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 /**
  27  * @test
  28  * @summary Verifies the JVMTI Heap Monitor stack depth handling.
  29  * @compile HeapMonitorStackDepthTest.java
  30  * @run main/othervm/native -agentlib:HeapMonitor MyPackage.HeapMonitorStackDepthTest
  31  */
  32 
  33 public class HeapMonitorStackDepthTest {
  34   static {
  35     try {
  36       System.loadLibrary("HeapMonitor");
  37     } catch (UnsatisfiedLinkError ule) {
  38       System.err.println("Could not load HeapMonitor library");
  39       System.err.println("java.library.path: "
  40           + System.getProperty("java.library.path"));
  41       throw ule;
  42     }
  43   }
  44 
  45   private native static void enableSampling();
  46   private native static void disableSampling();
  47   private native static double getAverageStackDepth();
  48 
  49   private static int g_tmp[];
  50 
  51   private static int helper() {
  52     int sum = 0;
  53     // Let us assume that the array is 24 bytes of memory.
  54     for (int i = 0; i < 127000 / 6; i++) {
  55       int tmp[] = new int[1];
  56       // Force it to be kept.
  57       g_tmp = tmp;
  58       sum += g_tmp[0];
  59     }
  60     return sum;
  61   }
  62 
  63   private static void finalWrapper() {
  64     int sum = 0;
  65 
  66     for (int j = 0; j < 5000; j++) {
  67       sum += helper();
  68     }
  69     System.out.println(sum);
  70   }
  71 
  72   private static void recursiveWrapper(int depth) {
  73     if (depth > 1) {
  74       recursiveWrapper(depth - 1);
  75     } else {
  76       finalWrapper();
  77     }
  78   }
  79 
  80   private static double calculateErrorPercentage(double expected, double actual) {
  81     double error = expected - actual;
  82     error = error < 0 ? -error : error;
  83     return error / expected * 100;
  84   }
  85 
  86   public static void main(String[] args) {
  87     int[] depths = {10, 100, 500};
  88 
  89     for (int depthIdx = 0; depthIdx < depths.length; depthIdx++) {
  90       int depth = depths[depthIdx];
  91 
  92       enableSampling();
  93       recursiveWrapper(depth);
  94       disableSampling();
  95 
  96       // baseDepth represents the helper method depth: main, finalWrapper, and helper.
  97       // To get the requested depth, remove this from the count.
  98       final int baseDepth = 3;
  99       double averageDepth = getAverageStackDepth() - baseDepth;
 100       double errorPercentage = calculateErrorPercentage(depth, averageDepth);
 101 
 102       // 1% error should be close enough.
 103       if (errorPercentage > 1) {
 104         throw new RuntimeException("Stack depth average over 5% for depth " + depth + " : " + averageDepth + " , error: " + errorPercentage);
 105       }
 106     }
 107 
 108     // Last test is 1024, which is the current maximum.
 109     enableSampling();
 110     final int maximumDepth = 1024;
 111     recursiveWrapper(maximumDepth);
 112     disableSampling();
 113     // Because of the extra frames, we should be at (maximumDepth + a few frames). Due to the
 114     // maximum depth allowed, we hit it and so should still be at an average of 1024.
 115     double averageDepth = getAverageStackDepth();
 116     double errorPercentage = calculateErrorPercentage(maximumDepth, averageDepth);
 117 
 118     // 1% error should be close enough.
 119     if (errorPercentage > 1) {
 120       throw new RuntimeException("Stack depth average over 5% for depth 1024 : " + averageDepth + " , error: " + errorPercentage);
 121     }
 122   }
 123 }