From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753439Ab2AWQcx (ORCPT ); Mon, 23 Jan 2012 11:32:53 -0500 Received: from mail-gy0-f174.google.com ([209.85.160.174]:37390 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751122Ab2AWQcv (ORCPT ); Mon, 23 Jan 2012 11:32:51 -0500 Date: Mon, 23 Jan 2012 08:32:46 -0800 From: Tejun Heo To: Vivek Goyal Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 08/17] blkcg: shoot down blkio_groups on elevator switch Message-ID: <20120123163246.GG12652@google.com> References: <1327202725-3383-1-git-send-email-tj@kernel.org> <1327202725-3383-9-git-send-email-tj@kernel.org> <20120123152055.GD25986@redhat.com> <20120123153913.GB12652@google.com> <20120123155216.GF25986@redhat.com> <20120123155745.GD12652@google.com> <20120123161042.GG25986@redhat.com> <20120123161308.GH25986@redhat.com> <20120123162035.GF12652@google.com> <20120123162840.GJ25986@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120123162840.GJ25986@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 On Mon, Jan 23, 2012 at 11:28:40AM -0500, Vivek Goyal wrote: > Can we avoid integrating everything into single blkg. What's wrong with > separate blkg for separage policy. In this case we just don't have the > flexbility to change throttling policy. If it is compiled in, it gets > activated. The only configurable thing is IO scheduler and these groups > will be cleaned up. > > So keeping blkg separate for separate policy gives us this flexibility > that we don't have to cleanup throttling data and keep the throttling > rules persistent across elevator switch. I think that's the wrong trade off. We end up duplicating common stuff all over the place and the code to deal with the mess is naturally horrible and almost incomprehensible. Persistency is much more minor issue and should be handled as such. It shouldn't contort the whole design like it does now. Let's talk about persistency in the other reply. -- tejun