stdupanda/memory-measurer

Automatically exported from code.google.com/p/memory-measurer

ObjectExplorer, by Dimitris Andreou (jim.andreou@gmail.com)

= Introduction =

==[http://memory-measurer.googlecode.com/svn/trunk/dist/javadoc/index.html Javadocs]==

A small tool that is very handy when e.g. you design data structures and want to see how much memory each one uses. To do this, it uses a simple reflection-based object-traversing framework ([http://memory-measurer.googlecode.com/svn/trunk/dist/javadoc/objectexplorer/ObjectExplorer.html ObjectExplorer]). On it, it builds two facilities:

  * [http://memory-measurer.googlecode.com/svn/trunk/dist/javadoc/objectexplorer/MemoryMeasurer.html MemoryMeasurer], which can estimate the memory footprint of an object graph _in bytes_. This requires installing a javaagent when running the JVM, e.g. by passing {{{-javaagent:path/to/object-explorer.jar}}}. 

  * [http://memory-measurer.googlecode.com/svn/trunk/dist/javadoc/objectexplorer/ObjectGraphMeasurer.html ObjectGraphMeasurer] does not need a javaagent, and can also give a much more qualitative measurement than !MemoryMeasurer - it counts the number of objects, references, and primitives (of each kind) that an object graph entails.

Also of interest is the synergy with this project (of yours truly) : [http://code.google.com/p/jbenchy/ JBenchy] 

Put together, they allow you to easily and systematically run and analyze benchmarks regarding data structures.

== How to use ==

An extremely simple example:

{{{
long memory = MemoryMeasurer.measureBytes(new HashMap());
}}}

or

{{{
Footprint footprint = ObjectGraphMeasurer.measure(new HashMap());
}}}

Quick tip: To use the MemoryMeasurer (to measure the footprint of an object
graph in bytes), this parameter needs to be passed to th VM:
-javaagent:path/to/object-explorer.jar