From owner-freebsd-fs@FreeBSD.ORG  Fri Apr 23 06:08:56 2010
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 9B606106566C;
	Fri, 23 Apr 2010 06:08:56 +0000 (UTC)
	(envelope-from pjd@garage.freebsd.pl)
Received: from mail.garage.freebsd.pl (chello089077043238.chello.pl
	[89.77.43.238])
	by mx1.freebsd.org (Postfix) with ESMTP id 33CCE8FC08;
	Fri, 23 Apr 2010 06:08:55 +0000 (UTC)
Received: by mail.garage.freebsd.pl (Postfix, from userid 65534)
	id 8BB7445E8E; Fri, 23 Apr 2010 08:08:54 +0200 (CEST)
Received: from localhost (chello089077043238.chello.pl [89.77.43.238])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by mail.garage.freebsd.pl (Postfix) with ESMTP id 554384569A;
	Fri, 23 Apr 2010 08:08:49 +0200 (CEST)
Date: Fri, 23 Apr 2010 08:08:50 +0200
From: Pawel Jakub Dawidek <pjd@FreeBSD.org>
To: Andriy Gapon <avg@icyb.net.ua>
Message-ID: <20100423060850.GB1670@garage.freebsd.pl>
References: <4BD0C802.3000004@icyb.net.ua>
Mime-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="BwCQnh7xodEAoBMC"
Content-Disposition: inline
In-Reply-To: <4BD0C802.3000004@icyb.net.ua>
User-Agent: Mutt/1.4.2.3i
X-PGP-Key-URL: http://people.freebsd.org/~pjd/pjd.asc
X-OS: FreeBSD 9.0-CURRENT i386
X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on 
	mail.garage.freebsd.pl
X-Spam-Level: 
X-Spam-Status: No, score=-0.6 required=4.5 tests=BAYES_00,RCVD_IN_SORBS_DUL 
	autolearn=no version=3.0.4
Cc: freebsd-fs@FreeBSD.org, freebsd-geom@FreeBSD.org
Subject: Re: vdev_geom_io: parallelize ?
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: Fri, 23 Apr 2010 06:08:56 -0000


--BwCQnh7xodEAoBMC
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Fri, Apr 23, 2010 at 01:04:50AM +0300, Andriy Gapon wrote:
>=20
> Just thinking out loud.
>=20
> Currently ZFS vdev_geom_io does something like:
> for (...) {
> 	...
> 	g_io_request(...);
> 	biowait(...);
> 	...
> }
> I/O is done in MAXPHYS chunks.
>=20
> If that was changed to first issuing all the requests and only after that
> waiting on them, could there be any performance benefit?
> Or cases of vdev_geom_io with size > MAXPHYS are too rare?
> Or something else?

The vdev_geom_io() function is there only to read ZFS labels, it is not
used during regular I/O. Regular I/O requests are handled asynchronously
by the vdev_geom_io_start() function.

--=20
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!

--BwCQnh7xodEAoBMC
Content-Type: application/pgp-signature
Content-Disposition: inline

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.14 (FreeBSD)

iEYEARECAAYFAkvROXIACgkQForvXbEpPzSM9wCcDPLqokCtvb9D/QzxkGAOX3oL
t90An3ssb9u19Zgw/x32k0xE5P5QLnHF
=LTp5
-----END PGP SIGNATURE-----

--BwCQnh7xodEAoBMC--