1 /*
2 * Copyright (c) 2017, Google 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 package MyPackage;
25
26 import java.util.ArrayList;
27 import java.util.List;
28
29 /** API for handling the underlying heap sampling monitoring system. */
30 public class HeapMonitor {
31 static {
32 try {
33 System.loadLibrary("HeapMonitor");
34 } catch (UnsatisfiedLinkError ule) {
35 System.err.println("Could not load HeapMonitor library");
36 System.err.println("java.library.path: " + System.getProperty("java.library.path"));
37 throw ule;
38 }
39 }
40
41 private static volatile int arrays[][];
42
43 /** Enable heap monitoring sampling given a rate and maximum garbage to keep in memory. */
44 public native static void enableSampling(int rate, int maximumGarbage);
45
46 /** Enable heap monitoring sampling given a rate. */
47 public static void enableSampling(int rate) {
48 enableSampling(rate, 200);
49 }
50
51 /** Enable heap monitoring sampling with default values for rate and maximum garbage. */
52 public static void enableSampling() {
53 enableSampling(1 << 19);
54 }
55
56 public native static void disableSampling();
57 public native static boolean areSamplingStatisticsZero();
58 public native static boolean statsHaveExpectedNumberSamples(int expected, int percentError);
59
60 /** Do the frames provided exist in live, recent garbage, and frequent garbage. */
61 public native static boolean framesExistEverywhere(Frame[] frames);
62 /** Do the frames provided not exist in live, recent garbage, and frequent garbage. */
63 public native static boolean framesExistNowhere(Frame[] frames);
64
65 /**
66 * Allocate memory but first create a stack trace of a particular depth.
67 *
68 * @return list of frames for the allocation.
69 */
70 public static List<Frame> allocate(int depth) {
71 List<Frame> frames = new ArrayList<Frame>();
72 if (depth > 1) {
73 createStackDepth(depth - 1, frames);
74 frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 73));
75 } else {
76 actuallyAllocate(frames);
77 frames.add(new Frame("actuallyAllocate", "(Ljava/util/List;)I", "HeapMonitor.java", 127));
78 frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 76));
79 }
80 return frames;
81 }
82
83 /**
84 * Allocate memory but first create a stack trace.
85 *
86 * @return list of frames for the allocation.
87 */
88 public static List<Frame> allocate() {
89 int sum = 0;
90 List<Frame> frames = new ArrayList<Frame>();
91 allocate(frames);
92 frames.add(new Frame("allocate", "()Ljava/util/List;", "HeapMonitor.java", 91));
93 return frames;
94 }
95
96 private static void createStackDepth(int depth, List<Frame> frames) {
97 if (depth > 1) {
98 createStackDepth(depth - 1, frames);
99 frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 98));
100 } else {
101 allocate(frames);
102 frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 101));
103 }
104 }
105
106 private static void allocate(List<Frame> frames) {
107 int sum = 0;
108 for (int j = 0; j < 1000; j++) {
109 sum += actuallyAllocate(frames);
110 }
111 frames.add(new Frame("actuallyAllocate", "(Ljava/util/List;)I", "HeapMonitor.java", 127));
112 frames.add(new Frame("allocate", "(Ljava/util/List;)V", "HeapMonitor.java", 109));
113 }
114
115 private static int actuallyAllocate(List<Frame> frames) {
116 int sum = 0;
117
118 // Let us assume that a 1-element array is 24 bytes of memory and we want
119 // 2MB allocated.
120 int iterations = (1 << 19) / 6;
121
122 if (arrays == null) {
123 arrays = new int[iterations][];
124 }
125
126 for (int i = 0; i < iterations; i++) {
127 int tmp[] = new int[1];
128 // Force it to be kept and, at the same time, wipe out any previous data.
129 arrays[i] = tmp;
130 sum += arrays[0][0];
131 }
132 return sum;
133 }
134
135 /** Remove the reference to the global array to free data at the next GC. */
136 public static void freeStorage() {
137 arrays = null;
138 }
139 }