From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932354AbcFOGjQ (ORCPT ); Wed, 15 Jun 2016 02:39:16 -0400 Received: from mga04.intel.com ([192.55.52.120]:32433 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932227AbcFOGjO (ORCPT ); Wed, 15 Jun 2016 02:39:14 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,475,1459839600"; d="scan'208";a="719277896" Date: Wed, 15 Jun 2016 06:42:18 +0800 From: Yuyang Du To: Mike Galbraith Cc: Peter Zijlstra , LKML Subject: Re: [rfc patch] sched/fair: Use instantaneous load for fork/exec balancing Message-ID: <20160614224218.GK8105@intel.com> References: <1465891111.1694.13.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1465891111.1694.13.camel@gmail.com> 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 Tue, Jun 14, 2016 at 09:58:31AM +0200, Mike Galbraith wrote: > SUSE's regression testing noticed that... > > 0905f04eb21f sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task() > > ...introduced a hackbench regression, and indeed it does. I think this > regression has more to do with randomness than anything else, but in > general... > > While averaging calms down load balancing, helping to keep migrations > down to a dull roar, it's not completely wonderful when it comes to > things that live in the here and now, hackbench being one such. > > time sh -c 'for i in `seq 1000`; do hackbench -p -P > /dev/null; done' > > real 0m55.397s > user 0m8.320s > sys 5m40.789s > > echo LB_INSTANTANEOUS_LOAD > /sys/kernel/debug/sched_features > > real 0m48.049s > user 0m6.510s > sys 5m6.291s > > Signed-off-by: Mike Galbraith I am entirely for giving it a "clear unadulterated reality", and even more for it an option. Reviewed-by: Yuyang Du