Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753747Ab2BWR3X (ORCPT ); Thu, 23 Feb 2012 12:29:23 -0500 Received: from mail-pw0-f46.google.com ([209.85.160.46]:48524 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753185Ab2BWR3V (ORCPT ); Thu, 23 Feb 2012 12:29:21 -0500 Date: Thu, 23 Feb 2012 09:29:15 -0800 From: Tejun Heo To: "Serge E. Hallyn" Cc: Glauber Costa , Frederic Weisbecker , containers@lists.linux-foundation.org, Kay Sievers , linux-kernel@vger.kernel.org, Christoph Hellwig , Lennart Poettering , cgroups@vger.kernel.org, Andrew Morton Subject: Re: [RFD] cgroup: about multiple hierarchies Message-ID: <20120223172915.GC22536@google.com> References: <20120221211938.GE12236@google.com> <20120221212106.GF12236@google.com> <4F44EEE4.2000809@parallels.com> <20120223074526.GA15835@mail.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120223074526.GA15835@mail.hallyn.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2665 Lines: 61 Hey, Serge. On Thu, Feb 23, 2012 at 07:45:26AM +0000, Serge E. Hallyn wrote: > > >>Documentation/cgroups.txt seems to be written with this consideration > > >>on mind. It's giving an example of applying limits accoring to two > > >>orthogonal categorizations - user groups (profressors, students...) > > >>and applications (WWW, NFS...). While it may sound like a valid use > > >>case, I'm very skeptical how useful or common mixing such orthogonal > > >>categorizations in a single setup would be. > > My first inclination is to agree, but counterexamples do come to mind. > > I could imagine a site saying "users can run (X) (say, ftpds), but the > memory consumed by all those ftpds must not be > 10% total RAM". At > the same time, they may run several apaches but want them all locked to > two of the cpus. Orthogonal hierarchies is a feature and it does allow use cases which aren't possible to support otherwise. It's not too difficult to come up with a use case crafted to exploit the feature. The main thing is whether the added functionality justifies the complexity and other disadvantages described earlier in the thread. To me, the scenarios seem not realistic, common place or essential enough. Also, it's not like there's only one problem to solve these issues. It may not be exactly the same thing but that's just part of the trade-off game we all play. > It might be worth a formal description of the new limits on use cases > such changes (both dropping support for orthogonal cgroups, and limiting > cgroups hierarchies to a mirror pstrees, separately) would bring. The word "formal" scares me. :) > To me personally the hierarchy limitation is more worrying. There have > been times when I've simply created cgroups for 'compile' and 'image > build', with particular cpu and memory limits. If I started a second > simultaneous compile, I'd want both compiles confined together. (That's > not to say the simplification might not be worth it, just bringing up > the other side) Yeah, that's an interesting point, but wouldn't something like the following work too? 1. create_cgroup --cpu 40% --mem 20% screen 2. tell screen to create as many build screens you want 3. issue builds from those screens To me, something like the above seems far more consistent with everything else we have on the system than moving tasks around by echoing pids to some sysfs file. Thanks. -- tejun -- 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/