为什么我看到一个进程的 CPU 使用率很高，但总体 CPU 空闲百分比很高？

Question

This is a 8 core machine. The %Cpu(s)->id is 99.4 but one java process already occupies 82.7% cpu usage.

The "top" output is as below:

top - 09:04:09 up 17:22,  1 user,  load average: 0.00, 0.00, 0.00
Tasks: 142 total,   1 running,  74 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.1 us,  0.1 sy,  0.0 ni, 99.4 id,  0.0 wa,  0.0 hi,  0.0 si,  0.3 st
KiB Mem : 62876640 total,  9865752 free, 51971500 used,  1039388 buff/cache
KiB Swap:        0 total,        0 free,        0 used. 10121552 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 4859 root      20   0   50.1g  49.4g 144356 S  82.7 82.4  20:28.62 java
 3847 root      20   0    6452    792    716 S   0.3  0.0   0:09.50 rngd
    1 root      20   0   43724   5680   4196 S   0.0  0.0   0:02.30 systemd
    2 root      20   0       0      0      0 S   0.0  0.0   0:00.01 kthreadd

Answer 1

the answer:

we have cpu = 8 cores

from top we have: process cpu_usage = 82.7% idle = 99.4 % id

look ! lets calculate

8 cores at full usage give = 800%,

so cpu usage % = > [82.7/800] * 100% = 10.3 % (calculated)

cpu idle % = 100-10.3 = 89.7 % (calculated)

well 89.7% kind of slightly different from 99.4% but will give you a flavour

i suppose your main confusion is about 82.7%.

82.7% does not mean 82.7% usage of all the cpu. it would be so if your cpu had 1 core. for multicore cpus 100% usage means that kind of only one core is 100% busy not all the cpu.

Answer 2

您好，这取决于您的使用情况、正在运行的服务或应用程序（eclipse、android studio、JBoss Server 等）检查它们。

Answer 3

Normally the CPU tries to distribute the functions/process between its cores in order to fulfill the multi-tasking. So, the specific process can fetch up the big part of one the cores, however the other cores and the CPU are not handling a huge load.

BR