Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751268AbVKNTx3 (ORCPT ); Mon, 14 Nov 2005 14:53:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751267AbVKNTx3 (ORCPT ); Mon, 14 Nov 2005 14:53:29 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:32432 "EHLO pentafluge.infradead.org") by vger.kernel.org with ESMTP id S1751268AbVKNTx3 (ORCPT ); Mon, 14 Nov 2005 14:53:29 -0500 Subject: Re: [PATCH 1/10] Cr4 is valid on some 486s From: Arjan van de Ven To: Zachary Amsden Cc: Linus Torvalds , Gerd Knorr , Dave Jones , Pavel Machek , Andrew Morton , Linux Kernel Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , Ingo Molnar In-Reply-To: <4378E97E.2060707@vmware.com> 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> <4378E97E.2060707@vmware.com> Content-Type: text/plain Date: Mon, 14 Nov 2005 20:52:51 +0100 Message-Id: <1131997971.2821.68.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit X-Spam-Score: 1.8 (+) X-Spam-Report: SpamAssassin version 3.0.4 on pentafluge.infradead.org summary: Content analysis details: (1.8 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.1 RCVD_IN_SORBS_DUL RBL: SORBS: sent directly from dynamic IP address [213.93.14.173 listed in dnsbl.sorbs.net] 1.7 RCVD_IN_NJABL_DUL RBL: NJABL: dialup sender did non-local SMTP [213.93.14.173 listed in combined.njabl.org] X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 986 Lines: 20 On Mon, 2005-11-14 at 11:46 -0800, Zachary Amsden wrote: > It seems that SMP vs. UP lock / spinlock overhead is relevant even for > future, multi-core CPUs in a virtualization context, as the notion of > hotplug here is based on scheduling constraints of the virtualization > engine, and the kernel can quite readily end up with only one VCPU. this assumes that you don't just always want to assume and use SMP primitives in a virtualized context. I sort of question that assumption; sure these things have overhead, especially "lock", but if the solution is more complexity and weird things to hide that half-percent or less of performance difference... then do remember that such complexity is not free either. Runtime tricks cost. - 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/