From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754592Ab2BBCEU (ORCPT ); Wed, 1 Feb 2012 21:04:20 -0500 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:55736 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754560Ab2BBCET (ORCPT ); Wed, 1 Feb 2012 21:04:19 -0500 X-Originating-IP: 217.70.178.133 X-Originating-IP: 50.43.15.19 Date: Wed, 1 Feb 2012 18:03:56 -0800 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, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, "Paul E. McKenney" Subject: Re: [PATCH RFC tip/core/rcu 14/41] rcu: Limit lazy-callback duration Message-ID: <20120202020356.GL29058@leaf> References: <20120201194131.GA10028@linux.vnet.ibm.com> <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> <1328125319-5205-14-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: <1328125319-5205-14-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 Wed, Feb 01, 2012 at 11:41:32AM -0800, Paul E. McKenney wrote: > Currently, a given CPU is permitted to remain in dyntick-idle mode > indefinitely if it has only lazy RCU callbacks queued. This is vulnerable > to corner cases in NUMA systems, so limit the time to six seconds by > default. (Currently controlled by a cpp macro.) I wonder: should this scale with the number of callbacks, or do we not want to make estimates about memory usage based on that? Interestingly, with kfree_rcu, we actually know at callback queuing time *exactly* how much memory we'll get back by calling the callback, and we could sum up those numbers. - Josh Triplett