From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 2/2] memcg: first step towards hierarchical controller Date: Tue, 26 Jun 2012 15:14:52 -0700 Message-ID: <20120626221452.GA15811@google.com> References: <1340725634-9017-1-git-send-email-glommer@parallels.com> <1340725634-9017-3-git-send-email-glommer@parallels.com> <20120626180451.GP3869@google.com> <20120626220809.GA4653@tiehlicka.suse.cz> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=rCyhkuSGAjpsQ7g50mv9r9zgkQKYj2j9pNUYDS7KOXA=; b=fS6rZksvbiIjTK2l4JXK0LwczuzVOiFw8xlFLkZWGIDKGZThA3LyTB7ePmcAf0Wwvu 2nKsUTE2Flhp4K7HHCOEdikFEqXNRANuSND7xKiaTp1ircvoLREyN0ZDIGLIeOw25JwR 1fezFFGqa0nNOv+2ZtS8IdBENtdKJIaXeEggLEqu0RoQaG95AWw+nrBPY791NfBxm84I 2rldh4g8nCXY05l47EQlb6W2jEjyAoG4AcSv32wOIK/SdLiGtBYn+JCtLA1nWrXLBG0E F/RnoGcS/BvjrJPENGaDwfXyJJthTEYt+pPQb5ldnHlM0HPJn6y4DPMCVbvvm3iLHbQP J1bQ== Content-Disposition: inline In-Reply-To: <20120626220809.GA4653-VqjxzfR4DlwKmadIfiO5sKVXKuFTiq87@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michal Hocko Cc: Glauber Costa , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Johannes Weiner , Andrew Morton Hello, Michal. On Wed, Jun 27, 2012 at 12:08:09AM +0200, Michal Hocko wrote: > According to my experience, people usually create deeper subtrees > just because they want to have memcg hierarchy together with other > controller(s) and the other controller requires a different topology > but then they do not care about memory.* attributes in parents. > Those cases are not affected by this change because parents are > unlimited by default. > Deeper subtrees without hierarchy and independent limits are usually > mis-configurations, and we would like to hear about those to help to fix > them, or they are unfixable usecases which we want to know about as well > (because then we have a blocker for the unified cgroup hierarchy, don't > we). Yeah, this is something I'm seriously considering doing from cgroup core. ie. generating a warning message if the user nests cgroups w/ controllers which don't support full hierarchy. > > Note that the default should still be flat hierarchy. > > > > 2. Mark flat hierarchy deprecated and produce a warning message if > > memcg is mounted w/o hierarchy option for a year or two. > > I would agree with you on this with many kernel configurables but > this one doesn't fall in. There is a trivial fallback (set root to > use_hierarchy=0) so the mount option seems like an overkill - yet > another API to keep for some time... Just disallow clearing .use_hierarchy if it was mounted with the option? We can later either make the file RO 1 for compatibility's sake or remove it. > So in short, I do think we should go the sanity path and end up > with hierarchical trees and sooner we start the better. I do agree with you in principle, but I still don't think we can switch the default behavior underneath the users. Thanks. -- tejun