For example - if I create a ByteBuffer and pack it with ints and my architecture does specific things with byte alignment, what does the VM do.
Nothing to my knowledge. The VM lays down data byte by byte according to the Java spec. You need to format
the data yourself if you are handing it to hardware that needs a given format.
How are objects created and destroyed with autoboxing - what's going on beneath the covers in the virtual machine.
Nothing. Thsi is purely a compiler thing. Syntactic sugar.
When I make a call to a JNI function that creates object, how is this different than if they were created in my native Java code.
Its the same code underneath. The only issues being those of locking as with any JNI manipultion of Java objects.
If I wanted to create lots of short lived objects yet have a large eden space (because maybe I do lots of operations that require object instantiation for some reason), why are the pause times growing since those objects should pretty much be going away immediately.
Got me, Id need to see some numbers and the test and we could run it by the VM guys.
Is there a way to organize collections such that the objects you put in collections can set in the young generation longer even though the collection itself may be tenured.
The young generation gets celaned up when the eden fills. You can increase the eden size with command line parameters. The flip side is that the bigger the eden the more it may have to potentially moe when an eden clean DOES happen.
The VM itself also adjusts the eden size on the fly trying to maintaina good balance. Im not sure if there are tweakable nobs on that, like there are in the -XX flags but also likely they're meanings ae nto intuitively obious. Again I can ask the Vm guys for mreo info if you want.
How do I configure all of these performance operations in webstart or in a Java applet.
Can't yet. They are working on adding command line flag support to Webstart. Applets rally have no place to add that
I could sit all day with someone while trying to do performance tuning and ask a million questions even though I've read through the available materials.
Well, ask them here and I'l ltry to find answers wher I cna. Also, if you can get to JavaOne, the BOF sessions are great for questions like this because you get direct access to the developers.
In particulqr we are going to have game BOF at JavaOne. If you guys would like to giv eme a list of the grousp you'ld like to see ther to answer questions I can try to twist some arms into showing up