1 /* 2 * Copyright (c) 2018, 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 private static int[][] arrays; 32 33 static { 34 try { 35 System.loadLibrary("HeapMonitor"); 36 } catch (UnsatisfiedLinkError ule) { 37 System.err.println("Could not load HeapMonitor library"); 38 System.err.println("java.library.path: " + System.getProperty("java.library.path")); 39 throw ule; 40 } 41 } 42 43 /** Enable heap monitoring sampling with default value for rate. */ 44 public static void enableSamplingRate() { 45 setSamplingRate(1 << 19); 46 } 47 48 public static void disableSamplingRate() { 49 setSamplingRate(0); 50 } 51 52 /** Set a specific sampling rate, 0 turns off sampling. */ 53 public native static void setSamplingRate(int rate); 54 /** Set a specific garbage history buffer. */ 55 public native static void setGarbageHistory(int amount); 56 57 public native static void enableSamplingEvents(); 58 public native static void disableSamplingEvents(); 59 60 /** 61 * Allocate memory but first create a stack trace of a particular depth. 62 * 63 * @return list of frames for the allocation. 64 */ 65 public static List<Frame> allocate(int depth) { 66 List<Frame> frames = new ArrayList<Frame>(); 67 if (depth > 1) { 68 createStackDepth(depth - 1, frames); 69 frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 68)); 70 } else { 71 actuallyAllocate(); 72 frames.add(new Frame("actuallyAllocate", "()I", "HeapMonitor.java", 131)); 73 frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 71)); 74 } 75 return frames; 76 } 77 78 /** 79 * Allocate memory but first create a stack trace. 80 * 81 * @return list of frames for the allocation. 82 */ 83 public static List<Frame> allocate() { 84 int sum = 0; 85 List<Frame> frames = new ArrayList<Frame>(); 86 allocate(frames); 87 frames.add(new Frame("allocate", "()Ljava/util/List;", "HeapMonitor.java", 86)); 88 return frames; 89 } 90 91 private static void createStackDepth(int depth, List<Frame> frames) { 92 if (depth > 1) { 93 createStackDepth(depth - 1, frames); 94 frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 93)); 95 } else { 96 allocate(frames); 97 frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 96)); 98 } 99 } 100 101 private static void allocate(List<Frame> frames) { 102 int sum = 0; 103 for (int j = 0; j < 1000; j++) { 104 sum += actuallyAllocate(); 105 } 106 frames.add(new Frame("actuallyAllocate", "()I", "HeapMonitor.java", 131)); 107 frames.add(new Frame("allocate", "(Ljava/util/List;)V", "HeapMonitor.java", 104)); 108 } 109 110 public static List<Frame> repeatAllocate(int max) { 111 List<Frame> frames = null; 112 for (int i = 0; i < max; i++) { 113 frames = allocate(); 114 } 115 frames.add(new Frame("repeatAllocate", "(I)Ljava/util/List;", "HeapMonitor.java", 113)); 116 return frames; 117 } 118 119 private static int actuallyAllocate() { 120 int sum = 0; 121 122 // Let us assume that a 1-element array is 24 bytes of memory and we want 123 // 2MB allocated. 124 int iterations = (1 << 19) / 6; 125 126 if (arrays == null) { 127 arrays = new int[iterations][]; 128 } 129 130 for (int i = 0; i < iterations; i++) { 131 int tmp[] = new int[1]; 132 // Force it to be kept and, at the same time, wipe out any previous data. 133 arrays[i] = tmp; 134 sum += arrays[0][0]; 135 } 136 return sum; 137 } 138 139 public static int allocateSize(int totalSize) { 140 int sum = 0; 141 142 // Let us assume that a 1-element array is 24 bytes. 143 int iterations = totalSize / 24; 144 145 if (arrays == null) { 146 arrays = new int[iterations][]; 147 } 148 149 System.out.println("Allocating for " + iterations); 150 for (int i = 0; i < iterations; i++) { 151 int tmp[] = new int[1]; 152 153 // Force it to be kept and, at the same time, wipe out any previous data. 154 arrays[i] = tmp; 155 sum += arrays[0][0]; 156 } 157 158 return sum; 159 } 160 161 /** Remove the reference to the global array to free data at the next GC. */ 162 public static void freeStorage() { 163 arrays = null; 164 } 165 166 public native static boolean obtainedEvents(Frame[] frames); 167 public native static boolean garbageContains(Frame[] frames); 168 public native static boolean eventStorageIsEmpty(); 169 public native static void resetEventStorage(); 170 public native static int getEventStorageElementCount(); 171 public native static void forceGarbageCollection(); 172 173 public static boolean statsHaveExpectedNumberSamples(int expected, int acceptedErrorPercentage) { 174 double actual = getEventStorageElementCount(); 175 double diffPercentage = Math.abs(actual - expected) / expected; 176 return diffPercentage < acceptedErrorPercentage; 177 } 178 }