Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760114AbZANOta (ORCPT ); Wed, 14 Jan 2009 09:49:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753585AbZANOtW (ORCPT ); Wed, 14 Jan 2009 09:49:22 -0500 Received: from ti-out-0910.google.com ([209.85.142.190]:61268 "EHLO ti-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753441AbZANOtW (ORCPT ); Wed, 14 Jan 2009 09:49:22 -0500 Date: Wed, 14 Jan 2009 15:41:15 +0100 From: Frederik Deweerdt To: Andi Kleen Cc: Peter Zijlstra , Ingo Molnar , Ravikiran G Thirumalai , tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org Subject: Re: [patch] tlb flush_data: replace per_cpu with an array Message-ID: <20090114144115.GF10720@gambetta> References: <20090112213539.GA10720@gambetta> <20090112223421.GA20594@localdomain> <20090112230052.GB18771@elte.hu> <1231848016.442.112.camel@twins> <20090114090811.GQ23848@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090114090811.GQ23848@one.firstfloor.org> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1166 Lines: 31 On Wed, Jan 14, 2009 at 10:08:11AM +0100, Andi Kleen wrote: > > > > It also would save some memory > > > on most distros out there (Ubuntu x86_64 has NR_CPUS=64 by default). > > As pointed out several times this claim in the changelog is incorrect. > Please fix it. > > A correct description would be: > > - This patch wastes memory of one configured cache line for each CPU > on systems with less than 8 cores (e.g. 896 bytes on a 1 core system > with CONFIG_GENERIC_CPU/ cache line size 128) > It saves some memory on systems with more than 8 cores (one cache > line size for each core above 8) To be fair, it also depends on whenever HOTPLUG_CPU is on or not (if it is we allocate NR_CPUS percpu sections). In that case, which is Ubuntu's and Fedora's, we do save memory. This would make for a fairly long changelog, how about a link to this thread, and removing the NR_CPUS bit? Regards, Frederik > > -Andi > -- 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/