From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758303Ab2IEJfQ (ORCPT ); Wed, 5 Sep 2012 05:35:16 -0400 Received: from mx2.parallels.com ([64.131.90.16]:53594 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758099Ab2IEJfO (ORCPT ); Wed, 5 Sep 2012 05:35:14 -0400 Message-ID: <50471C0C.7050600@parallels.com> Date: Wed, 5 Sep 2012 13:31:56 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Tejun Heo , , , , , , , , Subject: Re: [RFC 0/5] forced comounts for cgroups. References: <1346768300-10282-1-git-send-email-glommer@parallels.com> <20120904214602.GA9092@dhcp-172-17-108-109.mtv.corp.google.com> <5047074D.1030104@parallels.com> <20120905081439.GC3195@dhcp-172-17-108-109.mtv.corp.google.com> <50470A87.1040701@parallels.com> <20120905082947.GD3195@dhcp-172-17-108-109.mtv.corp.google.com> <50470EBF.9070109@parallels.com> <20120905084740.GE3195@dhcp-172-17-108-109.mtv.corp.google.com> <1346835993.2600.9.camel@twins> <20120905091140.GH3195@dhcp-172-17-108-109.mtv.corp.google.com> <50471782.6060800@parallels.com> <1346837209.2600.14.camel@twins> In-Reply-To: <1346837209.2600.14.camel@twins> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/2012 01:26 PM, Peter Zijlstra wrote: > On Wed, 2012-09-05 at 13:12 +0400, Glauber Costa wrote: >> On 09/05/2012 01:11 PM, Tejun Heo wrote: >>> Hello, Peter. >>> >>> On Wed, Sep 05, 2012 at 11:06:33AM +0200, Peter Zijlstra wrote: >>>> *confused* I always thought that was exactly what you meant with unified >>>> hierarchy. >>> >>> No, I never counted out differing granularity. >>> >> >> Can you elaborate on which interface do you envision to make it work? >> They will clearly be mounted in the same hierarchy, or as said >> alternatively, comounted. >> >> If you can turn them on/off on a per-subtree basis, which interface >> exactly do you propose for that? > > I wouldn't, screw that. That would result in the exact same problem > we're trying to fix. I want a single hierarchy walk, that's expensive > enough. > >> Would a pair of cgroup core files like available_controllers and >> current_controllers are a lot of drivers do, suffice? > > No.. its not a 'feature' I care to support for 'my' controllers. > > I simply don't want to have to do two (or more) hierarchy walks for > accounting on every schedule event, all that pointer chasing is stupidly > expensive. > You wouldn't have to do more than one hierarchy walks for that. What Tejun seems to want, is the ability to not have a particular controller at some point in the tree. But if they exist, they are always together.