From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030731AbWKORYz (ORCPT ); Wed, 15 Nov 2006 12:24:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030733AbWKORYz (ORCPT ); Wed, 15 Nov 2006 12:24:55 -0500 Received: from cantor.suse.de ([195.135.220.2]:61851 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1030731AbWKORYy (ORCPT ); Wed, 15 Nov 2006 12:24:54 -0500 From: Andi Kleen To: Ingo Molnar Subject: Re: [PATCH] i386-pda UP optimization Date: Wed, 15 Nov 2006 18:24:35 +0100 User-Agent: KMail/1.9.5 Cc: Eric Dumazet , akpm@osdl.org, Arjan van de Ven , Jeremy Fitzhardinge , linux-kernel@vger.kernel.org References: <1158046540.2992.5.camel@laptopd505.fenrus.org> <200611151232.31937.ak@suse.de> <20061115172003.GA20403@elte.hu> In-Reply-To: <20061115172003.GA20403@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200611151824.36198.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 15 November 2006 18:20, Ingo Molnar wrote: > > * Andi Kleen wrote: > > > On Wednesday 15 November 2006 12:27, Eric Dumazet wrote: > > > Seeing %gs prefixes used now by i386 port, I recalled seeing strange > > > oprofile results on Opteron machines. > > > > > > I really think %gs prefixes can be expensive in some (most ?) cases, > > > even if the Intel/AMD docs say they are free. > > > > They aren't free, just very cheap. > > Eric's test shows a 5% slowdown. That's far from cheap. I have my doubts about the accuracy of his test results. That is why I asked him to double check. -Andi