Re: 2G memory split

[Mark Lord <lkml@rtr.ca>]

Jens Axboe wrote:
> On Tue, Jan 10 2006, Mark Lord wrote:
>>So, the patch would now look like this:
> Looks good to me!

I'm just trying to save you some diff'ing, Jens!

Here it is again, with Linus's latest.

Andrew:  please drop this into -mm for now, per Linus:

Chief Penguin wrote:
 >Anyway, this should go into -mm, and I'd rather have it stay there for a
 >while. I've got tons of stuff for 2.6.16 already, I'd prefer to not see
 >this kind of thing too..

Signed-off-by:  mlord@pobox.com

diff -u --recursive --new-file --exclude='.*' linux-2.6.15/arch/i386/Kconfig linux/arch/i386/Kconfig
--- linux-2.6.15/arch/i386/Kconfig	2006-01-02 22:21:10.000000000 -0500
+++ linux/arch/i386/Kconfig	2006-01-10 12:02:40.000000000 -0500
@@ -448,6 +448,43 @@

  endchoice

+choice
+	depends on EXPERIMENTAL && !X86_PAE
+	prompt "Memory split"
+	default VMSPLIT_3G
+	help
+	  Select the desired split between kernel and user memory.
+
+	  If the address range available to the kernel is less than the
+	  physical memory installed, the remaining memory will be available
+	  as "high memory". Accessing high memory is a little more costly
+	  than low memory, as it needs to be mapped into the kernel first.
+	  Note that increasing the kernel address space limits the range
+	  available to user programs, making the address space there
+	  tighter.  Selecting anything other than the default 3G/1G split
+	  will also likely make your kernel incompatible with binary-only
+	  kernel modules.
+
+	  If you are not absolutely sure what you are doing, leave this
+	  option alone!
+
+	config VMSPLIT_3G
+		bool "3G/1G user/kernel split"
+	config VMSPLIT_3G_OPT
+		bool "3G/1G user/kernel split (for full 1G low memory)"
+	config VMSPLIT_2G
+		bool "2G/2G user/kernel split"
+	config VMSPLIT_1G
+		bool "1G/3G user/kernel split"
+endchoice
+
+config PAGE_OFFSET
+	hex
+	default 0xC0000000
+	default 0xB0000000 if VMSPLIT_3G_OPT
+	default 0x78000000 if VMSPLIT_2G
+	default 0x40000000 if VMSPLIT_1G
+
  config HIGHMEM
  	bool
  	depends on HIGHMEM64G || HIGHMEM4G
diff -u --recursive --new-file --exclude='.*' linux-2.6.15/include/asm-i386/page.h linux/include/asm-i386/page.h
--- linux-2.6.15/include/asm-i386/page.h	2006-01-02 22:21:10.000000000 -0500
+++ linux/include/asm-i386/page.h	2006-01-10 12:04:56.000000000 -0500
@@ -110,10 +110,10 @@
  #endif /* __ASSEMBLY__ */

  #ifdef __ASSEMBLY__
-#define __PAGE_OFFSET		(0xC0000000)
+#define __PAGE_OFFSET		CONFIG_PAGE_OFFSET
  #define __PHYSICAL_START	CONFIG_PHYSICAL_START
  #else
-#define __PAGE_OFFSET		(0xC0000000UL)
+#define __PAGE_OFFSET		((unsigned long)CONFIG_PAGE_OFFSET)
  #define __PHYSICAL_START	((unsigned long)CONFIG_PHYSICAL_START)
  #endif
  #define __KERNEL_START		(__PAGE_OFFSET + __PHYSICAL_START)