Enable custom prefix command from env var

[rwstauner]

I setup my machine with the kernel options to isolate a cpu and then I have a custom script that writes to the necessary files, and I have NOPASSWD sudo commands setup for the commands in that file.

Then I can set this env var to that script and it runs benchmarks specifically configured for my machine with no sudo prompt.

Example script:

#!/bin/bash

# sudoers
# rwstauner ALL= NOPASSWD: /usr/bin/tee /sys/devices/system/cpu/intel_pstate/no_turbo
# rwstauner ALL= NOPASSWD: /usr/bin/tee /sys/devices/system/cpu/intel_pstate/min_perf_pct
# rwstauner ALL= NOPASSWD: /usr/bin/tee /sys/devices/system/cpu/cpu*/online
# rwstauner ALL= NOPASSWD: /usr/bin/renice

# NOTE: add `isolcpus=10,11 nohz_full=10,11` to the options line in /boot/loader conf

cpu=10
sibling=11

sudo () {
  command sudo --bell "$@"
}

teardown () {
  echo 0 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
  echo 8 | sudo tee /sys/devices/system/cpu/intel_pstate/min_perf_pct
  echo 1 | sudo tee /sys/devices/system/cpu/cpu$sibling/online
}

setup () {
  echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
  echo 100 | sudo tee /sys/devices/system/cpu/intel_pstate/min_perf_pct
  echo 0 | sudo tee /sys/devices/system/cpu/cpu$sibling/online
}

setup > /dev/null
trap 'teardown > /dev/null' EXIT

setarch x86_64 -R taskset -c $cpu sh -c 'sudo renice -n -15 "$$" > /dev/null; exec "$@"' - "$@"