From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755566Ab2CMQAD (ORCPT ); Tue, 13 Mar 2012 12:00:03 -0400 Received: from mail-gx0-f174.google.com ([209.85.161.174]:51938 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751380Ab2CMQAA (ORCPT ); Tue, 13 Mar 2012 12:00:00 -0400 Date: Tue, 13 Mar 2012 08:59:55 -0700 From: Tejun Heo To: Vivek Goyal Cc: Peter Zijlstra , Li Zefan , containers@lists.linux-foundation.org, cgroups@vger.kernel.org, Andrew Morton , Kay Sievers , Lennart Poettering , Frederic Weisbecker , linux-kernel@vger.kernel.org, Michal Schmidt Subject: Re: [RFD] cgroup: about multiple hierarchies Message-ID: <20120313155955.GB7349@google.com> References: <20120221211938.GE12236@google.com> <20120312221050.GG23255@google.com> <1331590938.18960.57.camel@twins> <20120312222817.GI23255@google.com> <20120313140345.GC29169@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120313140345.GC29169@redhat.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 Hey, Vivek. On Tue, Mar 13, 2012 at 10:03:45AM -0400, Vivek Goyal wrote: > > With root being treated specially, probably as just being a equal > > group as other groups, I'm not fully determined about that yet. > > So what wrong with flattening the whole hierarchy and all groups being active > in the path? It is not worse then second option? > > root > / | | | \ > G1 G2 G3 G31 G32 It is worse because while there isn't much need for orthogonal hierarchies, people often need to apply different limits at different levels of the hierarchy for different controllers. ie. it often happens that the distinction between G31 and G32 matters for one controller but not for others. The problem with flattening like you suggested above is that it isn't a hierarchy at all - membership isn't recursive. Imposing limits at single level is an additional restriction and may cause some config complexity but it'll be at least explicit and can co-exist with full hierarchy in meaningful way. Thanks. -- tejun