From owner-freebsd-performance@FreeBSD.ORG  Fri Jul 25 23:48:38 2003
Return-Path: <owner-freebsd-performance@FreeBSD.ORG>
Delivered-To: freebsd-performance@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id AC66237B401; Fri, 25 Jul 2003 23:48:38 -0700 (PDT)
Received: from misery.sdf.com (misery.sdf.com [207.200.153.226])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 5795C43F93; Fri, 25 Jul 2003 23:48:36 -0700 (PDT)
	(envelope-from tom@sdf.com)
Received: from tom (helo=localhost)
	by misery.sdf.com with local-esmtp (Exim 2.12 #1)
	id 19gH6M-0005iR-00; Fri, 25 Jul 2003 21:56:14 -0700
Date: Fri, 25 Jul 2003 21:56:08 -0700 (PDT)
From: Tom Samplonius <tom@sdf.com>
To: Terry Lambert <tlambert2@mindspring.com>
In-Reply-To: <3F2220C7.F0179FC4@mindspring.com>
Message-ID: <Pine.BSF.4.05.10307252149000.16986-100000@misery.sdf.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: Sean Chittenden <seanc@FreeBSD.org>
cc: freebsd-database@freebsd.org
cc: freebsd-performance@freebsd.org
cc: Christopher Weimann <cweimann@k12hq.com>
cc: Paul Pathiakis <paul@pathiakis.com>
Subject: Re: Tuning for PostGreSQL Database
X-BeenThere: freebsd-performance@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Performance/tuning <freebsd-performance.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-performance>
List-Post: <mailto:freebsd-performance@freebsd.org>
List-Help: <mailto:freebsd-performance-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sat, 26 Jul 2003 06:48:39 -0000


On Fri, 25 Jul 2003, Terry Lambert wrote:

> Christopher Weimann wrote:
> > So I have conflicting documentation.
> > 
> > I have machine with 4Gig of ram.  What is the maximum
> > value of SHMMAX on FreeBSD?
> 
> Ideally, you would use memory mapped files for this, and not System V
> shared memory, so that the OS could implement swapping policies as it
> saw fit, and could actually swap the data, if nevcessary, instead of
> it sucking up huge amounts of wired memory.

  PostgreSQL is from the good old days of RDMSes when the they would
System V shared memory for everything, and store databases on raw devices
in an effort to utilize as little of the OS as possible, in effort to be
fast and reliable.

  But it does give PostgreSQL the advantage of working with large tables
and databases.  Mmapping a file over 4GB in size would likely exhaust the
VM on a x86.  Or, is it possible to map 4+GB with PAE?

> In any case, POSIX deprecated SysV shared memory years ago, and
> recommends that all code utilize shm_open instead, these days, if
> you insist on using an interface that sucks up huge amounts of
> wired pages and KVA space.
> 
> -- Terry
> 
> 


Tom