controling CompositeTaskRunner and DedicatedTaskRunner threads

Hi,

Could you please tell me is there a way to control the number of threads
spawned by activemq?
Basically, we are using IOtransport Configuration. By going through the
pstack, we have many threads for the process. Like:

IOtransport::run(),
TimerImpl::run(),
DedicatedTaskRunner::run(),
CompositeTaskRunner::run() .. etc

As per my understanding, IOtransport threads are used to marshall and
unmarshall the messages.

Do we really need a TimerImpl thread? is there anyway to stop these theads?

Thanks,
Narayana Reddy