1 /*
2 * Copyright (c) 2004, 2011, 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.tools;
26
27 import sun.jvm.hotspot.tools.*;
28
29 import sun.jvm.hotspot.oops.*;
30 import sun.jvm.hotspot.runtime.VM;
31 import sun.jvm.hotspot.utilities.SystemDictionaryHelper;
32 import sun.jvm.hotspot.utilities.ObjectReader;
33 import sun.jvm.hotspot.utilities.MarkBits;
34
35 import java.util.HashMap;
36 import java.util.ArrayList;
37 import java.util.Collections;
38 import java.util.Comparator;
39
40 /*
41 * Iterates over the queue of object pending finalization and prints a
42 * summary of these objects in the form of a histogram.
43 */
44 public class FinalizerInfo extends Tool {
45 public static void main(String[] args) {
46 FinalizerInfo finfo = new FinalizerInfo();
47 finfo.start(args);
48 finfo.stop();
49 }
50
51 public void run() {
52 /*
53 * The implementation here has a dependency on the implementation of
54 * java.lang.ref.Finalizer. If the Finalizer implementation changes it's
55 * possible this method will require changes too. We looked into using
56 * ObjectReader to deserialize the objects from the target VM but as
57 * there aren't any public methods to traverse the queue it means using
58 * reflection which will also tie us to the implementation.
59 *
60 * The assumption here is that Finalizer.queue is the ReferenceQueue
61 * with the objects awaiting finalization. The ReferenceQueue queueLength
62 * is the number of objects in the queue, and 'head' is the head of the
63 * queue.
64 */
65 InstanceKlass ik =
66 SystemDictionaryHelper.findInstanceKlass("java.lang.ref.Finalizer");
67 final Oop[] queueref = new Oop[1];
68 ik.iterateStaticFields(new DefaultOopVisitor() {
69 public void doOop(OopField field, boolean isVMField) {
70 String name = field.getID().getName();
71 if (name.equals("queue")) {
72 queueref[0] = field.getValue(getObj());
73 }
74 }
75 });
76 Oop queue = queueref[0];
77
78 InstanceKlass k = (InstanceKlass) queue.getKlass();
79
80 LongField queueLengthField = (LongField) k.findField("queueLength", "J");
81 long queueLength = queueLengthField.getValue(queue);
82
83 OopField headField = (OopField) k.findField("head", "Ljava/lang/ref/Reference;");
84 Oop head = headField.getValue(queue);
85
86 System.out.println("Number of objects pending for finalization: " + queueLength);
87
88 /*
89 * If 'head' is non-NULL then it is the head of a list of References.
90 * We iterate over the list (end of list is when head.next == head)
91 */
92 if (head != null) {
93 k = (InstanceKlass) head.getKlass();
94 OopField referentField =
95 (OopField) k.findField("referent", "Ljava/lang/Object;");
96 OopField nextField =
97 (OopField) k.findField("next", "Ljava/lang/ref/Reference;");
98
99 HashMap map = new HashMap();
100 for (;;) {
101 Oop referent = referentField.getValue(head);
102
103 Klass klass = referent.getKlass();
104 if (!map.containsKey(klass)) {
105 map.put(klass, new ObjectHistogramElement(klass));
106 }
107 ((ObjectHistogramElement)map.get(klass)).updateWith(referent);
108
109 Oop next = nextField.getValue(head);
110 if (next == null || next.equals(head)) break;
111 head = next;
112 }
113
114 /*
115 * Sort results - decending order by total size
116 */
117 ArrayList list = new ArrayList();
118 list.addAll(map.values());
119 Collections.sort(list, new Comparator() {
120 public int compare(Object o1, Object o2) {
121 return ((ObjectHistogramElement)o1).compare((ObjectHistogramElement)o2);
122 }
123 });
124
125 /*
126 * Print summary of objects in queue
127 */
128 System.out.println("");
129 System.out.println("Count" + "\t" + "Class description");
130 System.out.println("-------------------------------------------------------");
131 for (int i=0; i<list.size(); i++) {
132 ObjectHistogramElement e = (ObjectHistogramElement)list.get(i);
133 System.out.println(e.getCount() + "\t" + e.getDescription());
134 }
135 }
136
137 }
138 }