.NET runtime garbage collection 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, etc. For more information about how to use these events for diagnostic purposes, see logging and tracing .NET applications

GCStart_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
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 CoreCLR.

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 CoreCLR.

GCHeapStats_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 Description
GCHeapStats_V2 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 CoreCLR.
GenerationSize4 win:UInt64 The size, in bytes, of the pinned object heap.
TotalPromotedSize4 win:UInt64 The number of bytes that survived in the pinned object heap after the last collection.

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 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.

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 CoreCLR.

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.

This event does not have any event data.

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.

This event does not have any event data.

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.

This event does not have any event data.

GCSuspendEEBegin_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
GCSuspendEEBegin_V1 8 Start of suspension of the execution engine for garbage collection.
Field name Data type Description
Count win:UInt32 The nth garbage collection.
Reason win:UInt32 Reason for EE suspension.

0x0: Suspend for Other

0x1: Suspend for GC.

0x2: Suspend for AppDomain shutdown.

0x3: Suspend for code pitching.

0x4: Suspend for shutdown.

0x5: Suspend for debugger.

0x6: Suspend for GC Prep.

0x7: Suspend for debugger sweep

GCAllocationTick_V3 event

The following table shows the keyword and level:

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

The following table shows the event information:

Event Event ID Raised when
GCAllocationTick_V3 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).
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.
Address win:Pointer The address of the last allocated object.
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.

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.

This event does not have any event data.

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.

This event does not have any event data.

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.

This event does not have any event data.

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.

SetGCHandle event

The following table shows the keyword and level:

Keyword for raising the event Level
GCHandleKeyword (0x2) Informational (4)

The following table shows the event information:

Event Event ID Raised when
SetGCHandle 30 A GC Handle has been set.

The following table shows the event data:

Field name Data type Description
HandleID win:Pointer The address of the allocated handle.
ObjectID win:Pointer The address of the object whose handle was created.
Kind win:UInt32 The type of GC handle that was set.

0x0: WeakShort

0x1: WeakLong

0x2: Strong

0x3: Pinned

0x4: Variable

0x5: RefCounted

0x6: Dependent

0x7: AsyncPinned

0x8: SizedRef
Generation win:UInt32 The generation of the object whose handle was created.
AppDomainID win:UInt64 The AppDomain ID.
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.

DestroyGCHandle event

The following table shows the keyword and level:

Keyword for raising the event Level
GCHandleKeyword (0x2) Informational (4)

The following table shows the event information:

Event Event ID Raised when
DestroyGCHandle 31 A GC Handle is destroyed.

The following table shows the event data:

Field name Data type Description
HandleID win:Pointer The address of the destroyed handle.
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.

PinObjectAtGCTime event

The following table shows the keyword and level:

Keyword for raising the event Level
GCKeyword (0x1) Verbose (5)

The following table shows the event information:

Event Event ID Raised when
PinObjectAtGCTime 33 An object was pinned during a GC.

The following table shows the event data:

Field name Data type Description
HandleID win:Pointer The address of the handle.
ObjectID win:Pointer The address of the pinned object.
ObjectSize win:UInt64 The size of the pinned object.
TypeName win:UnicodeString The name of the type of the pinned object.
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.

GCTriggered event

The following table shows the keyword and level:

Keyword for raising the event Level
GCKeyword (0x1) Verbose (5)

The following table shows the event information:

Event Event ID Raised when
GCTriggered 33 A GC has been triggered.

The following table shows the event data:

Field name Data type Description
Reason win:UInt32 The reason a GC was triggered.

0x0: AllocSmall

0x1: Induced

0x2: LowMemory

0x3: Empty

0x4: AllocLarge

0x5: OutOfSpaceSmallObjectHeap

0x6: OutOfSpaceLargeObjectHeap

0x7:InducedNoForce

0x8: Stress

0x9: InducedLowMemory
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.

IncreaseMemoryPressure event

The following table shows the keyword and level:

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

The following table shows the event information:

Event Event ID Raised when
IncreaseMemoryPressure 200 Memory pressure was increased.

The following table shows the event data:

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

DecreaseMemoryPressure event

The following table shows the keyword and level:

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

The following table shows the event information:

Event Event ID Raised when
DecreaseMemoryPressure 201 Memory pressure was decreased.

The following table shows the event data:

Field Name Data type Description
BytesFreed win:UInt32 Bytes freed.
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.

GCMarkWithType event

The following table shows the keyword and level:

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

The following table shows the event information:

Event Event ID Raised when
GCMarkWithType 202 A GC root has been marked during GC mark phase.

The following table shows the event data:

Field Name Data type Description
HeapNum win:UInt32 The heap number.
ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.
Type win:UInt32 The GC root type.

0x0: Stack

0x1: Finalizer

0x2: Handle

0x3: Older

0x4: SizedRef

0x5: Overflow

Bytes win:UInt64 The number of bytes marked.

GCJoin_V2 event

The following table shows the keyword and level:

Keyword for raising the event Level
GCKeyword (0x1) Verbose (5)

The following table shows the event information:

Event Event ID Raised when
GCJoin_V2 203 A GC thread joined.

The following table shows the event data:

Field name Data type Description
Heap win:UInt32 The heap number
JoinTime win:UInt32 Indicates whether this event is fired at the start of a join or end of a join (0x0 for join start, 0x1 for join end)
JoinType win:UInt32 The join type.

0x0: Last Join

0x1: Join

0x2: Restart

0x3: First Reverse Join

0x4: Reverse Join

ClrInstanceID win:UInt16 Unique ID for the instance of CoreCLR.