While compiling lftp:

uvm_swapin: rewiring stack failed: 5                              
Stopped in pid 0.1 (swapper) at netbsd:cpu_Debugger+0x4:        leave           
cpu_Debugger(c389c6b4,0,c033af48,c389c6b4,c389c6b4) at netbsd:cpu_Debugger+0x4  
panic(c029d1e0,5,c033af68,c0234023,c389c6b4) at netbsd:panic+0x11d              
uvm_scheduler(c389c6b4,c02800cd,c033af68,c0233f56,0) at netbsd:uvm_scheduler    
uvm_scheduler(c02e73a0,0,c02eb73c,c027de96,1) at netbsd:uvm_scheduler+0xcf      
main(0,0,0,0,0) at netbsd:main+0x68f                                            
ds          0x11                                                                
es          0x11                                                                
fs          0x31                                                                
gs          0x11                                                                
edi         0x1                                                                 
esi         0x100                                                               
ebp         0xc033af08  xbd_allxr+0x4c268                                       
ebx         0xc033af34  xbd_allxr+0x4c294                                       
edx         0                                                                   
ecx         0                                                                   
eax         0x61e                                                               
eip         0xc0244d00  cpu_Debugger+0x4                                        
cs          0x9                                                                 
eflags      0x202                                                               
esp         0xc033af08  xbd_allxr+0x4c268                                
ss          0x11                                                                
netbsd:cpu_Debugger+0x4:        leave                                           
Stopped in pid 0.1 (swapper) at netbsd:cpu_Debugger+0x4:        leave

The same thing happened if I use my xennet devices heavily... :(