From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gregory Haskins Subject: [PATCH 1/5] sched: only try to push a task on wakeup if it is migratable Date: Mon, 25 Aug 2008 16:15:24 -0400 Message-ID: <20080825201523.23217.39632.stgit@dev.haskins.net> References: <20080825200852.23217.13842.stgit@dev.haskins.net> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: srostedt@redhat.com, peterz@infradead.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, npiggin@suse.de, gregory.haskins@gmail.com To: mingo@elte.hu Return-path: Received: from 75-130-108-43.dhcp.oxfr.ma.charter.com ([75.130.108.43]:36222 "EHLO dev.haskins.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753005AbYHYURl (ORCPT ); Mon, 25 Aug 2008 16:17:41 -0400 In-Reply-To: <20080825200852.23217.13842.stgit@dev.haskins.net> Sender: linux-rt-users-owner@vger.kernel.org List-ID: There is no sense in wasting time trying to push a task away that cannot move anywhere else. We gain no benefit from trying to push other tasks at this point, so if the task being woken up is non migratable, just skip the whole operation. This reduces overhead in the wakeup path for certain tasks. Signed-off-by: Gregory Haskins --- kernel/sched_rt.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 6163e4c..196c024 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1229,14 +1229,16 @@ static void post_schedule_rt(struct rq *rq) } /* - * If we are not running and we are not going to reschedule soon, we should - * try to push tasks away now + * If we are not running, we are not going to reschedule soon, + * and we have tasks that could be pushed, we should try to push tasks + * away now */ static void task_wake_up_rt(struct rq *rq, struct task_struct *p) { if (!task_running(rq, p) && !test_tsk_need_resched(rq->curr) && - rq->rt.overloaded) + rq->rt.overloaded && + p->rt.nr_cpus_allowed > 1) push_rt_tasks(rq); }