Gazebo takes up 1 core when physics is paused

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I'm trying to use gazebo on a fairly old laptop of mine - a core 2 duo with 2 gb ram. I'm using Lubuntu 14.04 (with ROS indigo + gazebo2)

I ran gazebo using gzserver (no GUI) and paused the physics of gazebo and was checking cpu resources on top (a task manager) - No GUI + physics = RAM is less than 500 MB and CPU usage is 100% for both the cores (And cpu temperature rises up to 70s) - No GUI + Paused physics = RAM is less than 500 MB and CPU usage is 100% for 1 core (And cpu temperature for that core rises up to 70s)

Finally, I have 3 questions:

1. Why is gazebo taking up 100% cpu when physics is paused ? Is this expected ?
2. How do I throttle the resources gazebo can take ? I don't want the CPU temperature to go higher than ~60s. Is there a method for me tell gazebo to only work 50% of each core at maximum or something ? (Obviously the simulation will be slower, I don't mind that)
3. Is there any generic way for me to figure out which function in a node is taking up most of the processing power ? How do I profile it ?