Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751594AbWIRNnB (ORCPT ); Mon, 18 Sep 2006 09:43:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751595AbWIRNnB (ORCPT ); Mon, 18 Sep 2006 09:43:01 -0400 Received: from embla.aitel.hist.no ([158.38.50.22]:6825 "HELO embla.aitel.hist.no") by vger.kernel.org with SMTP id S1751570AbWIRNnA (ORCPT ); Mon, 18 Sep 2006 09:43:00 -0400 Message-ID: <450EA198.5060302@aitel.hist.no> Date: Mon, 18 Sep 2006 15:39:36 +0200 From: Helge Hafting User-Agent: Thunderbird 1.5.0.5 (X11/20060812) MIME-Version: 1.0 To: yogeshwar sonawane CC: linux-kernel Subject: Re: How much kernel memory is in 64-bit OS ? References: In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1604 Lines: 45 yogeshwar sonawane wrote: > On 9/16/06, yogeshwar sonawane wrote: >> Hi all, >> >> We all know that in 32-bit OS, total 4GB memory space is divided in >> 3(user) + 1(kernel) space. >> >> Similarly, what is the division/scenario in case of 64-bit OS ? >> >> Any reference/explanation will be helpful. >> >> thanks in advance. >> >> >> Yogeshwar >> > > On similar lines, some time back, i read that, to accomodate large > physical memory , > the 3G/1G layout is modified to have 4G/4G partition. But if somebody > can focus the light on following things, it will be helpful. > 1) what was the requirement of 4G/4G layout ? It offers more memory than 3G/1G. This is an improvement, so of course it is the chosen way. It was not required - you sure can use a 3G/1G split on a 64-bit processor - but why introduce an artifical limitation? The requirement for using a 4G/4G split is to have a processor that support 64-bit adressing as well as 32-bit backward compatibility. > 2) how it is managed ? The kernel runs in 64-bit mode, offering the 4G/4G stuff for 32-bit processes. > 3) how HIGH_MEMORY concept is related here. high memory is a quirky way of supporting more than 4G on a 32-bit processor. A 64-bit processor support much more than 4G, so no need for tricks that work around the limitations of 32-bit processors. Helge Hafting - 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/