Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com Message-ID: <02c101c31e3e$7ffdc910$78d96f83@pomello> From: "Max Bowsher" To: "Pierre A. Humblet" , References: <028f01c31e38$0e428c30$78d96f83 AT pomello> <20030519200848 DOT GA246379 AT Worldnet> Subject: Re: SPARSE files considered harmful - please revert Date: Mon, 19 May 2003 20:40:27 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Pierre A. Humblet wrote: > On Mon, May 19, 2003 at 07:54:19PM +0100, Max Bowsher wrote: >> John Vincent wrote: >>> >>> I looked up sparse files on MSDN and found the following link: >>> >>> >> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/fileio/base/sparse_file_operations.asp >>> >>> The most interesting thing is that a sparse file is only sparse if the >> zeros >>> in the file are written with a special operation. I strongly suspect that >>> the patch to support sparse files introduced in cygwin is incorrect (or at >>> least incomplete) >> >> Areas that are simply seeked over, and never written to, should be sparse as >> well. > > Not only they "should be", they are. > >> Anyway: >> >> Based on the posted numbers, global use of sparse files is a bad idea. Can >> we conditionalize sparse files on a $CYGWIN option? (Or something else, I >> don't mind, but the important thing is that it should not be on by default.) > > Why not make in on by default *when it can help*, i.e. when the write() > leaves holes? Does anyone know of any programs which write non-sparse files, but not contiguously? If there are none, then this approach should be fine. In any case, the $CYGWIN approach could be a valid temporary measure until someone writes the heuristic code. Max. -- Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple Problem reports: http://cygwin.com/problems.html Documentation: http://cygwin.com/docs.html FAQ: http://cygwin.com/faq/