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.stickyimmix;
014
015 import static org.mmtk.policy.immix.ImmixConstants.MARK_LINE_AT_SCAN_TIME;
016 import static org.mmtk.policy.immix.ImmixConstants.TMP_PREFER_COPY_ON_NURSERY_GC;
017
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 transitive
030 * closure over a sticky-immix space.
031 */
032 @Uninterruptible
033 public final class StickyImmixNurseryTraceLocal extends TraceLocal {
034
035 /****************************************************************************
036 *
037 * Instance fields.
038 */
039 private final ObjectReferenceDeque modBuffer;
040
041 /**
042 * Constructor
043 */
044 public StickyImmixNurseryTraceLocal(Trace trace, ObjectReferenceDeque modBuffer) {
045 super(StickyImmix.SCAN_NURSERY, trace);
046 this.modBuffer = modBuffer;
047 }
048
049 /****************************************************************************
050 *
051 * Externally visible Object processing and tracing
052 */
053
054 /**
055 * Is the specified object live?
056 *
057 * @param object The object.
058 * @return True if the object is live.
059 */
060 public boolean isLive(ObjectReference object) {
061 if (object.isNull()) return false;
062 if (Space.isInSpace(StickyImmix.IMMIX, object))
063 return TMP_PREFER_COPY_ON_NURSERY_GC ? StickyImmix.immixSpace.copyNurseryIsLive(object) : StickyImmix.immixSpace.fastIsLive(object);
064 if (VM.VERIFY_ASSERTIONS) VM.assertions._assert(super.isLive(object));
065 return true;
066 }
067
068 /**
069 * This method is the core method during the trace of the object graph.
070 * The role of this method is to:
071 *
072 * 1. Ensure the traced object is not collected.
073 * 2. If this is the first visit to the object enqueue it to be scanned.
074 * 3. Return the forwarded reference to the object.
075 *
076 * In this instance, we refer objects in the mark-sweep space to the
077 * msSpace for tracing, and defer to the superclass for all others.
078 *
079 * @param object The object to be traced.
080 * @return The new reference to the same object instance.
081 */
082 @Inline
083 public ObjectReference traceObject(ObjectReference object) {
084 if (object.isNull()) return object;
085 if (Space.isInSpace(StickyImmix.IMMIX, object))
086 return StickyImmix.immixSpace.nurseryTraceObject(this, object, StickyImmix.ALLOC_DEFAULT);
087 else
088 return object;
089 }
090
091 /**
092 * Return true if this object is guaranteed not to move during this
093 * collection (i.e. this object is definitely not an unforwarded
094 * object).
095 *
096 * @param object
097 * @return True if this object is guaranteed not to move during this
098 * collection.
099 */
100 @Override
101 public boolean willNotMoveInCurrentCollection(ObjectReference object) {
102 if (Space.isInSpace(StickyImmix.IMMIX, object)) {
103 if (!TMP_PREFER_COPY_ON_NURSERY_GC)
104 return true;
105 else
106 return StickyImmix.immixSpace.willNotMoveThisNurseryGC(object);
107 }
108 return super.willNotMoveInCurrentCollection(object);
109 }
110
111 /**
112 * Collectors that move objects <b>must</b> override this method.
113 * It performs the deferred scanning of objects which are forwarded
114 * during bootstrap of each copying collection. Because of the
115 * complexities of the collection bootstrap (such objects are
116 * generally themselves gc-critical), the forwarding and scanning of
117 * the objects must be dislocated. It is an error for a non-moving
118 * collector to call this method.
119 *
120 * @param object The forwarded object to be scanned
121 */
122 @Inline
123 @Override
124 protected void scanObject(ObjectReference object) {
125 super.scanObject(object);
126 if (MARK_LINE_AT_SCAN_TIME && Space.isInSpace(StickyImmix.IMMIX, object))
127 StickyImmix.immixSpace.markLines(object);
128 }
129
130 /**
131 * Process any remembered set entries. This means enumerating the
132 * mod buffer and for each entry, marking the object as unlogged
133 * and enqueing it for scanning.
134 */
135 protected void processRememberedSets() {
136 logMessage(2, "processing modBuffer");
137 while (!modBuffer.isEmpty()) {
138 ObjectReference src = modBuffer.pop();
139 HeaderByte.markAsUnlogged(src);
140 processNode(src);
141 }
142 }
143 }