Bookworm: Poor systemd performance on arm cpu

[Kirill Buksha]

Hello,

I'm part of a team that develops embedded linux systems that use systemd package and mostly based on ARM processors.

Recently we upgraded one of our project to Debian Bookworm (systemd v252) and immediately noticed performance losses in systemd area. This is a known problem that has already been fixed in v255 of systemd:
- link to the issue: https://github.com/systemd/systemd/issues/26950
- the exact commit that fixes the problem: https://github.com/systemd/systemd/commit/f96a32c7f06995bd17daa311f491682f524e48a6

Unfortunately we are stick to Bookworm distribution and cannot update to Trixie/Sid due to other packages dependencies. Right now we are using patched systemd version, but we would like to switch back to main distribution to continue receiving updates and security patches, and I have two questions:
- would it be possible to include the specified commit as a patch in the systemd Bookworm distribution? How can I help you with this process?
- do you expect systemd v255 to be backported to bookworm? This would be really great, since v255 already contains mentioned fix and many others.

The main reason I ask is because this patch significantly improves the performance of these commands:
- `systemctl daemon-reload`: ~13 seconds with 252.33-1~deb12u1 and ~6 seconds when mentioned fix is applied;
- `systemctl enable/disable <service>`:  ~50 seconds with 252.33-1~deb12u1 and ~20 seconds when mentioned fix is applied;

I can't speak for others, but I think this kind of performance improvement will benefit all Bookworm's systemd users with more or less slow ARM processors.
Sorry if some of my questions seem stupid, I'm not familiar with the systemd distribution system and the current policy regarding patches in the stable branch.

Best regards,
Kirill