From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53335) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bQVRs-0003Tb-96 for qemu-devel@nongnu.org; Fri, 22 Jul 2016 04:04:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bQVRn-0007IQ-Hu for qemu-devel@nongnu.org; Fri, 22 Jul 2016 04:04:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60037) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bQVRn-0007IM-Bw for qemu-devel@nongnu.org; Fri, 22 Jul 2016 04:04:39 -0400 Date: Fri, 22 Jul 2016 09:04:34 +0100 From: "Daniel P. Berrange" Message-ID: <20160722080433.GB20567@redhat.com> Reply-To: "Daniel P. Berrange" References: <1469077560-20620-1-git-send-email-zhang.zhanghailiang@huawei.com> <20160721121914.GG13528@redhat.com> <20160721174122.GM2195@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160721174122.GM2195@work-vm> Subject: Re: [Qemu-devel] [RFC PATCH 0/2] Migration: support working on file:url List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: zhanghailiang , qemu-devel@nongnu.org, amit.shah@redhat.com, peter.huangpeng@huawei.com, quintela@redhat.com On Thu, Jul 21, 2016 at 06:41:23PM +0100, Dr. David Alan Gilbert wrote: > * Daniel P. Berrange (berrange@redhat.com) wrote: > > On Thu, Jul 21, 2016 at 01:05:58PM +0800, zhanghailiang wrote: > > > It is more simple to use file:url to migrate VM into file. > > > Besides, it will be used in memory snapshot. > > > > NB, you can already migrate into a file > > > > "exec:/bin/cat > /path/to/file" > > > > and likewise > > > > qemu -incoming "exec:/bin/cat /path/to/file" > > > > This avoids the problem with POSIX I/O on plain files not actually > > supporting O_NONBLOCK in any sensible manner, which your file: > > suggestion suffers from. > > Hmm that's a shame; I liked this idea as a nice simplification of the > exec: stuff. The only way to achieve that would be to spawn a thread in QEMU that does I/O to the actual file, and then have the migration code do I/O to/from that thread via a pipe. IOW, the thread would take the role of cat. What that's worth doing or not I don't know, given that it is already possible to use exec+cat. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|