From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935782Ab3DITLx (ORCPT ); Tue, 9 Apr 2013 15:11:53 -0400 Received: from mail-qa0-f52.google.com ([209.85.216.52]:59289 "EHLO mail-qa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935459Ab3DITLv (ORCPT ); Tue, 9 Apr 2013 15:11:51 -0400 Date: Tue, 9 Apr 2013 12:11:45 -0700 From: Tejun Heo To: Lennart Poettering Cc: Glauber Costa , Li Zefan , containers@lists.linux-foundation.org, cgroups@vger.kernel.org, Kay Sievers , linux-kernel@vger.kernel.org, jpoimboe@redhat.com, dhaval.giani@gmail.com, workman-devel@redhat.com Subject: Re: cgroup: status-quo and userland efforts Message-ID: <20130409191145.GI6186@mtj.dyndns.org> References: <20130406012159.GA17159@mtj.dyndns.org> <5162CA21.4060108@parallels.com> <51635371.7070104@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51635371.7070104@redhat.com> 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 Hello, On Tue, Apr 09, 2013 at 01:32:01AM +0200, Lennart Poettering wrote: > The other big thing we want from the systemd side is saner > notifications when cgroups run empty. i.e. currently we don't get > these at all in containers (since the agent can be only installed > once, for the host). And the way we get this is awful, via > kernel-spawned processes. I am looking for a way how I can establish > a watch on a certain subtree (not just one directory) and get simple > notifications in a race-free whenever a cgroup runs empty. Oh yeah, it's horrifying. There was something going on a while ago but I couldn't get hold of Eric Paris. We probably should resurrect that patch. As for delegating to namespaces, I'm not exactly sure what to do. At least for now, it could be an acceptable trade-off to delegate the subdirectory with some limits on the number of cgroups / depth of hierarchy / whatever. That said, I'm not really fond of the idea. It isn't likely to work seamlessly. The root cgroup is special anyway and I don't really like the idea of putting NS related stuff directly into cgroupfs. Thanks. -- tejun