From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756570Ab3A0K6V (ORCPT ); Sun, 27 Jan 2013 05:58:21 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:57781 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754754Ab3A0K6S (ORCPT ); Sun, 27 Jan 2013 05:58:18 -0500 X-Originating-IP: 217.70.178.147 X-Originating-IP: 150.203.246.47 Date: Sun, 27 Jan 2013 21:58:06 +1100 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, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu Subject: Re: [PATCH tip/core/rcu 2/2] rcu: Allow TREE_PREEMPT_RCU on UP systems Message-ID: <20130127105805.GE3119@leaf> References: <20130127002328.GA4847@linux.vnet.ibm.com> <1359246227-5770-1-git-send-email-paulmck@linux.vnet.ibm.com> <1359246227-5770-2-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: <1359246227-5770-2-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 Sat, Jan 26, 2013 at 04:23:47PM -0800, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > The TINY_PREEMPT_RCU is complex, does not provide that much memory > savings, and therefore TREE_PREEMPT_RCU should be used instead. The > systems where the difference between TINY_PREEMPT_RCU and TREE_PREEMPT_RCU > are quite small compared to the memory footprint of CONFIG_PREEMPT. > > This commit therefore takes a first step towards eliminating > TINY_PREEMPT_RCU by allowing TREE_PREEMPT_RCU to be configured on !SMP > systems. > > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > --- > init/Kconfig | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/init/Kconfig b/init/Kconfig > index a5e90e1..fb19b46 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -453,7 +453,7 @@ config TREE_RCU > > config TREE_PREEMPT_RCU > bool "Preemptible tree-based hierarchical RCU" > - depends on PREEMPT && SMP > + depends on PREEMPT > help > This option selects the RCU implementation that is > designed for very large SMP systems with hundreds or > @@ -461,6 +461,8 @@ config TREE_PREEMPT_RCU > is also required. It also scales down nicely to > smaller systems. > > + Select this option if you are unsure. > + > config TINY_RCU > bool "UP-only small-memory-footprint RCU" > depends on !PREEMPT && !SMP > -- > 1.7.8 >