通过/proc/stat文件信息,java实现计算cpu使用率
[root@Shentar ~]# cat /proc/stat
cpu 602 0 2164 11445 2294 0 17 0 0
cpu0 306 0 1232 4553 2125 0 15 0 0
cpu1 295 0 932 6891 169 0 1 0 0
intr 7110 269 7 0 1 1 0 5 0 1 0 0 0 91 0 0 106 0 6521 0 108 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
ctxt 38984
btime 1368275792
processes 2713
procs_running 1
procs_blocked 0
[root@Shentar ~]#
第一行的数值表示的是CPU总的使用情况,所以我们只要用第一行的数字计算就可以了。下表解析第一行各数值的含义:
参数 解析(单位:jiffies)
(jiffies是内核中的一个全局变量,用来记录自系统启动一来产生的节拍数,在linux中,一个节拍大致可理解为操作系统进程调度的最小时间片,不同linux内核可能值有不同,通常在1ms到10ms之间)
user (38082) 从系统启动开始累计到当前时刻,处于用户态的运行时间,不包含 nice值为负进程。
nice (627) 从系统启动开始累计到当前时刻,nice值为负的进程所占用的CPU时间
system (27594) 从系统启动开始累计到当前时刻,处于核心态的运行时间
idle (893908) 从系统启动开始累计到当前时刻,除IO等待时间以外的其它等待时间iowait (12256) 从系统启动开始累计到当前时刻,IO等待时间(since 2.5.41)
irq (581) 从系统启动开始累计到当前时刻,硬中断时间(since 2.6.0-test4)
softirq (895) 从系统启动开始累计到当前时刻,软中断时间(since 2.6.0-test4)stealstolen(0) which is the time spent in other operating systems when running in a virtualized environment(since 2.6.11)
guest(0) which is the time spent running a virtual CPU for guest operating systems under the control of the Linux kernel(since 2.6.24)
结论:总的cpu时间totalCpuTime = user + nice + system + idle + iowait + irq + softirq + stealstolen + guest
计算时,采样两个时间点的数据,对于时间点1,记录总的cpu时间total1,记录空闲时间idle1,对于时间2,同样记录total2和idle2。
菜谱使用率为:cpuusage = 1 – (idle2 – idle1) / (total2 – total1)
注意,如果时间点1和时间点2间隔足够小(小于10ms),则可能出现total2 – total1为0,这样cpu使用率应该为0,而不是采用除法计算。
java代码如下:
CPUUsage.java
package com;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class CPUUsage
{
private static final String procPath = File.separator + "proc" + File.separator + "stat";
public static void main(String[] args)
{
CPUTime startTime = new CPUTime();
CPUTime endTime = new CPUTime();
getcpuTime(startTime);
try
{
Thread.sleep(1000);
}
catch (InterruptedException e)
{
e.printStackTrace();
}
getcpuTime(endTime);
double cpuUsage = 0;
long totalTime = endTime.getTotalTime() - startTime.getTotalTime();
if (totalTime == 0)
{
cpuUsage = 0;
}
else
{
cpuUsage = 1 - (((double) (endTime.getIdleTime() - startTime.getIdleTime())) / totalTime);
}
System.out.println("the cpu usage is: " + cpuUsage * 100 + "%");
}
private static void getcpuTime(CPUTime t)
{
BufferedReader fr = null;
try
{
fr = new BufferedReader(new FileReader(new File(procPath)));
String oneLine = null;
while ((oneLine = fr.readLine()) != null)
{
if (oneLine.startsWith("cpu "))
{
String[] vals = oneLine.substring(4).split(" ");
if (vals.length != 10)
{
System.err.println("read an error line string!");
}
else
{
t.setTotalTime(Long.parseLong(vals[1]) + Long.parseLong(vals[2]) + Long.parseLong(vals[3])
+ Long.parseLong(vals[4]) + Long.parseLong(vals[5]) + Long.parseLong(vals[6])
+ Long.parseLong(vals[7]) + Long.parseLong(vals[8]) + Long.parseLong(vals[9]));
t.setIdleTime(Long.parseLong(vals[4]));
break;
}
}
}
}
catch (NumberFormatException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
if (fr != null)
{
try
{
fr.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
}
}
CPUTime.java
package com;
public class CPUTime
{
private long totalTime;
private long idleTime;
public CPUTime()
{
totalTime = 0;
idleTime = 0;
}
public long getTotalTime()
{
return totalTime;
}
public void setTotalTime(long totalTime)
{
this.totalTime = totalTime;
}
public long getIdleTime()
{
return idleTime;
}
public void setIdleTime(long idleTime)
{
this.idleTime = idleTime;
}
}