Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752952AbbFCFvI (ORCPT ); Wed, 3 Jun 2015 01:51:08 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:34344 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752191AbbFCFvE (ORCPT ); Wed, 3 Jun 2015 01:51:04 -0400 Date: Wed, 3 Jun 2015 14:50:57 +0900 From: Tejun Heo To: John Stultz Cc: lkml , Li Zefan , Jonathan Corbet , cgroups@vger.kernel.org, Android Kernel Team , Rom Lemarchand , Colin Cross , Johannes Weiner Subject: Re: [RFC][PATCH 0/2] Android style loosening of cgroup attach permissions Message-ID: <20150603055057.GE20091@mtj.duckdns.org> References: <1432179674-19154-1-git-send-email-john.stultz@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1996 Lines: 46 Hello, John. On Tue, Jun 02, 2015 at 12:07:23PM -0700, John Stultz wrote: > On Wed, May 20, 2015 at 8:41 PM, John Stultz wrote: > > As a heads up, this is just a first RFC and not a submission. > > > > Android currently loosens the cgroup attchment permissions, allowing > > tasks with CAP_SYS_NICE to be able to allow tasks to move arbitrary > > tasks across cgroups. > > > > At first glance, overloading CAP_SYS_NICE seems a bit hackish, but this > > shows that there is a active and widely deployed use for different cgroup > > attachment rules then what is currently available. > > > > I've tried to rework the patches so this attachment policy is build > > time configurable, and wanted to send them out for review so folks > > might give their thoughts on this implementation and what they might > > see as a better way to go about achieving the same goal. > > > > Thoughts and feedback would be appriciated! > > Ping? Not sure if I hit folks at a busy time or if I didn't cc the right folks? Can you explain why this is necessary? android's cgroups usage is pretty weird at this point. IIRC, it moves tasks between fg and bg cgroups with memory immigration turned on which basically forces memcg to walk every single page relabeling them on each fg/bg switch, which is a pretty silly thing to do and for this android kernel also removes a rcu sync operation which makes break things on removal of cgroups, which android doesn't do. memcg usage came up a while ago and there wasn't anything major which can't be achieved (usually better) by following more standard cgroup usage - changing knobs rather than moving tasks around. Given that, I'm not sure this patchset makes sense for upstream. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/