From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?utf-8?B?SsO2cm4=?= Engel Subject: Re: [PATCH] LogFS take three Date: Wed, 16 May 2007 15:20:35 +0200 Message-ID: <20070516132035.GJ5472@lazybastard.org> References: <20070515151919.GA32510@lazybastard.org> <20070516122603.GE5472@lazybastard.org> <84144f020705160536i189f6206sffc964a145177da7@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, akpm@osdl.org, Albert Cahalan , Thomas Gleixner , Jan Engelhardt , Evgeniy Polyakov , Greg KH , Ingo Oeser To: Pekka Enberg Return-path: Received: from lazybastard.de ([212.112.238.170]:58222 "EHLO longford.lazybastard.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752864AbXEPNYy (ORCPT ); Wed, 16 May 2007 09:24:54 -0400 Content-Disposition: inline In-Reply-To: <84144f020705160536i189f6206sffc964a145177da7@mail.gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 16 May 2007 15:36:44 +0300, Pekka Enberg wrote: > On 5/16/07, J=C3=B6rn Engel wrote: > > > >More trouble? >=20 > Forgot to add (see below). Seems logfs_segment_read would be simpler > too if you fixed this. Would it? I think that code would still be needed, although possibly i= n a different function. There are two minor drawbacks to using the page cache, btw: - Indirect blocks need some mapping too. So either I need to steal a bit from the inode space or from the fpos space. - OOM handling is a bit more complicated. I would need a mempool for that. > >[ Objects are the units that get compressed. Segments can contain b= oth > >compressed and uncompressed objects. ] > > > >It is a trade-off. Each object has a 24 Byte header plus X Bytes of > >data. Whether the data is compressed or not is indicated in the hea= der. >=20 > Was my point really. Why do segments contain both compressed and > uncompressed objects? Compressing random data will actually enlarge it. If that happens I simply store the verbatim uncompressed data instead and mark it as such= =2E There is also demand for a user-controlled bit in the inode to disable compression completely. All those .jpg, .mpg, .mp3, etc. just waste time by trying and failing to compress them. J=C3=B6rn --=20 Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface. -- Doug MacIlroy - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html