Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261393AbTIKQmN (ORCPT ); Thu, 11 Sep 2003 12:42:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261422AbTIKQmM (ORCPT ); Thu, 11 Sep 2003 12:42:12 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:26038 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S261393AbTIKQmK (ORCPT ); Thu, 11 Sep 2003 12:42:10 -0400 Date: Thu, 11 Sep 2003 17:42:10 +0100 From: Matthew Wilcox To: Andi Kleen Cc: Matthew Wilcox , linux-kernel@vger.kernel.org Subject: Re: Memory mapped IO vs Port IO Message-ID: <20030911164210.GM21596@parcelfarce.linux.theplanet.co.uk> References: <20030911160116.GI21596@parcelfarce.linux.theplanet.co.uk.suse.lists.linux.kernel> <20030911162504.GL21596@parcelfarce.linux.theplanet.co.uk> <20030911183136.01dfeb53.ak@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030911183136.01dfeb53.ak@suse.de> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 886 Lines: 20 On Thu, Sep 11, 2003 at 06:31:36PM +0200, Andi Kleen wrote: > On Thu, 11 Sep 2003 17:25:04 +0100 > Matthew Wilcox wrote: > > That's not true for MMIO writes which are posted. They should take > > no longer than a memory write. For MMIO reads and PIO reads & writes, > > you are, of course, correct. > > Even a memory write is tens to hundres of cycles. So are mispredicted branches. -- "It's not Hollywood. War is real, war is primarily not about defeat or victory, it is about death. I've seen thousands and thousands of dead bodies. Do you think I want to have an academic debate on this subject?" -- Robert Fisk - 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/