nia measurements on stuck core:
0xc0000000030d0bc0   mmu_radix_pmap_is_prefaultable   ||  
0xc0000000030d0c14   mmu_radix_pmap_is_prefaultable
0xc0000000030d0cac   mmu_radix_pmap_is_prefaultable
0xc000000003070630   vm_map_lookup
0xc0000000030c58fc   pmap_invalidate_all  ||||
0xc00000000306061c   vm_fault_prefault
0xc0000000024013e4   ast_frame_leave
0xc000000002c08700   __rw_rlock_int
0xc0000000030cd6b0   pmap_nofault (doing ptesync!) ||
0xc000000003090bb4   vm_phys_paddr_to_vm_page