/*
 * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
 *
 * 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.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

/*
 * @test ChurnNotifications
 * @summary Check that MX notifications are reported for all cycles
 *
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=passive      -XX:+ShenandoahDegeneratedGC -Dprecise=true  ChurnNotifications
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=passive      -XX:-ShenandoahDegeneratedGC -Dprecise=true  ChurnNotifications
 *
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=aggressive   -Dprecise=false ChurnNotifications
 *
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=adaptive     -Dprecise=false ChurnNotifications
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=static       -Dprecise=false ChurnNotifications
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=compact      -Dprecise=false ChurnNotifications
 * @run main/othervm -Xmx128m -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCHeuristics=traversal    -Dprecise=false ChurnNotifications
 */

import java.util.*;
import java.util.concurrent.atomic.*;
import javax.management.*;
import java.lang.management.*;
import javax.management.openmbean.*;
import com.sun.management.GarbageCollectionNotificationInfo;

public class ChurnNotifications {

  static final long HEAP_MB   = 128;                           // adjust for test configuration above
  static final long TARGET_MB = Long.getLong("target", 8_000); // 8 Gb allocation

  // Should we track the churn precisely?
  // Precise tracking is only reliable when GC is fully stop-the-world. Otherwise,
  // we cannot tell, looking at heap used before/after, what was the GC churn.
  static final boolean PRECISE = Boolean.getBoolean("precise");

  static final long M = 1024*1024;

  static volatile Object sink;

  public static void main(String[] args) throws Exception {
    final AtomicLong churnBytes = new AtomicLong();

    NotificationListener listener = new NotificationListener() {
      @Override
      public void handleNotification(Notification n, Object o) {
        if (n.getType().equals(GarbageCollectionNotificationInfo.GARBAGE_COLLECTION_NOTIFICATION)) {
          GarbageCollectionNotificationInfo info = GarbageCollectionNotificationInfo.from((CompositeData)n.getUserData());
          Map<String, MemoryUsage> mapBefore = info.getGcInfo().getMemoryUsageBeforeGc();
          Map<String, MemoryUsage> mapAfter = info.getGcInfo().getMemoryUsageAfterGc();

          MemoryUsage before = mapBefore.get("Shenandoah");
          MemoryUsage after  = mapAfter.get("Shenandoah");

          if ((before != null) && (after != null)) {
            long diff = before.getUsed() - after.getUsed();
            if (diff > 0) {
              churnBytes.addAndGet(diff);
            }
          }
        }
      }
    };

    for (GarbageCollectorMXBean bean : ManagementFactory.getGarbageCollectorMXBeans()) {
      ((NotificationEmitter) bean).addNotificationListener(listener, null, null);
    }

    final int size = 100_000;
    long count = TARGET_MB * 1024 * 1024 / (16 + 4*size);

    long mem = count * (16 + 4*size);

    for (int c = 0; c < count; c++) {
       sink = new int[size];
    }

    System.gc();

    Thread.sleep(1000);

    long actual = churnBytes.get();

    long minExpected = PRECISE ? (mem - HEAP_MB*1024*1024) : 1;
    long maxExpected = mem + HEAP_MB*1024*1024;

    String msg = "Expected = [" + minExpected/M +"; " + maxExpected/M + "] (" + mem/M + "), actual = " + actual/M;
    if (minExpected < actual && actual < maxExpected) {
      System.out.println(msg);
    } else {
      throw new IllegalStateException(msg);
    }
  }
}