Detailed explanation of top command and output results under Linux

The top command is a commonly used performance analysis tool under Linux. It can display the resource usage of each process in the system in real time. It is often used for server-side performance analysis. This article mainly explains the detailed explanation of the top command parameters and the explanation of the output results. I hope it can help everyone. .

top command description

$ top
top - 16:07:37 up 241 days, 20:11, 1 user, load average: 0.96, 1.13, 1.25
Tasks: 231 total,  1 running, 230 sleeping,  0 stopped,  0 zombie
Cpu(s): 12.7%us, 8.4%sy, 0.0%ni, 77.1%id, 0.0%wa, 0.0%hi, 1.8%si, 0.0%st
Mem: 12196436k total, 12056552k used,  139884k free,  64564k buffers
Swap: 2097144k total,  151016k used, 1946128k free, 3120236k cached

PID   USER   PR  NI  VIRT  RES   SHR  S  %CPU  %MEM    TIME+  COMMAND
18411  pplive  20   0 11.9g  7.8g  5372  S 220.2  67.1   16761:00  java
 1875  pplive  20   0 3958m  127m  4564  S  4.6   1.1   12497:35  java
  4  root   20   0   0   0    0  S  0.3   0.0  184:01.76  ksoftirqd/0
  13  root   20   0   0   0    0  S  0.3   0.0  135:49.83  ksoftirqd/2
  25  root   20   0   0   0    0  S  0.3   0.0  136:54.49  ksoftirqd/5

The result of the top command is divided into two parts:

Statistical information: The first five lines are the statistical information of the overall system;
Process information: The table-like area below the statistical information displays the detailed information of each process, which is refreshed every 5 seconds by default.

Statistical information description:

Line 1: Top task queue information (system running status and average load), the same as the uptime command result.
Paragraph 1: The current system time, for example: 16:07:37
Paragraph 2: System running time, the time before restarting. The longer the time, the more stable the system will be.
Format: up xx days, HH:MM
For example: 241 days, 20:11, means it has been running continuously for 241 days, 20 hours and 11 minutes
Paragraph 3: The number of currently logged in users, for example: 1 user , indicating that there is currently only one user logged in
Paragraph 4: System load, that is, the average length of the task queue, the three values ​​​​respectively count the average system load in the last 1, 5, and 15 minutes

Average system load : In the case of a single-core CPU, 0.00 means no load, 1.00 means just full load, more than 1 side means overload, the ideal value is 0.7;
Multi-core CPU load: Number of CPU cores * ideal value 0.7 = ideal load, for example : The 4-core CPU load does not exceed 2.8, which means there is no high load.

Line 2: Tasks process related information
Paragraph 1: Total number of processes, for example: Tasks: 231 total, indicating a total of 231 processes running
Paragraph 2: Number of running processes, For example: 1 running,
Paragraph 3: Number of sleeping processes, for example: 230 sleeping,
Paragraph 4: Number of stopped processes, for example: 0 stopped,
Paragraph 5: Number of zombie processes, For example: 0 zombie

Line 3: Cpus CPU related information. If it is a multi-core CPU, press the number 1 to display the CPU information of each core. At this time, line 1 will be converted to the Cpu core number line, and the number 1 can be switched back and forth. .
Paragraph 1: us user space occupies the CPU percentage, for example: Cpu(s): 12.7%us,
Paragraph 2: sy kernel space occupies the CPU percentage, for example: 8.4%sy,
Paragraph 3 Section: ni The percentage of CPU occupied by processes that have changed priorities in the user process space, for example: 0.0% ni,
Section 4: id The percentage of idle CPU, for example: 77.1% id,
Section 5: wa Waiting The percentage of CPU time for input and output, for example: 0.0% wa,
Paragraph 6: hi The total time spent by the CPU serving hardware interrupts, for example: 0.0% hi,
Paragraph 7: si CPU serving soft interrupts The total time spent, for example: 1.8%si,
Paragraph 8: st Steal time The CPU time stolen by the virtual machine by the hypervisor (if the vm is currently under a hypervisor, the hypervisor actually also consumes part of the CPU processing Time)

Line 4: Mem memory related information (Mem: 12196436k total, 12056552k used, 139884k free, 64564k buffers)
Paragraph 1: Total physical memory, for example: Mem: 12196436k total ,
Paragraph 2: Total amount of physical memory used, for example: 12056552k used,
Paragraph 3: Total amount of free memory, for example: Mem: 139884k free,
Paragraph 4: Used as kernel cache The amount of memory, for example: 64564k buffers

Line 5: Swap swap partition related information (Swap: 2097144k total, 151016k used, 1946128k free, 3120236k cached)
Paragraph 1: Total swap area, For example: Swap: 2097144k total,
Paragraph 2: Total amount of swap area used, for example: 151016k used,
Paragraph 3: Total amount of free swap area, for example: 1946128k free,
Paragraph 4 : Total buffered swap area, 3120236k cached

Process information:
Press f in the top command to view the displayed column information, and press the corresponding letter to turn on/off the column. Capital letters indicate on. Lowercase letters indicate closed. The columns marked with * are the default columns.

A: PID = (Process Id) 进程Id；
E: USER = (User Name) 进程所有者的用户名；
H: PR = (Priority) 优先级
I: NI = (Nice value) nice值。负值表示高优先级，正值表示低优先级
O: VIRT = (Virtual Image (kb)) 进程使用的虚拟内存总量，单位kb。VIRT=SWAP+RES
Q: RES = (Resident size (kb)) 进程使用的、未被换出的物理内存大小，单位kb。RES=CODE+DATA
T: SHR = (Shared Mem size (kb)) 共享内存大小，单位kb
W: S = (Process Status) 进程状态。D=不可中断的睡眠状态,R=运行,S=睡眠,T=跟踪/停止,Z=僵尸进程
K: %CPU = (CPU usage) 上次更新到现在的CPU时间占用百分比
N: %MEM = (Memory usage (RES)) 进程使用的物理内存百分比
M: TIME+ = (CPU Time, hundredths) 进程使用的CPU时间总计，单位1/100秒
b: PPID = (Parent Process Pid) 父进程Id
c: RUSER = (Real user name)
d: UID = (User Id) 进程所有者的用户id
f: GROUP = (Group Name) 进程所有者的组名
g: TTY = (Controlling Tty) 启动进程的终端名。不是从终端启动的进程则显示为 ?
j: P = (Last used cpu (SMP)) 最后使用的CPU，仅在多CPU环境下有意义
p: SWAP = (Swapped size (kb)) 进程使用的虚拟内存中，被换出的大小，单位kb
l: TIME = (CPU Time) 进程使用的CPU时间总计，单位秒
r: CODE = (Code size (kb)) 可执行代码占用的物理内存大小，单位kb
s: DATA = (Data+Stack size (kb)) 可执行代码以外的部分(数据段+栈)占用的物理内存大小，单位kb
u: nFLT = (Page Fault count) 页面错误次数
v: nDRT = (Dirty Pages count) 最后一次写入到现在，被修改过的页面数
y: WCHAN = (Sleeping in Function) 若该进程在睡眠，则显示睡眠中的系统函数名
z: Flags = (Task Flags ) 任务标志，参考 sched.h
X: COMMAND = (Command name/line) 命令名/命令行

top命令选项

-b：以批处理模式操作；
-c：显示完整的治命令；
-d：屏幕刷新间隔时间；
-I：忽略失效过程；
-s：保密模式；
-S：累积模式；
-i：设置间隔时间；
-u：指定用户名；
-p：指定进程；
-n：循环显示的次数。

top命令交互

常用交互操作

基础操作

1：显示CPU详细信息，每核显示一行
d / s ：修改刷新频率，单位为秒
h：可显示帮助界面
n：指定进程列表显示行数，默认为满屏行数
q：退出top

面板隐藏显示

l：隐藏/显示第1行负载信息；
t：隐藏/显示第2~3行CPU信息；
m：隐藏/显示第4~5行内存信息；

进程列表排序

M：根据驻留内存大小进行排序；
P：根据CPU使用百分比大小进行排序；
T：根据时间/累计时间进行排序；

详细交互指令：h / ? 可显示帮助界面，原始为英文版，简单翻译如下：

Help for Interactive Commands - procps version 3.2.8
Window 1:Def: Cumulative mode Off. System: Delay 3.0 secs; Secure mode Off.

 Z,B    Global: 'Z' change color mappings; 'B' disable/enable bold
      Z：修改颜色配置；B：关闭/开启粗体
 l,t,m   Toggle Summaries: 'l' load avg; 't' task/cpu stats; 'm' mem info
      l：隐藏/显示第1行负载信息；t：隐藏/显示第2~3行CPU信息；m：隐藏/显示第4~5行内存信息；
 1,I    Toggle SMP view: '1' single/separate states; 'I' Irix/Solaris mode
      1：单行/多行显示CPU信息；I：Irix/Solaris模式切换
 f,o   . Fields/Columns: 'f' add or remove; 'o' change display order
      f：列显示控制；o：列排序控制，按字母进行调整
 F or O . Select sort field 选择排序列
    . Move sort field: '' next col right 上下移动内容
 R,H   . Toggle: 'R' normal/reverse sort; 'H' show threads
      R：内容排序；H：显示线程
 c,i,S  . Toggle: 'c' cmd name/line; 'i' idle tasks; 'S' cumulative time
      c：COMMAND列命令名称与完整命令行路径切换；i：忽略闲置和僵死进程开关；S：累计模式切换
 x,y   . Toggle highlights: 'x' sort field; 'y' running tasks
      x：列排序；y：运行任务
 z,b   . Toggle: 'z' color/mono; 'b' bold/reverse (only if 'x' or 'y')
      z：颜色模式；b：粗体开关 仅适用于x，y模式中
 u    . Show specific user only 按用户进行过滤，当输入错误可按Ctrl + Backspace进行删除
 n or # . Set maximum tasks displayed 设置进程最大显示条数

 k,r    Manipulate tasks: 'k' kill; 'r' renice
      k：终止一个进程；r：重新设置一个进程的优先级别
 d or s  Set update interval 改变两次刷新之间的延迟时间（单位为s），如果有小数，就换算成ms。输入0值则系统将不断刷新，默认值是5s；
 W     Write configuration file 将当前设置写入~/.toprc文件中
 q     Quit    退出
     ( commands shown with '.' require a visible task display window )
      注意：带.的命令需要一个可见的任务显示窗口

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