NAME¶
pg_top - display and update information about the top cpu PostgreSQL processes
SYNOPSIS¶
pg_top [
-ITWbcinqu ] [
-dDBNAME ] [
-hHOSTNAME ] [
-ofield ] [
-pPORT ]
[
-stime ] [
-UUSER ] [
-xcount ] [
-zusername ] [
number ]
DESCRIPTION¶
pg_top displays the top processes on the system and periodically updates
this information. Raw cpu percentage is used to rank the processes. If
number is given, then the top
number processes will be displayed
instead of the default.
pg_top makes a distinction between terminals that support advanced
capabilities and those that do not. This distinction affects the choice of
defaults for certain options. In the remainder of this document, an
"intelligent" terminal is one that supports cursor addressing, clear
screen, and clear to end of line. Conversely, a "dumb" terminal is
one that does not support such features. If the output of
pg_top is
redirected to a file, it acts as if it were being run on a dumb terminal.
OPTIONS¶
- -C
- Turn off the use of color in the display.
- -I
- Do not display idle processes. By default, pg_top displays
both active and idle processes.
- -T
- List all available color tags and the current set of tests
used for color highlighting, then exit.
- -W
- Forces pg_top to prompt for a password before connecting to
a database.
- -b
- Use "batch" mode. In this mode, all input from
the terminal is ignored. Interrupt characters (such as ^C and ^\) still
have an effect. This is the default on a dumb terminal, or when the output
is not a terminal.
- -c
- Show the command name for each process. Default is to show
the full command line. This option is not supported on all platforms.
- -i
- Use "interactive" mode. In this mode, any input
is immediately read for processing. See the section on "Interactive
Mode" for an explanation of which keys perform what functions. After
the command is processed, the screen will immediately be updated, even if
the command was not understood. This mode is the default when standard
output is an intelligent terminal.
- -n
- Use "non-interactive" mode. This is indentical to
"batch" mode.
- -q
- Renice pg_top to -20 so that it will run faster.
This can be used when the system is being very sluggish to improve the
possibility of discovering the problem. This option can only be used by
root.
- -u
- Do not take the time to map uid numbers to usernames.
Normally, pg_top will read as much of the file
"/etc/passwd" as is necessary to map all the user id numbers it
encounters into login names. This option disables all that, while possibly
decreasing execution time. The uid numbers are displayed instead of the
names.
- -v
- Write version number information to stderr then exit
immediately. No other processing takes place when this option is used. To
see current revision information while pg_top is running, use the help
command "?".
- -stime
- Set the delay between screen updates to time
seconds. The default delay between updates is 5 seconds.
- -ofield
- Sort the process display area on the specified field. The
field name is the name of the column as seen in the output, but in lower
case. Likely values are "cpu", "size",
"res", and "time", but may vary on different operating
systems. Note that not all operating systems support this option.
- -xcount
- Show only count displays, then exit. A display is
considered to be one update of the screen. This option allows the user to
select the number of displays he wants to see before pg_top
automatically exits. For intelligent terminals, no upper limit is set. The
default is 1 for dumb terminals.
- -zusername
- Show only those processes owned by username. This
option currently only accepts usernames and will not understand uid
numbers.
Both
count and
number fields can be specified as
"infinite", indicating that they can stretch as far as possible.
This is accomplished by using any proper prefix of the keywords
"infinity", "maximum", or "all". The default for
count on an intelligent terminal is, in fact,
infinity.
The environment variable
PG_TOP is examined for options before the
command line is scanned. This enables a user to set his or her own defaults.
The number of processes to display can also be specified in the environment
variable
PG_TOP. The options
-C,
-I, and
-u are
actually toggles. A second specification of any of these options will negate
the first. Thus a user who has the environment variable
PG_TOP set to
"-I" may use the command "top -I" to see idle processes.
INTERACTIVE MODE¶
When
pg_top is running in "interactive mode", it reads commands
from the terminal and acts upon them accordingly. In this mode, the terminal
is put in "CBREAK", so that a character will be processed as soon as
it is typed. Almost always, a key will be pressed when
pg_top is
between displays; that is, while it is waiting for
time seconds to
elapse. If this is the case, the command will be processed and the display
will be updated immediately thereafter (reflecting any changes that the
command may have specified). This happens even if the command was incorrect.
If a key is pressed while
pg_top is in the middle of updating the
display, it will finish the update and then process the command. Some commands
require additional information, and the user will be prompted accordingly.
While typing this information in, the user's erase and kill keys (as set up by
the command
stty) are recognized, and a newline terminates the input.
These commands are currently recognized (^L refers to control-L):
- ^L
- Redraw the screen.
- A
- Display the actual query plan (EXPLAIN ANALYZE) of the
currently running SQL statement by re-running the SQL statement (prompt
for process id.)
- C
- Toggle the use of color in the display.
- c
- Toggle the display of the full command line.
- d
- Change the number of displays to show (prompt for new
number). Remember that the next display counts as one, so typing d1
will make pg_top show one final display and then immediately
exit.
- h or ?
- Display a summary of the commands (help screen). Version
information is included in this display.
- E
- Display re-determined execution plan (EXPLAIN) of the SQL
statement by a backend process (prompt for process id.)
- e
- Display a list of system errors (if any) generated by the
last kill or renice command.
- i
- (or I) Toggle the display of idle processes.
- k
- Send a signal ("kill" by default) to a list of
processes. This acts similarly to the command kill(1)).
- L
- Display the currently held locks by a backend process
(prompt for process id.)
- M
- Order by memory utilization.
- N
- Sort by process id.
- n or #
- Change the number of processes to display (prompt for new
number).
- o
- Change the order in which the display is sorted. This
command is not available on all systems. The sort key names when viewing
processes vary fron system to system but usually include: "cpu",
"res", "size", "time". The default is cpu.
When viewing user table statistics: "seq_scan",
"seq_tup_read", "idx_scan", "idx_tup_fetch",
"n_tup_ins", "n_tup_upd", "n_tup_del". The
default is seq_scan. When viewing user index statistics:
"idx_scan", "idx_tup_fetch", "idx_tup_read".
The default is idx_scan.
- P
- Sort by processor utilization.
- Q
- Display the currently running query of a backend process
(prompt for process id.)
- q
- Quit pg_top.
- R
- Display user table statistics.
- r
- Change the priority (the "nice") of a list of
processes. This acts similarly to the command renice(8)).
- s
- Change the number of seconds to delay between displays
(prompt for new number).
- T
- Order by time.
- t
- Toggle between cumulative or differential statistics when
viewing user table or user index statistics.
- u
- Display only processes owned by a specific username (prompt
for username). If the username specified is simply "+", then
processes belonging to all users will be displayed.
- X
- Display user index statistics.
THE DISPLAY¶
The actual display varies depending on the specific variant of Unix that the
machine is running. This description may not exactly match what is seen by
pg_top running on this particular machine. Differences are listed at the end
of this manual entry.
The top few lines of the display show general information about the state of the
system, including the last process id assigned to a process (on most systems),
the three load averages, the current time, the number of existing processes,
the number of processes in each state (sleeping, running, starting, zombies,
and stopped), and a percentage of time spent in each of the processor states
(user, nice, system, and idle). It also includes information about physical
and virtual memory allocation.
The remainder of the screen displays information about individual processes.
This display is similar in spirit to
ps(1) but it is not exactly the
same. The columns displayed by pg_top will differ slightly between operating
systems. Generally, the following fields are displayed:
- PID
- The process id.
- USERNAME
- Username of the process's owner (if -u is specified,
a UID column will be substituted for USERNAME).
- PRI
- Current priority of the process.
- NICE
- Nice amount in the range -20 to 20, as established by the
use of the command nice.
- SIZE
- Total size of the process (text, data, and stack) given in
kilobytes.
- RES
- Resident memory: current amount of process memory that
resides in physical memory, given in kilobytes.
- STATE
- Current state (typically one of "sleep",
"run", "idl", "zomb", or
"stop").
- TIME
- Number of system and user cpu seconds that the process has
used.
- CPU
- Percentage of available cpu time used by this process.
- COMMAND
- Name of the command that the process is currently
running.
COLOR¶
pg_top supports the use of ANSI color in its output. By default, color is
available but not used. The environment variable
TOPCOLORS specifies
colors to use and conditions for which they should be used. At the present
time, only numbers in the summay display area can be colored. In a future
version it will be possible to highlight numbers in the process display area
as well. The environment variable is the only way to specify color: there is
no equivalent command line option. Note that the environment variable
TOPCOLOURS is also understood. The British spelling takes precedence.
The use of color only works on terminals that understand and process ANSI
color escape sequences.
The environment variable is a sequence of color specifications, separated by
colons. Each specification takes the form tag=min,max#code where
tag is
the name of the value to check,
min and
max specify a range for
the value, and
code is an ANSI color code. Multiple color codes can be
listed and separated with semi-colons. A missing
min implies the lowest
possible value (usually 0) and a missing
max implies infinity. The
comma must always be present. When specifying numbers for load averages, they
should be multiplied by 100. For example, the specification
1min=500,1000#31 indicates that a 1 minute load average between 5 and
10 should be displayed in red. Color attributes can be combined. For example,
the specification
5min=1000,#37;41 indicates that a 5 minute load
average higher than 10 should be displayed with white characters on a red
background. A special tag named
header is used to control the color of
the header for process display. It should be specified with no lower and upper
limits, specifically
header=,# followed by the ANSI color code.
You can see a list of color codes recognized by this installation of pg_top with
the
-T option. This will also show the current set of tests used for
color highligting, as specified in the environment.
AUTHOR¶
William LeFebvre Mark Wong
ENVIRONMENT¶
PG_TOP user-configurable defaults for options. PG_TOPCOLORS color specification
BUGS¶
As with
ps(1), things can change while
pg_top is collecting
information for an update. The picture it gives is only a close approximation
to reality.
SEE ALSO¶
kill(1),
ps(1),
stty(1),
mem(4),
renice(8)
LINUX NOTES¶
The Linux port was written by Richard Henderson <rth@tamu.edu>. The CPU%
calculation was brazenly stolen from the Solaris 2 port and should be
attributed to one of the many names listed in its man page.
The order support was stolen from SUNOS 5 port by Alexey Klimkin
<kad@klon.tme.mcst.ru>
Made to work under 2.4 by William LeFebvre.