From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752609AbaINJNs (ORCPT ); Sun, 14 Sep 2014 05:13:48 -0400 Received: from casper.infradead.org ([85.118.1.10]:41845 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752577AbaINJNr (ORCPT ); Sun, 14 Sep 2014 05:13:47 -0400 Date: Sun, 14 Sep 2014 11:13:38 +0200 From: Peter Zijlstra To: Kirill Tkhai Cc: linux-kernel@vger.kernel.org, Ingo Molnar , tkhai@yandex.ru Subject: Re: [PATCH] sched: Do not stop cpu in set_cpus_allowed_ptr() if task is not running Message-ID: <20140914091338.GN346@worktop.programming.kicks-ass.net> References: <1410519814.3569.7.camel@tkhai> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1410519814.3569.7.camel@tkhai> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 12, 2014 at 03:03:34PM +0400, Kirill Tkhai wrote: > > If a task is queued but not running on it rq, we can simply migrate > it without migration thread and switching of context. > > Signed-off-by: Kirill Tkhai > --- > kernel/sched/core.c | 47 ++++++++++++++++++++++++++++++++--------------- > 1 file changed, 32 insertions(+), 15 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index d4399b4..dbbba26 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -4594,6 +4594,33 @@ void init_idle(struct task_struct *idle, int cpu) > } > > #ifdef CONFIG_SMP > +/* > + * move_queued_task - move a queued task to new rq. > + * > + * Returns (locked) new rq. Old rq's lock is released. > + */ > +static struct rq *move_queued_task(struct task_struct *p, int new_cpu) > +{ > + struct rq *rq = task_rq(p); > + > + lockdep_assert_held(&rq->lock); > + > + dequeue_task(rq, p, 0); > + p->on_rq = TASK_ON_RQ_MIGRATING; > + set_task_cpu(p, new_cpu); > + raw_spin_unlock(&rq->lock); > + > + rq = cpu_rq(new_cpu); > + > + raw_spin_lock(&rq->lock); > + BUG_ON(task_cpu(p) != new_cpu); > + p->on_rq = TASK_ON_RQ_QUEUED; > + enqueue_task(rq, p, 0); > + check_preempt_curr(rq, p, 0); > + > + return rq; > +} We have almost that exact code sequence in __migrate_task() could we share some?