From owner-freebsd-fs@FreeBSD.ORG  Thu Dec 20 23:51:42 2007
Return-Path: <owner-freebsd-fs@FreeBSD.ORG>
Delivered-To: freebsd-fs@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 4C33916A417;
	Thu, 20 Dec 2007 23:51:42 +0000 (UTC)
	(envelope-from peter.schuller@infidyne.com)
Received: from smtp.infidyne.com (ds9.infidyne.com [88.80.6.206])
	by mx1.freebsd.org (Postfix) with ESMTP id 0AD5713C45B;
	Thu, 20 Dec 2007 23:51:41 +0000 (UTC)
	(envelope-from peter.schuller@infidyne.com)
Received: from c-8216e555.03-51-73746f3.cust.bredbandsbolaget.se
	(c-8216e555.03-51-73746f3.cust.bredbandsbolaget.se [85.229.22.130])
	by smtp.infidyne.com (Postfix) with ESMTP id 3D20677887;
	Fri, 21 Dec 2007 00:51:40 +0100 (CET)
From: Peter Schuller <peter.schuller@infidyne.com>
To: Julian Elischer <julian@elischer.org>
Date: Fri, 21 Dec 2007 00:51:33 +0100
User-Agent: KMail/1.9.7
References: <fjbb3v$n60$1@ger.gmane.org>
	<200712210036.49040.peter.schuller@infidyne.com>
	<476AFDBC.9040301@elischer.org>
In-Reply-To: <476AFDBC.9040301@elischer.org>
MIME-Version: 1.0
Content-Type: multipart/signed; boundary="nextPart1325381.rZX7Dr3quE";
	protocol="application/pgp-signature"; micalg=pgp-sha1
Content-Transfer-Encoding: 7bit
Message-Id: <200712210051.41936.peter.schuller@infidyne.com>
Cc: freebsd-fs@freebsd.org, ticso@cicely.de, Ivan Voras <ivoras@freebsd.org>
Subject: Re: readv: parallel or sequential?
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
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, 20 Dec 2007 23:51:42 -0000

--nextPart1325381.rZX7Dr3quE
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

> multiple reads and writes to the same file *From different file
> descriptors* (same process or not) might proceed in "parallel" but readv
> and writev will be implemented serially to the filesystem. now IF THE
> FILESYSTEM IS NOT DOING SYNCHRONOUS DISK ACCESSES the reads and writes
> might proceed in parallel or be grouped, clustered or otherwise rearanged.

If the original claims were just as applied to readv/writev, I don't really=
=20
have a problem since there is no guarantee that it will be performed in=20
parallel (though even then, assuming non-synchronous writes, it would=20
certainly be nice if it did pass it along to the device layer in a fashion=
=20
that allowed concurrency).

But when I/O is clearly being done with the intent of concurrency (by using=
=20
AIO or by performing the I/O in different threads/processes), it is more=20
important.

=2D-=20
/ Peter Schuller

PGP userID: 0xE9758B7D or 'Peter Schuller <peter.schuller@infidyne.com>'
Key retrieval: Send an E-Mail to getpgpkey@scode.org
E-Mail: peter.schuller@infidyne.com Web: http://www.scode.org


--nextPart1325381.rZX7Dr3quE
Content-Type: application/pgp-signature; name=signature.asc 
Content-Description: This is a digitally signed message part.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.4 (FreeBSD)

iD8DBQBHawANDNor2+l1i30RApKtAJ42aWOvXKnYbC73AoXaZvza/I1MVwCdFei1
0FAfRm9x1swgNtx3YDTVmww=
=NQ+4
-----END PGP SIGNATURE-----

--nextPart1325381.rZX7Dr3quE--