Messages in this thread | | | Date | Tue, 01 May 2007 09:32:33 -0400 | From | Mark Lord <> | Subject | Re: [PATCH] [30/30] x86_64: Add missing !X86_PAE dependincy to the 2G/2G split. |
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William Lee Irwin III wrote: > On Tue, May 01, 2007 at 05:58:29AM +0200, Andi Kleen wrote: >> From: ebiederm@xmission.com >> When in PAE mode we require that the user kernel divide to be >> on a 1G boundary. The 2G/2G split does not have that property >> so require !X86_PAE >> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> >> --- >> arch/i386/Kconfig | 1 + >> 1 files changed, 1 insertions(+), 0 deletions(-) > > What on earth? > > config PAGE_OFFSET > hex > default 0xB0000000 if VMSPLIT_3G_OPT > default 0x78000000 if VMSPLIT_2G > default 0x40000000 if VMSPLIT_1G > default 0xC0000000 > > This appears to have been introduced by: > commit 975b3d3d5b983eb60706d35f0d24cd19f6badabf > Author: Mark Lord <lkml@rtr.ca> > Date: Wed Feb 1 03:06:11 2006 -0800 > [PATCH] VMSPLIT config options > > There's some sort of insanity going on here. Since when is 0x78000000 > a 2GB/2GB split? Mark, dare I ask what you were thinking? That should > be VMSPLIT_2G_OPT for 2GB laptops analogously to VMSPLIT_3G_OPT, if > nothing else, as it's certainly not 2GB/2GB.
You need to go search the archives and read the *extensive* thread on this from when it was introduced. Lots of high profile kernel developers were in on this one.
The idea is really simple: eliminate the need for HIGHMEM on common machines.
And yes, VMSPLIT_2G really means VMSPLIT_2G_OPT, in the same way as the (added last) VMSPLIT_3G_OPT flag.
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