From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:47744) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RsCwc-0005XI-9O for qemu-devel@nongnu.org; Tue, 31 Jan 2012 07:36:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RsCwW-0006hq-I6 for qemu-devel@nongnu.org; Tue, 31 Jan 2012 07:36:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:22663) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RsCwW-0006hW-BO for qemu-devel@nongnu.org; Tue, 31 Jan 2012 07:36:12 -0500 Message-ID: <4F27E034.5060302@redhat.com> Date: Tue, 31 Jan 2012 13:36:04 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1326731457-9056-1-git-send-email-pbonzini@redhat.com> <20120118073902.GA2265@localhost.localdomain> <4F183C7A.9070603@redhat.com> <20120130093318.GA4123@localhost.localdomain> In-Reply-To: <20120130093318.GA4123@localhost.localdomain> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 00/15] SCSI s/g + SCSI migration + virtio-scsi List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hu Tao Cc: qemu-devel@nongnu.org On 01/30/2012 10:33 AM, Hu Tao wrote: >> > I cannot reproduce this with a 100G qcow2 image (created with >> > "qemu-img create scsi.qcow2 100G" just before launching the host), >> > with a partition starting at sector 2048 and extending to the end of >> > the disk. mkfs (ext4) takes less than 1 minute and extends the >> > qcow2 file to a little less than 2 gigs. > > I've re-tested today, with host kernel 2.6.35.6-45.fc14.x86_64, > 2.6.32-71.el6.x86_64, 3.1.0 and 3.3.0-rc1+, qemu version and guest > configuration remain the same, including guest kernel. It apears > that the problem appears only when the host kernel version is 3.1.0. There are two parts in the bug: 1) I/O cancellation doesn't actually cancel anything on qcow2 (and maybe others) since the coroutine transition. This makes exception handling basically unusable in the virtio-scsi guest driver. I have been working on this but I don't have patches ready for testing yet. 2) Something unknown in the kernel is causing writes to take a longer time than usual. This appears to be a problem only with 3.1.0 guest kernels. I think we can wait until (1) causes problems elsewhere. Thanks for testing! Paolo