Linux云计算进阶-10条指令在1分钟内排查出服务器问题之top篇
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Linux云计算进阶-10条指令在1分钟内排查出服务器问题之top篇
TOP(1) User Commands TOP(1)
NAME
top - display Linux processes
SYNOPSIS
top -hv|-bcEeHiOSs1 -d secs -n max -u|U user -p pids -o field -w [cols]
The traditional switches `-' and whitespace are optional.
DESCRIPTION
The top program provides a dynamic real-time view of a running system. 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 configurable 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.
OVERVIEW
Documentation
The remaining Table of Contents
OVERVIEW
Operation
Linux Memory Types
1. COMMAND-LINE Options
2. SUMMARY Display
a. UPTIME and LOAD Averages
b. TASK and CPU States
c. MEMORY Usage
3. FIELDS / Columns Display
a. DESCRIPTIONS of Fields
b. MANAGING Fields
4. INTERACTIVE Commands
a. GLOBAL Commands
b. SUMMARY AREA Commands
c. TASK AREA Commands
1. Appearance
2. Content
3. Size
4. Sorting
d. COLOR Mapping
5. ALTERNATE-DISPLAY Provisions
a. WINDOWS Overview
b. COMMANDS for Windows
c. SCROLLING a Window
d. SEARCHING in a Window
e. FILTERING in a Window
6. FILES
a. PERSONAL Configuration File
b. ADDING INSPECT Entries
c. SYSTEM Configuration File
d. SYSTEM Restrictions File
7. STUPID TRICKS Sampler
a. Kernel Magic
b. Bouncing Windows
c. The Big Bird Window
d. The Ol' Switcheroo
8. BUGS, 9. SEE Also
Operation
When operating top, the two most important keys are the help (h or ?) key and quit (`q') key. Alternatively, you
could simply use the traditional interrupt key (^C) when you're done.
When started for the first time, you'll be presented with these traditional elements on the main top screen: 1)
Summary Area; 2) Fields/Columns Header; 3) Task Area. Each of these will be explored in the sections that follow.
There is also an Input/Message line between the Summary Area and Columns Header which needs no further explanation.
The main top screen is generally quite adaptive to changes in terminal dimensions under X-Windows. Other top screens
may be less so, especially those with static text. It ultimately depends, however, on your particular window manager
and terminal emulator. There may be occasions when their view of terminal size and current contents differs from
top's view, which is always based on operating system calls.
Following any re-size operation, if a top screen is corrupted, appears incomplete or disordered, simply typing
something innocuous like a punctuation character or cursor motion key will usually restore it. In extreme cases, the
following sequence almost certainly will:
key/cmd objective
^Z suspend top
fg resume top
<Left> force a screen redraw (if necessary)
But if the display is still corrupted, there is one more step you could try. Insert this command after top has been
suspended but before resuming it.
key/cmd objective
reset restore your terminal settings
Note: the width of top's display will be limited to 512 positions. Displaying all fields requires approximately 250
characters. Remaining screen width is usually allocated to any variable width columns currently visible. The
variable width columns, such as COMMAND, are noted in topic 3a. DESCRIPTIONS of Fields. Actual output width may also
be influenced by the -w switch, which is discussed in topic 1. COMMAND-LINE Options.
Lastly, some of top's screens or functions require the use of cursor motion keys like the standard arrow keys plus
the Home, End, PgUp and PgDn keys. If your terminal or emulator does not provide those keys, the following
combinations are accepted as alternatives:
key equivalent-keys
Left alt + h
Down alt + j
Up alt + k
Right alt + l
Home alt + ctrl + h
PgDn alt + ctrl + j
PgUp alt + ctrl + k
End alt + ctrl + l
The Up and Down arrow keys have special significance when prompted for line input terminated with the <Enter> key.
Those keys, or their aliases, can be used to retrieve previous input lines which can then be edited and re-input.
And there are four additional keys available with line oriented input.
key special-significance
Up recall older strings for re-editing
Down recall newer strings or erase entire line
Insert toggle between insert and overtype modes
Delete character removed at cursor, moving others left
Home jump to beginning of input line
End jump to end of input line
Linux Memory Types
For our purposes there are three types of memory, and one is optional. First is physical memory, a limited resource
where code and data must reside when executed or referenced. Next is the optional swap file, where modified (dirty)
memory can be saved and later retrieved if too many demands are made on physical memory. Lastly we have virtual
memory, a nearly unlimited resource serving the following goals:
1. abstraction, free from physical memory addresses/limits
2. isolation, every process in a separate address space
3. sharing, a single mapping can serve multiple needs
4. flexibility, assign a virtual address to a file
Regardless of which of these forms memory may take, all are managed as pages (typically 4096 bytes) but expressed by
default in top as KiB (kibibyte). The memory discussed under topic `2c. MEMORY Usage' deals with physical memory and
the swap file for the system as a whole. The memory reviewed in topic `3. FIELDS / Columns Display' embraces all
three memory types, but for individual processes.
For each such process, every memory page is restricted to a single quadrant from the table below. Both physical
memory and virtual memory can include any of the four, while the swap file only includes #1 through #3. The memory
in quadrant #4, when modified, acts as its own dedicated swap file.
Private | Shared
1 | 2
Anonymous . stack |
. malloc() |
. brk()/sbrk() | . POSIX shm*
. mmap(PRIVATE, ANON) | . mmap(SHARED, ANON)
-----------------------+----------------------
. mmap(PRIVATE, fd) | . mmap(SHARED, fd)
File-backed . pgms/shared libs |
3 | 4
The following may help in interpreting process level memory values displayed as scalable columns and discussed under
topic `3a. DESCRIPTIONS of Fields'.
%MEM - simply RES divided by total physical memory
CODE - the `pgms' portion of quadrant 3
DATA - the entire quadrant 1 portion of VIRT plus all
explicit mmap file-backed pages of quadrant 3
RES - anything occupying physical memory which, beginning with
Linux-4.5, is the sum of the following three fields:
RSan - quadrant 1 pages, which include any
former quadrant 3 pages if modified
RSfd - quadrant 3 and quadrant 4 pages
RSsh - quadrant 2 pages
RSlk - subset of RES which cannot be swapped out (any quadrant)
SHR - subset of RES (excludes 1, includes all 2 & 4, some 3)
SWAP - potentially any quadrant except 4
USED - simply the sum of RES and SWAP
VIRT - everything in-use and/or reserved (all quadrants)
Note: Even though program images and shared libraries are considered private to a process, they will be accounted for
as shared (SHR) by the kernel.
1. COMMAND-LINE Options
The command-line syntax for top consists of:
-hv|-bcEeHiOSs1 -d secs -n max -u|U user -p pids -o field -w [cols]
The typically mandatory switch (`-') and even whitespace are completely optional.
-h | -v :Help/Version
Show library version and the usage prompt, then quit.
-b :Batch-mode operation
Starts top in Batch mode, which could be useful for sending output from top to other programs or to a file. In
this mode, top will not accept input and runs until the iterations limit you've set with the `-n' command-line
option or until killed.
-c :Command-line/Program-name toggle
Starts top with the last remembered `c' state reversed. Thus, if top was displaying command lines, now that
field will show program names, and vice versa. See the `c' interactive command for additional information.
-d :Delay-time interval as: -d ss.t (secs.tenths)
Specifies the delay between screen updates, and overrides the corresponding value in one's personal
configuration file or the startup default. Later this can be changed with the `d' or `s' interactive commands.
Fractional seconds are honored, but a negative number is not allowed. In all cases, however, such changes are
prohibited if top is running in Secure mode, except for root (unless the `s' command-line option was used). For
additional information on Secure mode see topic 6d. SYSTEM Restrictions File.
-e :Enforce-Task-Memory-Scaling as: -e k | m | g | t | p
Instructs top to force task area memory to be scaled as:
k - kibibytes
m - mebibytes
g - gibibytes
t - tebibytes
p - pebibytes
Later this can be changed with the `e' command toggle.
-E :Enforce-Summary-Memory-Scaling as: -E k | m | g | t | p | e
Instructs top to force summary area memory to be scaled as:
k - kibibytes
m - mebibytes
g - gibibytes
t - tebibytes
p - pebibytes
e - exbibytes
Later this can be changed with the `E' command toggle.
-H :Threads-mode operation
Instructs top to display individual threads. Without this command-line option a summation of all threads in
each process is shown. Later this can be changed with the `H' interactive command.
-i :Idle-process toggle
Starts top with the last remembered `i' state reversed. When this toggle is Off, tasks that have not used any
CPU since the last update will not be displayed. For additional information regarding this toggle see topic 4c.
TASK AREA Commands, SIZE.
-n :Number-of-iterations limit as: -n number
Specifies the maximum number of iterations, or frames, top should produce before ending.
-o :Override-sort-field as: -o fieldname
Specifies the name of the field on which tasks will be sorted, independent of what is reflected in the
configuration file. You can prepend a `+' or `-' to the field name to also override the sort direction. A
leading `+' will force sorting high to low, whereas a `-' will ensure a low to high ordering.
This option exists primarily to support automated/scripted batch mode operation.
-O :Output-field-names
This option acts as a form of help for the above -o option. It will cause top to print each of the available
field names on a separate line, then quit. Such names are subject to NLS (National Language Support)
translation.
-p :Monitor-PIDs mode as: -pN1 -pN2 ... or -pN1,N2,N3 ...
Monitor only processes with specified process IDs. This option can be given up to 20 times, or you can provide
a comma delimited list with up to 20 pids. Co-mingling both approaches is permitted.
A pid value of zero will be treated as the process id of the top program itself once it is running.
This is a command-line option only and should you wish to return to normal operation, it is not necessary to
quit and restart top -- just issue any of these interactive commands: `=', `u' or `U'.
The `p', `u' and `U' command-line options are mutually exclusive.
-s :Secure-mode operation
Starts top with secure mode forced, even for root. This mode is far better controlled through a system
configuration file (see topic 6. FILES).
-S :Cumulative-time toggle
Starts top with the last remembered `S' state reversed. When Cumulative time 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.
-u | -U :User-filter-mode as: -u | -U number or name
Display only processes with a user id or user name matching that given. The `-u' option matches on effective
user whereas the `-U' option matches on any user (real, effective, saved, or filesystem).
Prepending an exclamation point (`!') to the user id or name instructs top to display only processes with users
not matching the one provided.
The `p', `u' and `U' command-line options are mutually exclusive.
-w :Output-width-override as: -w [ number ]
In Batch mode, when used without an argument top will format output using the COLUMNS= and LINES= environment
variables, if set. Otherwise, width will be fixed at the maximum 512 columns. With an argument, output width
can be decreased or increased (up to 512) but the number of rows is considered unlimited.
In normal display mode, when used without an argument top will attempt to format output using the COLUMNS= and
LINES= environment variables, if set. With an argument, output width can only be decreased, not increased.
Whether using environment variables or an argument with -w, when not in Batch mode actual terminal dimensions
can never be exceeded.
Note: Without the use of this command-line option, output width is always based on the terminal at which top was
invoked whether or not in Batch mode.
-1 :Single/Separate-Cpu-States toggle
Starts top with the last remembered Cpu States portion of the summary area reversed. Either all cpu information
will be displayed in a single line or each cpu will be displayed separately, depending on the state of the NUMA
Node command toggle ('2').
See the `1' and '2' interactive commands for additional information.
2. SUMMARY Display
Each of the following three areas are individually controlled through one or more interactive commands. See topic
4b. SUMMARY AREA Commands for additional information regarding these provisions.
2a. UPTIME and LOAD Averages
This portion consists of a single line containing:
program or window name, depending on display mode
current time and length of time since last boot
total number of users
system load avg over the last 1, 5 and 15 minutes
2b. TASK and CPU States
This portion consists of a minimum of two lines. In an SMP environment, additional lines can reflect individual CPU
state percentages.
Line 1 shows total tasks or threads, depending on the state of the Threads-mode toggle. That total is further
classified as:
running; sleeping; stopped; zombie
Line 2 shows CPU state percentages based on the interval since the last refresh.
As a default, percentages for these individual categories are displayed. Where two labels are shown below, those for
more recent kernel versions are shown first.
us, user : time running un-niced user processes
sy, system : time running kernel processes
ni, nice : time running niced user processes
id, idle : time spent in the kernel idle handler
wa, IO-wait : time waiting for I/O completion
hi : time spent servicing hardware interrupts
si : time spent servicing software interrupts
st : time stolen from this vm by the hypervisor
In the alternate cpu states display modes, beyond the first tasks/threads line, an abbreviated summary is shown
consisting of these elements:
a b c d
%Cpu(s): 75.0/25.0 100[ ...
Where: a) is the `user' (us + ni) percentage; b) is the `system' (sy + hi + si) percentage; c) is the total; and d)
is one of two visual graphs of those representations. See topic 4b. SUMMARY AREA Commands and the `t' command for
additional information on that special 4-way toggle.
2c. MEMORY Usage
This portion consists of two lines which may express values in kibibytes (KiB) through exbibytes (EiB) depending on
the scaling factor enforced with the `E' interactive command.
As a default, Line 1 reflects physical memory, classified as:
total, free, used and buff/cache
Line 2 reflects mostly virtual memory, classified as:
total, free, used and avail (which is physical memory)
The avail number on line 2 is an estimation of physical memory available for starting new applications, without
swapping. Unlike the free field, it attempts to account for readily reclaimable page cache and memory slabs. It is
available on kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as free.
In the alternate memory display modes, two abbreviated summary lines are shown consisting of these elements:
a b c
GiB Mem : 18.7/15.738 [ ...
GiB Swap: 0.0/7.999 [ ...
Where: a) is the percentage used; b) is the total available; and c) is one of two visual graphs of those
representations.
In the case of physical memory, the percentage represents the total minus the estimated avail noted above. The `Mem'
graph itself is divided between used and any remaining memory not otherwise accounted for by avail. See topic 4b.
SUMMARY AREA Commands and the `m' command for additional information on that special 4-way toggle.
This table may help in interpreting the scaled values displayed:
KiB = kibibyte = 1024 bytes
MiB = mebibyte = 1024 KiB = 1,048,576 bytes
GiB = gibibyte = 1024 MiB = 1,073,741,824 bytes
TiB = tebibyte = 1024 GiB = 1,099,511,627,776 bytes
PiB = pebibyte = 1024 TiB = 1,125,899,906,842,624 bytes
EiB = exbibyte = 1024 PiB = 1,152,921,504,606,846,976 bytes
3. FIELDS / Columns
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 provisions 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' interactive
command.
Note: When running in forest view mode (`V') with children collapsed (`v'), this field will also include the CPU
time of those unseen children. See topic 4c. TASK AREA Commands, CONTENT for more information regarding the `V'
and `v' toggles.
2. %MEM -- Memory Usage (RES)
A task's currently resident share of available physical memory.
See `OVERVIEW, Linux Memory Types' for additional details.
3. CGNAME -- Control Group Name
The name of the control group to which a process belongs, or `-' if not applicable for that process.
This will typically be the last entry in the full list of control groups as shown under the next heading
(CGROUPS). And as is true there, this field is also variable width.
4. 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, managing and
monitoring those resources.
Many different hierarchies of cgroups can exist simultaneously on a system and each hierarchy is attached to one
or more subsystems. A subsystem 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.
5. CODE -- Code Size (KiB)
The amount of physical memory currently devoted to executable code, also known as the Text Resident Set size or
TRS.
See `OVERVIEW, Linux Memory Types' for additional details.
6. COMMAND -- Command Name or Command Line
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 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.
7. DATA -- Data + Stack Size (KiB)
The amount of private memory reserved by a process. It is also known as the Data Resident Set or DRS. Such
memory may not yet be mapped to physical memory (RES) but will always be included in the virtual memory (VIRT)
amount.
See `OVERVIEW, Linux Memory Types' for additional details.
8. ENVIRON -- Environment variables
Display all of the environment variables, if any, as seen by the respective processes. These variables will be
displayed in their raw native order, not the sorted order you are accustomed to seeing with an unqualified `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.
9. 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>.
10. GID -- Group Id
The effective group ID.
11. GROUP -- Group Name
The effective group name.
12. LXC -- Lxc Container Name
The name of the lxc container within which a task is running. If a process is not running inside a container, a
dash (`-') will be shown.
13. 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 dispatch-
ability.
14. NU -- Last known NUMA node
A number representing the NUMA node associated with the last used processor (`P'). When -1 is displayed it means
that NUMA information is not available.
See the `'2' and `3' interactive commands for additional NUMA provisions affecting the summary area.
15. OOMa -- Out of Memory Adjustment Factor
The value, ranging from -1000 to +1000, added to the current out of memory score (OOMs) which is then used to
determine which task to kill when memory is exhausted.
16. OOMs -- Out of Memory Score
The value, ranging from 0 to +1000, used to select task(s) to kill when memory is exhausted. Zero translates to
`never kill' whereas 1000 means `always kill'.
17. 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).
18. PGRP -- Process Group Id
Every process is member of a unique process group which is used for distribution of signals and by terminals to
arbitrate requests for their input and output. When a process is created (forked), it becomes a member 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.
19. 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).
20. PPID -- Parent Process Id
The process ID (pid) of a task's parent.
21. 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 traditionally the operating itself was not
preemptible. And while the 2.6 kernel can be made mostly preemptible, it is not always so.
22. RES -- Resident Memory Size (KiB)
A subset of the virtual address space (VIRT) representing the non-swapped physical memory a task is currently
using. It is also the sum of the RSan, RSfd and RSsh fields.
It can include private anonymous pages, private pages mapped to files (including program images and shared
libraries) plus shared anonymous pages. All such memory is backed by the swap file represented separately under
SWAP.
Lastly, this field may also include shared file-backed pages which, when modified, act as a dedicated swap file
and thus will never impact SWAP.
See `OVERVIEW, Linux Memory Types' for additional details.
23. RSan -- Resident Anonymous Memory Size (KiB)
A subset of resident memory (RES) representing private pages not mapped to a file.
24. RSfd -- Resident File-Backed Memory Size (KiB)
A subset of resident memory (RES) representing the implicitly shared pages supporting program images and shared
libraries. It also includes explicit file mappings, both private and shared.
25. RSlk -- Resident Locked Memory Size (KiB)
A subset of resident memory (RES) which cannot be swapped out.
26. RSsh -- Resident Shared Memory Size (KiB)
A subset of resident memory (RES) representing the explicitly shared anonymous shm*/mmap pages.
27. RUID -- Real User Id
The real user ID.
28. RUSER -- Real User Name
The real user name.
29. S -- Process Status
The status of the task which can be one of:
D = uninterruptible sleep
I = idle
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.
30. SHR -- Shared Memory Size (KiB)
A subset of resident memory (RES) that may be used by other processes. It will include shared anonymous pages
and shared file-backed pages. It also includes private pages mapped to files representing program images and
shared libraries.
See `OVERVIEW, Linux Memory Types' for additional details.
31. SID -- Session Id
A session is a collection of process groups (see PGRP), usually established 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.
32. SUID -- Saved User Id
The saved user ID.
33. 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.
34. 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.
35. SUSER -- Saved User Name
The saved user name.
36. SWAP -- Swapped Size (KiB)
The formerly resident portion of a task's address space written to the swap file when physical memory becomes
over committed.
See `OVERVIEW, Linux Memory Types' for additional details.
37. 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.
38. 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.
39. TIME+ -- CPU Time, hundredths
The same as TIME, but reflecting more granularity through hundredths of a second.
40. 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).
41. 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.
42. UID -- User Id
The effective user ID of the task's owner.
43. USED -- Memory in Use (KiB)
This field represents the non-swapped physical memory a task is using (RES) plus the swapped out portion of its
address space (SWAP).
See `OVERVIEW, Linux Memory Types' for additional details.
44. USER -- User Name
The effective user name of the task's owner.
45. 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.
See `OVERVIEW, Linux Memory Types' for additional details.
46. WCHAN -- Sleeping in Function
This field will show the name of the kernel function in which the task is currently sleeping. Running tasks will
display a dash (`-') in this column.
47. 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.
This field was deprecated with linux 2.6 and is always zero.
48. 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.
49. 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.
50. nTH -- Number of Threads
The number of threads associated with a process.
51. 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.
52. nsMNT -- MNT namespace
The Inode of the namespace used to isolate filesystem mount points thus offering different views of the
filesystem hierarchy.
53. nsNET -- NET namespace
The Inode of the namespace used to isolate resources such as network devices, IP addresses, IP routing, port
numbers, etc.
54. 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/systemd' (PID #1) to manage various initialization tasks and reap
orphaned child processes.
55. 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.
56. nsUTS -- UTS namespace
The Inode of the namespace used to isolate hostname and NIS domain name. UTS simply means "UNIX Time-sharing
System".
57. vMj -- Major Page Fault Count Delta
The number of major page faults that have occurred since the last update (see nMaj).
58. vMn -- Minor Page Fault Count Delta
The number of minor page faults that have occurred since the last update (see nMin).
3b. MANAGING Fields
After pressing the interactive command `f' or `F' (Fields Management) you will be presented with a screen showing: 1)
the `current' window name; 2) the designated sort field; 3) all fields in their current order along with
descriptions. Entries marked with an asterisk are the currently displayed fields, screen width permitting.
• As the on screen instructions indicate, you navigate among the fields with the Up and Down arrow keys. The
PgUp, PgDn, Home and End keys can also be used to quickly reach the first or last available field.
• The Right arrow key selects a field for repositioning and the Left arrow key or the <Enter> key commits that
field's placement.
• The `d' key or the <Space> bar toggles a field's display status, and thus the presence or absence of the
asterisk.
• The `s' key designates a field as the sort field. See topic 4c. TASK AREA Commands, SORTING for additional
information regarding your selection of a sort field.
• The `a' and `w' keys can be used to cycle through all available windows and the `q' or <Esc> keys exit Fields
Management.
The Fields Management screen can also be used to change the `current' window/field group in either full-screen mode
or alternate-display mode. Whatever was targeted when `q' or <Esc> was pressed will be made current as you return to
the top display. See topic 5. ALTERNATE-DISPLAY Provisions and the `g' interactive command for insight into
`current' windows and field groups.
Note: Any window that has been scrolled horizontally will be reset if any field changes are made via the Fields
Management screen. Any vertical scrolled position, however, will not be affected. See topic 5c. SCROLLING a Window
for additional information regarding vertical and horizontal scrolling.
4. INTERACTIVE Commands
Listed below is a brief index of commands within categories. Some commands appear more than once -- their meaning
or scope may vary depending on the context in which they are issued.
4a. Global-Commands
<Ent/Sp> ?, =, 0,
A, B, d, E, e, g, h, H, I, k, q, r, s, W, X, Y, Z
4b. Summary-Area-Commands
C, l, t, m, 1, 2, 3, 4, !
4c. Task-Area-Commands
Appearance: b, J, j, x, y, z
Content: c, f, F, o, O, S, u, U, V, v
Size: #, i, n
Sorting: <, >, f, F, R
4d. Color-Mapping
<Ret>, a, B, b, H, M, q, S, T, w, z, 0 - 7
5b. Commands-for-Windows
-, _, =, +, A, a, g, G, w
5c. Scrolling-a-Window
C, Up, Dn, Left, Right, PgUp, PgDn, Home, End
5d. Searching-in-a-Window
L, &
4a. GLOBAL Commands
The global interactive commands are always available in both full-screen mode and alternate-display mode. However,
some of these interactive commands are not available when running in Secure mode.
If you wish to know in advance whether or not your top has been secured, simply ask for help and view the system
summary on the second line.
<Enter> or <Space> :Refresh-Display
These commands awaken top and following receipt of any input the entire display will be repainted. They also
force an update of any hotplugged cpu or physical memory changes.
Use either of these keys if you have a large delay interval and wish to see current status,
? | h :Help
There are two help levels available. The first will provide a reminder of all the basic interactive commands.
If top is secured, that screen will be abbreviated.
Typing `h' or `?' on that help screen will take you to help for those interactive commands applicable to
alternate-display mode.
= :Exit-Display-Limits
Removes restrictions on what is shown. This command will reverse any `i' (idle tasks), `n' (max tasks) and
`v' (hide children) commands that might be active. It also provides for an exit from PID monitoring, User
filtering, Other filtering, Locate processing and Combine Cpus mode.
Additionally, if the window has been scrolled it will be reset with this command.
0 :Zero-Suppress toggle
This command determines whether zeros are shown or suppressed for many of the fields in a task window. Fields
like UID, GID, NI, PR or P are not affected by this toggle.
A :Alternate-Display-Mode toggle
This command will switch between full-screen mode and alternate-display mode. See topic 5. ALTERNATE-DISPLAY
Provisions and the `g' interactive command for insight into `current' windows and field groups.
B :Bold-Disable/Enable toggle
This command will influence use of the bold terminfo capability and alters both the summary area and task area
for the `current' window. While it is intended primarily for use with dumb terminals, it can be applied
anytime.
Note: When this toggle is On and top is operating in monochrome mode, the entire display will appear as normal
text. Thus, unless the `x' and/or `y' toggles are using reverse for emphasis, there will be no visual
confirmation that they are even on.
* d | s :Change-Delay-Time-interval
You will be prompted to enter the delay time, in seconds, between display updates.
Fractional seconds are honored, but a negative number is not allowed. Entering 0 causes (nearly) continuous
updates, with an unsatisfactory display as the system and tty driver try to keep up with top's demands. The
delay value is inversely proportional to system loading, so set it with care.
If at any time you wish to know the current delay time, simply ask for help and view the system summary on the
second line.
E :Enforce-Summary-Memory-Scale in Summary Area
With this command you can cycle through the available summary area memory scaling which ranges from KiB
(kibibytes or 1,024 bytes) through EiB (exbibytes or 1,152,921,504,606,846,976 bytes).
If you see a `+' between a displayed number and the following label, it means that top was forced to truncate
some portion of that number. By raising the scaling factor, such truncation can be avoided.
e :Enforce-Task-Memory-Scale in Task Area
With this command you can cycle through the available task area memory scaling which ranges from KiB
(kibibytes or 1,024 bytes) through PiB (pebibytes or 1,125,899,906,842,624 bytes).
While top will try to honor the selected target range, additional scaling might still be necessary in order to
accommodate current values. If you wish to see a more homogeneous result in the memory columns, raising the
scaling range will usually accomplish that goal. Raising it too high, however, is likely to produce an all
zero result which cannot be suppressed with the `0' interactive command.
g :Choose-Another-Window/Field-Group
You will be prompted to enter a number between 1 and 4 designating the field group which should be made the
`current' window. You will soon grow comfortable with these 4 windows, especially after experimenting with
alternate-display mode.
H :Threads-mode toggle
When this toggle is On, individual threads will be displayed for all processes in all visible task windows.
Otherwise, top displays a summation of all threads in each process.
I :Irix/Solaris-Mode toggle
When operating in Solaris mode (`I' toggled Off), a task's cpu usage will be divided by the total number of
CPUs. After issuing this command, you'll be told the new state of this toggle.
* k :Kill-a-task
You will be prompted for a PID and then the signal to send.
Entering no PID or a negative number will be interpreted as the default shown in the prompt (the first task
displayed). A PID value of zero means the top program itself.
The default signal, as reflected in the prompt, is SIGTERM. However, you can send any signal, via number or
name.
If you wish to abort the kill process, do one of the following depending on your progress:
1) at the pid prompt, type an invalid number
2) at the signal prompt, type 0 (or any invalid signal)
3) at any prompt, type <Esc>
q :Quit
* r :Renice-a-Task
You will be prompted for a PID and then the value to nice it to.
Entering no PID or a negative number will be interpreted as the default shown in the prompt (the first task
displayed). A PID value of zero means the top program itself.
A positive nice value will cause a process to lose priority. Conversely, a negative nice value will cause a
process to be viewed more favorably by the kernel. As a general rule, ordinary users can only increase the
nice value and are prevented from lowering it.
If you wish to abort the renice process, do one of the following depending on your progress:
1) at the pid prompt, type an invalid number
2) at the nice prompt, type <Enter> with no input
3) at any prompt, type <Esc>
W :Write-the-Configuration-File
This will save all of your options and toggles plus the current display mode and delay time. By issuing this
command just before quitting top, you will be able restart later in exactly that same state.
X :Extra-Fixed-Width
Some fields are fixed width and not scalable. As such, they are subject to truncation which would be
indicated by a `+' in the last position.
This interactive command can be used to alter the widths of the following fields:
field default field default field default
GID 5 GROUP 8 WCHAN 10
RUID 5 LXC 8 nsIPC 10
SUID 5 RUSER 8 nsMNT 10
UID 5 SUSER 8 nsNET 10
TTY 8 nsPID 10
USER 8 nsUSER 10
nsUTS 10
You will be prompted for the amount to be added to the default widths shown above. Entering zero forces a
return to those defaults.
If you enter a negative number, top will automatically increase the column size as needed until there is no
more truncated data. You can accelerate this process by reducing the delay interval or holding down the
<Space> bar.
Note: Whether explicitly or automatically increased, the widths for these fields are never decreased by top.
To narrow them you must specify a smaller number or restore the defaults.
Y :Inspect-Other-Output
After issuing the `Y' interactive command, you will be prompted for a target PID. Typing a value or accepting
the default results in a separate screen. That screen can be used to view a variety of files or piped command
output while the normal top iterative display is paused.
Note: This interactive command is only fully realized when supporting entries have been manually added to the
end of the top configuration file. For details on creating those entries, see topic 6b. ADDING INSPECT
Entries.
Most of the keys used to navigate the Inspect feature are reflected in its header prologue. There are,
however, additional keys available once you have selected a particular file or command. They are familiar to
anyone who has used the pager `less' and are summarized here for future reference.
key function
= alternate status-line, file or pipeline
/ find, equivalent to `L' locate
n find next, equivalent to `&' locate next
<Space> scroll down, equivalent to <PgDn>
b scroll up, equivalent to <PgUp>
g first line, equivalent to <Home>
G last line, equivalent to <End>
Z :Change-Color-Mapping
This key will take you to a separate screen where you can change the colors for the `current' window, or for
all windows. For details regarding this interactive command see topic 4d. COLOR Mapping.
* The commands shown with an asterisk (`*') are not available in Secure mode, nor will they be shown on the level-1
help screen.
4b. SUMMARY AREA Commands
The summary area interactive commands are always available in both full-screen mode and alternate-display mode. They
affect the beginning lines of your display and will determine the position of messages and prompts.
These commands always impact just the `current' window/field group. See topic 5. ALTERNATE-DISPLAY Provisions and
the `g' interactive command for insight into `current' windows and field groups.
C :Show-scroll-coordinates toggle
Toggle an informational message which is displayed whenever the message line is not otherwise being used. For
additional information see topic 5c. SCROLLING a Window.
l :Load-Average/Uptime toggle
This is also the line containing the program name (possibly an alias) when operating in full-screen mode or
the `current' window name when operating in alternate-display mode.
t :Task/Cpu-States toggle
This command affects from 2 to many summary area lines, depending on the state of the `1', `2' or `3' command
toggles and whether or not top is running under true SMP.
This portion of the summary area is also influenced by the `H' interactive command toggle, as reflected in the
total label which shows either Tasks or Threads.
This command serves as a 4-way toggle, cycling through these modes:
1. detailed percentages by category
2. abbreviated user/system and total % + bar graph
3. abbreviated user/system and total % + block graph
4. turn off task and cpu states display
When operating in either of the graphic modes, the display becomes much more meaningful when individual CPUs
or NUMA nodes are also displayed. See the the `1', `2' and `3' commands below for additional information.
m :Memory/Swap-Usage toggle
This command affects the two summary area lines dealing with physical and virtual memory.
This command serves as a 4-way toggle, cycling through these modes:
1. detailed percentages by memory type
2. abbreviated % used/total available + bar graph
3. abbreviated % used/total available + block graph
4. turn off memory display
1 :Single/Separate-Cpu-States toggle
This command affects how the `t' command's Cpu States portion is shown. Although this toggle exists primarily
to serve massively-parallel SMP machines, it is not restricted to solely SMP environments.
When you see `%Cpu(s):' in the summary area, the `1' toggle is On and all cpu information is gathered in a
single line. Otherwise, each cpu is displayed separately as: `%Cpu0, %Cpu1, ...' up to available screen
height.
2 :NUMA-Nodes/Cpu-Summary toggle
This command toggles between the `1' command cpu summary display (only) or a summary display plus the cpu
usage statistics for each NUMA Node. It is only available if a system has the requisite NUMA support.
3 :Expand-NUMA-Node
You will be invited to enter a number representing a NUMA Node. Thereafter, a node summary plus the
statistics for each cpu in that node will be shown until the `1', `2' or `4' command toggle is pressed. This
interactive command is only available if a system has the requisite NUMA support.
4 :Display-Cpus-Two-Abreast
This command turns the `1' toggle Off for individual cpu display but prints the results two abreast. It
requires a terminal with a minimum width of 80 columns. If a terminal's width is decreased below the minimum
while top is running, top reverts to the normal `1' toggle Off state.
To avoid truncation when displaying detailed cpu statistcs, as opposed to the graphic representations, a
minimum width of 165 columns would be required.
! :Combine-Cpus-Mode
This command toggle is intended for massively parallel SMP environments where, even with the `4' command
toggle, not all processors can be displayed. With each press of `!' the number of additional cpu's combined
is doubled thus reducing the total number of cpu lines displayed.
For example, with the first press of `!' one additional cpu will be combined and displayed as `0-1, 2-3, ...'
instead of the normal `%Cpu0, %Cpu1, %Cpu2, %Cpu3, ...'. With a second `!' command toggle two additional cpus
are combined and shown as `0-2, 3-5, ...'. Then the third '!' press, combining four additional cpus, shows as
`0-4, 5-9, ...', etc.
Such progression continues until individual cpus are again displayed and impacts both the `1' and `4' toggles
(one or two columns). Use the `=' command to exit Combine Cpus mode.
Note: If the entire summary area has been toggled Off for any window, you would be left with just the message line.
In that way, you will have maximized available task rows but (temporarily) sacrificed the program name in full-screen
mode or the `current' window name when in alternate-display mode.
4c. TASK AREA Commands
The task area interactive commands are always available in full-screen mode.
The task area interactive commands are never available in alternate-display mode if the `current' window's task
display has been toggled Off (see topic 5. ALTERNATE-DISPLAY Provisions).
APPEARANCE of task window
J :Justify-Numeric-Columns toggle
Alternates between right-justified (the default) and left-justified numeric data. If the numeric data
completely fills the available column, this command toggle may impact the column header only.
j :Justify-Character-Columns toggle
Alternates between left-justified (the default) and right-justified character data. If the character data
completely fills the available column, this command toggle may impact the column header only.
The following commands will also be influenced by the state of the global `B' (bold enable) toggle.
b :Bold/Reverse toggle
This command will impact how the `x' and `y' toggles are displayed. It may also impact the summary area when
a bar graph has been selected for cpu states or memory usage via the `t' or `m' toggles.
x :Column-Highlight toggle
Changes highlighting for the current sort field. If you forget which field is being sorted this command can
serve as a quick visual reminder, providing the sort field is being displayed. The sort field might not be
visible because:
1) there is insufficient Screen Width
2) the `f' interactive command turned it Off
Note: Whenever Searching and/or Other Filtering is active in a window, column highlighting is temporarily
disabled. See the notes at the end of topics 5d. SEARCHING and 5e. FILTERING for an explanation why.
y :Row-Highlight toggle
Changes highlighting for "running" tasks. For additional insight into this task state, see topic 3a.
DESCRIPTIONS of Fields, the `S' field (Process Status).
Use of this provision provides important insight into your system's health. The only costs will be a few
additional tty escape sequences.
z :Color/Monochrome toggle
Switches the `current' window between your last used color scheme and the older form of black-on-white or
white-on-black. This command will alter both the summary area and task area but does not affect the state of
the `x', `y' or `b' toggles.
CONTENT of task window
c :Command-Line/Program-Name toggle
This command will be honored whether or not the COMMAND column is currently visible. Later, should that field
come into view, the change you applied will be seen.
f | F :Fields-Management
These keys display a separate screen where you can change which fields are displayed, their order and also
designate the sort field. For additional information on these interactive commands see topic 3b. MANAGING
Fields.
o | O :Other-Filtering
You will be prompted for the selection criteria which then determines which tasks will be shown in the
`current' window. Your criteria can be made case sensitive or case can be ignored. And you determine if top
should include or exclude matching tasks.
See topic 5e. FILTERING in a window for details on these and additional related interactive commands.
S :Cumulative-Time-Mode toggle
When Cumulative mode is On, each process is listed with the cpu time that it and its dead children have used.
When Off, programs that fork into many separate tasks will appear less demanding. For programs like `init' or
a shell this is appropriate but for others, like compilers, perhaps not. Experiment with two task windows
sharing the same sort field but with different `S' states and see which representation you prefer.
After issuing this command, you'll be informed of the new state of this toggle. If you wish to know in
advance whether or not Cumulative mode is in effect, simply ask for help and view the window summary on the
second line.
u | U :Show-Specific-User-Only
You will be prompted for the uid or name of the user to display. The -u option matches on effective user
whereas the -U option matches on any user (real, effective, saved, or filesystem).
Thereafter, in that task window only matching users will be shown, or possibly no processes will be shown.
Prepending an exclamation point (`!') to the user id or name instructs top to display only processes with
users not matching the one provided.
Different task windows can be used to filter different users. Later, if you wish to monitor all users again
in the `current' window, re-issue this command but just press <Enter> at the prompt.
V :Forest-View-Mode toggle
In this mode, processes are reordered according to their parents and the layout of the COMMAND column
resembles that of a tree. In forest view mode it is still possible to toggle between program name and command
line (see the `c' interactive command) or between processes and threads (see the `H' interactive command).
Note: Typing any key affecting the sort order will exit forest view mode in the `current' window. See topic
4c. TASK AREA Commands, SORTING for information on those keys.
v :Hide/Show-Children toggle
When in forest view mode, this key serves as a toggle to collapse or expand the children of a parent.
The toggle is applied against the first (topmost) process in the `current' window. See topic 5c. SCROLLING a
Window for additional information regarding vertical scrolling.
If the target process has not forked any children, this key has no effect. It also has no effect when not in
forest view mode.
SIZE of task window
i :Idle-Process toggle
Displays all tasks or just active tasks. When this toggle is Off, tasks that have not used any CPU since the
last update will not be displayed. However, due to the granularity of the %CPU and TIME+ fields, some
processes may still be displayed that appear to have used no CPU.
If this command is applied to the last task display when in alternate-display mode, then it will not affect
the window's size, as all prior task displays will have already been painted.
n | # :Set-Maximum-Tasks
You will be prompted to enter the number of tasks to display. The lessor of your number and available screen
rows will be used.
When used in alternate-display mode, this is the command that gives you precise control over the size of each
currently visible task display, except for the very last. It will not affect the last window's size, as all
prior task displays will have already been painted.
Note: If you wish to increase the size of the last visible task display when in alternate-display mode, simply
decrease the size of the task display(s) above it.
SORTING of task window
For compatibility, this top supports most of the former top sort keys. Since this is primarily a service to
former top users, these commands do not appear on any help screen.
command sorted-field supported
A start time (non-display) No
M %MEM Yes
N PID Yes
P %CPU Yes
T TIME+ Yes
Before using any of the following sort provisions, top suggests that you temporarily turn on column highlighting
using the `x' interactive command. That will help ensure that the actual sort environment matches your intent.
The following interactive commands will only be honored when the current sort field is visible. The sort field
might not be visible because:
1) there is insufficient Screen Width
2) the `f' interactive command turned it Off
< :Move-Sort-Field-Left
Moves the sort column to the left unless the current sort field is the first field being displayed.
> :Move-Sort-Field-Right
Moves the sort column to the right unless the current sort field is the last field being displayed.
The following interactive commands will always be honored whether or not the current sort field is visible.
f | F :Fields-Management
These keys display a separate screen where you can change which field is used as the sort column, among
other functions. This can be a convenient way to simply verify the current sort field, when running top
with column highlighting turned Off.
R :Reverse/Normal-Sort-Field toggle
Using this interactive command you can alternate between high-to-low and low-to-high sorts.
Note: Field sorting uses internal values, not those in column display. Thus, the TTY and WCHAN fields will
violate strict ASCII collating sequence.
4d. COLOR Mapping
When you issue the `Z' interactive command, you will be presented with a separate screen. That screen can be used to
change the colors in just the `current' window or in all four windows before returning to the top display.
The following interactive commands are available.
4 upper case letters to select a target
8 numbers to select a color
normal toggles available
B :bold disable/enable
b :running tasks "bold"/reverse
z :color/mono
other commands available
a/w :apply, then go to next/prior
<Enter> :apply and exit
q :abandon current changes and exit
If you use `a' or `w' to cycle the targeted window, you will have applied the color scheme that was displayed when
you left that window. You can, of course, easily return to any window and reapply different colors or turn colors
Off completely with the `z' toggle.
The Color Mapping screen can also be used to change the `current' window/field group in either full-screen mode or
alternate-display mode. Whatever was targeted when `q' or <Enter> was pressed will be made current as you return to
the top display.
5. ALTERNATE-DISPLAY Provisions
5a. WINDOWS Overview
Field Groups/Windows:
In full-screen mode there is a single window represented by the entire screen. That single window can still be
changed to display 1 of 4 different field groups (see the `g' interactive command, repeated below). Each of the 4
field groups has a unique separately configurable summary area and its own configurable task area.
In alternate-display mode, those 4 underlying field groups can now be made visible simultaneously, or can be
turned Off individually at your command.
The summary area will always exist, even if it's only the message line. At any given time only one summary area
can be displayed. However, depending on your commands, there could be from zero to four separate task displays
currently showing on the screen.
Current Window:
The `current' window is the window associated with the summary area and the window to which task related commands
are always directed. Since in alternate-display mode you can toggle the task display Off, some commands might be
restricted for the `current' window.
A further complication arises when you have toggled the first summary area line Off. With the loss of the window
name (the `l' toggled line), you'll not easily know what window is the `current' window.
5b. COMMANDS for Windows
- | _ :Show/Hide-Window(s) toggles
The `-' key turns the `current' window's task display On and Off. When On, that task area will show a minimum
of the columns header you've established with the `f' interactive command. It will also reflect any other
task area options/toggles you've applied yielding zero or more tasks.
The `_' key does the same for all task displays. In other words, it switches between the currently visible
task display(s) and any task display(s) you had toggled Off. If all 4 task displays are currently visible,
this interactive command will leave the summary area as the only display element.
* = | + :Equalize/Reset-Window(s)
The `=' key forces the `current' window's task display to be visible. It also reverses any active `i' (idle
tasks), `n' (max tasks), `u/U' (user filter), `o/O' (other filter), `v' (hide children), `L' (locate) and `!'
(combine cpus) commands. Also, if the window had been scrolled, it will be reset with this command. See
topic 5c. SCROLLING a Window for additional information regarding vertical and horizontal scrolling.
The `+' key does the same for all windows. The four task displays will reappear, evenly balanced, while
retaining any customizations previously applied beyond those noted for the `=' command toggle.
* A :Alternate-Display-Mode toggle
This command will switch between full-screen mode and alternate-display mode.
The first time you issue this command, all four task displays will be shown. Thereafter when you switch
modes, you will see only the task display(s) you've chosen to make visible.
* a | w :Next-Window-Forward/Backward
This will change the `current' window, which in turn changes the window to which commands are directed. These
keys act in a circular fashion so you can reach any desired window using either key.
Assuming the window name is visible (you have not toggled `l' Off), whenever the `current' window name loses
its emphasis/color, that's a reminder the task display is Off and many commands will be restricted.
* g :Choose-Another-Window/Field-Group
You will be prompted to enter a number between 1 and 4 designating the field group which should be made the
`current' window.
In full-screen mode, this command is necessary to alter the `current' window. In alternate-display mode, it
is simply a less convenient alternative to the `a' and `w' commands.
G :Change-Window/Field-Group-Name
You will be prompted for a new name to be applied to the `current' window. It does not require that the
window name be visible (the `l' toggle to be On).
* The interactive commands shown with an asterisk (`*') have use beyond alternate-display mode.
=, A, g are always available
a, w act the same with color mapping
and fields management
5c. SCROLLING a Window
Typically a task window is a partial view into a systems's total tasks/threads which shows only some of the available
fields/columns. With these scrolling keys, you can move that view vertically or horizontally to reveal any desired
task or column.
Up,PgUp :Scroll-Tasks
Move the view up toward the first task row, until the first task is displayed at the top of the `current' window.
The Up arrow key moves a single line while PgUp scrolls the entire window.
Down,PgDn :Scroll-Tasks
Move the view down toward the last task row, until the last task is the only task displayed at the top of the
`current' window. The Down arrow key moves a single line while PgDn scrolls the entire window.
Left,Right :Scroll-Columns
Move the view of displayable fields horizontally one column at a time.
Note: As a reminder, some fields/columns are not fixed-width but allocated all remaining screen width when
visible. When scrolling right or left, that feature may produce some unexpected results initially.
Additionally, there are special provisions for any variable width field when positioned as the last displayed
field. Once that field is reached via the right arrow key, and is thus the only column shown, you can continue
scrolling horizontally within such a field. See the `C' interactive command below for additional information.
Home :Jump-to-Home-Position
Reposition the display to the un-scrolled coordinates.
End :Jump-to-End-Position
Reposition the display so that the rightmost column reflects the last displayable field and the bottom task row
represents the last task.
Note: From this position it is still possible to scroll down and right using the arrow keys. This is true until
a single column and a single task is left as the only display element.
C :Show-scroll-coordinates toggle
Toggle an informational message which is displayed whenever the message line is not otherwise being used. That
message will take one of two forms depending on whether or not a variable width column has also been scrolled.
scroll coordinates: y = n/n (tasks), x = n/n (fields)
scroll coordinates: y = n/n (tasks), x = n/n (fields) + nn
The coordinates shown as n/n are relative to the upper left corner of the `current' window. The additional
`+ nn' represents the displacement into a variable width column when it has been scrolled horizontally. Such
displacement occurs in normal 8 character tab stop amounts via the right and left arrow keys.
y = n/n (tasks)
The first n represents the topmost visible task and is controlled by scrolling keys. The second n is updated
automatically to reflect total tasks.
x = n/n (fields)
The first n represents the leftmost displayed column and is controlled by scrolling keys. The second n is
the total number of displayable fields and is established with the `f' interactive command.
The above interactive commands are always available in full-screen mode but never available in alternate-display mode
if the `current' window's task display has been toggled Off.
Note: When any form of filtering is active, you can expect some slight aberrations when scrolling since not all tasks
will be visible. This is particularly apparent when using the Up/Down arrow keys.
5d. SEARCHING in a Window
You can use these interactive commands to locate a task row containing a particular value.
L :Locate-a-string
You will be prompted for the case-sensitive string to locate starting from the current window coordinates. There
are no restrictions on search string content.
Searches are not limited to values from a single field or column. All of the values displayed in a task row are
allowed in a search string. You may include spaces, numbers, symbols and even forest view artwork.
Keying <Enter> with no input will effectively disable the `&' key until a new search string is entered.
& :Locate-next
Assuming a search string has been established, top will attempt to locate the next occurrence.
When a match is found, the current window is repositioned vertically so the task row containing that string is first.
The scroll coordinates message can provide confirmation of such vertical repositioning (see the `C' interactive
command). Horizontal scrolling, however, is never altered via searching.
The availability of a matching string will be influenced by the following factors.
a. Which fields are displayable from the total available,
see topic 3b. MANAGING Fields.
b. Scrolling a window vertically and/or horizontally,
see topic 5c. SCROLLING a Window.
c. The state of the command/command-line toggle,
see the `c' interactive command.
d. The stability of the chosen sort column,
for example PID is good but %CPU bad.
If a search fails, restoring the `current' window home (unscrolled) position, scrolling horizontally, displaying
command-lines or choosing a more stable sort field could yet produce a successful `&' search.
The above interactive commands are always available in full-screen mode but never available in alternate-display mode
if the `current' window's task display has been toggled Off.
Note: Whenever a Search is active in a window, top will turn column highlighting Off to prevent false matches on
internal non-display escape sequences. Such highlighting will be restored when a window's search string is empty.
See the `x' interactive command for additional information on sort column highlighting.
5e. FILTERING in a Window
You can use this `Other Filter' feature to establish selection criteria which will then determine which tasks are
shown in the `current' window. Such filters can be made presistent if preserved in the rcfile via the 'W'
interactive command.
Establishing a filter requires: 1) a field name; 2) an operator; and 3) a selection value, as a minimum. This is the
most complex of top's user input requirements so, when you make a mistake, command recall will be your friend.
Remember the Up/Down arrow keys or their aliases when prompted for input.
Filter Basics
1. field names are case sensitive and spelled as in the header
2. selection values need not comprise the full displayed field
3. a selection is either case insensitive or sensitive to case
4. the default is inclusion, prepending `!' denotes exclusions
5. multiple selection criteria can be applied to a task window
6. inclusion and exclusion criteria can be used simultaneously
7. the 1 equality and 2 relational filters can be freely mixed
8. separate unique filters are maintained for each task window
If a field is not turned on or is not currently in view, then your selection criteria will not affect the display.
Later, should a filtered field become visible, the selection criteria will then be applied.
Keyboard Summary
o :Other-Filter (lower case)
You will be prompted to establish a filter that ignores case when matching.
O :Other-Filter (upper case)
You will be prompted to establish a case sensitive filter.
^O :Show-Active-Filters (Ctrl key + `o')
This can serve as a reminder of which filters are active in the `current' window. A summary will be shown on
the message line until you press the <Enter> key.
= :Reset-Filtering in current window
This clears all of your selection criteria in the `current' window. It also has additional impact so please
see topic 4a. GLOBAL Commands.
+ :Reset-Filtering in all windows
This clears the selection criteria in all windows, assuming you are in alternate-display mode. As with the `='
interactive command, it too has additional consequences so you might wish to see topic 5b. COMMANDS for
Windows.
Input Requirements
When prompted for selection criteria, the data you provide must take one of two forms. There are 3 required
pieces of information, with a 4th as optional. These examples use spaces for clarity but your input generally
would not.
#1 #2 #3 ( required )
Field-Name ? include-if-value
! Field-Name ? exclude-if-value
#4 ( optional )
Items #1, #3 and #4 should be self-explanatory. Item #2 represents both a required delimiter and the operator
which must be one of either equality (`=') or relation (`<' or `>').
The `=' equality operator requires only a partial match and that can reduce your `if-value' input requirements.
The `>' or `<' relational operators always employ string comparisons, even with numeric fields. They are designed
to work with a field's default justification and with homogeneous data. When some field's numeric amounts have
been subjected to scaling while others have not, that data is no longer homogeneous.
If you establish a relational filter and you have changed the default Numeric or Character justification, that
filter is likely to fail. When a relational filter is applied to a memory field and you have not changed the
scaling, it may produce misleading results. This happens, for example, because `100.0m' (MiB) would appear
greater than `1.000g' (GiB) when compared as strings.
If your filtered results appear suspect, simply altering justification or scaling may yet achieve the desired
objective. See the `j', `J' and `e' interactive commands for additional information.
Potential Problems
These GROUP filters could produce the exact same results or the second one might not display anything at all, just
a blank task window.
GROUP=root ( only the same results when )
GROUP=ROOT ( invoked via lower case `o' )
Either of these RES filters might yield inconsistent and/or misleading results, depending on the current memory
scaling factor. Or both filters could produce the exact same results.
RES>9999 ( only the same results when )
!RES<10000 ( memory scaling is at `KiB' )
This nMin filter illustrates a problem unique to scalable fields. This particular field can display a maximum of
4 digits, beyond which values are automatically scaled to KiB or above. So while amounts greater than 9999 exist,
they will appear as 2.6m, 197k, etc.
nMin>9999 ( always a blank task window )
Potential Solutions
These examples illustrate how Other Filtering can be creatively applied to achieve almost any desired result.
Single quotes are sometimes shown to delimit the spaces which are part of a filter or to represent a request for
status (^O) accurately. But if you used them with if-values in real life, no matches would be found.
Assuming field nTH is displayed, the first filter will result in only multi-threaded processes being shown. It
also reminds us that a trailing space is part of every displayed field. The second filter achieves the exact same
results with less typing.
!nTH=` 1 ' ( ' for clarity only )
nTH>1 ( same with less i/p )
With Forest View mode active and the COMMAND column in view, this filter effectively collapses child processes so
that just 3 levels are shown.
!COMMAND=` `- ' ( ' for clarity only )
The final two filters appear as in response to the status request key (^O). In reality, each filter would have
required separate input. The PR example shows the two concurrent filters necessary to display tasks with
priorities of 20 or more, since some might be negative. Then by exploiting trailing spaces, the nMin series of
filters could achieve the failed `9999' objective discussed above.
`PR>20' + `!PR=-' ( 2 for right result )
`!nMin=0 ' + `!nMin=1 ' + `!nMin=2 ' + `!nMin=3 ' ...
Note: Whenever Other Filtering is active in a window, top will turn column highlighting Off to prevent false matches
on internal non-display escape sequences. Such highlighting will be restored when a window is no longer subject to
filtering. See the `x' interactive command for additional information on sort column highlighting.
6. FILES
6a. PERSONAL Configuration File
This file is created or updated via the 'W' interactive command.
The legacy version is written as `$HOME/.your-name-4-top' + `rc' with a leading period.
A newly created configuration file is written as procps/your-name-4-top' + `rc' without a leading period. The procps
directory will be subordinate to either $XDG_CONFIG_HOME when set as an absolute path or the $HOME/.config directory.
While not intended to be edited manually, here is the general layout:
global # line 1: the program name/alias notation
" # line 2: id,altscr,irixps,delay,curwin
per ea # line a: winname,fieldscur
window # line b: winflags,sortindx,maxtasks,etc
" # line c: summclr,msgsclr,headclr,taskclr
global # line 15: additional miscellaneous settings
" # any remaining lines are devoted to optional
" # active 'other filters' discussed in section 5e above
" # plus 'inspect' entries discussed in section 6b below
If a valid absolute path to the rcfile cannot be established, customizations made to a running top will be impossible
to preserve.
6b. ADDING INSPECT Entries
To exploit the `Y' interactive command, you must add entries at the end of the top personal configuration file. Such
entries simply reflect a file to be read or command/pipeline to be executed whose results will then be displayed in a
separate scrollable, searchable window.
If you don't know the location or name of your top rcfile, use the `W' interactive command to rewrite it and note
those details.
Inspect entries can be added with a redirected echo or by editing the configuration file. Redirecting an echo risks
overwriting the rcfile should it replace (>) rather than append (>>) to that file. Conversely, when using an editor
care must be taken not to corrupt existing lines, some of which will contain unprintable data or unusual characters.
Those Inspect entries beginning with a `#' character are ignored, regardless of content. Otherwise they consist of
the following 3 elements, each of which must be separated by a tab character (thus 2 `\t' total):
.type: literal `file' or `pipe'
.name: selection shown on the Inspect screen
.fmts: string representing a path or command
The two types of Inspect entries are not interchangeable. Those designated `file' will be accessed using fopen and
must reference a single file in the `.fmts' element. Entries specifying `pipe' will employ popen, their `.fmts'
element could contain many pipelined commands and, none can be interactive.
If the file or pipeline represented in your `.fmts' deals with the specific PID input or accepted when prompted, then
the format string must also contain the `%d' specifier, as these examples illustrate.
.fmts= /proc/%d/numa_maps
.fmts= lsof -P -p %d
For `pipe' type entries only, you may also wish to redirect stderr to stdout for a more comprehensive result. Thus
the format string becomes:
.fmts= pmap -x %d 2>&1
Here are examples of both types of Inspect entries as they might appear in the rcfile. The first entry will be
ignored due to the initial `#' character. For clarity, the pseudo tab depictions (^I) are surrounded by an extra
space but the actual tabs would not be.
# pipe ^I Sockets ^I lsof -n -P -i 2>&1
pipe ^I Open Files ^I lsof -P -p %d 2>&1
file ^I NUMA Info ^I /proc/%d/numa_maps
pipe ^I Log ^I tail -n100 /var/log/syslog | sort -Mr
Except for the commented entry above, these next examples show what could be echoed to achieve similar results,
assuming the rcfile name was `.toprc'. However, due to the embedded tab characters, each of these lines should be
preceded by `/bin/echo -e', not just a simple an `echo', to enable backslash interpretation regardless of which shell
you use.
"pipe\tOpen Files\tlsof -P -p %d 2>&1" >> ~/.toprc
"file\tNUMA Info\t/proc/%d/numa_maps" >> ~/.toprc
"pipe\tLog\ttail -n200 /var/log/syslog | sort -Mr" >> ~/.toprc
If any inspect entry you create produces output with unprintable characters they will be displayed in either the ^C
notation or hexadecimal <FF> form, depending on their value. This applies to tab characters as well, which will show
as `^I'. If you want a truer representation, any embedded tabs should be expanded. The following example takes what
could have been a `file' entry but employs a `pipe' instead so as to expand the embedded tabs.
# next would have contained `\t' ...
# file ^I <your_name> ^I /proc/%d/status
# but this will eliminate embedded `\t' ...
pipe ^I <your_name> ^I cat /proc/%d/status | expand -
Note: Some programs might rely on SIGINT to end. Therefore, if a `pipe' such as the following is established, one
must use Ctrl-C to terminate it in order to review the results. This is the single occasion where a `^C' will not
also terminate top.
pipe ^I Trace ^I /usr/bin/strace -p %d 2>&1
Lastly, while `pipe' type entries have been discussed in terms of pipelines and commands, there is nothing to prevent
you from including shell scripts as well. Perhaps even newly created scripts designed specifically for the `Y'
interactive command.
For example, as the number of your Inspect entries grows over time, the `Options:' row will be truncated when screen
width is exceeded. That does not affect operation other than to make some selections invisible. However, if some
choices are lost to truncation but you want to see more options, there is an easy solution hinted at below.
Inspection Pause at pid ...
Use: left/right then <Enter> ...
Options: help 1 2 3 4 5 6 7 8 9 10 11 ...
The entries in the top rcfile would have a number for the `.name' element and the `help' entry would identify a shell
script you've written explaining what those numbered selections actually mean. In that way, many more choices can be
made visible.
6c. SYSTEM Configuration File
This configuration file represents defaults for users who have not saved their own configuration file. The format
mirrors exactly the personal configuration file and can also include `inspect' entries as explained above.
Creating it is a simple process.
1. Configure top appropriately for your installation and preserve that configuration with the `W' interactive
command.
2. Add and test any desired `inspect' entries.
3. Copy that configuration file to the /etc/ directory as `topdefaultrc'.
6d. SYSTEM Restrictions File
The presence of this file will influence which version of the help screen is shown to an ordinary user.
More importantly, it will limit what ordinary users are allowed to do when top is running. They will not be able to
issue the following commands.
k Kill a task
r Renice a task
d or s Change delay/sleep interval
This configuration file is not created by top. Rather, it is created manually and placed it in the /etc/ directory
as `toprc'.
It should have exactly two lines, as shown in this example:
s # line 1: secure mode switch
5.0 # line 2: delay interval in seconds
7. STUPID TRICKS Sampler
Many of these tricks work best when you give top a scheduling boost. So plan on starting him with a nice value of
-10, assuming you've got the authority.
7a. Kernel Magic
For these stupid tricks, top needs full-screen mode.
• The user interface, through prompts and help, intentionally implies that the delay interval is limited to tenths
of a second. However, you're free to set any desired delay. If you want to see Linux at his scheduling best, try
a delay of .09 seconds or less.
For this experiment, under x-windows open an xterm and maximize it. Then do the following:
. provide a scheduling boost and tiny delay via:
nice -n -10 top -d.09
. keep sorted column highlighting Off so as to
minimize path length
. turn On reverse row highlighting for emphasis
. try various sort columns (TIME/MEM work well),
and normal or reverse sorts to bring the most
active processes into view
What you'll see is a very busy Linux doing what he's always done for you, but there was no program available to
illustrate this.
• Under an xterm using `white-on-black' colors, on top's Color Mapping screen set the task color to black and be
sure that task highlighting is set to bold, not reverse. Then set the delay interval to around .3 seconds.
After bringing the most active processes into view, what you'll see are the ghostly images of just the currently
running tasks.
• Delete the existing rcfile, or create a new symlink. Start this new version then type `T' (a secret key, see
topic 4c. Task Area Commands, SORTING) followed by `W' and `q'. Finally, restart the program with -d0 (zero
delay).
Your display will be refreshed at three times the rate of the former top, a 300% speed advantage. As top climbs
the TIME ladder, be as patient as you can while speculating on whether or not top will ever reach the top.
7b. Bouncing Windows
For these stupid tricks, top needs alternate-display mode.
• With 3 or 4 task displays visible, pick any window other than the last and turn idle processes Off using the `i'
command toggle. Depending on where you applied `i', sometimes several task displays are bouncing and sometimes
it's like an accordion, as top tries his best to allocate space.
• Set each window's summary lines differently: one with no memory (`m'); another with no states (`t'); maybe one
with nothing at all, just the message line. Then hold down `a' or `w' and watch a variation on bouncing windows
-- hopping windows.
• Display all 4 windows and for each, in turn, set idle processes to Off using the `i' command toggle. You've just
entered the "extreme bounce" zone.
7c. The Big Bird Window
This stupid trick also requires alternate-display mode.
• Display all 4 windows and make sure that 1:Def is the `current' window. Then, keep increasing window size with
the `n' interactive command until all the other task displays are "pushed out of the nest".
When they've all been displaced, toggle between all visible/invisible windows using the `_' command toggle. Then
ponder this:
is top fibbing or telling honestly your imposed truth?
7d. The Ol' Switcheroo
This stupid trick works best without alternate-display mode, since justification is active on a per window basis.
• Start top and make COMMAND the last (rightmost) column displayed. If necessary, use the `c' command toggle to
display command lines and ensure that forest view mode is active with the `V' command toggle.
Then use the up/down arrow keys to position the display so that some truncated command lines are shown (`+' in
last position). You may have to resize your xterm to produce truncation.
Lastly, use the `j' command toggle to make the COMMAND column right justified.
Now use the right arrow key to reach the COMMAND column. Continuing with the right arrow key, watch closely the
direction of travel for the command lines being shown.
some lines travel left, while others travel right
eventually all lines will Switcheroo, and move right
8. BUGS
Please send bug reports to ⟨procps@freelists.org⟩.
9. SEE Also
free(1), ps(1), uptime(1), atop(1), slabtop(1), vmstat(8), w(1)
procps-ng September 2020 TOP(1)
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