From owner-freebsd-arch@FreeBSD.ORG  Thu Mar  1 14:28:45 2012
Return-Path: <owner-freebsd-arch@FreeBSD.ORG>
Delivered-To: arch@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id E5CBD1065670;
	Thu,  1 Mar 2012 14:28:45 +0000 (UTC)
	(envelope-from pawel@dawidek.net)
Received: from mail.dawidek.net (60.wheelsystems.com [83.12.187.60])
	by mx1.freebsd.org (Postfix) with ESMTP id 8F5318FC08;
	Thu,  1 Mar 2012 14:28:45 +0000 (UTC)
Received: from localhost (58.wheelsystems.com [83.12.187.58])
	by mail.dawidek.net (Postfix) with ESMTPSA id 169C413C;
	Thu,  1 Mar 2012 15:28:44 +0100 (CET)
Date: Thu, 1 Mar 2012 15:27:27 +0100
From: Pawel Jakub Dawidek <pjd@FreeBSD.org>
To: Konstantin Belousov <kostikbel@gmail.com>
Message-ID: <20120301142726.GF1336@garage.freebsd.pl>
References: <20120203193719.GB3283@deviant.kiev.zoral.com.ua>
	<CAJ-FndABi21GfcCRTZizCPc_Mnxm1EY271BiXcYt9SD_zXFpXw@mail.gmail.com>
	<20120225151334.GH1344@garage.freebsd.pl>
	<CAJ-FndBBKHrpB1MNJTXx8gkFXR2d-O6k5-HJeOAyv2DznpN-QQ@mail.gmail.com>
	<20120225194630.GI1344@garage.freebsd.pl>
	<20120301111624.GB30991@reks>
	<20120301141247.GE1336@garage.freebsd.pl>
	<20120301141553.GT55074@deviant.kiev.zoral.com.ua>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
	protocol="application/pgp-signature"; boundary="KR/qxknboQ7+Tpez"
Content-Disposition: inline
In-Reply-To: <20120301141553.GT55074@deviant.kiev.zoral.com.ua>
X-OS: FreeBSD 10.0-CURRENT amd64
User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: Attilio Rao <attilio@FreeBSD.org>, arch@FreeBSD.org,
	Gleb Kurtsou <gleb.kurtsou@gmail.com>
Subject: Re: Prefaulting for i/o buffers
X-BeenThere: freebsd-arch@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussion related to FreeBSD architecture <freebsd-arch.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-arch>
List-Post: <mailto:freebsd-arch@freebsd.org>
List-Help: <mailto:freebsd-arch-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-arch>,
	<mailto:freebsd-arch-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 01 Mar 2012 14:28:46 -0000


--KR/qxknboQ7+Tpez
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Thu, Mar 01, 2012 at 04:15:53PM +0200, Konstantin Belousov wrote:
> On Thu, Mar 01, 2012 at 03:12:47PM +0100, Pawel Jakub Dawidek wrote:
> > Yes, namecache is already library-like, but I was talking about the
> > buffer cache. I managed to bypass it eventually with suggestions from
> > ups@, but for a long time I was sure it isn't at all possible.
>=20
> I am quite curious, in which way buffer layer is mandatory ?

As I said, it is not, but it took me a while to figure it out.
I remember having massive problems when I was working on getting mmaped
reads/writes right and bypassing the buffer cache and talking to the
page cache directly. I don't think there was single example in the tree
that was showing it can be done at that time. Currently tmpfs is using
the same approach as ZFS, AFAIK.

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

--KR/qxknboQ7+Tpez
Content-Type: application/pgp-signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.18 (FreeBSD)

iEYEARECAAYFAk9Ph04ACgkQForvXbEpPzS4gwCgiqSLlzrJ2LRC4FHPSOVsjCQd
ZbwAn1yCaWUq3kik4zzQ+ClcPCQsUpbk
=LM1U
-----END PGP SIGNATURE-----

--KR/qxknboQ7+Tpez--