From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36039) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e58tM-0006zt-UO for qemu-devel@nongnu.org; Thu, 19 Oct 2017 07:21:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e58tH-0006Aa-Vq for qemu-devel@nongnu.org; Thu, 19 Oct 2017 07:21:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51626) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e58tH-0006AG-P1 for qemu-devel@nongnu.org; Thu, 19 Oct 2017 07:21:31 -0400 Date: Thu, 19 Oct 2017 12:21:23 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20171019112122.GF2281@work-vm> References: <20171018174013.22709-1-dgilbert@redhat.com> <20171019043145.GA7850@pxdev.xzpeter.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171019043145.GA7850@pxdev.xzpeter.org> Subject: Re: [Qemu-devel] [PATCH v3 0/7] migration: pause-before-switchover List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: qemu-devel@nongnu.org, kwolf@redhat.com, jdenemar@redhat.com, wangjie88@huawei.com, quintela@redhat.com, mreitz@redhat.com, berrange@redhat.com, eblake@redhat.com, fuweiwei2@huawei.com * Peter Xu (peterx@redhat.com) wrote: > On Wed, Oct 18, 2017 at 06:40:06PM +0100, Dr. David Alan Gilbert (git) wrote: > > [...] > > > The precopy flow is: > > active->pre-switchover->device->completed > > > > The postcopy flow is: > > active->pre-switchover->postcopy-active->completed > > The naming is still slightly confusing to me: > > (1) we have a capability called "pause-before-switchover", so it feels > like there is something called "switchover" and if we enable this > we'll pause before that point; > > (2) we have a new status "pre-switchover", it feels like that's the > point before we are in "switchover" state; > > (3) we don't really have a "switchover" state, but instead it's called > "device" which is exactly the "switchover" action. > > Considering (1) and (2), I would prefer "device" state to be just > "switchover"... Yes I stuck to pause-before-device and device originally; but what we're doing during the 'device' stage is mostly saving device state; the actual switchover occurs at the end. So hmm. > Further, not sure we can unify the state transition as well (say, we > add this switchover state even without cap "pause-before-switchover" > set, although it does not make much sense itself). Then, we can also > unify the precopy/postcopy state machine into one: > > active-> > [pre-switchover->] (optional, decided by "pause-before-switchover") > switchover-> > [postcopy-active->] (optional, decided by "postcopy-arm") > completed I didn't want to change the state transition behaviour without the capability set, since that could upset an existing libvirt that would get confused by the new state. Dave > (Sorry I am discussing the naming again instead of reviewing real > stuff!) > > -- > Peter Xu -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK