Hi, I just committed a new toy for Wicket. wicket.util.Objects now uses a simple strategy class to delegate calculating object sizes for method sizeOf (which is used in various places in Wicket, e.g. in the inspector bug). As an alternative implementation, I added project wicket-objectsizeof-agent, which only lives in the 1.3 branch, but should work just as well for 2.0. To use this, make a jar using mvn clean install (or get a snapshot from bamboo when it's available) and start up your application providing a -javaagent argument that points to the resulting jar. For instance, I used for my computer: -javaagent:/Users/eelcohillenius/.m2/repository/org/apache/wicket/wicket-objectsizeof-agent/1.3-incubating-SNAPSHOT/wicket-objectsizeof-agent-1.3-incubating-SNAPSHOT.jar
The instrumentation class will take care for pluggin in the strategy, so besides providing that parameter there is nothing you need to do. The calculation is based on counting the objects that would be serialized when using Java's default serialization. This is similar to what we did before, but now it counts using the instrumentation class rather than the bytes. This should eliminate bytes for class headers etc (which aren't very useful in the calculation) but otoh adds some of the overhead of the JVM you wouldn't have when serializing. I don't know, it still seems pretty tricky to get good memory measurements of isolated objects. I hope more people ditch in here and think with us/ tweak/ test to get this as accurate as we can. So... please play with it and give feedback here. Oh, it's JDK 5+ only, and if you are using JDK 6+ you can even attach the agent dynamically to a running JVM (though at this time there is no facility for detaching... patches are welcome). Cheers, Eelco
