Linux top命令

top类似windows任务管理器，展示进程任务信息，还有cpu、memory、swap等统计信息

--1.查看版本信息
[oracle@hgora11g ~]$ top -v
	top: procps version 3.2.8
usage:	top -hv | -abcHimMsS -d delay -n iterations [-u user | -U user] -p pid [,pid ...]

--2.默认显示信息，按%CPU列排序
[oracle@hgora11g ~]$ top
top - 16:29:13 up 238 days,  6:12,  6 users,  load average: 0.01, 0.06, 0.03
Tasks: 496 total,   1 running, 494 sleeping,   1 stopped,   0 zombie
Cpu(s):  0.3%us,  0.2%sy,  0.0%ni, 99.5%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  16335768k total, 15555392k used,   780376k free,   292632k buffers
Swap:  8241144k total,   476180k used,  7764964k free, 12907104k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                                                              
10620 oracle    -2   0 5037m  14m  14m S  1.7  0.1   3866:23 oracle                                                                                                                
10630 oracle    20   0 5048m  76m  68m S  0.7  0.5   1065:37 oracle                                                                                                                
27137 oracle    20   0 15304 1556  944 R  0.7  0.0   0:00.30 top                                                                                                                   
   36 root      20   0     0    0    0 S  0.3  0.0  14:48.67 events/1

--3.按内存使用排序
[oracle@hgora11g ~]$ top -a

--4.页面刷新时间，单位为秒
[oracle@hgora11g ~]$ top -d 5 

--5.不显示idle进程
[oracle@hgora11g ~]$ top -i
或者top后按i键

--6.VIRT/USED toggle，Reports USED (sum of process rss and swap total count) instead of VIRT
[oracle@hgora11g ~]$ top -m

--7.内存信息用(k/M/G)展示
[oracle@hgora11g ~]$ top -M
Mem:    15.579G total,   14.856G used,  740.629M free,  286.508M buffers
Swap: 8047.992M total,  465.020M used, 7582.973M free,   12.311G cached

--8.指定页面刷新次数
[oracle@hgora11g ~]$ top -n 5

--9.指定进程id,可以逗号分隔
[oracle@hgora11g ~]$ top -p 26835,28447

--10.-S : Cumulative time mode toggle
Starts top with the last remembered ’S’ state reversed.  When ’Cumulative mode’ is On, 
each process is listed with the cpu time that it and its  dead children have used.  
See the ’S’ interactive command for additional information regarding this mode.

--11.指定用户
[oracle@hgora11g ~]$ top -u oracle

 2. FIELDS / Columns
   2a. DESCRIPTIONS of Fields
       Listed  below  are top’s available fields.  They are always associated with the letter shown, regardless of the position 
       you may have established for them with the ’o’ (Order fields) interactive command.

       Any field is selectable as the sort field, and you control whether they are sorted high-to-low or low-to-high.  
       For additional information on sort  provi-sions see topic 3c. TASK Area Commands.

       a: PID  --  Process Id
          The task’s unique process ID, which periodically wraps, though never restarting at zero.

       b: PPID  --  Parent Process Pid
          The process ID of a task’s parent.

       c: RUSER  --  Real User Name
          The real user name of the task’s owner.

       d: UID  --  User Id
          The effective user ID of the task’s owner.

       e: USER  --  User Name
          The effective user name of the task’s owner.

       f: GROUP  --  Group Name
          The effective group name of the task’s owner.

       g: TTY  --  Controlling Tty
          The  name  of  the controlling terminal.  This is usually the device (serial port, pty, etc.) from which the process 
          was started, and which it uses for input or output.  
          However, a task need not be associated with a terminal, in which case you’ll see ’?’ displayed.
       
       h: PR  --  Priority
          The priority of the task.

       i: NI  --  Nice value
          The nice value of the task.  A negative nice value means higher priority, whereas a positive nice value means lower 
          priority.  
          Zero in this field  simply means priority will not be adjusted in determining a task’s dispatchability.

       j: P  --  Last used CPU (SMP)
          A  number  representing the last used processor.  In a true SMP environment this will likely change frequently since 
          the kernel intentionally uses weak affinity.  Also, the very act of running top may break this weak affinity 
          and cause more processes to change CPUs more  often  (because  of  the  extra demand for cpu time).

       k: %CPU  --  CPU usage
          The  task’s  share  of  the  elapsed CPU time since the last screen update, expressed as a percentage 
          of total CPU time.  
          In a true SMP environment, if ’Irix mode’ is Off, top will operate in ’Solaris mode’ where a task’s 
          cpu usage will be 
          divided by the total number of CPUs.  You toggle ’Irix/Solaris’ modes with the ’I’ interactive command.

       l: TIME  --  CPU Time
          Total  CPU  time the task has used since it started.  When ’Cumulative mode’ is On, each process is listed with the 
          cpu time that it and its dead children has used.  You toggle ’Cumulative mode’ with ’S’, 
          which is a command-line option 
          and an interactive command.  See the ’S’ interactive command  for additional information regarding this mode.

       m: TIME+  --  CPU Time, hundredths
          The same as ’TIME’, but reflecting more granularity through hundredths of a second.

       n: %MEM  --  Memory usage (RES)
          A task’s currently used share of available physical memory.
          
       o: VIRT  --  Virtual Image (kb)
          The total amount of virtual memory used by the task.  It includes all code, data and shared libraries plus pages 
          that have been swapped out. (Note: you can define the STATSIZE=1 environment variable and the VIRT will be 
          calculated from the /proc/#/state VmSize field.)

       p: SWAP  --  Swapped size (kb)
          Per-process swap values are now taken from /proc/#/status VmSwap field.

       q: RES  --  Resident size (kb)
          The non-swapped physical memory a task has used.

       r: CODE  --  Code size (kb)
          The amount of physical memory devoted to executable code, also known as the ’text resident set’ size or TRS.

       s: DATA  --  Data+Stack size (kb)
          The amount of physical memory devoted to other than executable code, also known as the ’data resident set’
         size or DRS.

       t: SHR  --  Shared Mem size (kb)
          The amount of shared memory used by a task.  It simply reflects memory that could be potentially shared with 
          other processes.

       u: nFLT  --  Page Fault count
          The number of major page faults that have occurred for a task.  A page fault occurs when a process attempts to 
          read from or write  to  a  virtual  page that is not currently present in its address space.  
          A major page fault is when disk access is involved in making that page available.

       v: nDRT  --  Dirty Pages count
          The  number of pages that have been modified since they were last written to disk.  Dirty pages must be 
          written to disk 
          before the corresponding physical memory location can be used for some other virtual page.

       w: S  --  Process Status
          The status of the task which can be one of:
             ’D’ = uninterruptible sleep
             ’R’ = running
             ’S’ = sleeping
             ’T’ = traced or stopped
             ’Z’ = zombie

          Tasks shown as running should be more properly thought of as ’ready to run’  --  their task_struct is simply 
          represented on the Linux run-queue.   Even without a true SMP machine, you may see numerous tasks in this state 
          depending on top’s delay interval and nice value.

       x: Command  --  Command line or Program name
          Display  the command line used to start a task or the name of the associated program.  
          You toggle between command line and name with ’c’, which is both a command-line option and an interactive command.

          When you’ve chosen to display command lines, processes without a command line (like kernel threads) will be 
          shown with only the program name in  paren theses, as in this example:
                ( mdrecoveryd )

          Either  form of display is subject to potential truncation if it’s too long to fit in this field’s current width.  
         That width depends upon other fields selected, their order and the current screen width.

          Note: The ’Command’ field/column is unique, in that it is not fixed-width.  When displayed, this column will be 
          allocated all  remaining  screen  width (up to the maximum 512 characters) to provide for the potential growth 
          of program names into command lines.

       y: WCHAN  --  Sleeping in Function
          Depending  on  the availability of the kernel link map (’System.map’), this field will show the name or 
          the address of the kernel function in which the task is currently sleeping.  
          Running tasks will display a dash (’-’) in this column.

          Note: By displaying this field, top’s own working set will be increased by over 700Kb.  
          Your only means of reducing that overhead will be to  stop  and restart top.

       z: Flags  --  Task Flags
          This  column  represents  the  task’s  current scheduling flags which are expressed in hexadecimal notation 
          and with zeros suppressed.  These flags are officially documented in <linux/sched.h>.  
          Less formal documentation can also be found on the ’Fields select’ and ’Order fields’ screens.

   2b. SELECTING and ORDERING Columns
       After pressing the interactive commands ’f’ (Fields select) or ′o’ (Order fields) you will be shown a screen 
       containing the current fields string followed by names and descriptions for all fields.

       Here is a sample fields string from one of top’s four windows/field groups and an explanation of the conventions used:

       -  Sample fields string:
             ANOPQRSTUVXbcdefgjlmyzWHIK

       -  The order of displayed fields corresponds to the order of the letters in that string.

       -  If the letter is upper case the corresponding field itself will then be shown as part of the task 
          display (screen width permitting).  
          This will also be indicated by a leading asterisk (’*’), as in this excerpt:
              ...
              * K: %CPU       = CPU usage
                l: TIME       = CPU Time
                m: TIME+      = CPU Time, hundredths
              * N: %MEM       = Memory usage (RES)
              * O: VIRT       = Virtual Image (kb)
              ...

       Fields select screen  --  the ’f’ interactive command
          You toggle the display of a field by simply pressing the corresponding letter.

       Order fields screen  --  the ’o’ interactive command
          You move a field to the left by pressing the corresponding upper case letter and to the right with the 
          lower case letter.

   2c. SUMMARY Area Fields
       The summary area fields describing CPU statistics are abbreviated.  They provide information about times spent in:
           us = user mode
           sy = system mode
           ni = low priority user mode (nice)
           id = idle task
           wa = I/O waiting
           hi = servicing IRQs
           si = servicing soft IRQs
           st = steal (time given to other DomU instances)
           

来源自man手册:man top