virt-top - Online in the Cloud

PROGRAM:

NAME

virt-top - 'top'-like utility for virtualization stats

SUMMARY

virt-top [-options]

DESCRIPTION

virt-top is a top(1)-like utility for showing stats of virtualized domains. Many keys and
command line options are the same as for ordinary top.

It uses libvirt so it is capable of showing stats across a variety of different
virtualization systems.

OPTIONS

-1 Display physical CPUs by default (instead of domains). When virt-top is running, use
the 1 key to toggle between physical CPUs and domains display.

-2 Display network interfaces by default (instead of domains). When virt-top is running,
use the 2 key to toggle between network interfaces and domains display.

-3 Display block devices (virtual disks) by default (instead of domains). When virt-top
is running, use the 3 key to toggle between block devices and domains display.

-b Batch mode. In this mode keypresses are ignored.

-c uri or --connect uri
Connect to the libvirt URI given.

To connect to QEMU/KVM you would normally do -c qemu:///system

To connect to Xen on the same host, do -c xen:///

To connect to libvirtd on a remote machine you would normally do -c qemu://host/system

If this option is not given then virt-top connects by default to whatever is the
default hypervisor for libvirt, although this can be overridden by setting environment
variables.

See the libvirt documentation at <http://libvirt.org/uri.html> for further
information.

-d delay
Set the delay between screen updates in seconds. The default is 3.0 seconds. You can
change this while virt-top is running by pressing either s or d key.

-n iterations
Set the number of iterations to run. The default is to run continuously.

-o sort
Set the sort order to one of: cpu (sort by %CPU used), mem (sort by total memory),
time (sort by total time), id (sort by domain ID), name (sort by domain name), netrx
(sort by network received bytes), nettx (sort by network transmitted bytes), blockrdrq
(sort by block device [disk] read requests), blockwrrq (sort by block device [disk]
write requests).

While virt-top is running you can change the sort order using keys P (cpu), M
(memory), T (total time), N (domain ID), F (interactively select the sort field).

-s Secure mode. Currently this does nothing.

--hist-cpu secs
Set the time in seconds between updates of the historical %CPU at the top right of the
display.

--csv file.csv
Write the statistics to file file.csv. First a header is written showing the
statistics being recorded in each column, then one line is written for each screen
update. The CSV file can be loaded directly by most spreadsheet programs.

Currently the statistics which this records vary between releases of virt-top (but the
column headers will stay the same, so you can use those to process the CSV file).

Not every version of virt-top supports CSV output - it depends how the program was
compiled (see README file in the source distribution for details).

To save space you can compress your CSV files (if your shell supports this feature,
eg. bash):

virt-top --csv >(gzip -9 > output.csv.gz)

You can use a similar trick to split the CSV file up. In this example the CSV file is
split every 1000 lines into files called output.csv.00, output.csv.01 etc.

virt-top --csv >(split -d -l 1000 - output.csv.)

--no-csv-cpu
Disable domain CPU stats in CSV output.

--no-csv-mem
Disable domain memory stats in CSV output.

--no-csv-block
Disable domain block device stats in CSV output.

--no-csv-net
Disable domain network interface stats in CSV output.

--debug filename
Send debug and error messages to filename. To send error messages to syslog you can
do:

virt-top --debug >(logger -t virt-top)

See also REPORTING BUGS below.

--init-file filename
Read filename as the init file instead of the default which is $HOME/.virt-toprc. See
also INIT FILE below.

--no-init-file
Do not read any init file.

--script
Script mode. There will be no user interface. This is most useful when used together
with the --csv and -n options.

--stream
Stream mode. All output is sent to stdout. This can be used from shell scripts etc.
There is no user interface.

--block-in-bytes
Show I/O statistics in Bytes. Default is shown in the number of Requests.

--end-time time
The program will exit at the time given.

The time may be given in one of the following formats:

YYYY-MM-DD HH:MM:SS
End time is the date and time given.

HH:MM:SS
End time is the time given, today.

+HH:MM:SS
End time is HH hours, MM minutes, SS seconds in the future (counted from the
moment that program starts).

+secs
End time is secs seconds in the future.

For example to run the program for 3 minutes you could do:

virt-top --end-time +00:03:00

or:

virt-top --end-time +180

Not every version of virt-top supports this option - it depends how the program was
compiled (see README file in the source distribution for details).

--help
Display usage summary.

--version
Display version number and exit.

KEYS

Note that keys are case sensitive. For example use upper-case P (shift P) to sort by
%CPU. ^ before a key means a Ctrl key, so ^L is Ctrl L.

space or ^L
Updates the display.

q Quits the program.

h Displays help.

s or d
Change the delay between screen updates.

B Toggle Block I/O statistics so they are shown in either bytes or requests.

0 (number 0)
Show the normal list of domains display.

1 (number 1)
Toggle into showing physical CPUs. If pressed again toggles back to showing domains
(the normal display).

2 Toggle into showing network interfaces. If pressed again toggles back to showing
domains.

3 Toggle into showing block devices (virtual disks). If pressed again toggles back to
showing domains.

P Sort by %CPU.

M Sort by total memory. Note that this shows the total memory allocated to the guest,
not the memory being used.

T Sort by total time.

N Sort by domain ID.

F Select the sort field interactively (there are other sort fields you can choose using
this key).

W This creates or overwrites the init file with the current settings.

This key is disabled if --no-init-file was specified on the command line or if
overwrite-init-file false is given in the init file.

INIT FILE

When virt-top starts up, it reads initial settings from the file .virt-toprc in the user's
home directory.

The name of this file may be overridden using the --init-file filename command line option
or may be disabled entirely using --no-init-file.

The init file has a simple format. Blank lines and comments beginning with # are ignored.
Everything else is a set of key value pairs, described below.

display task|pcpu|block|net
Sets the major display mode to one of task (tasks, the default), pcpu (physical CPUs),
block (block devices), or net (network interfaces).

delay secs
Sets the delay between display updates in seconds.

hist-cpu secs
Sets the historical CPU delay in seconds.

iterations n
Sets the number of iterations to run before we exit. Setting this to -1 means to run
continuously.

sort cpu|mem|time|id|name|...
Sets the sort order. The option names are the same as for the command line -o option.

connect uri
Sets the default connection URI.

debug filename
Sets the default filename to use for debug and error messages.

csv filename
Enables CSV output to the named file.

csv-cpu true|false
Enable or disable domain CPU stats in CSV output.

csv-mem true|false
Enable or disable domain memory stats in CSV output.

csv-block true|false
Enable or disable domain block device stats in CSV output.

csv-net true|false
Enable or disable domain network interface stats in CSV output.

batch true|false
Sets batch mode.

secure true|false
Sets secure mode.

script true|false
Sets script mode.

stream true|false
Sets stream mode.

block-in-bytes true|false
Show block device statistics in bytes.

end-time time
Set the time at which the program exits. See above for the time formats supported.

overwrite-init-file false
If set to false then the W key will not overwrite the init file.

Note that in the current implementation, options specified in the init file override
options specified on the command line. This is a bug and this behaviour may change in the
future.

NOTES

Block I/O statistics
This I/O value is the amount of I/O since the previous iteration of virt-top. To calculate
speed of I/O, you should divide the number by delay secs.

NETWORK RX BYTES AND PACKETS
Libvirt/virt-top has no way to know that a packet transmitted to a guest was received (eg.
if the guest is not listening). In the network RX stats, virt-top reports the packets
transmitted to the guest, on the basis that the guest might receive them.

In particular this includes broadcast packets. Because of the way that Linux bridges
work, if the guest is connected to a bridge, it will probably see a steady "background
noise" of RX packets even when the network interface is idle or down. These are caused by
STP packets generated by the bridge.

DEBUGGING LIBVIRT ISSUES
virt-top tries to turn libvirt errors into informative messages. However if libvirt
initialization fails then this is not possible. Instead you will get an obscure error
like:

libvir: error : Unknown failure
Fatal error: exception Libvirt.Virterror(...)

To see the cause of libvirt errors in more detail, enable libvirt debugging by setting
this environment variable:

export LIBVIRT_DEBUG=1

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