It's a good question. rr writes all the state to disk. Every syscall of any kind gets saved and replayed back the same way when you replay the recording. This m

It's a good question. rr writes all the state to disk. Every syscall of any kind gets saved and replayed back the same way when you replay the recording. This means that if your program reads a network packet in the recording, during the replay it will read exactly the same network packet at exactly the same point in it's execution. On the other hand, outputs are not really recorded. During the replay your program will generate exactly the same output, so saving it to disk isn't necessary. See http://rr-project.org/ http://rr-project.org/ for all the details. There's no such thing as a free lunch, so it'll certainly slow your game down a bit. I recommend saving the trace to the fastest disk you can find. Also, you would want to run your game during development both with and without rr, precisely so that you know that you're not exceeding your time budget.