Ship kernel modules Zstd compressed

[Benjamin Drung]

To reduce the size of the initramfs and also to speed up the boot (by only decompressing the modules that are needed), please compress the kernel modules. From size and speed perspective, either use zstd or xz. I suggest to go with zstd -19.

This change is independent of the initramfs-tools version. Old initramfs-tools versions will decompress the kernel modules before putting them in the initramfs. New initramfs-tools versions will put the compressed kernel modules into an uncompressed cpio archive (see bug #2028567).

See also https://lists.ubuntu.com/archives/ubuntu-devel/2023-July/042652.html and https://lists.ubuntu.com/archives/ubuntu-devel/2023-July/042707.html

See https://discourse.ubuntu.com/t/reduce-initramfs-size-and-speed-up-the-generation-in-ubuntu-23-10/38972 for the performance evaluation.

[Benjamin Drung (bdrung)]

Attached a tested patch for zstd -19 compression.

[Dimitri John Ledkov (xnox)]

hi, i like portions of the patch, but not quite where in the machinery it is implemented.

As we have many more packages that ship .ko modules, and those debs should not be compressed.

And also i'd want to enable in-kernel decompressor too.

[Dimitri John Ledkov (xnox)]

https://lists.ubuntu.com/archives/kernel-team/2023-July/141412.html

[Dimitri John Ledkov (xnox)]

This will be available in the next kernel builds, likely as part of landing v6.5 kernel into mantic.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-oem-6.5/6.5.0-1002.2 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-oem-6.5' to 'verification-done-jammy-linux-oem-6.5'. If the problem still exists, change the tag 'verification-needed-jammy-linux-oem-6.5' to 'verification-failed-jammy-linux-oem-6.5'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 6.5.0-5.5

---------------
linux (6.5.0-5.5) mantic; urgency=medium

  * mantic/linux: 6.5.0-5.5 -proposed tracker (LP: #2034546)

  * Packaging resync (LP: #1786013)
    - [Packaging] update helper scripts
    - debian/dkms-versions -- update from kernel-versions (main/d2023.08.23)

 -- Andrea Righi <email address hidden> Wed, 06 Sep 2023 15:51:04 +0200

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-azure-6.5/6.5.0-1007.7~22.04.1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-azure-6.5' to 'verification-done-jammy-linux-azure-6.5'. If the problem still exists, change the tag 'verification-needed-jammy-linux-azure-6.5' to 'verification-failed-jammy-linux-azure-6.5'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-aws-6.5/6.5.0-1008.8~22.04.1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-aws-6.5' to 'verification-done-jammy-linux-aws-6.5'. If the problem still exists, change the tag 'verification-needed-jammy-linux-aws-6.5' to 'verification-failed-jammy-linux-aws-6.5'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Werner Sembach (matombo)]

I spoted that for jammy hwe 6.5.0-14.14 the modules are still not compressed, albeit CONFIG_MODULE_COMPRESS_ZSTD is 'y' for amd64 in config/annotations.
I also spotted that when the modules are compressed, DKMS compresses built modules too, but DKMS v2.8.7 (the version running in jammy) has a bug that compressed modules don't get MOK signed.

[Werner Sembach (matombo)]

Nevermind, found the relevant commit/revert https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/jammy/commit/?h=Ubuntu-hwe-6.5-6.5.0-14.14_22.04.1&id=21f3ac7412644fb59a13db2e3adbb8a38cba9923