这是一个多次被问过的问题，但是我找不到很好的答案。
许多人建议使用top命令，但是如果你运行top一次（因为你有一个脚本，例如每1秒收集一次Cpu使用），它将始终提供相同的Cpu使用结果（example 1，{ {3}}）。
计算CPU使用率的更准确方法是从/proc/stat读取值，但大多数答案仅使用/proc/stat中的前4个字段来计算它（一个示例{{3 }}）。
/proc/stat/每个CPU核心有10个字段！
我也发现这个example 2问题指出了同样的问题 - 大多数其他问题只考虑了许多领域中的4个问题 - 但这里给出的答案仍然以“我认为”开头（不确定），除此之外，只关注前7个字段（/proc/stat/中的10个字段）
here perl脚本使用所有字段来计算CPU使用率，经过一些进一步的调查后我再次认为这是不正确的。
在快速查看内核代码Accurately Calculating CPU Utilization in Linux using /proc/stat之后，例如，guest_nice和guest fields似乎总是与nice和{{1}一起增加（因此它们不应包含在cpu使用计算中，因为它们已包含在user和nice字段中）
user总而言之，计算Linux中CPU使用率的准确方法是什么？在计算中应考虑哪些字段以及如何（哪些字段归因于空闲时间以及哪些字段归因于非空闲时间）？
答案 0 :(得分：58)
根据撰写本时的htop源代码，我的假设看起来有效：
（请参阅ProcessList.c上的void ProcessList_scan(ProcessList* this)功能）
// Guest time is already accounted in usertime
usertime = usertime - guest; # As you see here, it subtracts guest from user time
nicetime = nicetime - guestnice; # and guest_nice from nice time
// Fields existing on kernels >= 2.6
// (and RHEL's patched kernel 2.4...)
idlealltime = idletime + ioWait; # ioWait is added in the idleTime
systemalltime = systemtime + irq + softIrq;
virtalltime = guest + guestnice;
totaltime = usertime + nicetime + systemalltime + idlealltime + steal + virtalltime;
所以，来自/proc/stat第一行中列出的字段:(参见documentation上的第1.8节）
user nice system idle iowait irq softirq steal guest guest_nice
cpu 74608 2520 24433 1117073 6176 4054 0 0 0 0
在算法上，我们可以计算CPU使用百分比，如：
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
# differentiate: actual value minus the previous one
totald = Total - PrevTotal
idled = Idle - PrevIdle
CPU_Percentage = (totald - idled)/totald
答案 1 :(得分：8)
以下是基于Vangelis的答案的bash脚本。它产生如下输出：
total 49.1803
cpu0 14.2857
cpu1 100
cpu2 28.5714
cpu3 100
cpu4 30
cpu5 25
创建名为get_cpu_usage.sh
使用以下命令运行它：bash get_cpu_usage.sh 0.2
参数是要测量的秒数。在这种情况下，它是200毫秒。
内容如下：
#!/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
答案 2 :(得分：6)
嘿，我也在研究这个主题，发现这个主题非常有用。我使用Vangelis Tasoulas公式为此编写一个小的python脚本。附件是我的问题的Python代码。它每秒加载每个cpu_id的cpu使用量。也许它也有助于其他人。欢迎提出意见/建议： - ）
#!/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")
答案 3 :(得分：1)
idnt.net对如何使用/ proc / stat cpu数据有很好的描述，包括用于提取cpu的bash脚本和行的描述。我只想在这里链接它，因为我发现它很有价值。
答案 4 :(得分：0)
#!/usr/bin/ruby -w
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