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 
  24 /**
  25  * @test TestDynShrinkHeap
  26  * @bug 8016479
  27  * @requires vm.gc=="Parallel" | vm.gc=="null"
  28  * @summary Verify that the heap shrinks after full GC according to the current values of the Min/MaxHeapFreeRatio flags
  29  * @library /testlibrary
  30  * @run main/othervm -XX:+UseAdaptiveSizePolicyWithSystemGC -XX:+UseParallelGC -XX:MinHeapFreeRatio=0 -XX:MaxHeapFreeRatio=100 -Xmx1g -verbose:gc TestDynShrinkHeap
  31  */
  32 import com.oracle.java.testlibrary.DynamicVMOption;
  33 import java.lang.management.ManagementFactory;
  34 import java.lang.management.MemoryUsage;
  35 import java.util.ArrayList;
  36 import sun.management.ManagementFactoryHelper;
  37 import com.oracle.java.testlibrary.Asserts;
  38 
  39 public class TestDynShrinkHeap {
  40 
  41     public static final String MIN_FREE_RATIO_FLAG_NAME = "MinHeapFreeRatio";
  42     public static final String MAX_FREE_RATIO_FLAG_NAME = "MaxHeapFreeRatio";
  43 
  44     private static ArrayList<byte[]> list = new ArrayList<>(0);
  45     private static final int LEN = 512 * 1024 + 1;
  46 
  47     public TestDynShrinkHeap() {
  48     }
  49 
  50     private final void test() {
  51         System.gc();
  52         MemoryUsagePrinter.printMemoryUsage("init");
  53 
  54         eat();
  55         MemoryUsagePrinter.printMemoryUsage("eaten");
  56         MemoryUsage muFull = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
  57 
  58         free();
  59         MemoryUsagePrinter.printMemoryUsage("free");
  60         MemoryUsage muFree = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
  61 
  62         Asserts.assertLessThan(muFree.getCommitted(), muFull.getCommitted(), String.format(
  63                 "committed free heap size is not less than committed full heap size, heap hasn't been shrunk?%n"
  64                 + "%s = %s%n%s = %s",
  65                 MIN_FREE_RATIO_FLAG_NAME,
  66                 ManagementFactoryHelper.getDiagnosticMXBean().getVMOption(MIN_FREE_RATIO_FLAG_NAME).getValue(),
  67                 MAX_FREE_RATIO_FLAG_NAME,
  68                 ManagementFactoryHelper.getDiagnosticMXBean().getVMOption(MAX_FREE_RATIO_FLAG_NAME).getValue()
  69         ));
  70     }
  71 
  72     private void eat() {
  73         for (int i = 0; i < LEN; i++) {
  74             list.add(new byte[1024]);
  75         }
  76         MemoryUsagePrinter.printMemoryUsage("allocated " + LEN + " arrays");
  77 
  78         list.subList(0, LEN / 2).clear();
  79         System.gc();
  80         MemoryUsagePrinter.printMemoryUsage("array halved");
  81     }
  82 
  83     private void free() {
  84         int min = DynamicVMOption.getInt(MIN_FREE_RATIO_FLAG_NAME);
  85         DynamicVMOption.setInt(MAX_FREE_RATIO_FLAG_NAME, min);
  86         System.gc();
  87         MemoryUsagePrinter.printMemoryUsage("under pressure");
  88     }
  89 
  90     public static void main(String[] args) {
  91         new TestDynShrinkHeap().test();
  92     }
  93 }
  94 
  95 /**
  96  * Prints memory usage to standard output
  97  */
  98 class MemoryUsagePrinter {
  99 
 100     public static String humanReadableByteCount(long bytes, boolean si) {
 101         int unit = si ? 1000 : 1024;
 102         if (bytes < unit) {
 103             return bytes + " B";
 104         }
 105         int exp = (int) (Math.log(bytes) / Math.log(unit));
 106         String pre = (si ? "kMGTPE" : "KMGTPE").charAt(exp - 1) + (si ? "" : "i");
 107         return String.format("%.1f %sB", bytes / Math.pow(unit, exp), pre);
 108     }
 109 
 110     public static void printMemoryUsage(String label) {
 111         MemoryUsage memusage = ManagementFactory.getMemoryMXBean().getHeapMemoryUsage();
 112         float freeratio = 1f - (float) memusage.getUsed() / memusage.getCommitted();
 113         System.out.format("[%-24s] init: %-7s, used: %-7s, comm: %-7s, freeRatio ~= %.1f%%%n",
 114                 label,
 115                 humanReadableByteCount(memusage.getInit(), true),
 116                 humanReadableByteCount(memusage.getUsed(), true),
 117                 humanReadableByteCount(memusage.getCommitted(), true),
 118                 freeratio * 100
 119         );
 120     }
 121 }