/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.io;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.lessThan;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import java.io.IOException;
import java.lang.management.ManagementFactory;
import java.lang.management.RuntimeMXBean;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CopyOnWriteArraySet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.client.Delete;
import org.apache.hadoop.hbase.client.Mutation;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.io.hfile.BlockCacheKey;
import org.apache.hadoop.hbase.io.hfile.ExclusiveMemHFileBlock;
import org.apache.hadoop.hbase.io.hfile.HFileBlock;
import org.apache.hadoop.hbase.io.hfile.HFileContext;
import org.apache.hadoop.hbase.io.hfile.LruBlockCache;
import org.apache.hadoop.hbase.io.hfile.LruCachedBlock;
import org.apache.hadoop.hbase.io.hfile.SharedMemHFileBlock;
import org.apache.hadoop.hbase.regionserver.CSLMImmutableSegment;
import org.apache.hadoop.hbase.regionserver.CellArrayImmutableSegment;
import org.apache.hadoop.hbase.regionserver.CellArrayMap;
import org.apache.hadoop.hbase.regionserver.CellSet;
import org.apache.hadoop.hbase.regionserver.CompactingMemStore;
import org.apache.hadoop.hbase.regionserver.CompactionPipeline;
import org.apache.hadoop.hbase.regionserver.DefaultMemStore;
import org.apache.hadoop.hbase.regionserver.HRegion;
import org.apache.hadoop.hbase.regionserver.HStore;
import org.apache.hadoop.hbase.regionserver.ImmutableSegment;
import org.apache.hadoop.hbase.regionserver.MemStoreCompactor;
import org.apache.hadoop.hbase.regionserver.MutableSegment;
import org.apache.hadoop.hbase.regionserver.Segment;
import org.apache.hadoop.hbase.regionserver.StoreContext;
import org.apache.hadoop.hbase.regionserver.TimeRangeTracker.NonSyncTimeRangeTracker;
import org.apache.hadoop.hbase.regionserver.TimeRangeTracker.SyncTimeRangeTracker;
import org.apache.hadoop.hbase.regionserver.throttle.StoreHotnessProtector;
import org.apache.hadoop.hbase.testclassification.IOTests;
import org.apache.hadoop.hbase.testclassification.SmallTests;
import org.apache.hadoop.hbase.util.ClassSize;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Testing the sizing that HeapSize offers and compares to the size given by ClassSize.
 */
@Tag(IOTests.TAG)
@Tag(SmallTests.TAG)
public class TestHeapSize {

  private static final Logger LOG = LoggerFactory.getLogger(TestHeapSize.class);
  // List of classes implementing HeapSize
  // BatchOperation, BatchUpdate, BlockIndex, Entry, Entry<K,V>, HStoreKey
  // KeyValue, LruBlockCache, Put, WALKey

  @BeforeAll
  public static void beforeClass() throws Exception {
    // Print detail on jvm so we know what is different should below test fail.
    RuntimeMXBean b = ManagementFactory.getRuntimeMXBean();
    LOG.info("name=" + b.getName());
    LOG.info("specname=" + b.getSpecName());
    LOG.info("specvendor=" + b.getSpecVendor());
    LOG.info("vmname=" + b.getVmName());
    LOG.info("vmversion=" + b.getVmVersion());
    LOG.info("vmvendor=" + b.getVmVendor());
    Map<String, String> p = b.getSystemProperties();
    LOG.info("properties=" + p);
  }

  /**
   * Test our hard-coded sizing of native java objects
   */
  @Test
  public void testNativeSizes() throws IOException {
    Class<?> cl;
    long expected;
    long actual;

    // ArrayList
    cl = ArrayList.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.ARRAYLIST;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // ByteBuffer
    cl = ByteBuffer.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.BYTE_BUFFER;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // Integer
    cl = Integer.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.INTEGER;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // Map.Entry
    // Interface is public, all others are not. Hard to size via ClassSize
    // cl = Map.Entry.class;
    // expected = ClassSize.estimateBase(cl, false);
    // actual = ClassSize.MAP_ENTRY;
    // if(expected != actual) {
    // ClassSize.estimateBase(cl, true);
    // assertEquals(expected, actual);
    // }

    // Object
    cl = Object.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.align(ClassSize.OBJECT);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // TreeMap
    cl = TreeMap.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.TREEMAP;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // String
    cl = String.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.STRING;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // ConcurrentHashMap
    cl = ConcurrentHashMap.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.CONCURRENT_HASHMAP;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // ConcurrentSkipListMap
    cl = ConcurrentSkipListMap.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.CONCURRENT_SKIPLISTMAP;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // CellArrayMap
    cl = CellArrayMap.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.CELL_ARRAY_MAP;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // ReentrantReadWriteLock
    cl = ReentrantReadWriteLock.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.REENTRANT_LOCK;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // AtomicLong
    cl = AtomicLong.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.ATOMIC_LONG;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // AtomicInteger
    cl = AtomicInteger.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.ATOMIC_INTEGER;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // AtomicBoolean
    cl = AtomicBoolean.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.ATOMIC_BOOLEAN;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // CopyOnWriteArraySet
    cl = CopyOnWriteArraySet.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.COPYONWRITE_ARRAYSET;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // CopyOnWriteArrayList
    cl = CopyOnWriteArrayList.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.COPYONWRITE_ARRAYLIST;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // SyncTimeRangeTracker
    cl = SyncTimeRangeTracker.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.SYNC_TIMERANGE_TRACKER;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // NonSyncTimeRangeTracker
    cl = NonSyncTimeRangeTracker.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.NON_SYNC_TIMERANGE_TRACKER;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // CellSet
    cl = CellSet.class;
    expected = ClassSize.estimateBase(cl, false);
    actual = ClassSize.CELL_SET;
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }
  }

  /**
   * Testing the classes that implements HeapSize and are a part of 0.20. Some are not tested here
   * for example BlockIndex which is tested in TestHFile since it is a non public class
   */
  @Test
  public void testSizes() throws IOException {
    Class<?> cl;
    long expected;
    long actual;

    // KeyValue
    cl = KeyValue.class;
    expected = ClassSize.estimateBase(cl, false);
    KeyValue kv = new KeyValue();
    actual = kv.heapSize();
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // LruBlockCache Overhead
    cl = LruBlockCache.class;
    actual = LruBlockCache.CACHE_FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // CachedBlock Fixed Overhead
    // We really need "deep" sizing but ClassSize does not do this.
    // Perhaps we should do all these more in this style....
    cl = LruCachedBlock.class;
    actual = LruCachedBlock.PER_BLOCK_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    expected += ClassSize.estimateBase(String.class, false);
    expected += ClassSize.estimateBase(ByteBuffer.class, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(String.class, true);
      ClassSize.estimateBase(ByteBuffer.class, true);
      assertEquals(expected, actual);
    }

    // DefaultMemStore Overhead
    cl = DefaultMemStore.class;
    actual = DefaultMemStore.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // DefaultMemStore Deep Overhead
    actual = DefaultMemStore.DEEP_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // CompactingMemStore Deep Overhead
    cl = CompactingMemStore.class;
    actual = CompactingMemStore.DEEP_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    expected += ClassSize.estimateBase(AtomicBoolean.class, false);
    expected += ClassSize.estimateBase(AtomicBoolean.class, false);
    expected += ClassSize.estimateBase(CompactionPipeline.class, false);
    expected += ClassSize.estimateBase(LinkedList.class, false); // inside CompactionPipeline
    expected += ClassSize.estimateBase(LinkedList.class, false); // inside CompactionPipeline
    expected += ClassSize.estimateBase(MemStoreCompactor.class, false);
    expected += ClassSize.estimateBase(AtomicBoolean.class, false);// inside MemStoreCompactor
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(AtomicBoolean.class, true);
      ClassSize.estimateBase(AtomicBoolean.class, true);
      ClassSize.estimateBase(CompactionPipeline.class, true);
      ClassSize.estimateBase(LinkedList.class, true);
      ClassSize.estimateBase(LinkedList.class, true);
      ClassSize.estimateBase(MemStoreCompactor.class, true);
      ClassSize.estimateBase(AtomicBoolean.class, true);
      assertEquals(expected, actual);
    }

    // Segment Deep overhead
    cl = Segment.class;
    actual = Segment.DEEP_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    expected += 2 * ClassSize.estimateBase(AtomicLong.class, false);
    expected += ClassSize.estimateBase(AtomicReference.class, false);
    expected += ClassSize.estimateBase(CellSet.class, false);
    expected += ClassSize.estimateBase(ReentrantReadWriteLock.class, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicReference.class, true);
      ClassSize.estimateBase(CellSet.class, true);
      ClassSize.estimateBase(ReentrantReadWriteLock.class, true);
      assertEquals(expected, actual);
    }

    // MutableSegment Deep overhead
    cl = MutableSegment.class;
    actual = MutableSegment.DEEP_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    expected += 2 * ClassSize.estimateBase(AtomicLong.class, false);
    expected += ClassSize.estimateBase(AtomicReference.class, false);
    expected += ClassSize.estimateBase(CellSet.class, false);
    expected += ClassSize.estimateBase(ReentrantReadWriteLock.class, false);
    expected += ClassSize.estimateBase(SyncTimeRangeTracker.class, false);
    expected += ClassSize.estimateBase(ConcurrentSkipListMap.class, false);
    expected += ClassSize.estimateBase(AtomicBoolean.class, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicReference.class, true);
      ClassSize.estimateBase(CellSet.class, true);
      ClassSize.estimateBase(ReentrantReadWriteLock.class, true);
      ClassSize.estimateBase(SyncTimeRangeTracker.class, true);
      ClassSize.estimateBase(ConcurrentSkipListMap.class, true);
      ClassSize.estimateBase(AtomicBoolean.class, true);
      assertEquals(expected, actual);
    }

    // ImmutableSegments Deep overhead
    cl = ImmutableSegment.class;
    actual = ImmutableSegment.DEEP_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    expected += 2 * ClassSize.estimateBase(AtomicLong.class, false);
    expected += ClassSize.estimateBase(AtomicReference.class, false);
    expected += ClassSize.estimateBase(CellSet.class, false);
    expected += ClassSize.estimateBase(ReentrantReadWriteLock.class, false);
    expected += ClassSize.estimateBase(NonSyncTimeRangeTracker.class, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicReference.class, true);
      ClassSize.estimateBase(CellSet.class, true);
      ClassSize.estimateBase(ReentrantReadWriteLock.class, true);
      ClassSize.estimateBase(NonSyncTimeRangeTracker.class, true);
      assertEquals(expected, actual);
    }

    cl = CSLMImmutableSegment.class;
    actual = CSLMImmutableSegment.DEEP_OVERHEAD_CSLM;
    expected = ClassSize.estimateBase(cl, false);
    expected += 2 * ClassSize.estimateBase(AtomicLong.class, false);
    expected += ClassSize.estimateBase(AtomicReference.class, false);
    expected += ClassSize.estimateBase(CellSet.class, false);
    expected += ClassSize.estimateBase(ReentrantReadWriteLock.class, false);
    expected += ClassSize.estimateBase(NonSyncTimeRangeTracker.class, false);
    expected += ClassSize.estimateBase(ConcurrentSkipListMap.class, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicReference.class, true);
      ClassSize.estimateBase(CellSet.class, true);
      ClassSize.estimateBase(ReentrantReadWriteLock.class, true);
      ClassSize.estimateBase(NonSyncTimeRangeTracker.class, true);
      ClassSize.estimateBase(ConcurrentSkipListMap.class, true);
      assertEquals(expected, actual);
    }
    cl = CellArrayImmutableSegment.class;
    actual = CellArrayImmutableSegment.DEEP_OVERHEAD_CAM;
    expected = ClassSize.estimateBase(cl, false);
    expected += 2 * ClassSize.estimateBase(AtomicLong.class, false);
    expected += ClassSize.estimateBase(AtomicReference.class, false);
    expected += ClassSize.estimateBase(CellSet.class, false);
    expected += ClassSize.estimateBase(ReentrantReadWriteLock.class, false);
    expected += ClassSize.estimateBase(NonSyncTimeRangeTracker.class, false);
    expected += ClassSize.estimateBase(CellArrayMap.class, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicLong.class, true);
      ClassSize.estimateBase(AtomicReference.class, true);
      ClassSize.estimateBase(CellSet.class, true);
      ClassSize.estimateBase(ReentrantReadWriteLock.class, true);
      ClassSize.estimateBase(NonSyncTimeRangeTracker.class, true);
      ClassSize.estimateBase(CellArrayMap.class, true);
      assertEquals(expected, actual);
    }

    // Store Overhead
    cl = HStore.class;
    actual = HStore.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // Region Overhead
    cl = HRegion.class;
    actual = HRegion.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    cl = StoreHotnessProtector.class;
    actual = StoreHotnessProtector.FIXED_SIZE;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // Block cache key overhead. Only tests fixed overhead as estimating heap
    // size of strings is hard.
    cl = BlockCacheKey.class;
    actual = BlockCacheKey.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    // Currently NOT testing Deep Overheads of many of these classes.
    // Deep overheads cover a vast majority of stuff, but will not be 100%
    // accurate because it's unclear when we're referencing stuff that's already
    // accounted for. But we have satisfied our two core requirements.
    // Sizing is quite accurate now, and our tests will throw errors if
    // any of these classes are modified without updating overhead sizes.
  }

  @Test
  public void testHFileBlockSize() throws IOException {
    long expected;
    long actual;

    actual = HFileContext.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(HFileContext.class, false);
    assertEquals(expected, actual);

    actual = HFileBlock.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(HFileBlock.class, false);
    assertEquals(expected, actual);

    actual = ExclusiveMemHFileBlock.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(ExclusiveMemHFileBlock.class, false);
    assertEquals(expected, actual);

    actual = SharedMemHFileBlock.FIXED_OVERHEAD;
    expected = ClassSize.estimateBase(SharedMemHFileBlock.class, false);
    assertEquals(expected, actual);
  }

  @Test
  public void testMutations() {
    Class<?> cl;
    long expected;
    long actual;

    cl = TimeRange.class;
    actual = ClassSize.TIMERANGE;
    expected = ClassSize.estimateBase(cl, false);
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    byte[] row = new byte[] { 0 };
    cl = Put.class;
    actual = Mutation.MUTATION_OVERHEAD + ClassSize.align(ClassSize.ARRAY);
    expected = ClassSize.estimateBase(cl, false);
    // The actual TreeMap is not included in the above calculation
    expected += ClassSize.align(ClassSize.TREEMAP);
    expected += ClassSize.align(ClassSize.INTEGER); // priority
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }

    cl = Delete.class;
    actual = Mutation.MUTATION_OVERHEAD + ClassSize.align(ClassSize.ARRAY);
    expected = ClassSize.estimateBase(cl, false);
    // The actual TreeMap is not included in the above calculation
    expected += ClassSize.align(ClassSize.TREEMAP);
    expected += ClassSize.align(ClassSize.INTEGER); // priority
    if (expected != actual) {
      ClassSize.estimateBase(cl, true);
      assertEquals(expected, actual);
    }
  }

  @Test
  public void testReferenceSize() {
    LOG.info("ClassSize.REFERENCE is " + ClassSize.REFERENCE);
    // oop should be either 4 or 8
    assertTrue(ClassSize.REFERENCE == 4 || ClassSize.REFERENCE == 8);
  }

  @Test
  public void testObjectSize() throws IOException {
    LOG.info("header:" + ClassSize.OBJECT);
    LOG.info("array header:" + ClassSize.ARRAY);

    if (ClassSize.is32BitJVM()) {
      assertEquals(ClassSize.OBJECT, 8);
    } else {
      assertTrue(ClassSize.OBJECT == 12 || ClassSize.OBJECT == 16); // depending on CompressedOops
    }
    if (ClassSize.useUnsafeLayout()) {
      assertEquals(ClassSize.ARRAY, ClassSize.OBJECT + 4);
    } else {
      assertEquals(ClassSize.ARRAY, ClassSize.OBJECT + 8);
    }
  }

  private long calcFixedOverhead(List<Class<?>> classList) {
    long overhead = 0;
    for (Class<?> clazz : classList) {
      overhead += ClassSize.estimateBase(clazz, false);
    }
    return overhead;
  }

  @Test
  public void testAutoCalcFixedOverhead() throws InterruptedException {
    List<Class<?>> classList = Arrays.asList(HFileContext.class, HRegion.class, BlockCacheKey.class,
      HFileBlock.class, HStore.class, LruBlockCache.class, StoreContext.class);
    for (int i = 0; i < 10; i++) {
      // warm up
      calcFixedOverhead(classList);
    }
    long startNs = System.nanoTime();
    long overhead = 0;
    for (int i = 0; i < 100; i++) {
      overhead += calcFixedOverhead(classList);
    }
    long costNs = System.nanoTime() - startNs;
    LOG.info("overhead = {}, cost {} ns", overhead, costNs);
    // the single computation cost should be less than 5ms
    assertThat(costNs, lessThan(TimeUnit.MILLISECONDS.toNanos(5) * classList.size() * 100));
  }
}
