Date: Mon, 13 Aug 2012 11:41:20 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Petri Helenius <petri@helenius.fi> Cc: freebsd-fs@freebsd.org Subject: Re: zero deleted blocks Message-ID: <20120813084120.GA2352@deviant.kiev.zoral.com.ua> In-Reply-To: <7BDA02A3-99ED-4F67-9B2D-5AAF1523642E@helenius.fi> References: <7BDA02A3-99ED-4F67-9B2D-5AAF1523642E@helenius.fi>
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--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--
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