size is actually larger, so this impacts on the time to load the initramfs, so we end up with slower boots with zstd module compression. Attached is the data in a libre office spread sheet ** Attachment added: "raw test data" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1932329/+attachment/5506240/+files/zstd-module-compression.ods -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1932329 Title: Benchmark if we can compress kernel modules Status in linux package in Ubuntu: In Progress Bug description: Symbol: MODULE_COMPRESS_ZSTD [=n] Type : bool = Impacts to measure and observe = == Disk space == * Inspect linux-modules-* and linux-modules-extra* deb package Installed-Size and Download-Size changes, i.e. $ apt show linux-modules-5.8.0-53-generic linux-modules- extra-5.8.0-53-generic | grep -e Package: -e Size: Package: linux-modules-5.8.0-53-generic Installed-Size: 81.5 MB Download-Size: 15.5 MB Package: linux-modules-extra-5.8.0-53-generic Installed-Size: 215 MB Download-Size: 41.5 MB In theory, there should not be a significant change in the Download- size. It is desired that there is a significant reduction in Installed-Size. Modules take up about 300MB and normally one has upto three kernel version installed, resulting in about of 1GB of disk space that one constantly pays for. == Boot Speed == In theory, boot speed may either improve or regress. It depends if disk IO is slower than decompression speed, meaning loading compressed modules is faster. Also one has to observe the changes in the initrd size. zstd(zstd) compression may result in slight growth, which shouldn't impact boot speed too much. = Outcomes = If installed size savings can be achieved without regressing bootspeed we should enable CONFIG_MODULE_COMPRESS_ZSTD=y by default. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1932329/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
