1 /*
2 * Copyright (c) 2002, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 package sun.jvm.hotspot.utilities;
26
27 import java.io.*;
28 import java.util.*;
29 import sun.jvm.hotspot.debugger.*;
30 import sun.jvm.hotspot.classfile.*;
31 import sun.jvm.hotspot.gc.shared.*;
32 import sun.jvm.hotspot.memory.*;
33 import sun.jvm.hotspot.oops.*;
34 import sun.jvm.hotspot.runtime.*;
35 import sun.jvm.hotspot.utilities.*;
36
37 /** For a set of known roots, descends recursively into the object
38 graph, for each object recording those objects (and their fields)
39 which point to it. NOTE: currently only a subset of the roots
40 known to the VM is exposed to the SA: objects on the stack, static
41 fields in classes, and JNI handles. These should be most of the
42 user-level roots keeping objects alive. */
43
44 public class ReversePtrsAnalysis {
45 // Used for debugging this code
46 private static final boolean DEBUG = false;
47
48 public ReversePtrsAnalysis() {
49 }
50
51 /** Sets an optional progress thunk */
52 public void setHeapProgressThunk(HeapProgressThunk thunk) {
53 progressThunk = thunk;
54 }
55
56
57 /** Runs the analysis algorithm */
58 public void run() {
59 if (VM.getVM().getRevPtrs() != null) {
60 return; // Assume already done
61 }
62
63 VM vm = VM.getVM();
64 rp = new ReversePtrs();
65 vm.setRevPtrs(rp);
66 Universe universe = vm.getUniverse();
67 CollectedHeap collHeap = universe.heap();
68 usedSize = collHeap.used();
69 visitedSize = 0;
70
71 // Note that an experiment to iterate the heap linearly rather
72 // than in recursive-descent order has been done. It turns out
73 // that the recursive-descent algorithm is nearly twice as fast
74 // due to the fact that it scans only live objects and (currently)
75 // only a fraction of the perm gen, namely the static fields
76 // contained in instanceKlasses. (Iterating the heap linearly
77 // would also change the semantics of the result so that
78 // ReversePtrs.get() would return a non-null value even for dead
79 // objects.) Nonetheless, the reverse pointer computation is still
80 // quite slow and optimization in field iteration of objects
81 // should be done.
82
83 if (progressThunk != null) {
84 // Get it started
85 progressThunk.heapIterationFractionUpdate(0);
86 }
87
88 // Allocate mark bits for heap
89 markBits = new MarkBits(collHeap);
90
91 // Get a hold of the object heap
92 heap = vm.getObjectHeap();
93
94 // Do each thread's roots
95 for (JavaThread thread = VM.getVM().getThreads().first();
96 thread != null;
97 thread = thread.next()) {
98 ByteArrayOutputStream bos = new ByteArrayOutputStream();
99 thread.printThreadIDOn(new PrintStream(bos));
100 String threadDesc =
101 " in thread \"" + thread.getThreadName() +
102 "\" (id " + bos.toString() + ")";
103 doStack(thread,
104 new RootVisitor("Stack root" + threadDesc));
105 doJNIHandleBlock(thread.activeHandles(),
106 new RootVisitor("JNI handle root" + threadDesc));
107 }
108
109 // Do global JNI handles
110 JNIHandles handles = VM.getVM().getJNIHandles();
111 doJNIHandleBlock(handles.globalHandles(),
112 new RootVisitor("Global JNI handle root"));
113 doJNIHandleBlock(handles.weakGlobalHandles(),
114 new RootVisitor("Weak global JNI handle root"));
115
116 // Do Java-level static fields
117 ClassLoaderDataGraph cldg = VM.getVM().getClassLoaderDataGraph();
118 cldg.classesDo(new ClassLoaderDataGraph.ClassVisitor() {
119
120 public void visit(Klass k) {
121 if (k instanceof InstanceKlass) {
122 final InstanceKlass ik = (InstanceKlass)k;
123 ik.iterateStaticFields(
124 new DefaultOopVisitor() {
125 public void doOop(OopField field, boolean isVMField) {
126 Oop next = field.getValue(getObj());
127 NamedFieldIdentifier nfi = new NamedFieldIdentifier("Static field \"" +
128 field.getID().getName() +
129 "\" in class \"" +
130 ik.getName().asString() + "\"");
131 LivenessPathElement lp = new LivenessPathElement(null, nfi);
132 rp.put(lp, next);
133 try {
134 markAndTraverse(next);
135 } catch (AddressException e) {
136 System.err.print("RevPtrs analysis: WARNING: AddressException at 0x" +
137 Long.toHexString(e.getAddress()) +
138 " while traversing static fields of InstanceKlass ");
139 ik.printValueOn(System.err);
140 System.err.println();
141 } catch (UnknownOopException e) {
142 System.err.println("RevPtrs analysis: WARNING: UnknownOopException while " +
143 "traversing static fields of InstanceKlass ");
144 ik.printValueOn(System.err);
145 System.err.println();
146 }
147 }
148 });
149 }
150 }
151 });
152
153 if (progressThunk != null) {
154 progressThunk.heapIterationComplete();
155 }
156
157 // Clear out markBits
158 markBits = null;
159 }
160
161
162 //---------------------------------------------------------------------------
163 // Internals only below this point
164 //
165 private HeapProgressThunk progressThunk;
166 private long usedSize;
167 private long visitedSize;
168 private double lastNotificationFraction;
169 private static final double MINIMUM_NOTIFICATION_FRACTION = 0.01;
170 private ObjectHeap heap;
171 private MarkBits markBits;
172 private int depth; // Debugging only
173 private ReversePtrs rp;
174
175 private void markAndTraverse(OopHandle handle) {
176 try {
177 markAndTraverse(heap.newOop(handle));
178 } catch (AddressException e) {
179 System.err.println("RevPtrs analysis: WARNING: AddressException at 0x" +
180 Long.toHexString(e.getAddress()) +
181 " while traversing oop at " + handle);
182 } catch (UnknownOopException e) {
183 System.err.println("RevPtrs analysis: WARNING: UnknownOopException for " +
184 "oop at " + handle);
185 }
186 }
187
188 private void printHeader() {
189 for (int i = 0; i < depth; i++) {
190 System.err.print(" ");
191 }
192 }
193
194 private void markAndTraverse(final Oop obj) {
195
196 // End of path
197 if (obj == null) {
198 return;
199 }
200
201 // Visited object
202 if (!markBits.mark(obj)) {
203 return;
204 }
205
206 // Root of work list for objects to be visited. A simple
207 // stack for saving new objects to be analyzed.
208
209 final Stack workList = new Stack();
210
211 // Next object to be visited.
212 Oop next = obj;
213
214 try {
215 // Node in the list currently being visited.
216
217 while (true) {
218 final Oop currObj = next;
219
220 // For the progress meter
221 if (progressThunk != null) {
222 visitedSize += currObj.getObjectSize();
223 double curFrac = (double) visitedSize / (double) usedSize;
224 if (curFrac >
225 lastNotificationFraction + MINIMUM_NOTIFICATION_FRACTION) {
226 progressThunk.heapIterationFractionUpdate(curFrac);
227 lastNotificationFraction = curFrac;
228 }
229 }
230
231 if (DEBUG) {
232 ++depth;
233 printHeader();
234 System.err.println("ReversePtrs.markAndTraverse(" +
235 currObj.getHandle() + ")");
236 }
237
238 // Iterate over the references in the object. Do the
239 // reverse pointer analysis for each reference.
240 // Add the reference to the work-list so that its
241 // references will be visited.
242 currObj.iterate(new DefaultOopVisitor() {
243 public void doOop(OopField field, boolean isVMField) {
244 // "field" refers to a reference in currObj
245 Oop next = field.getValue(currObj);
246 rp.put(new LivenessPathElement(currObj, field.getID()), next);
247 if ((next != null) && markBits.mark(next)) {
248 workList.push(next);
249 }
250 }
251 }, false);
252
253 if (DEBUG) {
254 --depth;
255 }
256
257 // Get the next object to visit.
258 next = (Oop) workList.pop();
259 }
260 } catch (EmptyStackException e) {
261 // Done
262 } catch (NullPointerException e) {
263 System.err.println("ReversePtrs: WARNING: " + e +
264 " during traversal");
265 } catch (Exception e) {
266 System.err.println("ReversePtrs: WARNING: " + e +
267 " during traversal");
268 }
269 }
270
271
272 class RootVisitor implements AddressVisitor {
273 RootVisitor(String baseRootDescription) {
274 this.baseRootDescription = baseRootDescription;
275 }
276
277 public void visitAddress(Address addr) {
278 Oop next = heap.newOop(addr.getOopHandleAt(0));
279 LivenessPathElement lp = new LivenessPathElement(null,
280 new NamedFieldIdentifier(baseRootDescription +
281 " @ " + addr));
282 rp.put(lp, next);
283 markAndTraverse(next);
284 }
285
286 public void visitCompOopAddress(Address addr) {
287 Oop next = heap.newOop(addr.getCompOopHandleAt(0));
288 LivenessPathElement lp = new LivenessPathElement(null,
289 new NamedFieldIdentifier(baseRootDescription +
290 " @ " + addr));
291 rp.put(lp, next);
292 markAndTraverse(next);
293 }
294
295 private String baseRootDescription;
296 }
297
298 // Traverse the roots on a given thread's stack
299 private void doStack(JavaThread thread, AddressVisitor oopVisitor) {
300 for (StackFrameStream fst = new StackFrameStream(thread); !fst.isDone(); fst.next()) {
301 fst.getCurrent().oopsDo(oopVisitor, fst.getRegisterMap());
302 }
303 }
304
305 // Traverse a JNIHandleBlock
306 private void doJNIHandleBlock(JNIHandleBlock handles, AddressVisitor oopVisitor) {
307 handles.oopsDo(oopVisitor);
308 }
309 }