Low framerate (30 fps) on Linux (Debian)

[javl]

After quite a struggle I managed to get ofxOpenVR to work. There were a couple of small things I had to change to get it to compile, for example: my system didn't know the functions Sleep() (removed it) and stricmp (replaced it with strcasecmp). I didn't make a pull request as I'm not sure if it is platform dependent or anything like that (but you can see the changes here).

One problem I'm having is that the framerate is quite low (around 30/31 fps). The SteamVR Tutorial seems a little slower than the Windows version as well, but still far above the 30fps. I was wondering if you had any ideas about where to look for bottlenecks in ofxOpenVR, or do you think this is a problem with OpenVR?