Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755489AbdCTRgR (ORCPT ); Mon, 20 Mar 2017 13:36:17 -0400 Received: from mail-yw0-f194.google.com ([209.85.161.194]:35092 "EHLO mail-yw0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753614AbdCTRgO (ORCPT ); Mon, 20 Mar 2017 13:36:14 -0400 Date: Mon, 20 Mar 2017 13:36:11 -0400 From: Tejun Heo To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra Subject: Re: [RFC v3 1/5] sched/core: add capacity constraints to CPU controller Message-ID: <20170320173611.GA7398@htj.duckdns.org> References: <1488292722-19410-1-git-send-email-patrick.bellasi@arm.com> <1488292722-19410-2-git-send-email-patrick.bellasi@arm.com> <20170320171511.GB3623@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170320171511.GB3623@htj.duckdns.org> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1228 Lines: 26 On Mon, Mar 20, 2017 at 01:15:11PM -0400, Tejun Heo wrote: > > a) are tunable at all hierarchy levels, i.e. root group too > > This usually is problematic because there should be a non-cgroup way > of configuring the feature in case cgroup isn't configured or used, > and it becomes awkward to have two separate mechanisms configuring the > same thing. Maybe the feature is cgroup specific enough that it makes > sense here but this needs more explanation / justification. A related issue here is that what the non-cgroup interface and its interaction with cgroup should be. In the long term, I think it's better to have a generic non-cgroup interface for these new features, and we've gotten it wrong, or at least inconsistent, across different settings - most don't affect API accessible settings and just confine the configuration requested by the application inside the cgroup constraints; however, cpuset does it the other way and overwrites configurations set by individual applications. If we agree that exposing this only through cgroup is fine, this isn't a concern, but, given that this is a thread property and can obviously be useful outside cgroups, that seems debatable at the very least. Thanks. -- tejun