Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754411Ab2KMBeJ (ORCPT ); Mon, 12 Nov 2012 20:34:09 -0500 Received: from mail-vc0-f174.google.com ([209.85.220.174]:57735 "EHLO mail-vc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753851Ab2KMBeH (ORCPT ); Mon, 12 Nov 2012 20:34:07 -0500 MIME-Version: 1.0 In-Reply-To: <20121113011712.GA20884@jtriplet-mobl1> References: <20121113004906.GA10557@linux.vnet.ibm.com> <20121113011712.GA20884@jtriplet-mobl1> Date: Tue, 13 Nov 2012 02:34:06 +0100 Message-ID: Subject: Re: Does anyone use CONFIG_TINY_PREEMPT_RCU? From: Frederic Weisbecker To: Josh Triplett Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, 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, sbw@mit.edu, patches@linaro.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1345 Lines: 28 2012/11/13 Josh Triplett : > On Tue, Nov 13, 2012 at 02:12:27AM +0100, Frederic Weisbecker wrote: >> 2012/11/13 Paul E. McKenney : >> > Hello! >> > >> > I know of people using TINY_RCU, TREE_RCU, and TREE_PREEMPT_RCU, but I >> > have not heard of anyone using TINY_PREEMPT_RCU for whom TREE_PREEMPT_RCU >> > was not a viable option (in contrast, the people running Linux on >> > tiny-memmory systems typically use TINY_RCU). Of course, if no one >> > really needs it, the proper thing to do is to remove it. >> > >> > So, if you need TINY_PREEMPT_RCU, please let me know. Otherwise, I will >> > remove it, probably in the 3.9 timeframe. >> >> I don't use it personally but if you remove it, does that mean that >> RCU couldn't be preemptible on UP? > > No, it would mean that on UP you could choose between TINY_RCU and > TREE_PREEMPT_RCU, depending on whether you want tiny or preemptible. Ok. I thought the TREE version wasn't possible anymore on UP when I saw some patches that removed optimizations for nr_online_cpus=1. Hence the confusion. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/