From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965220AbaEMPJ6 (ORCPT ); Tue, 13 May 2014 11:09:58 -0400 Received: from cantor2.suse.de ([195.135.220.15]:58477 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932694AbaEMPJ4 (ORCPT ); Tue, 13 May 2014 11:09:56 -0400 Date: Tue, 13 May 2014 17:09:53 +0200 From: Michal Hocko To: Johannes Weiner 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: <20140513150953.GC25996@dhcp22.suse.cz> 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> <20140513131655.GC18849@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140513131655.GC18849@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 Tue 13-05-14 09:16:56, Johannes Weiner wrote: > On Mon, May 12, 2014 at 05:34:58PM +0200, Michal Hocko wrote: [...] > > >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. Well, I suspect that most users will try the new semantic at the latest possible moment and then it can come up as a surprise. I would prefer to catch those as soon as possible. I am even thinking to push this to SLES to catch possible enterprise users. > Acked-by: Johannes Weiner Thanks. OK, I will post it to Andrew. I guess he will want to have some rate-limiting or print-once semantic... -- Michal Hocko SUSE Labs