Hi,
I recently had a discussion of PostgreSQLs memory usage on FreeBSD,
notably the display of the different memory types in top, on the
PostgreSQL mailing list [1]. My server has 32GB ram, of which approx.
8GB vanish from tops display after a while. My question was wether there
is a memory problem on FreeBSD or if top is not capable of dealing well
with PostgreSQLs memory handling, eg. the shared_buffers.
We used a perl script [2] to get a better understanding of the current
memory usage on FreeBSD and a line from the scripts output caught my eye:
> mem_gap_vm: + 8812892160 ( 8404MB) [ 26%] Memory gap: UNKNOWN
I don't have a good understanding of the different types of system
memory, so the question is, in relation with PostgreSQL, if the
mem_gap_vm value can be considered normal or if it is a sign of memory
leak. Since this question is more of a FreeBSD question, we decided to
move the discussion here in order to get more insight on the system
internals :-)
This value equals more or less the shared buffers (shared_buffers=8GB)
setting of PostgreSQL and is stable, which means, it doesn't change
anymore after reaching its peak value.
I did post already some system configuration information in the thread
on the PostgreSQL list, but I am happy to provide all the information
necessary to shed some light on this matter.
Many thanks,
Frank
[1]
http://postgresql.1045698.n5.nabble.com/Memory-issue-on-FreeBSD-td5730651.html
[2] http://www.cyberciti.biz/faq/freebsd-command-to-get-ram-information/
--
Frank BRONIEWSKI
METRICO s.à r.l.
géomètres
technologies d'information géographique
rue des Romains 36
L-5433 NIEDERDONVEN
tél.: +352 26 74 94 - 28
fax.: +352 26 74 94 99
http://www.metrico.lu
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