CONFIG_VMSPLIT_3G in RHEL5?

Jarod Wilson jarod at wilsonet.com
Wed Jul 16 12:56:34 EDT 2008


On Wed, 2008-07-16 at 12:20 -0400, Michael ODonnell wrote:
> 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?

No.

excerpt from arch/i386/Kconfig:
--
choice
        depends on EXPERIMENTAL && !X86_PAE
        prompt "Memory split" if EMBEDDED
        default VMSPLIT_3G
--

Note the !X86_PAE part. At least above, you mentioned looking in a PAE
kernel config. :)

However, the VMSPLIT options also will not show up if CONFIG_NOHIGHMEM
isn't set to y. The i686 non-PAE RHEL5 kernel doesn't set that, because
it uses CONFIG_HIGHMEM4G=y.

So the option is there in Kconfig in the source, but you'd have to
change some options further up in the Kconfig hierarchy to expose them.


-- 
Jarod Wilson
jarod at wilsonet.com



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