approaches for generating a specific level of cpu utilization

I need to generate a specific level of cpu utilization (as continuous as possible) on an idle machine and am looking for approaches for doing that. An example would be that I want it to run at 50% cpu util for the next 30-minutes. A simple user app that just loops does not do what I need it to because the kernel preempts it. I was thinking of having a loadable module that an app could ioctl to and having the module loop for controllable values. I'm not sure what the side effects are of having the kernel at busy levels for periods of time however. Does this make sense or is there a better way to do this? One issue is that I need top or something else to give me some idea what the cpu loading is to verify that it's doing what I think it is. This could be at the console (run-level 3). This is going to be used for some environmental testing (heat generation) so I don't want the machine doing anything else other than running at some relatively constant controllable cpu utilzation. I'd appreicate any suggestions on ways to do this.

tks LT