Possibility of Controller Overload using Compressor

[apalrd]

Hello. If you have had any of the problems I have had, you probably keep a scribe close to hit the No App switch every time you download. Looking deep into the WPI library for possible causes of CPU overload, I found this.

The Compressor library opens a new thread to handle compressor updates. Kinda a weird thing to do, since it could just poll the compressor during every loop of Teleop or something, but it does. It uses FIFO to transfer enabled state between the main thread and the Compressor thread. The compressor thread has no delays - an infinite loop that reads the FIFO, reads the switch, and sets the relay. I don't know much about how FIFO operates, but I assume it dosen't take long to read the FIFO. I do know it dosen't take long to read a switch or set a relay. Thus, it is quite possible that all extra CPU power is dedicated to running the compressor as fast as possible, so it would be really really hard to tell if optimizations work, as the processor is always around 95% since the compressor is always eating the extra.

The solution is simple. I added a 100ms delay to the Compressor loop. After doing this, the CPU load on my cRio went from 96% to 56%. Drastic improvement. I can't certainly say it was this compressor, as I was trying desperately to get the drive lag to go away.