Обсуждение: postgres memory management
Hi all, I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat Linux 7. I'm sending lots of insert statements to the postgresql server from another machine via JDBC. During that process postgresql continues to take up more and more memory and seemingly never returns it to the system. Oddly if I watch the postmaster and it's sub processes in ktop, I can't see which process takes up this memory. ktop shows that the postgresql related processes have a constant memory usage but the overall memory usage always increases as long as I continue to send insert statements. When the database connection is closed, no memory is reclaimed, the overall memory usage stays the same. And when I close down all postgresql processes including postmaster, it's the same. I'm rather new to Linux and postgresql so I'm not sure if I should call this a memory leak :-) Has anybody experienced a similar thing? thanks, Alexander Jerusalemvknn
Thank you for your answer Mark! Now I have updated glibc to the latest version (2.2) and it's still the same. I don't have the time to change to a different Linux version just to try if that solves the problem. What else could I do? thanks, Alexander Jerusalem ajeru@gmx.net At 15:49 21.01.01, you wrote: >First Things First. I would not use a .0 version of Redhat for anything. The >7.0 version is very buggy. Switch to Redhat 6.2 or another distribution like >Slackware 7.2. > > > Hi all, > > > > I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat > > Linux 7. I'm sending lots of insert statements to the postgresql server > > from another machine via JDBC. During that process postgresql continues to > > take up more and more memory and seemingly never returns it to the system. > > Oddly if I watch the postmaster and it's sub processes in ktop, I can't >see > > which process takes up this memory. ktop shows that the postgresql related > > processes have a constant memory usage but the overall memory usage always > > increases as long as I continue to send insert statements. > > > > When the database connection is closed, no memory is reclaimed, the >overall > > memory usage stays the same. And when I close down all postgresql >processes > > including postmaster, it's the same. > > I'm rather new to Linux and postgresql so I'm not sure if I should call > > this a memory leak :-) > > Has anybody experienced a similar thing? > > > > thanks, > > Alexander Jerusalemvknn > > > >
On Sun, Jan 21, 2001 at 13:18:54 +0100, Alexander Jerusalem wrote:
> During that process postgresql continues to take up more and more memory
> and seemingly never returns it to the system. Oddly if I watch the
> postmaster and it's sub processes in ktop, I can't see which process takes
> up this memory. ktop shows that the postgresql related processes have a
> constant memory usage but the overall memory usage always increases as
> long as I continue to send insert statements.
>
> When the database connection is closed, no memory is reclaimed, the
> overall memory usage stays the same. And when I close down all postgresql
> processes including postmaster, it's the same.
Linux uses memory that wouldn't otherwise be used as buffer/cache space
(watch the "cached" entry in "top"). This is nothing to worry about.
HTH,
Ray
--
USDoJ/Judge Jackson: "Microsoft has performed an illegal operation and will
be shut down."
James Turinsky in alt.sysadmin.recovery
On Sun, Jan 21, 2001 at 01:18:54PM +0100, Alexander Jerusalem wrote: > When the database connection is closed, no memory is reclaimed, the overall > memory usage stays the same. And when I close down all postgresql processes > including postmaster, it's the same. > I'm rather new to Linux and postgresql so I'm not sure if I should call > this a memory leak :-) How much memory is being used? Do you ever go into swap? If not, what's probably happening is Linux is using free memory to cache data like I/O. Linux should automatically release this memory if it's needed by a process. So as long as you have some free memory, I'd say don't worry about it -- but if you start going into swap and this memory isn't released, then you might have a problem. BTW, you're using 'ktop', the KDE front end to 'top'? If you're concerned about memory usage, I'd definately recommend not running KDE, X, or any other GUI stuff. HTH, Neil -- Neil Conway <neilconway@home.com> Get my GnuPG key from: http://klamath.dyndns.org/mykey.asc Encrypted mail welcomed Violence is to dictatorship as propaganda is to democracy. -- Noam Chomsky
Neil, thank you for your answer, I thought about that possibility and it is possible since that computer has 512 MB RAM. But when I start and stop other programs like emacs the memory is freed as soon as I stop them. As to KDE: I'm not concerned about a lack of memory in general but I'm about to deploy an application on a server that I hope will be running for a long time without me having to restart it every two days because of a memory leak in some software. Anyway, I hope you're right, I'll just try it :-) thanks, Alexander Jerusalem ajeru@gmx.net vknn At 18:49 21.01.01, Neil Conway wrote: >On Sun, Jan 21, 2001 at 01:18:54PM +0100, Alexander Jerusalem wrote: > > When the database connection is closed, no memory is reclaimed, the > overall > > memory usage stays the same. And when I close down all postgresql > processes > > including postmaster, it's the same. > > I'm rather new to Linux and postgresql so I'm not sure if I should call > > this a memory leak :-) > >How much memory is being used? Do you ever go into swap? If not, >what's probably happening is Linux is using free memory to cache data >like I/O. Linux should automatically release this memory if it's >needed by a process. So as long as you have some free memory, I'd >say don't worry about it -- but if you start going into swap and >this memory isn't released, then you might have a problem. > >BTW, you're using 'ktop', the KDE front end to 'top'? If you're >concerned about memory usage, I'd definately recommend not running >KDE, X, or any other GUI stuff. > >HTH, > >Neil > >-- >Neil Conway <neilconway@home.com> >Get my GnuPG key from: http://klamath.dyndns.org/mykey.asc >Encrypted mail welcomed > >Violence is to dictatorship as propaganda is to democracy. > -- Noam Chomsky
Hello, I'm converting a mysql database to postgres. Is there an equivalent for the enum data type? Thanks, Steve L
On Sun, Jan 21, 2001 at 10:33:02PM -0500, Steve Leibel wrote:
> Hello,
>
> I'm converting a mysql database to postgres. Is there an equivalent
> for the enum data type?
If you want to make a column limited to few certain values, you can
define it something like:
mycolumn varchar(3) check (mycolumn in ('foo', 'bar', 'baz'))
That would be somewhat similar in effec to mysql's
mycolumn enum('foo', 'bar', 'baz')
Zach
--
xach@xach.com Zachary Beane http://www.xach.com/
Steve Leibel writes: > I'm converting a mysql database to postgres. Is there an equivalent > for the enum data type? No, but you can put the enum data in a separate table and join them. This also makes the operation of adding entries to the enum list better defined. Dan
At 13:18 21/01/01 +0100, Alexander Jerusalem wrote: >Hi all, > >I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat >Linux 7. I'm sending lots of insert statements to the postgresql server >from another machine via JDBC. During that process postgresql continues to >take up more and more memory and seemingly never returns it to the system. >Oddly if I watch the postmaster and it's sub processes in ktop, I can't >see which process takes up this memory. ktop shows that the postgresql >related processes have a constant memory usage but the overall memory >usage always increases as long as I continue to send insert statements. > >When the database connection is closed, no memory is reclaimed, the >overall memory usage stays the same. And when I close down all postgresql >processes including postmaster, it's the same. >I'm rather new to Linux and postgresql so I'm not sure if I should call >this a memory leak :-) >Has anybody experienced a similar thing? I'm not sure myself. You can rule out JDBC (or Java) here as you say you are connecting from another machine. When your JDBC app closes, does it call the connection's close() method? Does any messages like "Unexpected EOF from client" appear on the server side? The only other thing that comes to mine is possibly something weird is happening with IPC. After you closed down postgres, does ipcclean free up any memory? I'm cc'in the hackers list and the new jdbc list. Peter >thanks, >Alexander Jerusalemvknn
* Peter Mount <peter@retep.org.uk> [010122 13:21] wrote: > At 13:18 21/01/01 +0100, Alexander Jerusalem wrote: > >Hi all, > > > >I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat > >Linux 7. I'm sending lots of insert statements to the postgresql server > >from another machine via JDBC. During that process postgresql continues to > >take up more and more memory and seemingly never returns it to the system. > >Oddly if I watch the postmaster and it's sub processes in ktop, I can't > >see which process takes up this memory. ktop shows that the postgresql > >related processes have a constant memory usage but the overall memory > >usage always increases as long as I continue to send insert statements. > > > >When the database connection is closed, no memory is reclaimed, the > >overall memory usage stays the same. And when I close down all postgresql > >processes including postmaster, it's the same. > >I'm rather new to Linux and postgresql so I'm not sure if I should call > >this a memory leak :-) > >Has anybody experienced a similar thing? > > I'm not sure myself. You can rule out JDBC (or Java) here as you say you > are connecting from another machine. > > When your JDBC app closes, does it call the connection's close() method? > Does any messages like "Unexpected EOF from client" appear on the server side? > > The only other thing that comes to mine is possibly something weird is > happening with IPC. After you closed down postgres, does ipcclean free up > any memory? I don't know if this is valid for Linux, but it is how FreeBSD works, for the most part used memory is never free'd, it is only marked as reclaimable. This is so the system can cache more data. On a freshly booted FreeBSD box you'll have a lot of 'free' memory, after the box has been running for a long time the 'free' memory will probably never go higher that 10megs, the rest is being used as cache. The main things you have to worry about is: a) really running out of memory (are you useing a lot of swap?) b) not cleaning up IPC as Peter suggested. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk."
At 21:40 22.01.01, Peter Mount wrote: >At 13:18 21/01/01 +0100, Alexander Jerusalem wrote: >>Hi all, >> >>I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat >>Linux 7. I'm sending lots of insert statements to the postgresql server >>>from another machine via JDBC. During that process postgresql continues to >>take up more and more memory and seemingly never returns it to the >>system. Oddly if I watch the postmaster and it's sub processes in ktop, I >>can't see which process takes up this memory. ktop shows that the >>postgresql related processes have a constant memory usage but the overall >>memory usage always increases as long as I continue to send insert statements. >> >>When the database connection is closed, no memory is reclaimed, the >>overall memory usage stays the same. And when I close down all postgresql >>processes including postmaster, it's the same. >>I'm rather new to Linux and postgresql so I'm not sure if I should call >>this a memory leak :-) >>Has anybody experienced a similar thing? > >I'm not sure myself. You can rule out JDBC (or Java) here as you say you >are connecting from another machine. > >When your JDBC app closes, does it call the connection's close() method? >Does any messages like "Unexpected EOF from client" appear on the server side? > >The only other thing that comes to mine is possibly something weird is >happening with IPC. After you closed down postgres, does ipcclean free up >any memory? > >I'm cc'in the hackers list and the new jdbc list. > >Peter Thanks for your answer! Yes I'm calling Connection.close(). I don't get any error messages but maybe I just don't see them because postgresql is started automatically at run level 3. I'm not sure where the output goes. (pg_log contains only garbage or maybe it's a binary file) I tried ipcclean right now and it doesn't free the memory but it gives me some messages that I cannot interpret: Shared memory 0 ... skipped. Process still exists (pid ). Shared memory 1 ... skipped. Process still exists (pid ). Shared memory 2 ... skipped. Process still exists (pid ). Shared memory 3 ... skipped. Process still exists (pid ). Semaphore 0 ... resource(s) deleted Semaphore 1 ... resource(s) deleted Oddly, when I try to run ipcclean a second time, it says: ipcclean: You still have a postmaster running. Which is not the case as ps -e proves. Alexander Jerusalem ajeru@gmx.net vknn
At 22:29 22.01.01, Alfred Perlstein wrote: >* Peter Mount <peter@retep.org.uk> [010122 13:21] wrote: > > At 13:18 21/01/01 +0100, Alexander Jerusalem wrote: > > >Hi all, > > > > > >I'm experiencing some strange behaviour with postgresql 7.0.3 on Red Hat > > >Linux 7. I'm sending lots of insert statements to the postgresql server > > >from another machine via JDBC. During that process postgresql > continues to > > >take up more and more memory and seemingly never returns it to the > system. > > >Oddly if I watch the postmaster and it's sub processes in ktop, I can't > > >see which process takes up this memory. ktop shows that the postgresql > > >related processes have a constant memory usage but the overall memory > > >usage always increases as long as I continue to send insert statements. > > > > > >When the database connection is closed, no memory is reclaimed, the > > >overall memory usage stays the same. And when I close down all postgresql > > >processes including postmaster, it's the same. > > >I'm rather new to Linux and postgresql so I'm not sure if I should call > > >this a memory leak :-) > > >Has anybody experienced a similar thing? > > > > I'm not sure myself. You can rule out JDBC (or Java) here as you say you > > are connecting from another machine. > > > > When your JDBC app closes, does it call the connection's close() method? > > Does any messages like "Unexpected EOF from client" appear on the > server side? > > > > The only other thing that comes to mine is possibly something weird is > > happening with IPC. After you closed down postgres, does ipcclean free up > > any memory? > >I don't know if this is valid for Linux, but it is how FreeBSD >works, for the most part used memory is never free'd, it is only >marked as reclaimable. This is so the system can cache more data. >On a freshly booted FreeBSD box you'll have a lot of 'free' memory, >after the box has been running for a long time the 'free' memory >will probably never go higher that 10megs, the rest is being used >as cache. > >The main things you have to worry about is: >a) really running out of memory (are you useing a lot of swap?) >b) not cleaning up IPC as Peter suggested. Thanks for your answer! I'm rather new to Linux, so I can't tell if it's that way on Linux. But I noticed that other programs free some memory when I quit them. But it's true that I'm not running out of memory. I have 300 MB of free RAM and no swap space is used. As I wrote in reply to Peters mail, ipcclean doesn't change anything. Alexander Jerusalem ajeru@gmx.net vknn
Hi Alexander, I've noticed that the PG 7.03 ipcclean script uses "ps x | grep -s 'postmaster'" to determine if a postmaster daemon is still running, which at least for Mandrake Linux 7.2 doesn't work as expected. With this version of linux, the ps & grep combination will find itself and then ipcclean will complain about an existing postmaster. I found the solution to this being to edit the ipcclean script and change the "ps x | grep -s 'postmaster'" part to "ps -e | grep -s 'postmaster'". This then works correctly with Mandrake 7.2. Regards and best wishes, Justin Clift <snip> > > Oddly, when I try to run ipcclean a second time, it says: ipcclean: You > still have a postmaster running. Which is not the case as ps -e proves. > > Alexander Jerusalem > ajeru@gmx.net > vknn
Justin Clift writes: > I found the solution to this being to edit the ipcclean script and > change the "ps x | grep -s 'postmaster'" part to "ps -e | grep -s > 'postmaster'". This then works correctly with Mandrake 7.2. A standard way of finding a process by name without the grep itself appearing is use something like "grep '[p]ostmaster'". -- Pete Forman -./\.- Disclaimer: This post is originated WesternGeco -./\.- by myself and does not represent pete.forman@westerngeco.com -./\.- opinion of Schlumberger, Baker http://www.crosswinds.net/~petef -./\.- Hughes or their divisions.
Hi Clift,
you are right, I have the same problem on RedHat. After I inserted -e it
works so far. But there's something else that seems strange to me I'm not
quite sure if I'm reading this right since I understand only half of what
happens in this script. After the comment that says "Don't do anything if
process still running..." on line there is the following sequence of lines:
ps hj$ipcs_pid >/dev/null 2>&1
if [ $? -eq 0 ]; then
echo "skipped...."
As I understand it the if statement tests the output of the previous ps
statement. The strange thing is that the variable $ipcs_pid is never used
anywhere before this line, so I think it's always null (or whatever this
scripting language defaults to). There are three other variables ipcs_id,
ipcs_cpid and ipcs_lpid but no ipcs_pid. If I'm right here, it seems that
this script does effectively nothing in terms of shared memory.
Please tell me if I'm on a completely wrong track :-)
Alexander Jerusalem
ajeru@gmx.net
vknn
At 03:03 23.01.01, Justin Clift wrote:
>Hi Alexander,
>
>I've noticed that the PG 7.03 ipcclean script uses "ps x | grep -s
>'postmaster'" to determine if a postmaster daemon is still running,
>which at least for Mandrake Linux 7.2 doesn't work as expected. With
>this version of linux, the ps & grep combination will find itself and
>then ipcclean will complain about an existing postmaster.
>
>I found the solution to this being to edit the ipcclean script and
>change the "ps x | grep -s 'postmaster'" part to "ps -e | grep -s
>'postmaster'". This then works correctly with Mandrake 7.2.
>
>Regards and best wishes,
>
>Justin Clift
>
><snip>
> >
> > Oddly, when I try to run ipcclean a second time, it says: ipcclean: You
> > still have a postmaster running. Which is not the case as ps -e proves.
> >
> > Alexander Jerusalem
> > ajeru@gmx.net
> > vknn
Alexander Jerusalem <ajeru@gmx.net> writes:
> you are right, I have the same problem on RedHat. After I inserted -e it
> works so far. But there's something else that seems strange to me I'm not
> quite sure if I'm reading this right since I understand only half of what
> happens in this script. After the comment that says "Don't do anything if
> process still running..." on line there is the following sequence of lines:
> ps hj$ipcs_pid >/dev/null 2>&1
> if [ $? -eq 0 ]; then
> echo "skipped...."
> As I understand it the if statement tests the output of the previous ps
> statement. The strange thing is that the variable $ipcs_pid is never used
> anywhere before this line, so I think it's always null (or whatever this
> scripting language defaults to). There are three other variables ipcs_id,
> ipcs_cpid and ipcs_lpid but no ipcs_pid. If I'm right here, it seems that
> this script does effectively nothing in terms of shared memory.
I think you are right --- the Linux portion of this script is broken.
Aside from the bogus variable, the awk call at the top of the loop is
wrong (printf has three arguments and only two percents). Given those
two typos, there are probably more.
Feel free to submit a patch to make it actually work ...
regards, tom lane