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.TraceLocal;
018 import org.mmtk.plan.Trace;
019 import org.mmtk.policy.Space;
020 import org.mmtk.utility.HeaderByte;
021 import org.mmtk.utility.deque.ObjectReferenceDeque;
022 import org.mmtk.vm.VM;
023
024 import org.vmmagic.pragma.*;
025 import org.vmmagic.unboxed.*;
026
027 /**
028 * This class implements the thread-local functionality for a transitive
029 * closure over an immix space.
030 */
031 @Uninterruptible
032 public final class ImmixTraceLocal extends TraceLocal {
033
034 /****************************************************************************
035 *
036 * Instance fields
037 */
038 private final ObjectReferenceDeque modBuffer;
039
040 /**
041 * Constructor
042 *
043 * @param trace The trace associated with this trace local.
044 * @param modBuffer The modified objects buffer associated with this trace local. Possibly null.
045 */
046 public ImmixTraceLocal(Trace trace, ObjectReferenceDeque modBuffer) {
047 super(Immix.SCAN_IMMIX, 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 (object.isNull()) return false;
062 if (Space.isInSpace(Immix.IMMIX, object)) {
063 return Immix.immixSpace.fastIsLive(object);
064 }
065 return super.isLive(object);
066 }
067
068 /**
069 * {@inheritDoc}<p>
070 *
071 * In this instance, we refer objects in the mark-sweep space to the
072 * immixSpace for tracing, and defer to the superclass for all others.
073 *
074 * @param object The object to be traced.
075 * @return The new reference to the same object instance.
076 */
077 @Override
078 @Inline
079 public ObjectReference traceObject(ObjectReference object) {
080 if (object.isNull()) return object;
081 if (Space.isInSpace(Immix.IMMIX, object))
082 return Immix.immixSpace.fastTraceObject(this, object);
083 return super.traceObject(object);
084 }
085
086 /**
087 * Ensure that the referenced object will not move from this point through
088 * to the end of the collection. This can involve forwarding the object
089 * if necessary.
090 */
091 @Inline
092 @Override
093 public boolean willNotMoveInCurrentCollection(ObjectReference object) {
094 if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(!Immix.immixSpace.inImmixDefragCollection());
095 return true;
096 }
097
098 @Inline
099 @Override
100 protected void scanObject(ObjectReference object) {
101 super.scanObject(object);
102 if (MARK_LINE_AT_SCAN_TIME && Space.isInSpace(Immix.IMMIX, object))
103 Immix.immixSpace.markLines(object);
104 }
105
106 /**
107 * Process any remembered set entries. This means enumerating the
108 * mod buffer and for each entry, marking the object as unlogged
109 * (we don't enqueue for scanning since we're doing a full heap GC).
110 */
111 @Override
112 protected void processRememberedSets() {
113 if (modBuffer != null) {
114 logMessage(5, "clearing modBuffer");
115 while (!modBuffer.isEmpty()) {
116 ObjectReference src = modBuffer.pop();
117 HeaderByte.markAsUnlogged(src);
118 }
119 }
120 }
121 }