/**
* Copyright 2010 The Apache Software Foundation
*
* 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.util;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Properties;
/**
* 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
*/
public class ClassSize {
static final Log LOG = LogFactory.getLog(ClassSize.class);
private static int nrOfRefsPerObj = 2;
/** Array overhead */
public static final int ARRAY;
/** Overhead for ArrayList(0) */
public static final int ARRAYLIST;
/** Overhead for ByteBuffer */
public static final int BYTE_BUFFER;
/** Overhead for an Integer */
public static final int INTEGER;
/** Overhead for entry in map */
public static final int MAP_ENTRY;
/** Object overhead is minimum 2 * reference size (8 bytes on 64-bit) */
public static final int OBJECT;
/** Reference size is 8 bytes on 64-bit, 4 bytes on 32-bit */
public static final int REFERENCE;
/** String overhead */
public static final int STRING;
/** Overhead for TreeMap */
public static final int TREEMAP;
/** Overhead for ConcurrentHashMap */
public static final int CONCURRENT_HASHMAP;
/** Overhead for ConcurrentHashMap.Entry */
public static final int CONCURRENT_HASHMAP_ENTRY;
/** Overhead for ConcurrentHashMap.Segment */
public static final int CONCURRENT_HASHMAP_SEGMENT;
/** Overhead for ConcurrentSkipListMap */
public static final int CONCURRENT_SKIPLISTMAP;
/** Overhead for ConcurrentSkipListMap Entry */
public static final int CONCURRENT_SKIPLISTMAP_ENTRY;
/** Overhead for ReentrantReadWriteLock */
public static final int REENTRANT_LOCK;
/** Overhead for AtomicLong */
public static final int ATOMIC_LONG;
/** Overhead for AtomicInteger */
public static final int ATOMIC_INTEGER;
/** Overhead for AtomicBoolean */
public static final int ATOMIC_BOOLEAN;
/** Overhead for CopyOnWriteArraySet */
public static final int COPYONWRITE_ARRAYSET;
/** Overhead for CopyOnWriteArrayList */
public static final int COPYONWRITE_ARRAYLIST;
private static final String THIRTY_TWO = "32";
/**
* Method for reading the arc settings and setting overheads according
* to 32-bit or 64-bit architecture.
*/
static {
// Figure out whether this is a 32 or 64 bit machine.
Properties sysProps = System.getProperties();
String arcModel = sysProps.getProperty("sun.arch.data.model");
//Default value is set to 8, covering the case when arcModel is unknown
if (arcModel.equals(THIRTY_TWO)) {
REFERENCE = 4;
} else {
REFERENCE = 8;
}
OBJECT = 2 * REFERENCE;
ARRAY = align(3 * REFERENCE);
ARRAYLIST = align(OBJECT + align(REFERENCE) + align(ARRAY) +
(2 * Bytes.SIZEOF_INT));
//noinspection PointlessArithmeticExpression
BYTE_BUFFER = align(OBJECT + align(REFERENCE) + align(ARRAY) +
(5 * Bytes.SIZEOF_INT) +
(3 * Bytes.SIZEOF_BOOLEAN) + Bytes.SIZEOF_LONG);
INTEGER = align(OBJECT + Bytes.SIZEOF_INT);
MAP_ENTRY = align(OBJECT + 5 * REFERENCE + Bytes.SIZEOF_BOOLEAN);
TREEMAP = align(OBJECT + (2 * Bytes.SIZEOF_INT) + align(7 * REFERENCE));
STRING = align(OBJECT + ARRAY + REFERENCE + 3 * Bytes.SIZEOF_INT);
CONCURRENT_HASHMAP = align((2 * Bytes.SIZEOF_INT) + ARRAY +
(6 * REFERENCE) + OBJECT);
CONCURRENT_HASHMAP_ENTRY = align(REFERENCE + OBJECT + (3 * REFERENCE) +
(2 * Bytes.SIZEOF_INT));
CONCURRENT_HASHMAP_SEGMENT = align(REFERENCE + OBJECT +
(3 * Bytes.SIZEOF_INT) + Bytes.SIZEOF_FLOAT + ARRAY);
CONCURRENT_SKIPLISTMAP = align(Bytes.SIZEOF_INT + OBJECT + (8 * REFERENCE));
CONCURRENT_SKIPLISTMAP_ENTRY = align(
align(OBJECT + (3 * REFERENCE)) + /* one node per entry */
align((OBJECT + (3 * REFERENCE))/2)); /* one index per two entries */
REENTRANT_LOCK = align(OBJECT + (3 * REFERENCE));
ATOMIC_LONG = align(OBJECT + Bytes.SIZEOF_LONG);
ATOMIC_INTEGER = align(OBJECT + Bytes.SIZEOF_INT);
ATOMIC_BOOLEAN = align(OBJECT + Bytes.SIZEOF_BOOLEAN);
COPYONWRITE_ARRAYSET = align(OBJECT + REFERENCE);
COPYONWRITE_ARRAYLIST = align(OBJECT + (2 * REFERENCE) + ARRAY);
}
/**
* The estimate of the size of a class instance depends on whether the JVM
* uses 32 or 64 bit addresses, that is it depends on the size of an object
* reference. It is a linear function of the size of a reference, e.g.
* 24 + 5*r where r is the size of a reference (usually 4 or 8 bytes).
*
* This method returns the coefficients of the linear function, e.g. {24, 5}
* in the above example.
*
* @param cl A class whose instance size is to be estimated
* @param debug debug flag
* @return an array of 3 integers. The first integer is the size of the
* primitives, the second the number of arrays and the third the number of
* references.
*/
@SuppressWarnings("unchecked")
private static int [] getSizeCoefficients(Class cl, boolean debug) {
int primitives = 0;
int arrays = 0;
//The number of references that a new object takes
int references = nrOfRefsPerObj;
for ( ; null != cl; cl = cl.getSuperclass()) {
Field[] field = cl.getDeclaredFields();
if (null != field) {
for (Field aField : field) {
if (!Modifier.isStatic(aField.getModifiers())) {
Class fieldClass = aField.getType();
if (fieldClass.isArray()) {
arrays++;
references++;
} else if (!fieldClass.isPrimitive()) {
references++;
} else {// Is simple primitive
String name = fieldClass.getName();
if (name.equals("int") || name.equals("I"))
primitives += Bytes.SIZEOF_INT;
else if (name.equals("long") || name.equals("J"))
primitives += Bytes.SIZEOF_LONG;
else if (name.equals("boolean") || name.equals("Z"))
primitives += Bytes.SIZEOF_BOOLEAN;
else if (name.equals("short") || name.equals("S"))
primitives += Bytes.SIZEOF_SHORT;
else if (name.equals("byte") || name.equals("B"))
primitives += Bytes.SIZEOF_BYTE;
else if (name.equals("char") || name.equals("C"))
primitives += Bytes.SIZEOF_CHAR;
else if (name.equals("float") || name.equals("F"))
primitives += Bytes.SIZEOF_FLOAT;
else if (name.equals("double") || name.equals("D"))
primitives += Bytes.SIZEOF_DOUBLE;
}
if (debug) {
if (LOG.isDebugEnabled()) {
// Write out region name as string and its encoded name.
LOG.debug(aField.getName() + "\n\t" + aField.getType());
}
}
}
}
}
}
return new int [] {primitives, arrays, references};
}
/**
* Estimate the static space taken up by a class instance given the
* coefficients returned by getSizeCoefficients.
*
* @param coeff the coefficients
*
* @param debug debug flag
* @return the size estimate, in bytes
*/
private static long estimateBaseFromCoefficients(int [] coeff, boolean debug) {
long size = coeff[0] + align(coeff[1]*ARRAY) + coeff[2]*REFERENCE;
// Round up to a multiple of 8
size = align(size);
if(debug) {
if (LOG.isDebugEnabled()) {
// Write out region name as string and its encoded name.
LOG.debug("Primitives " + coeff[0] + ", arrays " + coeff[1] +
", references(includes " + nrOfRefsPerObj +
" for object overhead) " + coeff[2] + ", refSize " + REFERENCE +
", size " + size);
}
}
return size;
}
/**
* 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.
*
* @param cl class
* @param debug debug flag
* @return the size estimate in bytes.
*/
@SuppressWarnings("unchecked")
public static long estimateBase(Class cl, boolean debug) {
return estimateBaseFromCoefficients( getSizeCoefficients(cl, debug), debug);
}
/**
* Aligns a number to 8.
* @param num number to align to 8
* @return smallest number >= input that is a multiple of 8
*/
public static int align(int num) {
return (int)(align((long)num));
}
/**
* Aligns a number to 8.
* @param num number to align to 8
* @return smallest number >= input that is a multiple of 8
*/
public static long align(long num) {
//The 7 comes from that the alignSize is 8 which is the number of bytes
//stored and sent together
return ((num + 7) >> 3) << 3;
}
}