.NET runtime thread pool events

The events described in this article collect information about worker and I/O threads in the threadpool. For more information about how to use these events for diagnostic purposes, see logging and tracing .NET applications

IOThreadCreate_V1 event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Raised when
IOThreadCreate_V1	44	An I/O thread is created in the thread pool.

The following table shows the event data.

Field name	Data type	Description
Count	win:UInt64	Number of I/O threads, including the newly created thread.
NumRetired	win:UInt64	Number of retired worker threads.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

IOThreadTerminate_V1 event

The following table shows the keyword and level

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Raised when
IOThreadTerminate	45	An I/O thread is terminated in the thread pool.

The following table shows the event data.

Field name	Data type	Description
Count	win:UInt64	Number of I/O threads remaining in the thread pool.
NumRetired	win:UInt64	Number of retired I/O threads.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

IOThreadRetire_V1 event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Raised when
IOThreadRetire_V1	46	An I/O thread becomes a retirement candidate.

The following table shows the event data.

Field name	Data type	Description
Count	win:UInt64	Number of I/O threads remaining in the thread pool.
NumRetired	win:UInt64	Number of retired I/O threads.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

IOThreadUnretire_V1 event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Raised when
IOThreadUnretire_V1	47	An I/O thread is unretired because of I/O that arrives within a waiting period after the thread becomes a retirement candidate.

The following table shows the event data.

Field name	Data type	Description
Count	win:UInt64	Number of I/O threads in the thread pool, including this one.
NumRetired	win:UInt64	Number of retired I/O threads.
ClrInstanceID	Win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadStart event

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

Event	Event ID	Description
ThreadPoolWorkerThreadStart	50	A worker thread is created.

Field name	Data type	Description
ActiveWorkerThreadCount	win:UInt32	Number of worker threads available to process work, including those that are already processing work.
RetiredWorkerThreadCount	win:UInt32	Number of worker threads that are not available to process work, but that are being held in reserve in case more threads are needed later.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadStop event

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

Event	Event ID	Description
ThreadPoolWorkerThreadStop	51	A worker thread is stopped.

Field name	Data type	Description
ActiveWorkerThreadCount	win:UInt32	Number of worker threads available to process work, including those that are already processing work.
RetiredWorkerThreadCount	win:UInt32	Number of worker threads that are not available to process work, but that are being held in reserve in case more threads are needed later.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadWait event

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

Event	Event ID	Description
ThreadPoolWorkerThreadWait	57	A worker thread starts waiting for work.

Field name	Data type	Description
ActiveWorkerThreadCount	win:UInt32	Number of worker threads available to process work, including those that are already processing work.
RetiredWorkerThreadCount	win:UInt32	Number of worker threads that are not available to process work, but that are being held in reserve in case more threads are needed later.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadRetirementStart event

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

Event	Event ID	Description
ThreadPoolWorkerThreadRetirementStart	52	A worker thread retires.

Field name	Data type	Description
ActiveWorkerThreadCount	win:UInt32	Number of worker threads available to process work, including those that are already processing work.
RetiredWorkerThreadCount	win:UInt32	Number of worker threads that are not available to process work, but that are being held in reserve in case more threads are needed later.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadRetirementStop event

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

Event	Event ID	Description
ThreadPoolWorkerThreadRetirementStop	53	A retired worker thread becomes active again.

Field name	Data type	Description
ActiveWorkerThreadCount	win:UInt32	Number of worker threads available to process work, including those that are already processing work.
RetiredWorkerThreadCount	win:UInt32	Number of worker threads that are not available to process work, but that are being held in reserve in case more threads are needed later.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadAdjustmentSample event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolWorkerThreadAdjustmentSample	54	Refers to the collection of information for one sample; that is, a measurement of throughput with a certain concurrency level, in an instant of time.

The following table shows the event data.

Field name	Data type	Description
Throughput	win:Double	Number of completions per unit of time.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadAdjustmentAdjustment event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolWorkerThreadAdjustmentAdjustment	55	Records a change in control, when the thread injection (hill-climbing) algorithm determines that a change in concurrency level is in place.

The following table shows the event data.

Field name	Data type	Description
AverageThroughput	win:Double	Average throughput of a sample of measurements.
NewWorkerThreadCount	win:UInt32	New number of active worker threads.
Reason	win:UInt32	Reason for the adjustment. 0x0 - Warmup. 0x1 - Initializing. 0x2 - Random move. 0x3 - Climbing move. 0x4 - Change point. 0x5 - Stabilizing. 0x6 - Starvation. 0x7 - Thread timed out. 0x8 - Cooperative blocking.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolWorkerThreadAdjustmentStats event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Verbose (5)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolWorkerThreadAdjustmentStats	56	Gathers data on the thread pool.

The following table shows the event data

Field name	Data type	Description
Duration	win:Double	Amount of time, in seconds, during which these statistics were collected.
Throughput	win:Double	Average number of completions per second during this interval.
ThreadWave	win:Double	Reserved for internal use.
ThroughputWave	win:Double	Reserved for internal use.
ThroughputErrorEstimate	win:Double	Reserved for internal use.
AverageThroughputErrorEstimate	win:Double	Reserved for internal use.
ThroughputRatio	win:Double	The relative improvement in throughput caused by variations in active worker thread count during this interval.
Confidence	win:Double	A measure of the validity of the ThroughputRatio field.
NewcontrolSetting	win:Double	The number of active worker threads that serve as the baseline for future variations in active thread count.
NewThreadWaveMagnitude	win:UInt16	The magnitude of future variations in active thread count.
ClrInstanceID	win:UInt16	Unique ID for the instance of CLR or CoreCLR.

ThreadPoolEnqueue event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Verbose (5)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolEnqueue	61	A work item was enqueued in the thread pool queue.

The following table shows the event data

Field name	Data type	Description
WorkID	win:Pointer	Pointer to the work request.
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.

ThreadPoolDequeue event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Verbose (5)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolDequeue	62	A work item was dequeued from the thread pool queue.

The following table shows the event data

Field name	Data type	Description
WorkID	win:Pointer	Pointer to the work request.
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.

ThreadPoolIOEnqueue event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Verbose (5)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolIOEnqueue	63	A thread enqueues an IO completion notification after an async IO completion occurs.

The following table shows the event data

Field name	Data type	Description
NativeOverlapped	win:Pointer	Reserved for internal use.
Overlapped	win:Pointer	Reserved for internal use.
MultiDequeues	win:Boolean	Reserved for internal use.
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.

ThreadPoolIODequeue event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Verbose (5)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolIODequeue	64	A thread dequeues the IO completion notification.

The following table shows the event data

Field name	Data type	Description
NativeOverlapped	win:Pointer	Reserved for internal use.
Overlapped	win:Pointer	Reserved for internal use.
MultiDequeues	win:Boolean	Reserved for internal use.
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.

ThreadPoolIOPack event

The following table shows the keyword and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Verbose (5)

The following table shows the event information.

Event	Event ID	Description
ThreadPoolIOPack	65	ThreadPool overlapped IO pack is called.

The following table shows the event data

Field name	Data type	Description
NativeOverlapped	win:Pointer	Reserved for internal use.
Overlapped	win:Pointer	Reserved for internal use.
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.

ThreadCreating event

The following table shows the keywords and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Description
ThreadCreating	70	Thread has been created.

The following table shows the event data.

Field name	Data type	Description
ID	win:Pointer	Thread ID
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.

ThreadRunning event

The following table shows the keywords and level.

Keyword for raising the event	Level
ThreadingKeyword (0x10000)	Informational (4)

The following table shows the event information.

Event	Event ID	Description
ThreadRunning	71	Thread has started running.

The following table shows the event data.

Field name	Data type	Description
ID	win:Pointer	Thread ID
ClrInstanceID	win:UInt16	Unique ID for the instance of CoreCLR.