[systemd-devel] Fedora 25, cgroups V2 and systemd roadmap

Daniel P. Berrange berrange at redhat.com
Tue Oct 18 08:51:17 UTC 2016

On Tue, Oct 11, 2016 at 11:30:40PM +0300, Kevin Wilson wrote:
> Hello, Daniel,
> > We don't want to support out of tree kernel patches,
> This sounds very reasonable, I don't have anything against this policy.
> Still, I wonder: are you ruling out implementing "hybrid mode" (like
> Lennart uses in systemd) for libvirt? I mean a mode where you will use
> the 3 currently supported cgroup V2 controllers for libvirt (memory,
> io and pids; actually I don't know if you use the cgroups pids at all
> in libvirt, it is a new controller; BTW - do you ? ). And using other
> controllers (besides io, memory and pids) from cgroup V1

A controller can only be used in one mode at any time - so while libvirt
could potentially support using some in v1 mode and some in v2 mode, it
only works if the OS distro has actually setup those controllers in v1
mode - if they're in v2 mode, we'd be forced to use them in v2 mode.

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