There is a bunch of ObjectMonitor performance counters:

PerfCounter * ObjectMonitor::_sync_ContendedLockAttempts       = nullptr;
PerfCounter * ObjectMonitor::_sync_FutileWakeups               = nullptr;
PerfCounter * ObjectMonitor::_sync_Parks                       = nullptr;
PerfCounter * ObjectMonitor::_sync_Notifications               = nullptr;
PerfCounter * ObjectMonitor::_sync_Inflations                  = nullptr;
PerfCounter * ObjectMonitor::_sync_Deflations                  = nullptr;
PerfLongVariable * ObjectMonitor::_sync_MonExtant              = nullptr;


They seem to be seldom used, and their continued maintenance comes with at least two problems, both of which come down to intrinsic race against VM shutdown, see JDK-8049304 and JDK-8348402. Additionally, these get updated on locking paths, and attempts to do extra things, including synchronization, might obscure some of the bugs.