org.mmtk.policy

Class ExplicitLargeObjectSpace

java.lang.Object

org.mmtk.policy.Space

org.mmtk.policy.BaseLargeObjectSpace

org.mmtk.policy.ExplicitLargeObjectSpace

public final class ExplicitLargeObjectSpace
extends BaseLargeObjectSpace

Each instance of this class corresponds to one explicitly managed large object space.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ExplicitLargeObjectSpace.Sweeper A callback used to perform sweeping of the large object space.

Nested classes/interfaces inherited from class org.mmtk.policy.Space

Space.SpaceVisitor

Field Summary

Fields

Modifier and Type	Field and Description
private DoublyLinkedList	cells

Fields inherited from class org.mmtk.policy.BaseLargeObjectSpace

PAGE_MASK

Fields inherited from class org.mmtk.policy.Space

AVAILABLE_BYTES, AVAILABLE_END, AVAILABLE_PAGES, AVAILABLE_START, BYTES_IN_CHUNK, contiguous, descriptor, extent, headDiscontiguousRegion, HEAP_END, HEAP_START, immortal, LOG_ADDRESS_SPACE, LOG_BYTES_IN_CHUNK, MAX_CHUNKS, MAX_SPACES, movable, PAGES_IN_CHUNK, pr, start, zeroed

Constructor Summary

Constructors

Constructor and Description
ExplicitLargeObjectSpace(String name, boolean zeroed, VMRequest vmRequest) The caller specifies the region of virtual memory to be used for this space.
ExplicitLargeObjectSpace(String name, VMRequest vmRequest) The caller specifies the region of virtual memory to be used for this space.

Method Summary

Modifier and Type	Method and Description
protected int	cellHeaderSize() Return the size of the per-cell header for cells of a given class size.
void	free(ObjectReference object) Free an object
void	initializeHeader(ObjectReference object, boolean alloc) Perform any required initialization of the GC portion of the header.
boolean	isLive(ObjectReference object) Is the object in this space alive?
void	prepare() Prepare for a new collection increment.
void	release() A new collection increment has completed.
void	release(Address first) Release a group of pages that were allocated together.
protected int	superPageHeaderSize() Return the size of the per-superpage header required by this system.
void	sweep(ExplicitLargeObjectSpace.Sweeper sweeper) Sweep through all the objects in this space.
ObjectReference	traceObject(TransitiveClosure trace, ObjectReference object) Trace a reference to an object under a mark sweep collection policy.

Methods inherited from class org.mmtk.policy.BaseLargeObjectSpace

free, getHeaderSize, getSize, getSuperPage

Methods inherited from class org.mmtk.policy.Space

acquire, availablePhysicalPages, chunkAlign, chunkAlign, committedPages, cumulativeCommittedPages, eagerlyMmapMMTkContiguousSpaces, eagerlyMmapMMTkDiscontiguousSpaces, eagerlyMmapMMTkSpaces, getDescriptor, getDiscontigEnd, getDiscontigStart, getExtent, getFracAvailable, getHeadDiscontiguousRegion, getIndex, getName, getSpaceCount, getSpaceForAddress, getSpaceForObject, getSpaces, getStart, growDiscontiguousSpace, growSpace, isImmortal, isImmortal, isInSpace, isInSpace, isMappedAddress, isMappedObject, isMovable, isMovable, isReachable, printUsageMB, printUsagePages, printVMMap, releaseAllChunks, releaseDiscontiguousChunks, requiredChunks, reservedPages, setZeroingApproach, skipConcurrentZeroing, triggerConcurrentZeroing, visitSpaces

Methods inherited from class java.lang.Object

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

Field Detail

cells

private final DoublyLinkedList cells

Constructor Detail

ExplicitLargeObjectSpace

public ExplicitLargeObjectSpace(String name,
                                VMRequest vmRequest)

The caller specifies the region of virtual memory to be used for this space. If this region conflicts with an existing space, then the constructor will fail.

Parameters:

name - The name of this space (used when printing error messages etc)

vmRequest - An object describing the virtual memory requested.

ExplicitLargeObjectSpace

public ExplicitLargeObjectSpace(String name,
                                boolean zeroed,
                                VMRequest vmRequest)

The caller specifies the region of virtual memory to be used for this space. If this region conflicts with an existing space, then the constructor will fail.

Parameters:

name - The name of this space (used when printing error messages etc)

zeroed - if true, allocations return zeroed memory.

vmRequest - An object describing the virtual memory requested.

Method Detail

prepare

public void prepare()

Prepare for a new collection increment.

release

public void release()

A new collection increment has completed.

release

public void release(Address first)

Release a group of pages that were allocated together.

Specified by:

release in class Space

Parameters:

first - The first page in the group of pages that were allocated together.

initializeHeader

public void initializeHeader(ObjectReference object,
                             boolean alloc)

Perform any required initialization of the GC portion of the header.

Parameters:

object - the object ref to the storage to be initialized

alloc - is this initialization occuring due to (initial) allocation (true) or due to copying (false)?

traceObject

public ObjectReference traceObject(TransitiveClosure trace,
                                   ObjectReference object)

Trace a reference to an object under a mark sweep collection policy. If the object header is not already marked, mark the object in either the bitmap or by moving it off the treadmill, and enqueue the object for subsequent processing. The object is marked as (an atomic) side-effect of checking whether already marked.

Specified by:

traceObject in class Space

Parameters:

trace - The trace being conducted.

object - The object to be traced.

Returns:

The object (there is no object forwarding in this collector, so we always return the same object: this could be a void method but for compliance to a more general interface).

isLive

public boolean isLive(ObjectReference object)

Description copied from class: Space

Is the object in this space alive?

Specified by:

isLive in class Space

Parameters:

object - The object in question

Returns:

true if this object is known to be live (i.e. it is marked)

superPageHeaderSize

protected int superPageHeaderSize()

Description copied from class: BaseLargeObjectSpace

Return the size of the per-superpage header required by this system. In this case it is just the underlying superpage header size.

Specified by:

superPageHeaderSize in class BaseLargeObjectSpace

Returns:

The size of the per-superpage header required by this system.

cellHeaderSize

protected int cellHeaderSize()

Description copied from class: BaseLargeObjectSpace

Return the size of the per-cell header for cells of a given class size.

Specified by:

cellHeaderSize in class BaseLargeObjectSpace

Returns:

The size of the per-cell header for cells of a given class size.

sweep

public void sweep(ExplicitLargeObjectSpace.Sweeper sweeper)

Sweep through all the objects in this space.

Parameters:

sweeper - The sweeper callback to use.

free

public void free(ObjectReference object)

Free an object

Parameters:

object - The object to be freed.