[why lower bound?]

Because the kmapents are used for other purposes than mapping u-areas
or whateveritis, and I dont know just how many are needed..  

The default in 1.3.x is 500.  chuck cranor bumped that to 1000 in
-current, after running into a bug with running out of kmapents.  and
the patch is against -current.  I'd leave 500 as the lower limiit for
1.3.x, I'd leave the lower bound at 500.


>(And if someone kicks NPROC up high enough to cause problems with memory
>left after MAX_KMAPENT, they probably need more memory for whatever
>they're doing anyway...)

but mark allman looked around, bumped NPROC, and even with gobs of
memory, it still didnt DTRT. With the patch, it would.