Garbage Collection ETW Events

These events collect information pertaining to garbage collection. They help in diagnostics and debugging, including determining how many times garbage collection was performed, how much memory was freed during garbage collection, and so on.

This category consists of the following events:

GCStart_V1 Event

The following table shows the keyword and level. (For more information, see CLR ETW Keywords and Levels.)

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCStart_V1 1 A garbage collection has started.

The following table shows the event data.

Field name Data type Description
Count win:UInt32 The nth garbage collection.
Depth win:UInt32 The generation that is being collected.
Reason win:UInt32 Why the garbage collection was triggered:

0x0 - Small object heap allocation.

0x1 - Induced.

0x2 - Low memory.

0x3 - Empty.

0x4 - Large object heap allocation.

0x5 - Out of space (for small object heap).

0x6 - Out of space (for large object heap).

0x7 - Induced but not forced as blocking.
Type win:UInt32 0x0 - Blocking garbage collection occurred outside background garbage collection.

0x1 - Background garbage collection.

0x2 - Blocking garbage collection occurred during background garbage collection.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

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GCEnd_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCEnd_V1 2 The garbage collection has ended.

The following table shows the event data.

Field name Data type Description
Count win:UInt32 The nth garbage collection.
Depth win:UInt32 The generation that was collected.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

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GCHeapStats_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Description
GCHeapStats_V1 4 Shows the heap statistics at the end of each garbage collection.

The following table shows the event data.

Field name Data type Description
GenerationSize0 win:UInt64 The size, in bytes, of generation 0 memory.
TotalPromotedSize0 win:UInt64 The number of bytes that are promoted from generation 0 to generation 1.
GenerationSize1 win:UInt64 The size, in bytes, of generation 1 memory.
TotalPromotedSize1 win:UInt64 The number of bytes that are promoted from generation 1 to generation 2.
GenerationSize2 win:UInt64 The size, in bytes, of generation 2 memory.
TotalPromotedSize2 win:UInt64 The number of bytes that survived in generation 2 after the last collection.
GenerationSize3 win:UInt64 The size, in bytes, of the large object heap.
TotalPromotedSize3 win:UInt64 The number of bytes that survived in the large object heap after the last collection.
FinalizationPromotedSize win:UInt64 The total size, in bytes, of the objects that are ready for finalization.
FinalizationPromotedCount win:UInt64 The number of objects that are ready for finalization.
PinnedObjectCount win:UInt32 The number of pinned (unmovable) objects.
SinkBlockCount win:UInt32 The number of synchronization blocks in use.
GCHandleCount win:UInt32 The number of garbage collection handles in use.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

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GCCreateSegment_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCCreateSegment_V1 5 A new garbage collection segment has been created. In addition, when tracing is enabled on a process that is already running, this event is raised for each existing segment.

The following table shows the event data.

Field name Data type Description
Address win:UInt64 The address of the segment.
Size win:UInt64 The size of the segment.
Type win:UInt32 0x0 - Small object heap.

0x1 - Large object heap.

0x2 - Read-only heap.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

Note that the size of segments allocated by the garbage collector is implementation-specific and is subject to change at any time, including in periodic updates. Your app should never make assumptions about or depend on a particular segment size, nor should it attempt to configure the amount of memory available for segment allocations.

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GCFreeSegment_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCFreeSegment_V1 6 A garbage collection segment has been released.

The following table shows the event data.

Field name Data type Description
Address win:UInt64 The address of the segment.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

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GCRestartEEBegin_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCRestartEEBegin_V1 7 Resumption from common language runtime suspension has begun.

No event data.

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GCRestartEEEnd_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event Id Raised when
GCRestartEEEnd_V1 3 Resumption from common language runtime suspension has ended.

No event data.

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GCSuspendEE_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCSuspendEE_V1 9 Start of suspension of the execution engine for garbage collection.

The following table shows the event data.

Field name Data type Description
Reason win:UInt16 0x0 - Other.

0x1 - Garbage collection.

0x2 - Application domain shutdown.

0x3 - Code pitching.

0x4 - Shutdown.

0x5 - Debugger.

0x6 - Preparation for garbage collection.
Count win:UInt32 The GC count at the time. Usually, you would see a subsequent GC Start event after this, and its Count would be this Count + 1 as we increase the GC index during a garbage collection.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

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GCSuspendEEEnd_V1 Event

The following table shows the keyword and level:

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information:

Event Event ID Raised when
GCSuspendEEEnd_V1 8 End of suspension of the execution engine for garbage collection.

No event data.

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GCAllocationTick_V2 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCAllocationTick_V2 10 Each time approximately 100 KB is allocated.

The following table shows the event data.

Field name Data type Description
AllocationAmount win:UInt32 The allocation size, in bytes. This value is accurate for allocations that are less than the length of a ULONG (4,294,967,295 bytes). If the allocation is greater, this field contains a truncated value. Use AllocationAmount64 for very large allocations.
AllocationKind win:UInt32 0x0 - Small object allocation (allocation is in small object heap).

0x1 - Large object allocation (allocation is in large object heap).
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.
AllocationAmount64 win:UInt64 The allocation size, in bytes. This value is accurate for very large allocations.
TypeId win:Pointer The address of the MethodTable. When there are several types of objects that were allocated during this event, this is the address of the MethodTable that corresponds to the last object allocated (the object that caused the 100 KB threshold to be exceeded).
TypeName win:UnicodeString The name of the type that was allocated. When there are several types of objects that were allocated during this event, this is the type of the last object allocated (the object that caused the 100 KB threshold to be exceeded).
HeapIndex win:UInt32 The heap where the object was allocated. This value is 0 (zero) when running with workstation garbage collection.

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GCFinalizersBegin_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCFinalizersBegin_V1 14 The start of running finalizers.

No event data.

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GCFinalizersEnd_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCFinalizersEnd_V1 13 The end of running finalizers.

The following table shows the event data.

Field name Data type Description
Count win:UInt32 The number of finalizers that were run.
ClrInstanceID win:UInt16 Unique ID for the instance of CLR or CoreCLR.

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GCCreateConcurrentThread_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)
ThreadingKeyword (0x10000) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCCreateConcurrentThread_V1 11 Concurrent garbage collection thread was created.

No event data.

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GCTerminateConcurrentThread_V1 Event

The following table shows the keyword and level.

Keyword for raising the event Level
GCKeyword (0x1) Informational (4)
ThreadingKeyword (0x10000) Informational (4)

The following table shows the event information.

Event Event ID Raised when
GCTerminateConcurrentThread_V1 12 Concurrent garbage collection thread was terminated.

No event data.

See Also

CLR ETW Events