atop Man page

ATOP(1) General Commands Manual ATOP(1)

NAME

atop – AT Computing’s System & Process Monitor

SYNOPSIS

Interactive usage:

atop [-g|-m|-d|-n|-u|-p|-s|-c|-v|-o] [-C|-M|-D|-N|-A] [-af1x] [-L line‐
len] [-Plabel[,label]…] [ interval [ samples ]]

Writing and reading raw logfiles:

atop -w rawfile [-a] [-S] [ interval [ samples ]] atop -r [ rawfile ] [-b hh:mm ] [-e hh:mm ] [-g|-m|-d|-n|-u|-p|-s|-c|-v|-o] [-C|-M|-D|-N|-A] [-f1x] [-L linelen] [-Plabel[,label]…]

DESCRIPTION

The program atop is an interactive monitor to view the load on a Linux
system. It shows the occupation of the most critical hardware
resources (from a performance point of view) on system level, i.e. cpu,
memory, disk and network.
It also shows which processes are responsible for the indicated load
with respect to cpu- and memory load on process level. Disk load is
shown if per process “storage accounting” is active in the kernel or if
the kernel patch `cnt’ has been installed. Network load is only shown
per process if the kernel patch `cnt’ has been installed.

Every interval (default: 10 seconds) information is shown about the
resource occupation on system level (cpu, memory, disks and network
layers), followed by a list of processes which have been active during
the last interval (note that all processes that were unchanged during
the last interval are not shown, unless the key ‘a’ has been pressed).
If the list of active processes does not entirely fit on the screen,
only the top of the list is shown (sorted in order of activity).
The intervals are repeated till the number of samples (specified as
command argument) is reached, or till the key ‘q’ is pressed in inter‐
active mode.

When atop is started, it checks whether the standard output channel is
connected to a screen, or to a file/pipe. In the first case it produces
screen control codes (via the ncurses library) and behaves interac‐
tively; in the second case it produces flat ASCII-output.

In interactive mode, the output of atop scales dynamically to the cur‐
rent dimensions of the screen/window.
If the window is resized horizontally, columns will be added or removed
automatically. For this purpose, every column has a particular weight.
The columns with the highest weigths that fit within the current width
will be shown.
If the window is resized vertically, lines of the process-list will be
added or removed automatically.

Furthermore in interactive mode the output of atop can be controlled by
pressing particular keys. However it is also possible to specify such
key as flag on the command line. In the latter case atop will switch to
the indicated mode on beforehand; this mode can be modified again
interactively. Specifying such key as flag is especially useful when
running atop with output to a pipe or file (non-interactively). The
flags used are the same as the keys which can be pressed in interactive
mode (see section INTERACTIVE COMMANDS).
Additional flags are available to support storage of atop-data in raw
format (see section RAW DATA STORAGE).

PROCESS ACCOUNTING
When atop is started, it switches on the process accounting mechanism
in the kernel. This forces the kernel to write a record with accounting
information to the accounting file whenever a process ends. Apart from
the kernel administration related to the running processes, atop also
interprets the accounting records on disk with every interval; in this
way atop can also show the activity of a process during the interval in
which it is finished.
Whenever the last incarnation of atop stops (either by pressing `q’ or
by `kill -15′), it switches off the process accounting mechanism again.
You should never terminate atop by `kill -9′, because then it has no
chance to stop process accounting; as a result the accounting file may
consume a lot of disk space after a while.

With the environment variable ATOPACCT the name of a specific process
accounting file can be specified (accounting should have been activated
on beforehand). When this environment variable is present but its con‐
tents is empty, process accounting will not be used at all.

Notice that root-privileges are required to switch on process account‐
ing in the kernel. You can start atop as root or specify setuid-root
privileges to the executable file. In the latter case, atop switches
on process accounting and immediately drops the root-privileges again.

COLORS
For the resource consumption on system level, atop uses colors to indi‐
cate that a critical occupation percentage has been (almost) reached.
A critical occupation percentage means that is likely that this load
causes a noticable negative performance influence for applications
using this resource. The critical percentage depends on the type of
resource: e.g. the performance influence of a disk with a busy percent‐
age of 80% might be more noticable for applications/user than a CPU
with a busy percentage of 90%.
Currently atop uses the following default values to calculate a
weighted percentage per resource:

Processor
A busy percentage of 90% or higher is considered `critical’.

Disk
A busy percentage of 70% or higher is considered `critical’.

Network
A busy percentage of 90% or higher for the load of an interface is
considered `critical’.

Memory
An occupation percentage of 90% is considered `critical’. Notice
that this occupation percentage is the accumulated memory consump‐
tion of the kernel (including slab) and all processes; the memory
for the page cache (`cache’ and `buff’ in the MEM-line) is not
implied!
If the number of pages swapped out (`swout’ in the PAG-line) is
larger than 10 per second, the memory resource is considered
`critical’. A value of at least 1 per second is considered
`almost critical’.
If the committed virtual memory exceeds the limit (`vmcom’ and
`vmlim’ in the SWP-line), the SWP-line is colored due to overcom‐
mitting the system.

Swap
An occupation percentage of 80% is considered `critical’ because
swap space might be completely exhausted in the near future; it is
not critical from a performance point-of-view.

These default values can be modified in the configuration file (see
separate man-page of atoprc).

When a resource exceeded its critical occupation percentage, the entire
screen line is colored red.
When a resource exceeded (default) 80% of its critical percentage (so
it is almost critical), the entire screen line is colored cyan. This
`almost critical percentage’ (one value for all resources) can be modi‐
fied in the configuration file (see separate man-page of atoprc).

With the key ‘x’ (or flag -x), line coloring can be suppressed.

INTERACTIVE COMMANDS
When running atop interactively (no output redirection), keys can be
pressed to control the output. In general, lower case keys can be used
to show other information for the active processes and upper case keys
can be used to influence the sort order of the active process list.

g Show generic output (default).

Per process the following fields are shown in case of a window-
width of 80 positions: process-id, cpu consumption during the last
interval in system- and user mode, the virtual and resident memory
growth of the process.
The subsequent columns depend on the used kernel: When the kernel
patch `cnt’ has been installed, the number of read- and write
transfers on disk, and the number of received and transmitted net‐
work packets are shown for each process. When the kernel patch is
not installed and the kernel supports “storage accounting” (>=
2.6.20), the data transfer for read/write on disk, the status and
exit code are shown for each process. When the kernel patch is
not installed and the kernel does not support “storage account‐
ing”, the username, number of threads in the thread group, the
status and exit code are shown.
The last columns contain the state, the occupation percentage for
the choosen resource (default: cpu) and the process name.

When more than 80 positions are available, other information is
added.

m Show memory related output.

Per process the following fields are shown in case of a window-
width of 80 positions: process-id, minor and major memory faults,
size of virtual shared text, total virtual process size, total
resident process size, virtual and resident growth during last
interval, memory occupation percentage and process name.

When more than 80 positions are available, other information is
added.

d Show disk-related output.

When “storage accounting” is active in the kernel, the following
fields are shown: process-id, amount of data read from disk,
amount of data written to disk, amount of data that was written
but has been withdrawn again (WCANCL), disk occupation percentage
and process name.

When the kernel patch `cnt’ is installed in the kernel, the fol‐
lowing fields are shown: process-id, number of physical disk
reads, average size per read (bytes), total size for read trans‐
fers, physical disk writes, average size per write (bytes), total
size for write transfers, disk occupation percentage and process
name.

n Show network related output.

Per process the following fields are shown in case of a window-
width of 80 positions: process-id, number of received TCP packets
with the average size per packet (in bytes), number of sent TCP
packets with the average size per packet (in bytes), number of
received UDP packets with the average size per packet (in bytes),
number of sent UDP packets with the average size per packet (in
bytes), and received and sent raw packets (e.g. ICMP) in one col‐
umn, the network occupation percentage and process name.
This information can only be shown when kernel patch `cnt’ is
installed.

When more than 80 positions are available, other information is
added.

s Show scheduling characteristics.

Per process the following fields are shown in case of a window-
width of 80 positions: process-id, number of threads in state
‘running’ (R), number of threads in state ‘interruptible sleeping’
(S), number of threads in state ‘uninterruptible sleeping’ (D),
scheduling policy (normal timesharing, realtime round-robin, real‐
time fifo), nice value, priority, realtime priority, current pro‐
cessor, status, exit code, state, the occupation percentage for
the choosen resource and the process name.

When more than 80 positions are available, other information is
added.

v Show various process characteristics.

Per process the following fields are shown in case of a window-
width of 80 positions: process-id, user name and group, start date
and time, status (e.g. exit code if the process has finished),
state, the occupation percentage for the choosen resource and the
process name.

When more than 80 positions are available, other information is
added.

c Show the command line of the process.

Per process the following fields are shown: process-id, the occu‐
pation percentage for the choosen resource and the command line
including arguments.

o Show the user-defined line of the process.

In the configuration file the keyword ownprocline can be specified
with the description of a user-defined output-line.
Refer to the man-page of atoprc for a detailed description.

u Show the process activity accumulated per user.

Per user the following fields are shown: number of processes
active or terminated during last interval (or in total if combined
with command `a’), accumulated cpu consumption during last inter‐
val in system- and user mode, the current virtual and resident
memory space consumed by active processes (or all processes of the
user if combined with command `a’).
When the kernel patch `cnt’ has been installed or “storage
accounting” is active, the accumulated read- and write throughput
on disk is shown. When the kernel patch `cnt’ has been installed,
the number of received and sent network packets are shown.
The last columns contain the accumulated occupation percentage for
the choosen resource (default: cpu) and the user name.

p Show the process activity accumulated per program (i.e. process
name).

Per program the following fields are shown: number of processes
active or terminated during last interval (or in total if combined
with command `a’), accumulated cpu consumption during last inter‐
val in system- and user mode, the current virtual and resident
memory space consumed by active processes (or all processes of the
user if combined with command `a’).
When the kernel patch `cnt’ has been installed or “storage
accounting” is active, the accumulated read- and write throughput
on disk is shown. When the kernel patch `cnt’ has been installed,
the number of received and sent network packets are shown.
The last columns contain the accumulated occupation percentage for
the choosen resource (default: cpu) and the program name.

C Sort the current list in the order of cpu consumption (default).
The one-but-last column changes to “CPU”.

M Sort the current list in the order of resident memory consumption.
The one-but-last column changes to “MEM”.

D Sort the current list in the order of disk accesses issued. The
one-but-last column changes to “DSK”.

N Sort the current list in the order of network packets
received/transmitted. The one-but-last column changes to “NET”.

A Sort the current list automatically in the order of the most busy
system resource during this interval. The one-but-last column
shows either “ACPU”, “AMEM”, “ADSK” or “ANET” (the preced‐
ing ‘A’ indicates automatic sorting-order). The most busy
resource is determined by comparing the weighted busy-percentages
of the system resources, as described earlier in the section COL‐
ORS.
This option remains valid until another sorting-order is explic‐
itly selected again.
A sorting-order for disk is only possible when the kernel patch
`cnt’ is installed or “storage accounting” is active. A sorting-
order for network is only possible when the kernel patch `cnt’ is
installed.

Miscellaneous interactive commands:

? Request for help information (also the key ‘h’ can be pressed).

V Request for version information (version number and date).

x Suppress colors to highlight critical resources (toggle).
Whether this key is active or not can be seen in the header line.

z The pause key can be used to freeze the current situation in order
to investigate the output on the screen. While atop is paused, the
keys described above can be pressed to show other information
about the current list of processes. Whenever the pause key is
pressed again, atop will continue with a next sample.

i Modify the interval timer (default: 10 seconds). If an interval
timer of 0 is entered, the interval timer is switched off. In that
case a new sample can only be triggered manually by pressing the
key ‘t’.

t Trigger a new sample manually. This key can be pressed if the cur‐
rent sample should be finished before the timer has exceeded, or
if no timer is set at all (interval timer defined as 0). In the
latter case atop can be used as a stopwatch to measure the load
being caused by a particular application transaction, without
knowing on beforehand how many seconds this transaction will last.

When viewing the contents of a raw file, this key can be used to
show the next sample from the file.

T When viewing the contents of a raw file, this key can be used to
show the previous sample from the file.

b When viewing the contents of a raw file, this key can be used to
branch to a certain timestamp within the file (either forward or
backward).

r Reset all counters to zero to see the system and process activity
since boot again.

When viewing the contents of a raw file, this key can be used to
rewind to the beginning of the file again.

U Specify a search string for specific user names as a regular
expression. From now on, only (active) processes will be shown
from a user which matches the regular expression. The system sta‐
tistics are still system wide. If the Enter-key is pressed with‐
out specifying a name, active processes of all users will be shown
again.
Whether this key is active or not can be seen in the header line.

P Specify a search string for specific process names as a regular
expression. From now on, only processes will be shown with a name
which matches the regular expression. The system statistics are
still system wide. If the Enter-key is pressed without specifying
a name, all active processes will be shown again.
Whether this key is active or not can be seen in the header line.

a The `all/active’ key can be used to toggle between only show‐
ing/accumulating the processes that were active during the last
interval (default) or showing/accumulating all processes.
Whether this key is active or not can be seen in the header line.

f Fixate the number of lines for system resources (toggle). By
default only the lines are shown about system resources (cpu, pag‐
ing, disk, network) that really have been active during the last
interval. With this key you can force atop to show lines of inac‐
tive resources as well.
Whether this key is active or not can be seen in the header line.

1 Show relevant counters as an average per second (in the format
`…./s’) instead of as a total during the interval (toggle).
Whether this key is active or not can be seen in the header line.

l Limit the number of system level lines for the counters per-cpu,
the active disks and the network interfaces. By default lines are
shown of all cpu’s, disks and network interfaces which have been
active during the last interval. Limiting these lines can be use‐
ful on systems with huge number cpu’s, disks or interfaces in
order to be able to run atop on a screen/window with e.g. only 24
lines.
For all mentioned resources the maximum number of lines can be
specified interactively. When using the flag -l the maximum number
of per-cpu lines is set to 0, the maximum number of disk lines to
5 and the maximum number of interface lines to 3. These values
can be modified again in interactive mode.

k Send a signal to an active process (a.k.a. kill a process).

q Quit the program.

^F Show the next page of the process list (forward).

^B Show the previous page of the process list (backward).

^L Redraw the screen.

RAW DATA STORAGE
In order to store system- and process level statistics for long-term
analysis (e.g. to check the system load and the active processes run‐
ning yesterday between 3:00 and 4:00 PM), atop can store the system-
and process level statistics in compressed binary format in a raw file
with the flag -w followed by the filename. If this file already exists
and is recognized as a raw data file, atop will append new samples to
the file (starting with a sample which reflects the activity since
boot); if the file does not exist, it will be created.
By default only processes which have been active during the interval
are stored in the raw file. When the flag -a is specified, all pro‐
cesses will be stored.
The interval (default: 10 seconds) and number of samples (default:
infinite) can be passed as last arguments. Instead of the number of
samples, the flag -S can be used to indicate that atop should finish
anyhow before midnight.

A raw file can be read and visualized again with the flag -r followed
by the filename. If no filename is specified, the file
/var/log/atop/atop_YYYYMMDD is opened for input (where YYYYMMDD are
digits representing the current date). If a filename is specified in
the format YYYYMMDD (representing any valid date), the file
/var/log/atop/atop_YYYYMMDD is opened. If a filename with the symbolic
name y is specified, yesterday’s daily logfile is opened (this can be
repeated so ‘yyyy’ indicates the logfile of four days ago).
The samples from the file can be viewed interactively by using the key
‘t’ to show the next sample, the key ‘T’ to show the previous sample,
the key ‘b’ to branch to a particular time or the key ‘r’ to rewind to
the begin of the file.
When output is redirected to a file or pipe, atop prints all samples in
plain ASCII. The default line length is 80 characters in that case;
with the flag -L followed by an alternate line length, more (or less)
columns will be shown.
With the flag -b (begin time) and/or -e (end time) followed by a time
argument of the form HH:MM, a certain time period within the raw file
can be selected.

When atop is installed, the script atop.daily is stored in the
/etc/atop directory. This scripts takes care that atop is activated
every day at midnight to write compressed binary data to the file
/var/log/atop/atop_YYYYMMDD with an interval of 10 minutes.
Furthermore the script removes all raw files which are older than four
weeks.
The script is activated via the cron daemon using the file
/etc/cron.d/atop with the contents
0 0 * * * root /etc/atop/atop.daily

When the RPM `psacct’ is installed, the process accounting is automati‐
cally restarted via the logrotate mechanism. The file /etc/logro‐
tate.d/psaccs_atop takes care that atop is finished just before the
rotation of the process accounting file and the file /etc/logro‐
tate.d/psaccu_atop takes care that atop is restarted again after the
rotation. When the RPM `psacct’ is not installed, these logrotate-
files have no effect.

OUTPUT

DESCRIPTION

The first sample shows the system level activity since boot (the
elapsed time in the header shows the time since boot). Note that par‐
ticular counters could have reached their maximum value (several times)
and started by zero again, so do not rely on these figures.

For every sample atop first shows the lines related to system level
activity. If a particular system resource has not been used during the
interval, the entire line related to this resource is suppressed. So
the number of system level lines may vary for each sample.
After that a list is shown of processes which have been active during
the last interval. This list is by default sorted on cpu consumption,
but this order can be changed by the keys which are previously
described.

If values have to be shown by atop which do not fit in the column
width, another notation is used. If e.g. a cpu-consumption of 233216
milliseconds should be shown in a column width of 4 positions, it is
shown as `233s’ (in seconds). For large memory figures, another unit
is chosen if the value does not fit (Mb instead of Kb, Gb instead of
Mb). For other values, a kind of exponent notation is used (value
123456789 shown in a column of 5 positions gives 123e6).

OUTPUT DESCRIPTION – SYSTEM LEVEL
The system level information consists of the following output lines:

PRC Process level totals.
This line contains the total cpu time consumed in system mode
(`sys’) and in user mode (`user’), the total number of processes
present at this moment (`#proc’), the total number of threads
present at this moment in state `running’ (`#trun’), `sleeping
interruptible’ (`#tslpi’) and `sleeping uninterruptible’
(`#tslpu’), the number of zombie processes (`#zombie’), the number
of clone system calls (`clones’), and the number of processes that
ended during the interval (`#exit’, which shows `?’ if process
accounting is not used).
If the screen-width does not allow all of these counters, only a
relevant subset is shown.

CPU CPU utilization.
At least one line is shown for the total occupation of all CPU’s
together.
In case of a multi-processor system, an additional line is shown
for every individual processor (with `cpu’ in lower case), sorted
on activity. Inactive cpu’s will not be shown by default. The
lines showing the per-cpu occupation contain the cpu number in the
last field.

Every line contains the percentage of cpu time spent in kernel
mode by all active processes (`sys’), the percentage of cpu time
consumed in user mode (`user’) for all active processes (including
processes running with a nice value larger than zero), the per‐
centage of cpu time spent for interrupt handling (`irq’) including
softirq, the percentage of unused cpu time while no processes were
waiting for disk-I/O (`idle’), and the percentage of unused cpu
time while at least one process was waiting for disk-I/O (`wait’).
In case of per-cpu occupation, the last column shows the cpu num‐
ber and the wait percentage (`w’) for that cpu. The number of
lines showing the per-cpu occupation can be limited.

For virtual machines the steal-percentage is shown (`steal’),
reflecting the percentage of cpu time stolen by other virtual
machines running on the same hardware.
For physical machines hosting one or more virtual machines, the
guest-percentage is shown (`guest’), reflecting the percentage of
cpu time used by the virtual machines.

In case of frequency-scaling, all previously mentioned CPU-per‐
centages are relative to the used scaling of the CPU during the
interval. If e.g. a CPU has been active for 50% in user mode dur‐
ing the interval while the frequency-scaling of that was 40%, then
only 20% of the full capacity of the CPU has been used in user
mode.
In case that the kernel module `cpufreq_stats’ is active (after
issueing `modprobe cpufreq_stats’), the average frequency (`avgf’)
and the average scaling percentage (`avgscal’) is shown. Otherwise
the current frequency (`curf’) and the current scaling percentage
(`curscal’) is shown at the moment that the sample is taken.

If the screen-width does not allow all of these counters, only a
relevant subset is shown.

CPL CPU load information.
This line contains the load average figures reflecting the number
of threads that are available to run on a CPU (i.e. part of the
runqueue) or that are waiting for disk I/O. These figures are
averaged over 1 (`avg1′), 5 (`avg5′) and 15 (`avg15′) minutes.
Furthermore the number of context switches (`csw’), the number of
serviced interrupts (`intr’) and the number of available cpu’s are
shown.

If the screen-width does not allow all of these counters, only a
relevant subset is shown.

MEM Memory occupation.
This line contains the total amount of physical memory (`tot’),
the amount of memory which is currently free (`free’), the amount
of memory in use as page cache (`cache’), the amount of memory
within the page cache that has to be flushed to disk (`dirty’),
the amount of memory used for filesystem meta data (`buff’) and
the amount of memory being used for kernel malloc’s (`slab’ –
always 0 for kernel 2.4).

If the screen-width does not allow all of these counters, only a
relevant subset is shown.

SWP Swap occupation and overcommit info.
This line contains the total amount of swap space on disk (`tot’)
and the amount of free swap space (`free’).
Furthermore the committed virtual memory space (`vmcom’) and the
maximum limit of the committed space (`vmlim’, which is by default
swap size plus 50% of memory size) is shown. The committed space
is the reserved virtual space for all allocations of private mem‐
ory space for processes. The kernel only verifies whether the com‐
mitted space exceeds the limit if strict overcommit handling is
configured (vm.overcommit_memory is 2).

PAG Paging frequency.
This line contains the number of scanned pages (`scan’) due to the
fact that free memory drops below a particular threshold and the
number times that the kernel tries to reclaim pages due to an
urgent need (`stall’).
Also the number of memory pages the system read from swap space
(`swin’) and the number of memory pages the system wrote to swap
space (`swout’) are shown.

LVM/MDD/DSK
Logical volume/multiple device/disk utilization.
Per active unit one line is produced, sorted on unit activity.
Such line shows the name (e.g. VolGroup00-lvtmp for a logical vol‐
ume or sda for a hard disk), the busy percentage i.e. the portion
of time that the unit was busy handling requests (`busy’), the
number of read requests issued (`read’), the number of write
requests issued (`write’), the number of KiBytes per read
(`KiB/r’), the number of KiBytes per write (`KiB/w’), the number
of MiBytes per second throughput for reads (`MBr/s’), the number
of MiBytes per second throughput for writes (`MBw/s’), the average
queue depth (`avq’) and the average number of milliseconds needed
by a request (`avio’) for seek, latency and data transfer.
If the screen-width does not allow all of these counters, only a
relevant subset is shown.

The number of lines showing the units can be limited per class
(LVM, MDD or DSK) with the ‘l’ key or statically (see separate
man-page of atoprc). By specifying the value 0 for a particular
class, no lines will be shown any more for that class.

NET Network utilization (TCP/IP).
One line is shown for activity of the transport layer (TCP and
UDP), one line for the IP layer and one line per active interface.
For the transport layer, counters are shown concerning the number
of received TCP segments including those received in error
(`tcpi’), the number of transmitted TCP segments excluding those
containing only retransmitted octets (`tcpo’), the number of UDP
datagrams received (`udpi’), the number of UDP datagrams transmit‐
ted (`udpo’), the number of active TCP opens (`tcpao’), the number
of passive TCP opens (`tcppo’), the number of TCP output retrans‐
missions (`tcprs’), the number of TCP input errors (`tcpie’), the
number of TCP output resets (`tcpie’), the number of TCP output
retransmissions (`tcpor’), the number of UDP no ports (`udpnp’),
and the number of UDP input errors (`tcpie’).
If the screen-width does not allow all of these counters, only a
relevant subset is shown.
These counters are related to IPv4 and IPv6 combined.

For the IP layer, counters are shown concerning the number of IP
datagrams received from interfaces, including those received in
error (`ipi’), the number of IP datagrams that local higher-layer
protocols offered for transmission (`ipo’), the number of received
IP datagrams which were forwarded to other interfaces (`ipfrw’),
the number of IP datagrams which were delivered to local higher-
layer protocols (`deliv’), the number of received ICMP datagrams
(`icmpi’), and the number of transmitted ICMP datagrams (`icmpo’).
If the screen-width does not allow all of these counters, only a
relevant subset is shown.
These counters are related to IPv4 and IPv6 combined.

For every active network interface one line is shown, sorted on
the interface activity. Such line shows the name of the interface
and its busy percentage in the first column. The busy percentage
for half duplex is determined by comparing the interface speed
with the number of bits transmitted and received per second; for
full duplex the interface speed is compared with the highest of
either the transmitted or the received bits. When the interface
speed can not be determined (e.g. for the loopback interface),
`—‘ is shown instead of the percentage.
Furthermore the number of received packets (`pcki’), the number of
transmitted packets (`pcko’), the effective amount of bits
received per second (`si’), the effective amount of bits transmit‐
ted per second (`so’), the number of collisions (`coll’), the num‐
ber of received multicast packets (`mlti’), the number of errors
while receiving a packet (`erri’), the number of errors while
transmitting a packet (`erro’), the number of received packets
dropped (`drpi’), and the number of transmitted packets dropped
(`drpo’).
If the screen-width does not allow all of these counters, only a
relevant subset is shown.
The number of lines showing the network interfaces can be limited.

OUTPUT DESCRIPTION – PROCESS LEVEL
Following the system level information, the processes are shown from
which the resource utilization has changed during the last interval.
These processes might have used cpu time or issued disk- or network
requests. However a process is also shown if part of it has been paged
out due to lack of memory (while the process itself was in sleep
state).

Per process the following fields may be shown (in alphabetical order),
depending on the current output mode as described in the section INTER‐
ACTIVE COMMANDS and depending on the current width of your window:

AVGRSZ The average size of one read-action on disk.

AVGWSZ The average size of one write-action on disk.

CMD The name of the process. This name can be surrounded by
“less/greater than” signs (`‘) which means that the
process has finished during the last interval.
Behind the abbreviation `CMD’ in the header line, the current
page number and the total number of pages of the process list
are shown.

COMMAND-LINE
The full command line of the process (including arguments),
which is limited to the length of the screen line. Th command
line can be surrounded by “less/greater than” signs (`‘)
which means that the process has finished during the last
interval.
Behind the verb `COMMAND-LINE’ in the header line, the current
page number and the total number of pages of the process list
are shown.

CPU The occupation percentage of this process related to the
available capacity for this resource on system level.

CPUNR The identification of the CPU the main thread of the process
is running on or has recently been running on.

DSK The occupation percentage of this process related to the total
load that is produced by all processes (i.e. total disk
accesses by all processes during the last interval).
This information is shown when per process “storage account‐
ing” is active in the kernel or when the kernel patch `cnt’
has been installed.

EGID Effective group-id under which this process executes.

ENDATE Date that the process has been finished. If the process is
still running, this field shows `active’.

ENTIME Time that the process has been finished. If the process is
still running, this field shows `active’.

EUID Effective user-id under which this process executes.

EXC The exit code of a terminated process (second position of col‐
umn `ST’ is E) or the fatal signal number (second position of
column `ST’ is S or C).

FSGID Filesystem group-id under which this process executes.

FSUID Filesystem user-id under which this process executes.

MAJFLT The number of page faults issued by this process that have
been solved by creating/loading the requested memory page.

MEM The occupation percentage of this process related to the
available capacity for this resource on system level.

MINFLT The number of page faults issued by this process that have
been solved by reclaiming the requested memory page from the
free list of pages.

NET The occupation percentage of this process related to the total
load that is produced by all processes (i.e. network packets
transferred by all processes during the last interval).
This information can only be shown when kernel patch `cnt’ is
installed.

NICE The more or less static priority that can be given to a proces
on a scale from -20 (high priority) to +19 (low priority).

NPROCS The number of active and terminated processes accumulated for
this user or program.

PID Process-id. If a process has been started and finished during
the last interval, a `?’ is shown because the process-id is
not part of the standard process accounting record. However
when the kernel patch `acct’ is installed, this value will be
shown properly.

POLI The policies ‘norm’ (normal, which is SCHED_OTHER), ‘btch’
(batch) and ‘idle’ refer to timesharing processes. The poli‐
cies ‘fifo’ (SCHED_FIFO) and ‘rr’ (round robin, which is
SCHED_RR) refer to realtime processes.

PPID Parent process-id. If a process has been started and finished
during the last interval, value 0 is shown because the parent
process-id is not part of the standard process accounting
record. However when the kernel patch `acct’ is installed,
this value will be shown properly.

PRI The process’ priority ranges from 0 (highest priority) to 139
(lowest priority). Priority 0 to 99 are used for realtime pro‐
cesses (fixed priority independent of their behavior) and pri‐
ority 100 to 139 for timesharing processes (variable priority
depending on their recent CPU consumption and the nice value).

RAWRCV The number of raw datagrams received by this process. This
information can only be shown when kernel patch `cnt’ is
installed.
If a process has finished during the last interval, no value
is shown since network counters are not registered in the
standard process accounting record. However when the kernel
patch `acct’ is installed, this value will be shown.

RAWSND The number of raw datagrams sent by this process. This infor‐
mation can only be shown when kernel patch `cnt’ is installed.
If a process has finished during the last interval, no value
is shown since network counters are not registered in the
standard process accounting record. However when the kernel
patch `acct’ is installed, this value will be shown.

RDDSK When the kernel maintains standard io statistics (>= 2.6.20):
The read data transfer issued physically on disk (so reading
from the disk cache is not accounted for).

When the kernel patch `cnt’ is installed:
The number of read accesses issued physically on disk (so
reading from the disk cache is not accounted for).

RGID The real group-id under which the process executes.

RGROW The amount of resident memory that the process has grown dur‐
ing the last interval. A resident growth can be caused by
touching memory pages which were not physically created/loaded
before (load-on-demand). Note that a resident growth can also
be negative e.g. when part of the process is paged out due to
lack of memory or when the process frees dynamically allocated
memory. For a process which started during the last interval,
the resident growth reflects the total resident size of the
process at that moment.
If a process has finished during the last interval, no value
is shown since resident memory occupation is not part of the
standard process accounting record. However when the kernel
patch `acct’ is installed, this value will be shown.

RNET The number of TCP- and UDP packets received by this process.
This information can only be shown when kernel patch `cnt’ is
installed.
If a process has finished during the last interval, no value
is shown since network counters are not part of the standard
process accounting record. However when the kernel patch
`acct’ is installed, this value will be shown.

RSIZE The total resident memory usage consumed by this process (or
user).
If a process has finished during the last interval, no value
is shown since resident memory occupation is not part of the
standard process accounting record. However when the kernel
patch `acct’ is installed, this value will be shown.

RTPR Realtime priority according the POSIX standard. Value can be
0 for a timesharing process (policy ‘norm’, ‘btch’ or ‘idle’)
or ranges from 1 (lowest) till 99 (highest) for a realtime
process (policy ‘rr’ or ‘fifo’).

RUID The real user-id under which the process executes.

S The current state of the main thread of the process: `R’ for
running (currently processing or in the runqueue), `S’ for
sleeping interruptible (wait for an event to occur), `D’ for
sleeping non-interruptible, `Z’ for zombie (waiting to be syn‐
chronized with its parent process), `T’ for stopped (suspended
or traced), `W’ for swapping, and `E’ (exit) for processes
which have finished during the last interval.

SGID The saved group-id of the process.

SNET The number of TCP- and UDP packets transmitted by this
process. This information can only be shown when kernel patch
`cnt’ is installed.
If a process has finished during the last interval, no value
is shown since network-counters are not part of the standard
process accounting record. However when the kernel patch
`acct’ is installed, this value will be shown.

ST The status of a process.
The first position indicates if the process has been started
during the last interval (the value N means ‘new process’).

The second position indicates if the process has been finished
during the last interval.
The value E means ‘exit’ on the process’ own initiative; the
exit code is displayed in the column `EXC’.
The value S means that the process has been terminated unvol‐
untarily by a signal; the signal number is displayed in the in
the column `EXC’.
The value C means that the process has been terminated unvol‐
untarily by a signal, producing a core dump in its current
directory; the signal number is displayed in the column `EXC’.

STDATE The start date of the process.

STTIME The start time of the process.

SUID The saved user-id of the process.

SYSCPU CPU time consumption of this process in system mode (kernel
mode), usually due to system call handling.

TCPRASZ The average size of a received TCP buffer in bytes (by the
process). This information can only be shown when kernel
patch `cnt’ is installed. When the kernel patch `acct’ is
installed as well, this value will also be shown when a
process has finished during the last interval.

TCPRCV The number of receive requests issued by this process for TCP
sockets. This information can only be shown when kernel patch
`cnt’ is installed. When the kernel patch `acct’ is installed
as well, this value will also be shown when a process has fin‐
ished during the last interval.

TCPSASZ The average size of a transmitted TCP buffer in bytes (by the
process). This information can only be shown when kernel
patch `cnt’ is installed. When the kernel patch `acct’ is
installed as well, this value will also be shown when a
process has finished during the last interval.

TCPSND The number of send requests issued by this process for TCP
sockets, and the average size per transfer in bytes. This
information can only be shown when kernel patch `cnt’ is
installed. When the kernel patch `acct’ is installed as well,
this value will also be shown when a process has finished dur‐
ing the last interval.

THR Total number of threads within this process. All related
threads are contained in a thread group, represented by atop
as one line.

On Linux 2.4 systems it is hardly possible to determine which
threads (i.e. processes) are related to the same thread group.
Every thread is represented by atop as a separate line.

TOTRSZ The total amount of data physically read from disk. This
information can only be shown when kernel patch `cnt’ is
installed.

TOTWSZ The total amount of data physically written to disk. This
information can only be shown when kernel patch `cnt’ is
installed.

TRUN Number of threads within this process that are in the state
‘running’ (R).

TSLPI Number of threads within this process that are in the state
‘interruptible sleeping’ (S).

TSLPU Number of threads within this process that are in the state
‘uninterruptible sleeping’ (D).

UDPRASZ The average size of a received UDP packet in bytes. This
information can only be shown when kernel patch `cnt’ is
installed. When the kernel patch `acct’ is installed as well,
this value will also be shown when a process has finished dur‐
ing the last interval.

UDPRCV The number of receive requests issued by this process for UDP
sockets. This information can only be shown when kernel patch
`cnt’ is installed. When the kernel patch `acct’ is installed
as well, this value will also be shown when a process has fin‐
ished during the last interval.

UDPSASZ The average size of a transmitted UDP packets in bytes. This
information can only be shown when kernel patch `cnt’ is
installed. When the kernel patch `acct’ is installed as well,
this value will also be shown when a process has finished dur‐
ing the last interval.

UDPSND The number of send requests issued by this process for TCP
sockets, and the average size per transfer in bytes. This
information can only be shown when kernel patch `cnt’ is
installed. When the kernel patch `acct’ is installed as well,
this value will also be shown when a process has finished dur‐
ing the last interval.

USRCPU CPU time consumption of this process in user mode, due to pro‐
cessing the own program text.

VGROW The amount of virtual memory that the process has grown during
the last interval. A virtual growth can be caused by e.g.
issueing a malloc() or attaching a shared memory segment. Note
that a virtual growth can also be negative by e.g. issueing a
free() or detaching a shared memory segment. For a process
which started during the last interval, the virtual growth
reflects the total virtual size of the process at that moment.
If a process has finished during the last interval, no value
is shown since virtual memory occupation is not part of the
standard process accounting record. However when the kernel
patch `acct’ is installed, this value will be shown.

VSIZE The total virtual memory usage consumed by this process (or
user).
If a process has finished during the last interval, no value
is shown since virtual memory occupation is not part of the
standard process accounting record. However when the kernel
patch `acct’ is installed, this value will be shown.

VSTEXT The virtual memory size used by the shared text of this
process.

WRDSK When the kernel maintains standard io statistics (>= 2.6.20):
The write data transfer issued physically on disk (so writing
to the disk cache is not accounted for). This counter is
maintained for the application process that writes its data to
the cache (assuming that this data is physically transferred
to disk later on). Notice that disk I/O needed for swapping is
not taken into account.

When the kernel patch `cnt’ is installed:
The number of write accesses issued physically on disk (so
writing to the disk cache is not accounted for). Usually
application processes just transfer their data to the cache,
while the physical write accesses are done later on by kernel
daemons like pdflush. Note that the number read- and write
accesses are not separately maintained in the standard process
accounting record. This means that only one value is given
for read’s and write’s in case a process has finished during
the last interval. However when the kernel patch `acct’ is
installed, these values will be shown separately.

WCANCL When the kernel patch `cnt’ is not installed, but the kernel
maintains standard io statistics (>= 2.6.20):
The write data transfer previously accounted for this process
or another process that has been cancelled. Suppose that a
process writes new data to a file and that data is removed
again before the cache buffers have been flushed to disk.
Then the original process shows the written data as WRDSK,
while the process that removes/truncates the file shows the
unflushed removed data as WCANCL.

PARSEABLE OUTPUT
With the flag -P followed by a list of one or more labels (comma-sepa‐
rated), parseable output is produced for each sample. The labels that
can be specified for system-level statistics correspond to the labels
(first verb of each line) that can be found in the interactive output:
“CPU”, “cpu” “CPL” “MEM”, “SWP”, “PAG”, “LVM”, “MDD”, “DSK” and “NET”.
For process-level statistics special labels are introduced: “PRG” (gen‐
eral), “PRC” (cpu), “PRM” (memory), “PRD” (disk, only if the kernel-
patch has been installed) and “PRN” (network, only if the kernel-patch
has been installed).
With the label “ALL”, all system- and process-level statistics are
shown.

For every interval all requested lines are shown whereafter atop shows
a line just containing the label “SEP” as a separator before the lines
for the next sample are generated.
When a sample contains the values since boot, atop shows a line just
containing the label “RESET” before the lines for this sample are gen‐
erated.

The first part of each output-line consists of the following six
fields: label (the name of the label), host (the name of this machine),
epoch (the time of this interval as number of seconds since 1-1-1970),
date (date of this interval in format YYYY/MM/DD), time (time of this
interval in format HH:MM:SS), and interval (number of seconds elapsed
for this interval).

The subsequent fields of each output-line depend on the label:

CPU Subsequent fields: total number of clock-ticks per second for
this machine, number of processors, consumption for all CPU’s
in system mode (clock-ticks), consumption for all CPU’s in
user mode (clock-ticks), consumption for all CPU’s in user
mode for niced processes (clock-ticks), consumption for all
CPU’s in idle mode (clock-ticks), consumption for all CPU’s in
wait mode (clock-ticks), consumption for all CPU’s in irq mode
(clock-ticks), consumption for all CPU’s in softirq mode
(clock-ticks), consumption for all CPU’s in steal mode (clock-
ticks), and consumption for all CPU’s in guest mode (clock-
ticks).

cpu Subsequent fields: total number of clock-ticks per second for
this machine, processor-number, consumption for this CPU in
system mode (clock-ticks), consumption for this CPU in user
mode (clock-ticks), consumption for this CPU in user mode for
niced processes (clock-ticks), consumption for this CPU in
idle mode (clock-ticks), consumption for this CPU in wait mode
(clock-ticks), consumption for this CPU in irq mode (clock-
ticks), consumption for this CPU in softirq mode (clock-
ticks), consumption for this CPU in steal mode (clock-ticks),
and consumption for this CPU in guest mode (clock-ticks).

CPL Subsequent fields: number of processors, load average for last
minute, load average for last five minutes, load average for
last fifteen minutes, number of context-switches, and number
of device interrupts.

MEM Subsequent fields: page size for this machine (in bytes), size
of physical memory (pages), size of free memory (pages), size
of page cache (pages), size of buffer cache (pages), size of
slab (pages), and number of dirty pages in cache.

SWP Subsequent fields: page size for this machine (in bytes), size
of swap (pages), size of free swap (pages), 0 (future use),
size of committed space (pages), and limit for committed space
(pages).

PAG Subsequent fields: page size for this machine (in bytes), num‐
ber of page scans, number of allocstalls, 0 (future use), num‐
ber of swapins, and number of swapouts.

LVM/MDD/DSK
For every logical volume/multiple device/hard disk one line is
shown.
Subsequent fields: name, number of milliseconds spent for I/O,
number of reads issued, number of sectors transferred for
reads, number of writes issued, and number of sectors trans‐
ferred for write.

NET First one line is produced for the upper layers of the TCP/IP
stack.
Subsequent fields: the verb “upper”, number of packets
received by TCP, number of packets transmitted by TCP, number
of packets received by UDP, number of packets transmitted by
UDP, number of packets received by IP, number of packets
transmitted by IP, number of packets delivered to higher lay‐
ers by IP, and number of packets forwarded by IP.

Next one line is shown for every interface.
Subsequent fields: name of the interface, number of packets
received by the interface, number of bytes received by the
interface, number of packets transmitted by the interface,
number of bytes transmitted by the interface, interface speed,
and duplex mode (0=half, 1=full).

PRG For every process one line is shown.
Subsequent fields: PID, name (between brackets), state, real
uid, real gid, TGID (same as PID), total number of threads,
exit code, start time (epoch), full command line (between
brackets), PPID, number of threads in state ‘running’ (R),
number of threads in state ‘interruptible sleeping’ (S), num‐
ber of threads in state ‘uninterruptible sleeping’ (D), effec‐
tive uid, effective gid, saved uid, saved gid, filesystem uid,
filesystem gid, and elapsed time (hertz).

PRC For every process one line is shown.
Subsequent fields: PID, name (between brackets), state, total
number of clock-ticks per second for this machine, CPU-con‐
sumption in user mode (clockticks), CPU-consumption in system
mode (clockticks), nice value, priority, realtime priority,
scheduling policy, current CPU, and sleep average.

PRM For every process one line is shown.
Subsequent fields: PID, name (between brackets), state, page
size for this machine (in bytes), virtual memory size
(Kbytes), resident memory size (Kbytes), shared text memory
size (Kbytes), virtual memory growth (Kbytes), resident memory
growth (Kbytes), number of minor page faults, and number of
major page faults.

PRD For every process one line is shown.
Subsequent fields: PID, name (between brackets), state, ker‐
nel-patch installed (‘y’ or ‘n’), standard io statistics used
(‘y’ or ‘n’), number of reads on disk, cumulative number of
sectors read, number of writes on disk, cumulative number of
sectors written, and cancelled number of written sectors.
If the kernel patch is not installed and the standard I/O sta‐
tistics (>= 2.6.20) are not used, the disk I/O counters per
process are not relevant. When the kernel patch is installed,
the counter ‘cancelled number of written sectors’ is not rele‐
vant. When only the standard io statistics are used, the
counters ‘number of reads on disk’ and ‘number of writes on
disk’ are not relevant.

PRN For every process one line is shown.
Subsequent fields: PID, name (between brackets), state, ker‐
nel-patch installed (‘y’ or ‘n’), number of TCP-packets trans‐
mitted, cumulative size of TCP-packets transmitted, number of
TCP-packets received, cumulative size of TCP-packets received,
number of UDP-packets transmitted, cumulative size of UDP-
packets transmitted, number of UDP-packets received, cumula‐
tive size of UDP-packets transmitted, number of raw packets
transmitted, and number of raw packets received.
If the kernel patch is not installed, the network I/O counters
per process are not relevant.

EXAMPLES
To monitor the current system load interactively with an interval of 5
seconds:

atop 5

To monitor the system load and write it to a file (in plain ASCII) with
an interval of one minute during half an hour with active processes
sorted on memory consumption:

atop -M 60 30 > /log/atop.mem

Store information about the system- and process activity in binary com‐
pressed form to a file with an interval of ten minutes during an hour:

atop -w /tmp/atop.raw 600 6

View the contents of this file interactively:

atop -r /tmp/atop.raw

View the processor- and disk-utilization of this file in parseable for‐
mat:

atop -PCPU,DSK -r /tmp/atop.raw

View the contents of today’s standard logfile interactively:

atop -r

View the contents of the standard logfile of the day before yesterday
interactively:

atop -r yy

View the contents of the standard logfile of 2010, January 7 from 02:00
PM onwards interactively:

atop -r 20100107 -b 14:00

FILES
/tmp/atop.d/atop.acct
File in which the kernel writes the accounting records if the
standard accounting to the file /var/log/pacct or
/var/account/pacct is not used.

/etc/atoprc
Configuration file containing system-wide default values. See
related man-page.

~/.atoprc
Configuration file containing personal default values. See
related man-page.

/var/log/atop/atop_YYYYMMDD
Raw file, where YYYYMMDD are digits representing the current date.
This name is used by the script atop.daily as default name for the
output file, and by atop as default name for the input file when
using the -r flag.
All binary system- and process-level data in this file has been
stored in compressed format.

SEE ALSO

atopsar, atoprc(5), logrotate(8)
http://www.atoptool.nl

AUTHOR

Gerlof Langeveld (gerlof.langeveld@atoptool.nl)
JC van Winkel (jc@ATComputing.nl)

AT Computing April 2010 ATOP(1)

Ils en parlent aussi

How to Install ” to Monitor Logging Activity of Linux System …
Atop – monitor system resources in Linux – Linux Howto’s Guide