Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752182AbbEDFjb (ORCPT ); Mon, 4 May 2015 01:39:31 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:36838 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbbEDFjX (ORCPT ); Mon, 4 May 2015 01:39:23 -0400 Message-ID: <1430717964.3129.62.camel@gmail.com> Subject: Re: [PATCH] sched: Relax a restriction in sched_rt_can_attach() From: Mike Galbraith To: Zefan Li Cc: Ingo Molnar , Peter Zijlstra , Tejun Heo , LKML , Cgroups Date: Mon, 04 May 2015 07:39:24 +0200 In-Reply-To: <1430716247.3129.44.camel@gmail.com> References: <5546C34C.7050202@huawei.com> <1430709236.3129.42.camel@gmail.com> <5546F80B.3070802@huawei.com> <1430716247.3129.44.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1773 Lines: 43 On Mon, 2015-05-04 at 07:10 +0200, Mike Galbraith wrote: > On Mon, 2015-05-04 at 12:39 +0800, Zefan Li wrote: > > > >> We are moving toward unified hierarchy where all the cgroup controllers > > >> are bound together, so it would make cgroups easier to use if we have less > > >> restrictions on attaching tasks between cgroups. > > > > > > Forcing group scheduling overhead on users if they want cpuset or memory > > > cgroup functionality would be far from wonderful. Am I interpreting the > > > implications of this unification/binding properly? > > > > > > (I hope not, surely the plan is not to utterly _destroy_ cgroup utility) > > > > > > > Some degree of flexibility is provided so that you may disable some controllers > > in a subtree. For example: > > > > root ---> child1 > > (cpuset,memory,cpu) (cpuset,memory) > > \ > > \-> child2 > > (cpu) > > Whew, that's a relief. Thanks. But somehow I'm not feeling a whole lot better. "May" means if you don't explicitly take some action to disable group scheduling, you get it (I don't care if I have an off button), but that would also seemingly mean that we would then have rt tasks in taskgroups with no bandwidth allocated, ie you have to make group scheduling for rt tasks meaningless until a bandwidth appeared, and to make bandwidth appear, you'd have to stop the world, distribute, continue, no? The current "just say no" seems a lot more sensible. -Mike -- 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/