From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753995AbaG2RFH (ORCPT ); Tue, 29 Jul 2014 13:05:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40402 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751321AbaG2RFF (ORCPT ); Tue, 29 Jul 2014 13:05:05 -0400 Message-ID: <53D7D412.4040203@redhat.com> Date: Tue, 29 Jul 2014 13:04:18 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Peter Zijlstra CC: Vincent Guittot , linux-kernel , Michael Neuling , Ingo Molnar , jhladky@redhat.com, ktkhai@parallels.com, tim.c.chen@linux.intel.com, Nicolas Pitre Subject: Re: [PATCH 1/2] sched: fix and clean up calculate_imbalance References: <1406571388-3227-1-git-send-email-riel@redhat.com> <1406571388-3227-2-git-send-email-riel@redhat.com> <20140729145910.GH3935@laptop> <53D7BAA5.8080404@redhat.com> <20140729154956.GJ3935@laptop> In-Reply-To: <20140729154956.GJ3935@laptop> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/29/2014 11:49 AM, Peter Zijlstra wrote: > On Tue, Jul 29, 2014 at 11:15:49AM -0400, Rik van Riel wrote: > >>> Right, so we want that code for overloaded -> overloaded >>> migrations such as not to cause idle cpus in an attempt to >>> balance things. Idle cpus are worse than imbalance. >>> >>> But in case of overloaded/imb -> !overloaded migrations we can >>> allow it, and in fact want to allow it in order to balance >>> idle cpus. >> >> In case the destination is over the average load, or the source >> is under the average load, fix_small_imbalance() determines >> env->imbalance. >> >> The "load_above_capacity" calculation is only reached when >> busiest is busier than average, and the destination is under the >> average load. In that case, env->imbalance ends up as the minimum >> of busiest - avg and avg - target. >> >> Is there any case where limiting it further to "load - capacity" >> from the busiest domain makes a difference? > > sadly yes; suppose 8 cpus in 2 groups and 9 tasks, 8 tasks of > weight 10, 1 of 1024. The local group will have 5 tasks of 10, the > busiest will have the remaining 4. Good point! Looks like your patches address all issues raised, and the code looks nicer than before. - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJT19QSAAoJEM553pKExN6DM+EH/A0VSAcLB5TIDOC9axBwxdtY RxDkYvGZJ9OvbsU83alpjm+ee5l1x+A1tKQofqd1QVDSfpq9QPrUniueeqnNyJhM /alIRP/09bmH8vdn0uTqVrrx/lESeNPop5KmWimAdm1s452Lz8iuU3KmZryGssyJ MolSWGKwNbWIncBLRtkNB7szlkLyvO0JZQN5FnA1xrzDZeaCA9j072t/49fiscbs t6O8LxxsyooM+Wj3KyNt5dSKb9kHKf9gg0Z1dwcEqpcBjTB1jZNwOLQfhhaXX4gX Gu55x8bJzFRMLey1EVtzlM7gnjpgiELbyfB7JibN0I8pYJKS9EcybCjQuq7BuvA= =dt7v -----END PGP SIGNATURE-----