Re: 2G memory split

[Mark Lord <lkml@rtr.ca>]

So, the patch would now look like this:


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
+	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/arch/i386/mm/init.c linux/arch/i386/mm/init.c
--- linux-2.6.15/arch/i386/mm/init.c	2006-01-02 22:21:10.000000000 -0500
+++ linux/arch/i386/mm/init.c	2006-01-10 12:06:10.000000000 -0500
@@ -597,6 +597,12 @@
 	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 #endif

+#if !defined(CONFIG_VMSPLIT_3G)
+	/* if the user has less than 960MB of RAM, he should use the default */
+	if (max_low_pfn < (960 * 1024 * 1024 / PAGE_SIZE))
+		printk(KERN_INFO "Memory: less than 960MiB of RAM, you should use the default memory split setting\n");
+#endif
+
 	/* this will put all low memory onto the freelists */
 	totalram_pages += free_all_bootmem();

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)
-
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