GCSettings.LargeObjectHeapCompactionMode Property

Definition

Namespace:

System.Runtime

Assembly:

System.Runtime.dll

Source:

GCSettings.cs

Gets or sets a value that indicates whether a full blocking garbage collection compacts the large object heap (LOH).

public:
 static property System::Runtime::GCLargeObjectHeapCompactionMode LargeObjectHeapCompactionMode { System::Runtime::GCLargeObjectHeapCompactionMode get(); void set(System::Runtime::GCLargeObjectHeapCompactionMode value); };

public static System.Runtime.GCLargeObjectHeapCompactionMode LargeObjectHeapCompactionMode { get; set; }

static member LargeObjectHeapCompactionMode : System.Runtime.GCLargeObjectHeapCompactionMode with get, set

Public Shared Property LargeObjectHeapCompactionMode As GCLargeObjectHeapCompactionMode

Property Value

GCLargeObjectHeapCompactionMode

One of the enumeration values that indicates whether a full blocking garbage collection compacts the LOH.

Remarks

The LOH is used for allocating memory for large objects (such as arrays) that require more than 85,000 bytes. Because of the performance impact of copying large blocks of memory, the garbage collector ordinarily sweeps the LOH, which involves creating a list of the memory locations that were occupied by dead objects and that can be reused to satisfy future requests for allocation of memory for large objects. However, in apps that make extensive use of the LOH to store transient objects, memory fragmentation can also adversely impact performance. In this case, it is possible to use the LargeObjectHeapCompactionMode property to compact rather than simply sweep the LOH during a garbage collection.

The default value of the LargeObjectHeapCompactionMode property is GCLargeObjectHeapCompactionMode.Default, which indicates that the LOH is not compacted during garbage collections. If you assign the property a value of GCLargeObjectHeapCompactionMode.CompactOnce, the LOH is compacted during the next full blocking garbage collection, and the property value is reset to GCLargeObjectHeapCompactionMode.Default.

Note

Background garbage collections are not blocking. This means that, if you set the LargeObjectHeapCompactionMode property to GCLargeObjectHeapCompactionMode.CompactOnce, any background generation 2 collections that occur subsequently do not compact the LOH. Only the first blocking generation 2 collection compacts the LOH.

After the LargeObjectHeapCompactionMode property is set to GCLargeObjectHeapCompactionMode.CompactOnce, the next full blocking garbage collection (and compaction of the LOH) occurs at an indeterminate future time. You can compact the LOH immediately by using code like the following:

GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
GC.Collect();

GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce
GC.Collect()

See also

• GCLargeObjectHeapCompactionMode