Frequently Asked Questions and their Answers
1. What is pg_top?
pg_top is 'top' for PostgreSQL. It is derived from Unix Top. Similar to top,
pg_top allows you to monitor PostgreSQL processes. It also allows you to:
* View currently running SQL statement of a process.
* View query plan of a currently running SELECT statement.
* View locks held by a process.
* View user table statistics.
* View user index statistics.
2. Where do I get the latest version of pg_top?
If you have mercurial, you can download the latest version from SourceForge:
hg clone http://ptop.sourceforge.net/cgi-bin/hgwebdir.cgi/pg_top
3. Is there a web page for pg_top?
4. Is there a mailing list or on-line bulletin board for pg_top?
Subscribe or browse the archives of ptop-hackers at:
5. What about Y2K/Year 2038 compliance?
A full statement concerning top and the year 2000 can be found in the file
"Y2K" included with the distribution.
6. Will there be another major release of pg_top? Will there be a pg_top
We hope so! Depends on how much fun we have. :)
7. Is top under CVS control? Can I access the sources via SourceForge
CVS or Subversion?
I maintain top using mercurial, not CVS. See FAQ #2.
8. We just upgraded our operating system to a new version and pg_top broke.
What should we do?
Recompile it. pg_top is very sensitive to changes in internal kernel
data structures. It is not uncommon for a new version of the
operating system to include changes to kernel data structures.
10. I just finished compiling top and it works fine for root, but when I
try to run it as a regular user it either complains about files it
can't open or it doesn't display all the information it should. Did I
do something wrong?
Well, you're just not done. On many operating systems today, access
to many of the kernel memory devices and other system files is
restricted to either root or a particular group. The configure script
figures this out (usually) and makes sure that the "install" rule in
the Makefile will install top so that anyone can run it successfully.
However, you have to *install* it first. Do this with the command
11. pg_top is (not) displaying idle processes and I don't (do) want it to.
This default has only changed about a dozen times, and I finally got
tired of people whining about it. Go read the manual page for the
current version and pay special attention to the description of the
"PG_TOP" environment variable.
12. We have so much memory in our machine that the memory status display
(the fourth line) ends up being longer than 80 characters. This
completely messes up top's output. Is there a patch?
Most modules have been changed to use new memory formatting functions
which will display large values in terms of megabytes instead of
kilobytes. This should fix all occurences of this problem. Also note
that newer versions of top can use columns beyond 79, and understand
window resizes. So you can always make your window wider.
13. I tried to compile top with gcc and it doesn't work. I get
compilation errors in the include files, or I get an executable that
dumps core, or top displays incorrect numbers in some of the
displays. What's wrong?
Gnu CC likes very much to use its own include files. Not being a gcc
expert, I can't explain why it does this. But I can tell you that if
you upgrade your operating system (say from Solaris 2.6 to Solaris
2.7) after installing gcc, then the include files that gcc uses will
be incorrect, especially those found in the "sys" directory. Your
choices are: (1) rebuild and reinstall the "standard" include files
for gcc (look for scripts in the distribution called "fixincludes"
and "fixinc.svr4"), (2) compile machine.c with
"CFLAGS=-I/usr/include" then make the rest of the object files
normally, or (3) use a different compiler.
14. The cpu state percentages are all wrong, indicating that my machine
is using 95% system time when it is clearly idle. What's wrong?
This can happen if you compiled with gcc using the wrong include
files. See the previous question.
15. I tried to configure top on my Mac OSX system and I got an error
claiming "macosx not supported". What up?
Since I don't have full time root access to a Mac OSX system I cannot
provide effective support for the platform. MacOSX uses Mach, and it
is very difficult to extract accurate system and process information
from the system. It takes a lot of trial and error, along with root
access. I have included the most up-to-date version of the macosx
module in the distribution, but I do not claim that it works. If you
want to try to use it, you can configure with "./configure
16. I tried compiling top under SunOS version 4.1.x and it got compile
time errors or run time errors. Is there a patch?
If you try compiling top in a "System V environment" under SunOS
(that is, /usr/5bin is before /usr/bin on your path) then the
compilation may fail. This is mostly due to the fact that top thinks
its being compiled on a System V machine when it really isn't. The
only solution is to put /usr/bin and /usr/ucb before /usr/5bin on
your path and try again.
NOTE: the most common source of problems with top under Solaris is
the result of compiling it with the wrong front end. Make sure that
/usr/ucb is not on your path before attempting to compile top under
17. Is there somewhere I can get a pre-compiled package?
Yes. Although I don't provide pre-compiled binaries, you can get a
Sun-style package from www.sunfreeware.com.
18. Under Solaris 2, when I type "make", the system says "language
optional software package not installed." What's going on?
You tried to compile with /usr/ucb/cc. Make sure /usr/ucb is not on
your path. Furthermore, you do not have a Sun compiler installed on
your system. You need a compiler to make top. Either Sun's C compiler
or the Gnu C compiler will work fine.
19. Under Solaris 2, when I run top as root it only shows root processes,
or it only shows processes with a PID less than 1000. It refuses to
show anything else. What do I do?
You probably compiled it with /usr/ucb/cc instead of the real C
compiler. /usr/ucb/cc is a cc front end that compiles programs in BSD
source-level compatability mode. You do not want that. Make sure that
/usr/ucb is not on your path and try compiling top again.
20. Under Solaris 2, I compiled top using what I am sure is the correct
compiler but when I try to run it it complains about missing dynamic
libraries. What is wrong?
Check to see if you have LD_LIBRARY_PATH defined in your shell. If
you do, make sure that /usr/ucblib is not on the path anywhere. Then
try compiling top again.
21. Under Solaris 2, when I try to run top it complains that it can't
open the library "libucb.so.1". So I changed the LIBS line in
m_sunos5.c to include -R/usr/ucblib to make sure that the dynamic
linker will look there when top runs. I figured this was just an
oversight. Was I right?
No, you were not right. As distributed, top requires no alterations
for successful compilation and operations under any release of
Solaris 2. You probably compiled top with /usr/ucb/cc instead of the
real C compiler. See FAQ 22 for more details.
22. On my 64-bit system some processes show up with incorrect information
(such as zero memory).
If you are running a 64-bit system, then you will want to make a
64-bit top binary. pg_top's configure script attempts to detect 64-bit
systems, and will adjust the compilation options accordingly. If you
configure and make a binary on a 32-bit system it will still run on a
64-bit system, but may not produce the correct results. The same will
happen if you configure your distribution on a 32-bit system then
compile with that configuration on a 64-bit system. You must
configure and compile on the same system.
23. Can I install both 32-bit and 64-bit binaries on a central file
server and have machines which mount it automatically use the correct
Yes. First, compile a 32-bit version and name it top32. Then compile
a 64-bit version (see FAQ #22) and name it top64. Make sure each
binary has the correct ownership and mode. Choose your bin directory
(we will refer to that as $BIN). In $BIN make sure there are
subdirectories named "sparcv7" and "sparcv9". If they don't exist
then create them. Copy "top32" to "$BIN/sparcv7/top" and "top64" to
"$BIN/sparcv9/top". Finally copy (do not link) the binary
/usr/lib/isaexec to "$BIN/top". When a user runs "top" she will
actually be running a copy of isaexec. This tool will automatically
determine the kernel type and run the top "binary" out of the correct
24. This version of top show less available swap space than previous
versions. Why does it no longer match the output of the swap summary
produced with "swap -s"?
Starting with version 3.6 of top, the amount of swap space reported
by top has been changed to reflect only disk-based swap space. The
swap summary produced with "swap -s" also include memory-based swap
space. This changed was mae for several reasons. It makes the display
under Solaris more like those of other operating systems. The display
is more what users expect (except those used to previous versions of
top). Most importantly, "swap -s" gets its data via an undocumented
system interface. Now that top no longer displays that data it can
use publically documented and maintained system interfaces to
retrieve its data.
25. When I run top on my SVR4-derived operating system, it displays all
the system information at the top but does not display any process
information (or only displays process information for my own
processes). Yet when I run it as root, everything works fine. What's
Your system probably uses the pseudo file system "/proc", which is by
default only accessible by root. pg_top needs to be installed setuid
root on such systems if it is going to function correctly for normal
26. The memory display doesn't work right. Why?
This is a known bug with the svr42 module. The problem has been
traced down to a potential bug in the "mem" driver. The author of the
svr42 module is working on a fix.
27. I'm still stuck. To whom do I report problems with top?
The most common problems are caused by top's sensitivity to internal
kernel data structures. So make sure that you are using the right
include files, and make sure that you test out top on the same
machine where you compiled it. Sun's BSD Source Compatability Mode is
also a common culprit. Make sure you aren't using either /usr/ucb/cc
or any of the libraries in /usr/ucblib. Finally, make sure you are
using the correct module. If there does not appear to be one
appropriate for your computer, then top probably will not work on
If after reading all of this file and checking everything you can you
are still stuck, then please use SourceForge to submit a support
request or a bug. pg_top is supported by the SourceForge project named
"unixtop". On SourceForge you will find defect tracking, a mailing
list, and on-line forums. You can also contact the author through