Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759960AbZDBD1o (ORCPT ); Wed, 1 Apr 2009 23:27:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753194AbZDBD1d (ORCPT ); Wed, 1 Apr 2009 23:27:33 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:59179 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752152AbZDBD1c (ORCPT ); Wed, 1 Apr 2009 23:27:32 -0400 Date: Thu, 2 Apr 2009 05:25:06 +0200 From: Ingo Molnar To: Christoph Lameter Cc: Matthew Wilcox , Linus Torvalds , Tejun Heo , Martin Schwidefsky , rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com, Paul Mundt , rmk@arm.linux.org.uk, starvik@axis.com, ralf@linux-mips.org, davem@davemloft.net, cooloney@kernel.org, kyle@mcmartin.ca, grundler@parisc-linux.org, takata@linux-m32r.org, benh@kernel.crashing.org, rth@twiddle.net, ink@jurassic.park.msu.ru, heiko.carstens@de.ibm.com, Nick Piggin , Peter Zijlstra Subject: Re: [PATCH UPDATED] percpu: use dynamic percpu allocator as the default percpu allocator Message-ID: <20090402032506.GC21545@elte.hu> References: <49D2B209.9060000@kernel.org> <20090401154913.GA31435@elte.hu> <20090401190113.GA734@elte.hu> <20090401223241.GA28168@elte.hu> <20090401225754.GN8014@parisc-linux.org> <20090402021024.GA26446@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1103 Lines: 29 * Christoph Lameter wrote: > > A sub-sub argument was that perhaps we should not split .data > > and .bss variables into separate sections - it doubles the > > chance of false cacheline sharing and spreads the cacheline > > footprint. > > False cacheline sharing is something normal that comes with the > cpu caching schemes. As long as there is no significant impact on > performance we are fine with it. Extensive measures to avoid false > cacheline sharing on unimportant variables increases the cache > footprint of code. You didnt really answer to my suggestion(s) though. You only stated that: "problem XYZ is something normal that comes with the cpu caching schemes. As long as there is no significant impact on performance weare fine with it." Which i'd proffer is true for any given value of XYZ ;-) Ingo -- 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/