Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933282AbaJUQgK (ORCPT ); Tue, 21 Oct 2014 12:36:10 -0400 Received: from relay.parallels.com ([195.214.232.42]:43410 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932452AbaJUQgG (ORCPT ); Tue, 21 Oct 2014 12:36:06 -0400 Message-ID: <1413909356.19914.128.camel@tkhai> Subject: [RFC] sched/dl: Fix preemption checks From: Kirill Tkhai To: Juri Lelli , CC: Peter Zijlstra , Ingo Molnar , Kirill Tkhai Date: Tue, 21 Oct 2014 20:35:56 +0400 Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 1)switched_to_dl() check is wrong. We reschedule only if rq->curr is deadline task, and we do not reschedule if it's a lower priority task. But we must always preempt a task of other classes. 2)dl_task_timer(): Policy does not change in case of priority inheritance. rt_mutex_setprio() changes prio, while policy remains old. So we lose some balancing logic in dl_task_timer() and switched_to_dl() when we check policy instead of priority. Boosted task may be rq->curr. (I didn't change switched_from_dl() because no check is necessary there at all). I've looked at this place(switched_to_dl) several times and even fixed this function, but found just now... I suppose some performance tests may work better after this. Completely untested, just RFC. Juri how about this? Signed-off-by: Kirill Tkhai --- kernel/sched/deadline.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 256e577..937a875 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -532,7 +532,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) dl_se->dl_yielded = 0; if (task_on_rq_queued(p)) { enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); - if (task_has_dl_policy(rq->curr)) + if (dl_task(rq->curr)) check_preempt_curr_dl(rq, p, 0); else resched_curr(rq); @@ -1607,8 +1607,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) /* Only reschedule if pushing failed */ check_resched = 0; #endif /* CONFIG_SMP */ - if (check_resched && task_has_dl_policy(rq->curr)) - check_preempt_curr_dl(rq, p, 0); + if (check_resched) { + if (dl_task(rq->curr)) + check_preempt_curr_dl(rq, p, 0); + else + resched_curr(rq); + } } } -- 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/