is the Jboss serialization mechanism producing smaller data output or the performance is only in the algorithm for producing this data.???

It's a little bit of both.

Is there a way to remove the required dependencies.. at least log4j??

The only way would be to use Java trace machanism from Java5 but that would put dependencies on Java 5 and I don't want to avoid that.

the other mechanism would be to not having logging at al (bad) or to use System.out (also bad) or to use any other built in framework (also bad).

We had a discussion thread while ago about this... The best way was to keep log4j.

As for trove is just beause I'm using trove on the objects cache inside JBossObject*Stream. (*=Input/output)

 

The JBossSerialization mechanics also get improvement in use of Externalizable??

When you call writeObject from inside writeExternal methods yes.

Say... if you writeObject(Long) that's going to just call write(Long) (and with an extra objectId to respect the graph of objects.