From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from plane.gmane.org ([80.91.229.3]:41948 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752310AbaAVUzx (ORCPT ); Wed, 22 Jan 2014 15:55:53 -0500 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1W64q0-0004MG-2s for linux-btrfs@vger.kernel.org; Wed, 22 Jan 2014 21:55:52 +0100 Received: from 50-0-67-239.dsl.static.fusionbroadband.com ([50.0.67.239]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 22 Jan 2014 21:55:52 +0100 Received: from rogerb by 50-0-67-239.dsl.static.fusionbroadband.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 22 Jan 2014 21:55:52 +0100 To: linux-btrfs@vger.kernel.org From: Roger Binns Subject: Re: Working on Btrfs as topic for master thesis Date: Wed, 22 Jan 2014 12:55:39 -0800 Message-ID: References: <8E968DF3B7EC0D40B67B5A9D25675A6A03FC70@MBXSRV03EDU.edu.local> <20140122121220.GF6498@twin.jikos.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 In-Reply-To: <20140122121220.GF6498@twin.jikos.cz> Sender: linux-btrfs-owner@vger.kernel.org List-ID: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 22/01/14 04:12, David Sterba wrote: > I have done some work here, so far it's stalled due to more important > work. > > https://btrfs.wiki.kernel.org/index.php/Project_ideas#Compression_enhancements > > Do you have other suggestions beyond what's proposed there? There was the theoretical side - ie coming up with a way of defining perfection which then allows measuring against. For example you have going up to a 128K block size but without knowing the theoretical best we don't know if that is a stopgap or very good. That also feeds into things like if it would be a good idea to go back afterwards (perhaps as part of defrag) and spend more effort on (re)compression. Another consideration is perhaps having the compression dictionary kept separate from the compressed blocks thereby allowing it to be used across blocks and potentially files. Compressors like smaz (very good on short pieces of text) work by having a precomputed dictionary - perhaps those can be used too. Roger -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) iEYEARECAAYFAlLgMEQACgkQmOOfHg372QRGDACeI604tw4OZsITHZEY60O6aiQX GD4AoIj9s2rbVWiRp2W4FR6rkAf+iSsH =cD4/ -----END PGP SIGNATURE-----