Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750974AbWIKHiN (ORCPT ); Mon, 11 Sep 2006 03:38:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751028AbWIKHiM (ORCPT ); Mon, 11 Sep 2006 03:38:12 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:3233 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1750969AbWIKHiM (ORCPT ); Mon, 11 Sep 2006 03:38:12 -0400 Date: Mon, 11 Sep 2006 09:29:59 +0200 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: Andrew Morton , Andi Kleen , Laurent Riffard , Arjan van de Ven , Kernel development list , Jeremy Fitzhardinge Subject: Re: 2.6.18-rc6-mm1: GPF loop on early boot Message-ID: <20060911072959.GA2322@elte.hu> References: <20060908011317.6cb0495a.akpm@osdl.org> <200609101032.17429.ak@suse.de> <20060910115722.GA15356@elte.hu> <200609101334.34867.ak@suse.de> <20060910132614.GA29423@elte.hu> <20060910093307.a011b16f.akpm@osdl.org> <450499D3.5010903@goop.org> <20060911051028.GA10084@elte.hu> <450510E0.8080906@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <450510E0.8080906@goop.org> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.9 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.9 required=5.9 tests=ALL_TRUSTED,AWL,BAYES_50 autolearn=no SpamAssassin version=3.0.3 -3.3 ALL_TRUSTED Did not pass through any untrusted hosts 0.5 BAYES_50 BODY: Bayesian spam probability is 40 to 60% [score: 0.5000] -0.1 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 929 Lines: 22 * Jeremy Fitzhardinge wrote: > Ingo Molnar wrote: > >another thing about i386-pda: why did you pick the %gs selector to store > >the PDA in? %fs would be a better choice because %gs is used by glibc so > >the saving/restoring of %fs would likely be near zero-cycles cost. > >(instead of the current 9 cycles for saving/restoring %gs) > > Why would saving/restoring %fs be quicker? [...] because userspace does not use it normally, while with %gs we'd switch between glibc's descriptor [which must be shadowed by the CPU] and the kernel's descriptor [which must be shadowed by the CPU too] - hence causing a constant reloading of the shadow register. 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/