Currently JacORB does each servant deactivation within a separate thread.
I think this was introduced as fix to bug 204. 

Unfortunately, for bigger numbers of servants, the thread creation and start
results in a huge performance penalty. We have an application that at one time
frees some 4000 servants, at this point the vm crawls, sometimes even gets out
of memory.
(http://lists.spline.inf.fu-berlin.de/pipermail/jacorb-developer/2007-August/009053.html)

I attach a patch that creates only one thread per POA. This thread waits on a
edu.emory.mathcs.backport.java.util.concurrent.LinkedBlockingQueue. In the
remove method the servant data is put onto this queue.

Unfortunately my patch creates a core JacORB dependency on
backport-util-concurrent.jar. I could have used java.util.concurrent but this
creates a dependency on Java 1.5

I have looked for a queue implementation in JacORB core but I did not find one.