# Contention ETW events

Contention events are raised whenever there is contention for System.Threading.Monitor locks or native locks used by the runtime. Contention occurs when a thread is waiting for a lock while another thread possesses the lock.

The following table shows the keyword under which contention events are raised, and the level of the events. For more information, see CLR ETW Keywords and Levels.

Keyword for raising the event Level
ContentionKeyword (0x4000) Informational (4)

The following table shows event information:

Event Event ID Raised when
ContentionStart_V1 81 Contention starts. This event does not include the amount of spinning time before a thread waits to acquire a lock; it is raised only when the thread waits to acquire a lock.
ContentionStop 91 Contention ends.

The following table shows event data:

Field name Data type Description
Flags win:UInt8 0 for managed; 1 for native.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR.