Listener is deregistered when returned object is destroyed.
@@ -380,6 +380,7 @@ struct PersistenceProvider
/*
* Register a listener for updates to resource usage.
+ * The listener is deregistered when the returned object is destroyed.
*/
virtual std::unique_ptr<vespalib::IDestructorCallback> register_resource_usage_listener(IResourceUsageListener& listener) = 0;
