From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751362Ab2IBFXM (ORCPT ); Sun, 2 Sep 2012 01:23:12 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:55205 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750870Ab2IBFXK (ORCPT ); Sun, 2 Sep 2012 01:23:10 -0400 X-Originating-IP: 217.70.178.151 X-Originating-IP: 50.43.46.74 Date: Sat, 1 Sep 2012 22:23:02 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org Subject: Re: [PATCH tip/core/rcu 10/23] rcu: Allow RCU quiescent-state forcing to be preempted Message-ID: <20120902052301.GB7767@leaf> References: <20120830181811.GA29154@linux.vnet.ibm.com> <1346350718-30937-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346350718-30937-10-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: <1346350718-30937-10-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 30, 2012 at 11:18:25AM -0700, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > RCU quiescent-state forcing is currently carried out without preemption > points, which can result in excessive latency spikes on large systems > (many hundreds or thousands of CPUs). This patch therefore inserts > a voluntary preemption point into force_qs_rnp(), which should greatly > reduce the magnitude of these spikes. > > Reported-by: Mike Galbraith > Reported-by: Dimitri Sivanich > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > kernel/rcutree.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 79c2c28..cce73ff 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1784,6 +1784,7 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) > struct rcu_node *rnp; > > rcu_for_each_leaf_node(rsp, rnp) { > + cond_resched(); > mask = 0; > raw_spin_lock_irqsave(&rnp->lock, flags); > if (!rcu_gp_in_progress(rsp)) { > -- > 1.7.8 >