Re: new cg-manager gui tool for managin cgroups

From: Vivek Goyal <vgoyal@redhat.com>
To: Lennart Poettering <mzerqung@0pointer.de>
Cc: fedora-devel-list@redhat.com, mclasen@redhat.co,
	cg-manager-developers@lists.fedorahosted.org,
	Linda Wang <lwang@redhat.com>,
	duffy@redhat.com, containers@lists.osdl.org
Subject: Re: new cg-manager gui tool for managin cgroups
Date: Thu, 21 Jul 2011 16:58:50 -0400	[thread overview]
Message-ID: <20110721205850.GH12373@redhat.com> (raw)
In-Reply-To: <20110721161703.GD19140@tango.0pointer.de>

On Thu, Jul 21, 2011 at 06:17:03PM +0200, Lennart Poettering wrote:
> On Thu, 21.07.11 15:52, Daniel P. Berrange (berrange@redhat.com) wrote:
> 
> > > I think its a question of do we want to make users go to a bunch of
> > > different front end tools, which don't communicate with each other to
> > > configure the system? I think it makes sense to have libvirt or
> > > virt-manager and systemd front-end be able to configure cgroups, but I
> > > think it would be also nice if they could know when the step on each
> > > other. I think it would also be nice if there was a way to help better
> > > understand how the various system components are making use of cgroups
> > > and interacting. I liked to see an integrated desktop approach - not one
> > > where separate components aren't communicating with each other. 
> > 
> > It is already possible for different applications to use cgroups
> > without stepping on each other, and without requiring every app
> > to communicate with each other.
> > 
> > As an example, when it starts libvirt will look at what cgroup
> > it has been placed in, and create the VM cgroups below this point.
> > So systemd can put libvirtd in an arbitrary location and set an
> > overall limits for the virtualization service, and it will cap
> > all VMs. No direct communication between systemd & libvirt is
> > required.
> 
> systemd (when run as the user) does exactly the same thing btw. It will
> discover the group it is urnning in, and will create all its groups
> beneath that.
> 
> In fact, right now the cgroup hierarchy is not virtualized. To make sure
> systemd works fine in a container we employ the very same logic here: if
> the container manager started systemd in specific cgroup, then system
> will do all its stuff below that, even if it is PID 1.

How does the cgroup hierarchy look like in case of containers? I thought
libvirtd will do all container management and libvirtd is one of the services
started by systemd.

Thanks
Vivek
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