Package io.debezium.util

Class ObjectSizeCalculator

java.lang.Object
io.debezium.util.ObjectSizeCalculator
public class ObjectSizeCalculator extends Object
Contains utility methods for calculating the memory usage of objects. It only works on the HotSpot JVM, and infers the actual memory layout (32 bit vs. 64 bit word size, compressed object pointers vs. uncompressed) from best available indicators. It can reliably detect a 32 bit vs. 64 bit JVM. It can only make an educated guess at whether compressed OOPs are used, though; specifically, it knows what the JVM's default choice of OOP compression would be based on HotSpot version and maximum heap sizes, but if the choice is explicitly overridden with the -XX:{+|-}UseCompressedOops command line switch, it can not detect this fact and will report incorrect sizes, as it will presume the default JVM behavior.
Author:
Attila Szegedi

  • Field Details

    • arrayHeaderSize

      private final int arrayHeaderSize

    • objectHeaderSize

      private final int objectHeaderSize

    • objectPadding

      private final int objectPadding

    • referenceSize

      private final int referenceSize

    • superclassFieldPadding

      private final int superclassFieldPadding

    • classSizeInfos

      private final com.google.common.cache.LoadingCache<Class<?>,ObjectSizeCalculator.ClassSizeInfo> classSizeInfos

    • alreadyVisited

      private final Set<Object> alreadyVisited

    • pending

      private final Deque<Object> pending

    • size

      private long size

  • Constructor Details

    • ObjectSizeCalculator

      public ObjectSizeCalculator(ObjectSizeCalculator.MemoryLayoutSpecification memoryLayoutSpecification)
      Creates an object size calculator that can calculate object sizes for a given memoryLayoutSpecification.
      Parameters:
      memoryLayoutSpecification - a description of the JVM memory layout.

  • Method Details

    • getObjectSize

      public static long getObjectSize(Object obj) throws UnsupportedOperationException
      Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it. Attempts to to detect the current JVM memory layout, but may fail with UnsupportedOperationException;
      Parameters:
      obj - the object; can be null. Passing in a Class object doesn't do anything special, it measures the size of all objects reachable through it (which will include its class loader, and by extension, all other Class objects loaded by the same loader, and all the parent class loaders). It doesn't provide the size of the static fields in the JVM class that the Class object represents.
      Returns:
      the total allocated size of the object and all other objects it retains.
      Throws:
      UnsupportedOperationException - if the current vm memory layout cannot be detected.

    • calculateObjectSize

      public long calculateObjectSize(Object obj)
      Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it.
      Parameters:
      obj - the object; can be null. Passing in a Class object doesn't do anything special, it measures the size of all objects reachable through it (which will include its class loader, and by extension, all other Class objects loaded by the same loader, and all the parent class loaders). It doesn't provide the size of the static fields in the JVM class that the Class object represents.
      Returns:
      the total allocated size of the object and all other objects it retains.

    • visit

      private void visit(Object obj)

    • visitArray

      private void visitArray(Object array)

    • increaseByArraySize

      private void increaseByArraySize(int length, long elementSize)

    • enqueue

      void enqueue(Object obj)

    • increaseSize

      void increaseSize(long objectSize)

    • roundTo

      static long roundTo(long x, int multiple)

    • getPrimitiveFieldSize

      private static long getPrimitiveFieldSize(Class<?> type)

    • getEffectiveMemoryLayoutSpecification

      static ObjectSizeCalculator.MemoryLayoutSpecification getEffectiveMemoryLayoutSpecification()