Messages in this thread | | | Date | Wed, 4 Aug 2004 08:06:25 +0200 | From | Jens Axboe <> | Subject | Re: HIGHMEM4G config for 1GB RAM on desktop? |
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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
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