Freebsd 8.0 kmem map too small

[Giulio Ferro]

NFS server amd64 Freebsd 8.0 recent (2 days ago)

This server has been running for several months without problems.
Beginning last week, however, I'm experiencing panics (about 1 per day)
with the error in the subject

Current settings:


vm.kmem_size_scale: 3
vm.kmem_size_max: 329853485875
vm.kmem_size_min: 0
vm.kmem_size: 2764046336
...
hw.physmem: 8568225792
hw.usermem: 6117404672
hw.realmem: 9395240960
...
vfs.zfs.l2arc_noprefetch: 0
vfs.zfs.l2arc_feed_secs_shift: 1
vfs.zfs.l2arc_feed_secs: 1
vfs.zfs.l2arc_headroom: 128
vfs.zfs.l2arc_write_boost: 67108864
vfs.zfs.l2arc_write_max: 67108864
vfs.zfs.arc_meta_limit: 431882240
vfs.zfs.arc_meta_used: 431874720
vfs.zfs.arc_min: 215941120
vfs.zfs.arc_max: 1727528960


I've set nothing in either /boot/loader.conf or sysctl.conf


What should I do?