4.9 boot problem on em0 platform.

[Deepak Jain]

> Just a guess, but i think you've bumped nmbclusters or nmbufs up
> too much (or perhaps maxsockets, maxfds, ...) and have run out of
> KVA.
> 
> You can tune clusters & mbufs in loader.conf without recompiling
> kernel. You will want to see what vm.zone_kmem_pages, vm.zone_kmem_kvaspace
> are showing you, vmstat -z, vmstat -m, etc.
> 
> You may want to alter VM_KMEM_SIZE_SCALE to e.g. '2' if you are
> trying to put more into the kernel mem space.
> 

The kernel that works from another machine has the same settings 
(NMBCLUSTERS=65536, maxusers=512). The machine has 2GB of RAM.

How do you undo the loader.conf settings when the machine won't boot 
because of the settings you made? :|

thanks,

Deepak