Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753650AbYH1J0x (ORCPT ); Thu, 28 Aug 2008 05:26:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751984AbYH1J0d (ORCPT ); Thu, 28 Aug 2008 05:26:33 -0400 Received: from viefep11-int.chello.at ([62.179.121.31]:60823 "EHLO viefep11-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751805AbYH1J0c (ORCPT ); Thu, 28 Aug 2008 05:26:32 -0400 Subject: Re: [patch] sched: call resched_task() conditionally from new task wake up path. From: Peter Zijlstra To: bharata@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, Srivatsa Vaddagiri , Ingo Molnar In-Reply-To: <20080828091249.GA3303@in.ibm.com> References: <20080828091249.GA3303@in.ibm.com> Content-Type: text/plain Date: Thu, 28 Aug 2008 11:25:07 +0200 Message-Id: <1219915507.6443.13.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1794 Lines: 60 On Thu, 2008-08-28 at 14:42 +0530, Bharata B Rao wrote: > Hi, > > sched: call resched_task() conditionally from new task wake up path. > > - During wake up of a new task, task_new_fair() can do a resched_task() > on the current task. Later in the code path, check_preempt_curr() also ends > up doing the same, which can be avoided. Check if TIF_NEED_RESCHED is > already set for the current task. > > - task_new_fair() does a resched_task() on the current task unconditionally. > This can be done only in case when child runs before the parent. > > Signed-off-by: Bharata B Rao > CC: Srivatsa Vaddagiri Acked-by: Peter Zijlstra > CC: Ingo Molnar > --- > kernel/sched_fair.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -1348,6 +1348,13 @@ static void check_preempt_wakeup(struct > if (unlikely(se == pse)) > return; > > + /* > + * We can come here with TIF_NEED_RESCHED already set from new task > + * wake up path. > + */ > + if (test_tsk_need_resched(curr)) > + return; > + > cfs_rq_of(pse)->next = pse; > > /* > @@ -1615,10 +1622,10 @@ static void task_new_fair(struct rq *rq, > * 'current' within the tree based on its new key value. > */ > swap(curr->vruntime, se->vruntime); > + resched_task(rq->curr); > } > > enqueue_task_fair(rq, p, 0); > - resched_task(rq->curr); > } > > /* > > Regards, > Bharata. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/