org.apache.spark.util
Class SizeEstimator

Object
  org.apache.spark.util.SizeEstimator

All Implemented Interfaces:

Logging

public class SizeEstimator
extends Object
implements Logging

:: DeveloperApi :: 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

Constructor Summary

SizeEstimator()

Method Summary

static long

estimate(Object obj) Estimate the number of bytes that the given object takes up on the JVM heap.

Methods inherited from class Object

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

Methods inherited from interface org.apache.spark.Logging

initializeIfNecessary, initializeLogging, isTraceEnabled, log_, log, logDebug, logDebug, logError, logError, logInfo, logInfo, logName, logTrace, logTrace, logWarning, logWarning

Constructor Detail

SizeEstimator

public SizeEstimator()

Method Detail

estimate

public static long estimate(Object obj)

Estimate the number of bytes that the given object takes up on the JVM heap. The estimate includes space taken up by objects referenced by the given object, their references, and so on and so forth.

This is useful for determining the amount of heap space a broadcast variable will occupy on each executor or the amount of space each object will take when caching objects in deserialized form. This is not the same as the serialized size of the object, which will typically be much smaller.

Parameters:

obj - (undocumented)

Returns:

(undocumented)