/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Common Public License (CPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/cpl1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.mmtk.plan.refcount;
import org.mmtk.plan.*;
import org.mmtk.plan.refcount.cd.CDCollector;
import org.mmtk.plan.refcount.cd.NullCDCollector;
import org.mmtk.plan.refcount.cd.TrialDeletionCollector;
import org.mmtk.utility.deque.ObjectReferenceDeque;
import org.mmtk.utility.sanitychecker.SanityCheckerLocal;
import org.mmtk.vm.VM;
import org.vmmagic.pragma.*;
import org.vmmagic.unboxed.*;
/**
* This class implements <i>per-collector thread</i> behavior
* and state for the <i>RC</i> plan, which implements a full-heap
* reference counting collector.<p>
*
* Specifically, this class defines <i>RC</i> collection behavior
* (through <code>trace</code> and the <code>collectionPhase</code>
* method).<p>
*
* @see RCBase for an overview of the reference counting algorithm.<p>
*
* FIXME The SegregatedFreeList class (and its decendents such as
* MarkSweepLocal) does not properly separate mutator and collector
* behaviors, so the ms field below should really not exist in
* this class as there is no collection-time allocation in this
* collector.
*
* @see RCBase
* @see RCBaseMutator
* @see StopTheWorldCollector
* @see CollectorContext
*/
@Uninterruptible public abstract class RCBaseCollector extends StopTheWorldCollector {
/****************************************************************************
* Instance fields
*/
public ObjectReferenceDeque newRootSet;
public ObjectReferenceDeque oldRootSet;
public DecBuffer decBuffer;
public ObjectReferenceDeque modBuffer;
private NullCDCollector nullCD;
private TrialDeletionCollector trialDeletionCD;
private RCSanityCheckerLocal sanityChecker;
/****************************************************************************
* Initialization
*/
/**
* Constructor
*/
public RCBaseCollector() {
newRootSet = new ObjectReferenceDeque("new root", global().newRootPool);
oldRootSet = new ObjectReferenceDeque("old root", global().oldRootPool);
modBuffer = new ObjectReferenceDeque("mod buf", global().modPool);
decBuffer = new DecBuffer(global().decPool);
sanityChecker = new RCSanityCheckerLocal();
switch (RCBase.CYCLE_DETECTOR) {
case RCBase.NO_CYCLE_DETECTOR:
nullCD = new NullCDCollector();
break;
case RCBase.TRIAL_DELETION:
trialDeletionCD = new TrialDeletionCollector();
break;
}
}
/****************************************************************************
*
* Collection
*/
/**
* Perform a per-collector collection phase.
*
* @param phaseId The collection phase to perform
* @param primary Perform any single-threaded activities using this thread.
*/
@Inline
public void collectionPhase(short phaseId, boolean primary) {
if (phaseId == RCBase.PREPARE) {
if (RCBase.WITH_COALESCING_RC) {
processModBuffer();
}
processOldRootSet();
getCurrentTrace().prepare();
return;
}
if (phaseId == RCBase.CLOSURE) {
getCurrentTrace().completeTrace();
processNewRootSet();
return;
}
if (phaseId == RCBase.RELEASE) {
getCurrentTrace().release();
processDecBuffer();
return;
}
if (!cycleDetector().collectionPhase(phaseId, primary)) {
super.collectionPhase(phaseId, primary);
}
}
/**
* Report a root object.
*
* @param object The root
*/
public void reportRoot(ObjectReference object) {
if (VM.VERIFY_ASSERTIONS) {
VM.assertions._assert(RCBase.isRCObject(object));
}
RCHeader.incRC(object);
newRootSet.push(object);
}
/**
* Process the old root set, by either decrementing each
* entry, or unmarking the object's root flag.
*/
public void processOldRootSet() {
ObjectReference current;
while (!(current = oldRootSet.pop()).isNull()) {
decBuffer.push(current);
}
decBuffer.flushLocal();
}
/**
* Move the new root set so that it is the old set for the
* next collection.
*/
public void processNewRootSet() {
ObjectReference current;
while (!(current = newRootSet.pop()).isNull()) {
oldRootSet.push(current);
}
oldRootSet.flushLocal();
}
/**
* Process the decrement buffers, enqueing recursive
* decrements if necessary.
*/
public void processDecBuffer() {
ObjectReference current;
while (!(current = decBuffer.pop()).isNull()) {
if (VM.VERIFY_ASSERTIONS) {
VM.assertions._assert(RCBase.isRCObject(current));
}
switch (RCHeader.decRC(current)) {
case RCHeader.DEC_KILL:
decBuffer.processChildren(current);
if (global().cycleDetector().allowFree(current)) {
RCBase.free(current);
}
break;
case RCHeader.DEC_BUFFER:
cycleDetector().bufferOnDecRC(current);
break;
}
}
}
/**
* Process the modified object buffers.
*/
public void processModBuffer() {
TransitiveClosure modProcessor = getModifiedProcessor();
ObjectReference current;
while (!(current = modBuffer.pop()).isNull()) {
RCHeader.makeUnlogged(current);
VM.scanning.scanObject(modProcessor, current);
}
}
/****************************************************************************
*
* Miscellaneous
*/
/** @return The active global plan as an <code>MS</code> instance. */
@Inline
private static RCBase global() {
return (RCBase) VM.activePlan.global();
}
/** @return The current sanity checker. */
public SanityCheckerLocal getSanityChecker() {
return sanityChecker;
}
/** @return The TraceStep to use when processing modified objects. */
protected abstract TransitiveClosure getModifiedProcessor();
/** @return The active cycle detector instance */
@Inline
public final CDCollector cycleDetector() {
switch (RCBase.CYCLE_DETECTOR) {
case RCBase.NO_CYCLE_DETECTOR:
return nullCD;
case RCBase.TRIAL_DELETION:
return trialDeletionCD;
}
VM.assertions.fail("No cycle detector instance found.");
return null;
}
}