From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757639Ab2DFS62 (ORCPT ); Fri, 6 Apr 2012 14:58:28 -0400 Received: from casper.infradead.org ([85.118.1.10]:36545 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754453Ab2DFS60 (ORCPT ); Fri, 6 Apr 2012 14:58:26 -0400 Subject: Re: [patch 0/2] cpusets, cpu_cgroup: disallow attaching kthreadd From: Peter Zijlstra To: Tejun Heo Cc: David Rientjes , Mike Galbraith , Andrew Morton , Ingo Molnar , Paul Menage , LKML , Li Zefan In-Reply-To: <20120406155203.GA4798@dhcp-172-17-108-109.mtv.corp.google.com> References: <20120405160829.GA12854@google.com> <20120405213704.GA29517@google.com> <20120405222400.GC29517@google.com> <20120405225854.GE29517@google.com> <20120405231306.GF29517@google.com> <20120406155203.GA4798@dhcp-172-17-108-109.mtv.corp.google.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 06 Apr 2012 20:26:10 +0200 Message-ID: <1333736770.2960.114.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2012-04-06 at 08:52 -0700, Tejun Heo wrote: > Hello, David. > > On Thu, Apr 05, 2012 at 04:40:06PM -0700, David Rientjes wrote: > > Well, I'm fussing over it because the patch being considered unnecessary > > requires that kthreadd can't be moved anywhere and I know one company is > > trying to move in a direction where nothing is in the root memcg. > > "Nothing in the root memcg" can't be a goal in and of itself. You > want that to achieve some functional goal and I'm trying to say this > specific kthreadd change doesn't necessarily affect the goal - better > accounting - all that much. If root group is gonna be completely > empty otherwise, just combine information from it. Even if that > doesn't work, assigning specific kthreads to appropriate cgroups after > the creation wouldn't be too far off. I just don't see how relevant > it actually would be. > > If we want all controlles to play by the same rules, which is > necessary for having a unified hierarchy, I wanna keep those rules > simple. If bound kthreads in !root cgroups cause issues for some and > there aren't quite strong reasons to do otherwise, I would just > restrict them in the root. It's not like those kthreads are > cgroup-aware in any form anyway. > > I don't know. Just proceed without kthreadd in the root. If the > fallouts are big enough and can't be easily worked around, let's talk > then. Furthermore, the whole point of kthreadd's existence is so that we could create kthreads without context. Placing it in a cgroup will ensure all subsequently created kthreads do have context (including possible idle threads). This seems like a particularly bad idea.