/*
 * Copyright (c) 2018, Google and/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.
 *
 * 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.
 */

package MyPackage;

/**
 * @test
 * @build Frame HeapMonitor
 * @summary Verifies the JVMTI Heap Monitor Thread sanity
 * @compile HeapMonitorThreadTest.java
 * @run main/othervm/native -agentlib:HeapMonitor MyPackage.HeapMonitorThreadTest
 */

import java.util.ArrayList;
import java.util.List;

public class HeapMonitorThreadTest {
  private native static boolean checkSamples(int numThreads);

  public static void main(String[] args) {
    final int numThreads = 24;
    ArrayList<Thread> list = new ArrayList<>();

    // Remember a lot of garbage to have space for all thread samples.
    HeapMonitor.enableSamplingEvents();

    for (int i = 0 ; i < numThreads; i++) {
      Thread thread = new Thread(new Allocator(i), "Allocator" + i);
      thread.start();
      list.add(thread);
    }

    for (Thread elem : list) {
      try {
        elem.join();
      } catch(InterruptedException e) {
        throw new RuntimeException("Thread got interrupted...");
      }
    }

    if (!checkSamples(numThreads)) {
      throw new RuntimeException("Problem with checkSamples...");
    }
  }
}

class Allocator implements Runnable {
  private int depth;
  private List<int[]> currentList;

  public Allocator(int depth) {
    this.depth = depth;
  }

  private void helper() {
    List<int[]> newList = new ArrayList<>();
    // Let us assume that the array is 24 bytes of memory, by default we sample at 512k, keep in
    // memory at least 2MB without counting the link-list itself, which adds to this.
    int iterations = (1 << 21) / 24;
    for (int i = 0; i < iterations; i++) {
      int newTmp[] = new int[1];
      // Force it to be kept.
      newList.add(newTmp);
    }

    // Replace old list with new list, which provokes two things:
    //  Old list will get GC'd at some point.
    //  New list forces that this thread has some allocations still sampled.
    currentList = newList;
  }

  private void recursiveWrapper(int depth) {
    if (depth > 0) {
      recursiveWrapper(depth - 1);
    }
    helper();
  }

  public void run() {
    for (int j = 0; j < 50; j++) {
      recursiveWrapper(depth);
    }
  }
}