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/*
* 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 spark
import java.lang.reflect.Field
import java.lang.reflect.Modifier
import java.lang.reflect.{Array => JArray}
import java.util.IdentityHashMap
import java.util.concurrent.ConcurrentHashMap
import java.util.Random
import javax.management.MBeanServer
import java.lang.management.ManagementFactory
import scala.collection.mutable.ArrayBuffer
import it.unimi.dsi.fastutil.ints.IntOpenHashSet
/**
* Estimates the sizes of Java objects (number of bytes of memory they occupy), for use in
* memory-aware caches.
*
* Based on the following JavaWorld article:
* http://www.javaworld.com/javaworld/javaqa/2003-12/02-qa-1226-sizeof.html
*/
private[spark] object SizeEstimator extends Logging {
// Sizes of primitive types
private val BYTE_SIZE = 1
private val BOOLEAN_SIZE = 1
private val CHAR_SIZE = 2
private val SHORT_SIZE = 2
private val INT_SIZE = 4
private val LONG_SIZE = 8
private val FLOAT_SIZE = 4
private val DOUBLE_SIZE = 8
// Alignment boundary for objects
// TODO: Is this arch dependent ?
private val ALIGN_SIZE = 8
// A cache of ClassInfo objects for each class
private val classInfos = new ConcurrentHashMap[Class[_], ClassInfo]
// Object and pointer sizes are arch dependent
private var is64bit = false
// Size of an object reference
// Based on https://wikis.oracle.com/display/HotSpotInternals/CompressedOops
private var isCompressedOops = false
private var pointerSize = 4
// Minimum size of a java.lang.Object
private var objectSize = 8
initialize()
// Sets object size, pointer size based on architecture and CompressedOops settings
// from the JVM.
private def initialize() {
is64bit = System.getProperty("os.arch").contains("64")
isCompressedOops = getIsCompressedOops
objectSize = if (!is64bit) 8 else {
if(!isCompressedOops) {
16
} else {
12
}
}
pointerSize = if (is64bit && !isCompressedOops) 8 else 4
classInfos.clear()
classInfos.put(classOf[Object], new ClassInfo(objectSize, Nil))
}
private def getIsCompressedOops : Boolean = {
if (System.getProperty("spark.test.useCompressedOops") != null) {
return System.getProperty("spark.test.useCompressedOops").toBoolean
}
try {
val hotSpotMBeanName = "com.sun.management:type=HotSpotDiagnostic"
val server = ManagementFactory.getPlatformMBeanServer()
// NOTE: This should throw an exception in non-Sun JVMs
val hotSpotMBeanClass = Class.forName("com.sun.management.HotSpotDiagnosticMXBean")
val getVMMethod = hotSpotMBeanClass.getDeclaredMethod("getVMOption",
Class.forName("java.lang.String"))
val bean = ManagementFactory.newPlatformMXBeanProxy(server,
hotSpotMBeanName, hotSpotMBeanClass)
// TODO: We could use reflection on the VMOption returned ?
return getVMMethod.invoke(bean, "UseCompressedOops").toString.contains("true")
} catch {
case e: Exception => {
// Guess whether they've enabled UseCompressedOops based on whether maxMemory < 32 GB
val guess = Runtime.getRuntime.maxMemory < (32L*1024*1024*1024)
val guessInWords = if (guess) "yes" else "not"
logWarning("Failed to check whether UseCompressedOops is set; assuming " + guessInWords)
return guess
}
}
}
/**
* The state of an ongoing size estimation. Contains a stack of objects to visit as well as an
* IdentityHashMap of visited objects, and provides utility methods for enqueueing new objects
* to visit.
*/
private class SearchState(val visited: IdentityHashMap[AnyRef, AnyRef]) {
val stack = new ArrayBuffer[AnyRef]
var size = 0L
def enqueue(obj: AnyRef) {
if (obj != null && !visited.containsKey(obj)) {
visited.put(obj, null)
stack += obj
}
}
def isFinished(): Boolean = stack.isEmpty
def dequeue(): AnyRef = {
val elem = stack.last
stack.trimEnd(1)
return elem
}
}
/**
* Cached information about each class. We remember two things: the "shell size" of the class
* (size of all non-static fields plus the java.lang.Object size), and any fields that are
* pointers to objects.
*/
private class ClassInfo(
val shellSize: Long,
val pointerFields: List[Field]) {}
def estimate(obj: AnyRef): Long = estimate(obj, new IdentityHashMap[AnyRef, AnyRef])
private def estimate(obj: AnyRef, visited: IdentityHashMap[AnyRef, AnyRef]): Long = {
val state = new SearchState(visited)
state.enqueue(obj)
while (!state.isFinished) {
visitSingleObject(state.dequeue(), state)
}
return state.size
}
private def visitSingleObject(obj: AnyRef, state: SearchState) {
val cls = obj.getClass
if (cls.isArray) {
visitArray(obj, cls, state)
} else if (obj.isInstanceOf[ClassLoader] || obj.isInstanceOf[Class[_]]) {
// Hadoop JobConfs created in the interpreter have a ClassLoader, which greatly confuses
// the size estimator since it references the whole REPL. Do nothing in this case. In
// general all ClassLoaders and Classes will be shared between objects anyway.
} else {
val classInfo = getClassInfo(cls)
state.size += classInfo.shellSize
for (field <- classInfo.pointerFields) {
state.enqueue(field.get(obj))
}
}
}
// Estimat the size of arrays larger than ARRAY_SIZE_FOR_SAMPLING by sampling.
private val ARRAY_SIZE_FOR_SAMPLING = 200
private val ARRAY_SAMPLE_SIZE = 100 // should be lower than ARRAY_SIZE_FOR_SAMPLING
private def visitArray(array: AnyRef, cls: Class[_], state: SearchState) {
val length = JArray.getLength(array)
val elementClass = cls.getComponentType
// Arrays have object header and length field which is an integer
var arrSize: Long = alignSize(objectSize + INT_SIZE)
if (elementClass.isPrimitive) {
arrSize += alignSize(length * primitiveSize(elementClass))
state.size += arrSize
} else {
arrSize += alignSize(length * pointerSize)
state.size += arrSize
if (length <= ARRAY_SIZE_FOR_SAMPLING) {
for (i <- 0 until length) {
state.enqueue(JArray.get(array, i))
}
} else {
// Estimate the size of a large array by sampling elements without replacement.
var size = 0.0
val rand = new Random(42)
val drawn = new IntOpenHashSet(ARRAY_SAMPLE_SIZE)
for (i <- 0 until ARRAY_SAMPLE_SIZE) {
var index = 0
do {
index = rand.nextInt(length)
} while (drawn.contains(index))
drawn.add(index)
val elem = JArray.get(array, index)
size += SizeEstimator.estimate(elem, state.visited)
}
state.size += ((length / (ARRAY_SAMPLE_SIZE * 1.0)) * size).toLong
}
}
}
private def primitiveSize(cls: Class[_]): Long = {
if (cls == classOf[Byte])
BYTE_SIZE
else if (cls == classOf[Boolean])
BOOLEAN_SIZE
else if (cls == classOf[Char])
CHAR_SIZE
else if (cls == classOf[Short])
SHORT_SIZE
else if (cls == classOf[Int])
INT_SIZE
else if (cls == classOf[Long])
LONG_SIZE
else if (cls == classOf[Float])
FLOAT_SIZE
else if (cls == classOf[Double])
DOUBLE_SIZE
else throw new IllegalArgumentException(
"Non-primitive class " + cls + " passed to primitiveSize()")
}
/**
* Get or compute the ClassInfo for a given class.
*/
private def getClassInfo(cls: Class[_]): ClassInfo = {
// Check whether we've already cached a ClassInfo for this class
val info = classInfos.get(cls)
if (info != null) {
return info
}
val parent = getClassInfo(cls.getSuperclass)
var shellSize = parent.shellSize
var pointerFields = parent.pointerFields
for (field <- cls.getDeclaredFields) {
if (!Modifier.isStatic(field.getModifiers)) {
val fieldClass = field.getType
if (fieldClass.isPrimitive) {
shellSize += primitiveSize(fieldClass)
} else {
field.setAccessible(true) // Enable future get()'s on this field
shellSize += pointerSize
pointerFields = field :: pointerFields
}
}
}
shellSize = alignSize(shellSize)
// Create and cache a new ClassInfo
val newInfo = new ClassInfo(shellSize, pointerFields)
classInfos.put(cls, newInfo)
return newInfo
}
private def alignSize(size: Long): Long = {
val rem = size % ALIGN_SIZE
return if (rem == 0) size else (size + ALIGN_SIZE - rem)
}
}
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