root@fledgling:~ # lockstat dd if=/dev/zero of=/testfile bs=1M count=44
44+0 records in
44+0 records out
46137344 bytes transferred in 0.062202 secs (741737312 bytes/sec)

R/W writer spin on writer: 984 events in 0.094 seconds (10451 events/sec)

Count indv cuml rcnt     nsec Lock                   Caller                  
-------------------------------------------------------------------------------
  228  23%  23% 0.00     3023 Per-Filesystem Softdep Lock 0xc00000000308837c      
  188  19%  42% 0.00     3219 vm object              bufdone+0x45c           
  132  13%  56% 0.00     2189 vm object              bdwrite+0x2f4           
  123  12%  68% 0.00     2394 bufobj interlock       bufobj_wdrop+0x13c      
  108  11%  79% 0.00     2093 Per-Filesystem Softdep Lock 0xc00000000308e270      
   53   5%  85% 0.00     1136 bufobj interlock       bqrelse+0x2a0           
   45   5%  89% 0.00     2608 Per-Filesystem Softdep Lock (usermode)              
   32   3%  92% 0.00     3348 bufobj interlock       (usermode)              
   19   2%  94% 0.00     3143 bufobj interlock       getblkx+0x6a4           
   13   1%  96% 0.00     1559 Per-Filesystem Softdep Lock 0xc000000003090bdc      
   10   1%  97% 0.00      361 vm object              allocbuf+0xa84          
   10   1%  98% 0.00     1368 vm object              (usermode)              
   10   1%  99% 0.00     1158 Per-Filesystem Softdep Lock softdep_setup_blkmapdep+0x294
    8   1%  99% 0.00      822 Per-Filesystem Softdep Lock 0xc00000000308ef48      
    3   0% 100% 0.00     1022 bufobj interlock       reassignbuf+0x350       
    1   0% 100% 0.00      471 vm object              vnode_pager_setsize+0x2bc
    1   0% 100% 0.00      317 Per-Filesystem Softdep Lock softdep_prealloc+0x460  
-------------------------------------------------------------------------------

R/W writer spin on readers: 27 events in 0.094 seconds (287 events/sec)

Count indv cuml rcnt     nsec Lock                   Caller                  
-------------------------------------------------------------------------------
   25  93%  93% 0.00     1717 bufobj interlock       bufobj_wdrop+0x13c      
    2   7% 100% 0.00     3396 bufobj interlock       (usermode)              
-------------------------------------------------------------------------------

R/W reader spin on writer: 16 events in 0.094 seconds (170 events/sec)

Count indv cuml rcnt     nsec Lock                   Caller                  
-------------------------------------------------------------------------------
   16 100% 100% 0.00     2167 bufobj interlock       __rw_rlock_int+0x9c     
-------------------------------------------------------------------------------