On Tue, Jul 23, 2013 at 11:19 AM, yinyin <yin....@cs2c.com.cn> wrote: > during the migration, the source, not the destination, will start > dataplane again....
Thanks for explaining. The backtrace you posted is harmless. The code is written to work like this. I have annotated it explaining what is going on: virtio_blk_data_plane_start pid:29037 tid:29037 0x37cf01ecdd [/lib64/libc-2.12.so+0x1ecdd/0x393000] 0x636954 : main+0x3666/0x369a [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x630083 : main_loop+0x5d/0x82 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x5a3834 : main_loop_wait+0x92/0xc9 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x5a2e2c : qemu_iohandler_poll+0xec/0x188 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x76c755 : wait_for_connect+0x170/0x19a [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x5a3dba : tcp_wait_for_connect+0x6e/0x84 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x5a5b16 : migrate_fd_connect+0xc6/0x104 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] Live migration is start on the source. 0x7740f4 : notifier_list_notify+0x59/0x79 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] Before starting migration we notify listeners that migration is starting. 0x66a2e4 : virtio_blk_migration_state_changed+0x7c/0x12d [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x667da2 : virtio_blk_data_plane_destroy+0x33/0x70 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] Dataplane is a listener, it wants to know when migration begins. It will stop dataplane and switch to regular virtio-blk operation during live migration iterations (while RAM is being transferred but the VM is still running on the source). 0x6682a8 : virtio_blk_data_plane_stop+0x1aa/0x232 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] We are stopping dataplane right here. 0x59e98c : virtio_pci_set_host_notifier+0x73/0x8e [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x59cdf1 : virtio_pci_set_host_notifier_internal+0x132/0x157 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x6ae1bb : virtio_queue_set_host_notifier_fd_handler+0x7d/0x93 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x6ae128 : virtio_queue_host_notifier_read+0x50/0x66 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] 0x6ac6ff : virtio_queue_notify_vq+0x92/0xa8 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] As part of stopping dataplane we first flush any pending virtqueue kicks. 0x669802 : virtio_blk_handle_output+0x9c/0x118 [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] There was a pending virtqueue kick from the guest so we will complete it before stopping dataplane. 0x667ddf : virtio_blk_data_plane_start+0x0/0x31f [/root/dataplane/qemu/x86_64-softmmu/qemu-kvm] The dataplane thread was not running so it is temporarily started to process these final requests. Once they are finished it will stop again. Stefan
