mate-desktop missing cgroups support, dangerous if systemd-oomd is used

[adatum]

Expected behaviour

The whole X-session should not be killed when systemd-oomd kills processes when running low on memory.

Actual behaviour

From RH2078108: "Using systemd-oomd is dangerous for mate-desktop because it can kill the whole X-session because of missing cgroups support.
When system runs out of memory X-session will be kiiled by systemd-oomd, reported by a users in reports."

Workaround:
From RH2078108: "Mate desktop [in Fedora] will step back to original earlyoom memory management implementation, which was used before f34 in fedora.

So removing systemd-oomd-defaults will simply disable systemd-oomd unit, and earlyoom service will be installed by the update and is enabled by default."

Steps to reproduce the behaviour

Trigger systemd-oomd out of memory killer while using a desktop environment or window manager without cgroups support

MATE general version

1.26

Package version

mate-desktop-1.26.0-2.fc35

Linux Distribution

Fedora 35

Link to bugreport of your Distribution (requirement)

https://bugzilla.redhat.com/show_bug.cgi?id=2078108

Additional references:
https://bugzilla.redhat.com/show_bug.cgi?id=2068699

https://fedoraproject.org/wiki/Changes/EnableSystemdOomd#Should_spins_that_don.27t_put_processes_in_separate_cgroups_be_excluded_from_this_change.3F

https://bugzilla.redhat.com/show_bug.cgi?id=1933494

[raveit65]

I can confirm that missing cgroups support is an issue in fedora.
Since f34 systemd-oomd is the default out-of-memory-killer. Without cgroup support systemd-oomd can kill the whole X session on systems with low memory.
It was hard action for me to switch back actual 3 fedora releases to earlyoom out-of-memory-killer.
And i want clearly state that this is a workaround and not a real solution.
Real solution is to support cgroups.
Well, it's only a question of time when systemd-oomd will arrive in ubuntu, debian or other distros.
Docs: https://fedoraproject.org/wiki/Changes/EnableSystemdOomd
User pain: https://bugzilla.redhat.com/show_bug.cgi?id=2068699

[lukefromdc]

As of now, wiithout something like systemd-oomd, instead of automatically losing even my entire X session, if I use up the RAM on something like my laptop, I have to act very fast to kill a big process or even the X session itself, or I risk having to power cycle the entire machine to get out of an unresponsive condition. Even auto-killing the X session beats a freeze and having to power cycle. I don't know much about cgroups, but being able to kill just the offending (possibly memorly leaking) process can be a big deal on laptops that never seem to have enough RAM

[lillolollo]

Actually systemd-oomd is already in ubuntu 22.04 with problems.. systemd/systemd#19007

[jhgit]

Has there been any progress regarding enabling cgroup support for MATE? Patches / pull requests to try?

[lukefromdc]

I don't know enough about cgroups to even start with that right now. Maybe some of the others here do?