Package alluxio.util
Class ObjectSizeCalculator
- java.lang.Object
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- alluxio.util.ObjectSizeCalculator
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public class ObjectSizeCalculator extends java.lang.Object
Contains utility methods for calculating the memory usage of objects. It only works on the HotSpot JVM, and infers the actual memory layout (32 bit vs. 64 bit word size, compressed object pointers vs. uncompressed) from best available indicators. It can reliably detect a 32 bit vs. 64 bit JVM. It can only make an educated guess at whether compressed OOPs are used, though; specifically, it knows what the JVM's default choice of OOP compression would be based on HotSpot version and maximum heap sizes, but if the choice is explicitly overridden with the -XX:{+|-}UseCompressedOops command line switch, it can not detect this fact and will report incorrect sizes, as it will presume the default JVM behavior. Adapted from https://github.com/twitter-archive/commons/blob/master/src/java/com/twitter/common/objectsize/ObjectSizeCalculator.java
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Nested Class Summary
Nested Classes Modifier and Type Class Description static interface
ObjectSizeCalculator.MemoryLayoutSpecification
Describes constant memory overheads for various constructs in a JVM implementation.
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Constructor Summary
Constructors Constructor Description ObjectSizeCalculator(ObjectSizeCalculator calc)
Creates an object size calculator based on a previous one.ObjectSizeCalculator(ObjectSizeCalculator.MemoryLayoutSpecification memoryLayoutSpecification)
Creates an object size calculator that can calculate object sizes for a givenmemoryLayoutSpecification
.ObjectSizeCalculator(ObjectSizeCalculator.MemoryLayoutSpecification memoryLayoutSpecification, java.util.Set<java.lang.Class<?>> constSizeClass)
Creates an object size calculator that can calculate object sizes for a givenmemoryLayoutSpecification
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description long
calculateObjectSize(java.lang.Object obj)
Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it.static long
getObjectSize(java.lang.Object obj)
Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it.static long
getObjectSize(java.lang.Object obj, java.util.Set<java.lang.Class<?>> constantClasses)
Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it.
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Constructor Detail
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ObjectSizeCalculator
public ObjectSizeCalculator(ObjectSizeCalculator.MemoryLayoutSpecification memoryLayoutSpecification)
Creates an object size calculator that can calculate object sizes for a givenmemoryLayoutSpecification
.- Parameters:
memoryLayoutSpecification
- a description of the JVM memory layout
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ObjectSizeCalculator
public ObjectSizeCalculator(ObjectSizeCalculator.MemoryLayoutSpecification memoryLayoutSpecification, java.util.Set<java.lang.Class<?>> constSizeClass)
Creates an object size calculator that can calculate object sizes for a givenmemoryLayoutSpecification
.- Parameters:
memoryLayoutSpecification
- a description of the JVM memory layoutconstSizeClass
- constant sized classes
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ObjectSizeCalculator
public ObjectSizeCalculator(ObjectSizeCalculator calc)
Creates an object size calculator based on a previous one.- Parameters:
calc
- previous calculator
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Method Detail
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getObjectSize
public static long getObjectSize(java.lang.Object obj) throws java.lang.UnsupportedOperationException
Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it. Attempts to to detect the current JVM memory layout, but may fail withUnsupportedOperationException
;- Parameters:
obj
- the object; can be null. Passing in aClass
object doesn't do anything special, it measures the size of all objects reachable through it (which will include its class loader, and by extension, all other Class objects loaded by the same loader, and all the parent class loaders). It doesn't provide the size of the static fields in the JVM class that the Class object represents.- Returns:
- the total allocated size of the object and all other objects it retains
- Throws:
java.lang.UnsupportedOperationException
- if the current vm memory layout cannot be detected
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getObjectSize
public static long getObjectSize(java.lang.Object obj, java.util.Set<java.lang.Class<?>> constantClasses) throws java.lang.UnsupportedOperationException
Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it. Attempts to to detect the current JVM memory layout, but may fail withUnsupportedOperationException
;- Parameters:
obj
- the object; can be nullconstantClasses
- a set of classes that are considered constant sized- Returns:
- the total allocated size of the object and all other objects it
- Throws:
java.lang.UnsupportedOperationException
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calculateObjectSize
public long calculateObjectSize(java.lang.Object obj)
Given an object, returns the total allocated size, in bytes, of the object and all other objects reachable from it.- Parameters:
obj
- the object; can be null. Passing in aClass
object doesn't do anything special, it measures the size of all objects reachable through it (which will include its class loader, and by extension, all other Class objects loaded by the same loader, and all the parent class loaders). It doesn't provide the size of the static fields in the JVM class that the Class object represents.- Returns:
- the total allocated size of the object and all other objects it retains
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