com.oracle.svm.core.heap

Class PinnedAllocator

java.lang.Object

com.oracle.svm.core.heap.PinnedAllocator

All Implemented Interfaces:

AutoCloseable

Direct Known Subclasses:

PinnedAllocatorImpl

public abstract class PinnedAllocator
extends Object
implements AutoCloseable

An allocator of pinned objects. The lifecycle of a PinnedAllocator is

• The PinnedAllocator is not itself pinned.
• The PinnedAllocator is opened by calling open(). The separation between creation and opening is to allow a PinnedAllocator to be created (e.g., during native image generation), but not opened until sometime later (e.g., at runtime).
• One or more calls are made to allocatePinnedObject(Class) or allocatePinnedArray(Class, int) to allocate objects (or arrays) that are pinned in memory. Pinned objects will not be moved by the collector, nor will they be collected.
• The PinnedAllocator is closed by calling close() (possibly implicitly in a try-with-resource statement). Only one PinnedAllocator may be open at a time. (This is a convenience for efficiency, not really a requirement of the idea of pinned allocation.). Objects created by the PinnedAllocator continue to be pinned.
• The objects allocated by this PinnedAllocator are unpinned by calling release(). The objects allocated by the PinnedAllocator become unpinned, and subject to collection if they are not reachable.

If a client forgets to call release(), the PinnedAllocator and all the Objects it has allocated will remain reachable, and the Objects it has allocated will remained pinned. Don't do that. Calling release() on an open (that is, not closed) PinnedAllocator closes the PinnedAllocator and then then releases it. TODO: There could be a convenience implementation of this interface that opens the PinnedAllocator when it is created, and releases it when it is closed.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	PinnedAllocator.PinnedAllocationLifecycleError Signals that allocation has failed because of a lifecycle error, i.e., rather than an out-of-memory error.

Constructor Summary

Constructors

Constructor and Description
PinnedAllocator()

Method Summary

Modifier and Type	Method and Description
abstract void	close() Close this PinnedAllocator to further allocation.
Object	newArray(Class<?> componentType, int length) Allocate an array with the given element type.
<T> T	newInstance(Class<T> instanceClass) Allocate an Object of the given class.
abstract PinnedAllocator	open() A PinnedAllocator can not allocate objects until opened.
abstract void	release() Release the Objects allocated by this PinnedAllocator.

Methods inherited from class java.lang.Object

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

Constructor Detail

PinnedAllocator

public PinnedAllocator()

Method Detail

open

public abstract PinnedAllocator open()

A PinnedAllocator can not allocate objects until opened.

newInstance

public final <T> T newInstance(Class<T> instanceClass)

Allocate an Object of the given class. The returned object is initialized with zero, but no constructors are executed. The class parameter must be a compile time constant. This method has the same behavior as Unsafe.allocateInstance(Class).

newArray

public final Object newArray(Class<?> componentType,
                             int length)

Allocate an array with the given element type. The class parameter must be a compile time constant. This method has the same behavior as Array.newInstance(Class, int);

close

public abstract void close()

Close this PinnedAllocator to further allocation.

Specified by:

close in interface AutoCloseable

release

public abstract void release()

Release the Objects allocated by this PinnedAllocator.