[systemd-devel] version bump of minimal kernel version supported by systemd?

[Luca Boccassi]

On Thu, 2022-03-24 at 14:05 +0100, Zbigniew Jędrzejewski-Szmek wrote:
> On Thu, Mar 24, 2022 at 10:28:39AM +0000, Luca Boccassi wrote:
> > On Thu, 2022-03-24 at 09:38 +0100, Lennart Poettering wrote:
> > > On Mi, 23.03.22 11:28, Luca Boccassi (bluca at debian.org) wrote:
> > > 
> > > > At least according to our documentation it wouldn't save us much
> > > > anyway, as the biggest leap is taking cgroupv2 for granted, which
> > > > requires 4.1, so it's included regardless. Unless there's something
> > > > undocumented that would make a big difference, in practical terms of
> > > > maintainability?
> > > 
> > > Note that "cgroupv2 exists" and "cgroupv2 works well" are two distinct
> > > things. Initially too few controllers supported cgroupv2 for cgroupv2
> > > to be actually useful.
> > > 
> > > What I am trying to say is that it would actually help us a lot if
> > > we'd not just be able to take croupv2 for granted but to take a
> > > reasonably complete cgroupv2 for granted.
> > 
> > Yes, that does sound like worth exploring - our README doesn't document
> > it though, do we have a list of required controllers and when they were
> > introduced?
> 
> In the README:
>   Linux kernel >= 4.2 for unified cgroup hierarchy support
>   Linux kernel >= 4.10 for cgroup-bpf egress and ingress hooks
>   Linux kernel >= 4.15 for cgroup-bpf device hook
>   Linux kernel >= 4.17 for cgroup-bpf socket address hooks
> 
> In this light, 4.19 is better than 4.4 or 4.9 ;)
> 
> Zbyszek

I saw that, but I'm pretty sure we need to keep all the bpf-related
stuff optional regardless of that, forever. There's plenty of use cases
that disable it entirely (in the sense, things shouldn't fall apart if
we run on a non-bpf kernel and there are no bpf options configured in
any unit). I have one of them.

I think Lennart was referring to more 'core' controllers - maybe the
cpuset is one that was added pretty late? But just going from memory
here - it would be good to have a precise list.

-- 
Kind regards,
Luca Boccassi
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