From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751417AbWIMKIY (ORCPT ); Wed, 13 Sep 2006 06:08:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751427AbWIMKIY (ORCPT ); Wed, 13 Sep 2006 06:08:24 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:37564 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1751417AbWIMKIX (ORCPT ); Wed, 13 Sep 2006 06:08:23 -0400 Date: Wed, 13 Sep 2006 11:59:42 +0200 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: Arjan van de Ven , akpm@osdl.org, ak@suse.de, linux-kernel@vger.kernel.org, Michael.Fetterman@cl.cam.ac.uk, Ian Campbell Subject: Re: i386 PDA patches use of %gs Message-ID: <20060913095942.GA10075@elte.hu> References: <1158046540.2992.5.camel@laptopd505.fenrus.org> <45075829.701@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45075829.701@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 * Jeremy Fitzhardinge wrote: > [...] The basic inner loop is: > > push %segreg > mov %selectorreg, %segreg > add $1,%segreg:offset # use the segment register > pop %segreg well, the most important thing i believe you didnt test: the effect of mixing two descriptors on the _same_ selector: one %gs selector value loaded and used by glibc, and another %gs selector value loaded and used by the kernel, intermixed. It's the mixing that causes the descriptor cache reload. (unless i missed some detail about your testcase) Ingo