MemorySize.java

/*
 * 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.activemq.artemis.utils;

import java.lang.ref.WeakReference;

import org.apache.activemq.artemis.core.client.ActiveMQClientLogger;

public class MemorySize {

   private static final int numberOfObjects = 10000;

   private static Object newObject(final ObjectFactory factory) throws Exception {
      return factory.createObject();
   }

   public static boolean is64bitArch() {
      boolean is64bit = true; // Default to 64 e.g. if can't retrieve property

      try {
         String arch = System.getProperty("os.arch");

         if (arch != null) {
            is64bit = arch.contains("64");
         }
      } catch (Exception e) {
         // Ignore
      }

      return is64bit;
   }

   public interface ObjectFactory {

      Object createObject();
   }

   public static int calculateSize(final ObjectFactory factory) throws Exception {
      final Runtime runtime = Runtime.getRuntime();

      MemorySize.getMemorySize(runtime);

      MemorySize.newObject(factory);

      int i = 0;
      long heap1 = 0;
      long heap2 = 0;
      long totalMemory1 = 0;
      long totalMemory2 = 0;

      // First we do a dry run with twice as many then throw away the results

      Object[] obj = new Object[MemorySize.numberOfObjects * 2];

      for (i = 0; i < MemorySize.numberOfObjects * 2; i++) {
         obj[i] = MemorySize.newObject(factory);
      }

      obj = new Object[MemorySize.numberOfObjects * 2];

      heap1 = MemorySize.getMemorySize(runtime);

      totalMemory1 = runtime.totalMemory();

      for (i = 0; i < MemorySize.numberOfObjects; i++) {
         obj[i] = MemorySize.newObject(factory);
      }

      heap2 = MemorySize.getMemorySize(runtime);

      totalMemory2 = runtime.totalMemory();

      final int size = Math.round((float) (heap2 - heap1) / MemorySize.numberOfObjects);

      if (totalMemory1 != totalMemory2) {
         // throw new IllegalStateException("Warning: JVM allocated more data what would make results invalid " +
         // totalMemory1 + ":" + totalMemory2);

         ActiveMQClientLogger.LOGGER.jvmAllocatedMoreMemory(totalMemory1, totalMemory2);
      }

      return size;
   }

   private static long getMemorySize(final Runtime runtime) {
      for (int i = 0; i < 5; i++) {
         MemorySize.forceGC();
      }
      return runtime.totalMemory() - runtime.freeMemory();
   }

   private static void forceGC() {
      WeakReference<Object> dumbReference = new WeakReference<>(new Object());
      // A loop that will wait GC, using the minimal time as possible
      while (dumbReference.get() != null) {
         System.gc();
         try {
            Thread.sleep(500);
         } catch (InterruptedException e) {
         }
      }
   }

}