From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753865AbaG2OxM (ORCPT ); Tue, 29 Jul 2014 10:53:12 -0400 Received: from casper.infradead.org ([85.118.1.10]:37949 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753224AbaG2OxK (ORCPT ); Tue, 29 Jul 2014 10:53:10 -0400 Date: Tue, 29 Jul 2014 16:53:08 +0200 From: Peter Zijlstra To: riel@redhat.com Cc: linux-kernel@vger.kernel.org, vincent.guittot@linaro.org, mikey@neuling.org, mingo@kernel.org, jhladky@redhat.com, ktkhai@parallels.com, tim.c.chen@linux.intel.com, nicolas.pitre@linaro.org Subject: Re: [PATCH 1/2] sched: fix and clean up calculate_imbalance Message-ID: <20140729145308.GV12054@laptop.lan> References: <1406571388-3227-1-git-send-email-riel@redhat.com> <1406571388-3227-2-git-send-email-riel@redhat.com> <20140729144952.GG3935@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140729144952.GG3935@laptop> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 29, 2014 at 04:49:52PM +0200, Peter Zijlstra wrote: > > @@ -6247,32 +6247,15 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s > > return fix_small_imbalance(env, sds); > > } > > > > - if (!busiest->group_imb) { > > - /* > > - * Don't want to pull so many tasks that a group would go idle. > > - * Except of course for the group_imb case, since then we might > > - * have to drop below capacity to reach cpu-load equilibrium. > > - */ > > - load_above_capacity = > > - (busiest->sum_nr_running - busiest->group_capacity_factor); > > - > > - load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE); > > - load_above_capacity /= busiest->group_capacity; > > - } > > I think we want to retain that, esp. for the overloaded case. So that > wants to be: > > if (busiest->sum_nr_running > busiest->group_capacity_factor) > > Clearly it doesn't make sense for the !overload case, and we explicitly > want to avoid it in the imb case. Ah, wait, I think I see why you want that gone. I was only expecting a correction fix wrt changing pick_busiest(), not also behaviour changes. Lemme reconsider.