From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758324Ab2IEJ1G (ORCPT ); Wed, 5 Sep 2012 05:27:06 -0400 Received: from casper.infradead.org ([85.118.1.10]:50549 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751257Ab2IEJ1E convert rfc822-to-8bit (ORCPT ); Wed, 5 Sep 2012 05:27:04 -0400 Message-ID: <1346837209.2600.14.camel@twins> Subject: Re: [RFC 0/5] forced comounts for cgroups. From: Peter Zijlstra To: Glauber Costa Cc: Tejun Heo , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, davej@redhat.com, ben@decadent.org.uk, pjt@google.com, lennart@poettering.net, kay.sievers@vrfy.org Date: Wed, 05 Sep 2012 11:26:49 +0200 In-Reply-To: <50471782.6060800@parallels.com> 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> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.