From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754980AbZA1N5T (ORCPT ); Wed, 28 Jan 2009 08:57:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752149AbZA1N4b (ORCPT ); Wed, 28 Jan 2009 08:56:31 -0500 Received: from casper.infradead.org ([85.118.1.10]:47055 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751910AbZA1N4a (ORCPT ); Wed, 28 Jan 2009 08:56:30 -0500 Message-Id: <20090128135253.688841942@chello.nl> References: <20090128135137.632938951@chello.nl> User-Agent: quilt/0.46-1 Date: Wed, 28 Jan 2009 14:51:39 +0100 From: Peter Zijlstra To: mingo@elte.hu, efault@gmx.de Cc: linux-kernel@vger.kernel.org, Peter Zijlstra Subject: [PATCH 2/3] sched: clear buddies more aggressively Content-Disposition: inline; filename=sched-clear-buddies.patch X-Bad-Reply: References but no 'Re:' in Subject. Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mike Galbraith It was noticed that a task could get re-elected past its run quota due to buddy affinities. This could increase latency a little. Cure it by more aggresively clearing buddy state. We do so in two situations: - when we force preempt - when we select a buddy to run Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra --- kernel/sched_fair.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) Index: linux-2.6/kernel/sched_fair.c =================================================================== --- linux-2.6.orig/kernel/sched_fair.c +++ linux-2.6/kernel/sched_fair.c @@ -768,8 +768,14 @@ check_preempt_tick(struct cfs_rq *cfs_rq ideal_runtime = sched_slice(cfs_rq, curr); delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; - if (delta_exec > ideal_runtime) + if (delta_exec > ideal_runtime) { resched_task(rq_of(cfs_rq)->curr); + /* + * The current task ran long enough, ensure it doesn't get + * re-elected due to buddy favours. + */ + clear_buddies(cfs_rq, curr); + } } static void @@ -1492,6 +1498,11 @@ static struct task_struct *pick_next_tas do { se = pick_next_entity(cfs_rq); + /* + * If se was a buddy, clear it so that it will have to earn + * the favour again. + */ + clear_buddies(cfs_rq, se); set_next_entity(cfs_rq, se); cfs_rq = group_cfs_rq(se); } while (cfs_rq); --