From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758297AbZIFUHH (ORCPT ); Sun, 6 Sep 2009 16:07:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758268AbZIFUHG (ORCPT ); Sun, 6 Sep 2009 16:07:06 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:55842 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758241AbZIFUHF (ORCPT ); Sun, 6 Sep 2009 16:07:05 -0400 Date: Sun, 6 Sep 2009 22:07:01 +0200 From: Pavel Machek To: "Paul E. McKenney" Cc: Valdis.Kletnieks@vt.edu, Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: RCU Kconfig help text Message-ID: <20090906200700.GA12714@elf.ucw.cz> References: <12924.1252157230@turing-police.cc.vt.edu> <20090905200145.GB7181@linux.vnet.ibm.com> <20090906062441.GD1431@ucw.cz> <20090906063927.GG7181@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090906063927.GG7181@linux.vnet.ibm.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > > > This leaves somebody who has a laptop wondering which choice is best for > > > > a system with only one or two cores that has CONFIG_PREEMPT defined. One > > > > choice says it scales down nicely, the other explicitly has a 'depends on > > > > PREEMPT' attached to it... > > > > > > > > (Yes, I realize in practice, the RCU sections on a laptop are probably usually > > > > so short they don't matter in practice. I finally concluded TREE_PREEMPT was > > > > apparently a rename of CONFIG_PREEMPT_RCU and went with that since that was > > > > working for me before...) > > > > > > Good point -- I will add the "It also scales down nicely to smaller > > > systems" to TREE_PREEMPT_RCU. > > > > > > For -really- small systems, TINY_RCU will hopefully be there at some > > > point, but it can only handle single-CPU systems. > > > > If so, call it 'UP_RCU' or 'UNIPROCESSOR_RCU'? > > "UP_RCU". Cute!!! ;-) > > My hope is to drive the RCU selection directly from CONFIG_SMP and > CONFIG_PREEMPT, so that the choice of RCU would be implicit (aside from > things like tracing and fanout). > > Seem reasonable, or would you expect anyone to want to hand-select > the RCU implementation? Seems reasonable. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html