Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752499Ab3F0NWU (ORCPT ); Thu, 27 Jun 2013 09:22:20 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:32890 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751530Ab3F0NWS (ORCPT ); Thu, 27 Jun 2013 09:22:18 -0400 Date: Thu, 27 Jun 2013 08:22:06 -0500 From: Serge Hallyn To: Mike Galbraith Cc: Tejun Heo , Tim Hockin , "linux-kernel@vger.kernel.org" , Containers , Kay Sievers , lpoetter , workman-devel , jpoimboe , "dhaval.giani" , Cgroups Subject: Re: cgroup: status-quo and userland efforts Message-ID: <20130627132206.GE4003@sergelap> References: <20130406012159.GA17159@mtj.dyndns.org> <20130422214159.GG12543@htj.dyndns.org> <20130625000118.GT1918@mtj.dyndns.org> <20130626212047.GB4536@htj.dyndns.org> <1372311907.5871.78.camel@marge.simpson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1372311907.5871.78.camel@marge.simpson.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2801 Lines: 54 Quoting Mike Galbraith (bitbucket@online.de): > 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. 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). 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/