From owner-freebsd-stable@FreeBSD.ORG Wed Sep 3 12:40:00 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6A041106564A for ; Wed, 3 Sep 2008 12:40:00 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.terabit.net.ua (mail.terabit.net.ua [195.137.202.147]) by mx1.freebsd.org (Postfix) with ESMTP id 0A6788FC13 for ; Wed, 3 Sep 2008 12:39:59 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from skuns.zoral.com.ua ([91.193.166.194] helo=mail.zoral.com.ua) by mail.terabit.net.ua with esmtp (Exim 4.63 (FreeBSD)) (envelope-from ) id 1KareQ-000J75-Al; Wed, 03 Sep 2008 15:39:58 +0300 Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m83Cdt5s033290 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 3 Sep 2008 15:39:55 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m83CdteT010986; Wed, 3 Sep 2008 15:39:55 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2/Submit) id m83Cdter010984; Wed, 3 Sep 2008 15:39:55 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 3 Sep 2008 15:39:55 +0300 From: Kostik Belousov To: Igor Sysoev Message-ID: <20080903123955.GE2038@deviant.kiev.zoral.com.ua> References: <20080903095352.GA62541@rambler-co.ru> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="iHi2w+J2QYXBOoee" Content-Disposition: inline In-Reply-To: <20080903095352.GA62541@rambler-co.ru> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: ClamAV version 0.93.3, clamav-milter version 0.93.3 on skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on skuns.kiev.zoral.com.ua X-Virus-Scanned: mail.terabit.net.ua 1KareQ-000J75-Al 4021e6aeaec9c80292b1dea13860bb81 X-Terabit: YES Cc: Tor Egge , freebsd-stable@freebsd.org Subject: Re: vfs.ffs.rawreadahead X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Sep 2008 12:40:00 -0000 --iHi2w+J2QYXBOoee Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Sep 03, 2008 at 01:53:52PM +0400, Igor Sysoev wrote: > Hi, >=20 > could anyone tell what does vfs.ffs.rawreadahead enable ? > As I understand it's used in DIRECTIO code that allows read data > directly to an userland buffer bypassing the buffer cache. > What I can not understand where the read ahead data can be placed in ? The operation of the ffs_rawread is more accurately described as bypassing the page cache. It creates the physical buffer that maps the user pages. The readahead is performed only when the supplied user memory region is bigger then blocksize. In this case, two reads are performed simultaneously, with both buffers mapping consequent blocks from user-supplied buffers. The read operation looks like footsteps. --iHi2w+J2QYXBOoee Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAki+hZoACgkQC3+MBN1Mb4iUzwCeK6uS/EA1LU6Pb9cLEE+L/e16 TawAoMnUlFdZUm11S2ApwjBVO9SToWoW =zxas -----END PGP SIGNATURE----- --iHi2w+J2QYXBOoee--