1 /* 2 * Copyright (c) 2018, 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 import java.lang.instrument.ClassFileTransformer; 26 import java.lang.instrument.Instrumentation; 27 import java.lang.instrument.IllegalClassFormatException; 28 import java.security.ProtectionDomain; 29 30 // This test is sensitive to -Xmx. It must be run with -xmx64m. 31 // Running with a different -Xmx requires changing the parameters and careful re-testing. 32 public class HumongousDuringDumpTransformer implements ClassFileTransformer { 33 public byte[] transform(ClassLoader loader, String name, Class<?> classBeingRedefined, 34 ProtectionDomain pd, byte[] buffer) throws IllegalClassFormatException { 35 if (name.equals("Hello")) { 36 try { 37 makeHumongousRegions(); 38 } catch (Throwable t) { 39 array = null; 40 humon = null; 41 System.out.println("Unexpected error: " + t); 42 t.printStackTrace(); 43 } 44 } 45 array = null; 46 return null; 47 } 48 49 private static Instrumentation savedInstrumentation; 50 51 public static void premain(String agentArguments, Instrumentation instrumentation) { 52 long xmx = Runtime.getRuntime().maxMemory(); 53 if (xmx < 60 * 1024 * 1024 || xmx > 80 * 1024 * 1024) { 54 System.out.println("Running with incorrect heap size: " + xmx); 55 System.exit(1); 56 } 57 58 System.out.println("ClassFileTransformer.premain() is called"); 59 instrumentation.addTransformer(new HumongousDuringDumpTransformer(), /*canRetransform=*/true); 60 savedInstrumentation = instrumentation; 61 } 62 63 public static Instrumentation getInstrumentation() { 64 return savedInstrumentation; 65 } 66 67 public static void agentmain(String args, Instrumentation inst) throws Exception { 68 premain(args, inst); 69 } 70 71 Object[] array; 72 73 static final int DUMMY_SIZE = 4096 - 16 - 8; 74 static final int HUMON_SIZE = 4 * 1024 * 1024 - 16 - 8; 75 static final int SKIP = 13; 76 77 byte humon[] = null; 78 boolean first = true; 79 80 public synchronized void makeHumongousRegions() { 81 if (!first) { 82 return; 83 } 84 System.out.println("==============================================================================="); 85 first = false; 86 87 int total = 0; 88 array = new Object[100000]; 89 System.out.println(array); 90 91 // (1) Allocate about 8MB of old objects. 92 for (int n=0, i=0; total < 8 * 1024 * 1024; n++) { 93 // Make enough allocations to cause a GC (for 64MB heap) to create 94 // old regions. 95 // 96 // But don't completely fill up the heap. That would cause OOM and 97 // may not be handled gracefully inside class transformation! 98 Object x = new byte[DUMMY_SIZE]; 99 if ((n % SKIP) == 0) { 100 array[i++] = x; 101 total += DUMMY_SIZE; 102 } 103 } 104 105 System.gc(); 106 107 // (2) Now allocate a humongous array. It will sit above the 8MB of old regions. 108 humon = new byte[HUMON_SIZE]; 109 array = null; 110 System.gc(); 111 } 112 }