ZFS kmem_map too small.

[Martijn Plak]

>> === cat /boot/loader.conf
>> # Load ZFS and load root system from the RAID-Z array.
>> zfs_load="YES"
>> vfs.root.mountfrom="zfs:raid/sys/root"
>>
>> # Tune ZFS and VM parameters.
>> #vfs.zfs.arc_max="64M"
>> #kern.maxvnodes="50000"
>> #vm.kmem_size_max="512M"
>> #vm.kmem_size="512M"
>> === sysctl vm | grep kmem
>> vm.kmem_size_scale: 3
>> vm.kmem_size_max: 335544320
>> vm.kmem_size_min: 0
>> vm.kmem_size: 335544320
>
> The only tuning that is needed (and ZFS will warn now about this) is
> vm.kmem_size/vm.kmem_size_max. Can you set those back to 512M and  
> retry?

I set the vm.kmem_size and vm.kmem_size_max values back to 512M and  
rebooted.

After about 7 hours, during the second "make buildworld" in parallel  
with additional network and disk activity, the machine experienced a  
kmem_map too small panic again.

This time, the machine hung, no crash dump was available.

Do you want me to update the kernel sources? I'm using Nov 5 sources  
at the moment.