CONFIG_VMSPLIT_3G in RHEL5?

[Michael ODonnell]

In kernels built from the kernel.org 2.6.18 kernel sources
you can control whether and where the User mode VM is split
between User/Kernel.  Config directives like CONFIG_VMSPLIT_3G
come into play and are visible in the config files.

But when I look in the config files on a machine that just
had RHEL5 loaded I see no such directives (or anything
else that might be a likely suspect) in any of the config
files like /boot/config-2.6.18-53.1.14.el5PAE.  Does anybody
know whether/how the User/Kernel split is controllable with
those kernels?  Did RHAT diverge from the kernel.org path in
this matter?