com.oracle.svm.core.heap

Class CollectionWatcher

java.lang.Object

com.oracle.svm.core.heap.AllocationFreeList.Element<CollectionWatcher>

com.oracle.svm.core.heap.CollectionWatcher

public abstract class CollectionWatcher
extends AllocationFreeList.Element<CollectionWatcher>

The abstract base class for CollectionWatchers. Clients sub-class this provide their own implementations.

Each CollectionWatcher instance may be registered at most once with GC.registerCollectionWatcher(CollectionWatcher). If there is state that could be reused between CollectionWatchers (e.g., the list of loaded classes), allocate it outside of the CollectionWatcher instance and share it between CollectionWatcher instances.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CollectionWatcher() Constructor for subclasses.

Method Summary

Modifier and Type	Method and Description
abstract void	afterCollection() Called after a collection.
abstract void	beforeCollection() Called before a collection.
void	report() Called when the collection is over.

Methods inherited from class com.oracle.svm.core.heap.AllocationFreeList.Element

getHasBeenOnList, getNextElement, getNextObject, removeElement, testingBackDoorGetNextElement, testingBackDoorIsEnabled

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CollectionWatcher

protected CollectionWatcher()

Constructor for subclasses.

Method Detail

beforeCollection

public abstract void beforeCollection()

Called before a collection.

A collection has been requested, so space is not available when this method is called. This method runs inside the collection VMOperation, so taking locks is not allowed.

afterCollection

public abstract void afterCollection()

Called after a collection.

A collection has finished, but allocation is still disallowed. This method is run inside the collection VMOperation, so taking locks is not allowed.

report

public void report()

Called when the collection is over.

Allocation is allowed, but too much allocation may cause another collection. Collections may be caused by VMOperations, in which case this method will be called inside that enclosing VMOperation, so taking locks is not allowed. More than one thread may end up calling this method for the same collection.

The default implementation is to do nothing.