externalUsage property Null safety
read / write
The amount of non-Dart memory that is retained by Dart objects. For example, memory associated with Dart objects through APIs such as Dart_NewFinalizableHandle, Dart_NewWeakPersistentHandle and Dart_NewExternalTypedData. This usage is only as accurate as the values supplied to these APIs from the VM embedder. This external memory applies GC pressure, but is separate from heapUsage and heapCapacity.
Implementation
int? externalUsage;