High mem (4GB) support on FreeBSD 4.8

Mike Silbersack silby at silby.com
Sat Oct 18 13:41:13 PDT 2003

On Sat, 18 Oct 2003, Yaoping Ruan wrote:

> Hi:
> I installed the 4.8 release on a new box with 4GB memory, and found
> kernel panic when I tried to write date. But the system run great with
> only 2GB memory. Is there any kernel compiling option in the LINT, like
> the "high mem" option in Linux?
> BTW, we also tried 4.6 release, didn't have this problem but had some
> different issues.

Some of the kernel autoscaling values may be off with 4GB machines; I
believe that this has been fixed with 4.9, so running 4.9-RC3 might be the
easiest answer.

Alternately, try the following:

1.  Check the mailing list archives, there might be a better explanation
than I'm about to give.

2.  Play with the amount of memory available using the hw.physmem tunable
in loader.conf; you can set to to intermediate values, such as 3G, etc.

3.  Tweak the tunable kern.vm.kmem.size upwards, it defaults to 200M,
which is probably too small for a 4G machine; try 300 or 400M.

Don't worry about PAE, that's only needed if you have _more_ than 4G of

Mike "Silby" Silbersack

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