On Thu, Jun 27, 2013 at 6:22 AM, Serge Hallyn <serge.hallyn@xxxxxxxxxx> wrote: > Quoting Mike Galbraith (bitbucket@xxxxxxxxx): >> On Wed, 2013-06-26 at 14:20 -0700, Tejun Heo wrote: >> > Hello, Tim. >> > >> > On Mon, Jun 24, 2013 at 09:07:47PM -0700, Tim Hockin wrote: >> > > I really want to understand why this is SO IMPORTANT that you have to >> > > break userspace compatibility? I mean, isn't Linux supposed to be the >> > > OS with the stable kernel interface? I've seen Linus rant time and >> > > time again about this - why is it OK now? >> > >> > What the hell are you talking about? Nobody is breaking userland >> > interface. A new version of interface is being phased in and the old >> > one will stay there for the foreseeable future. It will be phased out >> > eventually but that's gonna take a long time and it will have to be >> > something hardly noticeable. Of course new features will only be >> > available with the new interface and there will be efforts to nudge >> > people away from the old one but the existing interface will keep >> > working it does. >> >> I can understand some alarm. When I saw the below I started frothing at >> the face and howling at the moon, and I don't even use the things much. >> >> http://lists.freedesktop.org/archives/systemd-devel/2013-June/011521.html >> >> Hierarchy layout aside, that "private property" bit says that the folks >> who currently own and use the cgroups interface will lose direct access >> to it. I can imagine folks who have become dependent upon an on the fly >> management agents of their own design becoming a tad alarmed. > > FWIW, the code is too embarassing yet to see daylight, but I'm playing > with a very lowlevel cgroup manager which supports nesting itself. > Access in this POC is low-level ("set freezer.state to THAWED for cgroup > /c1/c2", "Create /c3"), but the key feature is that it can run in two > modes - native mode in which it uses cgroupfs, and child mode where it > talks to a parent manager to make the changes. In this world, are users able to read cgroup files, or do they have to go through a central agent, too? > So then the idea would be that userspace (like libvirt and lxc) would > talk over /dev/cgroup to its manager. Userspace inside a container > (which can't actually mount cgroups itself) would talk to its own > manager which is talking over a passed-in socket to the host manager, > which in turn runs natively (uses cgroupfs, and nests "create /c1" under > the requestor's cgroup). How do you handle updates of this agent? Suppose I have hundreds of running containers, and I want to release a new version of the cgroupd ? (note: inquiries about the implementation do not denote acceptance of the model :) > At some point (probably soon) we might want to talk about a standard API > for these things. However I think it will have to come in the form of > a standard library, which knows to either send requests over dbus to > systemd, or over /dev/cgroup sock to the manager. > > -serge _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
