From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760678AbXGEMQW (ORCPT ); Thu, 5 Jul 2007 08:16:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754331AbXGEMQN (ORCPT ); Thu, 5 Jul 2007 08:16:13 -0400 Received: from lucidpixels.com ([75.144.35.66]:56766 "EHLO lucidpixels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752778AbXGEMQM (ORCPT ); Thu, 5 Jul 2007 08:16:12 -0400 Date: Thu, 5 Jul 2007 08:16:11 -0400 (EDT) From: Justin Piszcz X-X-Sender: jpiszcz@p34.internal.lan To: Pavel Machek cc: Jesse Barnes , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Andi Kleen , "Eric W. Biederman" , Yinghai Lu Subject: Re: [PATCH] trim memory not covered by WB MTRRs In-Reply-To: <20070705121203.GB5167@ucw.cz> Message-ID: References: <200706251434.43863.jesse.barnes@intel.com> <20070705121203.GB5167@ucw.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 5 Jul 2007, Pavel Machek wrote: > Hi! > >> On some machines, buggy BIOSes don't properly setup WB MTRRs to >> cover all available RAM, meaning the last few megs (or even gigs) >> of memory will be marked uncached. Since Linux tends to allocate >> from high memory addresses first, this causes the machine to be >> unusably slow as soon as the kernel starts really using memory >> (i.e. right around init time). >> >> This patch works around the problem by scanning the MTRRs at >> boot and figuring out whether the current end_pfn value (setup >> by early e820 code) goes beyond the highest WB MTRR range, and >> if so, trimming it to match. A fairly obnoxious KERN_WARNING >> is printed too, letting the user know that not all of their >> memory is available due to a likely BIOS bug. >> >> Something similar could be done on i386 if needed, but the boot >> ordering would be slightly different, since the MTRR code on i386 >> depends on the boot_cpu_data structure being setup. >> >> This patch fixes a bug in the last patch that caused the code to >> run on non-Intel machines (AMD machines apparently don't need it >> and it's untested on other non-Intel machines, so best keep it >> off). >> >> akpm -- this one should replace all the mtrr patches currently >> in your tree. >> >> Yinghai, maybe you can test this on one of your AMD machines to >> make sure I got the CPU code right? > >> + if ((highest_addr >> PAGE_SHIFT) != end_pfn) { >> + printk(KERN_WARNING "***************\n"); >> + printk(KERN_WARNING "**** WARNING: likely BIOS bug\n"); >> + printk(KERN_WARNING "**** MTRRs don't cover all of " >> + "memory, trimmed %ld pages\n", end_pfn - >> + (highest_addr >> PAGE_SHIFT)); >> + printk(KERN_WARNING "***************\n"); >> + end_pfn = highest_addr >> PAGE_SHIFT; > > I'd say using that many stars for KERN_WARNING printk is sign of > mental illness or something... > Pavel > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html > Will this patch make it into 2.6.23? Been patching manually for a while with each -rc for 2.6.22.. Justin.