org.mmtk.plan.generational

Class Gen

java.lang.Object

org.mmtk.plan.Plan

org.mmtk.plan.Simple

org.mmtk.plan.StopTheWorld

org.mmtk.plan.generational.Gen

Direct Known Subclasses:

GenCopy, GenImmix, GenMS

public abstract class Gen
extends StopTheWorld

This abstract class implements the core functionality of generic two-generation copying collectors. Nursery collections occur when either the heap is full or the nursery is full. The nursery size is determined by an optional command line argument. If undefined, the nursery size is "infinite", so nursery collections only occur when the heap is full (this is known as a flexible-sized nursery collector). Thus both fixed and flexible nursery sizes are supported. Full heap collections occur when the nursery size has dropped to a statically defined threshold, NURSERY_THRESHOLD

See also Plan.java for general comments on local vs global plan classes.

Field Summary

Fields

Modifier and Type	Field and Description
static int	ALLOC_MATURE
static int	ALLOC_MATURE_MAJORGC
static int	ALLOC_MATURE_MINORGC
static int	ALLOC_NURSERY
SharedDeque	arrayRemsetPool
protected static BooleanCounter	fullHeap
private static Timer	fullHeapTime
boolean	gcFullHeap
static boolean	IGNORE_REMSETS
protected static float	MATURE_FRACTION
SharedDeque	modbufPool
boolean	nextGCFullHeap
static int	NURSERY
private static Address	NURSERY_START
protected static float	NURSERY_VM_FRACTION Fraction of available virtual memory to give to the nursery (if contiguous)
static SizeCounter	nurseryCons
static SizeCounter	nurseryMark
static CopySpace	nurserySpace
Trace	nurseryTrace
SharedDeque	remsetPool
static int	SCAN_MATURE
static int	SCAN_NURSERY
protected static float	SURVIVAL_ESTIMATE
(package private) static boolean	USE_DISCONTIGUOUS_NURSERY Switch between a contiguous and discontiguous nursery (experimental)
static boolean	USE_NON_HEAP_OBJECT_REFERENCE_WRITE_BARRIER
static boolean	USE_OBJECT_BARRIER
static boolean	USE_OBJECT_BARRIER_FOR_AASTORE
static boolean	USE_OBJECT_BARRIER_FOR_PUTFIELD
private static VMRequest	vmRequest
protected static EventCounter	wbFast
protected static EventCounter	wbSlow
private static float	WORST_CASE_COPY_EXPANSION

Fields inherited from class org.mmtk.plan.StopTheWorld

postSanityPhase, preSanityPhase

Fields inherited from class org.mmtk.plan.Simple

CLOSURE, collection, collectionAttempt, COMPLETE, completeClosurePhase, FINALIZABLE, finishPhase, FORWARD, FORWARD_FINALIZABLE, FORWARD_REFS, forwardPhase, INITIATE, initPhase, PHANTOM_REFS, POST_SANITY_PLACEHOLDER, PRE_SANITY_PLACEHOLDER, PREPARE, PREPARE_STACKS, prepareStacks, refTypeClosurePhase, RELEASE, rootClosurePhase, ROOTS, SANITY_BUILD_TABLE, SANITY_CHECK_TABLE, SANITY_COPY_ROOTS, SANITY_PREPARE, SANITY_RELEASE, SANITY_ROOTS, SANITY_SET_POSTGC, SANITY_SET_PREGC, sanityBuildPhase, sanityCheckPhase, SET_COLLECTION_KIND, SOFT_REFS, STACK_ROOTS, WEAK_REFS, WEAK_TRACK_REFS

Fields inherited from class org.mmtk.plan.Plan

ALLOC_CODE, ALLOC_COLD_CODE, ALLOC_DEFAULT, ALLOC_GCSPY, ALLOC_HOT_CODE, ALLOC_IMMORTAL, ALLOC_LARGE_CODE, ALLOC_LOS, ALLOC_NON_MOVING, ALLOC_NON_REFERENCE, ALLOC_PRIMITIVE_LOS, ALLOC_STACK, allocationSiteCount, ALLOCATORS, concurrentWorkers, controlCollectorContext, DEFAULT_MAX_NURSERY, DEFAULT_MIN_NURSERY, DEFAULT_SITE, defaultCollectorContext, emergencyCollection, GATHER_WRITE_BARRIER_STATS, GC_PREPARE, GC_PROPER, IMMORTAL, immortalSpace, insideHarness, internalTriggeredCollection, LARGE_CODE, largeCodeSpace, lastInternalTriggeredCollection, LOS, loSpace, MAX_NON_LOS_COPY_BYTES, MAX_NON_LOS_DEFAULT_ALLOC_BYTES, MAX_NON_LOS_NONMOVING_ALLOC_BYTES, META, metaDataSpace, NEEDS_LOG_BIT_IN_HEADER, NON_MOVING, NON_PARTICIPANT, nonMovingSpace, NOT_IN_GC, parallelWorkers, pretenureThreshold, SANITY, sanityChecker, sanitySpace, SCAN_BOOT_IMAGE, SMALL_CODE, smallCodeSpace, stacksPrepared, totalTime, USE_CODE_SPACE, userTriggeredCollection, VM_SPACE, vmSpace

Constructor Summary

Constructors

Constructor and Description
Gen()

Method Summary

Modifier and Type	Method and Description
protected abstract Space	activeMatureSpace() Accessor method to allow the generic generational code in Gen.java to access the mature space.
void	collectionPhase(short phaseId) Perform a (global) collection phase.
boolean	collectionRequired(boolean spaceFull, Space space) This method controls the triggering of a GC.
protected boolean	copyMature()
void	forceFullHeapCollection() Force the next collection to be full heap.
void	fullyBooted()
int	getCollectionReserve() Return the number of pages reserved for collection.
abstract int	getMaturePhysicalPagesAvail() Return the number of pages available for allocation into the mature space.
int	getPagesAvail() Return the number of pages available for allocation, assuming all future allocation is to the nursery.
int	getPagesUsed() Return the number of pages reserved for use given the pending allocation.
(package private) static boolean	inNursery(Address addr) Return true if the address resides within the nursery
(package private) static boolean	inNursery(ObjectReference obj) Return true if the object resides within the nursery
boolean	isCurrentGCNursery()
boolean	lastCollectionFullHeap()
void	printPreStats() Print pre-collection statistics.
protected void	registerSpecializedMethods() Registers specialized methods.
protected boolean	requiresFullHeapCollection() Determine if this GC should be a full heap collection.
int	sanityExpectedRC(ObjectReference object, int sanityRootRC) Return the expected reference count.
boolean	traceFullHeap()
private boolean	virtualMemoryExhausted() Independent of how many pages remain in the page budget (a function of heap size), we must ensure we never exhaust virtual memory.
boolean	willNeverMove(ObjectReference object) Can this object ever move.

Methods inherited from class org.mmtk.plan.StopTheWorld

processOptions

Methods inherited from class org.mmtk.plan.Simple

replacePhase, replacePlaceholderPhase, switchNurseryZeroingApproach

Methods inherited from class org.mmtk.plan.Plan

availableMemory, bootTimeWriteBarrier, concurrentCollectionRequired, determineThreadCount, enableAllocation, enableCollection, freeMemory, gcInProgress, gcInProgressProper, getAllocationSite, getPagesReserved, getSpecializedScanClass, getTotalPages, handleUserCollectionRequest, harnessBegin, harnessEnd, insertPhaseAfter, isEmergencyCollection, isInitialized, isInternalTriggeredCollection, isUserTriggeredCollection, lastCollectionWasExhaustive, loadObjectReference, logPoll, notifyExit, poll, preCollectorSpawn, printDetailedTiming, printPostStats, printUsedPages, reservedMemory, resetCollectionTrigger, sanityLinearScan, setBuildTimeGCByte, setGCStatus, spawnCollectorThreads, stacksPrepared, startGCspyServer, storeObjectReference, stressTestGCRequired, totalMemory, triggerInternalCollectionRequest, usedMemory

Methods inherited from class java.lang.Object

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

Field Detail

SURVIVAL_ESTIMATE

protected static final float SURVIVAL_ESTIMATE

See Also:

Constant Field Values

MATURE_FRACTION

protected static final float MATURE_FRACTION

See Also:

Constant Field Values

WORST_CASE_COPY_EXPANSION

private static final float WORST_CASE_COPY_EXPANSION

See Also:

Constant Field Values

IGNORE_REMSETS

public static final boolean IGNORE_REMSETS

See Also:

Constant Field Values

USE_NON_HEAP_OBJECT_REFERENCE_WRITE_BARRIER

public static final boolean USE_NON_HEAP_OBJECT_REFERENCE_WRITE_BARRIER

See Also:

Constant Field Values

USE_OBJECT_BARRIER_FOR_AASTORE

public static final boolean USE_OBJECT_BARRIER_FOR_AASTORE

See Also:

Constant Field Values

USE_OBJECT_BARRIER_FOR_PUTFIELD

public static final boolean USE_OBJECT_BARRIER_FOR_PUTFIELD

See Also:

Constant Field Values

USE_OBJECT_BARRIER

public static final boolean USE_OBJECT_BARRIER

See Also:

Constant Field Values

NURSERY_VM_FRACTION

protected static final float NURSERY_VM_FRACTION

Fraction of available virtual memory to give to the nursery (if contiguous)

See Also:

Constant Field Values

USE_DISCONTIGUOUS_NURSERY

static final boolean USE_DISCONTIGUOUS_NURSERY

Switch between a contiguous and discontiguous nursery (experimental)

See Also:

Constant Field Values

ALLOC_NURSERY

public static final int ALLOC_NURSERY

See Also:

Constant Field Values

ALLOC_MATURE

public static final int ALLOC_MATURE

See Also:

Constant Field Values

ALLOC_MATURE_MINORGC

public static final int ALLOC_MATURE_MINORGC

See Also:

Constant Field Values

ALLOC_MATURE_MAJORGC

public static final int ALLOC_MATURE_MAJORGC

See Also:

Constant Field Values

SCAN_NURSERY

public static final int SCAN_NURSERY

See Also:

Constant Field Values

SCAN_MATURE

public static final int SCAN_MATURE

See Also:

Constant Field Values

fullHeap

protected static final BooleanCounter fullHeap

fullHeapTime

private static final Timer fullHeapTime

wbFast

protected static final EventCounter wbFast

wbSlow

protected static final EventCounter wbSlow

nurseryMark

public static final SizeCounter nurseryMark

nurseryCons

public static final SizeCounter nurseryCons

vmRequest

private static final VMRequest vmRequest

nurserySpace

public static final CopySpace nurserySpace

NURSERY

public static final int NURSERY

NURSERY_START

private static final Address NURSERY_START

gcFullHeap

public boolean gcFullHeap

nextGCFullHeap

public boolean nextGCFullHeap

nurseryTrace

public final Trace nurseryTrace

modbufPool

public final SharedDeque modbufPool

remsetPool

public final SharedDeque remsetPool

arrayRemsetPool

public final SharedDeque arrayRemsetPool

Constructor Detail

Gen

public Gen()

Method Detail

forceFullHeapCollection

public void forceFullHeapCollection()

Force the next collection to be full heap.

Overrides:

forceFullHeapCollection in class Plan

collectionPhase

public void collectionPhase(short phaseId)

Description copied from class: Simple

Perform a (global) collection phase.

Overrides:

collectionPhase in class Simple

Parameters:

phaseId - The unique id of the phase to perform.

collectionRequired

public final boolean collectionRequired(boolean spaceFull,
                                        Space space)

Description copied from class: Plan

This method controls the triggering of a GC. It is called periodically during allocation. Returns true to trigger a collection.

Overrides:

collectionRequired in class Plan

Parameters:

spaceFull - Space request failed, must recover pages within 'space'.

space - TODO

Returns:

true if a collection is requested by the plan.

requiresFullHeapCollection

protected boolean requiresFullHeapCollection()

Determine if this GC should be a full heap collection.

Returns:

true is this GC should be a full heap collection.

virtualMemoryExhausted

private boolean virtualMemoryExhausted()

Independent of how many pages remain in the page budget (a function of heap size), we must ensure we never exhaust virtual memory. Therefore we must never let the nursery grow to the extent that it can't be copied into the mature space.

Returns:

true if the nursery has grown to the extent that it may not be able to be copied into the mature space.

getPagesUsed

public int getPagesUsed()

Return the number of pages reserved for use given the pending allocation. Simply add the nursery's contribution to that of the superclass.

Overrides:

getPagesUsed in class Plan

Returns:

The number of pages reserved given the pending allocation, excluding space reserved for copying.

getPagesAvail

public int getPagesAvail()

Return the number of pages available for allocation, assuming all future allocation is to the nursery.

Overrides:

getPagesAvail in class Plan

Returns:

The number of pages available for allocation, assuming all future allocation is to the nursery.

getCollectionReserve

public int getCollectionReserve()

Return the number of pages reserved for collection.

Overrides:

getCollectionReserve in class Plan

Returns:

The number of pages reserved given the pending allocation, including space reserved for collection.

getMaturePhysicalPagesAvail

public abstract int getMaturePhysicalPagesAvail()

Return the number of pages available for allocation into the mature space.

Returns:

The number of pages available for allocation into the mature space.

inNursery

static boolean inNursery(Address addr)

Return true if the address resides within the nursery

Parameters:

addr - The object to be tested

Returns:

true if the address resides within the nursery

inNursery

static boolean inNursery(ObjectReference obj)

Return true if the object resides within the nursery

Parameters:

obj - The object to be tested

Returns:

true if the object resides within the nursery

copyMature

protected boolean copyMature()

Returns:

Does the mature space do copying ?

printPreStats

public void printPreStats()

Print pre-collection statistics. In this class we prefix the output indicating whether the collection was full heap or not.

Overrides:

printPreStats in class Plan

activeMatureSpace

protected abstract Space activeMatureSpace()

Accessor method to allow the generic generational code in Gen.java to access the mature space.

Returns:

The mature space, set by each subclass of Gen.

traceFullHeap

public final boolean traceFullHeap()

Returns:

true if we should trace the whole heap during collection. True if we're ignoring remsets or if we're doing a full heap GC.

isCurrentGCNursery

public final boolean isCurrentGCNursery()

Overrides:

isCurrentGCNursery in class Plan

Returns:

Is current GC only collecting objects allocated since last GC.

lastCollectionFullHeap

public final boolean lastCollectionFullHeap()

Overrides:

lastCollectionFullHeap in class Plan

Returns:

Whether last GC is a full GC.

willNeverMove

public boolean willNeverMove(ObjectReference object)

Description copied from class: Plan

Can this object ever move. Used by the VM to make decisions about whether it needs to copy IO buffers etc.

Overrides:

willNeverMove in class Plan

Parameters:

object - The object in question

Returns:

true if it is not possible that the object will ever move.

sanityExpectedRC

public int sanityExpectedRC(ObjectReference object,
                            int sanityRootRC)

Description copied from class: Plan

Return the expected reference count. For non-reference counting collectors this becomes a true/false relationship.

Overrides:

sanityExpectedRC in class Plan

Parameters:

object - The object to check.

sanityRootRC - The number of root references to the object.

Returns:

The expected (root excluded) reference count.

registerSpecializedMethods

protected void registerSpecializedMethods()

Description copied from class: Plan

Registers specialized methods.

Overrides:

registerSpecializedMethods in class Plan

fullyBooted

public void fullyBooted()

Overrides:

fullyBooted in class Plan