test/hotspot/jtreg/gc/shenandoah/TestAllocIntArrays.java

@@ -1,7 +1,8 @@
  /*
   * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.
+  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.

@@ -91,14 +92,26 @@
   *
   * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -Xmx1g -Xms1g
   *      -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=adaptive
   *      -XX:+ShenandoahVerify
   *      TestAllocIntArrays
+  */
+ 
+ /*
+  * @test id=generational
+  * @summary Acceptance tests: collector can withstand allocation
+  * @key randomness
+  * @requires vm.gc.Shenandoah
+  * @library /test/lib
   *
   * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -Xmx1g -Xms1g
   *      -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=adaptive
   *      TestAllocIntArrays
+  *
+  * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -Xmx1g -Xms1g
+  *      -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=adaptive -XX:ShenandoahGCMode=generational
+  *      TestAllocIntArrays
   */
  
  /*
   * @test id=static
   * @summary Acceptance tests: collector can withstand allocation

@@ -195,13 +208,18 @@
      static volatile Object sink;
  
      public static void main(String[] args) throws Exception {
          final int min = 0;
          final int max = 384 * 1024;
+         // Each allocated int array is assumed to consume 16 bytes for alignment and header, plus
+         //  an average of 4 * the average number of elements in the array.
          long count = TARGET_MB * 1024 * 1024 / (16 + 4 * (min + (max - min) / 2));
  
          Random r = Utils.getRandomInstance();
+         // Repeatedly, allocate an array of int having between 0 and 384K elements, until we have
+         // allocated approximately TARGET_MB.  The largest allocated array consumes 384K*4 + 16, which is 1.5 M,
+         // which is well below the heap size of 1g.
          for (long c = 0; c < count; c++) {
              sink = new int[min + r.nextInt(max - min)];
          }
      }