benchmarker.py: set cpu frequency governor to "performance" before running tests

btw the command "sudo -s ulimit -n 16384" does nothing; ulimit limits are per-process, and the "ulimit" command is a shell built-in that calls setrlimit(2). when the child shell (started by sudo) executes the ulimit command, it only sets the resource limits for that shell, not the parent shell.

as far as i know, there isn't a way to modify resource limits of another process (other than loading a kernel module, of course), but what you can do is write a shell script that runs as root, sets ulimit, and "su" back to the original user, and then execute the benchmarker