Manual browser: lockstat(8)

LOCKSTAT(8) System Manager's Manual LOCKSTAT(8)


lockstatdisplay kernel locking statistics


lockstat [-cdeflMmpstx] [-b nbuf] [-E event] [-F func] [-L lock] [-N nlist] [-o file] [-T type] command ...


The lockstat command enables system wide tracing of kernel lock events, executes the specified command, and when finished reports statistics to the user.

Tracing may be ended early by sending SIGINT (Ctrl-C) to the process being executed by lockstat.

The lockstat pseudo-device driver must be present in the kernel, and the lockstat command may only be used by the root user.

The options are as follows:

-b nbuf
Adjust the number of trace buffers allocated by the kernel to nbuf.
Report percentage of total events by count, and sort the output by number of events. The default is to key on event timings.
Disable lockstat. This is useful when a program crashed leaving the lockstat kernel driver enabled.
-E event
Limit tracing to one type of event. Use the -e option to list valid events.
List valid event types for the -E option and exit.
-F func
Limit tracing to locking operations performed within the specified function. func must be the name of a valid function in the kernel.
Trace only by calling functions; do not report on individual locks.
-L lock
Limit tracing to one lock. lock may either be the name of a lock object in the kernel, or a kernel virtual address.
Trace only by lock; do not report on calling functions.
Merge lock addresses within unique objects.
Merge call sites within unique functions.
-N nlist
Extract symbol information from the nlist file.
-o file
Send output to the file named by file, instead of the standard output (the default).
Show the average number of events and time spent per CPU. The default is to show the total values. May be used in conjunction with the -s option.
Show the average number of events per second, and the average time spent per second. The default is to show the total values.
-T type
Limit tracing to one type of lock. Use the -t option to list valid lock types.
List valid lock types for the -T option and exit.
Summarize events, and do not report on lock types.


lockstat control device


# lockstat -L uvm_pageqlock sleep 10 
Elapsed time: 10.01 seconds. 
-- Adaptive mutex spin 
Total%  Count   Time/ms          Lock                       Caller 
------ ------- --------- ---------------------- ------------------------------ 
100.00    1281      0.78 uvm_pageqlock          <all> 
 39.81     385      0.31 uvm_pageqlock          uvm_fault_internal+11cc 
 30.98     358      0.24 uvm_pageqlock          uvm_fault_internal+bb1 
 28.06     522      0.22 uvm_pageqlock          uvm_anfree+132 
  0.51       5      0.00 uvm_pageqlock          ubc_fault+28f 
  0.20       4      0.00 uvm_pageqlock          uvm_fault_internal+12b6 
  0.18       2      0.00 uvm_pageqlock          uao_detach_locked+58 
  0.11       2      0.00 uvm_pageqlock          uvm_fault_internal+7d5 
  0.08       2      0.00 uvm_pageqlock          ufs_balloc_range+160 
  0.07       1      0.00 uvm_pageqlock          uvm_fault_internal+107b


lockstat: incompatible lockstat interface version

The kernel device driver does not match the version of the lockstat command.

lockstat: overflowed available kernel trace buffers

Increase the number of buffers using the -b option.

lockstat: ioctl: Invalid argument

The number of trace buffers is outside the minimum and maximum bounds set by the kernel.


The lockstat command appeared in NetBSD 4.0.
March 6, 2013 NetBSD 7.0