I recently discovered that FreeBSD has a neat way of doing kernel lock profiling. To use it you just need to add a single line in your kernel config script:

options  LOCK_PROFILING

Rebuild, install and reboot your new kernel. To check if it's working call sysctl debug.lock, you should see some options. Now try:

> sysctl debug.lock.prof.enable=1

> (launch a program or just wait a few seconds)

> sysctl debug.lock.prof.enable=0

> sysctl debug.lock.prof.stats

The stats include: file:line and lock type, maximum time held, total time held, total wait time, count, average time held, average wait time, contention while holding, contention while locking

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