From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753956Ab2ITSug (ORCPT ); Thu, 20 Sep 2012 14:50:36 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:41327 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755152Ab2ITSub (ORCPT ); Thu, 20 Sep 2012 14:50:31 -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 23/23] rcu: Shrink RCU based on number of CPUs Date: Thu, 20 Sep 2012 11:48:19 -0700 Message-Id: <1348166900-18716-23-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-Content-Scanned: Fidelis XPS MAILER x-cbid: 12092018-4242-0000-0000-000002F75025 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Currently, rcu_init_geometry() only reshapes RCU's combining trees if the leaf fanout is changed at boot time. This means that by default, kernels compiled with (say) NR_CPUS=4096 will keep oversized data structures, even when running on systems with (say) four CPUs. This commit therefore checks to see if the maximum number of CPUs on the actual running system (nr_cpu_ids) differs from NR_CPUS, and if so reshapes the combining trees accordingly. Reported-by: Mike Galbraith Signed-off-by: Paul E. McKenney --- kernel/rcutree.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 5068e51..52b24c0 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -2819,7 +2819,8 @@ static void __init rcu_init_geometry(void) int rcu_capacity[MAX_RCU_LVLS + 1]; /* If the compile-time values are accurate, just leave. */ - if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF) + if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF && + nr_cpu_ids == NR_CPUS) return; /* -- 1.7.8