Accurate calculation of CPU usage given in percentage in Linux?

The following is a bash script which is based on Vangelis's answer. It produces output like this:

total 49.1803 cpu0 14.2857 cpu1 100 cpu2 28.5714 cpu3 100 cpu4 30 cpu5 25 

Create a file called get_cpu_usage.sh

Run it using the following command: bash get_cpu_usage.sh 0.2

The argument is the number of seconds to measure. In this case it's 200 milliseconds.

The contents are:

#!/bin/sh sleepDurationSeconds=$1 previousDate=$(date +%s%N | cut -b1-13) previousStats=$(cat /proc/stat) sleep $sleepDurationSeconds currentDate=$(date +%s%N | cut -b1-13) currentStats=$(cat /proc/stat) cpus=$(echo "$currentStats" | grep -P 'cpu' | awk -F " " '{print $1}') for cpu in $cpus do currentLine=$(echo "$currentStats" | grep "$cpu ") user=$(echo "$currentLine" | awk -F " " '{print $2}') nice=$(echo "$currentLine" | awk -F " " '{print $3}') system=$(echo "$currentLine" | awk -F " " '{print $4}') idle=$(echo "$currentLine" | awk -F " " '{print $5}') iowait=$(echo "$currentLine" | awk -F " " '{print $6}') irq=$(echo "$currentLine" | awk -F " " '{print $7}') softirq=$(echo "$currentLine" | awk -F " " '{print $8}') steal=$(echo "$currentLine" | awk -F " " '{print $9}') guest=$(echo "$currentLine" | awk -F " " '{print $10}') guest_nice=$(echo "$currentLine" | awk -F " " '{print $11}') previousLine=$(echo "$previousStats" | grep "$cpu ") prevuser=$(echo "$previousLine" | awk -F " " '{print $2}') prevnice=$(echo "$previousLine" | awk -F " " '{print $3}') prevsystem=$(echo "$previousLine" | awk -F " " '{print $4}') previdle=$(echo "$previousLine" | awk -F " " '{print $5}') previowait=$(echo "$previousLine" | awk -F " " '{print $6}') previrq=$(echo "$previousLine" | awk -F " " '{print $7}') prevsoftirq=$(echo "$previousLine" | awk -F " " '{print $8}') prevsteal=$(echo "$previousLine" | awk -F " " '{print $9}') prevguest=$(echo "$previousLine" | awk -F " " '{print $10}') prevguest_nice=$(echo "$previousLine" | awk -F " " '{print $11}') PrevIdle=$((previdle + previowait)) Idle=$((idle + iowait)) PrevNonIdle=$((prevuser + prevnice + prevsystem + previrq + prevsoftirq + prevsteal)) NonIdle=$((user + nice + system + irq + softirq + steal)) PrevTotal=$((PrevIdle + PrevNonIdle)) Total=$((Idle + NonIdle)) totald=$((Total - PrevTotal)) idled=$((Idle - PrevIdle)) CPU_Percentage=$(awk "BEGIN {print ($totald - $idled)/$totald*100}") if [[ "$cpu" == "cpu" ]]; then echo "total "$CPU_Percentage else echo $cpu" "$CPU_Percentage fi done 

Hey i was also researching for the topic and found this thread really helpful. I used Vangelis Tasoulas formula to write a small python script for this. Attached is my Python code for the issue. It loads the cpu usage per cpu_id every second. Maybe its helps others as well. Also comments/suggestions are welcome :-)

#!/usr/bin/python # -*- coding: utf-8 -*- ''' Created on 04.12.2014 @author: plagtag ''' from time import sleep import sys class GetCpuLoad(object): ''' classdocs ''' def __init__(self, percentage=True, sleeptime = 1): ''' @parent class: GetCpuLoad @date: 04.12.2014 @author: plagtag @info: @param: @return: CPU load in percentage ''' self.percentage = percentage self.cpustat = '/proc/stat' self.sep = ' ' self.sleeptime = sleeptime def getcputime(self): ''' http://stackoverflow.com/questions/23367857/accurate-calculation-of-cpu-usage-given-in-percentage-in-linux read in cpu information from file The meanings of the columns are as follows, from left to right: 0cpuid: number of cpu 1user: normal processes executing in user mode 2nice: niced processes executing in user mode 3system: processes executing in kernel mode 4idle: twiddling thumbs 5iowait: waiting for I/O to complete 6irq: servicing interrupts 7softirq: servicing softirqs #the formulas from htop user nice system idle iowait irq softirq steal guest guest_nice cpu 74608 2520 24433 1117073 6176 4054 0 0 0 0 Idle=idle+iowait NonIdle=user+nice+system+irq+softirq+steal Total=Idle+NonIdle # first line of file for all cpus CPU_Percentage=((Total-PrevTotal)-(Idle-PrevIdle))/(Total-PrevTotal) ''' cpu_infos = {} #collect here the information with open(self.cpustat,'r') as f_stat: lines = [line.split(self.sep) for content in f_stat.readlines() for line in content.split('\n') if line.startswith('cpu')] #compute for every cpu for cpu_line in lines: if '' in cpu_line: cpu_line.remove('')#remove empty elements cpu_line = [cpu_line[0]]+[float(i) for i in cpu_line[1:]]#type casting cpu_id,user,nice,system,idle,iowait,irq,softrig,steal,guest,guest_nice = cpu_line Idle=idle+iowait NonIdle=user+nice+system+irq+softrig+steal Total=Idle+NonIdle #update dictionionary cpu_infos.update({cpu_id:{'total':Total,'idle':Idle}}) return cpu_infos def getcpuload(self): ''' CPU_Percentage=((Total-PrevTotal)-(Idle-PrevIdle))/(Total-PrevTotal) ''' start = self.getcputime() #wait a second sleep(self.sleeptime) stop = self.getcputime() cpu_load = {} for cpu in start: Total = stop[cpu]['total'] PrevTotal = start[cpu]['total'] Idle = stop[cpu]['idle'] PrevIdle = start[cpu]['idle'] CPU_Percentage=((Total-PrevTotal)-(Idle-PrevIdle))/(Total-PrevTotal)*100 cpu_load.update({cpu: CPU_Percentage}) return cpu_load if __name__=='__main__': x = GetCpuLoad() while True: try: data = x.getcpuload() print data except KeyboardInterrupt: sys.exit("Finished") 

idnt.net has a good description for how to use the /proc/stat cpu data, include a bash-script for extracting cpu and description of the lines. I just wanted to link it here, since I found it valuable.

I was also looking for the same. Here is my ruby program based on the Vangelis Tasoulas's answer:

#!/usr/bin/env ruby $VERBOSE = true prev_file = IO.readlines(::File.join('', 'proc', 'stat')).select { |line| line.start_with?('cpu') } Kernel.sleep(0.05) file = IO.readlines(::File.join('', 'proc', 'stat')).select { |line| line.start_with?('cpu') } file.size.times do |i| data, prev_data = file[i].split.map(&:to_f), prev_file[i].split.map(&:to_f) %w(user nice sys idle iowait irq softirq steal).each_with_index do |el, index| eval "@#{el}, @prev_#{el} = #{data[index + 1]}, #{prev_data[index + 1]}" end previdle, idle = @prev_idle + @prev_iowait, @idle + @iowait totald = idle + (@user + @nice + @sys + @irq + @softirq + @steal) - (previdle + (@prev_user + @prev_nice + @prev_sys + @prev_irq + @prev_softirq + @prev_steal)) puts "CPU #{i}: #{((totald - (idle - previdle)) / totald * 100).round(2)} %" end 

The following is a bash script builds on Fidel's answer and arberg's link.

I wanted to lower the usage of cat awk grep and date calls and spend less cpu usage trying to figure out the cpu usage.

Output:

total: 4% cpu0: 10% cpu1: 5% cpu2: 1% cpu3: 1% 

create a bash script using this:

#!/bin/bash # Paramiter one used to set time in sec between reads sleepDurationSeconds=$1 # read cpu stats to arrays readarray -t previousStats < <( awk '/^cpu /{flag=1}/^intr/{flag=0}flag' /proc/stat ) sleep $sleepDurationSeconds readarray -t currentStats < <( awk '/^cpu /{flag=1}/^intr/{flag=0}flag' /proc/stat ) # loop through the arrays for i in "${!previousStats[@]}"; do # Break up arrays 1 line sting into an array element for each item in string previousStat_elemant_array=(${previousStats[i]}) currentStat_elemant_array=(${currentStats[i]}) # Get all columns from user to steal previousStat_colums="${previousStat_elemant_array[@]:1:7}" currentStat_colums="${currentStat_elemant_array[@]:1:7}" # Replace the column seperator (space) with + previous_cpu_sum=$((${previousStat_colums// /+})) current_cpu_sum=$((${currentStat_colums// /+})) # Get the delta between two reads cpu_delta=$((current_cpu_sum - previous_cpu_sum)) # Get the idle time Delta cpu_idle=$((currentStat_elemant_array[4]- previousStat_elemant_array[4])) # Calc time spent working cpu_used=$((cpu_delta - cpu_idle)) # Calc percentage cpu_usage=$((100 * cpu_used / cpu_delta)) # Get cpu used for calc cpu percentage used cpu_used_for_calc="${currentStat_elemant_array[0]}" if [[ "$cpu_used_for_calc" == "cpu" ]]; then echo "total: "$cpu_usage"%" else echo $cpu_used_for_calc": "$cpu_usage"%" fi done