To implement a custom native container, you must annotate your type with the the
NativeContainer attribute. You should also understand how native containers are integrated with the safety system.
There are two major elements to implement:
NativeContainerinstance, so that it can detect and prevent potential conflicts, such as two jobs writing to the same native container at the same time.
NativeContainerisn’t disposed of properly. In this situation, a memory leak happens, where the memory allocated to the
NativeContainerbecomes unavailable for the entire remaining lifetime of the program.
To access usage tracking in your code, use the
AtomicSafetyHandle holds a reference to the central information that the safety system stores for a given native container, and is the main way that the methods of a
NativeContainer interact with the safety system. Because of this, every
NativeContainer instance must contain an
AtomicSafetyHandle field named
AtomicSafetyHandle stores a set of flags that indicate what types of operation can be performed on the native container in the current context. When a job contains a
NativeContainer instance, the job system automatically configures the flags in the
AtomicSafetyHandle to reflect the way that the native container can be used in that job.
When a job tries to read from a
NativeContainer instance, the job system calls the
CheckReadAndThrow method before reading, to confirm that the job has read access to the native container. Similarly, when a job tries to write to a native container, the job system calls
CheckWriteAndThrow before writing, to check that the job has write access to the native container. Two jobs that have been assigned the same
NativeContainer instance have separate
AtomicSafetyHandle objects for that native container, so although they both reference the same set of central information, they can each hold separate flags that indicate what read and write access each job has to the native container.
Unity’s native code primarily implements leak tracking. It uses the
UnsafeUtility.MallocTracked method to allocate the memory needed to store
NativeContainer data, and then uses
UnsafeUtility.FreeTracked to dispose of it.
In earlier versions of Unity the
DisposeSentinel class provides leak tracking. Unity reports a memory leak when the garbage collector collects the
DisposeSentinel object. To create a
DisposeSentinel, use the
Create method, which also initializes the
AtomicSafetyHandle at the same time. When you use this method, you don’t need to initialize the
AtomicSafetyHandle. When the
NativeContainer is disposed of, the
Dispose method disposes of both the
DisposeSentinel and the
AtomicSafetyHandle in a single call.
To identify where the leaked
NativeContainer was created, you can capture the stack trace of where the memory was originally allocated. To do this, use the
NativeLeakDetection.Mode property. You can also access this property in the Editor. To do this, go to Preferences > Jobs > Leak Detection Level and choose the leak detection level you need.
The safety system doesn’t support nested native containers in jobs, because the job system can’t correctly configure the
AtomicSafetyHandle for each individual
NativeContainer inside the larger
To prevent scheduling jobs that use nested native containers, use
SetNestedContainer, which flags a
NativeContainer as nested when they contain other
The safety system provides error messages that indicate when your code doesn’t adhere to safety constraints. To help make the error messages clearer, you can register a
NativeContainer object’s name with the safety system.
To register a name, use
NewStaticSafetyId, which returns a safety ID that you can pass to
SetStaticSafetyId. Once you create a safety ID, you can reuse it for all instances of the
NativeContainer, so a common pattern is to store it in a static member of the container class.
You can also override the error messages for specific safety constraint violations with