com.tangosol.net.cache
Class SimpleMemoryCalculator

java.lang.Object
  com.tangosol.util.Base
      com.tangosol.net.cache.SimpleMemoryCalculator

All Implemented Interfaces:

OldCache.UnitCalculator

Direct Known Subclasses:

BinaryMemoryCalculator

public class SimpleMemoryCalculator
extends Base
implements OldCache.UnitCalculator

A UnitCalculator implementation that weighs a cache entry based upon the amount of physical memory (in bytes) required to store the entry.

This implementation can only determine an accurate entry size if both the entry key and value object types are one of the following classes (or an array thereof):

• Object
• Boolean
• Byte
• Character
• Double
• Float
• Integer
• String
• Binary

If either the key or value object is not one of these types, an exception will be thrown during the unit calculation.

Author:

jh 2005.12.20

Field Summary

static Map	MAP_FIXED_SIZES An immutable map of fixed-sized classes to instance size (in bytes).
static int	SIZE_BINARY The minimum size (in bytes) of a Binary object.
static int	SIZE_BOOLEAN The size (in bytes) of a Boolean object.
static int	SIZE_BYTE The size (in bytes) of a Byte object.
static int	SIZE_CHARACTER The size (in bytes) of a Character object.
static int	SIZE_DOUBLE The size (in bytes) of a Double object.
static int	SIZE_ENTRY The minimum size (in bytes) of an LocalCache.Entry object.
static int	SIZE_FLOAT The size (in bytes) of a Float object.
static int	SIZE_INTEGER The size (in bytes) of a Integer object.
static int	SIZE_LONG The size (in bytes) of a Long object.
static int	SIZE_OBJECT The size (in bytes) of an Object.
static int	SIZE_OBJECT_REF The size (in bytes) of an object reference.
static int	SIZE_SHORT The size (in bytes) of a Short object.
static int	SIZE_STRING The minimum size (in bytes) of a String object.

Constructor Summary

SimpleMemoryCalculator()

Method Summary

protected static int	calculateShallowSize(Class clz) Calculate the approximate number of bytes required to store an instance of the given class and its non-static fields in memory.
int	calculateUnits(Object oKey, Object oValue) Calculate a cache cost for the specified cache entry key and value.
static void	main(String[] asArg) Unit test.
protected int	padMemorySize(int cb) Round the given number of bytes to the next closest integer that is divisible by 8.
protected int	sizeOf(Class clz) Determine the minimum number of bytes required to store an instance of the given fixed-sized class in memory.
protected int	sizeOf(Object o) Estimate the number of bytes of memory consumed by the given object.

Field Detail

SIZE_OBJECT_REF

public static final int SIZE_OBJECT_REF

The size (in bytes) of an object reference.

On a 32 bit JVM, an object reference is 4 bytes. On a 64 bit JVM, an object reference is 8 bytes.

SIZE_OBJECT

public static final int SIZE_OBJECT

The size (in bytes) of an Object.

SIZE_BOOLEAN

public static final int SIZE_BOOLEAN

The size (in bytes) of a Boolean object.

SIZE_BYTE

public static final int SIZE_BYTE

The size (in bytes) of a Byte object.

SIZE_SHORT

public static final int SIZE_SHORT

The size (in bytes) of a Short object.

SIZE_CHARACTER

public static final int SIZE_CHARACTER

The size (in bytes) of a Character object.

SIZE_INTEGER

public static final int SIZE_INTEGER

The size (in bytes) of a Integer object.

SIZE_FLOAT

public static final int SIZE_FLOAT

The size (in bytes) of a Float object.

SIZE_LONG

public static final int SIZE_LONG

The size (in bytes) of a Long object.

SIZE_DOUBLE

public static final int SIZE_DOUBLE

The size (in bytes) of a Double object.

SIZE_STRING

public static final int SIZE_STRING

The minimum size (in bytes) of a String object.

SIZE_BINARY

public static final int SIZE_BINARY

The minimum size (in bytes) of a Binary object.

SIZE_ENTRY

public static final int SIZE_ENTRY

The minimum size (in bytes) of an LocalCache.Entry object.

MAP_FIXED_SIZES

public static final Map MAP_FIXED_SIZES

An immutable map of fixed-sized classes to instance size (in bytes).

Constructor Detail

SimpleMemoryCalculator

public SimpleMemoryCalculator()

Method Detail

calculateUnits

public int calculateUnits(Object oKey,
                          Object oValue)

Calculate a cache cost for the specified cache entry key and value.

Specified by:

calculateUnits in interface OldCache.UnitCalculator

Parameters:

oKey - the cache key to evaluate for unit cost

oValue - the cache value to evaluate for unit cost

Returns:

an integer value 0 or greater, with a larger value signifying a higher cost

sizeOf

protected int sizeOf(Object o)

Estimate the number of bytes of memory consumed by the given object.

The calculation is based on the class of the given object:

Class	Size
boolean	1
byte	1
short	2
char	2
int	4
float	4
long	8
double	8
Object	SIZE_OBJECT
Boolean	SIZE_OBJECT + 1
Byte	SIZE_OBJECT + 1
Short	SIZE_OBJECT + 2
Character	SIZE_OBJECT + 2
Integer	SIZE_OBJECT + 4
Float	SIZE_OBJECT + 4
Long	SIZE_OBJECT + 8
Double	SIZE_OBJECT + 8
String	SIZE_STRING + 2*length()
Binary	SIZE_BINARY + length()
isArray()	16 + [element size]*length()

Parameters:

o - the object to measure the size of

Returns:

an estimate of the number of bytes required to store the given object in memory

Throws:

IllegalArgumentException - if the type of the object is not one of the classes listed above

sizeOf

protected int sizeOf(Class clz)

Determine the minimum number of bytes required to store an instance of the given fixed-sized class in memory.

The calculation is based on the following table:

Class	Size
boolean	1
byte	1
short	2
char	2
int	4
float	4
long	8
double	8
Object	SIZE_OBJECT
Boolean	SIZE_OBJECT + 1
Byte	SIZE_OBJECT + 1
Short	SIZE_OBJECT + 2
Character	SIZE_OBJECT + 2
Integer	SIZE_OBJECT + 4
Float	SIZE_OBJECT + 4
Long	SIZE_OBJECT + 8
Double	SIZE_OBJECT + 8

Parameters:

clz - the target class

Returns:

the minimum number of bytes required to store an instance of the given class in memory

Throws:

IllegalArgumentException - if the type of the object is not one of the classes listed above

padMemorySize

protected int padMemorySize(int cb)

Round the given number of bytes to the next closest integer that is divisible by 8.

This method is used to pad the result of a memory calculation assuming that fields are ordered to minimize padding and that allocation granularity is 8 bytes.

Parameters:

cb - the number of bytes to round

Returns:

the input, rounded up to the nearest multiple of 8

calculateShallowSize

protected static int calculateShallowSize(Class clz)

Calculate the approximate number of bytes required to store an instance of the given class and its non-static fields in memory.

The size calculation is shallow, in that fields that are references to variable-sized classes are not included in the estimate.

Parameters:

clz - the target class

Returns:

the number of bytes required to store an instance of the given class, including its non-static members

main

public static void main(String[] asArg)

Unit test.

Usage:

 java com.tangosol.net.cache.SimpleMemoryCalculator [class name]
 

Parameters:

asArg - command line arguments