From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:55267) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QbtWz-0006i3-NI for Qemu-devel@nongnu.org; Wed, 29 Jun 2011 08:06:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QbtWx-0008AZ-QE for Qemu-devel@nongnu.org; Wed, 29 Jun 2011 08:06:09 -0400 Received: from mail-yi0-f45.google.com ([209.85.218.45]:40614) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QbtWx-0008AU-GV for Qemu-devel@nongnu.org; Wed, 29 Jun 2011 08:06:07 -0400 Received: by yia25 with SMTP id 25so519706yia.4 for ; Wed, 29 Jun 2011 05:06:06 -0700 (PDT) Message-ID: <4E0B152B.1000201@codemonkey.ws> Date: Wed, 29 Jun 2011 07:06:03 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <4E0B1399.4050807@redhat.com> In-Reply-To: <4E0B1399.4050807@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Default cache mode List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: Avi Kivity , Christoph Hellwig , Qemu-devel@nongnu.org, Stefan Hajnoczi On 06/29/2011 06:59 AM, Kevin Wolf wrote: > Hi, > > I think we have touched this topic before during some IRC discussions or > somewhere deep in a mailing list thread, but I think it hasn't been > discussed on the list. > > Our default cache mode of cache=writethrough is extremely conservative > and provides absolute safety at the cost of performance, But for the most part, we track bare metal fairly well in terms of block performance, no? Or are you really referring to qcow2 as a specific example? In the past, we used a different default caching mode for qcow2. I think that could be done again if there was a compelling reason. Regards, Anthony Liguori