1 /*
   2  * Copyright (c) 2014, 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 package org.openjdk.bench.vm.compiler;
  24 
  25 import org.openjdk.jmh.annotations.Benchmark;
  26 import org.openjdk.jmh.annotations.BenchmarkMode;
  27 import org.openjdk.jmh.annotations.Mode;
  28 import org.openjdk.jmh.annotations.OutputTimeUnit;
  29 import org.openjdk.jmh.annotations.Param;
  30 import org.openjdk.jmh.annotations.Scope;
  31 import org.openjdk.jmh.annotations.State;
  32 import org.openjdk.jmh.infra.Blackhole;
  33 
  34 import java.util.Enumeration;
  35 import java.util.Hashtable;
  36 import java.util.concurrent.TimeUnit;
  37 
  38 /**
  39  * Tests that the JVM performs object explosion (or some sort of stack allocation).
  40  */
  41 @BenchmarkMode(Mode.AverageTime)
  42 @OutputTimeUnit(TimeUnit.NANOSECONDS)
  43 @State(Scope.Thread)
  44 public class Explosion {
  45 
  46     @Param("5")
  47     private int len;
  48 
  49     @Benchmark
  50     public void testHashtableExplosion(Blackhole bh) throws Exception {
  51         Object o = new Object();
  52         Object[] oa = new Object[len];
  53         for (int i = 0; i < len; i++) {
  54             oa[i] = new Object();
  55         }
  56 
  57         Hashtable<Object, Object> h = new Hashtable<>();
  58 
  59         for (int i = 0; i < len; i++) {
  60             h.put(oa[i], o);
  61         }
  62 
  63         Enumeration<Object> e = h.elements();
  64         while (e.hasMoreElements()) {
  65             bh.consume(e.nextElement());
  66         }
  67     }
  68 }