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Date: Sun, 27 Feb 2005 14:21:07 +0100
From: "O. Hartmann" <ohartman@uni-mainz.de>
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Subject: Kernel/Userland Mem-Space Tuning (1/3 on IA32)
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Hello.
I read about address space division of recent operating systems like 
Linux and Windows XP.
In both cases, the whole address space of the 32 or 64 Bit system is 
divided into halfes, 2GB for
kernel, 2 GB for process(es) (speaking in 32Bit words). The same in 
64bit systems like AMD64.
Those who happily utilize an AMD64 based machine are not (yet) involved 
by this problem,
but on recent 32 Bit architectures someone can run out of process space, 
like me! Some
geophysical modelling software needs more than the allowed 2GB address 
space and therefore
I would like to ask whether FreeBSD (my preferred OS) has a 'knob' to 
change the kernel/userland parity
of the address space like it is done in Windows with a special knob at 
boot time (/W3GB I think, but I'm not
sure about the exakt syntax but I know someone can change the half by 
half parity towards 1 to 3 in
XP). I'm not sure whether FreeBSD divides kernel/userland address space 
this way, I know Linux and
Windows does and on Windows we changed this (not yet on Linux and not 
yet on our FreeBSD machines
(OS version >5.0, mostly FreeBSD 5.3-R or 5.4-PRERELEASE).

Any help is appreciated.

Thanks, Oliver