001 /*
002 * This file is part of the Jikes RVM project (http://jikesrvm.org).
003 *
004 * This file is licensed to You under the Eclipse Public License (EPL);
005 * You may not use this file except in compliance with the License. You
006 * may obtain a copy of the License at
007 *
008 * http://www.opensource.org/licenses/eclipse-1.0.php
009 *
010 * See the COPYRIGHT.txt file distributed with this work for information
011 * regarding copyright ownership.
012 */
013 package org.mmtk.plan.immix;
014
015 import static org.mmtk.policy.immix.ImmixConstants.MARK_LINE_AT_SCAN_TIME;
016
017 import org.mmtk.plan.Plan;
018 import org.mmtk.plan.TraceLocal;
019 import org.mmtk.plan.Trace;
020 import org.mmtk.policy.Space;
021 import org.mmtk.utility.HeaderByte;
022 import org.mmtk.utility.deque.ObjectReferenceDeque;
023 import org.mmtk.vm.VM;
024
025 import org.vmmagic.pragma.*;
026 import org.vmmagic.unboxed.*;
027
028 /**
029 * This class implements the thread-local functionality for a defragmenting
030 * transitive closure over an immix space.
031 */
032 @Uninterruptible
033 public final class ImmixDefragTraceLocal extends TraceLocal {
034
035 /****************************************************************************
036 *
037 * Instance fields
038 */
039 private final ObjectReferenceDeque modBuffer;
040
041 /**
042 * Constructor
043 * @param trace TODO
044 * @param modBuffer TODO
045 */
046 public ImmixDefragTraceLocal(Trace trace, ObjectReferenceDeque modBuffer) {
047 super(Immix.SCAN_DEFRAG, trace);
048 this.modBuffer = modBuffer;
049 }
050
051 /****************************************************************************
052 *
053 * Externally visible Object processing and tracing
054 */
055
056 /**
057 * {@inheritDoc}
058 */
059 @Override
060 public boolean isLive(ObjectReference object) {
061 if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
062 if (object.isNull()) return false;
063 if (Space.isInSpace(Immix.IMMIX, object)) {
064 return Immix.immixSpace.isLive(object);
065 }
066 return super.isLive(object);
067 }
068
069 /**
070 * {@inheritDoc}<p>
071 *
072 * In this instance, we refer objects in the mark-sweep space to the
073 * immixSpace for tracing, and defer to the superclass for all others.
074 *
075 * @param object The object to be traced.
076 * @return The new reference to the same object instance.
077 */
078 @Override
079 @Inline
080 public ObjectReference traceObject(ObjectReference object) {
081 if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
082 if (object.isNull()) return object;
083 if (Space.isInSpace(Immix.IMMIX, object))
084 return Immix.immixSpace.traceObject(this, object, Plan.ALLOC_DEFAULT);
085 return super.traceObject(object);
086 }
087
088 /**
089 * Return {@code true} if this object is guaranteed not to move during this
090 * collection (i.e. this object is defintely not an unforwarded
091 * object).
092 *
093 * @param object
094 * @return {@code true} if this object is guaranteed not to move during this
095 * collection.
096 */
097 @Override
098 public boolean willNotMoveInCurrentCollection(ObjectReference object) {
099 if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
100 if (Space.isInSpace(Immix.IMMIX, object))
101 return Immix.immixSpace.willNotMoveThisGC(object);
102 return true;
103 }
104
105 @Inline
106 @Override
107 protected void scanObject(ObjectReference object) {
108 if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(Immix.immixSpace.inImmixDefragCollection());
109 super.scanObject(object);
110 if (MARK_LINE_AT_SCAN_TIME && Space.isInSpace(Immix.IMMIX, object))
111 Immix.immixSpace.markLines(object);
112 }
113
114 /**
115 * Process any remembered set entries. This means enumerating the
116 * mod buffer and for each entry, marking the object as unlogged
117 * (we don't enqueue for scanning since we're doing a full heap GC).
118 */
119 @Override
120 protected void processRememberedSets() {
121 if (modBuffer != null) {
122 logMessage(5, "clearing modBuffer");
123 while (!modBuffer.isEmpty()) {
124 ObjectReference src = modBuffer.pop();
125 HeaderByte.markAsUnlogged(src);
126 }
127 }
128 }
129 }