(4)top详解 (每周一个linux命令系列)
linux命令 top详解
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).