From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755297AbZDHWcW (ORCPT ); Wed, 8 Apr 2009 18:32:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754028AbZDHWcM (ORCPT ); Wed, 8 Apr 2009 18:32:12 -0400 Received: from smtp-out.google.com ([216.239.33.17]:1340 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753973AbZDHWcK (ORCPT ); Wed, 8 Apr 2009 18:32:10 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:to:subject:message-id:user-agent:mime-version:content-type; b=cBeq658E5rD5ufAW2uBi19RXwMF/bIrulnsVwo2oetbfR29vFyd2ROBdhMkR7hows TPihTcAvXOvbhiT6IggKg== Date: Wed, 8 Apr 2009 15:29:43 -0700 (PDT) From: Paul Turner To: mingo@elte.hu, peterz@infradead.org, linux-kernel@vger.kernel.org Subject: sched: remove redundant hierarchy walk in check_preempt_wakeup Message-ID: User-Agent: Alpine 1.00 (DEB 882 2007-12-20) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ingo, Peter, In check_preempt_wakeup we walk up until both entities are queued on the same cfs_rq. After the iteration of vruntime vs wall-clock pre-emption changes the current check now checks at every level of the tree above this. However, unless I'm missing something at this point they should have a common parent. Thanks, - Paul -- sched: remove redundant hierarchy walk in check_preempt_wakeup Under group scheduling we traverse up until we are at common siblings to make the wakeup comparison on. At this point however, they should have the same parent so continuing to check up the tree is redundant. Signed-off-by: Paul Turner --- kernel/sched_fair.c | 13 +++---------- 1 files changed, 3 insertions(+), 10 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 3816f21..5f9650e 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1487,17 +1487,10 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync) find_matching_se(&se, &pse); - while (se) { - BUG_ON(!pse); + BUG_ON(!pse); - if (wakeup_preempt_entity(se, pse) == 1) { - resched_task(curr); - break; - } - - se = parent_entity(se); - pse = parent_entity(pse); - } + if (wakeup_preempt_entity(se, pse) == 1) + resched_task(curr); } static struct task_struct *pick_next_task_fair(struct rq *rq) -- 1.5.4.3