1 /*
   2  * Copyright (c) 2020, 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 package gc.z;
  25 
  26 /*
  27  * @test TestPageCacheFlush
  28  * @requires vm.gc.Z
  29  * @summary Test ZGC page cache flushing
  30  * @library /test/lib
  31  * @run driver gc.z.TestPageCacheFlush
  32  */
  33 
  34 import java.util.LinkedList;
  35 import jdk.test.lib.process.ProcessTools;
  36 
  37 public class TestPageCacheFlush {
  38     static class Test {
  39         private static final int K = 1024;
  40         private static final int M = K * K;
  41         private static volatile LinkedList<byte[]> keepAlive;
  42 
  43         public static void fillPageCache(int size) {
  44             System.out.println("Begin allocate (" + size + ")");
  45 
  46             keepAlive = new LinkedList<>();
  47 
  48             try {
  49                 for (;;) {
  50                     keepAlive.add(new byte[size]);
  51                 }
  52             } catch (OutOfMemoryError e) {
  53                 keepAlive = null;
  54                 System.gc();
  55             }
  56 
  57             System.out.println("End allocate (" + size + ")");
  58         }
  59 
  60         public static void main(String[] args) throws Exception {
  61             // Allocate small objects to fill the page cache with small pages
  62             fillPageCache(10 * K);
  63 
  64             // Allocate large objects to provoke page cache flushing to rebuild
  65             // cached small pages into large pages
  66             fillPageCache(10 * M);
  67         }
  68     }
  69 
  70     public static void main(String[] args) throws Exception {
  71         ProcessTools.executeProcess(ProcessTools.createJavaProcessBuilder(
  72                                     "-XX:+UseZGC",
  73                                     "-Xms128M",
  74                                     "-Xmx128M",
  75                                     "-Xlog:gc,gc+init,gc+heap=debug",
  76                                     Test.class.getName()))
  77                     .outputTo(System.out)
  78                     .errorTo(System.out)
  79                     .shouldContain("Page Cache Flushed:")
  80                     .shouldHaveExitValue(0);
  81     }
  82 }