tf::MessageFilter CPU usage / clean up problem

[conqualifaction]

The following code creates additional CPU usage if "testMethod" is called. The problem seems to be connected to the creation of MessageFilter. This can be tested by removing the MessageFilter creation code line.

The additional CPU usage is 4 % on my system.
I could not find a way to clean up in a way to avoid this (e.g. call clear(), unsubscribe(), etc. have no effect).

Tested on ROS Indigo.

#include <ros/ros.h>
#include <image_transport/image_transport.h>
#include <tf/transform_listener.h>
#include <tf/message_filter.h>
#include <message_filters/subscriber.h>

void testMethod(ros::NodeHandle node)
{
  tf::TransformListener tf_listener(node, ros::Duration(40));
  message_filters::Subscriber<sensor_msgs::Image> img_subscriber(node, "/topic", 400);
  tf::MessageFilter<sensor_msgs::Image> msg_filter(img_subscriber, tf_listener, "/frame", 400);
}

int main(int argc, char** argv)
{
  ros::init(argc, argv, "test_node");
  ros::NodeHandle node;

  testMethod(node);

  ROS_INFO("Going to spin...");
  ros::spin();
  return 0;
}

[tfoote]

I tried running the code and don't see any noticeable load.

Checking it's state while spinning I see only the basic systems:

$ rosnode info test_node
--------------------------------------------------------------------------------
Node [/test_node]
Publications: 
 * /rosout [rosgraph_msgs/Log]

Subscriptions: None

Services: 
 * /test_node/get_loggers
 * /test_node/set_logger_level


contacting node http://snowman:44688/ ...
Pid: 17454
Connections:
 * topic: /rosout
    * to: /rosout
    * direction: outbound
    * transport: TCPROS

Can you provide more context or an example of the rest of the system that would trigger this behavior? Might you be forcing this program into and out of swap or something else to trigger a load due to memory exhaustion?