准确计算Linux中以百分比给出的CPU使用率？

Question

这是一个被问过很多次的问题，但是我找不到得到充分支持的答案。

很多人建议使用 top 命令，但是如果你运行一次 top（因为你有一个脚本，例如每 1 秒收集一次 Cpu 使用情况）它总是会给出相同的 Cpu 使用结果（example 1，example 2 )。

一种更准确的计算 CPU 使用率的方法是读取来自 /proc/stat 的值，但大多数答案仅使用来自 /proc/stat 的前 4 个字段来计算它（一个示例 here）。

/proc/stat/ 自 Linux 内核 2.6.33 起每个 CPU 内核有 10 个字段！

我还发现了这个Accurately Calculating CPU Utilization in Linux using /proc/stat 问题，它指出了同样的问题——大多数其他问题只考虑了众多领域中的 4 个——但这里给出的答案仍然以“我认为”开头（不确定)，除此之外，它只关注前 7 个字段（/proc/stat/ 中的 10 个字段）

This perl 脚本使用所有字段来计算 CPU 使用率，经过进一步调查，我认为这也是不正确的。

在快速查看内核代码here 后，看起来，例如，guest_nice 和 guest fields 总是与 nice 和 user 一起增加（因此它们不应包含在cpu 使用率计算，因为它们已经包含在 nice 和 user 字段中）

/*
 * Account guest cpu time to a process.
 * @p: the process that the cpu time gets accounted to
 * @cputime: the cpu time spent in virtual machine since the last update
 * @cputime_scaled: cputime scaled by cpu frequency
 */
static void account_guest_time(struct task_struct *p, cputime_t cputime,
                   cputime_t cputime_scaled)
{
    u64 *cpustat = kcpustat_this_cpu->cpustat;

    /* Add guest time to process. */
    p->utime += cputime;
    p->utimescaled += cputime_scaled;
    account_group_user_time(p, cputime);
    p->gtime += cputime;

    /* Add guest time to cpustat. */
    if (task_nice(p) > 0) {
        cpustat[CPUTIME_NICE] += (__force u64) cputime;
        cpustat[CPUTIME_GUEST_NICE] += (__force u64) cputime;
    } else {
        cpustat[CPUTIME_USER] += (__force u64) cputime;
        cpustat[CPUTIME_GUEST] += (__force u64) cputime;
    }
}

所以总结一下，在Linux中计算CPU使用率的准确方法是什么，计算中应该考虑哪些字段以及如何（哪些字段归因于空闲时间，哪些字段归因于非空闲时间）？

Answer 1

根据htop 源代码，我的假设看起来是有效的：

（见static inline double LinuxProcessList_scanCPUTime(LinuxProcessList* this)函数LinuxProcessList.c）

// 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...)
unsigned long long int idlealltime = idletime + ioWait;  # ioWait is added in the idleTime
unsigned long long int systemalltime = systemtime + irq + softIrq;
unsigned long long int virtalltime = guest + guestnice;
unsigned long long int totaltime = usertime + nicetime + systemalltime + idlealltime + steal + virtalltime;

因此，从/proc/stat 第一行中列出的字段中：（请参阅documentation 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

从算法上，我们可以计算出 CPU 使用百分比：

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

Answer 2

以下是基于 Vangelis 回答的 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

创建一个名为get_cpu_usage.sh的文件

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。在本例中为 200 毫秒。

内容是：

#!/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

Answer 3

嘿，我也在研究这个话题，发现这个帖子真的很有帮助。我使用 Vangelis Tasoulas 公式为此编写了一个小 Python 脚本。附件是我的 Python 代码。它每秒加载每个 cpu_id 的 cpu 使用情况。也许它也可以帮助其他人。也欢迎 cmets/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")                

Answer 4

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 脚本和行描述。我只是想在这里链接它，因为我发现它很有价值。

Answer 5

我也在寻找同样的东西。这是我基于 Vangelis Tasoulas 回答的 ruby​​ 程序：

#!/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

Answer 6

以下是基于 Fidel 的回答和 arberg 的链接构建的 bash 脚本。

我想降低 cat awk grep 和 date 调用的使用率，并花费更少的 cpu 使用率来计算 cpu 使用率。

输出：

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

使用这个创建一个 bash 脚本：

#!/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