top

# top
see also:
- htop
- iotop
- iftop

## 示例

![](/media/202108/2021-08-14_224205.png)

## 说明
- 用户 CPU(us)和 Nice CPU(ni)高，说明用户态进程占用了较多的 CPU，所以应该着重排查进程的性能问题

- 系统 CPU(sy)高，说明内核态占用了较多的 CPU所以应该着重排查内核线程或者系统调用的性能问题

- 若 %iowait(wa)的值过高，表示硬盘存在I/O瓶颈；

- 若 %idle(id)的值高但系统响应慢时，有可能是 CPU 等待分配内存，此时应加大内存容量；

- 若 %idle 的值持续低于1，则系统的 CPU 处理能力相对较低，表明系统中最需要解决的资源是 CPU；

## 使用方式
运行top命令后，按h可以查看帮助
```
Help for Interactive Commands - procps-ng version 3.3.10
Window 1:Def: Cumulative mode Off.  System: Delay 3.0 secs; Secure mode Off.

Z,B,E,e   Global: 'Z' colors; 'B' bold; 'E'/'e' summary/task memory scale
  l,t,m     Toggle Summary: 'l' load avg; 't' task/cpu stats; 'm' memory info
  0,1,2,3,I Toggle: '0' zeros; '1/2/3' cpus or numa node views; 'I' Irix mode
  f,F,X     Fields: 'f'/'F' add/remove/order/sort; 'X' increase fixed-width

L,&,<,> . Locate: 'L'/'&' find/again; Move sort column: '<'/'>' left/right
  R,H,V,J . Toggle: 'R' Sort; 'H' Threads; 'V' Forest view; 'J' Num justify
  c,i,S,j . Toggle: 'c' Cmd name/line; 'i' Idle; 'S' Time; 'j' Str justify
  x,y     . Toggle highlights: 'x' sort field; 'y' running tasks
  z,b     . Toggle: 'z' color/mono; 'b' bold/reverse (only if 'x' or 'y')
  u,U,o,O . Filter by: 'u'/'U' effective/any user; 'o'/'O' other criteria
  n,#,^O  . Set: 'n'/'#' max tasks displayed; Show: Ctrl+'O' other filter(s)
  C,...   . Toggle scroll coordinates msg for: up,down,left,right,home,end

k,r       Manipulate tasks: 'k' kill; 'r' renice
  d or s    Set update interval
  W,Y       Write configuration file 'W'; Inspect other output 'Y'
  q         Quit
          ( commands shown with '.' require a visible task display window ) 
Press 'h' or '?' for help with Windows,
Type 'q' or <Esc> to continue
```

### 搜索关键字
运行top后，输入`L`，然后输入关键字，再回车如下：
![](/media/202108/2021-08-15_002744.png)