From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753229Ab3A2JaR (ORCPT ); Tue, 29 Jan 2013 04:30:17 -0500 Received: from forward4.mail.yandex.net ([77.88.46.9]:33294 "EHLO forward4.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751305Ab3A2JaM (ORCPT ); Tue, 29 Jan 2013 04:30:12 -0500 X-Greylist: delayed 991 seconds by postgrey-1.27 at vger.kernel.org; Tue, 29 Jan 2013 04:30:12 EST From: Kirill Tkhai To: Libo Chen Cc: linux-kernel@vger.kernel.org, Steven Rostedt , Ingo Molnar , Peter Zijlstra , linux-rt-users , lizefan@huawei.com, jovi.zhangwei@huawei.com Subject: Re:[PATCH]sched/rt: Do not try to push tasks if pinned task switches to RT MIME-Version: 1.0 Message-Id: <446051359450817@web10d.yandex.ru> X-Mailer: Yamail [ http://yandex.ru ] 5.0 Date: Tue, 29 Jan 2013 13:13:37 +0400 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=utf-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Libo Chen > > On 2013-1-29 4:23, Kirill Tkhai wrote: > >> Just switched pinned task is not able to be pushed. If the rq had had >> several RT tasks before they have already been considered as candidates >> to be pushed (or pulled). >> >> Signed-off-by: Kirill V Tkhai >> CC: Steven Rostedt >> CC: Ingo Molnar >> CC: Peter Zijlstra >> CC: linux-rt-users >> --- >> kernel/sched/rt.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c >> index 4e8f0f4..5f7d92b 100644 >> --- a/kernel/sched/rt.c >> +++ b/kernel/sched/rt.c >> @@ -1925,9 +1925,9 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) >> */ >> if (p->on_rq && rq->curr != p) { >> #ifdef CONFIG_SMP >> - if (rq->rt.overloaded && push_rt_task(rq) && >> + if (rq->rt.overloaded && p->nr_cpus_allowed > 1 && >> /* Don't resched if we changed runqueues */ >> - rq != task_rq(p)) >> + push_rt_task(rq) && rq != task_rq(p)) > > I think you worry about it was excess to call push_rt_task, since the task of p->nr_cpus_allowed=1 can`t be pushed. is that right? Sure. > > The task of p->nr_cpus_allowed =1 would`t be added to pushable_tasks list （see the enqueue_task_rt()）and this push_rt_task() need to push other tasks when rt.overloaded. If rq has already had 2 or more pushable tasks and we try to add a pinned task then call of push_rt_task will just waste a time. > > So I don`t agree this patch. > >> check_resched = 0; >> #endif /* CONFIG_SMP */ >> if (check_resched && p->prio < rq->curr->prio) >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html --