From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=41060 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OF5wF-0008K7-4v for qemu-devel@nongnu.org; Thu, 20 May 2010 09:37:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OF5vi-00049x-VC for qemu-devel@nongnu.org; Thu, 20 May 2010 09:37:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42941) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OF5vi-00049k-JY for qemu-devel@nongnu.org; Thu, 20 May 2010 09:36:54 -0400 Message-ID: <4BF53AEE.10207@redhat.com> Date: Thu, 20 May 2010 15:36:46 +0200 From: Jes Sorensen MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] QEMU: change default disk cache behavior References: <1274347924-9188-1-git-send-email-Jes.Sorensen@redhat.com> <4BF52B64.1020903@codemonkey.ws> In-Reply-To: <4BF52B64.1020903@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: hch@infradead.org, aliguori@us.ibm.com, qemu-devel@nongnu.org, crobinso@redhat.com On 05/20/10 14:30, Anthony Liguori wrote: > On 05/20/2010 04:32 AM, Jes.Sorensen@redhat.com wrote: >> Therefore, here is a patch that does two things: >> - default to "nocache" >> - in case of failure with nocache, retry with "write-back" >> > > This sort of change requires performance data in a variety of > circumstances to justify. > > And I strongly suspect that such a blanket change would be wrong but > that a more targeted change like making cache=none default for physical > devices would satisfy mostly everyone. Is there any other thing than physical devices attached to the -drive parameter? If so, I can take a look at making it more generic when I am back from holiday next week. Jes