org.mmtk.plan.generational.marksweep

Class GenMS

java.lang.Object

org.mmtk.plan.Plan

org.mmtk.plan.Simple

org.mmtk.plan.StopTheWorld

org.mmtk.plan.generational.Gen

org.mmtk.plan.generational.marksweep.GenMS

public class GenMS
extends Gen

This class implements the functionality of a two-generation copying collector where the higher generation is a mark-sweep space (free list allocation, mark-sweep collection). 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 the Jones & Lins GC book, chapter 7 for a detailed discussion of generational collection and section 7.3 for an overview of the flexible nursery behavior ("The Standard ML of New Jersey collector"), or go to Appel's paper "Simple generational garbage collection and fast allocation." SP&E 19(2):171--183, 1989.

For general comments about the global/local distinction among classes refer to Plan.java and PlanLocal.java.

Field Summary

Fields

Modifier and Type	Field and Description
Trace	matureTrace The trace class for a full-heap collection
static int	MS
static MarkSweepSpace	msSpace The mature space, which for GenMS uses a mark sweep collection policy.

Fields inherited from class org.mmtk.plan.generational.Gen

ALLOC_MATURE, ALLOC_MATURE_MAJORGC, ALLOC_MATURE_MINORGC, ALLOC_NURSERY, arrayRemsetPool, fullHeap, gcFullHeap, IGNORE_REMSETS, MATURE_FRACTION, modbufPool, nextGCFullHeap, NURSERY, NURSERY_VM_FRACTION, nurseryCons, nurseryMark, nurserySpace, nurseryTrace, remsetPool, SCAN_MATURE, SCAN_NURSERY, SURVIVAL_ESTIMATE, USE_NON_HEAP_OBJECT_REFERENCE_WRITE_BARRIER, USE_OBJECT_BARRIER, USE_OBJECT_BARRIER_FOR_AASTORE, USE_OBJECT_BARRIER_FOR_PUTFIELD, wbFast, wbSlow

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
GenMS()

Method Summary

Modifier and Type	Method and Description
protected 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.
int	getMaturePhysicalPagesAvail() Return the number of pages available for allocation into the mature space.
int	getPagesUsed() Return the number of pages reserved for use given the pending allocation.
protected void	registerSpecializedMethods() Registers specialized methods.
boolean	willNeverMove(ObjectReference object) Can this object ever move.

Methods inherited from class org.mmtk.plan.generational.Gen

collectionRequired, copyMature, forceFullHeapCollection, fullyBooted, getCollectionReserve, getPagesAvail, isCurrentGCNursery, lastCollectionFullHeap, printPreStats, requiresFullHeapCollection, sanityExpectedRC, traceFullHeap

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

msSpace

public static final MarkSweepSpace msSpace

The mature space, which for GenMS uses a mark sweep collection policy.

MS

public static final int MS

matureTrace

public final Trace matureTrace

The trace class for a full-heap collection

Constructor Detail

GenMS

public GenMS()

Method Detail

collectionPhase

public final void collectionPhase(short phaseId)

Perform a (global) collection phase.

Overrides:

collectionPhase in class Gen

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 Gen

Returns:

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

getMaturePhysicalPagesAvail

public int getMaturePhysicalPagesAvail()

Description copied from class: Gen

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

Specified by:

getMaturePhysicalPagesAvail in class Gen

Returns:

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

activeMatureSpace

protected final Space activeMatureSpace()

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

Specified by:

activeMatureSpace in class Gen

Returns:

The mature space, set by each subclass of Gen.

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 Gen

Parameters:

object - The object in question

Returns:

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

registerSpecializedMethods

protected void registerSpecializedMethods()

Description copied from class: Plan

Registers specialized methods.

Overrides:

registerSpecializedMethods in class Gen