On Tue, Aug 27, 2013 at 03:04:54PM +0800, Qin Chuanyu wrote: > On 2013/8/27 12:19, Michael S. Tsirkin wrote: > >On Tue, Aug 27, 2013 at 11:32:31AM +0800, Qin Chuanyu wrote: > >>Hi all > >> > >>I am participating in a project which try to port vhost_net on Xen。 > >> > >>By change the memory copy and notify mechanism ，currently > >>virtio-net with vhost_net could run on Xen with good > >>performance。TCP receive throughput of single vnic from 2.77Gbps up > >>to 6Gps。In VM receive side，I instead grant_copy with grant_map + > >>memcopy，it efficiently reduce the cost of grant_table spin_lock of > >>dom0，So the hole server TCP performance from 5.33Gps up to 9.5Gps。 > >> > >>Now I am consider the live migrate of vhost_net on Xen，vhost_net > >>use vhost_log for live migrate on Kvm，but qemu on Xen havn't manage > >>the hole memory of VM，So I am trying to fallback datapath from > >>vhost_net to qemu when doing live migrate ，and fallback datapath > >>from qemu to > >>vhost_net again after vm migrate to new server。 > >> > >>My question is： > >> why didn't vhost_net do the same fallback operation for live > >>migrate on KVM，but use vhost_log to mark the dirty page？ > >> Is there any mechanism fault for the idea of fallback datapath from > >>vhost_net to qemu for live migrate？ > >> > >>any question about the detail of vhost_net on Xen is welcome。 > >> > >>Thanks > >> > > > >It should work, in practice. > > > >However, one issue with this approach that I see is that you > >are running two instances of virtio-net on the host: > >qemu and vhost-net, doubling your security surface > >for guest to host attack. > > > >I don't exactly see why does it matter that qemu doesn't manage > >the whole memory of a VM - vhost only needs to log > >memory writes that it performs. > > > > > >. > > > Thanks for your reply. > > In fact，I am not sure that whether vhost_log could work on Xen live > migrate or not. Yes，vhost_sync_dirty_bitmap work well on Kvm，but > vhost_net havn't run on Xen before，although the method > vhost_dev_sync_region -> memory_region_set_dirty -> > xen_modified_memory call sequence exist. > > Have you considered the scene that vhost_migration_log code running > on Xen？ If yes，it sames much easier then fallback datapath from > vhost_net to qemu for live migrate. > I never looked at how Xen live migration works with QEMU so I don't know. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
