org.mmtk.plan.refcount

Class RCBase

java.lang.Object

org.mmtk.plan.Plan

org.mmtk.plan.Simple

org.mmtk.plan.StopTheWorld

org.mmtk.plan.refcount.RCBase

Direct Known Subclasses:

GenRC, RC

public class RCBase
extends StopTheWorld

This class implements the global state of a reference counting collector. See Shahriyar et al for details of and rationale for the optimizations used here (http://dx.doi.org/10.1145/2258996.2259008). See Chapter 4 of Daniel Frampton's PhD thesis for details of and rationale for the cycle collection strategy used by this collector.

Field Summary

Fields

Modifier and Type	Field and Description
Trace	backupTrace
static short	BT_CLOSURE
static boolean	BUILD_FOR_GENRC True if we are building for generational RC
static boolean	CC_BACKUP_TRACE Use backup tracing for cycle collection (currently the only option)
static boolean	CC_ENABLED Is cycle collection enabled?
static boolean	ccForceFull Force full cycle collection at each GC?
SharedDeque	decPool
short	genRCCollection
protected static short	genRCCollectionPhase
protected static short	genRCRootClosurePhase
private BTFreeLargeObjectSweeper	loFreeSweeper
SharedDeque	modPool
SharedDeque	newRootPool
SharedDeque	oldRootPool
static boolean	performCycleCollection
static short	PROCESS_DECBUFFER
static short	PROCESS_MODBUFFER
static short	PROCESS_NEWROOTBUFFER
static short	PROCESS_OLDROOTBUFFER
static ExplicitLargeObjectSpace	rcloSpace
static ExplicitFreeListSpace	rcSpace
private BTSweeper	rcSweeper
static int	REF_COUNT
static int	REF_COUNT_LOS
short	refCountCollection This is the phase that is executed to perform a collection.
protected static short	refCountCollectionPhase Reference counting specific collection steps.
protected static short	refCountRootClosurePhase Perform the initial determination of liveness from the roots.
Trace	rootTrace

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
RCBase() Constructor

Method Summary

Modifier and Type	Method and Description
void	collectionPhase(short phaseId) Perform a (global) collection phase.
int	getPagesUsed() Return the number of pages reserved for use given the pending allocation.
static boolean	isRCObject(ObjectReference object)
boolean	lastCollectionFullHeap()
void	processOptions() The processOptions method is called by the runtime immediately after command-line arguments are available.
protected void	registerSpecializedMethods() Registers specialized methods.
int	sanityExpectedRC(ObjectReference object, int sanityRootRC) Return the expected reference count.
void	sanityLinearScan(LinearScan scan) Perform a linear scan across all objects in the heap to check for leaks.
byte	setBuildTimeGCByte(Address object, ObjectReference typeRef, int size) Performs any required initialization of the GC portion of the header.

Methods inherited from class org.mmtk.plan.Simple

replacePhase, replacePlaceholderPhase, switchNurseryZeroingApproach

Methods inherited from class org.mmtk.plan.Plan

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

Methods inherited from class java.lang.Object

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

Field Detail

PROCESS_OLDROOTBUFFER

public static final short PROCESS_OLDROOTBUFFER

PROCESS_NEWROOTBUFFER

public static final short PROCESS_NEWROOTBUFFER

PROCESS_MODBUFFER

public static final short PROCESS_MODBUFFER

PROCESS_DECBUFFER

public static final short PROCESS_DECBUFFER

CC_ENABLED

public static final boolean CC_ENABLED

Is cycle collection enabled?

See Also:

Constant Field Values

ccForceFull

public static boolean ccForceFull

Force full cycle collection at each GC?

CC_BACKUP_TRACE

public static final boolean CC_BACKUP_TRACE

Use backup tracing for cycle collection (currently the only option)

See Also:

Constant Field Values

performCycleCollection

public static boolean performCycleCollection

BT_CLOSURE

public static final short BT_CLOSURE

BUILD_FOR_GENRC

public static final boolean BUILD_FOR_GENRC

True if we are building for generational RC

refCountCollectionPhase

protected static final short refCountCollectionPhase

Reference counting specific collection steps.

genRCCollectionPhase

protected static final short genRCCollectionPhase

refCountRootClosurePhase

protected static final short refCountRootClosurePhase

Perform the initial determination of liveness from the roots.

genRCRootClosurePhase

protected static final short genRCRootClosurePhase

refCountCollection

public short refCountCollection

This is the phase that is executed to perform a collection.

genRCCollection

public short genRCCollection

rcSpace

public static final ExplicitFreeListSpace rcSpace

rcloSpace

public static final ExplicitLargeObjectSpace rcloSpace

REF_COUNT

public static final int REF_COUNT

REF_COUNT_LOS

public static final int REF_COUNT_LOS

modPool

public final SharedDeque modPool

decPool

public final SharedDeque decPool

newRootPool

public final SharedDeque newRootPool

oldRootPool

public final SharedDeque oldRootPool

rootTrace

public final Trace rootTrace

backupTrace

public final Trace backupTrace

rcSweeper

private final BTSweeper rcSweeper

loFreeSweeper

private final BTFreeLargeObjectSweeper loFreeSweeper

Constructor Detail

RCBase

public RCBase()

Constructor

Method Detail

processOptions

public void processOptions()

Description copied from class: StopTheWorld

The processOptions method is called by the runtime immediately after command-line arguments are available. Allocation must be supported prior to this point because the runtime infrastructure may require allocation in order to parse the command line arguments. For this reason all plans should operate gracefully on the default minimum heap size until the point that processOptions is called.

Overrides:

processOptions in class StopTheWorld

isRCObject

public static final boolean isRCObject(ObjectReference object)

Parameters:

object - an object reference

Returns:

whether the object is subject to collection by reference counting

lastCollectionFullHeap

public boolean lastCollectionFullHeap()

Overrides:

lastCollectionFullHeap in class Plan

Returns:

Whether last GC is a full GC.

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.

getPagesUsed

public int getPagesUsed()

Return the number of pages reserved for use given the pending allocation.

Overrides:

getPagesUsed in class Plan

Returns:

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

sanityLinearScan

public void sanityLinearScan(LinearScan scan)

Perform a linear scan across all objects in the heap to check for leaks.

Overrides:

sanityLinearScan in class Plan

Parameters:

scan - The scanner callback to use.

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

setBuildTimeGCByte

public byte setBuildTimeGCByte(Address object,
                               ObjectReference typeRef,
                               int size)

Description copied from class: Plan

Performs any required initialization of the GC portion of the header. Called for objects created at boot time.

Overrides:

setBuildTimeGCByte in class Plan

Parameters:

object - the Address representing the storage to be initialized

typeRef - the type reference for the instance being created

size - the number of bytes allocated by the GC system for this object.

Returns:

The new value of the status word