From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753545Ab0AZVbA (ORCPT ); Tue, 26 Jan 2010 16:31:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752823Ab0AZVa7 (ORCPT ); Tue, 26 Jan 2010 16:30:59 -0500 Received: from one.firstfloor.org ([213.235.205.2]:51884 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752644Ab0AZVa7 (ORCPT ); Tue, 26 Jan 2010 16:30:59 -0500 To: paulmck@linux.vnet.ibm.com 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, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com Subject: Re: [PATCH RFC tip/core/rcu] accelerate grace period if last non-dynticked CPU From: Andi Kleen References: <20100125034816.GA14043@linux.vnet.ibm.com> Date: Tue, 26 Jan 2010 22:30:57 +0100 In-Reply-To: <20100125034816.GA14043@linux.vnet.ibm.com> (Paul E. McKenney's message of "Sun, 24 Jan 2010 19:48:16 -0800") Message-ID: <873a1sft9q.fsf@basil.nowhere.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/22.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Paul E. McKenney" writes: Kind of offtopic to the original patch, but I couldn't resist... > +config RCU_FAST_NO_HZ > + bool "Accelerate last non-dyntick-idle CPU's grace periods" > + depends on TREE_RCU && NO_HZ && SMP Having such a thing as a config option doesn't really make any sense to me. Who would want to recompile their kernel to enable/disable this? If anything it should be runtime, or better just unconditionally on. In general RCU could probably reduce its number of "weird" Kconfig options. While I think I have a better understanding of RCU than a lot of normal users I often have no clue what to set there when building a kernel. -Andi -- ak@linux.intel.com -- Speaking for myself only.