From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750897AbXD1U0p (ORCPT ); Sat, 28 Apr 2007 16:26:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751060AbXD1U0p (ORCPT ); Sat, 28 Apr 2007 16:26:45 -0400 Received: from an-out-0708.google.com ([209.85.132.250]:46166 "EHLO an-out-0708.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750897AbXD1U0o (ORCPT ); Sat, 28 Apr 2007 16:26:44 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=DlfKWiUdRmaOFVhifGBZ7WtXjX5+66gkOBa7oUYiZ9poM+T9KqOncBbEsSQc5Agrj8rKggNHu78/hlGJNgBKajZ0i6KBYv6Y9JqEhjS3+3CZFeAd85knp4ZfLC6CT83eJBmaP7RtAG081lYivCAOBm/wp2y+2CU93Mek9ghxpuE= Message-ID: Date: Sat, 28 Apr 2007 21:26:42 +0100 From: "Bradley Chapman" To: linux-kernel@vger.kernel.org Subject: CONFIG_HIGHMEM4G and 1GB RAM MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org After installing a second 512MB SODIMM into my laptop, I noticed that my 2.6.18.3 kernel only detected and used 896MB of the resulting 1GB, and informed me that I needed to enable high memory in order to access the remaining 127MB. While doing so, I noticed that the help text stated that enabling high memory (in my case, CONFIG_HIGHMEM4G) should only be done if the system the kernel is running on has more than 1GB, but less than 4GB - it said that systems with 1GB should leave it off, which resulted in an eighth of the installed memory going missing. A bit more research found a three year old thread on this list where it was stated that enabling CONFIG_HIGHMEM4G sometimes slows the system down due to sometimes undesirable changes to the way the kernel sets up the memory map. Basically, all I want to know is whether or not enabling CONFIG_HIGHMEM4G for a laptop that has exactly 1GB of RAM will result in any performance degradation. TIA, Brad P.S: Direct replies please - I'm not subscribed to the list.