Linux Top 命令解析 比较详细(6)

       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  parentheses, 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.

       默认情况下仅显示比较重要的  PID、USER、PR、NI、VIRT、RES、SHR、S、%CPU、%MEM、TIME+、COMMAND  列。

2.1 用快捷键更改显示内容。
（1）更改显示内容通过 f键可以选择显示的内容。

       按 f 键之后会显示列的列表，按 a-z  即可显示或隐藏对应的列，最后按回车键确定。

（2）按o键可以改变列的显示顺序。