From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754354Ab2ITStM (ORCPT ); Thu, 20 Sep 2012 14:49:12 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:49476 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754278Ab2ITStF (ORCPT ); Thu, 20 Sep 2012 14:49:05 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, 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, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 11/23] rcu: Allow RCU quiescent-state forcing to be preempted Date: Thu, 20 Sep 2012 11:48:07 -0700 Message-Id: <1348166900-18716-11-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1348166900-18716-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120920184751.GA18657@linux.vnet.ibm.com> <1348166900-18716-1-git-send-email-paulmck@linux.vnet.ibm.com> x-cbid: 12092018-7182-0000-0000-000002AAD3B7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 dbf9cc3..b353d32 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1765,6 +1765,7 @@ 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