org.mmtk.policy.immix

Class ImmixSpace

java.lang.Object

org.mmtk.policy.Space

org.mmtk.policy.immix.ImmixSpace

public final class ImmixSpace
extends Space

Each instance of this class corresponds to one immix space. Each of the instance methods of this class may be called by any thread (i.e. synchronization must be explicit in any instance or class method). This contrasts with the SquishLocal, where instances correspond to *plan* instances and therefore to kernel threads. Thus unlike this class, synchronization is not necessary in the instance methods of SquishLocal.

Nested Class Summary

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

Space.SpaceVisitor

Field Summary

Fields

Modifier and Type	Field and Description
private Address	allocBlockCursor
private Address	allocBlockSentinel
private ChunkList	chunkMap
private Defrag	defrag
private boolean	exhaustedReusableSpace
private Lock	gcLock
private boolean	inCollection
(package private) byte	lineMarkState
private int	linesConsumed
private byte	lineUnavailState
private byte	markState
private Lock	mutatorLock
private static short	reusableMarkStateThreshold

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
ImmixSpace(String name, boolean zeroed, VMRequest vmRequest) The caller specifies the region of virtual memory to be used for this space.
ImmixSpace(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
Address	acquireReusableBlocks()
boolean	copyNurseryIsLive(ObjectReference object) Test the liveness of an object during copying sticky mark bits collection
void	decideWhetherToDefrag(boolean emergencyCollection, boolean collectWholeHeap, int collectionAttempt, boolean userTriggeredCollection) Determine the collection kind.
int	defragHeadroomPages() Return the amount of headroom required to allow defrag, so this can be included in a collection reserve.
boolean	fastIsLive(ObjectReference object) Test the liveness of an object during defragmentation
ObjectReference	fastTraceObject(TransitiveClosure trace, ObjectReference object) Trace a reference to an object in the context of a non-moving collection.
(package private) int	getAvailableLines(int[] spillAvailHistogram) Establish the number of recyclable lines lines available for allocation during defragmentation, populating the spillAvailHistogram, which buckets available lines according to the number of holes on the block on which the available lines reside.
(package private) ChunkList	getChunkMap()
(package private) Defrag	getDefrag()
int	getNextAvailableLine(Address baseLineAvailAddress, int line)
int	getNextUnavailableLine(Address baseLineAvailAddress, int line)
int	getPagesAllocated() Return the number of pages allocated since the last collection
static short	getReusuableMarkStateThreshold(boolean forDefrag) Return the reusable mark state threshold, which determines how eagerly lines should be recycled (by default these values are set so that all lines are recycled).
Address	getSpace(boolean hot, boolean copy, int lineUseCount) Return a pointer to a set of new usable blocks, or null if none are available.
private int	getUsableLinesInRegion(Address start, Address end, int[] spillAvailHistogram) Return the number of lines usable for allocation during defragmentation in the address range specified by start and end.
void	growSpace(Address start, Extent bytes, boolean newChunk) This hook is called by page resources each time a space grows.
boolean	inImmixCollection() Return true if this space is currently being collected.
boolean	inImmixDefragCollection() Return true if this space is currently being defraged.
void	initializeDefrag()
boolean	isDefragSource(Address address)
private boolean	isDefragSource(ObjectReference object)
boolean	isLive(ObjectReference object) Generic test of the liveness of an object
static boolean	isRecycleAllocChunkAligned(Address ptr)
private void	lock() Acquire the appropriate lock depending on whether the context is GC or mutator.
void	markLines(ObjectReference object) Mark the line/s associated with a given object.
ObjectReference	nurseryTraceObject(TransitiveClosure trace, ObjectReference object, int allocator) Trace a reference to an object during a nursery collection for a sticky mark bits implementation of immix.
void	postAlloc(ObjectReference object, int bytes) Perform any required post allocation initialization
void	postCopy(ObjectReference object, int bytes, boolean majorGC) Perform any required post copy (i.e. in-GC allocation) initialization.
void	prepare(boolean majorGC) Prepare for a new collection increment.
void	release(Address block) Release a block.
boolean	release(boolean majorGC) A new collection increment has completed.
int	releaseDiscontiguousChunks(Address chunk) Release one or more contiguous chunks associated with a discontiguous space.
ObjectReference	traceObject(TransitiveClosure trace, ObjectReference object) Trace a reference to an object.
ObjectReference	traceObject(TransitiveClosure trace, ObjectReference object, int allocator) Trace a reference to an object.
private ObjectReference	traceObjectWithOpportunisticCopy(TransitiveClosure trace, ObjectReference object, int allocator, boolean nurseryCollection) Trace a reference to an object, forwarding the object if appropriate If the object is not already marked, mark the object and enqueue it for subsequent processing.
private void	traceObjectWithoutMoving(TransitiveClosure trace, ObjectReference object) Trace a reference to an object in the context of a non-moving collection.
private void	unlock() Release the appropriate lock depending on whether the context is GC or mutator.
boolean	willNotMoveThisGC(Address address)
boolean	willNotMoveThisGC(ObjectReference object)
boolean	willNotMoveThisNurseryGC(ObjectReference object)

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, isImmortal, isImmortal, isInSpace, isInSpace, isMappedAddress, isMappedObject, isMovable, isMovable, isReachable, printUsageMB, printUsagePages, printVMMap, releaseAllChunks, 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

reusableMarkStateThreshold

private static short reusableMarkStateThreshold

markState

private byte markState

lineMarkState

byte lineMarkState

lineUnavailState

private byte lineUnavailState

inCollection

private boolean inCollection

linesConsumed

private int linesConsumed

mutatorLock

private final Lock mutatorLock

gcLock

private final Lock gcLock

allocBlockCursor

private Address allocBlockCursor

allocBlockSentinel

private Address allocBlockSentinel

exhaustedReusableSpace

private boolean exhaustedReusableSpace

chunkMap

private final ChunkList chunkMap

defrag

private final Defrag defrag

Constructor Detail

ImmixSpace

public ImmixSpace(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 - The virtual memory request

ImmixSpace

public ImmixSpace(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 - The virtual memory request

Method Detail

initializeDefrag

public void initializeDefrag()

prepare

public void prepare(boolean majorGC)

Prepare for a new collection increment.

Parameters:

majorGC - whether the collection will be a full heap collection

release

public boolean release(boolean majorGC)

A new collection increment has completed. Release global resources.

Parameters:

majorGC - whether the collection was a full heap collection

Returns:

whether defragmentation occurred

decideWhetherToDefrag

public void decideWhetherToDefrag(boolean emergencyCollection,
                                  boolean collectWholeHeap,
                                  int collectionAttempt,
                                  boolean userTriggeredCollection)

Determine the collection kind.

Parameters:

emergencyCollection - Is this collection an emergency (last did not yield enough)?

collectWholeHeap - Is this a whole heap collection?

collectionAttempt - Which attempt is this to collect?

userTriggeredCollection - Was this collection requested by the user?

defragHeadroomPages

public int defragHeadroomPages()

Return the amount of headroom required to allow defrag, so this can be included in a collection reserve.

Returns:

The number of pages.

inImmixCollection

public boolean inImmixCollection()

Return true if this space is currently being collected.

Returns:

true if this space is currently being collected.

inImmixDefragCollection

public boolean inImmixDefragCollection()

Return true if this space is currently being defraged.

Returns:

true if this space is currently being defraged.

getPagesAllocated

public int getPagesAllocated()

Return the number of pages allocated since the last collection

Returns:

The number of pages allocated since the last collection

getReusuableMarkStateThreshold

public static short getReusuableMarkStateThreshold(boolean forDefrag)

Return the reusable mark state threshold, which determines how eagerly lines should be recycled (by default these values are set so that all lines are recycled).

Parameters:

forDefrag - The query is the context of a defragmenting collection

Returns:

The reusable mark state threshold

getSpace

public Address getSpace(boolean hot,
                        boolean copy,
                        int lineUseCount)

Return a pointer to a set of new usable blocks, or null if none are available. Use different block selection heuristics depending on whether the allocation request is "hot" or "cold".

Parameters:

hot - True if the requesting context is for hot allocations (used for allocations from high allocation volume sites).

copy - TODO needs documentation

lineUseCount - TODO needs documentation

Returns:

the pointer into the alloc table containing usable blocks, null if no usable blocks are available

growSpace

public void growSpace(Address start,
                      Extent bytes,
                      boolean newChunk)

Description copied from class: Space

This hook is called by page resources each time a space grows. The space may tap into the hook to monitor heap growth. The call is made from within the page resources' critical region, immediately before yielding the lock.

Overrides:

growSpace in class Space

Parameters:

start - The start of the newly allocated space

bytes - The size of the newly allocated space

newChunk - true if the new space encroached upon or started a new chunk or chunks.

acquireReusableBlocks

public Address acquireReusableBlocks()

release

public void release(Address block)

Release a block. A block is free, so call the underlying page allocator to release the associated storage.

Specified by:

release in class Space

Parameters:

block - The address of the block to be released

releaseDiscontiguousChunks

public int releaseDiscontiguousChunks(Address chunk)

Release one or more contiguous chunks associated with a discontiguous space.

This hook is called by the page level allocators whenever a complete discontiguous chunk is released.

Overrides:

releaseDiscontiguousChunks in class Space

Parameters:

chunk - The address of the start of the contiguous chunk or chunks

Returns:

The number of chunks freed

postAlloc

public void postAlloc(ObjectReference object,
                      int bytes)

Perform any required post allocation initialization

Parameters:

object - the object ref to the storage to be initialized

bytes - size of the allocated object in bytes

postCopy

public void postCopy(ObjectReference object,
                     int bytes,
                     boolean majorGC)

Perform any required post copy (i.e. in-GC allocation) initialization. This is relevant (for example) when Squish is used as the mature space in a copying GC.

Parameters:

object - the object ref to the storage to be initialized

bytes - size of the copied object in bytes

majorGC - Is this copy happening during a major gc?

traceObject

public ObjectReference traceObject(TransitiveClosure trace,
                                   ObjectReference object,
                                   int allocator)

Trace a reference to an object. If the object header is not already marked, mark the object and enqueue it for subsequent processing.

Parameters:

trace - The trace performing the transitive closure

object - The object to be traced.

allocator - The allocator to which any copying should be directed

Returns:

The object, which may have been moved.

fastTraceObject

public ObjectReference fastTraceObject(TransitiveClosure trace,
                                       ObjectReference object)

Trace a reference to an object in the context of a non-moving collection. This call is optimized for the simpler non-moving case.

Parameters:

trace - The trace performing the transitive closure

object - The object to be traced.

Returns:

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

nurseryTraceObject

public ObjectReference nurseryTraceObject(TransitiveClosure trace,
                                          ObjectReference object,
                                          int allocator)

Trace a reference to an object during a nursery collection for a sticky mark bits implementation of immix. If the object header is not already marked, mark the object and enqueue it for subsequent processing.

Parameters:

trace - The trace performing the transitive closure

object - The object to be traced.

allocator - The allocator to which any copying should be directed

Returns:

Either the object or a forwarded object, depending on the policy in place.

traceObject

public ObjectReference traceObject(TransitiveClosure trace,
                                   ObjectReference object)

Trace a reference to an object. This interface is not supported by immix, since we require the allocator to be identified except for the special case of the fast trace.

Specified by:

traceObject in class Space

Parameters:

trace - The trace performing the transitive closure

object - The object to be traced.

Returns:

null and fail.

traceObjectWithoutMoving

private void traceObjectWithoutMoving(TransitiveClosure trace,
                                      ObjectReference object)

Trace a reference to an object in the context of a non-moving collection. This call is optimized for the simpler non-moving case.

Parameters:

trace - The trace performing the transitive closure

object - The object to be traced.

traceObjectWithOpportunisticCopy

private ObjectReference traceObjectWithOpportunisticCopy(TransitiveClosure trace,
                                                         ObjectReference object,
                                                         int allocator,
                                                         boolean nurseryCollection)

Trace a reference to an object, forwarding the object if appropriate If the object is not already marked, mark the object and enqueue it for subsequent processing.

Parameters:

trace - The trace performing the transitive closure

object - The object to be traced.

allocator - The allocator to which any copying should be directed

nurseryCollection - whether the current collection is a nursery collection

Returns:

Either the object or a forwarded object, if it was forwarded.

markLines

public void markLines(ObjectReference object)

Mark the line/s associated with a given object. This is distinct from the above tracing code because line marks are stored separately from the object headers (thus both must be set), and also because we found empirically that it was more efficient to perform the line mark of the object during the scan phase (which occurs after the trace phase), presumably because the latency of the associated memory operations was better hidden in the context of that code

Parameters:

object - The object which is live and for which the associated lines must be marked.

getNextUnavailableLine

public int getNextUnavailableLine(Address baseLineAvailAddress,
                                  int line)

getNextAvailableLine

public int getNextAvailableLine(Address baseLineAvailAddress,
                                int line)

getAvailableLines

int getAvailableLines(int[] spillAvailHistogram)

Establish the number of recyclable lines lines available for allocation during defragmentation, populating the spillAvailHistogram, which buckets available lines according to the number of holes on the block on which the available lines reside.

Parameters:

spillAvailHistogram - A histogram of availability to be populated

Returns:

The number of available recyclable lines

getUsableLinesInRegion

private int getUsableLinesInRegion(Address start,
                                   Address end,
                                   int[] spillAvailHistogram)

Return the number of lines usable for allocation during defragmentation in the address range specified by start and end. Populate a histogram to indicate where the usable lines reside as a function of block hole count.

Parameters:

start - The start of the region to be checked for availability

end - The end of the region to be checked for availability

spillAvailHistogram - The histogram which will be populated

Returns:

The number of usable lines

isLive

public boolean isLive(ObjectReference object)

Generic test of the liveness of an object

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)

copyNurseryIsLive

public boolean copyNurseryIsLive(ObjectReference object)

Test the liveness of an object during copying sticky mark bits collection

Parameters:

object - The object in question

Returns:

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

fastIsLive

public boolean fastIsLive(ObjectReference object)

Test the liveness of an object during defragmentation

Parameters:

object - The object in question

Returns:

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

willNotMoveThisGC

public boolean willNotMoveThisGC(ObjectReference object)

willNotMoveThisNurseryGC

public boolean willNotMoveThisNurseryGC(ObjectReference object)

isDefragSource

private boolean isDefragSource(ObjectReference object)

willNotMoveThisGC

public boolean willNotMoveThisGC(Address address)

isDefragSource

public boolean isDefragSource(Address address)

lock

private void lock()

Acquire the appropriate lock depending on whether the context is GC or mutator.

unlock

private void unlock()

Release the appropriate lock depending on whether the context is GC or mutator.

isRecycleAllocChunkAligned

public static boolean isRecycleAllocChunkAligned(Address ptr)

Parameters:

ptr - the block's address

Returns:

whether the block has the ImmixConstants.RECYCLE_ALLOC_CHUNK_MASK flag

getChunkMap

ChunkList getChunkMap()

getDefrag

Defrag getDefrag()