(4)top详解 (每周一个linux命令系列)

(4)top详解 (每周一个linux命令系列)

linux命令 top详解

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引言：今天的命令是用来看cpu信息的top

top

我们先看man top

top - display Linux processes

翻译：显示linux进程信息

具体的描述如下：

The  top  program provides a dynamic real-time view of a running sys‐
       tem.  It can display system summary information as well as a list  of
       processes  or  threads  currently  being managed by the Linux kernel.
       The types of system summary information shown and  the  types,  order
       and  size of information displayed for processes are all user config‐
       urable and that configuration can be made persistent across restarts.

       The program provides a  limited  interactive  interface  for  process
       manipulation  as well as a much more extensive interface for personal
       configuration  --  encompassing every aspect of its  operation.   And
       while  top  is  referred to throughout this document, you are free to
       name the program anything you  wish.   That  new  name,  possibly  an
       alias,  will then be reflected on top's display and used when reading
       and writing a configuration file.

翻译如下：

top命令提供一个运行中系统的动态实时视图，它可以显示系统摘要信息以及由linux内核管理的的进程或线程的列表。系统概要信息的类型被显示出来，类型、顺序为进程显示的信息大小都是用户配置的。可以通过重新启动使配置持久化。

该程序为进程操作提供有限的交互式界面。并为个人配置提供了更广泛的接口 - 涵盖了其操作的各个方面。 虽然本文档中提到了top，但你可以随意命名该程序。 该新名称（可能是别名）将反映在top的显示界面上，并在读取和写入配置文件时使用。

我们再来看一下命令执行结果

top - 17:00:43 up 12 days,  1:13,  3 users,  load average: 6.27, 3.04, 2.31
Tasks: 444 total,   3 running, 441 sleeping,   0 stopped,   0 zombie
%Cpu(s): 19.0 us,  4.7 sy,  0.0 ni, 75.1 id,  1.1 wa,  0.0 hi,  0.2 si,  0.0
KiB Mem : 16131568 total,   926512 free,  8862288 used,  6342768 buff/cache
KiB Swap:  8191996 total,  8191900 free,       96 used.  5994096 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 5297 nobody    20   0  283588  20388   5372 R   9.3  0.1   9:25.75 php-fpm
23312 nobody    20   0  372584  21660   6272 S   9.3  0.1  14:31.92 php-fpm
23325 nobody    20   0  353288  13676   4916 R   9.3  0.1  14:55.50 php-fpm  

......

可以看到，top命令同时返回了一些uptime命令中返回的系统信息，这里不再赘述。

第二行是系统作业数量（Tasks）

 - total        进程总数
 - running      正在运行的进程数
 - sleeping     休眠的进程数
 - stopped      停止的进程数
 - zombie       僵尸进程数 （没有被子进程先于父进程结束却没有被回收，不占用内存等资源，但在进程表中有记录）

第三行是cpu使用情况（%Cpu(s)）

 - us, user：   运行未调整优先级的用户进程的CPU百分比
 - sy，system:  运行内核进程的CPU百分比
 - ni，niced：  运行已调整优先级的用户进程的CPU百分比
 - id           空闲cpu百分比
 - wa，IO wait: 用于等待IO完成的CPU时间
 - hi           硬件中断（Hardware IRQ）占用CPU的百分比
 - si           软件中断（Software Interrupts）占用CPU的百分比
 - st，Steal time 如果当前处于一个hypervisor下的vm，被vm偷走（Steal）的时间，虚拟 CPU 等待实际 CPU 的时间的百分比。

接下来的命令有点像是我们之前发的free

Mem: 

 - total        物理内存总量
 - used         使用中的物理内存总量
 - free         空闲内存总量
 - buffers      用作内核缓存的内存量 

Swap: 

 - total        交换区总量
 - used         使用中的交换区总量
 - free         空闲交换区总量
 - cached       缓冲的交换区总量。

在说交互和列含义之前，先大概说一下，top命令的交互并不是通过以前 ‘ 命令 <选项> ’的形式 而是在出现top视图后，按键盘上的键进行操作。

交互和选项

选项

top [-] [d] [p] [q] [c] [S] [s] [i] [n] [u]

使用说明

-d   delay 指定每两次屏幕信息刷新之间的时间间隔。交互命令s交互命令来改变之。
-p   通过指定监控进程ID来仅仅监控某个进程的状态。
-q   该选项将使top没有任何延迟的进行刷新。如果调用程序有超级用户权限，那么top将以尽可能高的优先级运行。
-c   显示整个命令行而不只是显示命令名
-S   指定累计模式 和交互命令中的S同
-s   使top命令在安全模式中运行。这将去除交互命令所带来的潜在危险。
-i   使top不显示任何闲置或者僵死进程。
-n   <次数>：循环显示的次数。
-u   <用户名>：指定用户名；

交互命令

h或？：显示帮助画面，给出一些简短的命令总结说明；
k：终止一个进程 按键后会提示:PID to signal/kill [default pid = xxx] 让你输入pid；
i：忽略闲置和僵死进程，这是一个开关式命令；
q：退出程序；
r：重新安排一个进程的优先级别 也会有提示：PID to renice [default pid = xxx] 输入pid后提示：Renice PID 28851 to value；输入正数降低优先级，负数增加优先级

S：切换到累计模式；
s：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3s；
f/F：从当前显示中添加或者删除列属性，进入后有操作说明；
o/O：改变显示项目的顺序；
l：切换显示平均负载和启动时间信息；
m：切换显示内存信息；
t：切换显示进程和CPU状态信息；
c：切换显示命令名称和完整命令；
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；
w：将当前设置写入~/.toprc文件中。

我们不可能尽善尽美的说明每一项，其他的用到的概率也不大。具体的意思也需要大家自己去尝试。我们下面说一下视图中每一列代表的含义（常用的带*）

列含义

* PID     = Process Id              进程唯一标识符
* USER    = Effective User Name     用户名
* PR      = Priority                优先级 越低越好 rt是运行状态
* NI      = Nice Value              调整的优先级
* VIRT    = Virtual Image (KiB)     进程使用的虚拟内存。VIRT=SWAP+RES
* RES     = Resident Size (KiB)     任务使用的非交换物理内存大小b。RES=CODE+DATA
* SHR     = Shared Memory (KiB)     SHR是进程使用的共享内存。共享内存大小，单位kb
* S       = Process Status          进程状态  取值如下：

                                D - 不可中断的睡眠态。
                                R – 运行态
                                S – 睡眠态
                                T – 被跟踪或已停止
                                Z – 僵尸态

* %CPU    = CPU Usage               任务所使用的CPU时间百分比。
* %MEM    = Memory Usage (RES)      任务所使用的CPU时间百分比
* TIME+   = CPU Time, hundredths    全部CPU时间精确到1/100秒
* COMMAND = Command Name/Line       进程名称（命令名/命令行）
  PPID    = Parent Process pid      PPID 父进程id
  UID     = Effective User Id       进程所有者的用户id
  RUID    = Real User Id            进程所有者的真实用户id
  RUSER   = Real User Name          进程所有者的真实用户
  SUID    = Saved User Id
  SUSER   = Saved User Name
  GID     = Group Id                用户组id
  GROUP   = Group Name              用户组
  PGRP    = Process Group Id        进程组id
  TTY     = Controlling Tty         控制台，有如下：

                                    ？          不是从终端启动的
                                    tty1-6      控制台1-6
                                    pty         虚拟终端
                                    pts/ptmx    pts(pseudo-terminal slave)是pty的实现方法，与ptmx(pseudo-terminal master)配合使用实现pty。pts/0 斜杠后的数字代表标号  一般pts都是网络连接进来的程序

  TPGID   = Tty Process Grp Id      tty的组
  SID     = Session Id              回话id
  nTH     = Number of Threads       线程数量
  P       = Last Used Cpu (SMP)     最后使用的cpu标号
  TIME    = CPU Time                使用cpu的时间
  SWAP    = Swapped Size (KiB)      进程使用的虚拟内存中，被换出的大小。
  CODE    = Code Size (KiB)         可执行代码占用的物理内存大小
  DATA    = Data+Stack (KiB)        可执行代码以外的部分(数据段+栈)占用的物理内存大小
  nMaj    = Major Page Faults
  nMin    = Minor Page Faults
  nDRT    = Dirty Pages Count       最后一次写入到现在，被修改过的页面数。
  WCHAN   = Sleeping in Function    若该进程在睡眠，则显示睡眠中的系统函数名
  Flags   = Task Flags <sched.h>    任务标志
  CGROUPS = Control Groups
  SUPGIDS = Supp Groups IDs
  SUPGRPS = Supp Groups Names
  TGID    = Thread Group Id         线程组id
  ENVIRON = Environment vars
  vMj     = Major Faults delta
  vMn     = Minor Faults delta
  USED    = Res+Swap Size (KiB)     物理内存和使用的交换区大小
  nsIPC   = IPC namespace Inode
  nsMNT   = MNT namespace Inode
  nsNET   = NET namespace Inode
  nsPID   = PID namespace Inode
  nsUSER  = USER namespace Inode
  nsUTS   = UTS namespace Inode 

附录：部分列名称的解释（来源于man top）

这里给出英文的原文档，方便大家参考。

   3a. DESCRIPTIONS of Fields
       Listed below are top's available process fields (columns).  They are shown in
       strict ascii alphabetical  order.   You  may  customize  their  position  and
       whether  or  not they are displayable with the `f' or `F' (Fields Management)
       interactive commands.

       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 4c. TASK AREA Commands, SORTING.

       The fields related to physical memory or  virtual  memory  reference  `(KiB)'
       which  is  the  unsuffixed display mode.  Such fields may, however, be scaled
       from KiB through PiB.  That scaling is influenced  via  the  `e'  interactive
       command or established for startup through a build option.

        1. %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 a process is multi-threaded and top is  not
           operating  in  Threads  mode,  amounts greater than 100% may be reported.
           You toggle Threads mode with the `H' interactive command.

           Also for multi-processor environments, 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'  inter‐
           active command.

        2. %MEM  --  Memory Usage (RES)
           A task's currently used share of available physical memory.

        3. CGROUPS  --  Control Groups
           The  names  of the control group(s) to which a process belongs, or `-' if
           not applicable for that process.

           Control Groups provide for allocating  resources  (cpu,  memory,  network
           bandwidth,  etc.)  among  installation-defined groups of processes.  They
           enable fine-grained control over allocating, denying, prioritizing,  man‐
           aging and monitoring those resources.

           Many  different hierarchies of cgroups can exist simultaneously on a sys‐
           tem and each hierarchy is attached to one or more subsystems.  A  subsys‐
           tem represents a single resource.

           Note:  The  CGROUPS field, unlike most columns, is not fixed-width.  When
           displayed, it plus any other variable width columns will be allocated all
           remaining screen width (up to the maximum 512 characters).  Even so, such
           variable width fields could  still  suffer  truncation.   See  topic  5c.
           SCROLLING  a Window for additional information on accessing any truncated
           data.

        4. CODE  --  Code Size (KiB)
           The amount of physical memory devoted to executable code, also  known  as
           the Text Resident Set size or TRS.

        5. COMMAND  --  Command Name or Command Line
           Display  the command line used to start a task or the name of the associ‐
           ated 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
           brackets, as in this example:
               [kthreadd]

           This field may also be impacted by the forest view display mode.  See the
           `V' interactive command for additional information regarding that mode.

           Note: The COMMAND field, unlike most columns, is not  fixed-width.   When
           displayed, it plus any other variable width columns will be allocated all
           remaining screen width (up to the maximum 512 characters).  Even so, such
           variable  width fields could still suffer truncation.  This is especially
           true for this field when command  lines  are  being  displayed  (the  `c'
           interactive  command.)   See  topic 5c. SCROLLING a Window for additional
           information on accessing any truncated data.

        6. DATA  --  Data + Stack Size (KiB)
           The amount of physical memory devoted to other than executable code, also
           known as the Data Resident Set size or DRS.

        7. ENVIRON  --  Environment variables
           Display  all of the environment variables, if any, as seen by the respec‐
           tive processes.  These variables will be displayed in  their  raw  native
           order, not the sorted order you are accustomed to seeing with an unquali‐
           fied `set'.

           Note: The ENVIRON field, unlike most columns, is not  fixed-width.   When
           displayed, it plus any other variable width columns will be allocated all
           remaining screen width (up to the maximum 512 characters).  Even so, such
           variable  width fields could still suffer truncation.  This is especially
           true for this field.  See topic 5c. SCROLLING  a  Window  for  additional
           information on accessing any truncated data.

        8. 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>.

        9. GID  --  Group Id
           The effective group ID.

       10. GROUP  --  Group Name
           The effective group name.

       11. 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 dis‐
           patch-ability.

       12. 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).

       13. PGRP  --  Process Group Id
           Every process is member of a unique process group which is used for  dis‐
           tribution  of  signals  and  by terminals to arbitrate requests for their
           input and output.  When a process is created (forked), it becomes a  mem‐
           ber of the process group of its parent.  By convention, this value equals
           the process ID (see PID) of the first member of a process  group,  called
           the process group leader.

       14. PID  --  Process Id
           The  task's  unique  process  ID,  which periodically wraps, though never
           restarting at zero.  In kernel terms, it is a dispatchable entity defined
           by a task_struct.

           This  value may also be used as: a process group ID (see PGRP); a session
           ID for the session leader (see SID); a thread group  ID  for  the  thread
           group leader (see TGID); and a TTY process group ID for the process group
           leader (see TPGID).

       15. PPID  --  Parent Process Id
           The process ID (pid) of a task's parent.

       16. PR  --  Priority
           The scheduling priority of the task.  If you see `rt' in this  field,  it
           means the task is running under real time scheduling priority.

           Under  linux,  real time priority is somewhat misleading since tradition‐
           ally the operating itself was not preemptible.  And while the 2.6  kernel
           can be made mostly preemptible, it is not always so.

       17. RES  --  Resident Memory Size (KiB)
           The non-swapped physical memory a task is using.

       18. RUID  --  Real User Id
           The real user ID.

       19. RUSER  --  Real User Name
           The real user name.

       20. S  --  Process Status
           The status of the task which can be one of:
               D = uninterruptible sleep
               R = running
               S = sleeping
               T = stopped by job control signal
               t = stopped by debugger during trace
               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.

       21. SHR  --  Shared Memory Size (KiB)
           The amount of shared memory available to a task, not all of which is typ‐
           ically  resident.   It  simply  reflects memory that could be potentially
           shared with other processes.

       22. SID  --  Session Id
           A session is a collection of process groups (see  PGRP),  usually  estab‐
           lished  by  the login shell.  A newly forked process joins the session of
           its creator.  By convention, this value equals the process ID  (see  PID)
           of  the  first member of the session, called the session leader, which is
           usually the login shell.

       23. SUID  --  Saved User Id
           The saved user ID.

       24. SUPGIDS  --  Supplementary Group IDs
           The IDs of any supplementary group(s) established at login  or  inherited
           from a task's parent.  They are displayed in a comma delimited list.

           Note:  The  SUPGIDS field, unlike most columns, is not fixed-width.  When
           displayed, it plus any other variable width columns will be allocated all
           remaining screen width (up to the maximum 512 characters).  Even so, such
           variable width fields could  still  suffer  truncation.   See  topic  5c.
           SCROLLING  a Window for additional information on accessing any truncated
           data.

       25. SUPGRPS  --  Supplementary Group Names
           The names of any supplementary group(s) established at login or inherited
           from a task's parent.  They are displayed in a comma delimited list.

           Note:  The  SUPGRPS field, unlike most columns, is not fixed-width.  When
           displayed, it plus any other variable width columns will be allocated all
           remaining screen width (up to the maximum 512 characters).  Even so, such
           variable width fields could  still  suffer  truncation.   See  topic  5c.
           SCROLLING  a Window for additional information on accessing any truncated
           data.

       26. SUSER  --  Saved User Name
           The saved user name.

       27. SWAP  --  Swapped Size (KiB)
           The non-resident portion of a task's address space.

       28. TGID  --  Thread Group Id
           The ID of the thread group to which a task belongs.  It is the PID of the
           thread  group  leader.   In  kernel terms, it represents those tasks that
           share an mm_struct.

       29. 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 have used.  You toggle Cumulative mode with `S', which is both a
           command-line  option and an interactive command.  See the `S' interactive
           command for additional information regarding this mode.

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

       31. TPGID  --  Tty Process Group Id
           The  process group ID of the foreground process for the connected tty, or
           -1 if a process is not connected to  a  terminal.   By  convention,  this
           value  equals  the  process ID (see PID) of the process group leader (see
           PGRP).

       32. 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  ter‐
           minal, in which case you'll see `?' displayed.

       33. UID  --  User Id
           The effective user ID of the task's owner.

       34. USED  --  Memory in Use (KiB)
           This  field  represents  the  non-swapped physical memory a task has used
           (RES) plus the non-resident portion of its address space (SWAP).

       35. USER  --  User Name
           The effective user name of the task's owner.

       36. VIRT  --  Virtual Memory Size (KiB)
           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 and
           pages that have been mapped but not used.

       37. 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.

           By  displaying  this  field,  top's own working set could be increased by
           over 700Kb, depending on the kernel version.   Should  that  occur,  your
           only means of reducing that overhead will be to stop and restart top.

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

       39. nMaj  --  Major 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  auxiliary storage access is involved in making that page
           available.

       40. nMin  --  Minor Page Fault count
           The number of minor 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  minor  page
           fault  does  not  involve  auxiliary  storage  access in making that page
           available.

       41. nTH  --  Number of Threads
           The number of threads associated with a process.

       42. nsIPC  --  IPC namespace
           The Inode of the namespace used  to  isolate  interprocess  communication
           (IPC) resources such as System V IPC objects and POSIX message queues.

       43. nsMNT  --  MNT namespace
           The  Inode  of the namespace used to isolate filesystem mount points thus
           offering different views of the filesystem hierarchy.

       44. nsNET  --  NET namespace
           The Inode of the namespace used to  isolate  resources  such  as  network
           devices, IP addresses, IP routing, port numbers, etc.

       45. nsPID  --  PID namespace
           The  Inode  of  the  namespace used to isolate process ID numbers meaning
           they need not remain unique.  Thus, each such namespace  could  have  its
           own  `init'  (PID  #1)  to  manage  various initialization tasks and reap
           orphaned child processes.

       46. nsUSER  --  USER namespace
           The Inode of the namespace used to isolate the user and group ID numbers.
           Thus,  a  process could have a normal unprivileged user ID outside a user
           namespace while having a user ID of 0, with full root privileges,  inside
           that namespace.

       47. nsUTS  --  UTS namespace
           The  Inode of the namespace used to isolate hostname and NIS domain name.
           UTS simply means "UNIX Time-sharing System".

       48. vMj  --  Major Page Fault Count Delta
           The number of major page faults that have occurred since the last  update
           (see nMaj).

       49. vMn  --  Minor Page Fault Count Delta
           The  number of minor page faults that have occurred since the last update
           (see nMin).