From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: legacy mode Date: Thu, 27 Aug 2015 15:21:37 -0500 Message-ID: <20150827202137.GA4221@mail.hallyn.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Hi, after the unified cgroup overview at the containers mini-summit last week, I mentioned the idea of supporting backward-compatible cgroupfs mounts in the unified hierarchy. The problem this would solve is running older userspace (i.e. libvirt in a container running an older distro) on a newer kernel which has unified hierarchy mounted. I was thinking this could do the same tricks I'm doing in cgmanager to support the existing cgmanager API with the unified hierarchy: i.e. create a leaf node for every cgroup, and redirect any tasks written to the cgroup.procs file for $cgroup to $cgroup/.leaf. I realize there will likely be other changes, but keeping in mind that new unified-only features aren't relevant for legacy support, maybe this sort of approach wouldn't be as bad as I originally thought it would be. Not supporting release-agent is also a non-issue imo. The combination of cgroup namespaces, a "legacy-mount" mode, and fully proper hierarchical support leading to full safe delegation, would allow cgmanager and lxcfs to be killed with extreme privilege - WIN! So is anyone interested on working on a legacy mount option? What other issues need to be considered there? thanks, -serge