org.apache.hadoop.hbase.util

Class ClassSize

java.lang.Object

org.apache.hadoop.hbase.util.ClassSize

@InterfaceAudience.Private
public class ClassSize
extends Object

Class for determining the "size" of a class, an attempt to calculate the actual bytes that an object of this class will occupy in memory The core of this class is taken from the Derby project

Field Summary

Fields

Modifier and Type	Field and Description
static int	ARRAY Array overhead
static int	ARRAYLIST Overhead for ArrayList(0)
static int	ATOMIC_BOOLEAN Overhead for AtomicBoolean
static int	ATOMIC_INTEGER Overhead for AtomicInteger
static int	ATOMIC_LONG Overhead for AtomicLong
static int	BYTE_BUFFER Overhead for ByteBuffer
static int	CELL_SKIPLIST_SET Overhead for CellSkipListSet
static int	CONCURRENT_HASHMAP Overhead for ConcurrentHashMap
static int	CONCURRENT_HASHMAP_ENTRY Overhead for ConcurrentHashMap.Entry
static int	CONCURRENT_HASHMAP_SEGMENT Overhead for ConcurrentHashMap.Segment
static int	CONCURRENT_SKIPLISTMAP Overhead for ConcurrentSkipListMap
static int	CONCURRENT_SKIPLISTMAP_ENTRY Overhead for ConcurrentSkipListMap Entry
static int	COPYONWRITE_ARRAYLIST Overhead for CopyOnWriteArrayList
static int	COPYONWRITE_ARRAYSET Overhead for CopyOnWriteArraySet
static int	INTEGER Overhead for an Integer
static int	MAP_ENTRY Overhead for entry in map
static int	OBJECT Object overhead is minimum 2 * reference size (8 bytes on 64-bit)
static int	REENTRANT_LOCK Overhead for ReentrantReadWriteLock
static int	REFERENCE Reference size is 8 bytes on 64-bit, 4 bytes on 32-bit
static int	STRING String overhead
static int	TIMERANGE Overhead for timerange
static int	TIMERANGE_TRACKER Overhead for TimeRangeTracker
static int	TREEMAP Overhead for TreeMap

Constructor Summary

Constructors

Constructor and Description
ClassSize()

Method Summary

Modifier and Type	Method and Description
static int	align(int num) Aligns a number to 8.
static long	align(long num) Aligns a number to 8.
static long	estimateBase(Class cl, boolean debug) Estimate the static space taken up by the fields of a class.
static boolean	is32BitJVM() Determines if we are running in a 32-bit JVM.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ARRAY

public static final int ARRAY

Array overhead

ARRAYLIST

public static final int ARRAYLIST

Overhead for ArrayList(0)

BYTE_BUFFER

public static final int BYTE_BUFFER

Overhead for ByteBuffer

INTEGER

public static final int INTEGER

Overhead for an Integer

MAP_ENTRY

public static final int MAP_ENTRY

Overhead for entry in map

OBJECT

public static final int OBJECT

Object overhead is minimum 2 * reference size (8 bytes on 64-bit)

REFERENCE

public static final int REFERENCE

Reference size is 8 bytes on 64-bit, 4 bytes on 32-bit

STRING

public static final int STRING

String overhead

TREEMAP

public static final int TREEMAP

Overhead for TreeMap

CONCURRENT_HASHMAP

public static final int CONCURRENT_HASHMAP

Overhead for ConcurrentHashMap

CONCURRENT_HASHMAP_ENTRY

public static final int CONCURRENT_HASHMAP_ENTRY

Overhead for ConcurrentHashMap.Entry

CONCURRENT_HASHMAP_SEGMENT

public static final int CONCURRENT_HASHMAP_SEGMENT

Overhead for ConcurrentHashMap.Segment

CONCURRENT_SKIPLISTMAP

public static final int CONCURRENT_SKIPLISTMAP

Overhead for ConcurrentSkipListMap

CONCURRENT_SKIPLISTMAP_ENTRY

public static final int CONCURRENT_SKIPLISTMAP_ENTRY

Overhead for ConcurrentSkipListMap Entry

REENTRANT_LOCK

public static final int REENTRANT_LOCK

Overhead for ReentrantReadWriteLock

ATOMIC_LONG

public static final int ATOMIC_LONG

Overhead for AtomicLong

ATOMIC_INTEGER

public static final int ATOMIC_INTEGER

Overhead for AtomicInteger

ATOMIC_BOOLEAN

public static final int ATOMIC_BOOLEAN

Overhead for AtomicBoolean

COPYONWRITE_ARRAYSET

public static final int COPYONWRITE_ARRAYSET

Overhead for CopyOnWriteArraySet

COPYONWRITE_ARRAYLIST

public static final int COPYONWRITE_ARRAYLIST

Overhead for CopyOnWriteArrayList

TIMERANGE

public static final int TIMERANGE

Overhead for timerange

TIMERANGE_TRACKER

public static final int TIMERANGE_TRACKER

Overhead for TimeRangeTracker

CELL_SKIPLIST_SET

public static final int CELL_SKIPLIST_SET

Overhead for CellSkipListSet

Constructor Detail

ClassSize

public ClassSize()

Method Detail

estimateBase

public static long estimateBase(Class cl,
                                boolean debug)

Estimate the static space taken up by the fields of a class. This includes the space taken up by by references (the pointer) but not by the referenced object. So the estimated size of an array field does not depend on the size of the array. Similarly the size of an object (reference) field does not depend on the object.

Parameters:

cl - class

debug - debug flag

Returns:

the size estimate in bytes.

align

public static int align(int num)

Aligns a number to 8.

Parameters:

num - number to align to 8

Returns:

smallest number >= input that is a multiple of 8

align

public static long align(long num)

Aligns a number to 8.

Parameters:

num - number to align to 8

Returns:

smallest number >= input that is a multiple of 8

is32BitJVM

public static boolean is32BitJVM()

Determines if we are running in a 32-bit JVM. Some unit tests need to know this too.