From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751551AbdAUUlX (ORCPT ); Sat, 21 Jan 2017 15:41:23 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:38588 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751345AbdAUUlQ (ORCPT ); Sat, 21 Jan 2017 15:41:16 -0500 X-Originating-IP: 50.39.169.170 Date: Sat, 21 Jan 2017 12:41:03 -0800 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH v2 tip/core/rcu 07/18] rcu: Add long-term CPU kicking Message-ID: <20170121204103.p2d7q4syf2t53kyt@x> References: <20170118025316.GB2042@linux.vnet.ibm.com> <1484708037-2523-7-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1484708037-2523-7-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: NeoMutt/20161126 (1.7.1) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 17, 2017 at 06:53:46PM -0800, Paul E. McKenney wrote: > Commit d2db185bfee8 ("rcu: Remove short-term CPU kicking") removed > frequent calls to resched_cpu(), which means that the only time > resched_cpu() is invoked is after an RCU CPU stall warning. Although > this is good from an avoid-IPIs perspective, we should try to break > things loose -before- splatting. This commit therefore starts invoking > resched_cpu() for each holdout at each force-quiescent-state interval > that is more than halfway through the stall-warning interval. > > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > --- > kernel/rcu/tree.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 83bf054e194e..0e61b62e3f4a 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1225,6 +1225,12 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, > rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) || > ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs)) > resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ > + /* > + * If more than halfway to RCU CPU stall-warning time, do > + * a resched_cpu() to try to loosen things up a bit. > + */ > + if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2) > + resched_cpu(rdp->cpu); > > return 0; > } > -- > 2.5.2 >