Use this script to demonstrate the effect of setting all CPUs on a machine to their maximum frequency

freq-ex.rst

#! /usr/bin/python

import time


x = 0
last = time.time()

while True:
    x += 1
    if x % 10000 == 0:
        now = time.time()
        print now - last
        time.sleep(0.100)
        last = time.time()

Use this script to demonstrate the effect of changing the Linux CPU governor from ondemand to performance. While the script is running, set all CPU governors to performance and watch the time drop!

Start by checking the frequencies of all your processors. Note that hyperthreads count as separate processors for this demonstration:

cat /proc/cpuinfo | grep "cpu MHz"

To set processors 0-7 to performance mode, use the command below (requires the cpufrequtils package).

for cpu in `seq 0 7`; do cpufreq-set --cpu $cpu --governor performance; done

Then watch the time for the script to hit 10000 each round, and check your processor frequencies again! The script will run faster and your frequencies will all be higher!

Note to self: I think you can set the governors by echoing "performance" or "ondemand" to /sys/devices/system/cpu/cpuX/cpufreq/scaling_governor (replacing X with the CPU number). This way you don't have to install cpufrequtils.