Postgress memory leak with JBoss3.2.6 and large DB

Hey guys,

We are running a Linux 2.4 enterprise edition box with 6GB of RAM,
Postgres 8.0.3. Our applications are running on JBoss 3.2.6. We are having a
Database of over 22GB in size.

The problem is when we are querying a specific set of table (which all
tables having over 100K of rows), the Postgres user process takes over or
close 700MB of memory. This is just to return 3000 odd rows. Even though we
have lot of data we still do not have that much to eat up this much of
memory.

What I would like to know is, is there any setting in the Postgres or in
Linux that we can tune this with?

Our Postgres.conf file has the following settings, we have been playing
around wit this but still no success.

shared_buffers = 5000

effective_cache_size = 10000

work_mem = 2048

random_page_cost = 2

A sample of the top command is given below.

12:38:05 up 136 days, 7:06, 10 users, load average: 7.69, 4.83, 3.78

459 processes: 458 sleeping, 1 running, 0 zombie, 0 stopped

CPU states: cpu user nice system irq softirq iowait idle

total 9.6% 0.0% 1.8% 0.0% 0.0% 88.3% 0.0%

cpu00 11.3% 0.0% 0.3% 0.0% 0.1% 88.0% 0.0%

cpu01 8.9% 0.0% 2.5% 0.0% 0.0% 88.4% 0.0%

cpu02 14.1% 0.0% 2.9% 0.0% 0.0% 82.9% 0.0%

cpu03 4.1% 0.0% 1.5% 0.1% 0.1% 93.8% 0.0%

Mem: 6153976k av, 6092084k used, 61892k free, 0k shrd, 6232k
buff

4769364k actv, 916224k in_d, 111336k in_c

Swap: 1052216k av, 761912k used, 290304k free 3036700k
cached

PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND

19736 postgres 15 0 508M 448M 42840 D 0.9 7.4 0:22 0 postmaster

19740 postgres 15 0 507M 441M 41428 D 0.8 7.3 0:21 0 postmaster

19779 postgres 15 0 508M 472M 42828 D 0.8 7.8 0:21 0 postmaster

19789 postgres 15 0 508M 477M 42412 D 0.6 7.9 0:21 0 postmaster

19738 postgres 15 0 507M 438M 41852 D 0.4 7.3 0:21 0 postmaster

14647 postgres 15 0 63948 56M 44236 D 0.1 0.9 0:41 3 postmaster

As you can see the postmaster users are taking way over the memory that
should be taken.

If any of you can give us some pointers we would really appreciate that and
thanks in advance.

Regards

Indika.