Fatal trap 12 on ZFS in 8.0-RC1

[Thomas Backman]

On Oct 25, 2009, at 3:10 AM, Doug Poland wrote:

> Hello,
>
> I'm experimenting with ZFS on 8-0-RC1 (amd64) in a VMWare virtual
> machine w/2GB RAM.  In installed ZFS on GPT root using the excellent
> instructions at http://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/RAIDZ1.
>
> All was well until I tried some benchmarking with
> benchmarks/unixbench.  I kept getting kmem_map too small panics on the
> filesystem tests so starting playing with vm.kmem_size.
>
> I finally got unixbench through the first 6 Filesystem Throughput
> tests with:
> vm.kmem_size="1296M"
> vm.kmem_size_max="1296M"
> vfs.zfs.arc_max="128M"
> vfs.zfs.vdev.cache.size="24M" (i think)
>
> Unfortunately, ZFS paniced with:
> Fatal trap 12: page fault while in kernel mode. Now, when I attempt to
> restart the VM, as soon as the "boot menu" is gone, I immediately get
> the same Fatal trap 12 panics again and cannot get past this point.
>
> I've got the 8.0-RC1 DVD and can run Fixit, but have no idea how to
> repair this broken ZFS installation.  Suggestions welcome.

You should be able to break into the loader prompt (choice #6 IIRC)  
and do
unset vm.kmem_size
unset vm...
... etc.
boot

That way, you'll be back to the earlier panics, but at least it'll  
boot. Oh, and the settings aren't permanent, so make editing /boot/ 
loader.conf your first prority.

Regards,
Thomas