1 /*
   2  * Copyright (c) 2014, 2016, 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 TestSmallHeap
  26  * @bug 8067438 8152239
  27  * @requires vm.gc=="null"
  28  * @summary Verify that starting the VM with a small heap works
  29  * @library /testlibrary /test/lib /test/lib/share/classes
  30  * @modules java.base/jdk.internal.misc
  31  * @modules java.management/sun.management
  32  * @build TestSmallHeap
  33  * @run main ClassFileInstaller sun.hotspot.WhiteBox
  34  * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI TestSmallHeap
  35  */
  36 
  37 /* Note: It would be nice to verify the minimal supported heap size (2m) here,
  38  * but we align the heap size based on the card table size. And the card table
  39  * size is aligned based on the minimal pages size provided by the os. This
  40  * means that on most platforms, where the minimal page size is 4k, we get a
  41  * minimal heap size of 2m but on Solaris/Sparc we have a page size of 8k and
  42  * get a minimal heap size of 4m. And on platforms where the page size is 64k
  43  * we get a minimal heap size of 32m. We never use large pages for the card table.
  44  *
  45  * There is also no check in the VM for verifying that the maximum heap size
  46  * is larger than the supported minimal heap size. This means that specifying
  47  * -Xmx1m on the command line is fine but will give a heap of 2m (or 4m or 32m).
  48  *
  49  * To work around these rather strange behaviors this test uses -Xmx2m but then
  50  * calculates what the expected heap size should be. The calculation is a
  51  * simplified version of the code in the VM. We assume that the card table will
  52  * use one page. Each byte in the card table corresponds to 512 bytes on the heap.
  53  * So, the expected heap size is page_size * 512.
  54  */
  55 
  56 import jdk.test.lib.Asserts;
  57 import jdk.test.lib.process.OutputAnalyzer;
  58 import jdk.test.lib.process.ProcessTools;
  59 
  60 import java.util.LinkedList;
  61 
  62 import sun.hotspot.WhiteBox;
  63 
  64 public class TestSmallHeap {
  65 
  66     public static void main(String[] args) throws Exception {
  67         // Do all work in the VM driving the test, the VM
  68         // with the small heap size should do as little as
  69         // possible to avoid hitting an OOME.
  70         WhiteBox wb = WhiteBox.getWhiteBox();
  71         int pageSize = wb.getVMPageSize();
  72         int heapBytesPerCard = 512;
  73         long expectedMaxHeap = pageSize * heapBytesPerCard;
  74 
  75         verifySmallHeapSize("-XX:+UseParallelGC", expectedMaxHeap);
  76         verifySmallHeapSize("-XX:+UseSerialGC", expectedMaxHeap);
  77         verifySmallHeapSize("-XX:+UseG1GC", expectedMaxHeap);
  78         verifySmallHeapSize("-XX:+UseConcMarkSweepGC", expectedMaxHeap);
  79     }
  80 
  81     private static void verifySmallHeapSize(String gc, long expectedMaxHeap) throws Exception {

  82         LinkedList<String> vmOptions = new LinkedList<>();
  83         vmOptions.add(gc);
  84         vmOptions.add("-Xmx2m");
  85         vmOptions.add("-XX:+PrintFlagsFinal");
  86         vmOptions.add(VerifyHeapSize.class.getName());
  87 
  88         ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(vmOptions.toArray(new String[0]));
  89         OutputAnalyzer analyzer = new OutputAnalyzer(pb.start());
  90         analyzer.shouldHaveExitValue(0);
  91 

  92         long maxHeapSize = Long.parseLong(analyzer.firstMatch("MaxHeapSize.+=\\s+(\\d+)",1));
  93         long actualHeapSize = Long.parseLong(analyzer.firstMatch(VerifyHeapSize.actualMsg + "(\\d+)",1));
  94         Asserts.assertEQ(maxHeapSize, expectedMaxHeap);
  95         Asserts.assertLessThanOrEqual(actualHeapSize, maxHeapSize);
  96     }
  97 }
  98 
  99 class VerifyHeapSize {
 100     public static final String actualMsg = "Actual heap size: ";
 101 
 102     public static void main(String args[]) {
 103         // Avoid string concatenation
 104         System.out.print(actualMsg);
 105         System.out.println(Runtime.getRuntime().maxMemory());
 106     }
 107 }
--- EOF ---