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 55 public native static void enableSamplingEvents(); 56 public native static void disableSamplingEvents(); 57 58 /** 59 * Allocate memory but first create a stack trace of a particular depth. 60 * 61 * @return list of frames for the allocation. 62 */ 63 public static List<Frame> allocate(int depth) { 64 List<Frame> frames = new ArrayList<Frame>(); 65 if (depth > 1) { 66 createStackDepth(depth - 1, frames); 67 frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 61)); 68 } else { 69 actuallyAllocate(); 70 frames.add(new Frame("actuallyAllocate", "()I", "HeapMonitor.java", 126)); 71 frames.add(new Frame("allocate", "(I)Ljava/util/List;", "HeapMonitor.java", 64)); 72 } 73 return frames; 74 } 75 76 /** 77 * Allocate memory but first create a stack trace. 78 * 79 * @return list of frames for the allocation. 80 */ 81 public static List<Frame> allocate() { 82 int sum = 0; 83 List<Frame> frames = new ArrayList<Frame>(); 84 allocate(frames); 85 frames.add(new Frame("allocate", "()Ljava/util/List;", "HeapMonitor.java", 79)); 86 return frames; 87 } 88 89 private static void createStackDepth(int depth, List<Frame> frames) { 90 if (depth > 1) { 91 createStackDepth(depth - 1, frames); 92 frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 86)); 93 } else { 94 allocate(frames); 95 frames.add(new Frame("createStackDepth", "(ILjava/util/List;)V", "HeapMonitor.java", 89)); 96 } 97 } 98 99 private static void allocate(List<Frame> frames) { 100 int sum = 0; 101 for (int j = 0; j < 1000; j++) { 102 sum += actuallyAllocate(); 103 } 104 frames.add(new Frame("actuallyAllocate", "()I", "HeapMonitor.java", 124)); 105 frames.add(new Frame("allocate", "(Ljava/util/List;)V", "HeapMonitor.java", 97)); 106 } 107 108 public static List<Frame> repeatAllocate(int max) { 109 List<Frame> frames = null; 110 for (int i = 0; i < max; i++) { 111 frames = allocate(); 112 } 113 frames.add(new Frame("repeatAllocate", "(I)Ljava/util/List;", "HeapMonitor.java", 106)); 114 return frames; 115 } 116 117 private static int actuallyAllocate() { 118 int sum = 0; 119 120 // Let us assume that a 1-element array is 24 bytes of memory and we want 121 // 2MB allocated. 122 int iterations = (1 << 19) / 6; 123 124 if (arrays == null) { 125 arrays = new int[iterations][]; 126 } 127 128 for (int i = 0; i < iterations; i++) { 129 int tmp[] = new int[1]; 130 // Force it to be kept and, at the same time, wipe out any previous data. 131 arrays[i] = tmp; 132 sum += arrays[0][0]; 133 } 134 return sum; 135 } 136 137 /** Remove the reference to the global array to free data at the next GC. */ 138 public static void freeStorage() { 139 arrays = null; 140 } 141 142 public native static boolean obtainedEvents(Frame[] frames); 143 public native static boolean eventStorageIsEmpty(); 144 public native static void resetEventStorage(); 145 }