Re: [PR PATCH] [Merged]: drop slub_debug/page_poison from bootloaders

[q66 <q66@users.noreply.github.com>]

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There's a merged pull request on the void-packages repository

drop slub_debug/page_poison from bootloaders
https://github.com/void-linux/void-packages/pull/29142

Description:
These are kernel hardening options introduced into Void in 2016. On most modern hardware they have a small performance hit, on older hardware they can have a significant performance hit. In kernel 5.3, new options were introduced, `init_on_alloc` and `init_on_free`. There are also kernel options to make these default.

The new defaults have been toggled in kernels 5.4, 5.10 and 5.11 in bd0d33eec0bd774d8cc62e32689b6fbfda517179. I explicitly did not enable `init_on_free` since that has a much bigger performance penalty, even on current-day hardware.

The only "drawback" of these changes is that people using old kernels will not get these options anymore. OTOH, the new behavior is much better in other ways (it has less of an impact, it's enabled in kernels rather than default configs so any changes to it will propagate to all users unconditionally, etc). And also, there isn't any other mainstream distribution that was using these options in the first place, for a reason, as far as I can tell.

People on kernels 4.4, 4.9, 4.14 and 4.19 who really care can update it themselves. But since older kernels tend to be associated with older hardware, they'll probably want to keep the options off in the first place.

What troubles me more is that even if I merge this PR, it will not propagate to existing users who have modified their `/etc/default/grub`, so they will need to change those files themselves. The new default kernel options are not incompatible with the old options, but people will likely want to remove them anyway. So we should probably put information about this in the documentation, too.

[ci skip]

Anyway, waiting with merging this until the affected kernels have been rebuilt (i.e. for their next version bump).