From owner-freebsd-fs@FreeBSD.ORG  Thu Jan 27 03:00:26 2005
Return-Path: <owner-freebsd-fs@FreeBSD.ORG>
Delivered-To: freebsd-fs@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id DAF8116A4CE
	for <freebsd-fs@freebsd.org>; Thu, 27 Jan 2005 03:00:26 +0000 (GMT)
Received: from dyson.jdyson.com (dsl-static-206-246-160-137.iquest.net
	[206.246.160.137])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 2B20743D31
	for <freebsd-fs@freebsd.org>; Thu, 27 Jan 2005 03:00:26 +0000 (GMT)
	(envelope-from toor@dyson.jdyson.com)
Received: from dyson.jdyson.com (localhost [127.0.0.1])
	by dyson.jdyson.com (8.12.8/8.9.3) with ESMTP id j0R30PNF000714
	for <freebsd-fs@freebsd.org>; Wed, 26 Jan 2005 22:00:25 -0500 (EST)
	(envelope-from toor@dyson.jdyson.com)
Received: (from toor@localhost)
	by dyson.jdyson.com (8.12.8/8.12.8/Submit) id j0R30PE7000713
	for freebsd-fs@freebsd.org; Wed, 26 Jan 2005 22:00:25 -0500 (EST)
Message-Id: <200501270300.j0R30PE7000713@dyson.jdyson.com>
To: freebsd-fs@freebsd.org
Date: Wed, 26 Jan 2005 22:00:24 -0500 (EST)
From: jdy@jdyson.com
X-Mailer: ELM [version 2.4ME+ PL54 (25)]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
cc: dyson@iquest.net
Subject: Write caching on FreeBSD
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
Reply-To: jdy@jdyson.com
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
	<mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
	<mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 27 Jan 2005 03:00:27 -0000

Quick comment:

	When doing/updating the write code, I carefully
	limited the amount of pending write data so that
	the system wouldn't 'go to sleep' while trying
	to sync out massive amounts of data.  For convienience,
	this amount of write space was limited by the disk
	cache buffer representation.  My original disk cache
	code wasn't limited to the cache buffers, and would	
	actually create large numbers of dirty pages.  This
	allowed for faster performance, except under load.

	I was interested in the high load performance conditions,
	and some mods have apparently been made to support
	more pending writes (by increasing the disk buffer
	cache representations?)  Anyway, it seems like FreeBSD
	currently has a good compromise (better than my original,
	but also better than a no-holds barred scheme that
	creates lots of dirty pages.)

	John