To: Jon Brisbin <jon.brisbin@npcinternational.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance on SUSE w/ reiserfs 
In-reply-to: <434ADD46.5060206@npcinternational.com> 
References: <434ADD46.5060206@npcinternational.com>
Comments: In-reply-to Jon Brisbin <jon.brisbin@npcinternational.com>
	message dated "Mon, 10 Oct 2005 16:29:42 -0500"
Date: Mon, 10 Oct 2005 17:54:49 -0400
Message-ID: <6247.1128981289@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Jon Brisbin <jon.brisbin@npcinternational.com> writes:
> I have a SUSE 9 box that is running Postgres 8.0.1 compiled from source. 
> Over time, I see the memory usage of the box go way way up (it's got 
> 8GBs in it and by the end of the day, it'll be all used up) with what 
> looks like cached inodes relating to the extreme IO generated by 
> postgres. We replicate about 10GBs of data every day from our AS/400 
> into postgres, and it is the main database for our intranet portal, 
> which will server 40,000 pages on a good day.

Are you sure it's not cached data pages, rather than cached inodes?
If so, the above behavior is *good*.

People often have a mistaken notion that having near-zero free RAM means
they have a problem.  In point of fact, that is the way it is supposed
to be (at least on Unix-like systems).  This is just a reflection of the
kernel doing what it is supposed to do, which is to use all spare RAM
for caching recently accessed disk pages.  If you're not swapping then
you do not have a problem.

You should be looking at swap I/O rates (see vmstat or iostat) to
determine if you have memory pressure, not "free RAM".

			regards, tom lane