From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx113.postini.com [74.125.245.113]) by kanga.kvack.org (Postfix) with SMTP id 29A406B005A for ; Tue, 26 Jun 2012 13:55:18 -0400 (EDT) Received: by pbbrp2 with SMTP id rp2so474995pbb.14 for ; Tue, 26 Jun 2012 10:55:17 -0700 (PDT) Date: Tue, 26 Jun 2012 10:55:13 -0700 From: Tejun Heo Subject: Re: [PATCH] fix bad behavior in use_hierarchy file Message-ID: <20120626175513.GO3869@google.com> References: <1340616061-1955-1-git-send-email-glommer@parallels.com> <20120625204908.GL3869@google.com> <20120626075653.GD6713@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120626075653.GD6713@tiehlicka.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Glauber Costa , cgroups@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , devel@openvz.org, Dhaval Giani , Kamezawa Hiroyuki , Johannes Weiner , Ying Han , gthelen@google.com Hello, On Tue, Jun 26, 2012 at 09:56:53AM +0200, Michal Hocko wrote: > [Adding Ying to CC - they are using hierarchies AFAIU in their workloads] Ooh, I'm they. :) Asking around.... okay, so google does use .use_hierarchy but it's a tree-wide thing and would be perfectly happy with a global switch. > On Mon 25-06-12 13:49:08, Tejun Heo wrote: > [...] > > A bit of delta but is there any chance we can either deprecate > > .use_hierarhcy or at least make it global toggle instead of subtree > > thing? > > So what you are proposing is to have all subtrees of the root either > hierarchical or not, right? Yeap. Just make it a global switch. Probably determined on mount time. > > This seems needlessly complicated. :( > > Toggle wouldn't help much I am afraid. We would still have to > distinguish (non)hierarchical cases. And I am not sure we can make > everything hierarchical easily. I'm kinda confused by this paragraph. What do you mean by "wouldn't help much"? Do you mean in terms of complexity? > Most users (from my experience) ignored use_hierarchy for some reasons > and the end results might be really unexpected for them if they used > deeper subtrees (which might be needed due to combination with other > controller(s)). Oh yeah, we can't change the default behavior like that. The transition should be a lot more gradual. Even if making .use_hierarchy doesn't help much in terms of reducing complexity right now, it would at least allow us to weed out and prevent wacky woo-hoo mom-look-at-what-I-can-do configurations which will be a lot more difficult to deal with for both us and such users (if we end up forcing hierarchy). Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org