OpenVZ CPU Calculations

gistfile1.txt

#!/usr/bin/env ruby

require 'fileutils'

def get_freq
  File.readlines('/proc/cpuinfo').each do |line|
    next unless line.match(/^cpu MHz/)
    return line.split(/:/).last.strip.to_f * 1048576
  end
end

def get_stats
  vals = Array.new
  File.readlines('/proc/vz/vestat').each do |line|
    # skip garbage
    next if line.match(/^Version/)
    next if line.match(/^$/)
    next if line.match(/VEID/)
    # headers and vals
    line.gsub!(/\s+/, ' ')
    vals = line.strip.split(/\s/)
  end

  return {:veid => vals[0],
          :user => vals[1],
          :system => vals[3],
          :uptime_jiffies => vals[4],
          :uptime_cycles => vals[7],
          :used => vals[8]}
end

# Calculations:
# jiffies: (user, nice, system, uptime)
#  seconds = measurement / jiffies_per_second
# cycles: (idle, strv, uptime, used, maxlat, totlat, numsched)
#  seconds = measurement / frequency_of_your_cpu

def calc_stats (old_stats, new_stats, freq)
  elapsed_jiffies = new_stats[:uptime_jiffies].to_f - old_stats[:uptime_jiffies].to_f
  elapsed_cycles = new_stats[:uptime_cycles].to_f - old_stats[:uptime_cycles].to_f

  cpu = ((new_stats[:used].to_f - old_stats[:used].to_f) / elapsed_cycles) * 100
  user = ((new_stats[:user].to_f - old_stats[:user].to_f) / elapsed_jiffies) * 100
  system = ((new_stats[:system].to_f - old_stats[:system].to_f) / elapsed_jiffies) * 100

  return {:cpu => cpu, :user => user, :system => system}
end

# load starting data
freq = get_freq
new_stats = get_stats

i = 0

while i < 10 do
  old_stats = new_stats
  new_stats = get_stats

  summary = calc_stats(old_stats, new_stats, freq)
  puts "\n CYCLE #{i}\n-------------"
  puts "CPU Use: #{summary[:cpu]} %"
  puts "User: #{summary[:user]} %"
  puts "System %: #{summary[:system]} %"

  i += 1
  sleep 10
end