Can you describe the main stages of the memory cleanup process in automatic memory management systems?

Memory cleanup process in automatic memory management systems usually includes several main stages:

1. Allocation — the system allocates memory for new objects or data.

2. Marking — the garbage collector determines which objects in memory are still in use (reachable) and which are not. This is usually done by traversing the object graph starting from root references.

3. Sweeping — objects that were not marked as reachable are considered garbage and are freed.

4. Compacting — an optional stage where remaining objects are moved to reduce memory fragmentation.

In Android, for example, a garbage collector in the Dalvik or ART environment implements these stages to manage application memory.