From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932979AbaEMNWp (ORCPT ); Tue, 13 May 2014 09:22:45 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:60883 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753360AbaEMNWn (ORCPT ); Tue, 13 May 2014 09:22:43 -0400 Date: Tue, 13 May 2014 09:16:56 -0400 From: Johannes Weiner To: Michal Hocko Cc: Tejun Heo , lizefan@huawei.com, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] memcg: deprecate memory.force_empty knob Message-ID: <20140513131655.GC18849@cmpxchg.org> References: <1399671091-23867-1-git-send-email-tj@kernel.org> <1399671091-23867-3-git-send-email-tj@kernel.org> <20140512145324.GE9564@dhcp22.suse.cz> <20140512145803.GF9564@dhcp22.suse.cz> <20140512150014.GB1421@htj.dyndns.org> <20140512152015.GH9564@dhcp22.suse.cz> <20140512152507.GD1421@htj.dyndns.org> <20140512153458.GJ9564@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140512153458.GJ9564@dhcp22.suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 12, 2014 at 05:34:58PM +0200, Michal Hocko wrote: > On Mon 12-05-14 11:25:07, Tejun Heo wrote: > > On Mon, May 12, 2014 at 05:20:15PM +0200, Michal Hocko wrote: > > > On Mon 12-05-14 11:00:14, Tejun Heo wrote: > > > > On Mon, May 12, 2014 at 04:58:03PM +0200, Michal Hocko wrote: > > > > > @@ -4793,6 +4793,10 @@ static int mem_cgroup_force_empty_write(struct cgroup_subsys_state *css, > > > > > > > > > > if (mem_cgroup_is_root(memcg)) > > > > > return -EINVAL; > > > > > + pr_info("%s (%d): memory.force_empty is deprecated and will be removed.", > > > > > + current->comm, task_pid_nr(current)); > > > > > + pr_cont(" Let us know if you know if it needed in your usecase at"); > > > > > + pr_cont(" linux-mm@kvack.org\n"); > > > > > return mem_cgroup_force_empty(memcg); > > > > > > > > It probably would be way easier to just mark the knob with > > > > CFTYPE_INSANE. > > > > > > That would prevent from creating the file, right? I do not mind that but > > > I would like to see people complaining before. > > > > Oh sure, if you wanna see people complaining before the roll out of > > unified hierarchy, but let's make sure it's also marked with > > CFTYPE_INSANE. It's easy to remove the flag afterwards. The other > > way isn't, so... > --- > >From 6f2a33df7750f0794b03f7a85aba02a4e631f2a0 Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Mon, 12 May 2014 16:20:46 +0200 > Subject: [PATCH] memcg: deprecate memory.force_empty knob > > force_empty has been introduced primarily to drop memory before it gets > reparented on the group removal. This alone doesn't sound fully > justified because reparented pages which are not in use can be reclaimed > also later when there is a memory pressure on the parent level. > > Mark the knob CFTYPE_INSANE which tells the cgroup core that it > shouldn't create the knob with the experimental sane_behavior. Other > users will get informed about the deprecation and asked to tell us more. > But I expect that most users will be simply cgroup remove handlers > which do that since ever without having any good reason for it. > > If somebody really cares and the reparented pages, which would be dropped > otherwise, push out more important ones then we should fix the > reparenting code and put pages to the tail. > > Signed-off-by: Michal Hocko I'm skeptical the printk will do anything useful, but you marked the knob insane and that's the most important change. Acked-by: Johannes Weiner