On Thu, Jan 11, 2018 at 12:16:56PM +0200, Gal Hammer wrote:
> The loading time of a VM is quite significant when its virtio
> devices uses a large amount of virt-queues (e.g. a virtio-serial
> device with max_ports=511). Most of the time is spend in the
> creation of all the required event notifiers (ioeventfd and memory
> regions).
>
> This patch pack all the changes to the memory regions in a
> single memory transaction.
>
> Reported-by: Sitong Liu <si...@redhat.com>
> Reported-by: Xiaoling Gao <xia...@redhat.com>
> Signed-off-by: Gal Hammer <gham...@redhat.com>
Nice patch! Any timing numbers to share before/after?
> ---
> hw/virtio/virtio.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index ad564b0..8d8d93d 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2574,6 +2574,7 @@ static int
> virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
> VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev)));
> int n, r, err;
>
> + memory_region_transaction_begin();
> for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
> VirtQueue *vq = &vdev->vq[n];
> if (!virtio_queue_get_num(vdev, n)) {
> @@ -2596,6 +2597,7 @@ static int
> virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
> }
> event_notifier_set(&vq->host_notifier);
> }
> + memory_region_transaction_commit();
> return 0;
>
> assign_error:
> @@ -2609,6 +2611,7 @@ assign_error:
> r = virtio_bus_set_host_notifier(qbus, n, false);
> assert(r >= 0);
> }
> + memory_region_transaction_commit();
> return err;
> }
>
> @@ -2625,6 +2628,7 @@ static void
> virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev)
> VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev)));
> int n, r;
>
> + memory_region_transaction_begin();
> for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
> VirtQueue *vq = &vdev->vq[n];
>
> @@ -2632,6 +2636,13 @@ static void
> virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev)
> continue;
> }
> event_notifier_set_handler(&vq->host_notifier, NULL);
> + }
> + memory_region_transaction_commit();
> +
> + for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
> + if (!virtio_queue_get_num(vdev, n)) {
> + continue;
> + }
> r = virtio_bus_set_host_notifier(qbus, n, false);
> assert(r >= 0);
> }
> --
> 2.7.5
