Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756754AbXKFBUV (ORCPT ); Mon, 5 Nov 2007 20:20:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755582AbXKFBUI (ORCPT ); Mon, 5 Nov 2007 20:20:08 -0500 Received: from terminus.zytor.com ([198.137.202.10]:51284 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755536AbXKFBUH (ORCPT ); Mon, 5 Nov 2007 20:20:07 -0500 Message-ID: <472FC130.40605@zytor.com> Date: Mon, 05 Nov 2007 17:19:44 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.5 (X11/20070727) MIME-Version: 1.0 To: Andi Kleen CC: Ray Lee , =?ISO-8859-1?Q?Bo_Brant=E9n?= , Andrew Morton , Jesse Barnes , linux-kernel@vger.kernel.org Subject: Re: x86_64 ten times slower than i386 References: <20071103162640.GS17536@waste.org> <2c0942db0711050832t5207ea8bib1f75e59e071ade2@mail.gmail.com> <20071106002647.GA27182@one.firstfloor.org> In-Reply-To: <20071106002647.GA27182@one.firstfloor.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1060 Lines: 24 Andi Kleen wrote: >> Jesse Barnes (cc:d) wrote a patch to address this, I think (x86: trim >> memory not covered by WB MTRRs), but as far as I can tell it hasn't >> been merged yet. System is Intel, 4gb of RAM. > > It wasn't merged because it broke booting on some systems. > Besides the memory would be still lost -- all it did was to automate > the "mem=XXXX" line. There really are only two ways to deal with this -- drop the memory (which should be automated, and a warning printed) or adjust the MTRRs. The problem is that at some point we run out of MTRRs, partially because they're masks instead of base/limit. Even use of PAT doesn't trivially resolve this issue with less than doing MTRR emulation via PAT (setting the default MTRR to WB); however, that is bound to cause trouble with SMM. -hpa - 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/