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authorMark Lord <lkml@rtr.ca>2006-02-01 06:06:11 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-01 11:53:21 -0500
commit975b3d3d5b983eb60706d35f0d24cd19f6badabf (patch)
tree39d55db9236ef1acef4e955617296217c3a9fc02 /arch/i386/Kconfig
parent4940fb441275d654cff7d0f7708f91bd8435a85a (diff)
[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>
Diffstat (limited to 'arch/i386/Kconfig')
-rw-r--r--arch/i386/Kconfig37
1 files changed, 37 insertions, 0 deletions
diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 4e9e49a55ea8..d86c865a7cd2 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -448,6 +448,43 @@ config HIGHMEM64G
448 448
449endchoice 449endchoice
450 450
451choice
452 depends on EXPERIMENTAL && !X86_PAE
453 prompt "Memory split"
454 default VMSPLIT_3G
455 help
456 Select the desired split between kernel and user memory.
457
458 If the address range available to the kernel is less than the
459 physical memory installed, the remaining memory will be available
460 as "high memory". Accessing high memory is a little more costly
461 than low memory, as it needs to be mapped into the kernel first.
462 Note that increasing the kernel address space limits the range
463 available to user programs, making the address space there
464 tighter. Selecting anything other than the default 3G/1G split
465 will also likely make your kernel incompatible with binary-only
466 kernel modules.
467
468 If you are not absolutely sure what you are doing, leave this
469 option alone!
470
471 config VMSPLIT_3G
472 bool "3G/1G user/kernel split"
473 config VMSPLIT_3G_OPT
474 bool "3G/1G user/kernel split (for full 1G low memory)"
475 config VMSPLIT_2G
476 bool "2G/2G user/kernel split"
477 config VMSPLIT_1G
478 bool "1G/3G user/kernel split"
479endchoice
480
481config PAGE_OFFSET
482 hex
483 default 0xB0000000 if VMSPLIT_3G_OPT
484 default 0x78000000 if VMSPLIT_2G
485 default 0x40000000 if VMSPLIT_1G
486 default 0xC0000000
487
451config HIGHMEM 488config HIGHMEM
452 bool 489 bool
453 depends on HIGHMEM64G || HIGHMEM4G 490 depends on HIGHMEM64G || HIGHMEM4G