Memory issue on FreeBSD

Hi,

I am running a PostgreSQL server on FreeBSD. The system has 32GB memory.
Usually I use top to examine the memory usage of the system. After a
while, a part, approximately 5GB, vanish from top, so that the memory
rounds up to 27GB. After restarting PostgreSQL, I have all 32GB again
available, but then it's already slightly decreasing. It's a standalone
database server. It has an OpenStreetMap world database running with
353GB data (with indices).

Some system information:
# uname -r
9.0-RELEASE-p3
# pg_ctl --version
pg_ctl (PostgreSQL) 9.1.6

# cat /boot/loader.conf
...
kern.ipc.semmni=256
kern.ipc.semmns=512
kern.ipc.semmnu=256
kern.ipc.semumr=200
vm.pmap.shpgperproc=400
vm.pmap.pv_entry_max=50331648
...

# cat /pgdata/data/postgresql.conf
...
default_statistics_target = 50 # pgtune wizard 2012-04-04
maintenance_work_mem = 4GB # pgtune wizard 2012-04-04
constraint_exclusion = on # pgtune wizard 2012-04-04
checkpoint_completion_target = 0.9 # pgtune wizard 2012-04-04
effective_cache_size = 24GB # pgtune wizard 2012-04-04
work_mem = 768MB # pgtune wizard 2012-04-04
wal_buffers = 16MB # pgtune wizard 2012-04-04
checkpoint_segments = 60 # 20
shared_buffers = 8GB # pgtune wizard 2012-04-04
max_connections = 100
synchronous_commit = off

So any help finding out why my system "looses" some RAM is greatly
appreciated :-) If more information is needed I will gladly provide it.

Frank

--
Frank BRONIEWSKI

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