OnGcGlobalHeapHistory.cs

// This event is used to figure out if a collection is compacting or not
// Note: last event for background GC (will be GCHeapStats for ephemeral (0/1) and non concurrent gen 2 collections)
private void OnGcGlobalHeapHistory(EventWrittenEventArgs e)
{
    var currentGC = GetCurrentGC(_gcInfo);

    // check unexpected event (we should have received a GCStart first)
    if (currentGC == null)
        return;
    var globalMask = GetFieldValue<GCGlobalMechanisms>(e, "GlobalMechanisms");
    currentGC.IsCompacting =
        (globalMask & GCGlobalMechanisms.Compaction) == GCGlobalMechanisms.Compaction;

    // this is the last event for gen 2 background collections
    if ((GetFieldValue<int>(e, "CondemnedGeneration") == 2) && (currentGC.Type == GCType.BackgroundGC))
    {
        // check unexpected generation mismatch
        var globalMask = (GCGlobalMechanisms)GetFieldValue<uint>(e, "GlobalMechanisms");
        currentGC.IsCompacting =
            (globalMask & GCGlobalMechanisms.Compaction) == GCGlobalMechanisms.Compaction;

        // this is the last event for gen 2 background collections
        if ((GetFieldValue<uint>(e, "CondemnedGeneration") == 2) && (currentGC.Type == GCType.BackgroundGC))
 {
            GcEvents?.Invoke(this, BuildGcArgs(currentGC));
            ClearCollections(_gcInfo);
        }
    }
}