From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755387AbYAYCQl (ORCPT ); Thu, 24 Jan 2008 21:16:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752440AbYAYCQe (ORCPT ); Thu, 24 Jan 2008 21:16:34 -0500 Received: from hawking.rebel.net.au ([203.20.69.83]:32931 "EHLO hawking.rebel.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752422AbYAYCQe (ORCPT ); Thu, 24 Jan 2008 21:16:34 -0500 Message-ID: <4799467E.6020407@davidnewall.com> Date: Fri, 25 Jan 2008 12:46:30 +1030 From: David Newall User-Agent: Thunderbird 2.0.0.6 (X11/20071022) MIME-Version: 1.0 To: Andi Kleen CC: Adrian Bunk , Ingo Molnar , akpm@osdl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH for mm] Remove iBCS support References: <20080120055544.GB19861@one.firstfloor.org> <4792E8E2.1090307@davidnewall.com> <20080120072922.GA21047@one.firstfloor.org> <4793F775.6090403@davidnewall.com> <20080122111205.GA25090@elte.hu> <4796081A.7060505@davidnewall.com> <20080122160114.GB23277@does.not.exist> <4798C511.8070305@davidnewall.com> <20080124172414.GD4476@does.not.exist> <4798D10C.6090109@davidnewall.com> <20080124203724.GA14852@one.firstfloor.org> In-Reply-To: <20080124203724.GA14852@one.firstfloor.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen wrote: >> The performance benefit is trivial, >> > > That's actually not true when you're talking about potential cache misses. > Cache misses are very expensive. > They are when in a tight loop, but are trivial in this case. I'll go further and say that unless the system is constantly execing, there will always be a cache miss, and that removing this code will not improve that at all.