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.

These counters should be covered by related JFR events:
 - ContendedLockAttempts: covered by JavaMonitorEnter event
 - FutileWakeups: not covered, we think this is unnecessary to track
 - Parks: covered by JavaMonitorWait event
 - Notifications: would be covered by new event in JDK-8351187
 - Inflation: already covered by JavaMonitorInflate event
 - Deflations: would be covered by new event in JDK-8351142
 - MonExtant: would be covered by new event in JDK-8351142