package com.carrotsearch.sizeof;
/**
* 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.
*/
import java.lang.management.ManagementFactory;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.util.*;
/**
* Estimates the size (memory representation) of Java objects.
*
* @see #sizeOf(Object)
* @see #shallowSizeOf(Object)
* @see #shallowSizeOfInstance(Class)
*/
public final class RamUsageEstimator {
/**
* JVM diagnostic features.
*/
public static enum JvmFeature {
OBJECT_REFERENCE_SIZE("Object reference size estimated using array index scale."),
ARRAY_HEADER_SIZE("Array header size estimated using array based offset."),
FIELD_OFFSETS("Shallow instance size based on field offsets."),
OBJECT_ALIGNMENT("Object alignment retrieved from HotSpotDiagnostic MX bean.");
public final String description;
private JvmFeature(String description) {
this.description = description;
}
@Override
public String toString() {
return super.name() + " (" + description + ")";
}
}
/** JVM info string for debugging and reports. */
public final static String JVM_INFO_STRING;
/** One kilobyte bytes. */
public static final long ONE_KB = 1024;
/** One megabyte bytes. */
public static final long ONE_MB = ONE_KB * ONE_KB;
/** One gigabyte bytes.*/
public static final long ONE_GB = ONE_KB * ONE_MB;
/** No instantiation. */
private RamUsageEstimator() {}
public final static int NUM_BYTES_BOOLEAN = 1;
public final static int NUM_BYTES_BYTE = 1;
public final static int NUM_BYTES_CHAR = 2;
public final static int NUM_BYTES_SHORT = 2;
public final static int NUM_BYTES_INT = 4;
public final static int NUM_BYTES_FLOAT = 4;
public final static int NUM_BYTES_LONG = 8;
public final static int NUM_BYTES_DOUBLE = 8;
/**
* Number of bytes this jvm uses to represent an object reference.
*/
public final static int NUM_BYTES_OBJECT_REF;
/**
* Number of bytes to represent an object header (no fields, no alignments).
*/
public final static int NUM_BYTES_OBJECT_HEADER;
/**
* Number of bytes to represent an array header (no content, but with alignments).
*/
public final static int NUM_BYTES_ARRAY_HEADER;
/**
* A constant specifying the object alignment boundary inside the JVM. Objects will
* always take a full multiple of this constant, possibly wasting some space.
*/
public final static int NUM_BYTES_OBJECT_ALIGNMENT;
/**
* Sizes of primitive classes.
*/
private static final Map<Class<?>,Integer> primitiveSizes;
static {
primitiveSizes = new IdentityHashMap<Class<?>,Integer>();
primitiveSizes.put(boolean.class, NUM_BYTES_BOOLEAN);
primitiveSizes.put(byte.class, NUM_BYTES_BYTE);
primitiveSizes.put(char.class, NUM_BYTES_CHAR);
primitiveSizes.put(short.class, NUM_BYTES_SHORT);
primitiveSizes.put(int.class, NUM_BYTES_INT);
primitiveSizes.put(float.class, NUM_BYTES_FLOAT);
primitiveSizes.put(double.class, NUM_BYTES_DOUBLE);
primitiveSizes.put(long.class, NUM_BYTES_LONG);
}
/**
* A handle to <code>sun.misc.Unsafe</code>.
*/
private final static Object theUnsafe;
/**
* A handle to <code>sun.misc.Unsafe#fieldOffset(Field)</code>.
*/
private final static Method objectFieldOffsetMethod;
/**
* All the supported "internal" JVM features detected at clinit.
*/
private final static EnumSet<JvmFeature> supportedFeatures;
/**
* Initialize constants and try to collect information about the JVM internals.
*/
static {
// Initialize empirically measured defaults. We'll modify them to the current
// JVM settings later on if possible.
int referenceSize = Constants.JRE_IS_64BIT ? 8 : 4;
int objectHeader = Constants.JRE_IS_64BIT ? 16 : 8;
// The following is objectHeader + NUM_BYTES_INT, but aligned (object alignment)
// so on 64 bit JVMs it'll be align(16 + 4, @8) = 24.
int arrayHeader = Constants.JRE_IS_64BIT ? 24 : 12;
supportedFeatures = EnumSet.noneOf(JvmFeature.class);
Class<?> unsafeClass = null;
Object tempTheUnsafe = null;
try {
unsafeClass = Class.forName("sun.misc.Unsafe");
final Field unsafeField = unsafeClass.getDeclaredField("theUnsafe");
unsafeField.setAccessible(true);
tempTheUnsafe = unsafeField.get(null);
} catch (Exception e) {
// Ignore.
}
theUnsafe = tempTheUnsafe;
// get object reference size by getting scale factor of Object[] arrays:
try {
final Method arrayIndexScaleM = unsafeClass.getMethod("arrayIndexScale", Class.class);
referenceSize = ((Number) arrayIndexScaleM.invoke(theUnsafe, Object[].class)).intValue();
supportedFeatures.add(JvmFeature.OBJECT_REFERENCE_SIZE);
} catch (Exception e) {
// ignore.
}
// "best guess" based on reference size. We will attempt to modify
// these to exact values if there is supported infrastructure.
objectHeader = Constants.JRE_IS_64BIT ? (8 + referenceSize) : 8;
arrayHeader = Constants.JRE_IS_64BIT ? (8 + 2 * referenceSize) : 12;
// get the object header size:
// - first try out if the field offsets are not scaled (see warning in Unsafe docs)
// - get the object header size by getting the field offset of the first field of a dummy object
// If the scaling is byte-wise and unsafe is available, enable dynamic size measurement for
// estimateRamUsage().
Method tempObjectFieldOffsetMethod = null;
try {
final Method objectFieldOffsetM = unsafeClass.getMethod("objectFieldOffset", Field.class);
final Field dummy1Field = DummyTwoLongObject.class.getDeclaredField("dummy1");
final int ofs1 = ((Number) objectFieldOffsetM.invoke(theUnsafe, dummy1Field)).intValue();
final Field dummy2Field = DummyTwoLongObject.class.getDeclaredField("dummy2");
final int ofs2 = ((Number) objectFieldOffsetM.invoke(theUnsafe, dummy2Field)).intValue();
if (Math.abs(ofs2 - ofs1) == NUM_BYTES_LONG) {
final Field baseField = DummyOneFieldObject.class.getDeclaredField("base");
objectHeader = ((Number) objectFieldOffsetM.invoke(theUnsafe, baseField)).intValue();
supportedFeatures.add(JvmFeature.FIELD_OFFSETS);
tempObjectFieldOffsetMethod = objectFieldOffsetM;
}
} catch (Exception e) {
// Ignore.
}
objectFieldOffsetMethod = tempObjectFieldOffsetMethod;
// Get the array header size by retrieving the array base offset
// (offset of the first element of an array).
try {
final Method arrayBaseOffsetM = unsafeClass.getMethod("arrayBaseOffset", Class.class);
// we calculate that only for byte[] arrays, it's actually the same for all types:
arrayHeader = ((Number) arrayBaseOffsetM.invoke(theUnsafe, byte[].class)).intValue();
supportedFeatures.add(JvmFeature.ARRAY_HEADER_SIZE);
} catch (Exception e) {
// Ignore.
}
NUM_BYTES_OBJECT_REF = referenceSize;
NUM_BYTES_OBJECT_HEADER = objectHeader;
NUM_BYTES_ARRAY_HEADER = arrayHeader;
// Try to get the object alignment (the default seems to be 8 on Hotspot,
// regardless of the architecture).
int objectAlignment = 8;
try {
final Class<?> beanClazz = Class.forName("com.sun.management.HotSpotDiagnosticMXBean");
// Try to get the diagnostic mxbean without calling {@link ManagementFactory#getPlatformMBeanServer()}
// which starts AWT thread (and shows junk in the dock) on a Mac:
Object hotSpotBean;
// Java 7+, HotSpot
try {
hotSpotBean = ManagementFactory.class
.getMethod("getPlatformMXBean", Class.class)
.invoke(null, beanClazz);
} catch (Exception e1) {
// Java 6, HotSpot
try {
Class<?> sunMF = Class.forName("sun.management.ManagementFactory");
hotSpotBean = sunMF.getMethod("getDiagnosticMXBean").invoke(null);
} catch (Exception e2) {
// Last resort option is an attempt to get it from ManagementFactory's server anyway (may start AWT).
hotSpotBean = ManagementFactory.newPlatformMXBeanProxy(
ManagementFactory.getPlatformMBeanServer(),
"com.sun.management:type=HotSpotDiagnostic", beanClazz);
}
}
if (hotSpotBean != null) {
final Method getVMOptionMethod = beanClazz.getMethod("getVMOption", String.class);
final Object vmOption = getVMOptionMethod.invoke(hotSpotBean, "ObjectAlignmentInBytes");
objectAlignment = Integer.parseInt(
vmOption.getClass().getMethod("getValue").invoke(vmOption).toString());
supportedFeatures.add(JvmFeature.OBJECT_ALIGNMENT);
}
} catch (Exception e) {
// Ignore.
}
NUM_BYTES_OBJECT_ALIGNMENT = objectAlignment;
JVM_INFO_STRING = "[JVM: " +
Constants.JVM_NAME + ", " + Constants.JVM_VERSION + ", " + Constants.JVM_VENDOR + ", " +
Constants.JAVA_VENDOR + ", " + Constants.JAVA_VERSION + "]";
}
/**
* Cached information about a given class.
*/
private static final class ClassCache {
public final long alignedShallowInstanceSize;
public final Field[] referenceFields;
public ClassCache(long alignedShallowInstanceSize, Field[] referenceFields) {
this.alignedShallowInstanceSize = alignedShallowInstanceSize;
this.referenceFields = referenceFields;
}
}
// Object with just one field to determine the object header size by getting the offset of the dummy field:
@SuppressWarnings("unused")
private static final class DummyOneFieldObject {
public byte base;
}
// Another test object for checking, if the difference in offsets of dummy1 and dummy2 is 8 bytes.
// Only then we can be sure that those are real, unscaled offsets:
@SuppressWarnings("unused")
private static final class DummyTwoLongObject {
public long dummy1, dummy2;
}
/**
* Returns true, if the current JVM is fully supported by {@code RamUsageEstimator}.
* If this method returns {@code false} you are maybe using a 3rd party Java VM
* that is not supporting Oracle/Sun private APIs. The memory estimates can be
* imprecise then (no way of detecting compressed references, alignments, etc.).
* Lucene still tries to use sensible defaults.
*/
public static boolean isSupportedJVM() {
return supportedFeatures.size() == JvmFeature.values().length;
}
/**
* Aligns an object size to be the next multiple of {@link #NUM_BYTES_OBJECT_ALIGNMENT}.
*/
public static long alignObjectSize(long size) {
size += (long) NUM_BYTES_OBJECT_ALIGNMENT - 1L;
return size - (size % NUM_BYTES_OBJECT_ALIGNMENT);
}
/** Returns the size in bytes of the byte[] object. */
public static long sizeOf(byte[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + arr.length);
}
/** Returns the size in bytes of the boolean[] object. */
public static long sizeOf(boolean[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + arr.length);
}
/** Returns the size in bytes of the char[] object. */
public static long sizeOf(char[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + (long) NUM_BYTES_CHAR * arr.length);
}
/** Returns the size in bytes of the short[] object. */
public static long sizeOf(short[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + (long) NUM_BYTES_SHORT * arr.length);
}
/** Returns the size in bytes of the int[] object. */
public static long sizeOf(int[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + (long) NUM_BYTES_INT * arr.length);
}
/** Returns the size in bytes of the float[] object. */
public static long sizeOf(float[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + (long) NUM_BYTES_FLOAT * arr.length);
}
/** Returns the size in bytes of the long[] object. */
public static long sizeOf(long[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + (long) NUM_BYTES_LONG * arr.length);
}
/** Returns the size in bytes of the double[] object. */
public static long sizeOf(double[] arr) {
return alignObjectSize((long) NUM_BYTES_ARRAY_HEADER + (long) NUM_BYTES_DOUBLE * arr.length);
}
/**
* Estimates the RAM usage by the given object. It will
* walk the object tree and sum up all referenced objects.
*
* <p><b>Resource Usage:</b> This method internally uses a set of
* every object seen during traversals so it does allocate memory
* (it isn't side-effect free). After the method exits, this memory
* should be GCed.</p>
*/
public static long sizeOf(Object obj) {
ArrayList<Object> stack = new ArrayList<Object>();
stack.add(obj);
return measureSizeOf(stack);
}
/**
* Same as {@link #sizeOf(Object)} but sums up all the arguments. Not an
* overload to prevent accidental parameter conflicts with {@link #sizeOf(Object)}.
*/
public static long sizeOfAll(Object... objects) {
return sizeOfAll(Arrays.asList(objects));
}
/**
* Same as {@link #sizeOf(Object)} but sums up all the arguments. Not an
* overload to prevent accidental parameter conflicts with {@link #sizeOf(Object)}.
*/
public static long sizeOfAll(Iterable<Object> objects) {
final ArrayList<Object> stack;
if (objects instanceof Collection<?>) {
stack = new ArrayList<Object>(((Collection<?>) objects).size());
} else {
stack = new ArrayList<Object>();
}
for (Object o : objects) {
stack.add(o);
}
return measureSizeOf(stack);
}
/**
* Estimates a "shallow" memory usage of the given object. For arrays, this will be the
* memory taken by array storage (no subreferences will be followed). For objects, this
* will be the memory taken by the fields.
*
* JVM object alignments are also applied.
*/
public static long shallowSizeOf(Object obj) {
if (obj == null) return 0;
final Class<?> clz = obj.getClass();
if (clz.isArray()) {
return shallowSizeOfArray(obj);
} else {
return shallowSizeOfInstance(clz);
}
}
/**
* Same as {@link #shallowSizeOf(Object)} but sums up all the arguments. Not an
* overload to prevent accidental parameter conflicts with {@link #shallowSizeOf(Object)}.
*/
public static long shallowSizeOfAll(Object... objects) {
return shallowSizeOfAll(Arrays.asList(objects));
}
/**
* Same as {@link #shallowSizeOf(Object)} but sums up all the arguments. Duplicate
* objects are not resolved and will be counted twice.
* Not an overload to prevent accidental parameter conflicts with
* {@link #shallowSizeOf(Object)}.
*/
public static long shallowSizeOfAll(Iterable<Object> objects) {
long sum = 0;
for (Object o : objects) {
sum += shallowSizeOf(o);
}
return sum;
}
/**
* Returns the shallow instance size in bytes an instance of the given class would occupy.
* This works with all conventional classes and primitive types, but not with arrays
* (the size then depends on the number of elements and varies from object to object).
*
* @see #shallowSizeOf(Object)
* @throws IllegalArgumentException if {@code clazz} is an array class.
*/
public static long shallowSizeOfInstance(Class<?> clazz) {
if (clazz.isArray())
throw new IllegalArgumentException("This method does not work with array classes.");
if (clazz.isPrimitive())
return primitiveSizes.get(clazz);
long size = NUM_BYTES_OBJECT_HEADER;
// Walk type hierarchy
for (;clazz != null; clazz = clazz.getSuperclass()) {
final Field[] fields = clazz.getDeclaredFields();
for (Field f : fields) {
if (!Modifier.isStatic(f.getModifiers())) {
size = adjustForField(size, f);
}
}
}
return alignObjectSize(size);
}
/** Return the set of unsupported JVM features that improve the estimation. */
public static EnumSet<JvmFeature> getUnsupportedFeatures() {
EnumSet<JvmFeature> unsupported = EnumSet.allOf(JvmFeature.class);
unsupported.removeAll(supportedFeatures);
return unsupported;
}
/** Return the set of supported JVM features that improve the estimation. */
public static EnumSet<JvmFeature> getSupportedFeatures() {
return EnumSet.copyOf(supportedFeatures);
}
/**
* Return shallow size of any <code>array</code>.
*/
private static long shallowSizeOfArray(Object array) {
long size = NUM_BYTES_ARRAY_HEADER;
final int len = Array.getLength(array);
if (len > 0) {
Class<?> arrayElementClazz = array.getClass().getComponentType();
if (arrayElementClazz.isPrimitive()) {
size += (long) len * primitiveSizes.get(arrayElementClazz);
} else {
size += (long) NUM_BYTES_OBJECT_REF * len;
}
}
return alignObjectSize(size);
}
/**
* Non-recursive version of object descend. This consumes more memory than recursive in-depth
* traversal but prevents stack overflows on long chains of objects
* or complex graphs (a max. recursion depth on my machine was ~5000 objects linked in a chain
* so not too much).
*
* @param stack Root objects.
*/
private static long measureSizeOf(ArrayList<Object> stack) {
final IdentityHashSet<Object> seen = new IdentityHashSet<Object>();
final IdentityHashMap<Class<?>, ClassCache> classCache = new IdentityHashMap<Class<?>, ClassCache>();
long totalSize = 0;
while (!stack.isEmpty()) {
final Object ob = stack.remove(stack.size() - 1);
if (ob == null || seen.contains(ob)) {
continue;
}
seen.add(ob);
final Class<?> obClazz = ob.getClass();
if (obClazz.isArray()) {
/*
* Consider an array, possibly of primitive types. Push any of its references to
* the processing stack and accumulate this array's shallow size.
*/
long size = NUM_BYTES_ARRAY_HEADER;
final int len = Array.getLength(ob);
if (len > 0) {
Class<?> componentClazz = obClazz.getComponentType();
if (componentClazz.isPrimitive()) {
size += (long) len * primitiveSizes.get(componentClazz);
} else {
size += (long) NUM_BYTES_OBJECT_REF * len;
for (int i = len; --i >= 0 ;) {
final Object o = Array.get(ob, i);
if (o != null && !seen.contains(o)) {
stack.add(o);
}
}
}
}
totalSize += alignObjectSize(size);
} else {
/*
* Consider an object. Push any references it has to the processing stack
* and accumulate this object's shallow size.
*/
try {
ClassCache cachedInfo = classCache.get(obClazz);
if (cachedInfo == null) {
classCache.put(obClazz, cachedInfo = createCacheEntry(obClazz));
}
for (Field f : cachedInfo.referenceFields) {
// Fast path to eliminate redundancies.
final Object o = f.get(ob);
if (o != null && !seen.contains(o)) {
stack.add(o);
}
}
totalSize += cachedInfo.alignedShallowInstanceSize;
} catch (IllegalAccessException e) {
// this should never happen as we enabled setAccessible().
throw new RuntimeException("Reflective field access failed?", e);
}
}
}
// Help the GC.
seen.clear();
stack.clear();
classCache.clear();
return totalSize;
}
/**
* Create a cached information about shallow size and reference fields for
* a given class.
*/
private static ClassCache createCacheEntry(final Class<?> clazz) {
ClassCache cachedInfo;
long shallowInstanceSize = NUM_BYTES_OBJECT_HEADER;
final ArrayList<Field> referenceFields = new ArrayList<Field>(32);
for (Class<?> c = clazz; c != null; c = c.getSuperclass()) {
if (c == Class.class) {
// Prevent inspection of Class' fields, throws SecurityException in Java 9
continue;
}
final Field[] fields = c.getDeclaredFields();
for (final Field f : fields) {
if (!Modifier.isStatic(f.getModifiers())) {
shallowInstanceSize = adjustForField(shallowInstanceSize, f);
if (!f.getType().isPrimitive()) {
f.setAccessible(true);
referenceFields.add(f);
}
}
}
}
cachedInfo = new ClassCache(
alignObjectSize(shallowInstanceSize),
referenceFields.toArray(new Field[referenceFields.size()]));
return cachedInfo;
}
/**
* This method returns the maximum representation size of an object. <code>sizeSoFar</code>
* is the object's size measured so far. <code>f</code> is the field being probed.
*
* <p>The returned offset will be the maximum of whatever was measured so far and
* <code>f</code> field's offset and representation size (unaligned).
*/
private static long adjustForField(long sizeSoFar, final Field f) {
final Class<?> type = f.getType();
final int fsize = type.isPrimitive() ? primitiveSizes.get(type) : NUM_BYTES_OBJECT_REF;
if (objectFieldOffsetMethod != null) {
try {
final long offsetPlusSize =
((Number) objectFieldOffsetMethod.invoke(theUnsafe, f)).longValue() + fsize;
return Math.max(sizeSoFar, offsetPlusSize);
} catch (IllegalAccessException ex) {
throw new RuntimeException("Access problem with sun.misc.Unsafe", ex);
} catch (InvocationTargetException ite) {
final Throwable cause = ite.getCause();
if (cause instanceof RuntimeException)
throw (RuntimeException) cause;
if (cause instanceof Error)
throw (Error) cause;
// this should never happen (Unsafe does not declare
// checked Exceptions for this method), but who knows?
throw new RuntimeException("Call to Unsafe's objectFieldOffset() throwed "+
"checked Exception when accessing field " +
f.getDeclaringClass().getName() + "#" + f.getName(), cause);
}
} else {
// TODO: No alignments based on field type/ subclass fields alignments?
return sizeSoFar + fsize;
}
}
/**
* Returns <code>size</code> in human-readable units (GB, MB, KB or bytes).
*/
public static String humanReadableUnits(long bytes) {
return humanReadableUnits(bytes,
new DecimalFormat("0.#", DecimalFormatSymbols.getInstance(Locale.ENGLISH)));
}
/**
* Returns <code>size</code> in human-readable units (GB, MB, KB or bytes).
*/
public static String humanReadableUnits(long bytes, DecimalFormat df) {
if (bytes / ONE_GB > 0) {
return df.format((float) bytes / ONE_GB) + " GB";
} else if (bytes / ONE_MB > 0) {
return df.format((float) bytes / ONE_MB) + " MB";
} else if (bytes / ONE_KB > 0) {
return df.format((float) bytes / ONE_KB) + " KB";
} else {
return bytes + " bytes";
}
}
/**
* Return a human-readable size of a given object.
* @see #sizeOf(Object)
* @see #humanReadableUnits(long)
*/
public static String humanSizeOf(Object object) {
return humanReadableUnits(sizeOf(object));
}
}