com.oracle.svm.core.genscavenge

Class HeapChunk

java.lang.Object

com.oracle.svm.core.genscavenge.HeapChunk

public final class HeapChunk
extends Object

The common structure of the chunks of memory which make up the heap. HeapChunks are aggregated into spaces. A specific "subtype" of chunk should be accessed via its own accessor class, such as AlignedHeapChunk, which provides methods that are specific to the type of chunk and its layout. (Such classes intentionally do not subclass HeapChunk so to not directly expose its methods.)

A HeapChunk is raw memory with a HeapChunk.Header on the beginning that stores bookkeeping information about the HeapChunk. HeapChunks do not have any instance methods: instead they have static methods that take the HeapChunk.Header as a parameter.

HeapChunks maintain offsets of the current allocation point (top) with them, and the limit (end) where Objects can be allocated. Subclasses of HeapChunks can add additional fields as needed.

HeapChunks maintain some fields that would otherwise have to be maintained in per-HeapChunk memory by the Space that contains them. For example, the fields for linking lists of HeapChunks in a Space is kept in each HeapChunk rather than in some storage outside the HeapChunk.

For fields that are maintained as more-specifically-typed offsets by leaf "sub-classes", HeapChunk defines the generic (Pointer) "get" methods, and only the "sub-classes" define "set" methods that store more-specifically-typed Pointers, for type safety.

In addition to the declared fields of a HeapChunk.Header, for example, a subtype keeps a card table for the write barrier, but because they are variable-sized, rather than declaring field in the Header, static methods are used to compute Pointers to those "fields".

HeapChunks are *not* examined for interior Object references by the collector, though the Objects allocated within the HeapChunk are examined by the collector.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	HeapChunk.Header<T extends HeapChunk.Header<T>> The header of a chunk.

Method Summary

Modifier and Type	Method and Description
static org.graalvm.word.Pointer	asPointer(HeapChunk.Header<?> that)
static org.graalvm.word.UnsignedWord	availableObjectMemory(HeapChunk.Header<?> that)
static HeapChunk.Header<?>	getEnclosingHeapChunk(Object obj)
static HeapChunk.Header<?>	getEnclosingHeapChunk(org.graalvm.word.Pointer ptrToObj, org.graalvm.word.UnsignedWord header)
static org.graalvm.word.UnsignedWord	getEndOffset(HeapChunk.Header<?> that)
static org.graalvm.word.Pointer	getEndPointer(HeapChunk.Header<?> that)
static <T extends HeapChunk.Header<T>> T	getNext(HeapChunk.Header<T> that)
static <T extends HeapChunk.Header<T>> T	getPrevious(HeapChunk.Header<T> that)
static Space	getSpace(HeapChunk.Header<?> that)
static org.graalvm.word.UnsignedWord	getTopOffset(HeapChunk.Header<?> that)
static org.graalvm.word.Pointer	getTopPointer(HeapChunk.Header<?> that)
static void	initialize(HeapChunk.Header<?> chunk, org.graalvm.word.Pointer objectsStart, org.graalvm.word.UnsignedWord chunkSize)
static void	setEndOffset(HeapChunk.Header<?> that, org.graalvm.word.UnsignedWord newEnd)
static <T extends HeapChunk.Header<T>> void	setNext(HeapChunk.Header<T> that, T newNext)
static <T extends HeapChunk.Header<T>> void	setPrevious(HeapChunk.Header<T> that, T newPrevious)
static void	setSpace(HeapChunk.Header<?> that, Space newSpace)
static void	setTopPointer(HeapChunk.Header<?> that, org.graalvm.word.Pointer newTop)
static boolean	walkObjectsFrom(HeapChunk.Header<?> that, org.graalvm.word.Pointer offset, ObjectVisitor visitor)
static boolean	walkObjectsFromInline(HeapChunk.Header<?> that, org.graalvm.word.Pointer startOffset, ObjectVisitor visitor)

Methods inherited from class java.lang.Object

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

Method Detail

initialize

public static void initialize(HeapChunk.Header<?> chunk,
                              org.graalvm.word.Pointer objectsStart,
                              org.graalvm.word.UnsignedWord chunkSize)

getTopOffset

public static org.graalvm.word.UnsignedWord getTopOffset(HeapChunk.Header<?> that)

getTopPointer

public static org.graalvm.word.Pointer getTopPointer(HeapChunk.Header<?> that)

setTopPointer

public static void setTopPointer(HeapChunk.Header<?> that,
                                 org.graalvm.word.Pointer newTop)

getEndOffset

public static org.graalvm.word.UnsignedWord getEndOffset(HeapChunk.Header<?> that)

getEndPointer

public static org.graalvm.word.Pointer getEndPointer(HeapChunk.Header<?> that)

setEndOffset

public static void setEndOffset(HeapChunk.Header<?> that,
                                org.graalvm.word.UnsignedWord newEnd)

getSpace

public static Space getSpace(HeapChunk.Header<?> that)

setSpace

public static void setSpace(HeapChunk.Header<?> that,
                            Space newSpace)

getPrevious

public static <T extends HeapChunk.Header<T>> T getPrevious(HeapChunk.Header<T> that)

setPrevious

public static <T extends HeapChunk.Header<T>> void setPrevious(HeapChunk.Header<T> that,
                                                               T newPrevious)

getNext

public static <T extends HeapChunk.Header<T>> T getNext(HeapChunk.Header<T> that)

setNext

public static <T extends HeapChunk.Header<T>> void setNext(HeapChunk.Header<T> that,
                                                           T newNext)

walkObjectsFrom

public static boolean walkObjectsFrom(HeapChunk.Header<?> that,
                                      org.graalvm.word.Pointer offset,
                                      ObjectVisitor visitor)

walkObjectsFromInline

public static boolean walkObjectsFromInline(HeapChunk.Header<?> that,
                                            org.graalvm.word.Pointer startOffset,
                                            ObjectVisitor visitor)

availableObjectMemory

public static org.graalvm.word.UnsignedWord availableObjectMemory(HeapChunk.Header<?> that)

asPointer

public static org.graalvm.word.Pointer asPointer(HeapChunk.Header<?> that)

getEnclosingHeapChunk

public static HeapChunk.Header<?> getEnclosingHeapChunk(Object obj)

getEnclosingHeapChunk

public static HeapChunk.Header<?> getEnclosingHeapChunk(org.graalvm.word.Pointer ptrToObj,
                                                        org.graalvm.word.UnsignedWord header)