From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267291AbUHDGHc (ORCPT ); Wed, 4 Aug 2004 02:07:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267292AbUHDGHc (ORCPT ); Wed, 4 Aug 2004 02:07:32 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:27328 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S267291AbUHDGGw (ORCPT ); Wed, 4 Aug 2004 02:06:52 -0400 Date: Wed, 4 Aug 2004 08:06:25 +0200 From: Jens Axboe To: Con Kolivas Cc: "Barry K. Nathan" , Steve Snyder , Linux Kernel Mailing List Subject: Re: HIGHMEM4G config for 1GB RAM on desktop? Message-ID: <20040804060625.GE10340@suse.de> References: <200408021602.34320.swsnyder@insightbb.com> <20040802220521.GA2179@ip68-4-98-123.oc.oc.cox.net> <20040803133034.GM23504@suse.de> <410FA145.70701@kolivas.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <410FA145.70701@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 04 2004, Con Kolivas wrote: > Jens Axboe wrote: > >On Mon, Aug 02 2004, Barry K. Nathan wrote: > > > >>On Mon, Aug 02, 2004 at 04:02:34PM -0500, Steve Snyder wrote: > >> > >>>There seems to be a controversy about the use of the CONFIG_HIGHMEM4G > >>>kernel configuration. After reading many posts on the subject, I still > >>>don't know which setting is best for me. > > No idea what the performance hit is of highmem these days - it seems > insignificant compared to 2.4 so I've had it enabled for 1Gb ram. > > >There's also the option of moving the mapping only slightly, so that all > >of the 1G fits in low memory. That's the best option for 1G desktop > >machines, imho. Changing PAGE_OFFSET from 0xc0000000 to 0xb0000000 would > >probably be enough. > > > >Then you can have your cake and eat it too. > > Something like this attached patch? Seems to work nicely. Thanks! > > Cheers, > Con > Index: linux-2.6.8-rc2-mm2/arch/i386/kernel/vmlinux.lds.S > =================================================================== > --- linux-2.6.8-rc2-mm2.orig/arch/i386/kernel/vmlinux.lds.S 2004-05-23 12:54:46.000000000 +1000 > +++ linux-2.6.8-rc2-mm2/arch/i386/kernel/vmlinux.lds.S 2004-08-04 00:20:02.219462913 +1000 > @@ -11,7 +11,7 @@ > jiffies = jiffies_64; > SECTIONS > { > - . = 0xC0000000 + 0x100000; > + . = 0xB0000000 + 0x100000; > /* read-only */ > _text = .; /* Text and read-only data */ > .text : { > Index: linux-2.6.8-rc2-mm2/include/asm-i386/page.h > =================================================================== > --- linux-2.6.8-rc2-mm2.orig/include/asm-i386/page.h 2004-08-03 01:29:28.000000000 +1000 > +++ linux-2.6.8-rc2-mm2/include/asm-i386/page.h 2004-08-03 23:58:16.000000000 +1000 > @@ -123,9 +123,9 @@ > #endif /* __ASSEMBLY__ */ > > #ifdef __ASSEMBLY__ > -#define __PAGE_OFFSET (0xC0000000) > +#define __PAGE_OFFSET (0xB0000000) > #else > -#define __PAGE_OFFSET (0xC0000000UL) > +#define __PAGE_OFFSET (0xB0000000UL) > #endif Yup precisely. I agree that there probably isn't a whole lot of performance hit on a 1GB, it just seems silly that we need highmem on such a standard memory configuration these days. Especially when just moving the offset slightly removes that need. -- Jens Axboe