1 /*
   2  * Copyright (c) 2014, 2015, 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
  27  * @requires vm.gc=="null"
  28  * @requires (vm.opt.AggressiveOpts=="null") | (vm.opt.AggressiveOpts=="false")
  29  * @summary Verify that starting the VM with a small heap works
  30  * @library /testlibrary /../../test/lib
  31  * @build TestSmallHeap
  32  * @run main ClassFileInstaller sun.hotspot.WhiteBox
  33  * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -Xmx2m -XX:+UseParallelGC TestSmallHeap
  34  * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -Xmx2m -XX:+UseSerialGC TestSmallHeap
  35  * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -Xmx2m -XX:+UseG1GC TestSmallHeap
  36  * @run main/othervm -Xbootclasspath/a:. -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI -Xmx2m -XX:+UseConcMarkSweepGC TestSmallHeap
  37  */
  38 
  39 /* Note: It would be nice to verify the minimal supported heap size (2m) here,
  40  * but we align the heap size based on the card table size. And the card table
  41  * size is aligned based on the minimal pages size provided by the os. This
  42  * means that on most platforms, where the minimal page size is 4k, we get a
  43  * minimal heap size of 2m but on Solaris/Sparc we have a page size of 8k and
  44  * get a minimal heap size of 4m. And on platforms where the page size is 64k
  45  * we get a minimal heap size of 32m. We never use large pages for the card table.
  46  *
  47  * There is also no check in the VM for verifying that the maximum heap size
  48  * is larger than the supported minimal heap size. This means that specifying
  49  * -Xmx1m on the command line is fine but will give a heap of 2m (or 4m or 32m).
  50  *
  51  * To work around these rather strange behaviors this test uses -Xmx2m but then
  52  * calculates what the expected heap size should be. The calculation is a
  53  * simplified version of the code in the VM. We assume that the card table will
  54  * use one page. Each byte in the card table corresponds to 512 bytes on the heap.
  55  * So, the expected heap size is page_size * 512.
  56  */
  57 
  58 import com.oracle.java.testlibrary.*;
  59 import static com.oracle.java.testlibrary.Asserts.*;
  60 import sun.hotspot.WhiteBox;
  61 import sun.management.ManagementFactoryHelper;
  62 
  63 public class TestSmallHeap {
  64 
  65     public static void main(String[] args) {
  66         WhiteBox wb = WhiteBox.getWhiteBox();
  67         int pageSize = wb.getVMPageSize();
  68         int heapBytesPerCard = 512;
  69         long expectedMaxHeap = pageSize * heapBytesPerCard;
  70         String maxHeap = ManagementFactoryHelper.getDiagnosticMXBean().getVMOption("MaxHeapSize").getValue();
  71         assertEQ(Long.parseLong(maxHeap), expectedMaxHeap);
  72     }
  73 }