[slurm-users] cgroup2

[Richard Neuböck]

Hi,

I have a (hopefully quick) question: Do the slurm 19.05 cgroup plugins
know how to handle cgroup v2?

I'm setting up slurm on Fedora 32 and get the following error messages:

May 29 11:34:17 regulus slurmd[171632]: error: unable to mount cpuset
cgroup namespace: Device or resource busy
May 29 11:34:17 regulus slurmd[171632]: error: task/cgroup: unable to
create cpuset namespace
May 29 11:34:17 regulus slurmd[171632]: error: Couldn't load specified
plugin name for task/cgroup: Plugin init() callback failed
May 29 11:34:17 regulus slurmd[171632]: error: cannot create task
context for task/cgroup
May 29 11:34:17 regulus slurmd[171632]: error: slurmd initialization failed

Google didn't reveal anything useful for me so my searching tangents and
parts of the slurm source just gave me some directions. I'm guessing
slurm only knows cgroup v1 so it fails when it tries to interact with
cgorup v2. Am I correct or am I barking up the wrong tree?

Thanks for you feedback in advance!
Cheers
Richard

[Richard Neuböck]

To answer my own question just in case I'm not the only one stumbling on
this.

slurm 19.05 (packaged with Fedora 32) can't handle cgroup v2.

If there is nothing depending on cgroup v2 you can switch to the legacy
hierarchy by adding a kernel boot command line:

systemd.unified_cgroup_hierarchy=0

[Christoph Brüning]

Hi everyone,

sorry to bring this old thread back up, but I'm seeing the same on
Debian Bullseye with Slurm 20.11.3 from Debian's Repository.

Also thanks, Richard, for posting your solution. You're actually "not
the only one stumbling on this." :)

I haven't found anything on that topic in the Release Notes of Slurm
20.02 and 20.11, so I guess nothing of importance has changed from 19.05.

Now, what is the best practice in this case?
Switch back to hybrid cgroups hierarchy and wait for a future Slurm
version that can handle unified?
Does anyone know if that version is being worked upon and maybe when we
can expect it?

Cheers,
Christoph

--
Dr. Christoph Brüning
Universität Würzburg
HPC & DataManagement @ ct.qmat & RZUW
Am Hubland
D-97074 Würzburg
Tel.: +49 931 31-80499