From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1EzfjA-0003Ff-Tv for qemu-devel@nongnu.org; Thu, 19 Jan 2006 14:45:49 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1Ezfj7-0003D5-4k for qemu-devel@nongnu.org; Thu, 19 Jan 2006 14:45:47 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Ezfj6-0003Ct-LZ for qemu-devel@nongnu.org; Thu, 19 Jan 2006 14:45:44 -0500 Received: from [64.233.162.201] (helo=zproxy.gmail.com) by monty-python.gnu.org with esmtp (Exim 4.34) id 1EzfnB-0006lW-TX for qemu-devel@nongnu.org; Thu, 19 Jan 2006 14:49:58 -0500 Received: by zproxy.gmail.com with SMTP id z3so265783nzf for ; Thu, 19 Jan 2006 11:43:11 -0800 (PST) Message-ID: <2ad73a0601191143s106b5414ob582714c59bf8fe7@mail.gmail.com> Date: Thu, 19 Jan 2006 17:43:10 -0200 From: =?ISO-8859-1?Q?Andr=E9_Braga?= Subject: Re: [Qemu-devel] Evaluating Disk IO and Snapshots In-Reply-To: <200601191504.35155.info@j-pfennig.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: <200601191504.35155.info@j-pfennig.de> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org On 1/19/06, Juergen Pfennig wrote: > What I found is that qcow has poor performance. I wrote my own driver > (which is intended only for -snapshot) and see signifcant improvements. > A 300 MByte file copy (win2003 xcopy /e between two real drives) takes > 90 instead of 135 seconds. I will send the patch to the list after it > has matured for a while. The thing is linux only for mmap() is used. Hi, While you are at it, have you considered using the LZO libraries instead of zlib for compression/decompression speed? Sure, it won't compress as much as zlib, but speed improvements should be noticeable. I was thinking about doing this myself, but no doubt you now understand the relevant source code on a level I'll still take a few weeks to. The source code for LZO is GPL'd, though. If I understand it correctly, Mr. Oberhumer wouldn't mind doing an exception for QEMU and licensing it as LGPL in this particular case; anyway, he must be contacted to clarify this issue. Link: http://www.oberhumer.com/opensource/lzo/ > The thing is linux only for mmap() is used. On the link below you'll find some practical source code showing the differences between **nix mmap() and Windows' equivalents: http://www-128.ibm.com/developerworks/eserver/library/es-MigratingWin32toLi= nux.html Please consider using those so everyone can benefit ;) Thank you! -- "I decry the current tendency to seek patents on algorithms. There are better ways to earn a living than to prevent other people from making use of one's contributions to computer science." Donald Knuth