From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH v2] memcg: first step towards hierarchical controller Date: Tue, 4 Sep 2012 12:29:42 +0400 Message-ID: <5045BBF6.5000900@parallels.com> References: <1346687211-31848-1-git-send-email-glommer@parallels.com> <20120903164148.GS29217@decadent.org.uk> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120903164148.GS29217-/+tVBieCtBitmTQ+vhA3Yw@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Ben Hutchings Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Dave Jones , Peter Zijlstra , Paul Turner , Lennart Poettering , Kay Sievers , Michal Hocko , Kamezawa Hiroyuki , Johannes Weiner , Tejun Heo > >> + of the root memcg, regardless of their positioning in the tree. >> + >> + Use of flat hierarchies is highly discouraged, but has been the >> + default for performance reasons for quite some time. Setting this flag >> + to on will make hierarchical accounting the default. It is still >> + possible to set it back to flat by writing 0 to the file >> + memory.use_hierarchy, albeit discouraged. Distributors are encouraged >> + to set this option. > [...] > > I don't think that 'default n' is effective encouragement! > > Ben. > If it were up to me, I would just flip it to 1. No option. A bit of history here, is that people have a - quite valid - concern that this will disrupt users using their own kernel, should they decide to update, recompile and run. Conditional on a Kconfig option, people reusing their .config will see no change. Distros, otoh, are versioned. It is not unreasonable to expect a behavior change when a major version flips. The encouragement here comes not from the default, but from the acknowledgment that his thing is totally broken, and we need to act to fix it in a compatible way.