From owner-freebsd-fs@FreeBSD.ORG Mon Aug 13 08:41:32 2012 Return-Path: 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 115AE106564A for ; Mon, 13 Aug 2012 08:41:32 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.zoral.com.ua (mx0.zoral.com.ua [91.193.166.200]) by mx1.freebsd.org (Postfix) with ESMTP id 82A118FC1D for ; Mon, 13 Aug 2012 08:41:30 +0000 (UTC) Received: from skuns.kiev.zoral.com.ua (localhost [127.0.0.1]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id q7D8fXYj068453; Mon, 13 Aug 2012 11:41:33 +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 (8.14.5/8.14.5) with ESMTP id q7D8fKfW004437; Mon, 13 Aug 2012 11:41:20 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.5/8.14.5/Submit) id q7D8fK0g004436; Mon, 13 Aug 2012 11:41:20 +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: Mon, 13 Aug 2012 11:41:20 +0300 From: Konstantin Belousov To: Petri Helenius Message-ID: <20120813084120.GA2352@deviant.kiev.zoral.com.ua> References: <7BDA02A3-99ED-4F67-9B2D-5AAF1523642E@helenius.fi> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="GvXjxJ+pjyke8COw" Content-Disposition: inline In-Reply-To: <7BDA02A3-99ED-4F67-9B2D-5AAF1523642E@helenius.fi> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: clamav-milter 0.95.2 at skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.0 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 Cc: freebsd-fs@freebsd.org Subject: Re: zero deleted blocks X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Aug 2012 08:41:32 -0000 --GvXjxJ+pjyke8COw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 13, 2012 at 09:01:57AM +0300, Petri Helenius wrote: >=20 > Hi, >=20 > Is it possible to have ZFS or UFS to zero out the deallocated blocks > to facilitate VM disk compaction? I think TRIM support in UFS can be extended to zero-out the deleted blocks, with relatively small amount of work. Basically, in ufs/ffs/ffs_alloc.c:ffs_blkfree(), a BIO_WRITE of zero buffer shall be issued instead of BIO_DELETE. More, it seems that zero_region can be often used as a source of zeroes. --GvXjxJ+pjyke8COw Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (FreeBSD) iEYEARECAAYFAlAovbAACgkQC3+MBN1Mb4g3pQCghN2SVIK/H1lFD+hTeaf5y4/F YsUAoOb0gHTojP6R0DfCq/SBcrBiVpHA =ZjGj -----END PGP SIGNATURE----- --GvXjxJ+pjyke8COw--