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.markcompact;
014
015 import org.mmtk.plan.*;
016 import org.mmtk.policy.MarkCompactSpace;
017 import org.mmtk.policy.Space;
018 import org.mmtk.utility.heap.VMRequest;
019 import org.mmtk.utility.sanitychecker.SanityChecker;
020
021 import org.vmmagic.pragma.*;
022 import org.vmmagic.unboxed.ObjectReference;
023
024 /**
025 * This class implements the global state of a simple sliding mark-compact
026 * collector.<p>
027 *
028 * FIXME Need algorithmic overview and references.<p>
029 *
030 * All plans make a clear distinction between <i>global</i> and
031 * <i>thread-local</i> activities, and divides global and local state
032 * into separate class hierarchies. Global activities must be
033 * synchronized, whereas no synchronization is required for
034 * thread-local activities. There is a single instance of Plan (or the
035 * appropriate sub-class), and a 1:1 mapping of PlanLocal to "kernel
036 * threads" (aka CPUs). Thus instance
037 * methods of PlanLocal allow fast, unsychronized access to functions such as
038 * allocation and collection.<p>
039 *
040 * The global instance defines and manages static resources
041 * (such as memory and virtual memory resources). This mapping of threads to
042 * instances is crucial to understanding the correctness and
043 * performance properties of MMTk plans.
044 */
045 @Uninterruptible public class MC extends StopTheWorld {
046
047 /****************************************************************************
048 * Class variables
049 */
050
051 /** The mark compact space itself */
052 public static final MarkCompactSpace mcSpace = new MarkCompactSpace("mc", VMRequest.create(0.6f));
053
054 /** The space descriptor */
055 public static final int MARK_COMPACT = mcSpace.getDescriptor();
056
057 /** Specialized method identifier for the MARK phase */
058 public static final int SCAN_MARK = 0;
059
060 /** Specialized method identifier for the FORWARD phase */
061 public static final int SCAN_FORWARD = 1;
062
063 /* Phases */
064 public static final short PREPARE_FORWARD = Phase.createSimple("fw-prepare");
065 public static final short FORWARD_CLOSURE = Phase.createSimple("fw-closure");
066 public static final short RELEASE_FORWARD = Phase.createSimple("fw-release");
067
068 /** Calculate forwarding pointers via a linear scan over the heap */
069 public static final short CALCULATE_FP = Phase.createSimple("calc-fp");
070
071 /** Perform compaction via a linear scan over the heap */
072 public static final short COMPACT = Phase.createSimple("compact");
073
074 // CHECKSTYLE:OFF
075
076 /**
077 * This is the phase that is executed to perform a mark-compact collection.
078 *
079 * FIXME: Far too much duplication and inside knowledge of StopTheWorld
080 */
081 public short mcCollection = Phase.createComplex("collection", null,
082 Phase.scheduleComplex (initPhase),
083 Phase.scheduleComplex (rootClosurePhase),
084 Phase.scheduleComplex (refTypeClosurePhase),
085 Phase.scheduleComplex (completeClosurePhase),
086 Phase.scheduleCollector(CALCULATE_FP),
087 Phase.scheduleGlobal (PREPARE_FORWARD),
088 Phase.scheduleCollector(PREPARE_FORWARD),
089 Phase.scheduleMutator (PREPARE),
090 Phase.scheduleCollector(STACK_ROOTS),
091 Phase.scheduleCollector(ROOTS),
092 Phase.scheduleGlobal (ROOTS),
093 Phase.scheduleComplex (forwardPhase),
094 Phase.scheduleCollector(FORWARD_CLOSURE),
095 Phase.scheduleMutator (RELEASE),
096 Phase.scheduleCollector(RELEASE_FORWARD),
097 Phase.scheduleGlobal (RELEASE_FORWARD),
098 Phase.scheduleCollector(COMPACT),
099 Phase.scheduleComplex (finishPhase));
100
101 // CHECKSTYLE:ON
102
103 /****************************************************************************
104 * Instance variables
105 */
106
107 /** This trace sets the mark bit in live objects */
108 public final Trace markTrace;
109
110 /** This trace updates pointers with the forwarded references */
111 public final Trace forwardTrace;
112
113 /**
114 * Constructor.
115 */
116 public MC() {
117 markTrace = new Trace(metaDataSpace);
118 forwardTrace = new Trace(metaDataSpace);
119 collection = mcCollection;
120 }
121
122 /*****************************************************************************
123 *
124 * Collection
125 */
126
127
128 /**
129 * {@inheritDoc}
130 */
131 @Override
132 @Inline
133 public final void collectionPhase(short phaseId) {
134 if (phaseId == PREPARE) {
135 super.collectionPhase(phaseId);
136 markTrace.prepare();
137 mcSpace.prepare();
138 return;
139 }
140 if (phaseId == CLOSURE) {
141 markTrace.prepare();
142 return;
143 }
144 if (phaseId == RELEASE) {
145 markTrace.release();
146 mcSpace.release();
147 super.collectionPhase(phaseId);
148 return;
149 }
150
151 if (phaseId == PREPARE_FORWARD) {
152 super.collectionPhase(PREPARE);
153 forwardTrace.prepare();
154 mcSpace.prepare();
155 return;
156 }
157 if (phaseId == RELEASE_FORWARD) {
158 forwardTrace.release();
159 mcSpace.release();
160 super.collectionPhase(RELEASE);
161 return;
162 }
163
164 super.collectionPhase(phaseId);
165 }
166
167 /*****************************************************************************
168 *
169 * Accounting
170 */
171
172 /**
173 * {@inheritDoc}
174 * The superclass accounts for its spaces, we just
175 * augment this with the mark-sweep space's contribution.
176 */
177 @Override
178 public int getPagesUsed() {
179 return (mcSpace.reservedPages() + super.getPagesUsed());
180 }
181
182 @Override
183 public boolean willNeverMove(ObjectReference object) {
184 if (Space.isInSpace(MARK_COMPACT, object))
185 return false;
186 return super.willNeverMove(object);
187 }
188
189 @Override
190 public int sanityExpectedRC(ObjectReference object, int sanityRootRC) {
191 Space space = Space.getSpaceForObject(object);
192
193 // Nursery
194 if (space == MC.mcSpace) {
195 // We are never sure about objects in MC.
196 // This is not very satisfying but allows us to use the sanity checker to
197 // detect dangling pointers.
198 return SanityChecker.UNSURE;
199 }
200 return super.sanityExpectedRC(object, sanityRootRC);
201 }
202
203 @Override
204 @Interruptible
205 protected void registerSpecializedMethods() {
206 TransitiveClosure.registerSpecializedScan(SCAN_MARK, MCMarkTraceLocal.class);
207 TransitiveClosure.registerSpecializedScan(SCAN_FORWARD, MCForwardTraceLocal.class);
208 super.registerSpecializedMethods();
209 }
210 }