I have a server running NetBSD-1.5.2-macppc, and I'd like to figure out how
to adjust the kernel to make better use of 1.25G of memory.

I've already determined that a macppc-current kernel with UBC isn't stable
under load, either with or without NEWPMAP, so until someone fixes the
problems there I'm stuck with 1.5.2.

I've currently got some of the memory pulled out to bring the machine down
to 512M so it will boot.  My goals are:

- get the machine to boot without panicing with all the memory installed
- allocate a large percentage of memory to filesystem cache (probably 50%)
- continue the history of 170-day uptimes the machine had before the upgrade

Assuming I know absolutely nothing about kernel memory management or the
relevant kernel config options (which isn't far from the truth), can someone
explain how to do this right?  I want to make sure I don't set myself up for
a panic down the road by making the sizes of various things in the kernel
unbalanced.  

I've gone through the mailing list archives and found various discussions on
this subject, but the answers I've found were all relatively arbitrary ("set
this option to this number" with no explanation of how to calculate the
number) or vague ("you'll probably want to increase this other option" with
no indication of what the default is or how much to change it by).

Ideally, I'd like to see the following kernel options (as well as any other
relevant ones I've missed) explained in such a way that someone who hasn't
read any of the kernel code can correctly calculate (not guess) the values
they should use:

NMBCLUSTERS
NKMEMPAGES
BUFCACHE
NBUF
BUFPAGES

It would also be useful to know the default value for each option for
macppc, the interactions between the different values, and any other
implicit limits (i.e. what particular limit gets exceeded that causes macppc
machines with 1G+ of memory to panic on boot).

Thanks,
-- monroe
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Monroe Williams                                  monroe@criticalpath.com