Re: HIGHMEM4G config for 1GB RAM on desktop?

[Con Kolivas]

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

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