In determining when to schedule garbage collection, the runtime takes into account how much managed memory is allocated. If a small managed object allocates a large amount of unmanaged memory, the runtime takes into account only the managed memory, and thus underestimates the urgency of scheduling garbage collection. The AddMemoryPressure method informs the runtime of this additional pressure on system memory.

In the simplest usage pattern, a managed object allocates unmanaged memory in the constructor and releases it in the Dispose or Finalize method. Call the AddMemoryPressure method after allocating the unmanaged memory, and call the RemoveMemoryPressure method after releasing it.

In more complicated scenarios, where the unmanaged memory allocation changes substantially during the lifetime of the managed object, you can call the AddMemoryPressure and RemoveMemoryPressure methods to communicate these incremental changes to the runtime.

Caution:
You must ensure that you remove exactly the amount of pressure you add. Failing to do so can adversely affect the performance of the system in applications that run for long periods of time.

• SecurityPermission 

  for the ability to call unmanaged code when manipulating garbage-collection priority. Associated enumeration: UnmanagedCode

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

.NET Framework

Reference