From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265195AbUHDNIm (ORCPT ); Wed, 4 Aug 2004 09:08:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265207AbUHDNIm (ORCPT ); Wed, 4 Aug 2004 09:08:42 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:60639 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S265195AbUHDNIi (ORCPT ); Wed, 4 Aug 2004 09:08:38 -0400 Date: Wed, 4 Aug 2004 15:07:07 +0200 From: Jens Axboe To: Eric Bambach Cc: Con Kolivas , "Barry K. Nathan" , Steve Snyder , Linux Kernel Mailing List , Andrew Morton Subject: Re: HIGHMEM4G config for 1GB RAM on desktop? Message-ID: <20040804130707.GN10340@suse.de> References: <200408021602.34320.swsnyder@insightbb.com> <410FA145.70701@kolivas.org> <20040804060625.GE10340@suse.de> <200408040614.30820.eric@cisu.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200408040614.30820.eric@cisu.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 04 2004, Eric Bambach wrote: > On Wednesday 04 August 2004 01:06 am, Jens Axboe wrote: > > 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. > > As a desktop user with 1024MB ram I agree that HIMEM has a silly threshold and > should not need to be enabled in this case. Its becoming common, especially > with dual channel memory systems to use 2x512MB sticks. On a hunch I bet > 2x512 is more common that 1x512 and 1x256 so why not merge this up? Who would > we submit this patch to? One way would be to ask Andrew what he thinks? -- Jens Axboe