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;

  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.

  47  *
  48  * To work around these rather strange behaviors this test uses -Xmx4m but then
  49  * calculates what the expected heap size should be. The calculation is a
  50  * simplified version of the code in the VM. We assume that the card table will
  51  * use one page. Each byte in the card table corresponds to 512 bytes on the heap.
  52  * So, the expected heap size is page_size * 512.
  53  *
  54  * There is no formal requirement for the minimal value of the maximum heap size
  55  * the VM should support. In most cases the VM could start with -Xmx2m.
  56  * But with 2m limit GC could be triggered before VM initialization completed.
  57  * Therefore, the positive checks start the VM with -Xmx4m as minimum. 
  58  */
  59 
  60 import jdk.test.lib.Asserts;
  61 import jdk.test.lib.process.OutputAnalyzer;
  62 import jdk.test.lib.process.ProcessTools;
  63 
  64 import java.util.LinkedList;
  65 
  66 import sun.hotspot.WhiteBox;
  67 
  68 public class TestSmallHeap {
  69 
  70     public static void main(String[] args) throws Exception {
  71         // Do all work in the VM driving the test, the VM
  72         // with the small heap size should do as little as
  73         // possible to avoid hitting an OOME.
  74         WhiteBox wb = WhiteBox.getWhiteBox();
  75         int pageSize = wb.getVMPageSize();
  76         int heapBytesPerCard = 512;
  77         long expectedMaxHeap = pageSize * heapBytesPerCard;