Get and set the max CPU frequency on FreeBSD / FreeNAS / NAS4Free

cpu-speed

#!/bin/sh
#
# cpu-speed:
#   Requirements - be the root user, FreeBSD 9.2 or higher.
# 
#   Get or set the CPU frequency. This command with no arguments will
#   print the current CPU frequency. CPU may be idling at it's lowest speed.
#
#   This command takes 1 optional argument - new MAX cpu freq (in Mhz).
#   expressed as an integer number. e.g. "cpu 800" - set max freq 800 Mhz.
#   This MAX figure is the new max frequency it is allowed to clock up to.
#
#   Number is rounded off to the nearest allowed frequency multiplier.
#

show_all_cpu_sysctl_settings ()
{
  # Most FreeBSD kernel settings are read-only. Some may look like duplicates.
  # Very few are read-write (so we use powerd). Some CPU settings depend on the CPU family.

  # This command should reveal all the CPU-related key names:
  sysctl -a | grep -i cpu
}

set_cpu_speed ()
{
  # To change the max clock, we must restart the "powerd" rc.d service 
  # with new cmdline arguments. "man powerd" for more information.
  if [ "$(id -u)" = "0" ]; then
    if [ ! "$(grep "cpuspeed" "/etc/rc.conf")" ]; then
      echo "" >> "/etc/rc.conf"
      echo "powerd_enable=\"YES\"" >> "/etc/rc.conf"

      # make the cmdline argument to -M flag a txt substitution with the txt file "/etc/cpuspeed"
      echo "powerd_flags=\"-M \$(cat /etc/cpuspeed)\"" >> "/etc/rc.conf"
    fi

    if [ "$1" ]; then
      # write our new cpu speed to the txt file "/etc/cpuspeed"
      echo "$1" > /etc/cpuspeed
      
      # restart powerd daemon to read the new cpu speed
      /etc/rc.d/powerd restart > /dev/null
    fi
  fi
  
}

print_current_cpu_freq ()
{
  # Report back the current cpu frequency for core "0"
  sysctl dev.cpu.0.freq
}

show_possible_cpu_speeds ()
{
  # Show a list of all possible cpu frequency steps for core "0"
  sysctl dev.cpu.0.freq_levels
}

main ()
{
  set_cpu_speed "$@";
  sleep 1; # give it a chance to update before we check the new value
  print_current_cpu_freq;
  show_possible_cpu_speeds;
}

# Entry point
main "$@"