cinder doesnt work with cgroups v2

Bug #1942203 reported by Thomas Goirand
This bug affects 1 person
Affects Status Importance Assigned to Milestone

Bug Description


cgroups v2 has landed in Debian Unstable. Therefore, Cinder QoS with cgroups is now broken. Here's the matching Debian bug:

This likely will propagate to Ubuntu very quickly...

I'm hereby cut/pasting part of the Debian bug:

It means that instead of using blkio, as in cinder has to use the io controller (If I am not wrong). You can refer to the kernel documentation about cgroups v2:

Cinder would have to call `cgset` and `cgcreate` with paths according to the cgroup version supported by the running system. To know if cgroup v2 is supported, one way is to `grep cgroup2 /proc/mounts`

I'm not really sure of what's just above though. If this checks if the kernel supports it, it doesn't tell what flavor of the cgroup userland is supported. Therefore, to play it self, I would suggest using a configuration value so that Cinder can:
- autodetect (attempt with how it's described above)
- force old style cgroup v1
- force new style cgroup v2


Thomas Goirand (zigo)

Tags: cgroups
Changed in cinder:
status: New → Triaged
importance: Undecided → High
assignee: nobody → Brian Rosmaita (brian-rosmaita)
milestone: none → xena-rc1
Revision history for this message
Brian Rosmaita (brian-rosmaita) wrote :

We're going on the assumption that everyone supports cgroup v2, and the issue is that they're dropping support for cgroup v1. So we should just switch to cgroup v2.

The other issue is that the library cinder uses to handle cgroup (v1), libcgroup, has been extended to handle cgroup v2, but it is not packaged for the Red Hat family of distros (and apparently there are no plans to do so).

The recommendation seems to be to use systemd to handle cgroup creation. For example, see

Eric Harney suggests something like this: define systemd .slice files, and launch the command with "systemd-run --slice=cinder-whatever.slice <command>" instead of cgexec (cgexec is supplied by libcgroup).

Changed in cinder:
milestone: xena-rc1 → yoga-rc1
assignee: Brian Rosmaita (brian-rosmaita) → nobody
tags: added: cgroups
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