How do I make nodelet manager as fast as the individual nodes?

edit

I have two nodelets that don't talk to each other at all. Neither subscribes to anything that the other publishes. I put them under a shared nodelet manager as the first step of a larger project to integrate them with a third nodelet.

I was surprised to discover that stapling the nodes into a single nodelet manager made them slower overall, even with a really high num_worker_threads.

nodelets.launch:

    <node pkg="nodelet" type="nodelet" name="twin_nodelet_manager" args="manager"> 
        <param name="num_worker_threads" value="32" />
    </node>
    <node pkg="nodelet" type="nodelet" name="tweedledee" args="load wonderland/tweedledee twin_nodelet_manager" />
    <node pkg="nodelet" type="nodelet" name="tweedledum" args="load wonderland/tweedledum twin_nodelet_manager" />

nodes.launch:

    <node pkg="wonderland" type="tweedledee" name="tweedledee" output="screen"/>
    <node pkg="wonderland" type="tweedledum" name="tweedledum" output="screen"/>

Is this consistent with other people's experience? I assume I'm not giving the nodelet manager as much of the computer's resources as I gave the pair of nodes. Is there a way to increase that?

EDIT:

By "not as fast" I mean that the time elapsed during the main callback increased according to std::clock.

void mainCallback(msg) {
  double start = std::clock();
  // do stuff, publish
  double elapsed = ((double)std::clock() - start) / CLOCKS_PER_SEC;
  ROS_INFO_STREAM("elapsed: " << elapsed);
}