[PATCH] VMSPLIT config options

Enable selection of different user/kernel VM splits for i386, including an
optimized mode for 1GB physical RAM, which gives the kernel a direct (non
HIGHMEM) mapping to the entire 1GB rather than just the first 896MB.

There is a similarly a similarly optimized mode for machines with exactly 2GB
of physical RAM.

This can speed up the kernel by avoiding having to create/destroy temporary
HIGHMEM mappings, and by not having to include HIGHMEM support at all on such
machines.  The flip side is that there's less virtual addressing left for
userspace in these alternatives, and some binary-only kernel modules may
misbehave unless rebuilt with the same VMSPLIT option as the main kernel
image.

Original idea/patch from Jens Axboe, modified based on suggestions from Linus
et al.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/asm-i386/page.h b/include/asm-i386/page.h
index 73296d9924fb..997ca5d17876 100644
--- a/include/asm-i386/page.h
+++ b/include/asm-i386/page.h
@@ -110,10 +110,10 @@ extern int page_is_ram(unsigned long pagenr);
 #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)