Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753426AbaKCRCg (ORCPT ); Mon, 3 Nov 2014 12:02:36 -0500 Received: from cantor2.suse.de ([195.135.220.15]:56766 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753393AbaKCRCc (ORCPT ); Mon, 3 Nov 2014 12:02:32 -0500 Date: Mon, 3 Nov 2014 18:02:28 +0100 From: Michal Hocko To: Johannes Weiner Cc: Joonsoo Kim , Andrew Morton , Vladimir Davydov , Tejun Heo , David Miller , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 1/3] mm: embed the memcg pointer directly into struct page Message-ID: <20141103170228.GH10156@dhcp22.suse.cz> References: <1414898156-4741-1-git-send-email-hannes@cmpxchg.org> <20141103080208.GA7052@js1304-P5Q-DELUXE> <20141103150942.GA32052@phnom.home.cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141103150942.GA32052@phnom.home.cmpxchg.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 03-11-14 10:09:42, Johannes Weiner wrote: > Hi Joonsoo, > > On Mon, Nov 03, 2014 at 05:02:08PM +0900, Joonsoo Kim wrote: > > On Sat, Nov 01, 2014 at 11:15:54PM -0400, Johannes Weiner wrote: > > > Memory cgroups used to have 5 per-page pointers. To allow users to > > > disable that amount of overhead during runtime, those pointers were > > > allocated in a separate array, with a translation layer between them > > > and struct page. > > > > Hello, Johannes. > > > > I'd like to leave this translation layer. > > Could you just disable that code with #ifdef until next user comes? > > > > In our company, we uses PAGE_OWNER on mm tree which is the feature > > saying who allocates the page. To use PAGE_OWNER needs modifying > > struct page and then needs re-compile. This re-compile makes us difficult > > to use this feature. So, we decide to implement run-time configurable > > PAGE_OWNER through page_cgroup's translation layer code. Moreover, with > > this infrastructure, I plan to implement some other debugging feature. > > > > Because of my laziness, it didn't submitted to LKML. But, I will > > submit it as soon as possible. If the code is removed, I would > > copy-and-paste the code, but, it would cause lose of the history on > > that code. So if possible, I'd like to leave that code now. > > Please re-introduce this code when your new usecase is ready to be > upstreamed. There is little reason to burden an unrelated feature > with a sizable chunk of dead code for a vague future user. Completely agreed! I would hate to have some random feature piggy back on memcg internal structures. For that to be acceptable the page_cgroup would have to be abstracted into a more generic structure which wouldn't be under CONFIG_MEMCG anyway. -- Michal Hocko SUSE Labs -- 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/