From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423156AbcFHIoX (ORCPT ); Wed, 8 Jun 2016 04:44:23 -0400 Received: from foss.arm.com ([217.140.101.70]:51003 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161825AbcFHIoU (ORCPT ); Wed, 8 Jun 2016 04:44:20 -0400 Date: Wed, 8 Jun 2016 09:45:16 +0100 From: Morten Rasmussen To: Peter Zijlstra Cc: mingo@redhat.com, dietmar.eggemann@arm.com, yuyang.du@intel.com, vincent.guittot@linaro.org, mgalbraith@suse.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/16] sched: Make SD_BALANCE_WAKE a topology flag Message-ID: <20160608084515.GD9187@e105550-lin.cambridge.arm.com> References: <1464001138-25063-1-git-send-email-morten.rasmussen@arm.com> <1464001138-25063-8-git-send-email-morten.rasmussen@arm.com> <20160601201817.GF28447@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160601201817.GF28447@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 01, 2016 at 10:18:17PM +0200, Peter Zijlstra wrote: > On Mon, May 23, 2016 at 11:58:49AM +0100, Morten Rasmussen wrote: > > For systems with the SD_ASYM_CPUCAPACITY flag set on higher level in the > > sched_domain hierarchy we need a way to enable wake-up balancing for the > > lower levels as well as we may want to balance tasks that don't fit the > > capacity of the previous cpu. > > > > We have the option of introducing a new topology flag to express this > > requirement, or let the existing SD_BALANCE_WAKE flag be set by the > > architecture as a topology flag. The former means introducing yet > > another flag, the latter breaks the current meaning of topology flags. > > None of the options are really desirable. > > So why can't you couple this to ASYM_CAPACITY? If that's set anywhere, > add BALANCE_WAKE as appropriate? That should be possible. It is set at the sched_domain levels that span cpus of different capacity, but we need to set BALANCE_WAKE on the level below as well. So we would have to introduce a dependency between flags set at different levels. However, following the discussion with Vincent on enabling WAKE_AFFINE across cpus of different capacity, I might be able to repurpose ASYM_CPUCAPACITY to set BALANCE_WAKE instead which would be simpler I think.