Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932079AbVKWQwg (ORCPT ); Wed, 23 Nov 2005 11:52:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932078AbVKWQwg (ORCPT ); Wed, 23 Nov 2005 11:52:36 -0500 Received: from terminus.zytor.com ([192.83.249.54]:6032 "EHLO terminus.zytor.com") by vger.kernel.org with ESMTP id S932079AbVKWQwf (ORCPT ); Wed, 23 Nov 2005 11:52:35 -0500 Message-ID: <43849E1C.3030102@zytor.com> Date: Wed, 23 Nov 2005 08:51:40 -0800 From: "H. Peter Anvin" User-Agent: Mozilla Thunderbird 1.0.7-1.1.fc4 (X11/20050929) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Gerd Knorr CC: Alan Cox , Andi Kleen , Linus Torvalds , Dave Jones , Zachary Amsden , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar Subject: Re: [patch] SMP alternatives References: <200511100032.jAA0WgUq027712@zach-dev.vmware.com> <20051111103605.GC27805@elf.ucw.cz> <4374F2D5.7010106@vmware.com> <4374FB89.6000304@vmware.com> <20051113074241.GA29796@redhat.com> <4378A7F3.9070704@suse.de> <4379ECC1.20005@suse.de> <437A0649.7010702@suse.de> <437B5A83.8090808@suse.de> <438359D7.7090308@suse.de> <1132764133.7268.51.camel@localhost.localdomain> <43849C23.3040001@suse.de> In-Reply-To: <43849C23.3040001@suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 861 Lines: 20 Gerd Knorr wrote: > > Patching in/out SMP-locking with more than one active CPU would be a > pretty silly idea in the first place ;) > No, doing this crap with CPU hotplug is a silly idea. Patching on a real UP system, and then throwing out the tables, makes sense. Keeping two sets of tables for a minimal performance improvement in a very rare configuration (CPU hotplug is the exception, not the rule) is just plain stupid. You probably lose as much performance from the memory hogged up in the tables as you gain from it, and on every system where you have the tables at all you take the hit. -hpa - 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/