From owner-cvs-src@FreeBSD.ORG  Tue Apr  8 10:15:08 2003
Return-Path: <owner-cvs-src@FreeBSD.ORG>
Delivered-To: cvs-src@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id A751D37B401; Tue,  8 Apr 2003 10:15:08 -0700 (PDT)
Received: from flood.ping.uio.no (flood.ping.uio.no [129.240.78.31])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 7E9FE43FAF; Tue,  8 Apr 2003 10:15:07 -0700 (PDT)
	(envelope-from des@ofug.org)
Received: by flood.ping.uio.no (Postfix, from userid 2602)
	id DD9F05308; Tue,  8 Apr 2003 19:15:04 +0200 (CEST)
X-URL: http://www.ofug.org/~des/
X-Disclaimer: The views expressed in this message do not necessarily
  coincide with those of any organisation or company with
  which I am or have been affiliated.
To: Nate Lawson <nate@root.org>
From: Dag-Erling Smorgrav <des@ofug.org>
Date: Tue, 08 Apr 2003 19:15:04 +0200
In-Reply-To: <Pine.BSF.4.21.0304081001400.27414-100000@root.org> (Nate
 Lawson's message of "Tue, 8 Apr 2003 10:09:20 -0700 (PDT)")
Message-ID: <xzpof3gnc6f.fsf@flood.ping.uio.no>
User-Agent: Gnus/5.090015 (Oort Gnus v0.15) Emacs/21.2
References: <Pine.BSF.4.21.0304081001400.27414-100000@root.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
cc: src-committers@freebsd.org
cc: cvs-src@freebsd.org
cc: Alexander Leidinger <Alexander@Leidinger.net>
cc: sos@spider.deepcore.dk
cc: cvs-all@freebsd.org
cc: sos@freebsd.org
Subject: Re: cvs commit: src/sys/dev/ata ata-all.c ata-all.h
 ata-chipset.cata-dma.c ata-pci.c ata-pci.h
X-BeenThere: cvs-src@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the src tree <cvs-src.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src>
List-Post: <mailto:cvs-src@freebsd.org>
List-Help: <mailto:cvs-src-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 08 Apr 2003 17:15:09 -0000

Nate Lawson <nate@root.org> writes:
> Tagged queuing is orthogonal to caching.  TQ allows multiple transactions
> to be passed to the drive, allowing it to order and aggregate the requests
> as it thinks best.  TQ can be done with no cache because all the drive is
> tracking is handles to transactions (typically 16 bit ids).  Think of it
> as more like a pipeline than a cache.

It can't be done without cache, because you can't queue and reorder
transactions without some sort of cache.

DES
-- 
Dag-Erling Smorgrav - des@ofug.org