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.semispace.gctrace;
014
015 import org.mmtk.plan.semispace.*;
016 import org.mmtk.policy.RawPageSpace;
017 import org.mmtk.policy.Space;
018 import org.mmtk.utility.deque.SortTODSharedDeque;
019 import org.mmtk.utility.heap.VMRequest;
020 import org.mmtk.utility.TraceGenerator;
021 import org.mmtk.utility.options.Options;
022
023 import org.mmtk.vm.VM;
024
025 import org.vmmagic.pragma.*;
026
027 /**
028 * This plan has been modified slightly to perform the processing necessary
029 * for GC trace generation. To maximize performance, it attempts to remain
030 * as faithful as possible to semiSpace/Plan.java.
031 *
032 * The generated trace format is as follows:
033 * <pre>
034 * B 345678 12
035 * (Object 345678 was created in the boot image with a size of 12 bytes)
036 * U 59843 234 47298
037 * (Update object 59843 at the slot at offset 234 to refer to 47298)
038 * S 1233 12345
039 * (Update static slot 1233 to refer to 12345)
040 * T 4567 78924
041 * (The TIB of 4567 is set to refer to 78924)
042 * D 342789
043 * (Object 342789 became unreachable)
044 * A 6860 24 346648 3
045 * (Object 6860 was allocated, requiring 24 bytes, with fp 346648 on
046 * thread 3; this allocation has perfect knowledge)
047 * a 6884 24 346640 5
048 * (Object 6864 was allocated, requiring 24 bytes, with fp 346640 on
049 * thread 5; this allocation DOES NOT have perfect knowledge)
050 * I 6860 24 346648 3
051 * (Object 6860 was allocated into immortal space, requiring 24 bytes,
052 * with fp 346648 on thread 3; this allocation has perfect knowledge)
053 * i 6884 24 346640 5
054 * (Object 6864 was allocated into immortal space, requiring 24 bytes,
055 * with fp 346640 on thread 5; this allocation DOES NOT have perfect
056 * knowledge)
057 * 48954->[345]LObject;:blah()V:23 Ljava/lang/Foo;
058 * (Citation for: a) where the was allocated, fp of 48954,
059 * at the method with ID 345 -- or void Object.blah() -- and bytecode
060 * with offset 23; b) the object allocated is of type java.lang.Foo)
061 * D 342789 361460
062 * (Object 342789 became unreachable after 361460 was allocated)
063 * </pre>
064 * This class implements a simple semi-space collector. See the Jones
065 * & Lins GC book, section 2.2 for an overview of the basic
066 * algorithm. This implementation also includes a large object space
067 * (LOS), and an uncollected "immortal" space.<p>
068 *
069 * All plans make a clear distinction between <i>global</i> and
070 * <i>thread-local</i> activities. Global activities must be
071 * synchronized, whereas no synchronization is required for
072 * thread-local activities. Instances of Plan map 1:1 to "kernel
073 * threads" (aka CPUs). Thus instance
074 * methods allow fast, unsychronized access to Plan utilities such as
075 * allocation and collection. Each instance rests on static resources
076 * (such as memory and virtual memory resources) which are "global"
077 * and therefore "static" members of Plan. This mapping of threads to
078 * instances is crucial to understanding the correctness and
079 * performance proprties of this plan.
080 */
081 @Uninterruptible public class GCTrace extends SS {
082
083 /****************************************************************************
084 *
085 * Class variables
086 */
087
088 /* Spaces */
089
090 /**
091 *
092 */
093 public static final RawPageSpace traceSpace = new RawPageSpace("trace", VMRequest.create());
094 public static final int TRACE = traceSpace.getDescriptor();
095
096 /* GC state */
097 public static boolean lastGCWasTracing = false; // True when previous GC was for tracing
098 public static boolean traceInducedGC = false; // True if trace triggered GC
099 public static boolean deathScan = false;
100 public static boolean finalDead = false;
101
102 /****************************************************************************
103 *
104 * Initialization
105 */
106
107 /**
108 * Constructor
109 */
110 public GCTrace() {
111 SortTODSharedDeque workList = new SortTODSharedDeque("workList",traceSpace, 1);
112 SortTODSharedDeque traceBuf = new SortTODSharedDeque("traceBuf",traceSpace, 1);
113 workList.prepareNonBlocking();
114 traceBuf.prepareNonBlocking();
115 TraceGenerator.init(workList, traceBuf);
116 }
117
118 @Override
119 @Interruptible
120 public void processOptions() {
121 super.processOptions();
122 Options.noFinalizer.setValue(true);
123 }
124
125 /**
126 * The planExit method is called at RVM termination to allow the
127 * trace process to finish.
128 */
129 @Override
130 @Interruptible
131 public final void notifyExit(int value) {
132 super.notifyExit(value);
133 finalDead = true;
134 traceInducedGC = false;
135 deathScan = true;
136 TraceGenerator.notifyExit(value);
137 }
138
139 @Override
140 public final boolean collectionRequired(boolean spaceFull, Space space) {
141 if (super.collectionRequired(spaceFull, space)) {
142 traceInducedGC = false;
143 return true;
144 }
145 return false;
146 }
147
148 /****************************************************************************
149 *
150 * Collection
151 */
152
153 /**
154 * {@inheritDoc}
155 */
156 @Override
157 public void collectionPhase(short phaseId) {
158 if (phaseId == PREPARE) {
159 lastGCWasTracing = traceInducedGC;
160 }
161 if (phaseId == RELEASE) {
162 if (traceInducedGC) {
163 /* Clean up following a trace-induced scan */
164 deathScan = false;
165 } else {
166 /* Finish the collection by calculating the unreachable times */
167 deathScan = true;
168 TraceGenerator.postCollection();
169 deathScan = false;
170 /* Perform the semispace collections. */
171 super.collectionPhase(phaseId);
172 }
173 } else if (!traceInducedGC ||
174 (phaseId == INITIATE) ||
175 (phaseId == PREPARE_STACKS) ||
176 (phaseId == ROOTS) ||
177 (phaseId == STACK_ROOTS) ||
178 (phaseId == COMPLETE)) {
179 /* Performing normal GC; sponge off of parent's work. */
180 super.collectionPhase(phaseId);
181 }
182 }
183
184
185 /****************************************************************************
186 *
187 * Space management
188 */
189
190 /**
191 * @return Since trace induced collections are not called to free up memory,
192 * their failure to return memory isn't cause for concern.
193 */
194 public boolean isLastGCFull() {
195 return !lastGCWasTracing;
196 }
197
198 /**
199 * @return the active Plan as a GCTrace
200 */
201 public static GCTrace global() {
202 return ((GCTrace) VM.activePlan.global());
203 }
204 }